Final California 2026 Integrated Report (303(d) List/305(b) Report)
Supporting Information
Regional Board 2 - San Francisco Bay Region
Water Body Name:
Arroyo Las Positas
Water Body ID:
CAR2043008020010905115005
Water Body Type:
River & Stream
DECISION ID
151285
Region 2
Arroyo Las Positas
Pollutant:
Eutrophication
Final Listing Decision:
Do Not Delist from 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:
List on 303(d) list (TMDL required list)(2018)
Revision Status
Revised
Sources:
A Source Unknown
TMDL Priority:
Low
Impairment from Pollutant or Pollution:
Pollutant
Regional Board Conclusion:
This pollutant is being considered for listing under sections 3.2 and 3.11 of the Listing Policy. Under section 3.11, water segments shall be evaluated to determine whether the weight of evidence demonstrates that a water quality standard is not attained. Four lines of evidence are available in the administrative record to assess this pollutant: (1) low dissolved oxygen measurements from continuous dissolved oxygen records, (2) supersaturated dissolved oxygen measurements from continuous dissolved oxygen records, (3) measurements of nitrate as N concentrations in water, and (4) samples of benthic macroinvertebrate assemblages. Based on the readily available data for this water body, the weight of evidence indicates that there is sufficient justification available in favor of adding this water segment-pollutant combination to the section 303(d) list in the Water Quality Limited Segments category. This conclusion is based on the staff findings that: 1. The data concerning current conditions and supporting the listing decision satisfy the data quality requirements of section 6.1.4 of the Policy. 2. The data used satisfy the data quantity requirements of section 6.1.5 of the Policy. 3. Minimum dissolved oxygen measurements were below the warm-water water quality objective of 5 mg/L in 4 out of 9 sampling events. Using table 3.2 of the listing policy, a minimum of 5 exceedances are needed to list this water body on the 303(d) list with a minimum sample size of 5. However, additional water quality information indicates that this water body is impaired by low dissolved oxygen levels as a result of widespread eutrophic conditions. Under section 3.11, these additional factors shall be considered in a weight of evidence approach in the decision to list a water body as impaired. 4. Supersaturated dissolved oxygen levels greater than 200% were observed in 5 out of 9 deployments, including a maximum value of 395%, indicating tremendous oxygen production by algae (eutrophication). 5. Eight out of 8 nitrate samples had concentrations greater than the guideline of 0.5 mg/L to prevent nuisance algae growth. Additionally, 8 out of 8 nitrate samples had concentrations greater than the guideline of 2.0 mg/L to protect aquatic life from nitrate toxicity. These high nitrate concentrations can promote the growth of periphyton that can cause nuisance and adversely affect beneficial uses. 6. Twelve out of 13 samples exceeded the recommended pH level of 8.5. The measured exceedances ranged from 8.52 to 8.99 with one maximum pH of 9.24. 7. Benthic macroinvertebrate (BMI) assemblages were significantly altered relative to reference conditions, indicating that controllable water quality factors have resulted in significant alterations in the community ecology of receiving waters. These alterations are most likely the result of low levels of dissolved oxygen, which is a result of eutrophication. Of the 6 sites where BMI were sampled, dissolved oxygen was also measured at 4 sites. Three of these sites had dissolved oxygen levels <5 mg/L. 8. Pursuant to section 3.11 of the Listing Policy, no additional data and information are available indicating that standards are not met.
Regional Board Decision Recommendation:
This is a decision previously approved by the State Water Resources Control Board and the USEPA. No new data were assessed by the Regional Board for the current. The decision has not changed.
State Board Review of Regional Board Conclusion and Recommendation:
State Board Decision Recommendation:
After review of this Regional Board decision, SWRCB staff recommend the decision be approved by the State Board.
Listing Extent:
This TMDL completion date was updated to 2037
Line of Evidence (LOE) for Decision ID 151285, Eutrophication
Region 2
Arroyo Las Positas
LOE ID:
4810
Pollutant:
Low Dissolved Oxygen
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
None
Beneficial Use:
Warm Freshwater Habitat
Aquatic Life Use:
Wildlife Habitat
Number of Samples:
9
Number of Exceedances:
4
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Data used to evaluate dissolved oxygen were collected by SWAMP in 2002. In 4 out of 9 deployments, minimum dissolved oxygen levels fell below the objective of 5 mg/L. Minimum values were nearly anoxic (0.56 mg/L) at one site in the summer season. Low dissolved oxygen concentrations generally occurred during the night and early morning hours.
Continuous depressed levels of dissolved oxygen (< 5.0 mg/L) lasted from over 5 hours (dry season, downstream location) to 12 hours and 45 minutes (dry season, Altamont Creek upstream of confluence with Arroyo Las Positas).
Dissolved oxygen levels fell below 5 mg/L during one additional deployment in the upstream section of Arroyo Las Positas. The longest duration of suppressed oxygen levels lasted for over 12 hours and the patterns of dissolved oxygen concentrations at this location followed closely that of Altamont Creek. Although these measurements support the listing decision and indicate that dissolved oxygen levels are the cause of the impairment, they cannot be used directly because of the marginal (by +/- 0.4%) exceedance of the quality assurance requirements.
The numeric water quality objective for dissolved oxygen is 5.0 mg/L minimum for waters designated as warm freshwater habitat. The median dissolved oxygen concentration for any three consecutive months shall not be less than 80 percent of the dissolved oxygen content at saturation.
Dissolved oxygen was measured at five sites. Three of these sites were located on the mainstem of Arroyo Las Positas, while one site each was located on Altamont Creek and Arroyo Seco, two major tributaries. The lowest dissolved oxygen levels were measured at site ALP105 on Altamont Creek. Low dissolved oxygen levels also occurred in the mainstem of Arroyo Las Positas during the summer season.
Temporal Representation:
The SWAMP Program performed continuous monitoring of dissolved oxygen at 15 minute intervals for periods of 1-2 weeks in each of three different seasons: winter (March 2002; 3 sites, 1 site meeting quality assurance requirements), spring (April 2002; 5 sites, 4 sites meeting quality assurance requirements), and summer (late June and late July 2002; 5 sites, 4 sites meeting quality assurance requirements).
Environmental Conditions:
Arroyo Las Positas flows west through the eastern Livermore valley before its confluence with Arroyo Mocho in eastern Pleasanton. The lower and middle sections of Arroyo Las Positas and Altamont Creek flow through the northern portion of the city of Livermore, a city of 82,000 people. The upper watershed is primarily used for cattle grazing. The lowest and highest dissolved oxygen levels were measured in a section of Altamont Creek that contained very high amounts of benthic algae and was located downstream of a golf course and small eutrophic pond. The main stem of Arroyo Las Positas is almost completely devoid of riparian vegetation as a result of extensive channel alteration and incision.
QAPP Information:
All samples were collected and analyzed using procedures comparable with the SWAMP Quality Assurance Management Plan (SWRCB 2002).
Final California 2026 Integrated Report (303(d) List/305(b) Report)
Supporting Information
Regional Board 2 - San Francisco Bay Region
Water Body Name:
Arroyo Las Positas
Water Body ID:
CAR2043008020010905115005
Water Body Type:
River & Stream
DECISION ID
151285
Region 2
Arroyo Las Positas
Pollutant:
Eutrophication
Final Listing Decision:
Do Not Delist from 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:
List on 303(d) list (TMDL required list)(2018)
Revision Status
Revised
Sources:
A Source Unknown
TMDL Priority:
Low
Impairment from Pollutant or Pollution:
Pollutant
Regional Board Conclusion:
This pollutant is being considered for listing under sections 3.2 and 3.11 of the Listing Policy. Under section 3.11, water segments shall be evaluated to determine whether the weight of evidence demonstrates that a water quality standard is not attained. Four lines of evidence are available in the administrative record to assess this pollutant: (1) low dissolved oxygen measurements from continuous dissolved oxygen records, (2) supersaturated dissolved oxygen measurements from continuous dissolved oxygen records, (3) measurements of nitrate as N concentrations in water, and (4) samples of benthic macroinvertebrate assemblages. Based on the readily available data for this water body, the weight of evidence indicates that there is sufficient justification available in favor of adding this water segment-pollutant combination to the section 303(d) list in the Water Quality Limited Segments category. This conclusion is based on the staff findings that: 1. The data concerning current conditions and supporting the listing decision satisfy the data quality requirements of section 6.1.4 of the Policy. 2. The data used satisfy the data quantity requirements of section 6.1.5 of the Policy. 3. Minimum dissolved oxygen measurements were below the warm-water water quality objective of 5 mg/L in 4 out of 9 sampling events. Using table 3.2 of the listing policy, a minimum of 5 exceedances are needed to list this water body on the 303(d) list with a minimum sample size of 5. However, additional water quality information indicates that this water body is impaired by low dissolved oxygen levels as a result of widespread eutrophic conditions. Under section 3.11, these additional factors shall be considered in a weight of evidence approach in the decision to list a water body as impaired. 4. Supersaturated dissolved oxygen levels greater than 200% were observed in 5 out of 9 deployments, including a maximum value of 395%, indicating tremendous oxygen production by algae (eutrophication). 5. Eight out of 8 nitrate samples had concentrations greater than the guideline of 0.5 mg/L to prevent nuisance algae growth. Additionally, 8 out of 8 nitrate samples had concentrations greater than the guideline of 2.0 mg/L to protect aquatic life from nitrate toxicity. These high nitrate concentrations can promote the growth of periphyton that can cause nuisance and adversely affect beneficial uses. 6. Twelve out of 13 samples exceeded the recommended pH level of 8.5. The measured exceedances ranged from 8.52 to 8.99 with one maximum pH of 9.24. 7. Benthic macroinvertebrate (BMI) assemblages were significantly altered relative to reference conditions, indicating that controllable water quality factors have resulted in significant alterations in the community ecology of receiving waters. These alterations are most likely the result of low levels of dissolved oxygen, which is a result of eutrophication. Of the 6 sites where BMI were sampled, dissolved oxygen was also measured at 4 sites. Three of these sites had dissolved oxygen levels <5 mg/L. 8. Pursuant to section 3.11 of the Listing Policy, no additional data and information are available indicating that standards are not met.
Regional Board Decision Recommendation:
This is a decision previously approved by the State Water Resources Control Board and the USEPA. No new data were assessed by the Regional Board for the current. The decision has not changed.
State Board Review of Regional Board Conclusion and Recommendation:
State Board Decision Recommendation:
After review of this Regional Board decision, SWRCB staff recommend the decision be approved by the State Board.
Listing Extent:
This TMDL completion date was updated to 2037
Line of Evidence (LOE) for Decision ID 151285, Eutrophication
Region 2
Arroyo Las Positas
LOE ID:
4810
Pollutant:
Low Dissolved Oxygen
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
None
Beneficial Use:
Warm Freshwater Habitat
Aquatic Life Use:
Wildlife Habitat
Number of Samples:
9
Number of Exceedances:
4
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Data used to evaluate dissolved oxygen were collected by SWAMP in 2002. In 4 out of 9 deployments, minimum dissolved oxygen levels fell below the objective of 5 mg/L. Minimum values were nearly anoxic (0.56 mg/L) at one site in the summer season. Low dissolved oxygen concentrations generally occurred during the night and early morning hours.
Continuous depressed levels of dissolved oxygen (< 5.0 mg/L) lasted from over 5 hours (dry season, downstream location) to 12 hours and 45 minutes (dry season, Altamont Creek upstream of confluence with Arroyo Las Positas).
Dissolved oxygen levels fell below 5 mg/L during one additional deployment in the upstream section of Arroyo Las Positas. The longest duration of suppressed oxygen levels lasted for over 12 hours and the patterns of dissolved oxygen concentrations at this location followed closely that of Altamont Creek. Although these measurements support the listing decision and indicate that dissolved oxygen levels are the cause of the impairment, they cannot be used directly because of the marginal (by +/- 0.4%) exceedance of the quality assurance requirements.
The numeric water quality objective for dissolved oxygen is 5.0 mg/L minimum for waters designated as warm freshwater habitat. The median dissolved oxygen concentration for any three consecutive months shall not be less than 80 percent of the dissolved oxygen content at saturation.
Dissolved oxygen was measured at five sites. Three of these sites were located on the mainstem of Arroyo Las Positas, while one site each was located on Altamont Creek and Arroyo Seco, two major tributaries. The lowest dissolved oxygen levels were measured at site ALP105 on Altamont Creek. Low dissolved oxygen levels also occurred in the mainstem of Arroyo Las Positas during the summer season.
Temporal Representation:
The SWAMP Program performed continuous monitoring of dissolved oxygen at 15 minute intervals for periods of 1-2 weeks in each of three different seasons: winter (March 2002; 3 sites, 1 site meeting quality assurance requirements), spring (April 2002; 5 sites, 4 sites meeting quality assurance requirements), and summer (late June and late July 2002; 5 sites, 4 sites meeting quality assurance requirements).
Environmental Conditions:
Arroyo Las Positas flows west through the eastern Livermore valley before its confluence with Arroyo Mocho in eastern Pleasanton. The lower and middle sections of Arroyo Las Positas and Altamont Creek flow through the northern portion of the city of Livermore, a city of 82,000 people. The upper watershed is primarily used for cattle grazing. The lowest and highest dissolved oxygen levels were measured in a section of Altamont Creek that contained very high amounts of benthic algae and was located downstream of a golf course and small eutrophic pond. The main stem of Arroyo Las Positas is almost completely devoid of riparian vegetation as a result of extensive channel alteration and incision.
QAPP Information:
All samples were collected and analyzed using procedures comparable with the SWAMP Quality Assurance Management Plan (SWRCB 2002).
Line of Evidence (LOE) for Decision ID 151285, Eutrophication
Region 2
Arroyo Las Positas
LOE ID:
4812
Pollutant:
Nitrate
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Dissolved
Beneficial Use:
Warm Freshwater Habitat
Aquatic Life Use:
Wildlife Habitat
Number of Samples:
8
Number of Exceedances:
8
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Eight out of 8 nitrate samples had concentrations greater than 0.5 mg/L. Eight out of 8 nitrate samples also had concentrations greater than 2.0 mg/L. The highest concentrations (8.04 mg/L and 6.52 mg/L) occurred at the same site (ALP110; Arroyo Las Positas, just upstream of Altamont Creek) in January and April 2002, and were among the highest nitrate concentrations measured by SWAMP in the SF Bay Region.
Waters shall not contain biostimulatory substances in concentrations that promote aquatic growths to the extent that such growths cause nuisance or adversely affect beneficial uses
All waters shall be maintained free of toxic substances in concentrations that are lethal to or that produce significant alterations in population or community ecology or receiving water biota.
1. Total nitrogen levels greater than 0.5 mg/L can result in large masses of nuisance algae unless other factors limit algae growth (Bowie et al. 1985; Biggs 2000). Since nitrate is one component of total nitrogen in water, nitrate levels should also be less than 0.5 mg/L.
2. Nitrate (NO3-N) concentrations above 2.0 mg/L can cause toxicity in a variety of freshwater organisms (Camargo et al. 2005).
Nitrate was sampled at four sites in the watershed, including two main stem sites and two sites on Altamont Creek, an important tributary.
Temporal Representation:
Water samples were collected for nitrate analyses during three sampling events. The same four sites were sampled during each sampling event. Data are evaluated from the January 2002 and April 2002 sampling events only. Laboratory methods used on samples collected during September 2001 did not meet quality assurance requirements, so this data has not been considered.
Environmental Conditions:
Arroyo Las Positas flows west through the eastern Livermore valley before its confluence with Arroyo Mocho in eastern Pleasanton. The lower and middle sections of Arroyo Las Positas and Altamont Creek flow through the northern portion of the city of Livermore, a city of 82,000 people. The upper watershed is primarily used for cattle grazing. The main stem of Arroyo Las Positas is almost completely devoid of riparian vegetation as a result of extensive channel alteration and incision.
QAPP Information:
All samples were collected and analyzed using procedures comparable with the SWAMP Quality Assurance Management Plan (SWRCB 2002).
Eight out of 8 nitrate samples had concentrations greater than 0.5 mg/L. Eight out of 8 nitrate samples also had concentrations greater than 2.0 mg/L. The highest concentrations (8.04 mg/L and 6.52 mg/L) occurred at the same site (ALP110; Arroyo Las Positas, just upstream of Altamont Creek) in January and April 2002, and were among the highest nitrate concentrations measured by SWAMP in the SF Bay Region.
Waters shall not contain biostimulatory substances in concentrations that promote aquatic growths to the extent that such growths cause nuisance or adversely affect beneficial uses
All waters shall be maintained free of toxic substances in concentrations that are lethal to or that produce significant alterations in population or community ecology or receiving water biota.
1. Total nitrogen levels greater than 0.5 mg/L can result in large masses of nuisance algae unless other factors limit algae growth (Bowie et al. 1985; Biggs 2000). Since nitrate is one component of total nitrogen in water, nitrate levels should also be less than 0.5 mg/L.
2. Nitrate (NO3-N) concentrations above 2.0 mg/L can cause toxicity in a variety of freshwater organisms (Camargo et al. 2005).
Nitrate was sampled at four sites in the watershed, including two main stem sites and two sites on Altamont Creek, an important tributary.
Temporal Representation:
Water samples were collected for nitrate analyses during three sampling events. The same four sites were sampled during each sampling event. Data are evaluated from the January 2002 and April 2002 sampling events only. Laboratory methods used on samples collected during September 2001 did not meet quality assurance requirements, so this data has not been considered.
Environmental Conditions:
Arroyo Las Positas flows west through the eastern Livermore valley before its confluence with Arroyo Mocho in eastern Pleasanton. The lower and middle sections of Arroyo Las Positas and Altamont Creek flow through the northern portion of the city of Livermore, a city of 82,000 people. The upper watershed is primarily used for cattle grazing. The main stem of Arroyo Las Positas is almost completely devoid of riparian vegetation as a result of extensive channel alteration and incision.
QAPP Information:
All samples were collected and analyzed using procedures comparable with the SWAMP Quality Assurance Management Plan (SWRCB 2002).
Line of Evidence (LOE) for Decision ID 151285, Eutrophication
Region 2
Arroyo Las Positas
LOE ID:
28987
Pollutant:
pH
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
None
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
13
Number of Exceedances:
12
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water quality assessment was conducted at the Arroyo Las Positas Creek watershed as part of SWAMP study in 2001-2002. Continuous field monitoring at 15 minute increments of temperature, dissolved oxygen, pH and specific conductance was conducted to determine temporal variability in basic water quality at three locations. Continuous monitoring sondes were deployed 13 times at 3 or 5 monitoring locations during wet, spring and dry seasons. The pH ranged from 7.58 to 8.99. The upper level of 8.5 was exceeded in 12 of the 13 sampling location over the three seasons.
The pH shall not be depressed below 6.5 nor raised above 8.5. This encompasses the pH range usually found in waters within the basin. Controllable water quality factors shall not cause changes greater than 0.5 units in normal ambient pH levels.
Comprehensive water quality assessment was conducted at Arroyo Las Positas Creek watershed as part of SWAMP assessment in 2002. Continuous field monitoring of temperature, dissolved oxygen, pH, and specific conductance to determine temporal variability in basic water quality at three or five locations, throughout Arroyo Las Positas Creek watershed. The pH ranged from 7.58 to 8.99 and varied with season.
pH was measured at three to five sites located on the mainstream of Arroyo Las Positas Creek that are representative of the entire creek length.
Temporal Representation:
In 2002 the SWAMP Program performed continuous monitoring of pH at 15 minute intervals for periods of 1-2 weeks in each of three different seasons: winter (3 sites), spring (5 sites), and summer dry season (5 sites).
Environmental Conditions:
QAPP Information:
All samples were collected and analyzed using procedures comparable with the SWAMP Quality Assurance Management Plan (SWRCB, 2002).
Line of Evidence (LOE) for Decision ID 151285, Eutrophication
Region 2
Arroyo Las Positas
LOE ID:
4813
Pollutant:
Benthic-Macroinvertebrate Bioassessments
LOE Subgroup:
Line of Evidence (LOE) for Decision ID 151285, Eutrophication
Region 2
Arroyo Las Positas
LOE ID:
28987
Pollutant:
pH
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
None
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
13
Number of Exceedances:
12
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water quality assessment was conducted at the Arroyo Las Positas Creek watershed as part of SWAMP study in 2001-2002. Continuous field monitoring at 15 minute increments of temperature, dissolved oxygen, pH and specific conductance was conducted to determine temporal variability in basic water quality at three locations. Continuous monitoring sondes were deployed 13 times at 3 or 5 monitoring locations during wet, spring and dry seasons. The pH ranged from 7.58 to 8.99. The upper level of 8.5 was exceeded in 12 of the 13 sampling location over the three seasons.
The pH shall not be depressed below 6.5 nor raised above 8.5. This encompasses the pH range usually found in waters within the basin. Controllable water quality factors shall not cause changes greater than 0.5 units in normal ambient pH levels.
Comprehensive water quality assessment was conducted at Arroyo Las Positas Creek watershed as part of SWAMP assessment in 2002. Continuous field monitoring of temperature, dissolved oxygen, pH, and specific conductance to determine temporal variability in basic water quality at three or five locations, throughout Arroyo Las Positas Creek watershed. The pH ranged from 7.58 to 8.99 and varied with season.
pH was measured at three to five sites located on the mainstream of Arroyo Las Positas Creek that are representative of the entire creek length.
Temporal Representation:
In 2002 the SWAMP Program performed continuous monitoring of pH at 15 minute intervals for periods of 1-2 weeks in each of three different seasons: winter (3 sites), spring (5 sites), and summer dry season (5 sites).
Environmental Conditions:
QAPP Information:
All samples were collected and analyzed using procedures comparable with the SWAMP Quality Assurance Management Plan (SWRCB, 2002).
Line of Evidence (LOE) for Decision ID 151285, Eutrophication
Region 2
Arroyo Las Positas
LOE ID:
4813
Pollutant:
Benthic-Macroinvertebrate Bioassessments
LOE Subgroup:
Population/Community Degradation
Matrix:
-N/A
Fraction:
None
Beneficial Use:
Warm Freshwater Habitat
Aquatic Life Use:
Wildlife Habitat
Number of Samples:
7
Number of Exceedances:
7
Data and Information Type:
Benthic macroinvertebrate surveys
Data Used to Assess Water Quality:
Benthic macroinvertebrates were sampled from 7 sites in the Arroyo Las Positas watershed in April 2001 by the SWAMP program. Benthic macroinvertebrate assemblage metrics were well outside the range of scores for minimally disturbed reference sites. Taxa richness scores at all 7 sampled sites in the Arroyo Las Positas watershed ranged from 11 to 16 taxa, whereas taxa richness values at reference sites ranged from 28 to 59. No taxa that are sensitive to pollution were present in any of the samples, indicating that pollution has resulted in significant alterations of community ecology.
All waters shall be maintained free of toxic substances in concentrations that are lethal to or that produce significant alterations in population or community ecology or receiving water biota. In addition, the health and life history characteristics of aquatic organisms in waters affected by controllable water quality factors shall not differ significantly from those for the same waters in areas unaffected by controllable water quality factors.
Benthic macroinvertebrate assemblage metric scores that are outside the range of scores for minimally disturbed reference sites indicate significant alterations in community ecology. Taxa richness values at reference sites sampled by the SWAMP program between 2001 and 2003 ranged from 28 to 59.
Benthic macroinvertebrates were sampled from 7 sites throughout the watershed. Five sites were sampled on the main stem of Arroyo Las Positas, and 2 sites were sampled on Altamont Creek, the major perennial tributary of Arroyo Las Positas.
Temporal Representation:
Benthic macroinvertebrates were sampled once in April, 2001.
Environmental Conditions:
Arroyo Las Positas flows west through the eastern Livermore valley before its confluence with Arroyo Mocho in eastern Pleasanton. The lower and middle sections of Arroyo Las Positas and Altamont Creek flow through the northern portion of the city of Livermore, a city of 82,000 people. The upper watershed is primarily used for cattle grazing. The main stem of Arroyo Las Positas is almost completely devoid of riparian vegetation as a result of extensive channel alteration and incision.
QAPP Information:
All samples were collected and analyzed using procedures comparable with the SWAMP Quality Assurance Management Plan (SWRCB 2002).
Line of Evidence (LOE) for Decision ID 151285, Eutrophication
Region 2
Arroyo Las Positas
LOE ID:
4811
Pollutant:
Dissolved oxygen saturation
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
None
Beneficial Use:
Warm Freshwater Habitat
Aquatic Life Use:
Wildlife Habitat
Number of Samples:
9
Number of Exceedances:
5
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Data used to evaluate dissolved oxygen was collected by SWAMP. Supersaturated dissolved oxygen levels greater than 200% were observed in 5 out of 9 deployments, including a maximum value of 395%, indicating tremendous oxygen production by algae (eutrophication). Supersatured conditions always occurred during the daylight hours. The maximum diurnal range in dissolved oxygen was greater than 30 mg/L, higher than any values ever reported in the literature (Kent et al. 2005).
All waters shall be maintained free of toxic substances in concentrations that are lethal to or that produce significant alterations in population or community ecology or receiving water biota.
Dissolved oxygen supersaturation above 200 percent results in mortality of fish due to gill and skin lesions from gas bubble disease (Woodbury 1942, Renfro 1963, Weitkamp and Katz 1980).
Dissolved oxygen was measured at five sites. Three of these sites were located on the mainstem of Arroyo Las Positas, while one site each was located on the major tributary. The highest dissolved oxygen levels were measured at site ALP105 on Altamont Creek, a major tributary to Arroyo Las Positas.
Temporal Representation:
The SWAMP Program performed continuous monitoring of dissolved oxygen at 15 minute intervals for periods of 1-2 weeks in each of three different seasons: winter (March 2002; 3 sites, 1 site meeting quality assurance requirements), spring (April 2002; 5 sites, 4 sites meeting quality assurance requirements), and summer (late June and late July 2002; 5 sites, 4 sites meeting quality assurance requirements).
Environmental Conditions:
Arroyo Las Positas flows west through the eastern Livermore valley before its confluence with Arroyo Mocho in eastern Pleasanton. The lower and middle sections of Arroyo Las Positas and Altamont Creek flow through the northern portion of the city of Livermore, a city of 82,000 people. The upper watershed is primarily used for cattle grazing. The lowest and highest dissolved oxygen levels were measured in a section of Altamont Creek that contained very high amounts of benthic algae and was located downstream of a golf course and small eutrophic pond. The main stem of Arroyo Las Positas is almost completely devoid of riparian vegetation as a result of extensive channel alteration and incision.
QAPP Information:
All samples were collected and analyzed using procedures comparable with the SWAMP Quality Assurance Management Plan (SWRCB 2002).
Benthic macroinvertebrates were sampled from 7 sites in the Arroyo Las Positas watershed in April 2001 by the SWAMP program. Benthic macroinvertebrate assemblage metrics were well outside the range of scores for minimally disturbed reference sites. Taxa richness scores at all 7 sampled sites in the Arroyo Las Positas watershed ranged from 11 to 16 taxa, whereas taxa richness values at reference sites ranged from 28 to 59. No taxa that are sensitive to pollution were present in any of the samples, indicating that pollution has resulted in significant alterations of community ecology.
All waters shall be maintained free of toxic substances in concentrations that are lethal to or that produce significant alterations in population or community ecology or receiving water biota. In addition, the health and life history characteristics of aquatic organisms in waters affected by controllable water quality factors shall not differ significantly from those for the same waters in areas unaffected by controllable water quality factors.
Benthic macroinvertebrate assemblage metric scores that are outside the range of scores for minimally disturbed reference sites indicate significant alterations in community ecology. Taxa richness values at reference sites sampled by the SWAMP program between 2001 and 2003 ranged from 28 to 59.
Benthic macroinvertebrates were sampled from 7 sites throughout the watershed. Five sites were sampled on the main stem of Arroyo Las Positas, and 2 sites were sampled on Altamont Creek, the major perennial tributary of Arroyo Las Positas.
Temporal Representation:
Benthic macroinvertebrates were sampled once in April, 2001.
Environmental Conditions:
Arroyo Las Positas flows west through the eastern Livermore valley before its confluence with Arroyo Mocho in eastern Pleasanton. The lower and middle sections of Arroyo Las Positas and Altamont Creek flow through the northern portion of the city of Livermore, a city of 82,000 people. The upper watershed is primarily used for cattle grazing. The main stem of Arroyo Las Positas is almost completely devoid of riparian vegetation as a result of extensive channel alteration and incision.
QAPP Information:
All samples were collected and analyzed using procedures comparable with the SWAMP Quality Assurance Management Plan (SWRCB 2002).
Line of Evidence (LOE) for Decision ID 151285, Eutrophication
Region 2
Arroyo Las Positas
LOE ID:
4811
Pollutant:
Dissolved oxygen saturation
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
None
Beneficial Use:
Warm Freshwater Habitat
Aquatic Life Use:
Wildlife Habitat
Number of Samples:
9
Number of Exceedances:
5
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Data used to evaluate dissolved oxygen was collected by SWAMP. Supersaturated dissolved oxygen levels greater than 200% were observed in 5 out of 9 deployments, including a maximum value of 395%, indicating tremendous oxygen production by algae (eutrophication). Supersatured conditions always occurred during the daylight hours. The maximum diurnal range in dissolved oxygen was greater than 30 mg/L, higher than any values ever reported in the literature (Kent et al. 2005).
All waters shall be maintained free of toxic substances in concentrations that are lethal to or that produce significant alterations in population or community ecology or receiving water biota.
Dissolved oxygen supersaturation above 200 percent results in mortality of fish due to gill and skin lesions from gas bubble disease (Woodbury 1942, Renfro 1963, Weitkamp and Katz 1980).
Dissolved oxygen was measured at five sites. Three of these sites were located on the mainstem of Arroyo Las Positas, while one site each was located on the major tributary. The highest dissolved oxygen levels were measured at site ALP105 on Altamont Creek, a major tributary to Arroyo Las Positas.
Temporal Representation:
The SWAMP Program performed continuous monitoring of dissolved oxygen at 15 minute intervals for periods of 1-2 weeks in each of three different seasons: winter (March 2002; 3 sites, 1 site meeting quality assurance requirements), spring (April 2002; 5 sites, 4 sites meeting quality assurance requirements), and summer (late June and late July 2002; 5 sites, 4 sites meeting quality assurance requirements).
Environmental Conditions:
Arroyo Las Positas flows west through the eastern Livermore valley before its confluence with Arroyo Mocho in eastern Pleasanton. The lower and middle sections of Arroyo Las Positas and Altamont Creek flow through the northern portion of the city of Livermore, a city of 82,000 people. The upper watershed is primarily used for cattle grazing. The lowest and highest dissolved oxygen levels were measured in a section of Altamont Creek that contained very high amounts of benthic algae and was located downstream of a golf course and small eutrophic pond. The main stem of Arroyo Las Positas is almost completely devoid of riparian vegetation as a result of extensive channel alteration and incision.
QAPP Information:
All samples were collected and analyzed using procedures comparable with the SWAMP Quality Assurance Management Plan (SWRCB 2002).
Do Not Delist from 303(d) list (being addressed with USEPA approved TMDL)
Last Listing Cycle's Final Listing Decision:
List on 303(d) list (being addressed by USEPA approved TMDL)(2018)
Revision Status
Revised
Sources:
Urban Runoff/Storm Sewers
TMDL Name:
San Francisco Bay Urban Creeks Diazinon
TMDL Project Code:
9
Date TMDL Approved by USEPA:
05/16/2007
Impairment from Pollutant or Pollution:
Pollutant
Regional Board Conclusion:
303(d) listing decisions made prior to 2006 were not held in an assessment database. The Regional Boards will update this decision when new data and information become available and are assessed. The USEPA final decision on the 2006 303(d) list was to move this listing to the being addressed by a USEPA approved TMDL portion of the 303(d) list, because the San Francisco Bay Urban Creeks Diazinon TMDL was approved by USEPA on 5/21/07 (USEPA, 2007).
Regional Board Decision Recommendation:
This is a decision previously approved by the State Water Resources Control Board and the USEPA. No new data were assessed by the Regional Board for the current. The decision has not changed.
State Board Review of Regional Board Conclusion and Recommendation:
State Board Decision Recommendation:
After review of this Regional Board decision, SWRCB staff recommend the decision be approved by the State Board.
Listing Extent:
For 2006, diazinon was moved by USEPA from the 303(d) list to this being addressed list because of a completed USEPA approved TMDL.
Line of Evidence (LOE) for Decision ID 141706, Diazinon
Region 2
Arroyo Las Positas
LOE ID:
1797
Pollutant:
Diazinon
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
None
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
0
Number of Exceedances:
0
Data and Information Type:
Not Specified
Data Used to Assess Water Quality:
Unspecified---This LOE is a placeholder to support a 303(d) listing decision made prior to 2006.
Line of Evidence (LOE) for Decision ID 141706, Diazinon
Region 2
Arroyo Las Positas
LOE ID:
290173
Pollutant:
Diazinon
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
None
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
The Arroyo Las Positas Creek watershed was monitored as part of SWAMP assessment. Neither sample exceeded the water quality objectives for Chlorpyrifos, Dacthal, diazinon, disulfoton, endosulfan, Lindane/gamma Hexachlorocyclohexane (gamma-HCH), methyl parathion, thiobencarb.
All waters shall be maintained free of toxic substances that are lethal to or that produce other detrimental responses in aquatic organisms. There shall be no chronic toxicity in ambient waters. Chronic toxicity is a detrimental biological effect on growth rate, reproduction, fertilization success, larval development, population abundance, community composition, or any other relevant measure of the health of an organism, population, or community.Diazinon water quality objective, 0.1 ug/L (acute)
Do Not Delist from 303(d) list (being addressed with USEPA approved TMDL)
Last Listing Cycle's Final Listing Decision:
List on 303(d) list (being addressed by USEPA approved TMDL)(2018)
Revision Status
Revised
Sources:
Urban Runoff/Storm Sewers
TMDL Name:
San Francisco Bay Urban Creeks Diazinon
TMDL Project Code:
9
Date TMDL Approved by USEPA:
05/16/2007
Impairment from Pollutant or Pollution:
Pollutant
Regional Board Conclusion:
303(d) listing decisions made prior to 2006 were not held in an assessment database. The Regional Boards will update this decision when new data and information become available and are assessed. The USEPA final decision on the 2006 303(d) list was to move this listing to the being addressed by a USEPA approved TMDL portion of the 303(d) list, because the San Francisco Bay Urban Creeks Diazinon TMDL was approved by USEPA on 5/21/07 (USEPA, 2007).
Regional Board Decision Recommendation:
This is a decision previously approved by the State Water Resources Control Board and the USEPA. No new data were assessed by the Regional Board for the current. The decision has not changed.
State Board Review of Regional Board Conclusion and Recommendation:
State Board Decision Recommendation:
After review of this Regional Board decision, SWRCB staff recommend the decision be approved by the State Board.
Listing Extent:
For 2006, diazinon was moved by USEPA from the 303(d) list to this being addressed list because of a completed USEPA approved TMDL.
Line of Evidence (LOE) for Decision ID 141706, Diazinon
Region 2
Arroyo Las Positas
LOE ID:
1797
Pollutant:
Diazinon
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
None
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
0
Number of Exceedances:
0
Data and Information Type:
Not Specified
Data Used to Assess Water Quality:
Unspecified---This LOE is a placeholder to support a 303(d) listing decision made prior to 2006.
Line of Evidence (LOE) for Decision ID 141706, Diazinon
Region 2
Arroyo Las Positas
LOE ID:
290173
Pollutant:
Diazinon
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
None
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
The Arroyo Las Positas Creek watershed was monitored as part of SWAMP assessment. Neither sample exceeded the water quality objectives for Chlorpyrifos, Dacthal, diazinon, disulfoton, endosulfan, Lindane/gamma Hexachlorocyclohexane (gamma-HCH), methyl parathion, thiobencarb.
All waters shall be maintained free of toxic substances that are lethal to or that produce other detrimental responses in aquatic organisms. There shall be no chronic toxicity in ambient waters. Chronic toxicity is a detrimental biological effect on growth rate, reproduction, fertilization success, larval development, population abundance, community composition, or any other relevant measure of the health of an organism, population, or community.Diazinon water quality objective, 0.1 ug/L (acute)
Insufficient information is available to determine beneficial use support for this waterbody-pollutant combination with the statistical power and confidence required by the Listing Policy. Beneficial use support will be reassessed in a future cycle, if more data are available.
Regional Board Decision Recommendation:
After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list. The readily available data and information is insufficient to determine, with the power and confidence of the Listing Policy, the applicable beneficial use support rating.
State Board Review of Regional Board Conclusion and Recommendation:
State Board Decision Recommendation:
After review of this Regional Board decision, SWRCB staff recommend the decision be approved by the State Board.
Listing Extent:
Line of Evidence (LOE) for Decision ID 141730, Alkalinity as CaCO3
Region 2
Arroyo Las Positas
LOE ID:
276594
Pollutant:
Alkalinity as CaCO3
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2012 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Alkalinity as CaCO3.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
The USEPA recommended alkalinity criterion continuous concentration (CCC) for the protection of aquatic life in freshwater is a minimum value of 20,000 ug/L (4-day average).
Guideline Reference:
DECISION ID
141730
Region 2
Arroyo Las Positas
Pollutant:
Alkalinity as CaCO3
Final Listing Decision:
Do Not List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:
New Decision
Revision Status
Revised
Impairment from Pollutant or Pollution:
Pollutant
Regional Board Conclusion:
Insufficient information is available to determine beneficial use support for this waterbody-pollutant combination with the statistical power and confidence required by the Listing Policy. Beneficial use support will be reassessed in a future cycle, if more data are available.
Regional Board Decision Recommendation:
After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list. The readily available data and information is insufficient to determine, with the power and confidence of the Listing Policy, the applicable beneficial use support rating.
State Board Review of Regional Board Conclusion and Recommendation:
State Board Decision Recommendation:
After review of this Regional Board decision, SWRCB staff recommend the decision be approved by the State Board.
Listing Extent:
Line of Evidence (LOE) for Decision ID 141730, Alkalinity as CaCO3
Region 2
Arroyo Las Positas
LOE ID:
276594
Pollutant:
Alkalinity as CaCO3
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2012 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Alkalinity as CaCO3.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
The USEPA recommended alkalinity criterion continuous concentration (CCC) for the protection of aquatic life in freshwater is a minimum value of 20,000 ug/L (4-day average).
Line of Evidence (LOE) for Decision ID 141730, Alkalinity as CaCO3
Region 2
Arroyo Las Positas
LOE ID:
276638
Pollutant:
Alkalinity as CaCO3
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2015 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Alkalinity as CaCO3.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
The USEPA recommended alkalinity criterion continuous concentration (CCC) for the protection of aquatic life in freshwater is a minimum value of 20,000 ug/L (4-day average).
Line of Evidence (LOE) for Decision ID 141730, Alkalinity as CaCO3
Region 2
Arroyo Las Positas
LOE ID:
276638
Pollutant:
Alkalinity as CaCO3
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2015 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Alkalinity as CaCO3.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
The USEPA recommended alkalinity criterion continuous concentration (CCC) for the protection of aquatic life in freshwater is a minimum value of 20,000 ug/L (4-day average).
Line of Evidence (LOE) for Decision ID 141730, Alkalinity as CaCO3
Region 2
Arroyo Las Positas
LOE ID:
276614
Pollutant:
Alkalinity as CaCO3
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
3
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed SWAMP RWB2 Monitoring data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 3 samples exceeded the water quality threshold for Alkalinity as CaCO3.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
The USEPA recommended alkalinity criterion continuous concentration (CCC) for the protection of aquatic life in freshwater is a minimum value of 20,000 ug/L (4-day average).
Line of Evidence (LOE) for Decision ID 141730, Alkalinity as CaCO3
Region 2
Arroyo Las Positas
LOE ID:
276598
Pollutant:
Alkalinity as CaCO3
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2015 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Alkalinity as CaCO3.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on atd>
Alkalinity as CaCO3
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
3
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed SWAMP RWB2 Monitoring data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 3 samples exceeded the water quality threshold for Alkalinity as CaCO3.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
The USEPA recommended alkalinity criterion continuous concentration (CCC) for the protection of aquatic life in freshwater is a minimum value of 20,000 ug/L (4-day average).
Line of Evidence (LOE) for Decision ID 141730, Alkalinity as CaCO3
Region 2
Arroyo Las Positas
LOE ID:
276598
Pollutant:
Alkalinity as CaCO3
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2015 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Alkalinity as CaCO3.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
The USEPA recommended alkalinity criterion continuous concentration (CCC) for the protection of aquatic life in freshwater is a minimum value of 20,000 ug/L (4-day average).
Line of Evidence (LOE) for Decision ID 141730, Alkalinity as CaCO3
Region 2
Arroyo Las Positas
LOE ID:
276637
Pollutant:
Alkalinity as CaCO3
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2014 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Alkalinity as CaCO3.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
The USEPA recommended alkalinity criterion continuous concentration (CCC) for the protection of aquatic life in freshwater is a minimum value of 20,000 ug/L (4-day average).
The USEPA recommended alkalinity criterion continuous concentration (CCC) for the protection of aquatic life in freshwater is a minimum value of 20,000 ug/L (4-day average).
Line of Evidence (LOE) for Decision ID 141730, Alkalinity as CaCO3
Region 2
Arroyo Las Positas
LOE ID:
276637
Pollutant:
Alkalinity as CaCO3
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2014 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Alkalinity as CaCO3.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
The USEPA recommended alkalinity criterion continuous concentration (CCC) for the protection of aquatic life in freshwater is a minimum value of 20,000 ug/L (4-day average).
Line of Evidence (LOE) for Decision ID 141730, Alkalinity as CaCO3
Region 2
Arroyo Las Positas
LOE ID:
276658
Pollutant:
Alkalinity as CaCO3
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
3
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed SWAMP RWB2 Monitoring data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 3 samples exceeded the water quality threshold for Alkalinity as CaCO3.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
The USEPA recommended alkalinity criterion continuous concentration (CCC) for the protection of aquatic life in freshwater is a minimum value of 20,000 ug/L (4-day average).
Line of Evidence (LOE) for Decision ID 141730, Alkalinity as CaCO3
Region 2
Arroyo Las Positas
LOE ID:
276639
Pollutant:
Alkalinity as CaCO3
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
3
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed SWAMP RWB2 Monitoring data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 3 samples exceeded the water quality threshold for Alkalinity as CaCO3.
100%; text-align: left; PADDING-TOP: 3px; font-smooth: always">Line of Evidence (LOE) for Decision ID 141730, Alkalinity as CaCO3
Region 2
Arroyo Las Positas
LOE ID:
276658
Pollutant:
Alkalinity as CaCO3
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
3
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed SWAMP RWB2 Monitoring data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 3 samples exceeded the water quality threshold for Alkalinity as CaCO3.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
The USEPA recommended alkalinity criterion continuous concentration (CCC) for the protection of aquatic life in freshwater is a minimum value of 20,000 ug/L (4-day average).
Line of Evidence (LOE) for Decision ID 141730, Alkalinity as CaCO3
Region 2
Arroyo Las Positas
LOE ID:
276639
Pollutant:
Alkalinity as CaCO3
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
3
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed SWAMP RWB2 Monitoring data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 3 samples exceeded the water quality threshold for Alkalinity as CaCO3.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
The USEPA recommended alkalinity criterion continuous concentration (CCC) for the protection of aquatic life in freshwater is a minimum value of 20,000 ug/L (4-day average).
Line of Evidence (LOE) for Decision ID 141730, Alkalinity as CaCO3
Region 2
Arroyo Las Positas
LOE ID:
276618
Pollutant:
Alkalinity as CaCO3
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2014 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Alkalinity as CaCO3.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
The USEPA recommended alkalinity criterion continuous concentration (CCC) for the protection of aquatic life in freshwater is a minimum value of 20,000 ug/L (4-day average).
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
The USEPA recommended alkalinity criterion continuous concentration (CCC) for the protection of aquatic life in freshwater is a minimum value of 20,000 ug/L (4-day average).
Line of Evidence (LOE) for Decision ID 141730, Alkalinity as CaCO3
Region 2
Arroyo Las Positas
LOE ID:
276618
Pollutant:
Alkalinity as CaCO3
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2014 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Alkalinity as CaCO3.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
The USEPA recommended alkalinity criterion continuous concentration (CCC) for the protection of aquatic life in freshwater is a minimum value of 20,000 ug/L (4-day average).
Line of Evidence (LOE) for Decision ID 141730, Alkalinity as CaCO3
Region 2
Arroyo Las Positas
LOE ID:
276640
Pollutant:
Alkalinity as CaCO3
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
4
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed SWAMP RWB2 Monitoring data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 4 samples exceeded the water quality threshold for Alkalinity as CaCO3.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
The USEPA recommended alkalinity criterion continuous concentration (CCC) for the protection of aquatic life in freshwater is a minimum value of 20,000 ug/L (4-day average).
Line of Evidence (LOE) for Decision ID 141730, Alkalinity as CaCO3
Region 2
Arroyo Las Positas
LOE ID:
276640
Pollutant:
Alkalinity as CaCO3
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
4
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed SWAMP RWB2 Monitoring data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 4 samples exceeded the water quality threshold for Alkalinity as CaCO3.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
The USEPA recommended alkalinity criterion continuous concentration (CCC) for the protection of aquatic life in freshwater is a minimum value of 20,000 ug/L (4-day average).
Line of Evidence (LOE) for Decision ID 141730, Alkalinity as CaCO3
Region 2
Arroyo Las Positas
LOE ID:
277369
Pollutant:
Alkalinity as CaCO3
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2014 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Alkalinity as CaCO3.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
The USEPA recommended alkalinity criterion continuous concentration (CCC) for the protection of aquatic life in freshwater is a minimum value of 20,000 ug/L (4-day average).
Line of Evidence (LOE) for Decision ID 141730, Alkalinity as CaCO3
Region 2
Arroyo Las Positas
LOE ID:
276595
Pollutant:
Alkalinity as CaCO3
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2014 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Alkalinity as CaCO3.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
Water Board staff assessed BASMAA RMC Monitoring in WY2014 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Alkalinity as CaCO3.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
The USEPA recommended alkalinity criterion continuous concentration (CCC) for the protection of aquatic life in freshwater is a minimum value of 20,000 ug/L (4-day average).
Line of Evidence (LOE) for Decision ID 141730, Alkalinity as CaCO3
Region 2
Arroyo Las Positas
LOE ID:
276595
Pollutant:
Alkalinity as CaCO3
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2014 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Alkalinity as CaCO3.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
The USEPA recommended alkalinity criterion continuous concentration (CCC) for the protection of aquatic life in freshwater is a minimum value of 20,000 ug/L (4-day average).
Line of Evidence (LOE) for Decision ID 141730, Alkalinity as CaCO3
Region 2
Arroyo Las Positas
LOE ID:
276615
Pollutant:
Alkalinity as CaCO3
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
4
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed SWAMP RWB2 Monitoring data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 4 samples exceeded the water quality threshold for Alkalinity as CaCO3.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
The USEPA recommended alkalinity criterion continuous concentration (CCC) for the protection of aquatic life in freshwater is a minimum value of 20,000 ug/L (4-day average).
Line of Evidence (LOE) for Decision ID 141730, Alkalinity as CaCO3
The USEPA recommended alkalinity criterion continuous concentration (CCC) for the protection of aquatic life in freshwater is a minimum value of 20,000 ug/L (4-day average).
Line of Evidence (LOE) for Decision ID 141730, Alkalinity as CaCO3
Region 2
Arroyo Las Positas
LOE ID:
276615
Pollutant:
Alkalinity as CaCO3
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
4
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed SWAMP RWB2 Monitoring data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 4 samples exceeded the water quality threshold for Alkalinity as CaCO3.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
The USEPA recommended alkalinity criterion continuous concentration (CCC) for the protection of aquatic life in freshwater is a minimum value of 20,000 ug/L (4-day average).
Line of Evidence (LOE) for Decision ID 141730, Alkalinity as CaCO3
Region 2
Arroyo Las Positas
LOE ID:
276596
Pollutant:
Alkalinity as CaCO3
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2014 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Alkalinity as CaCO3.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
The USEPA recommended alkalinity criterion continuous concentration (CCC) for the protection of aquatic life in freshwater is a minimum value of 20,000 ug/L (4-day average).
Line of Evidence (LOE) for Decision ID 141730, Alkalinity as CaCO3
Region 2
Arroyo Las Positas
LOE ID:
276597
Pollutant:
Alkalinity as CaCO3
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2014 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Alkalinity as CaCO3.
Water Board staff assessed BASMAA RMC Monitoring in WY2014 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Alkalinity as CaCO3.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
The USEPA recommended alkalinity criterion continuous concentration (CCC) for the protection of aquatic life in freshwater is a minimum value of 20,000 ug/L (4-day average).
Line of Evidence (LOE) for Decision ID 141730, Alkalinity as CaCO3
Region 2
Arroyo Las Positas
LOE ID:
276597
Pollutant:
Alkalinity as CaCO3
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2014 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Alkalinity as CaCO3.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
The USEPA recommended alkalinity criterion continuous concentration (CCC) for the protection of aquatic life in freshwater is a minimum value of 20,000 ug/L (4-day average).
Line of Evidence (LOE) for Decision ID 141730, Alkalinity as CaCO3
Region 2
Arroyo Las Positas
LOE ID:
276616
Pollutant:
Alkalinity as CaCO3
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
3
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed SWAMP RWB2 Monitoring data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 3 samples exceeded the water quality threshold for Alkalinity as CaCO3.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
The USEPA recommended alkalinity criterion continuous concentration (CCC) for the protection of aquatic life in freshwater is a minimum value of 20,000 ug/L (4-day average).
Line of Evidence (LOE) for Decision ID 141730, Alkalinity as CaCO3
Region 2
Arroyo Las Positas
LOE ID:
276617
Pollutant:
Alkalinity as CaCO3
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2012 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Alkalinity as CaCO3.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
The USEPA recommended alkalinity criterion continuous concentration (CCC) for the protection of aquatic life in freshwater is a minimum value of 20,000 ug/L (4-day average).
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
The USEPA recommended alkalinity criterion continuous concentration (CCC) for the protection of aquatic life in freshwater is a minimum value of 20,000 ug/L (4-day average).
Line of Evidence (LOE) for Decision ID 141730, Alkalinity as CaCO3
Region 2
Arroyo Las Positas
LOE ID:
276616
Pollutant:
Alkalinity as CaCO3
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
3
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed SWAMP RWB2 Monitoring data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 3 samples exceeded the water quality threshold for Alkalinity as CaCO3.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
The USEPA recommended alkalinity criterion continuous concentration (CCC) for the protection of aquatic life in freshwater is a minimum value of 20,000 ug/L (4-day average).
Line of Evidence (LOE) for Decision ID 141730, Alkalinity as CaCO3
Region 2
Arroyo Las Positas
LOE ID:
276617
Pollutant:
Alkalinity as CaCO3
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2012 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Alkalinity as CaCO3.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
The USEPA recommended alkalinity criterion continuous concentration (CCC) for the protection of aquatic life in freshwater is a minimum value of 20,000 ug/L (4-day average).
Insufficient information is available to determine beneficial use support for this waterbody-pollutant combination with the statistical power and confidence required by the Listing Policy. Beneficial use support will be reassessed in a future cycle, if more data are available.
Regional Board Decision Recommendation:
After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list. The readily available data and information is insufficient to determine, with the power and confidence of the Listing Policy, the applicable beneficial use support rating.
State Board Review of Regional Board Conclusion and Recommendation:
State Board Decision Recommendation:
After review of the available data and information, SWRCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list because it cannot be determined if applicable water quality standards are not being exceeded.
Listing Extent:
Line of Evidence (LOE) for Decision ID 151624, Aluminum
Region 2
Arroyo Las Positas
LOE ID:
307167
Pollutant:
Aluminum
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Dissolved
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed SWAMP RWB2 Monitoring data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Aluminum.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
The aluminum criterion for the protection of aquatic life, is pH, total hardness, and dissolved organic carbon (DOC) dependent. When total hardness or DOC data were not available, default values based on the level III ecoregions developed by U.S EPA were substituted (EPA, 2018). When pH data were not available, the median pH value for the ecoregion, a pH value from a comparable waterbody, or a pH value from a local study in the same waterbody was used as a comparable surrogate.
Line of Evidence (LOE) for Decision ID 151624, Aluminum
Region 2
Arroyo Las Positas
LOE ID:
307174
Pollutant:
Aluminum
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Dissolved
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed SWAMP RWB2 Monitoring data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Aluminum.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
The aluminum criterion for the protection of aquatic life, is pH, total hardness, and dissolved organic carbon (DOC) dependent. When total hardness or DOC data were not available, default values based on the level III ecoregions developed by U.S EPA were substituted (EPA, 2018). When pH data were not available, the median pH value for the ecoregion, a pH value from a comparable waterbody, or a pH value from a local study in the same waterbody was used as a comparable surrogate.
Insufficient information is available to determine beneficial use support for this waterbody-pollutant combination with the statistical power and confidence required by the Listing Policy. Beneficial use support will be reassessed in a future cycle, if more data are available.
Regional Board Decision Recommendation:
After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list. The readily available data and information is insufficient to determine, with the power and confidence of the Listing Policy, the applicable beneficial use support rating.
State Board Review of Regional Board Conclusion and Recommendation:
State Board Decision Recommendation:
After review of the available data and information, SWRCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list because it cannot be determined if applicable water quality standards are not being exceeded.
Listing Extent:
Line of Evidence (LOE) for Decision ID 151624, Aluminum
Region 2
Arroyo Las Positas
LOE ID:
307167
Pollutant:
Aluminum
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Dissolved
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed SWAMP RWB2 Monitoring data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Aluminum.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
The aluminum criterion for the protection of aquatic life, is pH, total hardness, and dissolved organic carbon (DOC) dependent. When total hardness or DOC data were not available, default values based on the level III ecoregions developed by U.S EPA were substituted (EPA, 2018). When pH data were not available, the median pH value for the ecoregion, a pH value from a comparable waterbody, or a pH value from a local study in the same waterbody was used as a comparable surrogate.
Line of Evidence (LOE) for Decision ID 151624, Aluminum
Region 2
Arroyo Las Positas
LOE ID:
307174
Pollutant:
Aluminum
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Dissolved
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed SWAMP RWB2 Monitoring data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Aluminum.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
The aluminum criterion for the protection of aquatic life, is pH, total hardness, and dissolved organic carbon (DOC) dependent. When total hardness or DOC data were not available, default values based on the level III ecoregions developed by U.S EPA were substituted (EPA, 2018). When pH data were not available, the median pH value for the ecoregion, a pH value from a comparable waterbody, or a pH value from a local study in the same waterbody was used as a comparable surrogate.
Insufficient information is available to determine beneficial use support for this waterbody-pollutant combination with the statistical power and confidence required by the Listing Policy. Beneficial use support will be reassessed in a future cycle, if more data are available.
Regional Board Decision Recommendation:
After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list. The readily available data and information is insufficient to determine, with the power and confidence of the Listing Policy, the applicable beneficial use support rating.
State Board Review of Regional Board Conclusion and Recommendation:
State Board Decision Recommendation:
After review of the available data and information, SWRCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list because it cannot be determined if applicable water quality standards are not being exceeded.
Listing Extent:
Line of Evidence (LOE) for Decision ID 141693, Anthracene
Region 2
Arroyo Las Positas
LOE ID:
290026
Pollutant:
Anthracene
LOE Subgroup:
Pollutant-Sediment
Matrix:
Sediment
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Concentrations of Anthracene, fluorene, napthalene, phenanthrene, benz(a)anthracene, benzo(a)pyrene, chrysene, fluoranthrene, pyrene, PAH (total), PCB (total), chlordane, dieldrin, DDD/DDE/DDT, endrin, heptachlor epoxide, and HCH, gamma in one sediment sample collected in spring 2005 did not exceed the sediment quality guidelines.
Insufficient information is available to determine beneficial use support for this waterbody-pollutant combination with the statistical power and confidence required by the Listing Policy. Beneficial use support will be reassessed in a future cycle, if more data are available.
Regional Board Decision Recommendation:
After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list. The readily available data and information is insufficient to determine, with the power and confidence of the Listing Policy, the applicable beneficial use support rating.
State Board Review of Regional Board Conclusion and Recommendation:
State Board Decision Recommendation:
After review of the available data and information, SWRCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list because it cannot be determined if applicable water quality standards are not being exceeded.
Listing Extent:
Line of Evidence (LOE) for Decision ID 141693, Anthracene
Region 2
Arroyo Las Positas
LOE ID:
290026
Pollutant:
Anthracene
LOE Subgroup:
Pollutant-Sediment
Matrix:
Sediment
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Concentrations of Anthracene, fluorene, napthalene, phenanthrene, benz(a)anthracene, benzo(a)pyrene, chrysene, fluoranthrene, pyrene, PAH (total), PCB (total), chlordane, dieldrin, DDD/DDE/DDT, endrin, heptachlor epoxide, and HCH, gamma in one sediment sample collected in spring 2005 did not exceed the sediment quality guidelines.
Insufficient information is available to determine beneficial use support for this waterbody-pollutant combination with the statistical power and confidence required by the Listing Policy. Beneficial use support will be reassessed in a future cycle, if more data are available.
Regional Board Decision Recommendation:
After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list. The readily available data and information is insufficient to determine, with the power and confidence of the Listing Policy, the applicable beneficial use support rating.
State Board Review of Regional Board Conclusion and Recommendation:
State Board Decision Recommendation:
After review of this Regional Board decision, SWRCB staff recommend the decision be approved by the State Board.
Listing Extent:
Line of Evidence (LOE) for Decision ID 141694, Arsenic
Region 2
Arroyo Las Positas
LOE ID:
290114
Pollutant:
Arsenic
LOE Subgroup:
Pollutant-Sediment
Matrix:
Sediment
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Concentrations of arsenic, cadmium, copper, lead, mercury and zinc in one sediment sample collected in spring 2005 did not exceed the sediment quality guidelines.
Insufficient information is available to determine beneficial use support for this waterbody-pollutant combination with the statistical power and confidence required by the Listing Policy. Beneficial use support will be reassessed in a future cycle, if more data are available.
Regional Board Decision Recommendation:
After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list. The readily available data and information is insufficient to determine, with the power and confidence of the Listing Policy, the applicable beneficial use support rating.
State Board Review of Regional Board Conclusion and Recommendation:
State Board Decision Recommendation:
After review of this Regional Board decision, SWRCB staff recommend the decision be approved by the State Board.
Listing Extent:
Line of Evidence (LOE) for Decision ID 141694, Arsenic
Region 2
Arroyo Las Positas
LOE ID:
290114
Pollutant:
Arsenic
LOE Subgroup:
Pollutant-Sediment
Matrix:
Sediment
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Concentrations of arsenic, cadmium, copper, lead, mercury and zinc in one sediment sample collected in spring 2005 did not exceed the sediment quality guidelines.
Line of Evidence (LOE) for Decision ID 141694, Arsenic
Region 2
Arroyo Las Positas
LOE ID:
280168
Pollutant:
Arsenic
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Dissolved
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed SWAMP RWB2 Monitoring data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Arsenic.
The dissolved arsenic criterion continuous concentration (expressed as a 4-day average) to protect aquatic life in freshwater is 150 ug/L. The conversion factor used to convert the total fraction criterion for arsenic to dissolved fraction criterion is 1. Therefore all data was considered to be representative of the dissolved fraction. (California Toxics Rule, 2000)
Line of Evidence (LOE) for Decision ID 141694, Arsenic
Region 2
Arroyo Las Positas
LOE ID:
290132
Pollutant:
Arsenic
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Dissolved
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
6
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
The Arroyo Las Positas Creek watershed was monitored as part of SWAMP assessment. None of the six samples exceeded the water quality objectives for arsenic, chromium VI, copper, lead, nickel, silver and zinc.Concentrations of total dissolved chromium were well below the objective for chromium VI.
All waters shall be maintained free of toxic substances that are lethal to or that produce other detrimental responses in aquatic organisms. Table 3-4 in the Basin Plan (2007) lists freshwater water quality objectives for toxic pollutants: arsenic- 150 ug/L, chromium VI- 11 ug/L, copper - 9.0 ug/L, lead - 2.5 ug/L; nickel - 52 ug/L, silver-3.4 ug/L and zinc - 120 ug/L.
Data were collected at three sampling locations on Arroyo Las Positas Creek - ALP010 (El Charro), ALP100 (Altamont Creek), and ALP110 (Arroyo Las Positas).
Temporal Representation:
Samples were collected at all three sites during spring and dry seasons of the 2001-2002 sampling season.
Environmental Conditions:
QAPP Information:
All samples were collected and analyzed using procedures comparable with the SWAMP Quality Assurance Management Plan (SWRCB, 2002).
Line of Evidence (LOE) for Decision ID 141694, Arsenic
Region 2
Arroyo Las Positas
LOE ID:
280208
Pollutant:
Arsenic
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Dissolved
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed SWAMP RWB2 Monitoring data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Arsenic.
The dissolved arsenic criterion continuous concentration (expressed as a 4-day average) to protect aquatic life in freshwater is 150 ug/L. The conversion factor used to convert the total fraction criterion for arsenic to dissolved fraction criterion is 1. Therefore all data was considered to be representative of the dissolved fraction. (California Toxics Rule, 2000)
Line of Evidence (LOE) for Decision ID 141694, Arsenic
Region 2
Arroyo Las Positas
LOE ID:
280168
Pollutant:
Arsenic
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Dissolved
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed SWAMP RWB2 Monitoring data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Arsenic.
The dissolved arsenic criterion continuous concentration (expressed as a 4-day average) to protect aquatic life in freshwater is 150 ug/L. The conversion factor used to convert the total fraction criterion for arsenic to dissolved fraction criterion is 1. Therefore all data was considered to be representative of the dissolved fraction. (California Toxics Rule, 2000)
Line of Evidence (LOE) for Decision ID 141694, Arsenic
Region 2
Arroyo Las Positas
LOE ID:
290132
Pollutant:
Arsenic
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Dissolved
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
6
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
The Arroyo Las Positas Creek watershed was monitored as part of SWAMP assessment. None of the six samples exceeded the water quality objectives for arsenic, chromium VI, copper, lead, nickel, silver and zinc.Concentrations of total dissolved chromium were well below the objective for chromium VI.
All waters shall be maintained free of toxic substances that are lethal to or that produce other detrimental responses in aquatic organisms. Table 3-4 in the Basin Plan (2007) lists freshwater water quality objectives for toxic pollutants: arsenic- 150 ug/L, chromium VI- 11 ug/L, copper - 9.0 ug/L, lead - 2.5 ug/L; nickel - 52 ug/L, silver-3.4 ug/L and zinc - 120 ug/L.
Data were collected at three sampling locations on Arroyo Las Positas Creek - ALP010 (El Charro), ALP100 (Altamont Creek), and ALP110 (Arroyo Las Positas).
Temporal Representation:
Samples were collected at all three sites during spring and dry seasons of the 2001-2002 sampling season.
Environmental Conditions:
QAPP Information:
All samples were collected and analyzed using procedures comparable with the SWAMP Quality Assurance Management Plan (SWRCB, 2002).
Line of Evidence (LOE) for Decision ID 141694, Arsenic
Region 2
Arroyo Las Positas
LOE ID:
280208
Pollutant:
Arsenic
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Dissolved
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed SWAMP RWB2 Monitoring data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Arsenic.
The dissolved arsenic criterion continuous concentration (expressed as a 4-day average) to protect aquatic life in freshwater is 150 ug/L. The conversion factor used to convert the total fraction criterion for arsenic to dissolved fraction criterion is 1. Therefore all data was considered to be representative of the dissolved fraction. (California Toxics Rule, 2000)
Insufficient information is available to determine beneficial use support for this waterbody-pollutant combination with the statistical power and confidence required by the Listing Policy. Beneficial use support will be reassessed in a future cycle, if more data are available.
Regional Board Decision Recommendation:
After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list. The readily available data and information is insufficient to determine, with the power and confidence of the Listing Policy, the applicable beneficial use support rating.
State Board Review of Regional Board Conclusion and Recommendation:
State Board Decision Recommendation:
After review of the available data and information, SWRCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list because it cannot be determined if applicable water quality standards are not being exceeded.
Listing Extent:
Line of Evidence (LOE) for Decision ID 141696, Benzo(a)anthracene
Region 2
Arroyo Las Positas
LOE ID:
290027
Pollutant:
Benzo(a)anthracene
LOE Subgroup:
Pollutant-Sediment
Matrix:
Sediment
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Concentrations of Anthracene, fluorene, napthalene, phenanthrene, benz(a)anthracene, benzo(a)pyrene, chrysene, fluoranthrene, pyrene, PAH (total), PCB (total), chlordane, dieldrin, DDD/DDE/DDT, endrin, heptachlor epoxide, and HCH, gamma in one sediment sample collected in spring 2005 did not exceed the sediment quality guidelines.
Insufficient information is available to determine beneficial use support for this waterbody-pollutant combination with the statistical power and confidence required by the Listing Policy. Beneficial use support will be reassessed in a future cycle, if more data are available.
Regional Board Decision Recommendation:
After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list. The readily available data and information is insufficient to determine, with the power and confidence of the Listing Policy, the applicable beneficial use support rating.
State Board Review of Regional Board Conclusion and Recommendation:
State Board Decision Recommendation:
After review of the available data and information, SWRCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list because it cannot be determined if applicable water quality standards are not being exceeded.
Listing Extent:
Line of Evidence (LOE) for Decision ID 141696, Benzo(a)anthracene
Region 2
Arroyo Las Positas
LOE ID:
290027
Pollutant:
Benzo(a)anthracene
LOE Subgroup:
Pollutant-Sediment
Matrix:
Sediment
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Concentrations of Anthracene, fluorene, napthalene, phenanthrene, benz(a)anthracene, benzo(a)pyrene, chrysene, fluoranthrene, pyrene, PAH (total), PCB (total), chlordane, dieldrin, DDD/DDE/DDT, endrin, heptachlor epoxide, and HCH, gamma in one sediment sample collected in spring 2005 did not exceed the sediment quality guidelines.
Insufficient information is available to determine beneficial use support for this waterbody-pollutant combination with the statistical power and confidence required by the Listing Policy. Beneficial use support will be reassessed in a future cycle, if more data are available.
Regional Board Decision Recommendation:
After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list. The readily available data and information is insufficient to determine, with the power and confidence of the Listing Policy, the applicable beneficial use support rating.
State Board Review of Regional Board Conclusion and Recommendation:
State Board Decision Recommendation:
After review of the available data and information, SWRCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list because it cannot be determined if applicable water quality standards are not being exceeded.
Listing Extent:
Line of Evidence (LOE) for Decision ID 141695, Benzo(a)pyrene
Region 2
Arroyo Las Positas
LOE ID:
290039
Pollutant:
Benzo(a)pyrene
LOE Subgroup:
Pollutant-Sediment
Matrix:
Sediment
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Concentrations of Anthracene, fluorene, napthalene, phenanthrene, benz(a)anthracene, benzo(a)pyrene, chrysene, fluoranthrene, pyrene, PAH (total), PCB (total), chlordane, dieldrin, DDD/DDE/DDT, endrin, heptachlor epoxide, and HCH, gamma in one sediment sample collected in spring 2005 did not exceed the sediment quality guidelines.
Insufficient information is available to determine beneficial use support for this waterbody-pollutant combination with the statistical power and confidence required by the Listing Policy. Beneficial use support will be reassessed in a future cycle, if more data are available.
Regional Board Decision Recommendation:
After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list. The readily available data and information is insufficient to determine, with the power and confidence of the Listing Policy, the applicable beneficial use support rating.
State Board Review of Regional Board Conclusion and Recommendation:
State Board Decision Recommendation:
After review of the available data and information, SWRCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list because it cannot be determined if applicable water quality standards are not being exceeded.
Listing Extent:
Line of Evidence (LOE) for Decision ID 141695, Benzo(a)pyrene
Region 2
Arroyo Las Positas
LOE ID:
290039
Pollutant:
Benzo(a)pyrene
LOE Subgroup:
Pollutant-Sediment
Matrix:
Sediment
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Concentrations of Anthracene, fluorene, napthalene, phenanthrene, benz(a)anthracene, benzo(a)pyrene, chrysene, fluoranthrene, pyrene, PAH (total), PCB (total), chlordane, dieldrin, DDD/DDE/DDT, endrin, heptachlor epoxide, and HCH, gamma in one sediment sample collected in spring 2005 did not exceed the sediment quality guidelines.
Insufficient information is available to determine beneficial use support for this waterbody-pollutant combination with the statistical power and confidence required by the Listing Policy. Beneficial use support will be reassessed in a future cycle, if more data are available.
Regional Board Decision Recommendation:
After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list. The readily available data and information is insufficient to determine, with the power and confidence of the Listing Policy, the applicable beneficial use support rating.
State Board Review of Regional Board Conclusion and Recommendation:
State Board Decision Recommendation:
After review of this Regional Board decision, SWRCB staff recommend the decision be approved by the State Board.
Listing Extent:
Line of Evidence (LOE) for Decision ID 141697, Cadmium
Region 2
Arroyo Las Positas
LOE ID:
290115
Pollutant:
Cadmium
LOE Subgroup:
Pollutant-Sediment
Matrix:
Sediment
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Concentrations of arsenic, cadmium, copper, lead, mercury and zinc in one sediment sample collected in spring 2005 did not exceed the sediment quality guidelines.
Line of Evidence (LOE) for Decision ID 141697, Cadmium
Region 2
Arroyo Las Positas
LOE ID:
280320
Pollutant:
Cadmium
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Dissolved
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed SWAMP RWB2 Monitoring data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Cadmium.
The dissolved cadmium criterion continuous concentration (expressed as a 4-day average) to protect aquatic life in freshwater is hardness dependent. The criterion when calculated using a default hardness of 100 mg/L is 2.2 ug/L (California Toxics Rule, 2000).
Line of Evidence (LOE) for Decision ID 141697, Cadmium
Region 2
Arroyo Las Positas
LOE ID:
280391
Pollutant:
Cadmium
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Dissolved
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed SWAMP RWB2 Monitoring data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Cadmium.
The dissolved cadmium criterion continuous concentration (expressed as a 4-day average) to protect aquatic life in freshwater is hardness dependent. The criterion when calculated using a default hardness of 100 mg/L is 2.2 ug/L (California Toxics Rule, 2000).
Insufficient information is available to determine beneficial use support for this waterbody-pollutant combination with the statistical power and confidence required by the Listing Policy. Beneficial use support will be reassessed in a future cycle, if more data are available.
Regional Board Decision Recommendation:
After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list. The readily available data and information is insufficient to determine, with the power and confidence of the Listing Policy, the applicable beneficial use support rating.
State Board Review of Regional Board Conclusion and Recommendation:
State Board Decision Recommendation:
After review of this Regional Board decision, SWRCB staff recommend the decision be approved by the State Board.
Listing Extent:
Line of Evidence (LOE) for Decision ID 141697, Cadmium
Region 2
Arroyo Las Positas
LOE ID:
290115
Pollutant:
Cadmium
LOE Subgroup:
Pollutant-Sediment
Matrix:
Sediment
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Concentrations of arsenic, cadmium, copper, lead, mercury and zinc in one sediment sample collected in spring 2005 did not exceed the sediment quality guidelines.
Line of Evidence (LOE) for Decision ID 141697, Cadmium
Region 2
Arroyo Las Positas
LOE ID:
280320
Pollutant:
Cadmium
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Dissolved
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed SWAMP RWB2 Monitoring data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Cadmium.
The dissolved cadmium criterion continuous concentration (expressed as a 4-day average) to protect aquatic life in freshwater is hardness dependent. The criterion when calculated using a default hardness of 100 mg/L is 2.2 ug/L (California Toxics Rule, 2000).
Line of Evidence (LOE) for Decision ID 141697, Cadmium
Region 2
Arroyo Las Positas
LOE ID:
280391
Pollutant:
Cadmium
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Dissolved
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed SWAMP RWB2 Monitoring data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Cadmium.
The dissolved cadmium criterion continuous concentration (expressed as a 4-day average) to protect aquatic life in freshwater is hardness dependent. The criterion when calculated using a default hardness of 100 mg/L is 2.2 ug/L (California Toxics Rule, 2000).
Insufficient information is available to determine beneficial use support for this waterbody-pollutant combination with the statistical power and confidence required by the Listing Policy. Beneficial use support will be reassessed in a future cycle, if more data are available.
Regional Board Decision Recommendation:
After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list. The readily available data and information is insufficient to determine, with the power and confidence of the Listing Policy, the applicable beneficial use support rating.
State Board Review of Regional Board Conclusion and Recommendation:
State Board Decision Recommendation:
After review of the available data and information, SWRCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list because it cannot be determined if applicable water quality standards are not being exceeded.
Listing Extent:
Line of Evidence (LOE) for Decision ID 141698, Chlordane
Region 2
Arroyo Las Positas
LOE ID:
290040
Pollutant:
Chlordane
LOE Subgroup:
Pollutant-Sediment
Matrix:
Sediment
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Concentrations of Anthracene, fluorene, napthalene, phenanthrene, benz(a)anthracene, benzo(a)pyrene, chrysene, fluoranthrene, pyrene, PAH (total), PCB (total), chlordane, dieldrin, DDD/DDE/DDT, endrin, heptachlor epoxide, and HCH, gamma in one sediment sample collected in spring 2005 did not exceed the sediment quality guidelines.
Insufficient information is available to determine beneficial use support for this waterbody-pollutant combination with the statistical power and confidence required by the Listing Policy. Beneficial use support will be reassessed in a future cycle, if more data are available.
Regional Board Decision Recommendation:
After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list. The readily available data and information is insufficient to determine, with the power and confidence of the Listing Policy, the applicable beneficial use support rating.
State Board Review of Regional Board Conclusion and Recommendation:
State Board Decision Recommendation:
After review of the available data and information, SWRCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list because it cannot be determined if applicable water quality standards are not being exceeded.
Listing Extent:
Line of Evidence (LOE) for Decision ID 141698, Chlordane
Region 2
Arroyo Las Positas
LOE ID:
290040
Pollutant:
Chlordane
LOE Subgroup:
Pollutant-Sediment
Matrix:
Sediment
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Concentrations of Anthracene, fluorene, napthalene, phenanthrene, benz(a)anthracene, benzo(a)pyrene, chrysene, fluoranthrene, pyrene, PAH (total), PCB (total), chlordane, dieldrin, DDD/DDE/DDT, endrin, heptachlor epoxide, and HCH, gamma in one sediment sample collected in spring 2005 did not exceed the sediment quality guidelines.
Insufficient information is available to determine beneficial use support for this waterbody-pollutant combination with the statistical power and confidence required by the Listing Policy. Beneficial use support will be reassessed in a future cycle, if more data are available.
Although there was a sufficient number of samples to assess total chlorine, this water body was given a use rating of Insufficient Information and a Do Not List decision. First, data were collected with field instruments that do not have the sensitivity to detect low levels of total chlorine to assess the freshwater water quality objectives of 11 ug/L and 19 ug/L. Secondly, most of the data were collected only once for a given site, and the data were not collected with the purpose of assessing chlorine levels in the water body. A more appropriate sampling to determine water quality impacts of chlorine might be conducted for future Integrated Report assessments.
Regional Board Decision Recommendation:
After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list. The readily available data and information is insufficient to determine, with the power and confidence of the Listing Policy, the applicable beneficial use support rating.
State Board Review of Regional Board Conclusion and Recommendation:
State Board Decision Recommendation:
After review of the available data and information, SWRCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list because it cannot be determined if applicable water quality standards are not being exceeded.
Listing Extent:
Line of Evidence (LOE) for Decision ID 141700, Chlorine
Region 2
Arroyo Las Positas
LOE ID:
282296
Pollutant:
Chlorine
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
1
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2012 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 1 of 1 samples exceeded the water quality threshold for Chlorine, Total Residual.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
DECISION ID
141700
Region 2
Arroyo Las Positas
Pollutant:
Chlorine
Final Listing Decision:
Do Not List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:
New Decision
Revision Status
Revised
Impairment from Pollutant or Pollution:
Pollutant
Regional Board Conclusion:
Insufficient information is available to determine beneficial use support for this waterbody-pollutant combination with the statistical power and confidence required by the Listing Policy. Beneficial use support will be reassessed in a future cycle, if more data are available.
Although there was a sufficient number of samples to assess total chlorine, this water body was given a use rating of Insufficient Information and a Do Not List decision. First, data were collected with field instruments that do not have the sensitivity to detect low levels of total chlorine to assess the freshwater water quality objectives of 11 ug/L and 19 ug/L. Secondly, most of the data were collected only once for a given site, and the data were not collected with the purpose of assessing chlorine levels in the water body. A more appropriate sampling to determine water quality impacts of chlorine might be conducted for future Integrated Report assessments.
Regional Board Decision Recommendation:
After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list. The readily available data and information is insufficient to determine, with the power and confidence of the Listing Policy, the applicable beneficial use support rating.
State Board Review of Regional Board Conclusion and Recommendation:
State Board Decision Recommendation:
After review of the available data and information, SWRCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list because it cannot be determined if applicable water quality standards are not being exceeded.
Listing Extent:
Line of Evidence (LOE) for Decision ID 141700, Chlorine
Region 2
Arroyo Las Positas
LOE ID:
282296
Pollutant:
Chlorine
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
1
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2012 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 1 of 1 samples exceeded the water quality threshold for Chlorine, Total Residual.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
Line of Evidence (LOE) for Decision ID 141700, Chlorine
Region 2
Arroyo Las Positas
LOE ID:
282392
Pollutant:
Chlorine
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2019 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Chlorine, Total Residual.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
Line of Evidence (LOE) for Decision ID 141700, Chlorine
Region 2
Arroyo Las Positas
LOE ID:
282392
Pollutant:
Chlorine
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2019 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Chlorine, Total Residual.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
Line of Evidence (LOE) for Decision ID 141700, Chlorine
Region 2
Arroyo Las Positas
LOE ID:
282492
Pollutant:
Chlorine
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2014 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Chlorine, Total Residual.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
Line of Evidence (LOE) for Decision ID 141700, Chlorine
Region 2
Arroyo Las Positas
LOE ID:
282147
Pollutant:
Chlorine
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2016 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Chlorine, Total Residual.
Water Board staff assessed BASMAA RMC Monitoring in WY2014 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Chlorine, Total Residual.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
Line of Evidence (LOE) for Decision ID 141700, Chlorine
Region 2
Arroyo Las Positas
LOE ID:
282147
Pollutant:
Chlorine
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2016 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Chlorine, Total Residual.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
Line of Evidence (LOE) for Decision ID 141700, Chlorine
Region 2
Arroyo Las Positas
LOE ID:
282149
Pollutant:
Chlorine
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2014 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Chlorine, Total Residual.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
Line of Evidence (LOE) for Decision ID 141700, Chlorine
Region 2
Arroyo Las Positas
LOE ID:
282149
Pollutant:
Chlorine
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2014 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Chlorine, Total Residual.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
Line of Evidence (LOE) for Decision ID 141700, Chlorine
Region 2
Arroyo Las Positas
LOE ID:
282276
Pollutant:
Chlorine
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
1
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2012 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 1 of 1 samples exceeded the water quality threshold for Chlorine, Total Residual.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
Line of Evidence (LOE) for Decision ID 141700, Chlorine
Region 2
Arroyo Las Positas
LOE ID:
282374
Pollutant:
Chlorine
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
1
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring/records/region_2/2021/ref5527.pdf" >Creek Status Monitoring Program
Quality Assurance Project Plan
Line of Evidence (LOE) for Decision ID 141700, Chlorine
Region 2
Arroyo Las Positas
LOE ID:
282276
Pollutant:
Chlorine
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
1
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2012 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 1 of 1 samples exceeded the water quality threshold for Chlorine, Total Residual.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
Line of Evidence (LOE) for Decision ID 141700, Chlorine
Region 2
Arroyo Las Positas
LOE ID:
282374
Pollutant:
Chlorine
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
1
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2020 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 1 of 1 samples exceeded the water quality threshold for Chlorine, Total Residual.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
Line of Evidence (LOE) for Decision ID 141700, Chlorine
Region 2
Arroyo Las Positas
LOE ID:
282029
Pollutant:
Chlorine
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2015 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Chlorine, Total Residual.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
Line of Evidence (LOE) for Decision ID 141700, Chlorine
Region 2
Arroyo Las Positas
LOE ID:
282029
Pollutant:
Chlorine
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2015 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Chlorine, Total Residual.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
Line of Evidence (LOE) for Decision ID 141700, Chlorine
Region 2
Arroyo Las Positas
LOE ID:
282604
Pollutant:
Chlorine
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
1
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2014 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 1 of 1 samples exceeded the water quality threshold for Chlorine, Total Residual.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
Line of Evidence (LOE) for Decision ID 141700, Chlorine
Region 2
Arroyo Las Positas
LOE ID:
282604
Pollutant:
Chlorine
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
1
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2014 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 1 of 1 samples exceeded the water quality threshold for Chlorine, Total Residual.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
Line of Evidence (LOE) for Decision ID 141700, Chlorine
Region 2
Arroyo Las Positas
LOE ID:
282522
Pollutant:
Chlorine
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2019 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Chlorine, Total Residual.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
Line of Evidence (LOE) for Decision ID 141700, Chlorine
Region 2
Arroyo Las Positas
LOE ID:
282184
Pollutant:
Chlorine
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
1
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2017 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 1 of 1 samples exceeded the water quality threshold for Chlorine, Total Residual.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
Line of Evidence (LOE) for Decision ID 141700, Chlorine
Region 2
Arroyo Las Positas
LOE ID:
282715
Pollutant:
Chlorine
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2018 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Chlorine, Total Residual.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
Line of Evidence (LOE) for Decision ID 141700, Chlorine
Region 2
Arroyo Las Positas
LOE ID:
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2019 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Chlorine, Total Residual.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
Line of Evidence (LOE) for Decision ID 141700, Chlorine
Region 2
Arroyo Las Positas
LOE ID:
282184
Pollutant:
Chlorine
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
1
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2017 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 1 of 1 samples exceeded the water quality threshold for Chlorine, Total Residual.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
Line of Evidence (LOE) for Decision ID 141700, Chlorine
Region 2
Arroyo Las Positas
LOE ID:
282715
Pollutant:
Chlorine
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2018 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Chlorine, Total Residual.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
Line of Evidence (LOE) for Decision ID 141700, Chlorine
Region 2
Arroyo Las Positas
LOE ID:
282611
Pollutant:
Chlorine
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2019 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Chlorine, Total Residual.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
Line of Evidence (LOE) for Decision ID 141700, Chlorine
Region 2
Arroyo Las Positas
LOE ID:
282769
Pollutant:
Chlorine
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2015 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Chlorine, Total Residual.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
Line of Evidence (LOE) for Decision ID 141700, Chlorine
Region 2
Arroyo Las Positas
LOE ID:
282756
Pollutant:
Chlorine
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2016 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Chlorine, Total Residual.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
Line of Evidence (LOE) for Decision ID 141700, Chlorine
282611
Pollutant:
Chlorine
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2019 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Chlorine, Total Residual.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
Line of Evidence (LOE) for Decision ID 141700, Chlorine
Region 2
Arroyo Las Positas
LOE ID:
282769
Pollutant:
Chlorine
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2015 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Chlorine, Total Residual.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
Region 2
Arroyo Las Positas
LOE ID:
282843
Pollutant:
Chlorine
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2018 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Chlorine, Total Residual.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
Line of Evidence (LOE) for Decision ID 141700, Chlorine
Region 2
Arroyo Las Positas
LOE ID:
282504
Pollutant:
Chlorine
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
1
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2012 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 1 of 1 samples exceeded the water quality threshold for Chlorine, Total Residual.
Line of Evidence (LOE) for Decision ID 141700, Chlorine
Region 2
Arroyo Las Positas
LOE ID:
282756
Pollutant:
Chlorine
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2016 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Chlorine, Total Residual.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
Line of Evidence (LOE) for Decision ID 141700, Chlorine
Region 2
Arroyo Las Positas
LOE ID:
282843
Pollutant:
Chlorine
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2018 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Chlorine, Total Residual.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
Line of Evidence (LOE) for Decision ID 141700, Chlorine
Region 2
Arroyo Las Positas
LOE ID:
282504
Pollutant:
Chlorine
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
1
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2012 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 1 of 1 samples exceeded the water quality threshold for Chlorine, Total Residual.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
Line of Evidence (LOE) for Decision ID 141700, Chlorine
Region 2
Arroyo Las Positas
LOE ID:
282775
Pollutant:
Chlorine
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
1
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2017 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 1 of 1 samples exceeded the water quality threshold for Chlorine, Total Residual.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
Line of Evidence (LOE) for Decision ID 141700, Chlorine
Region 2
Arroyo Las Positas
LOE ID:
282789
Pollutant:
Chlorine
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
2
Number of Exceedances:
2
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2014 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 2 of 2 samples exceeded the water quality threshold for Chlorine, Total Residual.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
Line of Evidence (LOE) for Decision ID 141700, Chlorine
Region 2
Arroyo Las Positas
LOE ID:
282614
Pollutant:
Chlorine
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
1
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
SWAMP Data:
Non-SWAMP
Water Quality Objective/Criterion:
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
Line of Evidence (LOE) for Decision ID 141700, Chlorine
Region 2
Arroyo Las Positas
LOE ID:
282775
Pollutant:
Chlorine
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
1
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2017 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 1 of 1 samples exceeded the water quality threshold for Chlorine, Total Residual.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
The samples were collected at 1 monitoring site: 204R03481 (Altamont Creek upstream of Springtown).
Temporal Representation:
The samples were collected between the dates of 2017-05-25 and 2017-05-25
Environmental Conditions:
QAPP Information:
EOA, Inc., Applied Marine Sciences, Armand Ruby Consulting . 2016. BASMAA Regional Monitoring Coalition Creek Status and Pesticides & Toxicity Monitoring Quality Assurance Project Plan.
QAPP Informatiod align="left" valign="top" width="33%">Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2020 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 1 of 1 samples exceeded the water quality threshold for Chlorine, Total Residual.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
Line of Evidence (LOE) for Decision ID 141700, Chlorine
Region 2
Arroyo Las Positas
LOE ID:
282806
Pollutant:
Chlorine
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2019 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Chlorine, Total Residual.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
Line of Evidence (LOE) for Decision ID 141700, Chlorine
Region 2
Arroyo Las Positas
LOE ID:
282789
Pollutant:
Chlorine
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
2
Number of Exceedances:
2
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2014 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 2 of 2 samples exceeded the water quality threshold for Chlorine, Total Residual.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
Line of Evidence (LOE) for Decision ID 141700, Chlorine
Region 2
Arroyo Las Positas
LOE ID:
281892
Pollutant:
Chlorine
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
2
Number of Exceedances:
2
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2014 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 2 of 2 samples exceeded the water quality threshold for Chlorine, Total Residual.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
Line of Evidence (LOE) for Decision ID 141700, Chlorine
Region 2
Arroyo Las Positas
LOE ID:
282675
Pollutant:
Chlorine
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
d align="left" valign="top" width="33%">Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2020 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 1 of 1 samples exceeded the water quality threshold for Chlorine, Total Residual.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
Line of Evidence (LOE) for Decision ID 141700, Chlorine
Region 2
Arroyo Las Positas
LOE ID:
282806
Pollutant:
Chlorine
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2019 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Chlorine, Total Residual.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
The samples were collected at 1 monitoring site: 204R040
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2019 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Chlorine, Total Residual.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
Line of Evidence (LOE) for Decision ID 141700, Chlorine
Region 2
Arroyo Las Positas
LOE ID:
282298
Pollutant:
Chlorine
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2017 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Chlorine, Total Residual.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
The USEPA recommended chlorine criterion for the protection of aquatic ife in freshwater is 11 ug/L (4-day av31 (Arroyo Las Positas 300m upstream of El Charro Rd.).
Temporal Representation:
The samples were collected between the dates of 2019-05-15 and 2019-05-15
Environmental Conditions:
QAPP Information:
EOA, Inc.. 2014. Creek Status Monitoring Program Quality Assurance Project Plan.
Line of Evidence (LOE) for Decision ID 141700, Chlorine
Region 2
Arroyo Las Positas
LOE ID:
281892
Pollutant:
Chlorine
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
2
Number of Exceedances:
2
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2014 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 2 of 2 samples exceeded the water quality threshold for Chlorine, Total Residual.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
Line of Evidence (LOE) for Decision ID 141700, Chlorine
Region 2
Arroyo Las Positas
LOE ID:
282412
Pollutant:
Chlorine
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
1
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2012 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 1 of 1 samples exceeded the water quality threshold for Chlorine, Total Residual.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
Line of Evidence (LOE) for Decision ID 141700, Chlorine
Region 2
Arroyo Las Positas
LOE ID:
282765
Pollutant:
Chlorine
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2017 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Chlorine, Total Residual.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
Line of Evidence (LOE) for Decision ID 141700, Chlorine
Region 2
Arroyo Las Positas
LOE ID:
282772
Pollutant:
Chlorine
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2019 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Chlorine, Total Residual.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
Line of Evidence (LOE) for Decision ID 141700, Chlorine
Region 2
Arroyo Las Positas
LOE ID:
282028
Pollutant:
Chlorine
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
1
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2014 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 1 of 1 samples exceeded the water quality threshold for Chlorine, Total Residual.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
Water Board staff assessed BASMAA RMC Monitoring in WY2019 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Chlorine, Total Residual.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
Line of Evidence (LOE) for Decision ID 141700, Chlorine
Region 2
Arroyo Las Positas
LOE ID:
282298
Pollutant:
Chlorine
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2017 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Chlorine, Total Residual.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
The USEPA recommended chlorine criterion for the protection of aquatic ife in freshwater is 11 ug/L (4-day av
DECISION ID
141701
Region 2
Arroyo Las Positas
Pollutant:
Chlorophyll-a
Final Listing Decision:
Do Not List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:
New Decision
Revision Status
Revised
Impairment from Pollutant or Pollution:
Pollutant
Regional Board Conclusion:
Insufficient information is available to determine beneficial use support for this waterbody-pollutant combination with the statistical power and confidence required by the Listing Policy. Beneficial use support will be reassessed in a future cycle, if more data are available.
Regional Board Decision Recommendation:
After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list. The readily available data and information is insufficient to determine, with the power and confidence of the Listing Policy, the applicable beneficial use support rating.
State Board Review of Regional Board Conclusion and Recommendation:
State Board Decision Recommendation:
After review of this Regional Board decision, SWRCB staff recommend the decision be approved by the State Board.
Listing Extent:
Line of Evidence (LOE) for Decision ID 141701, Chlorophyll-a
Region 2
Arroyo Las Positas
LOE ID:
282872
Pollutant:
Chlorophyll-a
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
2
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed SWAMP RWB2 Monitoring data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 2 samples exceeded the water quality threshold for Chlorophyll a.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
North Carolina Administrative code (NCAC), Title 15A – Environmental and Natural Resources, Subchapter 2B-Surface water and wetland standards, Rule 0211-Fresh surface water quality standards for class C waters (Class C is defined as freshwaters protected for secondary recreation, fishing, aquatic life including propagation and survival, and wildlife).Section 3(a) of Rule 0211 applies to all fresh serage).
Line of Evidence (LOE) for Decision ID 141700, Chlorine
Region 2
Arroyo Las Positas
LOE ID:
282412
Pollutant:
Chlorine
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
1
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2012 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 1 of 1 samples exceeded the water quality threshold for Chlorine, Total Residual.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
Line of Evidence (LOE) for Decision ID 141700, Chlorine
Region 2
Arroyo Las Positas
LOE ID:
282765
Pollutant:
Chlorine
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2017 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Chlorine, Total Residual.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
Line of Evidence (LOE) for Decision ID 141700, Chlorine
Region 2
Arroyo Las Positas
LOE ID:
282772
Pollutant:
Chlorine
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2019 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Chlorine, Total Residual.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
Line of Evidence (LOE) for Decision ID 141700, Chlorine
Region 2
Arroyo Las Positas
LOE ID:
282028
Pollutant:
Chlorine
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
1
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2014 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 1 of 1 samples exceeded the water quality threshold for Chlorine, Total Residual.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
Line of Evidence (LOE) for Decision ID 141701, Chlorophyll-a
Region 2
Arroyo Las Positas
LOE ID:
282983
Pollutant:
Chlorophyll-a
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed SWAMP RWB2 Monitoring data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Chlorophyll a.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
North Carolina Administrative code (NCAC), Title 15A – Environmental and Natural Resources, Subchapter 2B-Surface water and wetland standards, Rule 0211-Fresh surface water quality standards for class C waters (Class C is defined as freshwaters protected for secondary recreation, fishing, aquatic life including propagation and survival, and wildlife).Section 3(a) of Rule 0211 applies to all fresh surface waters and states that chlorophyll a is not to exceed 40 ug/L.
Insufficient information is available to determine beneficial use support for this waterbody-pollutant combination with the statistical power and confidence required by the Listing Policy. Beneficial use support will be reassessed in a future cycle, if more data are available.
Regional Board Decision Recommendation:
After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list. The readily available data and information is insufficient to determine, with the power and confidence of the Listing Policy, the applicable beneficial use support rating.
State Board Review of Regional Board Conclusion and Recommendation:
State Board Decision Recommendation:
After review of this Regional Board decision, SWRCB staff recommend the decision be approved by the State Board.
Listing Extent:
Line of Evidence (LOE) for Decision ID 141701, Chlorophyll-a
Region 2
Arroyo Las Positas
LOE ID:
282872
Pollutant:
Chlorophyll-a
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
2
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed SWAMP RWB2 Monitoring data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 2 samples exceeded the water quality threshold for Chlorophyll a.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
North Carolina Administrative code (NCAC), Title 15A – Environmental and Natural Resources, Subchapter 2B-Surface water and wetland standards, Rule 0211-Fresh surface water quality standards for class C waters (Class C is defined as freshwaters protected for secondary recreation, fishing, aquatic life including propagation and survival, and wildlife).Section 3(a) of Rule 0211 applies to all fresh sNG-TOP: 3px; font-smooth: always">Line of Evidence (LOE) for Decision ID 141701, Chlorophyll-a
Region 2
Arroyo Las Positas
LOE ID:
282990
Pollutant:
Chlorophyll-a
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed SWAMP RWB2 Monitoring data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Chlorophyll a.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
North Carolina Administrative code (NCAC), Title 15A – Environmental and Natural Resources, Subchapter 2B-Surface water and wetland standards, Rule 0211-Fresh surface water quality standards for class C waters (Class C is defined as freshwaters protected for secondary recreation, fishing, aquatic life including propagation and survival, and wildlife).Section 3(a) of Rule 0211 applies to all fresh surface waters and states that chlorophyll a is not to exceed 40 ug/L.
Line of Evidence (LOE) for Decision ID 141701, Chlorophyll-a
Region 2
Arroyo Las Positas
LOE ID:
282983
Pollutant:
Chlorophyll-a
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed SWAMP RWB2 Monitoring data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Chlorophyll a.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
North Carolina Administrative code (NCAC), Title 15A – Environmental and Natural Resources, Subchapter 2B-Surface water and wetland standards, Rule 0211-Fresh surface water quality standards for class C waters (Class C is defined as freshwaters protected for secondary recreation, fishing, aquatic life including propagation and survival, and wildlife).Section 3(a) of Rule 0211 applies to all fresh surface waters and states that chlorophyll a is not to exceed 40 ug/L.
Water Board staff assessed SWAMP RWB2 Monitoring data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 2 samples exceeded the water quality threshold for Chlorophyll a.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
North Carolina Administrative code (NCAC), Title 15A – Environmental and Natural Resources, Subchapter 2B-Surface water and wetland standards, Rule 0211-Fresh surface water quality standards for class C waters (Class C is defined as freshwaters protected for secondary recreation, fishing, aquatic life including propagation and survival, and wildlife).Section 3(a) of Rule 0211 applies to all fresh surface waters and states that chlorophyll a is not to exceed 40 ug/L.
Line of Evidence (LOE) for Decision ID 141701, Chlorophyll-a
Region 2
Arroyo Las Positas
LOE ID:
282989
Pollutant:
Chlorophyll-a
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed SWAMP RWB2 Monitoring data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Chlorophyll a.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
North Carolina Administrative code (NCAC), Title 15A – Environmental and Natural Resources, Subchapter 2B-Surface water and wetland standards, Rule 0211-Fresh surface water quality standards for class C waters (Class C is defined as freshwaters protected for secondary recreation, fishing,NG-TOP: 3px; font-smooth: always">Line of Evidence (LOE) for Decision ID 141701, Chlorophyll-a
Region 2
Arroyo Las Positas
LOE ID:
282990
Pollutant:
Chlorophyll-a
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed SWAMP RWB2 Monitoring data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Chlorophyll a.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
North Carolina Administrative code (NCAC), Title 15A – Environmental and Natural Resources, Subchapter 2B-Surface water and wetland standards, Rule 0211-Fresh surface water quality standards for class C waters (Class C is defined as freshwaters protected for secondary recreation, fishing, aquatic life including propagation and survival, and wildlife).Section 3(a) of Rule 0211 applies to all fresh surface waters and states that chlorophyll a is not to exceed 40 ug/L.
Line of Evidence (LOE) for Decision ID 141701, Chlorophyll-a
Region 2
Arroyo Las Positas
LOE ID:
282942
Pollutant:
Chlorophyll-a
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed SWAMP RWB2 Monitoring data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Chlorophyll a.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
North Carolina Administrative code (NCAC), Title 15A – Environmental and Natural Resources, Subchapter 2B-Surface water and wetland standards, Rule 0211-Fresh surface water quality standards for class C waters (Class C is defined as freshwaters protected for secondary recreation, fishing, aquatic life including propagation and survival, and wildlife).Section 3(a) of Rule 0211 applies to all fresh surface waters and states that chlorophyll a is not to exceed 40 ug/L.
Water Board staff assessed SWAMP RWB2 Monitoring data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 2 samples exceeded the water quality threshold for Chlorophyll a.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
North Carolina Administrative code (NCAC), Title 15A – Environmental and Natural Resources, Subchapter 2B-Surface water and wetland standards, Rule 0211-Fresh surface water quality standards for class C waters (Class C is defined as freshwaters protected for secondary recreation, fishing, aquatic life including propagation and survival, and wildlife).Section 3(a) of Rule 0211 applies to all fresh surface waters and states that chlorophyll a is not to exceed 40 ug/L.
Line of Evidence (LOE) for Decision ID 141701, Chlorophyll-a
Region 2
Arroyo Las Positas
LOE ID:
282989
Pollutant:
Chlorophyll-a
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed SWAMP RWB2 Monitoring data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Chlorophyll a.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
North Carolina Administrative code (NCAC), Title 15A – Environmental and Natural Resources, Subchapter 2B-Surface water and wetland standards, Rule 0211-Fresh surface water quality standards for class C waters (Class C is defined as freshwaters protected for secondary recreation, fishing,
DECISION ID
141702
Region 2
Arroyo Las Positas
Pollutant:
Chlorpyrifos
Final Listing Decision:
Do Not List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:
New Decision
Revision Status
Revised
Impairment from Pollutant or Pollution:
Pollutant
Regional Board Conclusion:
Insufficient information is available to determine beneficial use support for this waterbody-pollutant combination with the statistical power and confidence required by the Listing Policy. Beneficial use support will be reassessed in a future cycle, if more data are available.
Regional Board Decision Recommendation:
After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list. The readily available data and information is insufficient to determine, with the power and confidence of the Listing Policy, the applicable beneficial use support rating.
State Board Review of Regional Board Conclusion and Recommendation:
State Board Decision Recommendation:
After review of this Regional Board decision, SWRCB staff recommend the decision be approved by the State Board.
Listing Extent:
Line of Evidence (LOE) for Decision ID 141702, Chlorpyrifos
Region 2
Arroyo Las Positas
LOE ID:
290161
Pollutant:
Chlorpyrifos
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
None
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
The Arroyo Las Positas Creek watershed was monitored as part of SWAMP assessment. Neither sample exceeded the water quality objectives for Chlorpyrifos, Dacthal, diazinon, disulfoton, endosulfan, Lindane/gamma Hexachlorocyclohexane (gamma-HCH), methyl parathion, thiobencarb.
All waters shall be maintained free of toxic substances that are lethal to or that produce other detrimental responses in aquatic organisms. There shall be no chronic toxicity in ambient waters. Chronic toxicity is a detrimental biological effect on growth rate, reproduction, fertilization success, larval development, population abundance, community composition, or any other relevant measure of the health of an organism, population, or community.Diazinon water quality objective, 0.1 ug/L (acute)
aquatic life including propagation and survival, and wildlife).Section 3(a) of Rule 0211 applies to all fresh surface waters and states that chlorophyll a is not to exceed 40 ug/L.
Line of Evidence (LOE) for Decision ID 141701, Chlorophyll-a
Region 2
Arroyo Las Positas
LOE ID:
282942
Pollutant:
Chlorophyll-a
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed SWAMP RWB2 Monitoring data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Chlorophyll a.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
North Carolina Administrative code (NCAC), Title 15A – Environmental and Natural Resources, Subchapter 2B-Surface water and wetland standards, Rule 0211-Fresh surface water quality standards for class C waters (Class C is defined as freshwaters protected for secondary recreation, fishing, aquatic life including propagation and survival, and wildlife).Section 3(a) of Rule 0211 applies to all fresh surface waters and states that chlorophyll a is not to exceed 40 ug/L.
Insufficient information is available to determine beneficial use support for this waterbody-pollutant combination with the statistical power and confidence required by the Listing Policy. Beneficial use support will be reassessed in a future cycle, if more data are available.
Regional Board Decision Recommendation:
After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list. The readily available data and information is insufficient to determine, with the power and confidence of the Listing Policy, the applicable beneficial use support rating.
State Board Review of Regional Board Conclusion and Recommendation:
State Board Decision Recommendation:
After review of this Regional Board decision, SWRCB staff recommend the decision be approved by the State Board.
Listing Extent:
Line of Evidence (LOE) for Decision ID 141702, Chlorpyrifos
Region 2
Arroyo Las Positas
LOE ID:
290161
Pollutant:
Chlorpyrifos
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
None
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
The Arroyo Las Positas Creek watershed was monitored as part of SWAMP assessment. Neither sample exceeded the water quality objectives for Chlorpyrifos, Dacthal, diazinon, disulfoton, endosulfan, Lindane/gamma Hexachlorocyclohexane (gamma-HCH), methyl parathion, thiobencarb.
All waters shall be maintained free of toxic substances that are lethal to or that produce other detrimental responses in aquatic organisms. There shall be no chronic toxicity in ambient waters. Chronic toxicity is a detrimental biological effect on growth rate, reproduction, fertilization success, larval development, population abundance, community composition, or any other relevant measure of the health of an organism, population, or community.Diazinon water quality objective, 0.1 ug/L (acute)
Do Not List on 303(d) list (TMDL required list)(2018)
Revision Status
Revised
Impairment from Pollutant or Pollution:
Pollutant
Regional Board Conclusion:
Insufficient information is available to determine beneficial use support for this waterbody-pollutant combination with the statistical power and confidence required by the Listing Policy. Beneficial use support will be reassessed in a future cycle, if more data are available
Regional Board Decision Recommendation:
After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list. The readily available data and information is insufficient to determine, with the power and confidence of the Listing Policy, the applicable beneficial use support rating.
State Board Review of Regional Board Conclusion and Recommendation:
State Board Decision Recommendation:
After review of the available data and information, SWRCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list because it cannot be determined if applicable water quality standards are not being exceeded.
Listing Extent:
Line of Evidence (LOE) for Decision ID 141731, Chromium
Region 2
Arroyo Las Positas
LOE ID:
283316
Pollutant:
Chromium
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Dissolved
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed SWAMP RWB2 Monitoring data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Chromium.
The dissolved chromium (III) criterion continuous concentration (expressed as a 4-day average) to protect aquatic life in freshwater is is hardness dependent as described in Table 1 of paragraph (b)(1). The value calculated when using a default hardness of 100 mg/L is 180 ug/L (California Toxics Rule, 2000).
Do Not List on 303(d) list (TMDL required list)(2018)
Revision Status
Revised
Impairment from Pollutant or Pollution:
Pollutant
Regional Board Conclusion:
Insufficient information is available to determine beneficial use support for this waterbody-pollutant combination with the statistical power and confidence required by the Listing Policy. Beneficial use support will be reassessed in a future cycle, if more data are available
Regional Board Decision Recommendation:
After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list. The readily available data and information is insufficient to determine, with the power and confidence of the Listing Policy, the applicable beneficial use support rating.
State Board Review of Regional Board Conclusion and Recommendation:
State Board Decision Recommendation:
After review of the available data and information, SWRCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list because it cannot be determined if applicable water quality standards are not being exceeded.
Listing Extent:
Line of Evidence (LOE) for Decision ID 141731, Chromium
Region 2
Arroyo Las Positas
LOE ID:
283316
Pollutant:
Chromium
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Dissolved
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed SWAMP RWB2 Monitoring data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Chromium.
The dissolved chromium (III) criterion continuous concentration (expressed as a 4-day average) to protect aquatic life in freshwater is is hardness dependent as described in Table 1 of paragraph (b)(1). The value calculated when using a default hardness of 100 mg/L is 180 ug/L (California Toxics Rule, 2000).
Line of Evidence (LOE) for Decision ID 141731, Chromium
Region 2
Arroyo Las Positas
LOE ID:
290143
Pollutant:
Chromium
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Dissolved
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
6
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
The Arroyo Las Positas Creek watershed was monitored as part of SWAMP assessment. None of the six samples exceeded the water quality objectives for arsenic, chromium VI, copper, lead, nickel, silver and zinc.Concentrations of total dissolved chromium were well below the objective for chromium VI.
All waters shall be maintained free of toxic substances that are lethal to or that produce other detrimental responses in aquatic organisms. Table 3-4 in the Basin Plan (2007) lists freshwater water quality objectives for toxic pollutants: arsenic- 150 ug/L, chromium VI- 11 ug/L, copper - 9.0 ug/L, lead - 2.5 ug/L; nickel - 52 ug/L, silver-3.4 ug/L and zinc - 120 ug/L.
Data were collected at three sampling locations on Arroyo Las Positas Creek - ALP010 (El Charro), ALP100 (Altamont Creek), and ALP110 (Arroyo Las Positas).
Temporal Representation:
Samples were collected at all three sites during spring and dry seasons of the 2001-2002 sampling season.
Environmental Conditions:
QAPP Information:
All samples were collected and analyzed using procedures comparable with the SWAMP Quality Assurance Management Plan (SWRCB, 2002).
One sediment sample was collected at a "watershed integrator" site located close to the mouth of Arroyo Las Positas watershed at El Charro. The PEC was exceeded for chromium, with a sample concentration of 133 mg/kg dw.
Temporal Representation:
Sediment sample was collected in September of 2001.
Environmental Conditions:
QAPP Information:
All samples were collected and analyzed using procedures comparable with the SWAMP Quality Assurance Management Plan (SWRCB, 2002).
QAPP Information Reference(s):
Line of Evidence (LOE) for Decision ID 141731, Chromium
Region 2
Arroyo Las Positas
LOE ID:
283210
Pollutant:
Chromium
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Dissolved
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed SWAMP RWB2 Monitoring data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Chromium.
The dissolved chromium (III) criterion continuous concentration (expressed as a 4-day average) to protect aquatic life in freshwater is is hardness dependent as described in Table 1 of paragraph (b)(1). The value calculated when using a default hardness of 100 mg/L is 180 ug/L (California Toxics Rule, 2000).
Line of Evidence (LOE) for Decision ID 141731, Chromium
Region 2
Arroyo Las Positas
LOE ID:
290143
Pollutant:
Chromium
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Dissolved
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
6
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
The Arroyo Las Positas Creek watershed was monitored as part of SWAMP assessment. None of the six samples exceeded the water quality objectives for arsenic, chromium VI, copper, lead, nickel, silver and zinc.Concentrations of total dissolved chromium were well below the objective for chromium VI.
All waters shall be maintained free of toxic substances that are lethal to or that produce other detrimental responses in aquatic organisms. Table 3-4 in the Basin Plan (2007) lists freshwater water quality objectives for toxic pollutants: arsenic- 150 ug/L, chromium VI- 11 ug/L, copper - 9.0 ug/L, lead - 2.5 ug/L; nickel - 52 ug/L, silver-3.4 ug/L and zinc - 120 ug/L.
Data were collected at three sampling locations on Arroyo Las Positas Creek - ALP010 (El Charro), ALP100 (Altamont Creek), and ALP110 (Arroyo Las Positas).
Temporal Representation:
Samples were collected at all three sites during spring and dry seasons of the 2001-2002 sampling season.
Environmental Conditions:
QAPP Information:
All samples were collected and analyzed using procedures comparable with the SWAMP Quality Assurance Management Plan (SWRCB, 2002).
One sediment sample was collected at a "watershed integrator" site located close to the mouth of Arroyo Las Positas watershed at El Charro. The PEC was exceeded for chromium, with a sample concentration of 133 mg/kg dw.
Temporal Representation:
Sediment sample was collected in September of 2001.
Environmental Conditions:
QAPP Information:
All samples were collected and analyzed using procedures comparable with the SWAMP Quality Assurance Management Plan (SWRCB, 2002).
QAPP Information Reference(s):
Line of Evidence (LOE) for Decision ID 141731, Chromium
Region 2
Arroyo Las Positas
LOE ID:
283210
Pollutant:
Chromium
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Dissolved
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed SWAMP RWB2 Monitoring data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Chromium.
The dissolved chromium (III) criterion continuous concentration (expressed as a 4-day average) to protect aquatic life in freshwater is is hardness dependent as described in Table 1 of paragraph (b)(1). The value calculated when using a default hardness of 100 mg/L is 180 ug/L (California Toxics Rule, 2000).
Insufficient information is available to determine beneficial use support for this waterbody-pollutant combination with the statistical power and confidence required by the Listing Policy. Beneficial use support will be reassessed in a future cycle, if more data are available.
Regional Board Decision Recommendation:
After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list. The readily available data and information is insufficient to determine, with the power and confidence of the Listing Policy, the applicable beneficial use support rating.
State Board Review of Regional Board Conclusion and Recommendation:
State Board Decision Recommendation:
After review of the available data and information, SWRCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list because it cannot be determined if applicable water quality standards are not being exceeded.
Listing Extent:
Line of Evidence (LOE) for Decision ID 141703, Chrysene (C1-C4)
Region 2
Arroyo Las Positas
LOE ID:
290041
Pollutant:
Chrysene (C1-C4)
LOE Subgroup:
Pollutant-Sediment
Matrix:
Sediment
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Concentrations of Anthracene, fluorene, napthalene, phenanthrene, benz(a)anthracene, benzo(a)pyrene, chrysene, fluoranthrene, pyrene, PAH (total), PCB (total), chlordane, dieldrin, DDD/DDE/DDT, endrin, heptachlor epoxide, and HCH, gamma in one sediment sample collected in spring 2005 did not exceed the sediment quality guidelines.
Insufficient information is available to determine beneficial use support for this waterbody-pollutant combination with the statistical power and confidence required by the Listing Policy. Beneficial use support will be reassessed in a future cycle, if more data are available.
Regional Board Decision Recommendation:
After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list. The readily available data and information is insufficient to determine, with the power and confidence of the Listing Policy, the applicable beneficial use support rating.
State Board Review of Regional Board Conclusion and Recommendation:
State Board Decision Recommendation:
After review of the available data and information, SWRCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list because it cannot be determined if applicable water quality standards are not being exceeded.
Listing Extent:
Line of Evidence (LOE) for Decision ID 141703, Chrysene (C1-C4)
Region 2
Arroyo Las Positas
LOE ID:
290041
Pollutant:
Chrysene (C1-C4)
LOE Subgroup:
Pollutant-Sediment
Matrix:
Sediment
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Concentrations of Anthracene, fluorene, napthalene, phenanthrene, benz(a)anthracene, benzo(a)pyrene, chrysene, fluoranthrene, pyrene, PAH (total), PCB (total), chlordane, dieldrin, DDD/DDE/DDT, endrin, heptachlor epoxide, and HCH, gamma in one sediment sample collected in spring 2005 did not exceed the sediment quality guidelines.
Insufficient information is available to determine beneficial use support for this waterbody-pollutant combination with the statistical power and confidence required by the Listing Policy. Beneficial use support will be reassessed in a future cycle, if more data are available.
Regional Board Decision Recommendation:
After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list. The readily available data and information is insufficient to determine, with the power and confidence of the Listing Policy, the applicable beneficial use support rating.
State Board Review of Regional Board Conclusion and Recommendation:
State Board Decision Recommendation:
After review of this Regional Board decision, SWRCB staff recommend the decision be approved by the State Board.
Listing Extent:
Line of Evidence (LOE) for Decision ID 141704, Copper
Region 2
Arroyo Las Positas
LOE ID:
283205
Pollutant:
Copper
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Dissolved
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
3
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2019 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 3 samples exceeded the water quality threshold for Copper.
The dissolved copper criterion continuous concentration (expressed as a 4-day average) to protect aquatic life in freshwater is hardness dependent. The criterion when calculated using a default hardness of 100 mg/L is 9 ug/L (California Toxics Rule, 2000).
The samples were collected at 1 monitoring site: 204R04031 (Arro
DECISION ID
141704
Region 2
Arroyo Las Positas
Pollutant:
Copper
Final Listing Decision:
Do Not List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:
New Decision
Revision Status
Revised
Impairment from Pollutant or Pollution:
Pollutant
Regional Board Conclusion:
Insufficient information is available to determine beneficial use support for this waterbody-pollutant combination with the statistical power and confidence required by the Listing Policy. Beneficial use support will be reassessed in a future cycle, if more data are available.
Regional Board Decision Recommendation:
After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list. The readily available data and information is insufficient to determine, with the power and confidence of the Listing Policy, the applicable beneficial use support rating.
State Board Review of Regional Board Conclusion and Recommendation:
State Board Decision Recommendation:
After review of this Regional Board decision, SWRCB staff recommend the decision be approved by the State Board.
Listing Extent:
Line of Evidence (LOE) for Decision ID 141704, Copper
Region 2
Arroyo Las Positas
LOE ID:
283205
Pollutant:
Copper
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Dissolved
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
3
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2019 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 3 samples exceeded the water quality threshold for Copper.
The dissolved copper criterion continuous concentration (expressed as a 4-day average) to protect aquatic life in freshwater is hardness dependent. The criterion when calculated using a default hardness of 100 mg/L is 9 ug/L (California Toxics Rule, 2000).
Line of Evidence (LOE) for Decision ID 141704, Copper
Region 2
Arroyo Las Positas
LOE ID:
283373
Pollutant:
Copper
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Dissolved
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
3
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2019 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 3 samples exceeded the water quality threshold for Copper.
The dissolved copper criterion continuous concentration (expressed as a 4-day average) to protect aquatic life in freshwater is hardness dependent. The criterion when calculated using a default hardness of 100 mg/L is 9 ug/L (California Toxics Rule, 2000).
Line of Evidence (LOE) for Decision ID 141704, Copper
Region 2
Arroyo Las Positas
LOE ID:
283373
Pollutant:
Copper
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Dissolved
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
3
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2019 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 3 samples exceeded the water quality threshold for Copper.
The dissolved copper criterion continuous concentration (expressed as a 4-day average) to protect aquatic life in freshwater is hardness dependent. The criterion when calculated using a default hardness of 100 mg/L is 9 ug/L (California Toxics Rule, 2000).
Line of Evidence (LOE) for Decision ID 141704, Copper
Region 2
Arroyo Las Positas
LOE ID:
290144
Pollutant:
Copper
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Dissolved
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
6
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
The Arroyo Las Positas Creek watershed was monitored as part of SWAMP assessment. None of the six samples exceeded the water quality objectives for arsenic, chromium VI, copper, lead, nickel, silver and zinc.Concentrations of total dissolved chromium were well below the objective for chromium VI.
All waters shall be maintained free of toxic substances that are lethal to or that produce other detrimental responses in aquatic organisms. Table 3-4 in the Basin Plan (2007) lists freshwater water quality objectives for toxic pollutants: arsenic- 150 ug/L, chromium VI- 11 ug/L, copper - 9.0 ug/L, lead - 2.5 ug/L; nickel - 52 ug/L, silver-3.4 ug/L and zinc - 120 ug/L.
Data were collected at three sampling locations on Arroyo Las Positas Creek - ALP010 (El Charro), ALP100 (Altamont Creek), and ALP110 (Arroyo Las Positas).
Temporal Representation:
Samples were collected at all three sites during spring and dry seasons of the 2001-2002 sampling season.
Environmental Conditions:
QAPP Information:
All samples were collected and analyzed using procedures comparable with the SWAMP Quality Assurance Management Plan (SWRCB, 2002).
Line of Evidence (LOE) for Decision ID 141704, Copper
Region 2
Arroyo Las Positas
LOE ID:
290128
Pollutant:
Copper
LOE Subgroup:
Pollutant-Sediment
Matrix:
Sediment
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Concentrations of arsenic, cadmium, copper, lead, mercury and zinc in one sediment sample collected in spring 2005 did not exceed the sediment quality guidelines.
The Arroyo Las Positas Creek watershed was monitored as part of SWAMP assessment. None of the six samples exceeded the water quality objectives for arsenic, chromium VI, copper, lead, nickel, silver and zinc.Concentrations of total dissolved chromium were well below the objective for chromium VI.
All waters shall be maintained free of toxic substances that are lethal to or that produce other detrimental responses in aquatic organisms. Table 3-4 in the Basin Plan (2007) lists freshwater water quality objectives for toxic pollutants: arsenic- 150 ug/L, chromium VI- 11 ug/L, copper - 9.0 ug/L, lead - 2.5 ug/L; nickel - 52 ug/L, silver-3.4 ug/L and zinc - 120 ug/L.
Data were collected at three sampling locations on Arroyo Las Positas Creek - ALP010 (El Charro), ALP100 (Altamont Creek), and ALP110 (Arroyo Las Positas).
Temporal Representation:
Samples were collected at all three sites during spring and dry seasons of the 2001-2002 sampling season.
Environmental Conditions:
QAPP Information:
All samples were collected and analyzed using procedures comparable with the SWAMP Quality Assurance Management Plan (SWRCB, 2002).
Line of Evidence (LOE) for Decision ID 141704, Copper
Region 2
Arroyo Las Positas
LOE ID:
290128
Pollutant:
Copper
LOE Subgroup:
Pollutant-Sediment
Matrix:
Sediment
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Concentrations of arsenic, cadmium, copper, lead, mercury and zinc in one sediment sample collected in spring 2005 did not exceed the sediment quality guidelines.
Line of Evidence (LOE) for Decision ID 141704, Copper
Region 2
Arroyo Las Positas
LOE ID:
283176
Pollutant:
Copper
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Dissolved
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
3
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2019 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 3 samples exceeded the water quality threshold for Copper.
The dissolved copper criterion continuous concentration (expressed as a 4-day average) to protect aquatic life in freshwater is hardness dependent. The criterion when calculated using a default hardness of 100 mg/L is 9 ug/L (California Toxics Rule, 2000).
Line of Evidence (LOE) for Decision ID 141704, Copper
Region 2
Arroyo Las Positas
LOE ID:
283176
Pollutant:
Copper
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Dissolved
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
3
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2019 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 3 samples exceeded the water quality threshold for Copper.
The dissolved copper criterion continuous concentration (expressed as a 4-day average) to protect aquatic life in freshwater is hardness dependent. The criterion when calculated using a default hardness of 100 mg/L is 9 ug/L (California Toxics Rule, 2000).
Line of Evidence (LOE) for Decision ID 141704, Copper
Region 2
Arroyo Las Positas
LOE ID:
283439
Pollutant:
Copper
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Dissolved
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed SWAMP RWB2 Monitoring data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Copper.
The dissolved copper criterion continuous concentration (expressed as a 4-day average) to protect aquatic life in freshwater is hardness dependent. The criterion when calculated using a default hardness of 100 mg/L is 9 ug/L (California Toxics Rule, 2000).
Line of Evidence (LOE) for Decision ID 141704, Copper
Region 2
Arroyo Las Positas
LOE ID:
283375
Pollutant:
Copper
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Dissolved
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
3
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2019 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 3 samples exceeded the water quality threshold for Copper.
The dissolved copper criterion continuous concentration (expressed as a 4-day average) to protect aquatic life in freshwater is hardness dependent. The criterion when calculated using a default hardness of 100 mg/L is 9 ug/L (California Toxics Rule, 2000).
Line of Evidence (LOE) for Decision ID 141704, Copper
Region 2
Arroyo Las Positas
LOE ID:
283131
Pollutant:
Copper
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Dissolved
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed SWAMP RWB2 Monitoring data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Copper.
The dissolved copper criterion continuous concentration (expressed as a 4-day average) to protect aquatic life in freshwater is hardness dependent. The criterion when calculated using a default hardness of 100 mg/L is 9 ug/L (California Toxics Rule, 2000).
Water Board staff assessed SWAMP RWB2 Monitoring data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Copper.
The dissolved copper criterion continuous concentration (expressed as a 4-day average) to protect aquatic life in freshwater is hardness dependent. The criterion when calculated using a default hardness of 100 mg/L is 9 ug/L (California Toxics Rule, 2000).
Line of Evidence (LOE) for Decision ID 141704, Copper
Region 2
Arroyo Las Positas
LOE ID:
283375
Pollutant:
Copper
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Dissolved
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
3
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2019 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 3 samples exceeded the water quality threshold for Copper.
The dissolved copper criterion continuous concentration (expressed as a 4-day average) to protect aquatic life in freshwater is hardness dependent. The criterion when calculated using a default hardness of 100 mg/L is 9 ug/L (California Toxics Rule, 2000).
Line of Evidence (LOE) for Decision ID 141704, Copper
Region 2
Arroyo Las Positas
LOE ID:
283131
Pollutant:
Copper
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Dissolved
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed SWAMP RWB2 Monitoring data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Copper.
The dissolved copper criterion continuous concentration (expressed as a 4-day average) to protect aquatic life in freshwater is hardness dependent. The criterion when calculated using a default hardness of 100 mg/L is 9 ug/L (California Toxics Rule, 2000).
Insufficient information is available to determine beneficial use support for this waterbody-pollutant combination with the statistical power and confidence required by the Listing Policy. Beneficial use support will be reassessed in a future cycle, if more data are available.
Regional Board Decision Recommendation:
After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list. The readily available data and information is insufficient to determine, with the power and confidence of the Listing Policy, the applicable beneficial use support rating.
State Board Review of Regional Board Conclusion and Recommendation:
State Board Decision Recommendation:
After review of this Regional Board decision, SWRCB staff recommend the decision be approved by the State Board.
Listing Extent:
Line of Evidence (LOE) for Decision ID 145709, DDD (Dichlorodiphenyldichloroethane)
Region 2
Arroyo Las Positas
LOE ID:
290052
Pollutant:
DDD (Dichlorodiphenyldichloroethane)
LOE Subgroup:
Pollutant-Sediment
Matrix:
Sediment
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Concentrations of Anthracene, fluorene, napthalene, phenanthrene, benz(a)anthracene, benzo(a)pyrene, chrysene, fluoranthrene, pyrene, PAH (total), PCB (total), chlordane, dieldrin, DDD/DDE/DDT, endrin, heptachlor epoxide, and HCH, gamma in one sediment sample collected in spring 2005 did not exceed the sediment quality guidelines.
Insufficient information is available to determine beneficial use support for this waterbody-pollutant combination with the statistical power and confidence required by the Listing Policy. Beneficial use support will be reassessed in a future cycle, if more data are available.
Regional Board Decision Recommendation:
After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list. The readily available data and information is insufficient to determine, with the power and confidence of the Listing Policy, the applicable beneficial use support rating.
State Board Review of Regional Board Conclusion and Recommendation:
State Board Decision Recommendation:
After review of this Regional Board decision, SWRCB staff recommend the decision be approved by the State Board.
Listing Extent:
Line of Evidence (LOE) for Decision ID 145709, DDD (Dichlorodiphenyldichloroethane)
Region 2
Arroyo Las Positas
LOE ID:
290052
Pollutant:
DDD (Dichlorodiphenyldichloroethane)
LOE Subgroup:
Pollutant-Sediment
Matrix:
Sediment
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Concentrations of Anthracene, fluorene, napthalene, phenanthrene, benz(a)anthracene, benzo(a)pyrene, chrysene, fluoranthrene, pyrene, PAH (total), PCB (total), chlordane, dieldrin, DDD/DDE/DDT, endrin, heptachlor epoxide, and HCH, gamma in one sediment sample collected in spring 2005 did not exceed the sediment quality guidelines.
Insufficient information is available to determine beneficial use support for this waterbody-pollutant combination with the statistical power and confidence required by the Listing Policy. Beneficial use support will be reassessed in a future cycle, if more data are available.
Regional Board Decision Recommendation:
After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list. The readily available data and information is insufficient to determine, with the power and confidence of the Listing Policy, the applicable beneficial use support rating.
State Board Review of Regional Board Conclusion and Recommendation:
State Board Decision Recommendation:
After review of this Regional Board decision, SWRCB staff recommend the decision be approved by the State Board.
Listing Extent:
Line of Evidence (LOE) for Decision ID 148159, DDE (Dichlorodiphenyldichloroethylene)
Region 2
Arroyo Las Positas
LOE ID:
290053
Pollutant:
DDE (Dichlorodiphenyldichloroethylene)
LOE Subgroup:
Pollutant-Sediment
Matrix:
Sediment
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Concentrations of Anthracene, fluorene, napthalene, phenanthrene, benz(a)anthracene, benzo(a)pyrene, chrysene, fluoranthrene, pyrene, PAH (total), PCB (total), chlordane, dieldrin, DDD/DDE/DDT, endrin, heptachlor epoxide, and HCH, gamma in one sediment sample collected in spring 2005 did not exceed the sediment quality guidelines.
Insufficient information is available to determine beneficial use support for this waterbody-pollutant combination with the statistical power and confidence required by the Listing Policy. Beneficial use support will be reassessed in a future cycle, if more data are available.
Regional Board Decision Recommendation:
After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list. The readily available data and information is insufficient to determine, with the power and confidence of the Listing Policy, the applicable beneficial use support rating.
State Board Review of Regional Board Conclusion and Recommendation:
State Board Decision Recommendation:
After review of this Regional Board decision, SWRCB staff recommend the decision be approved by the State Board.
Listing Extent:
Line of Evidence (LOE) for Decision ID 148159, DDE (Dichlorodiphenyldichloroethylene)
Region 2
Arroyo Las Positas
LOE ID:
290053
Pollutant:
DDE (Dichlorodiphenyldichloroethylene)
LOE Subgroup:
Pollutant-Sediment
Matrix:
Sediment
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Concentrations of Anthracene, fluorene, napthalene, phenanthrene, benz(a)anthracene, benzo(a)pyrene, chrysene, fluoranthrene, pyrene, PAH (total), PCB (total), chlordane, dieldrin, DDD/DDE/DDT, endrin, heptachlor epoxide, and HCH, gamma in one sediment sample collected in spring 2005 did not exceed the sediment quality guidelines.
Insufficient information is available to determine beneficial use support for this waterbody-pollutant combination with the statistical power and confidence required by the Listing Policy. Beneficial use support will be reassessed in a future cycle, if more data are available.
Regional Board Decision Recommendation:
After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list. The readily available data and information is insufficient to determine, with the power and confidence of the Listing Policy, the applicable beneficial use support rating.
State Board Review of Regional Board Conclusion and Recommendation:
State Board Decision Recommendation:
After review of this Regional Board decision, SWRCB staff recommend the decision be approved by the State Board.
Listing Extent:
Line of Evidence (LOE) for Decision ID 148242, DDT (Dichlorodiphenyltrichloroethane)
Region 2
Arroyo Las Positas
LOE ID:
290054
Pollutant:
DDT (Dichlorodiphenyltrichloroethane)
LOE Subgroup:
Pollutant-Sediment
Matrix:
Sediment
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Concentrations of Anthracene, fluorene, napthalene, phenanthrene, benz(a)anthracene, benzo(a)pyrene, chrysene, fluoranthrene, pyrene, PAH (total), PCB (total), chlordane, dieldrin, DDD/DDE/DDT, endrin, heptachlor epoxide, and HCH, gamma in one sediment sample collected in spring 2005 did not exceed the sediment quality guidelines.
Insufficient information is available to determine beneficial use support for this waterbody-pollutant combination with the statistical power and confidence required by the Listing Policy. Beneficial use support will be reassessed in a future cycle, if more data are available.
Regional Board Decision Recommendation:
After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list. The readily available data and information is insufficient to determine, with the power and confidence of the Listing Policy, the applicable beneficial use support rating.
State Board Review of Regional Board Conclusion and Recommendation:
State Board Decision Recommendation:
After review of this Regional Board decision, SWRCB staff recommend the decision be approved by the State Board.
Listing Extent:
Line of Evidence (LOE) for Decision ID 148242, DDT (Dichlorodiphenyltrichloroethane)
Region 2
Arroyo Las Positas
LOE ID:
290054
Pollutant:
DDT (Dichlorodiphenyltrichloroethane)
LOE Subgroup:
Pollutant-Sediment
Matrix:
Sediment
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Concentrations of Anthracene, fluorene, napthalene, phenanthrene, benz(a)anthracene, benzo(a)pyrene, chrysene, fluoranthrene, pyrene, PAH (total), PCB (total), chlordane, dieldrin, DDD/DDE/DDT, endrin, heptachlor epoxide, and HCH, gamma in one sediment sample collected in spring 2005 did not exceed the sediment quality guidelines.
Insufficient information is available to determine beneficial use support for this waterbody-pollutant combination with the statistical power and confidence required by the Listing Policy. Beneficial use support will be reassessed in a future cycle, if more data are available.
Regional Board Decision Recommendation:
After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list. The readily available data and information is insufficient to determine, with the power and confidence of the Listing Policy, the applicable beneficial use support rating.
State Board Review of Regional Board Conclusion and Recommendation:
State Board Decision Recommendation:
After review of this Regional Board decision, SWRCB staff recommend the decision be approved by the State Board.
Listing Extent:
Line of Evidence (LOE) for Decision ID 141705, Dacthal
Region 2
Arroyo Las Positas
LOE ID:
290162
Pollutant:
Dacthal
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
None
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
The Arroyo Las Positas Creek watershed was monitored as part of SWAMP assessment. Neither sample exceeded the water quality objectives for Chlorpyrifos, Dacthal, diazinon, disulfoton, endosulfan, Lindane/gamma Hexachlorocyclohexane (gamma-HCH), methyl parathion, thiobencarb.
All waters shall be maintained free of toxic substances that are lethal to or that produce other detrimental responses in aquatic organisms. There shall be no chronic toxicity in ambient waters. Chronic toxicity is a detrimental biological effect on growth rate, reproduction, fertilization success, larval development, population abundance, community composition, or any other relevant measure of the health of an organism, population, or community.Diazinon water quality objective, 0.1 ug/L (acute)
Insufficient information is available to determine beneficial use support for this waterbody-pollutant combination with the statistical power and confidence required by the Listing Policy. Beneficial use support will be reassessed in a future cycle, if more data are available.
Regional Board Decision Recommendation:
After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list. The readily available data and information is insufficient to determine, with the power and confidence of the Listing Policy, the applicable beneficial use support rating.
State Board Review of Regional Board Conclusion and Recommendation:
State Board Decision Recommendation:
After review of this Regional Board decision, SWRCB staff recommend the decision be approved by the State Board.
Listing Extent:
Line of Evidence (LOE) for Decision ID 141705, Dacthal
Region 2
Arroyo Las Positas
LOE ID:
290162
Pollutant:
Dacthal
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
None
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
The Arroyo Las Positas Creek watershed was monitored as part of SWAMP assessment. Neither sample exceeded the water quality objectives for Chlorpyrifos, Dacthal, diazinon, disulfoton, endosulfan, Lindane/gamma Hexachlorocyclohexane (gamma-HCH), methyl parathion, thiobencarb.
All waters shall be maintained free of toxic substances that are lethal to or that produce other detrimental responses in aquatic organisms. There shall be no chronic toxicity in ambient waters. Chronic toxicity is a detrimental biological effect on growth rate, reproduction, fertilization success, larval development, population abundance, community composition, or any other relevant measure of the health of an organism, population, or community.Diazinon water quality objective, 0.1 ug/L (acute)
Insufficient information is available to determine beneficial use support for this waterbody-pollutant combination with the statistical power and confidence required by the Listing Policy. Beneficial use support will be reassessed in a future cycle, if more data are available.
Regional Board Decision Recommendation:
After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list. The readily available data and information is insufficient to determine, with the power and confidence of the Listing Policy, the applicable beneficial use support rating.
State Board Review of Regional Board Conclusion and Recommendation:
State Board Decision Recommendation:
After review of the available data and information, SWRCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list because it cannot be determined if applicable water quality standards are not being exceeded.
Listing Extent:
Line of Evidence (LOE) for Decision ID 141707, Dieldrin
Region 2
Arroyo Las Positas
LOE ID:
290065
Pollutant:
Dieldrin
LOE Subgroup:
Pollutant-Sediment
Matrix:
Sediment
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Concentrations of Anthracene, fluorene, napthalene, phenanthrene, benz(a)anthracene, benzo(a)pyrene, chrysene, fluoranthrene, pyrene, PAH (total), PCB (total), chlordane, dieldrin, DDD/DDE/DDT, endrin, heptachlor epoxide, and HCH, gamma in one sediment sample collected in spring 2005 did not exceed the sediment quality guidelines.
Insufficient information is available to determine beneficial use support for this waterbody-pollutant combination with the statistical power and confidence required by the Listing Policy. Beneficial use support will be reassessed in a future cycle, if more data are available.
Regional Board Decision Recommendation:
After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list. The readily available data and information is insufficient to determine, with the power and confidence of the Listing Policy, the applicable beneficial use support rating.
State Board Review of Regional Board Conclusion and Recommendation:
State Board Decision Recommendation:
After review of the available data and information, SWRCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list because it cannot be determined if applicable water quality standards are not being exceeded.
Listing Extent:
Line of Evidence (LOE) for Decision ID 141707, Dieldrin
Region 2
Arroyo Las Positas
LOE ID:
290065
Pollutant:
Dieldrin
LOE Subgroup:
Pollutant-Sediment
Matrix:
Sediment
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Concentrations of Anthracene, fluorene, napthalene, phenanthrene, benz(a)anthracene, benzo(a)pyrene, chrysene, fluoranthrene, pyrene, PAH (total), PCB (total), chlordane, dieldrin, DDD/DDE/DDT, endrin, heptachlor epoxide, and HCH, gamma in one sediment sample collected in spring 2005 did not exceed the sediment quality guidelines.
Insufficient information is available to determine beneficial use support for this waterbody-pollutant combination with the statistical power and confidence required by the Listing Policy. Beneficial use support will be reassessed in a future cycle, if more data are available.
Regional Board Decision Recommendation:
After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list. The readily available data and information is insufficient to determine, with the power and confidence of the Listing Policy, the applicable beneficial use support rating.
State Board Review of Regional Board Conclusion and Recommendation:
State Board Decision Recommendation:
After review of this Regional Board decision, SWRCB staff recommend the decision be approved by the State Board.
Listing Extent:
Line of Evidence (LOE) for Decision ID 141708, Disulfoton
Region 2
Arroyo Las Positas
LOE ID:
290174
Pollutant:
Disulfoton
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
None
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
The Arroyo Las Positas Creek watershed was monitored as part of SWAMP assessment. Neither sample exceeded the water quality objectives for Chlorpyrifos, Dacthal, diazinon, disulfoton, endosulfan, Lindane/gamma Hexachlorocyclohexane (gamma-HCH), methyl parathion, thiobencarb.
All waters shall be maintained free of toxic substances that are lethal to or that produce other detrimental responses in aquatic organisms. There shall be no chronic toxicity in ambient waters. Chronic toxicity is a detrimental biological effect on growth rate, reproduction, fertilization success, larval development, population abundance, community composition, or any other relevant measure of the health of an organism, population, or community.Diazinon water quality objective, 0.1 ug/L (acute)
Insufficient information is available to determine beneficial use support for this waterbody-pollutant combination with the statistical power and confidence required by the Listing Policy. Beneficial use support will be reassessed in a future cycle, if more data are available.
Regional Board Decision Recommendation:
After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list. The readily available data and information is insufficient to determine, with the power and confidence of the Listing Policy, the applicable beneficial use support rating.
State Board Review of Regional Board Conclusion and Recommendation:
State Board Decision Recommendation:
After review of this Regional Board decision, SWRCB staff recommend the decision be approved by the State Board.
Listing Extent:
Line of Evidence (LOE) for Decision ID 141708, Disulfoton
Region 2
Arroyo Las Positas
LOE ID:
290174
Pollutant:
Disulfoton
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
None
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
The Arroyo Las Positas Creek watershed was monitored as part of SWAMP assessment. Neither sample exceeded the water quality objectives for Chlorpyrifos, Dacthal, diazinon, disulfoton, endosulfan, Lindane/gamma Hexachlorocyclohexane (gamma-HCH), methyl parathion, thiobencarb.
All waters shall be maintained free of toxic substances that are lethal to or that produce other detrimental responses in aquatic organisms. There shall be no chronic toxicity in ambient waters. Chronic toxicity is a detrimental biological effect on growth rate, reproduction, fertilization success, larval development, population abundance, community composition, or any other relevant measure of the health of an organism, population, or community.Diazinon water quality objective, 0.1 ug/L (acute)
Insufficient information is available to determine beneficial use support for this waterbody-pollutant combination with the statistical power and confidence required by the Listing Policy. Beneficial use support will be reassessed in a future cycle, if more data are available.
Regional Board Decision Recommendation:
After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list. The readily available data and information is insufficient to determine, with the power and confidence of the Listing Policy, the applicable beneficial use support rating.
State Board Review of Regional Board Conclusion and Recommendation:
State Board Decision Recommendation:
After review of this Regional Board decision, SWRCB staff recommend the decision be approved by the State Board.
Listing Extent:
Line of Evidence (LOE) for Decision ID 141709, Endosulfan
Region 2
Arroyo Las Positas
LOE ID:
290175
Pollutant:
Endosulfan
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
None
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
The Arroyo Las Positas Creek watershed was monitored as part of SWAMP assessment. Neither sample exceeded the water quality objectives for Chlorpyrifos, Dacthal, diazinon, disulfoton, endosulfan, Lindane/gamma Hexachlorocyclohexane (gamma-HCH), methyl parathion, thiobencarb.
All waters shall be maintained free of toxic substances that are lethal to or that produce other detrimental responses in aquatic organisms. There shall be no chronic toxicity in ambient waters. Chronic toxicity is a detrimental biological effect on growth rate, reproduction, fertilization success, larval development, population abundance, community composition, or any other relevant measure of the health of an organism, population, or community.Diazinon water quality objective, 0.1 ug/L (acute)
Insufficient information is available to determine beneficial use support for this waterbody-pollutant combination with the statistical power and confidence required by the Listing Policy. Beneficial use support will be reassessed in a future cycle, if more data are available.
Regional Board Decision Recommendation:
After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list. The readily available data and information is insufficient to determine, with the power and confidence of the Listing Policy, the applicable beneficial use support rating.
State Board Review of Regional Board Conclusion and Recommendation:
State Board Decision Recommendation:
After review of this Regional Board decision, SWRCB staff recommend the decision be approved by the State Board.
Listing Extent:
Line of Evidence (LOE) for Decision ID 141709, Endosulfan
Region 2
Arroyo Las Positas
LOE ID:
290175
Pollutant:
Endosulfan
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
None
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
The Arroyo Las Positas Creek watershed was monitored as part of SWAMP assessment. Neither sample exceeded the water quality objectives for Chlorpyrifos, Dacthal, diazinon, disulfoton, endosulfan, Lindane/gamma Hexachlorocyclohexane (gamma-HCH), methyl parathion, thiobencarb.
All waters shall be maintained free of toxic substances that are lethal to or that produce other detrimental responses in aquatic organisms. There shall be no chronic toxicity in ambient waters. Chronic toxicity is a detrimental biological effect on growth rate, reproduction, fertilization success, larval development, population abundance, community composition, or any other relevant measure of the health of an organism, population, or community.Diazinon water quality objective, 0.1 ug/L (acute)
Insufficient information is available to determine beneficial use support for this waterbody-pollutant combination with the statistical power and confidence required by the Listing Policy. Beneficial use support will be reassessed in a future cycle, if more data are available.
Regional Board Decision Recommendation:
After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list. The readily available data and information is insufficient to determine, with the power and confidence of the Listing Policy, the applicable beneficial use support rating.
State Board Review of Regional Board Conclusion and Recommendation:
State Board Decision Recommendation:
After review of the available data and information, SWRCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list because it cannot be determined if applicable water quality standards are not being exceeded.
Listing Extent:
Line of Evidence (LOE) for Decision ID 141710, Endrin
Region 2
Arroyo Las Positas
LOE ID:
290066
Pollutant:
Endrin
LOE Subgroup:
Pollutant-Sediment
Matrix:
Sediment
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Concentrations of Anthracene, fluorene, napthalene, phenanthrene, benz(a)anthracene, benzo(a)pyrene, chrysene, fluoranthrene, pyrene, PAH (total), PCB (total), chlordane, dieldrin, DDD/DDE/DDT, endrin, heptachlor epoxide, and HCH, gamma in one sediment sample collected in spring 2005 did not exceed the sediment quality guidelines.
Insufficient information is available to determine beneficial use support for this waterbody-pollutant combination with the statistical power and confidence required by the Listing Policy. Beneficial use support will be reassessed in a future cycle, if more data are available.
Regional Board Decision Recommendation:
After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list. The readily available data and information is insufficient to determine, with the power and confidence of the Listing Policy, the applicable beneficial use support rating.
State Board Review of Regional Board Conclusion and Recommendation:
State Board Decision Recommendation:
After review of the available data and information, SWRCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list because it cannot be determined if applicable water quality standards are not being exceeded.
Listing Extent:
Line of Evidence (LOE) for Decision ID 141710, Endrin
Region 2
Arroyo Las Positas
LOE ID:
290066
Pollutant:
Endrin
LOE Subgroup:
Pollutant-Sediment
Matrix:
Sediment
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Concentrations of Anthracene, fluorene, napthalene, phenanthrene, benz(a)anthracene, benzo(a)pyrene, chrysene, fluoranthrene, pyrene, PAH (total), PCB (total), chlordane, dieldrin, DDD/DDE/DDT, endrin, heptachlor epoxide, and HCH, gamma in one sediment sample collected in spring 2005 did not exceed the sediment quality guidelines.
Insufficient information is available to determine beneficial use support for this waterbody-pollutant combination with the statistical power and confidence required by the Listing Policy. Beneficial use support will be reassessed in a future cycle, if more data are available.
Regional Board Decision Recommendation:
After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list. The readily available data and information is insufficient to determine, with the power and confidence of the Listing Policy, the applicable beneficial use support rating.
State Board Review of Regional Board Conclusion and Recommendation:
State Board Decision Recommendation:
After review of the available data and information, SWRCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list because it cannot be determined if applicable water quality standards are not being exceeded.
Listing Extent:
Line of Evidence (LOE) for Decision ID 141711, Fluoranthene
Region 2
Arroyo Las Positas
LOE ID:
290067
Pollutant:
Fluoranthene
LOE Subgroup:
Pollutant-Sediment
Matrix:
Sediment
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Concentrations of Anthracene, fluorene, napthalene, phenanthrene, benz(a)anthracene, benzo(a)pyrene, chrysene, fluoranthrene, pyrene, PAH (total), PCB (total), chlordane, dieldrin, DDD/DDE/DDT, endrin, heptachlor epoxide, and HCH, gamma in one sediment sample collected in spring 2005 did not exceed the sediment quality guidelines.
Insufficient information is available to determine beneficial use support for this waterbody-pollutant combination with the statistical power and confidence required by the Listing Policy. Beneficial use support will be reassessed in a future cycle, if more data are available.
Regional Board Decision Recommendation:
After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list. The readily available data and information is insufficient to determine, with the power and confidence of the Listing Policy, the applicable beneficial use support rating.
State Board Review of Regional Board Conclusion and Recommendation:
State Board Decision Recommendation:
After review of the available data and information, SWRCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list because it cannot be determined if applicable water quality standards are not being exceeded.
Listing Extent:
Line of Evidence (LOE) for Decision ID 141711, Fluoranthene
Region 2
Arroyo Las Positas
LOE ID:
290067
Pollutant:
Fluoranthene
LOE Subgroup:
Pollutant-Sediment
Matrix:
Sediment
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Concentrations of Anthracene, fluorene, napthalene, phenanthrene, benz(a)anthracene, benzo(a)pyrene, chrysene, fluoranthrene, pyrene, PAH (total), PCB (total), chlordane, dieldrin, DDD/DDE/DDT, endrin, heptachlor epoxide, and HCH, gamma in one sediment sample collected in spring 2005 did not exceed the sediment quality guidelines.
Insufficient information is available to determine beneficial use support for this waterbody-pollutant combination with the statistical power and confidence required by the Listing Policy. Beneficial use support will be reassessed in a future cycle, if more data are available.
Regional Board Decision Recommendation:
After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list. The readily available data and information is insufficient to determine, with the power and confidence of the Listing Policy, the applicable beneficial use support rating.
State Board Review of Regional Board Conclusion and Recommendation:
State Board Decision Recommendation:
After review of the available data and information, SWRCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list because it cannot be determined if applicable water quality standards are not being exceeded.
Listing Extent:
Line of Evidence (LOE) for Decision ID 141712, Fluorene
Region 2
Arroyo Las Positas
LOE ID:
290079
Pollutant:
Fluorene
LOE Subgroup:
Pollutant-Sediment
Matrix:
Sediment
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Concentrations of Anthracene, fluorene, napthalene, phenanthrene, benz(a)anthracene, benzo(a)pyrene, chrysene, fluoranthrene, pyrene, PAH (total), PCB (total), chlordane, dieldrin, DDD/DDE/DDT, endrin, heptachlor epoxide, and HCH, gamma in one sediment sample collected in spring 2005 did not exceed the sediment quality guidelines.
Insufficient information is available to determine beneficial use support for this waterbody-pollutant combination with the statistical power and confidence required by the Listing Policy. Beneficial use support will be reassessed in a future cycle, if more data are available.
Regional Board Decision Recommendation:
After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list. The readily available data and information is insufficient to determine, with the power and confidence of the Listing Policy, the applicable beneficial use support rating.
State Board Review of Regional Board Conclusion and Recommendation:
State Board Decision Recommendation:
After review of the available data and information, SWRCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list because it cannot be determined if applicable water quality standards are not being exceeded.
Listing Extent:
Line of Evidence (LOE) for Decision ID 141712, Fluorene
Region 2
Arroyo Las Positas
LOE ID:
290079
Pollutant:
Fluorene
LOE Subgroup:
Pollutant-Sediment
Matrix:
Sediment
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Concentrations of Anthracene, fluorene, napthalene, phenanthrene, benz(a)anthracene, benzo(a)pyrene, chrysene, fluoranthrene, pyrene, PAH (total), PCB (total), chlordane, dieldrin, DDD/DDE/DDT, endrin, heptachlor epoxide, and HCH, gamma in one sediment sample collected in spring 2005 did not exceed the sediment quality guidelines.
Insufficient information is available to determine beneficial use support for this waterbody-pollutant combination with the statistical power and confidence required by the Listing Policy. Beneficial use support will be reassessed in a future cycle, if more data are available.
Regional Board Decision Recommendation:
After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list. The readily available data and information is insufficient to determine, with the power and confidence of the Listing Policy, the applicable beneficial use support rating.
State Board Review of Regional Board Conclusion and Recommendation:
State Board Decision Recommendation:
After review of the available data and information, SWRCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list because it cannot be determined if applicable water quality standards are not being exceeded.
Listing Extent:
Line of Evidence (LOE) for Decision ID 141713, Heptachlor epoxide
Region 2
Arroyo Las Positas
LOE ID:
290080
Pollutant:
Heptachlor epoxide
LOE Subgroup:
Pollutant-Sediment
Matrix:
Sediment
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Concentrations of Anthracene, fluorene, napthalene, phenanthrene, benz(a)anthracene, benzo(a)pyrene, chrysene, fluoranthrene, pyrene, PAH (total), PCB (total), chlordane, dieldrin, DDD/DDE/DDT, endrin, heptachlor epoxide, and HCH, gamma in one sediment sample collected in spring 2005 did not exceed the sediment quality guidelines.
Insufficient information is available to determine beneficial use support for this waterbody-pollutant combination with the statistical power and confidence required by the Listing Policy. Beneficial use support will be reassessed in a future cycle, if more data are available.
Regional Board Decision Recommendation:
After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list. The readily available data and information is insufficient to determine, with the power and confidence of the Listing Policy, the applicable beneficial use support rating.
State Board Review of Regional Board Conclusion and Recommendation:
State Board Decision Recommendation:
After review of the available data and information, SWRCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list because it cannot be determined if applicable water quality standards are not being exceeded.
Listing Extent:
Line of Evidence (LOE) for Decision ID 141713, Heptachlor epoxide
Region 2
Arroyo Las Positas
LOE ID:
290080
Pollutant:
Heptachlor epoxide
LOE Subgroup:
Pollutant-Sediment
Matrix:
Sediment
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Concentrations of Anthracene, fluorene, napthalene, phenanthrene, benz(a)anthracene, benzo(a)pyrene, chrysene, fluoranthrene, pyrene, PAH (total), PCB (total), chlordane, dieldrin, DDD/DDE/DDT, endrin, heptachlor epoxide, and HCH, gamma in one sediment sample collected in spring 2005 did not exceed the sediment quality guidelines.
Insufficient information is available to determine beneficial use support for this waterbody-pollutant combination with the statistical power and confidence required by the Listing Policy. Beneficial use support will be reassessed in a future cycle, if more data are available.
Regional Board Decision Recommendation:
After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list. The readily available data and information is insufficient to determine, with the power and confidence of the Listing Policy, the applicable beneficial use support rating.
State Board Review of Regional Board Conclusion and Recommendation:
State Board Decision Recommendation:
After review of this Regional Board decision, SWRCB staff recommend the decision be approved by the State Board.
Listing Extent:
Line of Evidence (LOE) for Decision ID 141714, Lead
Region 2
Arroyo Las Positas
LOE ID:
284332
Pollutant:
Lead
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Dissolved
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed SWAMP RWB2 Monitoring data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Lead.
The dissolved lead criterion continuous concentration (expressed as a 4-day average) to protect aquatic life in freshwater is hardness dependent. The criterion when calculated using a default hardness of 100 mg/L is 2.5 ug/L (California Toxics Rule, 2000).
The samples were collected at 1 monitoring site: 204ALP075 (Arroyo las Positas
DECISION ID
141714
Region 2
Arroyo Las Positas
Pollutant:
Lead
Final Listing Decision:
Do Not List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:
New Decision
Revision Status
Revised
Impairment from Pollutant or Pollution:
Pollutant
Regional Board Conclusion:
Insufficient information is available to determine beneficial use support for this waterbody-pollutant combination with the statistical power and confidence required by the Listing Policy. Beneficial use support will be reassessed in a future cycle, if more data are available.
Regional Board Decision Recommendation:
After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list. The readily available data and information is insufficient to determine, with the power and confidence of the Listing Policy, the applicable beneficial use support rating.
State Board Review of Regional Board Conclusion and Recommendation:
State Board Decision Recommendation:
After review of this Regional Board decision, SWRCB staff recommend the decision be approved by the State Board.
Listing Extent:
Line of Evidence (LOE) for Decision ID 141714, Lead
Region 2
Arroyo Las Positas
LOE ID:
284332
Pollutant:
Lead
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Dissolved
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed SWAMP RWB2 Monitoring data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Lead.
The dissolved lead criterion continuous concentration (expressed as a 4-day average) to protect aquatic life in freshwater is hardness dependent. The criterion when calculated using a default hardness of 100 mg/L is 2.5 ug/L (California Toxics Rule, 2000).
Line of Evidence (LOE) for Decision ID 141714, Lead
Region 2
Arroyo Las Positas
LOE ID:
290129
Pollutant:
Lead
LOE Subgroup:
Pollutant-Sediment
Matrix:
Sediment
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Concentrations of arsenic, cadmium, copper, lead, mercury and zinc in one sediment sample collected in spring 2005 did not exceed the sediment quality guidelines.
Line of Evidence (LOE) for Decision ID 141714, Lead
Region 2
Arroyo Las Positas
LOE ID:
290145
Pollutant:
Lead
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Dissolved
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
6
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
The Arroyo Las Positas Creek watershed was monitored as part of SWAMP assessment. None of the six samples exceeded the water quality objectives for arsenic, chromium VI, copper, lead, nickel, silver and zinc.Concentrations of total dissolved chromium were well below the objective for chromium VI.
All waters shall be maintained free of toxic substances that are lethal to or that produce other detrimental responses in aquatic organisms. Table 3-4 in the Basin Plan (2007) lists freshwater water quality objectives for toxic pollutants: arsenic- 150 ug/L, chromium VI- 11 ug/L, copper - 9.0 ug/L, lead - 2.5 ug/L; nickel - 52 ug/L, silver-3.4 ug/L and zinc - 120 ug/L.
Data were collected at three sampling locations on Arroyo Las Positas Creek - ALP010 (El Charro), ALP100 (Altamont Creek), and ALP110 (Arroyo Las Positas).
Temporal Representation:
Samples were collected at all three sites during spring and dry seasons of the 2001-2002 sampling season.
Environmental Conditions:
QAPP Information:
All samples were collected and analyzed using procedures comparable with the SWAMP Quality Assurance Management Plan (SWRCB, 2002).
Line of Evidence (LOE) for Decision ID 141714, Lead
Region 2
Arroyo Las Positas
LOE ID:
284289
Pollutant:
Lead
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Dissolved
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed SWAMP RWB2 Monitoring data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Lead.
The dissolved lead criterion continuous concentration (expressed as a 4-day average) to protect aquatic life in freshwater is hardness dependent. The criterion when calculated using a default hardness of 100 mg/L is 2.5 ug/L (California Toxics Rule, 2000).
Line of Evidence (LOE) for Decision ID 141714, Lead
Region 2
Arroyo Las Positas
LOE ID:
290129
Pollutant:
Lead
LOE Subgroup:
Pollutant-Sediment
Matrix:
Sediment
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Concentrations of arsenic, cadmium, copper, lead, mercury and zinc in one sediment sample collected in spring 2005 did not exceed the sediment quality guidelines.
Line of Evidence (LOE) for Decision ID 141714, Lead
Region 2
Arroyo Las Positas
LOE ID:
290145
Pollutant:
Lead
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Dissolved
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
6
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
The Arroyo Las Positas Creek watershed was monitored as part of SWAMP assessment. None of the six samples exceeded the water quality objectives for arsenic, chromium VI, copper, lead, nickel, silver and zinc.Concentrations of total dissolved chromium were well below the objective for chromium VI.
All waters shall be maintained free of toxic substances that are lethal to or that produce other detrimental responses in aquatic organisms. Table 3-4 in the Basin Plan (2007) lists freshwater water quality objectives for toxic pollutants: arsenic- 150 ug/L, chromium VI- 11 ug/L, copper - 9.0 ug/L, lead - 2.5 ug/L; nickel - 52 ug/L, silver-3.4 ug/L and zinc - 120 ug/L.
Data were collected at three sampling locations on Arroyo Las Positas Creek - ALP010 (El Charro), ALP100 (Altamont Creek), and ALP110 (Arroyo Las Positas).
Temporal Representation:
Samples were collected at all three sites during spring and dry seasons of the 2001-2002 sampling season.
Environmental Conditions:
QAPP Information:
All samples were collected and analyzed using procedures comparable with the SWAMP Quality Assurance Management Plan (SWRCB, 2002).
Line of Evidence (LOE) for Decision ID 141714, Lead
Region 2
Arroyo Las Positas
LOE ID:
284289
Pollutant:
Lead
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Dissolved
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed SWAMP RWB2 Monitoring data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Lead.
The dissolved lead criterion continuous concentration (expressed as a 4-day average) to protect aquatic life in freshwater is hardness dependent. The criterion when calculated using a default hardness of 100 mg/L is 2.5 ug/L (California Toxics Rule, 2000).
Insufficient information is available to determine beneficial use support for this waterbody-pollutant combination with the statistical power and confidence required by the Listing Policy. Beneficial use support will be reassessed in a future cycle, if more data are available.
Regional Board Decision Recommendation:
After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list. The readily available data and information is insufficient to determine, with the power and confidence of the Listing Policy, the applicable beneficial use support rating.
State Board Review of Regional Board Conclusion and Recommendation:
State Board Decision Recommendation:
After review of this Regional Board decision, SWRCB staff recommend the decision be approved by the State Board.
Listing Extent:
Line of Evidence (LOE) for Decision ID 141715, Lindane/gamma Hexachlorocyclohexane (gamma-HCH)
Region 2
Arroyo Las Positas
LOE ID:
290185
Pollutant:
Lindane/gamma Hexachlorocyclohexane (gamma-HCH)
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
None
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
The Arroyo Las Positas Creek watershed was monitored as part of SWAMP assessment. Neither sample exceeded the water quality objectives for Chlorpyrifos, Dacthal, diazinon, disulfoton, endosulfan, Lindane/gamma Hexachlorocyclohexane (gamma-HCH), methyl parathion, thiobencarb.
All waters shall be maintained free of toxic substances that are lethal to or that produce other detrimental responses in aquatic organisms. There shall be no chronic toxicity in ambient waters. Chronic toxicity is a detrimental biological effect on growth rate, reproduction, fertilization success, larval development, population abundance, community composition, or any other relevant measure of the health of an organism, population, or community.Diazinon water quality objective, 0.1 ug/L (acute)
Line of Evidence (LOE) for Decision ID 141715, Lindane/gamma Hexachlorocyclohexane (gamma-HCH)
Region 2
Arroyo Las Positas
LOE ID:
290081
Pollutant:
Lindane/gamma Hexachlorocyclohexane (gamma-HCH)
LOE Subgroup:
Pollutant-Sediment
Matrix:
Sediment
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Concentrations of Anthracene, fluorene, napthalene, phenanthrene, benz(a)anthracene, benzo(a)pyrene, chrysene, fluoranthrene, pyrene, PAH (total), PCB (total), chlordane, dieldrin, DDD/DDE/DDT, endrin, heptachlor epoxide, and HCH, gamma in one sediment sample collected in spring 2005 did not exceed the sediment quality guidelines.
Insufficient information is available to determine beneficial use support for this waterbody-pollutant combination with the statistical power and confidence required by the Listing Policy. Beneficial use support will be reassessed in a future cycle, if more data are available.
Regional Board Decision Recommendation:
After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list. The readily available data and information is insufficient to determine, with the power and confidence of the Listing Policy, the applicable beneficial use support rating.
State Board Review of Regional Board Conclusion and Recommendation:
State Board Decision Recommendation:
After review of this Regional Board decision, SWRCB staff recommend the decision be approved by the State Board.
Listing Extent:
Line of Evidence (LOE) for Decision ID 141715, Lindane/gamma Hexachlorocyclohexane (gamma-HCH)
Region 2
Arroyo Las Positas
LOE ID:
290185
Pollutant:
Lindane/gamma Hexachlorocyclohexane (gamma-HCH)
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
None
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
The Arroyo Las Positas Creek watershed was monitored as part of SWAMP assessment. Neither sample exceeded the water quality objectives for Chlorpyrifos, Dacthal, diazinon, disulfoton, endosulfan, Lindane/gamma Hexachlorocyclohexane (gamma-HCH), methyl parathion, thiobencarb.
All waters shall be maintained free of toxic substances that are lethal to or that produce other detrimental responses in aquatic organisms. There shall be no chronic toxicity in ambient waters. Chronic toxicity is a detrimental biological effect on growth rate, reproduction, fertilization success, larval development, population abundance, community composition, or any other relevant measure of the health of an organism, population, or community.Diazinon water quality objective, 0.1 ug/L (acute)
Line of Evidence (LOE) for Decision ID 141715, Lindane/gamma Hexachlorocyclohexane (gamma-HCH)
Region 2
Arroyo Las Positas
LOE ID:
290081
Pollutant:
Lindane/gamma Hexachlorocyclohexane (gamma-HCH)
LOE Subgroup:
Pollutant-Sediment
Matrix:
Sediment
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Concentrations of Anthracene, fluorene, napthalene, phenanthrene, benz(a)anthracene, benzo(a)pyrene, chrysene, fluoranthrene, pyrene, PAH (total), PCB (total), chlordane, dieldrin, DDD/DDE/DDT, endrin, heptachlor epoxide, and HCH, gamma in one sediment sample collected in spring 2005 did not exceed the sediment quality guidelines.
Insufficient information is available to determine beneficial use support for this waterbody-pollutant combination with the statistical power and confidence required by the Listing Policy. Beneficial use support will be reassessed in a future cycle, if more data are available.
Regional Board Decision Recommendation:
After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list. The readily available data and information is insufficient to determine, with the power and confidence of the Listing Policy, the applicable beneficial use support rating.
State Board Review of Regional Board Conclusion and Recommendation:
State Board Decision Recommendation:
After review of this Regional Board decision, SWRCB staff recommend the decision be approved by the State Board.
Listing Extent:
Line of Evidence (LOE) for Decision ID 145412, Mercury
Region 2
Arroyo Las Positas
LOE ID:
284717
Pollutant:
Mercury
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed SWAMP RWB2 Monitoring data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Mercury.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
National Recommended Water Quality Criteria Continuous Concentration (4-day average concentrations) for freshwater aquatic organisms exposure to total mercury is 0.77 ug/L.
Line of Evidence (LOE) for Decision ID 145412, Mercury
Region 2
Arroyo Las Positas
LOE ID:
290130
Pollutant:
Mercury
LOE Subgroup:
Pollutant-Sediment
Matrix:
Sediment
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Concentrations of arsenic, cadmium, copper, lead, mercury and zinc in one sediment sample collected in spring 2005 did not exceed the sediment quality guidelines.
Line of Evidence (LOE) for Decision ID 145412, Mercury
Region 2
Arroyo Las Positas
LOE ID:
284108
Pollutant:
Mercury
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed SWAMP RWB2 Monitoring data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Mercury.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
National Recommended Water Quality Criteria Continuous Concentration (4-day average concentrations) for freshwater aquatic organisms exposure to total mercury is 0.77 ug/L.
Insufficient information is available to determine beneficial use support for this waterbody-pollutant combination with the statistical power and confidence required by the Listing Policy. Beneficial use support will be reassessed in a future cycle, if more data are available.
Regional Board Decision Recommendation:
After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list. The readily available data and information is insufficient to determine, with the power and confidence of the Listing Policy, the applicable beneficial use support rating.
State Board Review of Regional Board Conclusion and Recommendation:
State Board Decision Recommendation:
After review of this Regional Board decision, SWRCB staff recommend the decision be approved by the State Board.
Listing Extent:
Line of Evidence (LOE) for Decision ID 145412, Mercury
Region 2
Arroyo Las Positas
LOE ID:
284717
Pollutant:
Mercury
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed SWAMP RWB2 Monitoring data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Mercury.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
National Recommended Water Quality Criteria Continuous Concentration (4-day average concentrations) for freshwater aquatic organisms exposure to total mercury is 0.77 ug/L.
Line of Evidence (LOE) for Decision ID 145412, Mercury
Region 2
Arroyo Las Positas
LOE ID:
290130
Pollutant:
Mercury
LOE Subgroup:
Pollutant-Sediment
Matrix:
Sediment
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Concentrations of arsenic, cadmium, copper, lead, mercury and zinc in one sediment sample collected in spring 2005 did not exceed the sediment quality guidelines.
Line of Evidence (LOE) for Decision ID 145412, Mercury
Region 2
Arroyo Las Positas
LOE ID:
284108
Pollutant:
Mercury
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed SWAMP RWB2 Monitoring data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Mercury.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
National Recommended Water Quality Criteria Continuous Concentration (4-day average concentrations) for freshwater aquatic organisms exposure to total mercury is 0.77 ug/L.
Insufficient information is available to determine beneficial use support for this waterbody-pollutant combination with the statistical power and confidence required by the Listing Policy. Beneficial use support will be reassessed in a future cycle, if more data are available.
Regional Board Decision Recommendation:
After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list. The readily available data and information is insufficient to determine, with the power and confidence of the Listing Policy, the applicable beneficial use support rating.
State Board Review of Regional Board Conclusion and Recommendation:
State Board Decision Recommendation:
After review of this Regional Board decision, SWRCB staff recommend the decision be approved by the State Board.
Listing Extent:
Line of Evidence (LOE) for Decision ID 141716, Methyl Parathion
Region 2
Arroyo Las Positas
LOE ID:
290186
Pollutant:
Methyl Parathion
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
None
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
The Arroyo Las Positas Creek watershed was monitored as part of SWAMP assessment. Neither sample exceeded the water quality objectives for Chlorpyrifos, Dacthal, diazinon, disulfoton, endosulfan, Lindane/gamma Hexachlorocyclohexane (gamma-HCH), methyl parathion, thiobencarb.
All waters shall be maintained free of toxic substances that are lethal to or that produce other detrimental responses in aquatic organisms. There shall be no chronic toxicity in ambient waters. Chronic toxicity is a detrimental biological effect on growth rate, reproduction, fertilization success, larval development, population abundance, community composition, or any other relevant measure of the health of an organism, population, or community.Diazinon water quality objective, 0.1 ug/L (acute)
Insufficient information is available to determine beneficial use support for this waterbody-pollutant combination with the statistical power and confidence required by the Listing Policy. Beneficial use support will be reassessed in a future cycle, if more data are available.
Regional Board Decision Recommendation:
After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list. The readily available data and information is insufficient to determine, with the power and confidence of the Listing Policy, the applicable beneficial use support rating.
State Board Review of Regional Board Conclusion and Recommendation:
State Board Decision Recommendation:
After review of this Regional Board decision, SWRCB staff recommend the decision be approved by the State Board.
Listing Extent:
Line of Evidence (LOE) for Decision ID 141716, Methyl Parathion
Region 2
Arroyo Las Positas
LOE ID:
290186
Pollutant:
Methyl Parathion
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
None
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
The Arroyo Las Positas Creek watershed was monitored as part of SWAMP assessment. Neither sample exceeded the water quality objectives for Chlorpyrifos, Dacthal, diazinon, disulfoton, endosulfan, Lindane/gamma Hexachlorocyclohexane (gamma-HCH), methyl parathion, thiobencarb.
All waters shall be maintained free of toxic substances that are lethal to or that produce other detrimental responses in aquatic organisms. There shall be no chronic toxicity in ambient waters. Chronic toxicity is a detrimental biological effect on growth rate, reproduction, fertilization success, larval development, population abundance, community composition, or any other relevant measure of the health of an organism, population, or community.Diazinon water quality objective, 0.1 ug/L (acute)
Insufficient information is available to determine beneficial use support for this waterbody-pollutant combination with the statistical power and confidence required by the Listing Policy. Beneficial use support will be reassessed in a future cycle, if more data are available.
Regional Board Decision Recommendation:
After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list. The readily available data and information is insufficient to determine, with the power and confidence of the Listing Policy, the applicable beneficial use support rating.
State Board Review of Regional Board Conclusion and Recommendation:
State Board Decision Recommendation:
After review of the available data and information, SWRCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list because it cannot be determined if applicable water quality standards are not being exceeded.
Listing Extent:
Line of Evidence (LOE) for Decision ID 141717, Naphthalene
Region 2
Arroyo Las Positas
LOE ID:
290096
Pollutant:
Naphthalene
LOE Subgroup:
Pollutant-Sediment
Matrix:
Sediment
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Concentrations of Anthracene, fluorene, napthalene, phenanthrene, benz(a)anthracene, benzo(a)pyrene, chrysene, fluoranthrene, pyrene, PAH (total), PCB (total), chlordane, dieldrin, DDD/DDE/DDT, endrin, heptachlor epoxide, and HCH, gamma in one sediment sample collected in spring 2005 did not exceed the sediment quality guidelines.
Insufficient information is available to determine beneficial use support for this waterbody-pollutant combination with the statistical power and confidence required by the Listing Policy. Beneficial use support will be reassessed in a future cycle, if more data are available.
Regional Board Decision Recommendation:
After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list. The readily available data and information is insufficient to determine, with the power and confidence of the Listing Policy, the applicable beneficial use support rating.
State Board Review of Regional Board Conclusion and Recommendation:
State Board Decision Recommendation:
After review of the available data and information, SWRCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list because it cannot be determined if applicable water quality standards are not being exceeded.
Listing Extent:
Line of Evidence (LOE) for Decision ID 141717, Naphthalene
Region 2
Arroyo Las Positas
LOE ID:
290096
Pollutant:
Naphthalene
LOE Subgroup:
Pollutant-Sediment
Matrix:
Sediment
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Concentrations of Anthracene, fluorene, napthalene, phenanthrene, benz(a)anthracene, benzo(a)pyrene, chrysene, fluoranthrene, pyrene, PAH (total), PCB (total), chlordane, dieldrin, DDD/DDE/DDT, endrin, heptachlor epoxide, and HCH, gamma in one sediment sample collected in spring 2005 did not exceed the sediment quality guidelines.
Do Not List on 303(d) list (TMDL required list)(2018)
Revision Status
Revised
Impairment from Pollutant or Pollution:
Pollutant
Regional Board Conclusion:
Insufficient information is available to determine beneficial use support for this waterbody-pollutant combination with the statistical power and confidence required by the Listing Policy. Beneficial use support will be reassessed in a future cycle, if more data are available
Regional Board Decision Recommendation:
After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list. The readily available data and information is insufficient to determine, with the power and confidence of the Listing Policy, the applicable beneficial use support rating.
State Board Review of Regional Board Conclusion and Recommendation:
State Board Decision Recommendation:
After review of the available data and information, SWRCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list because it cannot be determined if applicable water quality standards are not being exceeded.
Listing Extent:
Line of Evidence (LOE) for Decision ID 141718, Nickel
Region 2
Arroyo Las Positas
LOE ID:
284652
Pollutant:
Nickel
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Dissolved
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed SWAMP RWB2 Monitoring data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Nickel.
The dissolved nickel criterion continuous concentration (expressed as a 4-day average) to protect aquatic life in freshwater is hardness dependent. The criterion when calculated using a default hardness of 100 mg/L is 52 ug/L (California Toxics Rule, 2000).
Do Not List on 303(d) list (TMDL required list)(2018)
Revision Status
Revised
Impairment from Pollutant or Pollution:
Pollutant
Regional Board Conclusion:
Insufficient information is available to determine beneficial use support for this waterbody-pollutant combination with the statistical power and confidence required by the Listing Policy. Beneficial use support will be reassessed in a future cycle, if more data are available
Regional Board Decision Recommendation:
After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list. The readily available data and information is insufficient to determine, with the power and confidence of the Listing Policy, the applicable beneficial use support rating.
State Board Review of Regional Board Conclusion and Recommendation:
State Board Decision Recommendation:
After review of the available data and information, SWRCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list because it cannot be determined if applicable water quality standards are not being exceeded.
Listing Extent:
Line of Evidence (LOE) for Decision ID 141718, Nickel
Region 2
Arroyo Las Positas
LOE ID:
284652
Pollutant:
Nickel
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Dissolved
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed SWAMP RWB2 Monitoring data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Nickel.
The dissolved nickel criterion continuous concentration (expressed as a 4-day average) to protect aquatic life in freshwater is hardness dependent. The criterion when calculated using a default hardness of 100 mg/L is 52 ug/L (California Toxics Rule, 2000).
Line of Evidence (LOE) for Decision ID 141718, Nickel
Region 2
Arroyo Las Positas
LOE ID:
284733
Pollutant:
Nickel
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Dissolved
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed SWAMP RWB2 Monitoring data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Nickel.
The dissolved nickel criterion continuous concentration (expressed as a 4-day average) to protect aquatic life in freshwater is hardness dependent. The criterion when calculated using a default hardness of 100 mg/L is 52 ug/L (California Toxics Rule, 2000).
One sediment sample was collected at a "watershed integrator" site located close to the mouth of Arroyo Las Positas watershed at El Charro. The PEC was exceeded for nickel, with a sample concentration of 109 mg/kg dw.
Temporal Representation:
Sediment sample was collected in September of 2001.
Environmental Conditions:
QAPP Information:
All samples were collected and analyzed using procedures comparable with the SWAMP Quality Assurance Management Plan (SWRCB, 2002).
QAPP Information Reference(s):
Line of Evidence (LOE) for Decision ID 141718, Nickel
Region 2
Arroyo Las Positas
LOE ID:
290146
Pollutant:
Nickel
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Dissolved
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
6
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
The Arroyo Las Positas Creek watershed was monitored as part of SWAMP assessment. None of the six samples exceeded the water quality objectives for arsenic, chromium VI, copper, lead, nickel, silver and zinc.Concentrations of total dissolved chromium were well below the objective for chromium VI.
All waters shall be maintained free of toxic substances that are lethal to or that produce other detrimental responses in aquatic organisms. Table 3-4 in the Basin Plan (2007) lists freshwater water quality objectives for toxic pollutants: arsenic- 150 ug/L, chromium VI- 11 ug/L, copper - 9.0 ug/L, lead - 2.5 ug/L; nickel - 52 ug/L, silver-3.4 ug/L and zinc - 120 ug/L.
Data were collected at three sampling locations on Arroyo Las Positas Creek - ALP010 (El Charro), ALP100 (Altamont Creek), and ALP110 (Arroyo Las Positas).
Temporal Representation:
Samples were collected at all three sites during spring and dry seasons of the 2001-2002 sampling season.
Environmental Conditions:
QAPP Information:
All samples were collected and analyzed using procedures comparable with the SWAMP Quality Assurance Management Plan (SWRCB, 2002).
Line of Evidence (LOE) for Decision ID 141718, Nickel
Region 2
Arroyo Las Positas
LOE ID:
284733
Pollutant:
Nickel
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Dissolved
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed SWAMP RWB2 Monitoring data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Nickel.
The dissolved nickel criterion continuous concentration (expressed as a 4-day average) to protect aquatic life in freshwater is hardness dependent. The criterion when calculated using a default hardness of 100 mg/L is 52 ug/L (California Toxics Rule, 2000).
One sediment sample was collected at a "watershed integrator" site located close to the mouth of Arroyo Las Positas watershed at El Charro. The PEC was exceeded for nickel, with a sample concentration of 109 mg/kg dw.
Temporal Representation:
Sediment sample was collected in September of 2001.
Environmental Conditions:
QAPP Information:
All samples were collected and analyzed using procedures comparable with the SWAMP Quality Assurance Management Plan (SWRCB, 2002).
QAPP Information Reference(s):
Line of Evidence (LOE) for Decision ID 141718, Nickel
Region 2
Arroyo Las Positas
LOE ID:
290146
Pollutant:
Nickel
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Dissolved
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
6
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
The Arroyo Las Positas Creek watershed was monitored as part of SWAMP assessment. None of the six samples exceeded the water quality objectives for arsenic, chromium VI, copper, lead, nickel, silver and zinc.Concentrations of total dissolved chromium were well below the objective for chromium VI.
All waters shall be maintained free of toxic substances that are lethal to or that produce other detrimental responses in aquatic organisms. Table 3-4 in the Basin Plan (2007) lists freshwater water quality objectives for toxic pollutants: arsenic- 150 ug/L, chromium VI- 11 ug/L, copper - 9.0 ug/L, lead - 2.5 ug/L; nickel - 52 ug/L, silver-3.4 ug/L and zinc - 120 ug/L.
Data were collected at three sampling locations on Arroyo Las Positas Creek - ALP010 (El Charro), ALP100 (Altamont Creek), and ALP110 (Arroyo Las Positas).
Temporal Representation:
Samples were collected at all three sites during spring and dry seasons of the 2001-2002 sampling season.
Environmental Conditions:
QAPP Information:
All samples were collected and analyzed using procedures comparable with the SWAMP Quality Assurance Management Plan (SWRCB, 2002).
This pollutant is being considered for placement on the CWA section 303(d) List under section 3.2 of the Listing Policy. Under section 3.2 a single line of evidence is necessary to assess listing status.
Two lines of evidence are available in the administrative record to assess this pollutant. Four of the forty-three samples exceed the COLD dissolved oxygen Basin Plan objective.
Based on the readily available data and information, the weight of evidence indicates that there is sufficient justification against placing this water segment-pollutant combination on the CWA section 303(d) List.
This conclusion is based on the staff findings that: 1. The data used satisfies the data quality requirements of section 6.1.4 of the Policy. 2. The data used satisfies the data quantity requirements of section 6.1.5 of the Policy. 3. Four of the forty-three samples exceed the COLD dissolved oxygen Basin Plan objective and this does not exceed the allowable frequency listed in Table 3.2 of the Listing Policy. 4. Pursuant to section 3.11 of the Listing Policy, no additional data and information are available indicating that standards are not met.
Regional Board Decision Recommendation:
After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list because applicable water quality standards are not being exceeded.
State Board Review of Regional Board Conclusion and Recommendation:
State Board Decision Recommendation:
After review of this Regional Board decision, SWRCB staff recommend the decision be approved by the State Board.
Listing Extent:
Line of Evidence (LOE) for Decision ID 141719, Oxygen, Dissolved
Region 2
Arroyo Las Positas
LOE ID:
285374
Pollutant:
Oxygen, Dissolved
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
1
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2018 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 1 of 1 samples exceeded the water quality threshold for Oxygen, Dissolved.
Dissolved oxygen objectives for waters designated as cold water habitat shall be of a 7.0 mg/l minimum. (Water Quality Control Plan, San Francisco Bay Basin, Chapter III Water Quality Objectives.)
Objective/Criterion Reference:
DECISION ID
141719
Region 2
Arroyo Las Positas
Pollutant:
Oxygen, Dissolved
Final Listing Decision:
Do Not List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:
New Decision
Revision Status
Revised
Impairment from Pollutant or Pollution:
Pollutant
Regional Board Conclusion:
This pollutant is being considered for placement on the CWA section 303(d) List under section 3.2 of the Listing Policy. Under section 3.2 a single line of evidence is necessary to assess listing status.
Two lines of evidence are available in the administrative record to assess this pollutant. Four of the forty-three samples exceed the COLD dissolved oxygen Basin Plan objective.
Based on the readily available data and information, the weight of evidence indicates that there is sufficient justification against placing this water segment-pollutant combination on the CWA section 303(d) List.
This conclusion is based on the staff findings that: 1. The data used satisfies the data quality requirements of section 6.1.4 of the Policy. 2. The data used satisfies the data quantity requirements of section 6.1.5 of the Policy. 3. Four of the forty-three samples exceed the COLD dissolved oxygen Basin Plan objective and this does not exceed the allowable frequency listed in Table 3.2 of the Listing Policy. 4. Pursuant to section 3.11 of the Listing Policy, no additional data and information are available indicating that standards are not met.
Regional Board Decision Recommendation:
After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list because applicable water quality standards are not being exceeded.
State Board Review of Regional Board Conclusion and Recommendation:
State Board Decision Recommendation:
After review of this Regional Board decision, SWRCB staff recommend the decision be approved by the State Board.
Listing Extent:
Line of Evidence (LOE) for Decision ID 141719, Oxygen, Dissolved
Region 2
Arroyo Las Positas
LOE ID:
285374
Pollutant:
Oxygen, Dissolved
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
1
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2018 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 1 of 1 samples exceeded the water quality threshold for Oxygen, Dissolved.
Dissolved oxygen objectives for waters designated as cold water habitat shall be of a 7.0 mg/l minimum. (Water Quality Control Plan, San Francisco Bay Basin, Chapter III Water Quality Objectives.)
Line of Evidence (LOE) for Decision ID 141719, Oxygen, Dissolved
Region 2
Arroyo Las Positas
LOE ID:
285713
Pollutant:
Oxygen, Dissolved
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
10
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed SWAMP RWB2 Monitoring data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 10 samples exceeded the water quality threshold for Oxygen, Dissolved.
Dissolved oxygen objectives for waters designated as warm water habitat shall be of a 5.0 mg/l minimum. (Water Quality Control Plan, San Francisco Bay Basin, Chapter III Water Quality Objectives.)
Line of Evidence (LOE) for Decision ID 141719, Oxygen, Dissolved
Region 2
Arroyo Las Positas
LOE ID:
285713
Pollutant:
Oxygen, Dissolved
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
10
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed SWAMP RWB2 Monitoring data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 10 samples exceeded the water quality threshold for Oxygen, Dissolved.
Dissolved oxygen objectives for waters designated as warm water habitat shall be of a 5.0 mg/l minimum. (Water Quality Control Plan, San Francisco Bay Basin, Chapter III Water Quality Objectives.)
Line of Evidence (LOE) for Decision ID 141719, Oxygen, Dissolved
Region 2
Arroyo Las Positas
LOE ID:
285343
Pollutant:
Oxygen, Dissolved
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2019 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Oxygen, Dissolved.
Dissolved oxygen objectives for waters designated as cold water habitat shall be of a 7.0 mg/l minimum. (Water Quality Control Plan, San Francisco Bay Basin, Chapter III Water Quality Objectives.)
Line of Evidence (LOE) for Decision ID 141719, Oxygen, Dissolved
Region 2
Arroyo Las Positas
LOE ID:
284797
Pollutant:
Oxygen, Dissolved
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
1
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2020 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 1 of 1 samples exceeded the water quality threshold for Oxygen, Dissolved.
Dissolved oxygen objectives for waters designated as cold water habitat shall be of a 7.0 mg/l minimum. (Water Quality Control Plan, San Francisco Bay Basin, Chapter III Water Quality Objectives.)
The samples were collected at 1 monitoring site: 204R04816 (Arroyo Las Positas approx 350m west of Portola Ave).
Temporal Representation:
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2019 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Oxygen, Dissolved.
Dissolved oxygen objectives for waters designated as cold water habitat shall be of a 7.0 mg/l minimum. (Water Quality Control Plan, San Francisco Bay Basin, Chapter III Water Quality Objectives.)
Line of Evidence (LOE) for Decision ID 141719, Oxygen, Dissolved
Region 2
Arroyo Las Positas
LOE ID:
284797
Pollutant:
Oxygen, Dissolved
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
1
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2020 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 1 of 1 samples exceeded the water quality threshold for Oxygen, Dissolved.
Dissolved oxygen objectives for waters designated as cold water habitat shall be of a 7.0 mg/l minimum. (Water Quality Control Plan, San Francisco Bay Basin, Chapter III Water Quality Objectives.)
Line of Evidence (LOE) for Decision ID 141719, Oxygen, Dissolved
Region 2
Arroyo Las Positas
LOE ID:
284963
Pollutant:
Oxygen, Dissolved
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
1
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2019 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 1 of 1 samples exceeded the water quality threshold for Oxygen, Dissolved.
Dissolved oxygen objectives for waters designated as cold water habitat shall be of a 7.0 mg/l minimum. (Water Quality Control Plan, San Francisco Bay Basin, Chapter III Water Quality Objectives.)
Line of Evidence (LOE) for Decision ID 141719, Oxygen, Dissolved
Region 2
Arroyo Las Positas
LOE ID:
284963
Pollutant:
Oxygen, Dissolved
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
1
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2019 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 1 of 1 samples exceeded the water quality threshold for Oxygen, Dissolved.
Dissolved oxygen objectives for waters designated as cold water habitat shall be of a 7.0 mg/l minimum. (Water Quality Control Plan, San Francisco Bay Basin, Chapter III Water Quality Objectives.)
Line of Evidence (LOE) for Decision ID 141719, Oxygen, Dissolved
Region 2
Arroyo Las Positas
LOE ID:
285076
Pollutant:
Oxygen, Dissolved
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
7
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed SWAMP RWB2 Monitoring data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 7 samples exceeded the water quality threshold for Oxygen, Dissolved.
Dissolved oxygen objectives for waters designated as cold water habitat shall be of a 7.0 mg/l minimum. (Water Quality Control Plan, San Francisco Bay Basin, Chapter III Water Quality Objectives.)
Line of Evidence (LOE) for Decision ID 141719, Oxygen, Dissolved
Region 2
Arroyo Las Positas
LOE ID:
285511
Pollutant:
Oxygen, Dissolved
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
1
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2019 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 1 of 1 samples exceeded the water quality threshold for Oxygen, Dissolved.
Dissolved oxygen objectives for waters designated as warm water habitat shall be of a 5.0 mg/l minimum. (Water Quality Control Plan, San Francisco Bay Basin, Chapter III Water Quality Objectives.)
Water Board staff assessed SWAMP RWB2 Monitoring data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 7 samples exceeded the water quality threshold for Oxygen, Dissolved.
Dissolved oxygen objectives for waters designated as cold water habitat shall be of a 7.0 mg/l minimum. (Water Quality Control Plan, San Francisco Bay Basin, Chapter III Water Quality Objectives.)
Line of Evidence (LOE) for Decision ID 141719, Oxygen, Dissolved
Region 2
Arroyo Las Positas
LOE ID:
285511
Pollutant:
Oxygen, Dissolved
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
1
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2019 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 1 of 1 samples exceeded the water quality threshold for Oxygen, Dissolved.
Dissolved oxygen objectives for waters designated as warm water habitat shall be of a 5.0 mg/l minimum. (Water Quality Control Plan, San Francisco Bay Basin, Chapter III Water Quality Objectives.)
Line of Evidence (LOE) for Decision ID 141719, Oxygen, Dissolved
Region 2
Arroyo Las Positas
LOE ID:
285799
Pollutant:
Oxygen, Dissolved
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2012 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Oxygen, Dissolved.
Dissolved oxygen objectives for waters designated as warm water habitat shall be of a 5.0 mg/l minimum. (Water Quality Control Plan, San Francisco Bay Basin, Chapter III Water Quality Objectives.)
Line of Evidence (LOE) for Decision ID 141719, Oxygen, Dissolved
Region 2
Arroyo Las Positas
LOE ID:
284957
Pollutant:
Oxygen, Dissolved
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2014 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Oxygen, Dissolved.
Line of Evidence (LOE) for Decision ID 141719, Oxygen, Dissolved
Region 2
Arroyo Las Positas
LOE ID:
285799
Pollutant:
Oxygen, Dissolved
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2012 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Oxygen, Dissolved.
Dissolved oxygen objectives for waters designated as warm water habitat shall be of a 5.0 mg/l minimum. (Water Quality Control Plan, San Francisco Bay Basin, Chapter III Water Quality Objectives.)
Line of Evidence (LOE) for Decision ID 141719, Oxygen, Dissolved
Region 2
Arroyo Las Positas
LOE ID:
284957
Pollutant:
Oxygen, Dissolved
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2014 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Oxygen, Dissolved.
Dissolved oxygen objectives for waters designated as cold water habitat shall be of a 7.0 mg/l minimum. (Water Quality Control Plan, San Francisco Bay Basin, Chapter III Water Quality Objectives.)
Line of Evidence (LOE) for Decision ID 141719, Oxygen, Dissolved
Region 2
Arroyo Las Positas
LOE ID:
285201
Pollutant:
Oxygen, Dissolved
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2019 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Oxygen, Dissolved.
Dissolved oxygen objectives for waters designated as warm water habitat shall be of a 5.0 mg/l minimum. (Water Quality Control Plan, San Francisco Bay Basin, Chapter III Water Quality Objectives.)
Line of Evidence (LOE) for Decision ID 141719, Oxygen, Dissolved
Region 2
Arroyo Las Pos"left" valign="top" width="33%">SWAMP Data:
Non-SWAMP
Water Quality Objective/Criterion:
Dissolved oxygen objectives for waters designated as cold water habitat shall be of a 7.0 mg/l minimum. (Water Quality Control Plan, San Francisco Bay Basin, Chapter III Water Quality Objectives.)
Line of Evidence (LOE) for Decision ID 141719, Oxygen, Dissolved
Region 2
Arroyo Las Positas
LOE ID:
285201
Pollutant:
Oxygen, Dissolved
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2019 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Oxygen, Dissolved.
Dissolved oxygen objectives for waters designated as warm water habitat shall be of a 5.0 mg/l minimum. (Water Quality Control Plan, San Francisco Bay Basin, Chapter III Water Quality Objectives.)
Line of Evidence (LOE) for Decision ID 141719, Oxygen, Dissolved
Region 2
Arroyo Las Positas
LOE ID:
285778
Pollutant:
Oxygen, Dissolved
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed SWAMP RWB2 Monitoring data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Oxygen, Dissolved.
Dissolved oxygen objectives for waters designated as cold water habitat shall be of a 7.0 mg/l minimum. (Water Quality Control Plan, San Francisco Bay Basin, Chapter III Water Quality Objectives.)
Line of Evidence (LOE) for Decision ID 141719, Oxygen, Dissolved
Region 2
Arroyo Las Positas
LOE ID:
285602
Pollutant:
Oxygen, Dissolved
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2019 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Oxygen, Dissolved.
Dissolved oxygen objectives for waters designated as warm water habitat shall be of a 5.0 mg/l minimum. (Water Quality Control Plan, San Francisco Bay Basin, Chapter III Water Quality Objectives.)
Water Board staff assessed SWAMP RWB2 Monitoring data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Oxygen, Dissolved.
Dissolved oxygen objectives for waters designated as cold water habitat shall be of a 7.0 mg/l minimum. (Water Quality Control Plan, San Francisco Bay Basin, Chapter III Water Quality Objectives.)
Line of Evidence (LOE) for Decision ID 141719, Oxygen, Dissolved
Region 2
Arroyo Las Positas
LOE ID:
285602
Pollutant:
Oxygen, Dissolved
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2019 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Oxygen, Dissolved.
Dissolved oxygen objectives for waters designated as warm water habitat shall be of a 5.0 mg/l minimum. (Water Quality Control Plan, San Francisco Bay Basin, Chapter III Water Quality Objectives.)
Line of Evidence (LOE) for Decision ID 141719, Oxygen, Dissolved
Region 2
Arroyo Las Positas
LOE ID:
285097
Pollutant:
Oxygen, Dissolved
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2017 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Oxygen, Dissolved.
Dissolved oxygen objectives for waters designated as cold water habitat shall be of a 7.0 mg/l minimum. (Water Quality Control Plan, San Francisco Bay Basin, Chapter III Water Quality Objectives.)
Line of Evidence (LOE) for Decision ID 141719, Oxygen, Dissolved
Region 2
Arroyo Las Positas
LOE ID:
285097
Pollutant:
Oxygen, Dissolved
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2017 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Oxygen, Dissolved.
Dissolved oxygen objectives for waters designated as cold water habitat shall be of a 7.0 mg/l minimum. (Water Quality Control Plan, San Francisco Bay Basin, Chapter III Water Quality Objectives.)
Line of Evidence (LOE) for Decision ID 141719, Oxygen, Dissolved
Region 2
Arroyo Las Positas
LOE ID:
285286
Pollutant:
Oxygen, Dissolved
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2018 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Oxygen, Dissolved.
Dissolved oxygen objectives for waters designated as warm water habitat shall be of a 5.0 mg/l minimum. (Water Quality Control Plan, San Francisco Bay Basin, Chapter III Water Quality Objectives.)
Line of Evidence (LOE) for Decision ID 141719, Oxygen, Dissolved
Region 2
Arroyo Las Positas
LOE ID:
285155
Pollutant:
Oxygen, Dissolved
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
12
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed SWAMP RWB2 Monitoring data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 12 samples exceeded the water quality threshold for Oxygen, Dissolved.
Dissolved oxygen objectives for waters designated as warm water habitat shall be of a 5.0 mg/l minimum. (Water Quality Control Plan, San Francisco Bay Basin, Chapter III Water Quality Objectives.)
The samples were collected at 1 monitoring site: 204ALP075 (Arroyo las Positas at Paseo Laguna Seco apartments).
Temporal Representation:
The samples were collected between the dates of 2018-05-10 and 2019-08-26
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2018 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Oxygen, Dissolved.
Dissolved oxygen objectives for waters designated as warm water habitat shall be of a 5.0 mg/l minimum. (Water Quality Control Plan, San Francisco Bay Basin, Chapter III Water Quality Objectives.)
Line of Evidence (LOE) for Decision ID 141719, Oxygen, Dissolved
Region 2
Arroyo Las Positas
LOE ID:
285155
Pollutant:
Oxygen, Dissolved
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
12
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed SWAMP RWB2 Monitoring data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 12 samples exceeded the water quality threshold for Oxygen, Dissolved.
Dissolved oxygen objectives for waters designated as warm water habitat shall be of a 5.0 mg/l minimum. (Water Quality Control Plan, San Francisco Bay Basin, Chapter III Water Quality Objectives.)
Line of Evidence (LOE) for Decision ID 141719, Oxygen, Dissolved
Region 2
Arroyo Las Positas
LOE ID:
285342
Pollutant:
Oxygen, Dissolved
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2017 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Oxygen, Dissolved.
Dissolved oxygen objectives for waters designated as cold water habitat shall be of a 7.0 mg/l minimum. (Water Quality Control Plan, San Francisco Bay Basin, Chapter III Water Quality Objectives.)
Line of Evidence (LOE) for Decision ID 141719, Oxygen, Dissolved
Region 2
Arroyo Las Positas
LOE ID:
285342
Pollutant:
Oxygen, Dissolved
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2017 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Oxygen, Dissolved.
Dissolved oxygen objectives for waters designated as cold water habitat shall be of a 7.0 mg/l minimum. (Water Quality Control Plan, San Francisco Bay Basin, Chapter III Water Quality Objectives.)
Line of Evidence (LOE) for Decision ID 141719, Oxygen, Dissolved
Region 2
Arroyo Las Positas
LOE ID:
285600
Pollutant:
Oxygen, Dissolved
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2016 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Oxygen, Dissolved.
Dissolved oxygen objectives for waters designated as warm water habitat shall be of a 5.0 mg/l minimum. (Water Quality Control Plan, San Francisco Bay Basin, Chapter III Water Quality Objectives.)
Line of Evidence (LOE) for Decision ID 141719, Oxygen, Dissolved
Region 2
Arroyo Las Positas
LOE ID:
285157
Pollutant:
Oxygen, Dissolved
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed SWAMP RWB2 Monitoring data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Oxygen, Dissolved.
Dissolved oxygen objectives for waters designated as warm water habitat shall be of a 5.0 mg/l minimum. (Water Quality Control Plan, San Francisco Bay Basin, Chapter III Water Quality Objectives.)
Water Board staff assessed BASMAA RMC Monitoring in WY2016 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Oxygen, Dissolved.
Dissolved oxygen objectives for waters designated as warm water habitat shall be of a 5.0 mg/l minimum. (Water Quality Control Plan, San Francisco Bay Basin, Chapter III Water Quality Objectives.)
Line of Evidence (LOE) for Decision ID 141719, Oxygen, Dissolved
Region 2
Arroyo Las Positas
LOE ID:
285157
Pollutant:
Oxygen, Dissolved
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed SWAMP RWB2 Monitoring data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Oxygen, Dissolved.
Dissolved oxygen objectives for waters designated as warm water habitat shall be of a 5.0 mg/l minimum. (Water Quality Control Plan, San Francisco Bay Basin, Chapter III Water Quality Objectives.)
Line of Evidence (LOE) for Decision ID 141719, Oxygen, Dissolved
Region 2
Arroyo Las Positas
LOE ID:
285214
Pollutant:
Oxygen, Dissolved
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2016 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Oxygen, Dissolved.
Dissolved oxygen objectives for waters designated as cold water habitat shall be of a 7.0 mg/l minimum. (Water Quality Control Plan, San Francisco Bay Basin, Chapter III Water Quality Objectives.)
Line of Evidence (LOE) for Decision ID 141719, Oxygen, Dissolved
Region 2
Arroyo Las Positas
LOE ID:
286283
Pollutant:
Oxygen, Dissolved
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2012 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Oxygen, Dissolved.
Line of Evidence (LOE) for Decision ID 141719, Oxygen, Dissolved
Region 2
Arroyo Las Positas
LOE ID:
285214
Pollutant:
Oxygen, Dissolved
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2016 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Oxygen, Dissolved.
Dissolved oxygen objectives for waters designated as cold water habitat shall be of a 7.0 mg/l minimum. (Water Quality Control Plan, San Francisco Bay Basin, Chapter III Water Quality Objectives.)
Line of Evidence (LOE) for Decision ID 141719, Oxygen, Dissolved
Region 2
Arroyo Las Positas
LOE ID:
286283
Pollutant:
Oxygen, Dissolved
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2012 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Oxygen, Dissolved.
Dissolved oxygen objectives for waters designated as warm water habitat shall be of a 5.0 mg/l minimum. (Water Quality Control Plan, San Francisco Bay Basin, Chapter III Water Quality Objectives.)
Line of Evidence (LOE) for Decision ID 141719, Oxygen, Dissolved
Region 2
Arroyo Las Positas
LOE ID:
285683
Pollutant:
Oxygen, Dissolved
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2014 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Oxygen, Dissolved.
Dissolved oxygen objectives for waters designated as warm water habitat shall be of a 5.0 mg/l minimum. (Water Quality Control Plan, San Francisco Bay Basin, Chapter III Water Quality Objectives.)
Line of Evidence (LOE) for Decision ID 141719, Oxygen, Dissolved
Region 2
Field, Habitat, Toxicity, WQ data from the California Environmental Data Exchange Network assembled for the 2024 Integrated Report in Region 2.
SWAMP Data:
Non-SWAMP
Water Quality Objective/Criterion:
Dissolved oxygen objectives for waters designated as warm water habitat shall be of a 5.0 mg/l minimum. (Water Quality Control Plan, San Francisco Bay Basin, Chapter III Water Quality Objectives.)
Line of Evidence (LOE) for Decision ID 141719, Oxygen, Dissolved
Region 2
Arroyo Las Positas
LOE ID:
285683
Pollutant:
Oxygen, Dissolved
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2014 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Oxygen, Dissolved.
Dissolved oxygen objectives for waters designated as warm water habitat shall be of a 5.0 mg/l minimum. (Water Quality Control Plan, San Francisco Bay Basin, Chapter III Water Quality Objectives.)
Line of Evidence (LOE) for Decision ID 141719, Oxygen, Dissolved
Region 2
Arroyo Las Positas
LOE ID:
285601
Pollutant:
Oxygen, Dissolved
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2017 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Oxygen, Dissolved.
Dissolved oxygen objectives for waters designated as warm water habitat shall be of a 5.0 mg/l minimum. (Water Quality Control Plan, San Francisco Bay Basin, Chapter III Water Quality Objectives.)
Line of Evidence (LOE) for Decision ID 141719, Oxygen, Dissolved
Region 2
Arroyo Las Positas
LOE ID:
285486
Pollutant:
Oxygen, Dissolved
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2014 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Oxygen, Dissolved.
Dissolved oxygen objectives for waters designated as warm water habitat shall be of a 5.0 mg/l minimum. (Water Quality Control Plan, San Francisco Bay Basin, Chapter III Water Quality Objectives.)
Water Board staff assessed BASMAA RMC Monitoring in WY2017 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Oxygen, Dissolved.
Dissolved oxygen objectives for waters designated as warm water habitat shall be of a 5.0 mg/l minimum. (Water Quality Control Plan, San Francisco Bay Basin, Chapter III Water Quality Objectives.)
Line of Evidence (LOE) for Decision ID 141719, Oxygen, Dissolved
Region 2
Arroyo Las Positas
LOE ID:
285486
Pollutant:
Oxygen, Dissolved
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2014 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Oxygen, Dissolved.
Dissolved oxygen objectives for waters designated as warm water habitat shall be of a 5.0 mg/l minimum. (Water Quality Control Plan, San Francisco Bay Basin, Chapter III Water Quality Objectives.)
Line of Evidence (LOE) for Decision ID 141719, Oxygen, Dissolved
Region 2
Arroyo Las Positas
LOE ID:
284931
Pollutant:
Oxygen, Dissolved
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2015 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Oxygen, Dissolved.
Dissolved oxygen objectives for waters designated as cold water habitat shall be of a 7.0 mg/l minimum. (Water Quality Control Plan, San Francisco Bay Basin, Chapter III Water Quality Objectives.)
Line of Evidence (LOE) for Decision ID 141719, Oxygen, Dissolved
Region 2
Arroyo Las Positas
LOE ID:
284931
Pollutant:
Oxygen, Dissolved
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2015 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Oxygen, Dissolved.
Dissolved oxygen objectives for waters designated as cold water habitat shall be of a 7.0 mg/l minimum. (Water Quality Control Plan, San Francisco Bay Basin, Chapter III Water Quality Objectives.)
Line of Evidence (LOE) for Decision ID 141719, Oxygen, Dissolved
Region 2
Arroyo Las Positas
LOE ID:
285090
Pollutant:
Oxygen, Dissolved
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2012 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Oxygen, Dissolved.
Dissolved oxygen objectives for waters designated as cold water habitat shall be of a 7.0 mg/l minimum. (Water Quality Control Plan, San Francisco Bay Basin, Chapter III Water Quality Objectives.)
Line of Evidence (LOE) for Decision ID 141719, Oxygen, Dissolved
Region 2
Arroyo Las Positas
LOE ID:
285747
Pollutant:
Oxygen, Dissolved
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
10
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed SWAMP RWB2 Monitoring data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 10 samples exceeded the water quality threshold for Oxygen, Dissolved.
Dissolved oxygen objectives for waters designated as cold water habitat shall be of a 7.0 mg/l minimum. (Water Quality Control Plan, San Francisco Bay Basin, Chapter III Water Quality Objectives.)
The samples were collected at 1 monitoring site: 204ALP040 (Airway Blvd. Exit).
Temporal Representation:
The samples were collected between the dates ox:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2012 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Oxygen, Dissolved.
Dissolved oxygen objectives for waters designated as cold water habitat shall be of a 7.0 mg/l minimum. (Water Quality Control Plan, San Francisco Bay Basin, Chapter III Water Quality Objectives.)
Line of Evidence (LOE) for Decision ID 141719, Oxygen, Dissolved
Region 2
Arroyo Las Positas
LOE ID:
285747
Pollutant:
Oxygen, Dissolved
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
10
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed SWAMP RWB2 Monitoring data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 10 samples exceeded the water quality threshold for Oxygen, Dissolved.
Dissolved oxygen objectives for waters designated as cold water habitat shall be of a 7.0 mg/l minimum. (Water Quality Control Plan, San Francisco Bay Basin, Chapter III Water Quality Objectives.)
Line of Evidence (LOE) for Decision ID 141719, Oxygen, Dissolved
Region 2
Arroyo Las Positas
LOE ID:
285115
Pollutant:
Oxygen, Dissolved
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2012 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Oxygen, Dissolved.
Dissolved oxygen objectives for waters designated as cold water habitat shall be of a 7.0 mg/l minimum. (Water Quality Control Plan, San Francisco Bay Basin, Chapter III Water Quality Objectives.)
Line of Evidence (LOE) for Decision ID 141719, Oxygen, Dissolved
Region 2
Arroyo Las Positas
LOE ID:
285115
Pollutant:
Oxygen, Dissolved
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2012 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Oxygen, Dissolved.
Dissolved oxygen objectives for waters designated as cold water habitat shall be of a 7.0 mg/l minimum. (Water Quality Control Plan, San Francisco Bay Basin, Chapter III Water Quality Objectives.)
Line of Evidence (LOE) for Decision ID 141719, Oxygen, Dissolved
Region 2
Arroyo Las Positas
LOE ID:
285158
Pollutant:
Oxygen, Dissolved
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
7
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed SWAMP RWB2 Monitoring data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 7 samples exceeded the water quality threshold for Oxygen, Dissolved.
Dissolved oxygen objectives for waters designated as warm water habitat shall be of a 5.0 mg/l minimum. (Water Quality Control Plan, San Francisco Bay Basin, Chapter III Water Quality Objectives.)
Line of Evidence (LOE) for Decision ID 141719, Oxygen, Dissolved
Region 2
Arroyo Las Positas
LOE ID:
285021
Pollutant:
Oxygen, Dissolved
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2014 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Oxygen, Dissolved.
Dissolved oxygen objectives for waters designated as cold water habitat shall be of a 7.0 mg/l minimum. (Water Quality Control Plan, San Francisco Bay Basin, Chapter III Water Quality Objectives.)
Water Board staff assessed SWAMP RWB2 Monitoring data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 7 samples exceeded the water quality threshold for Oxygen, Dissolved.
Dissolved oxygen objectives for waters designated as warm water habitat shall be of a 5.0 mg/l minimum. (Water Quality Control Plan, San Francisco Bay Basin, Chapter III Water Quality Objectives.)
Line of Evidence (LOE) for Decision ID 141719, Oxygen, Dissolved
Region 2
Arroyo Las Positas
LOE ID:
285021
Pollutant:
Oxygen, Dissolved
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2014 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Oxygen, Dissolved.
Dissolved oxygen objectives for waters designated as cold water habitat shall be of a 7.0 mg/l minimum. (Water Quality Control Plan, San Francisco Bay Basin, Chapter III Water Quality Objectives.)
Line of Evidence (LOE) for Decision ID 141719, Oxygen, Dissolved
Region 2
Arroyo Las Positas
LOE ID:
285500
Pollutant:
Oxygen, Dissolved
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2015 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Oxygen, Dissolved.
Dissolved oxygen objectives for waters designated as warm water habitat shall be of a 5.0 mg/l minimum. (Water Quality Control Plan, San Francisco Bay Basin, Chapter III Water Quality Objectives.)
Line of Evidence (LOE) for Decision ID 141719, Oxygen, Dissolved
Region 2
Arroyo Las Positas
LOE ID:
284825
Pollutant:
Oxygen, Dissolved
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
1
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2019 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 1 of 1 samples exceeded the water quality threshold for Oxygen, Dissolved.
Line of Evidence (LOE) for Decision ID 141719, Oxygen, Dissolved
Region 2
Arroyo Las Positas
LOE ID:
285500
Pollutant:
Oxygen, Dissolved
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2015 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Oxygen, Dissolved.
Dissolved oxygen objectives for waters designated as warm water habitat shall be of a 5.0 mg/l minimum. (Water Quality Control Plan, San Francisco Bay Basin, Chapter III Water Quality Objectives.)
Line of Evidence (LOE) for Decision ID 141719, Oxygen, Dissolved
Region 2
Arroyo Las Positas
LOE ID:
284825
Pollutant:
Oxygen, Dissolved
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
1
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2019 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 1 of 1 samples exceeded the water quality threshold for Oxygen, Dissolved.
Dissolved oxygen objectives for waters designated as cold water habitat shall be of a 7.0 mg/l minimum. (Water Quality Control Plan, San Francisco Bay Basin, Chapter III Water Quality Objectives.)
Line of Evidence (LOE) for Decision ID 141719, Oxygen, Dissolved
Region 2
Arroyo Las Positas
LOE ID:
285630
Pollutant:
Oxygen, Dissolved
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
1
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2020 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 1 of 1 samples exceeded the water quality threshold for Oxygen, Dissolved.
Dissolved oxygen objectives for waters designated as warm water habitat shall be of a 5.0 mg/l minimum. (Water Quality Control Plan, San Francisco Bay Basin, Chapter III Water Quality Objectives.)
Line of Evidence (LOE) for Decision ID 141719, Oxygen, Dissolved
Region 2
Arroyo Las Positas
LOE ID:
285761
Pollutant:
Oxygen, Dissolved
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2017 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Oxygen, Dissolved.
Dissolved oxygen objectives for waters designated as warm water habitat shall be of a 5.0 mg/l minimum. (Water Quality Control Plan, San Francisco Bay Basin, Chapter III Water Quality Objectives.)
Line of Evidence (LOE) for Decision ID 141719, Oxygen, Dissolved
Region 2
Arroyo Las Positas
LOE ID:
285779
Pollutant:
Oxygen, Dissolved
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
12
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed SWAMP RWB2 Monitoring data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 12 samples exceeded the water quality threshold for Oxygen, Dissolved.
Dissolved oxygen objectives for waters designated as cold water habitat shall be of a 7.0 mg/l minimum. (Water Quality Control Plan, San Francisco Bay Basin, Chapter III Water Quality Objectives.)
Insufficient information is available to determine beneficial use support for this waterbody-pollutant combination with the statistical power and confidence required by the Listing Policy. Beneficial use support will be reassessed in a future cycle, if more data are available
Regional Board Decision Recommendation:
After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list. The readily available data and information is insufficient to determine, with the power and confidence of the Listing Policy, the applicable beneficial use support rating.
State Board Review of Regional Board Conclusion and Recommendation:
State Board Decision Recommendation:
After review of the available data and information, SWRCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list because it cannot be determined if applicable water quality standards are not being exceeded.
Listing Extent:
Line of Evidence (LOE) for Decision ID 148798, PAHs (Polycyclic Aromatic Hydrocarbons)
Region 2
Arroyo Las Positas
LOE ID:
290097
Pollutant:
PAHs (Polycyclic Aromatic Hydrocarbons)
LOE Subgroup:
Pollutant-Sediment
Matrix:
Sediment
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Concentrations of Anthracene, fluorene, napthalene, phenanthrene, benz(a)anthracene, benzo(a)pyrene, chrysene, fluoranthrene, pyrene, PAH (total), PCB (total), chlordane, dieldrin, DDD/DDE/DDT, endrin, heptachlor epoxide, and HCH, gamma in one sediment sample collected in spring 2005 did not exceed the sediment quality guidelines.
Dissolved oxygen objectives for waters designated as cold water habitat shall be of a 7.0 mg/l minimum. (Water Quality Control Plan, San Francisco Bay Basin, Chapter III Water Quality Objectives.)
Line of Evidence (LOE) for Decision ID 141719, Oxygen, Dissolved
Region 2
Arroyo Las Positas
LOE ID:
285630
Pollutant:
Oxygen, Dissolved
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
1
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2020 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 1 of 1 samples exceeded the water quality threshold for Oxygen, Dissolved.
Dissolved oxygen objectives for waters designated as warm water habitat shall be of a 5.0 mg/l minimum. (Water Quality Control Plan, San Francisco Bay Basin, Chapter III Water Quality Objectives.)
Line of Evidence (LOE) for Decision ID 141719, Oxygen, Dissolved
Region 2
Arroyo Las Positas
LOE ID:
285761
Pollutant:
Oxygen, Dissolved
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2017 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Oxygen, Dissolved.
Dissolved oxygen objectives for waters designated as warm water habitat shall be of a 5.0 mg/l minimum. (Water Quality Control Plan, San Francisco Bay Basin, Chapter III Water Quality Objectives.)
Line of Evidence (LOE) for Decision ID 141719, Oxygen, Dissolved
Region 2
Arroyo Las Positas
LOE ID:
285779
Pollutant:
Oxygen, Dissolved
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
12
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed SWAMP RWB2 Monitoring data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 12 samples exceeded the water quality threshold for Oxygen, Dissolved.
Dissolved oxygen objectives for waters designated as cold water habitat shall be of a 7.0 mg/l minimum. (Water Quality Control Plan, San Francisco Bay Basin, Chapter III Water Quality Objectives.)
Insufficient information is available to determine beneficial use support for this waterbody-pollutant combination with the statistical power and confidence required by the Listing Policy. Beneficial use support will be reassessed in a future cycle, if more data are available
Regional Board Decision Recommendation:
After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list. The readily available data and information is insufficient to determine, with the power and confidence of the Listing Policy, the applicable beneficial use support rating.
State Board Review of Regional Board Conclusion and Recommendation:
State Board Decision Recommendation:
After review of the available data and information, SWRCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list because it cannot be determined if applicable water quality standards are not being exceeded.
Listing Extent:
Line of Evidence (LOE) for Decision ID 148798, PAHs (Polycyclic Aromatic Hydrocarbons)
Region 2
Arroyo Las Positas
LOE ID:
290097
Pollutant:
PAHs (Polycyclic Aromatic Hydrocarbons)
LOE Subgroup:
Pollutant-Sediment
Matrix:
Sediment
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Concentrations of Anthracene, fluorene, napthalene, phenanthrene, benz(a)anthracene, benzo(a)pyrene, chrysene, fluoranthrene, pyrene, PAH (total), PCB (total), chlordane, dieldrin, DDD/DDE/DDT, endrin, heptachlor epoxide, and HCH, gamma in one sediment sample collected in spring 2005 did not exceed the sediment quality guidelines.
Insufficient information is available to determine beneficial use support for this waterbody-pollutant combination with the statistical power and confidence required by the Listing Policy. Beneficial use support will be reassessed in a future cycle, if more data are available.
Regional Board Decision Recommendation:
After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list. The readily available data and information is insufficient to determine, with the power and confidence of the Listing Policy, the applicable beneficial use support rating.
State Board Review of Regional Board Conclusion and Recommendation:
State Board Decision Recommendation:
After review of this Regional Board decision, SWRCB staff recommend the decision be approved by the State Board.
Listing Extent:
Line of Evidence (LOE) for Decision ID 141722, PCBs (Polychlorinated biphenyls)
Region 2
Arroyo Las Positas
LOE ID:
290098
Pollutant:
PCBs (Polychlorinated biphenyls)
LOE Subgroup:
Pollutant-Sediment
Matrix:
Sediment
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Concentrations of Anthracene, fluorene, napthalene, phenanthrene, benz(a)anthracene, benzo(a)pyrene, chrysene, fluoranthrene, pyrene, PAH (total), PCB (total), chlordane, dieldrin, DDD/DDE/DDT, endrin, heptachlor epoxide, and HCH, gamma in one sediment sample collected in spring 2005 did not exceed the sediment quality guidelines.
Line of Evidence (LOE) for Decision ID 141722, PCBs (Polychlorinated biphenyls)
Region 2
Arroyo Las Positas
LOE ID:
290187
Pollutant:
PCBs (Polychlorinated biphenyls)
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
None
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
The Arroyo Las Positas Creek watershed was monitored as part of SWAMP assessment. Neither sample exceeded the water quality objectives for Chlorpyrifos, Dacthal, diazinon, disulfoton, endosulfan, Lindane/gamma Hexachlorocyclohexane (gamma-HCH), methyl parathion, thiobencarb.
All waters shall be maintained free of toxic substances that are lethal to or that produce other detrimental responses in aquatic organisms. There shall be no chronic toxicity in ambient waters. Chronic toxicity is a detrimental biological effect on growth rate, reproduction, fertilization success, larval development, population abundance, community composition, or any other relevant measure of the health of an organism, population, or community.Diazinon water quality objective, 0.1 ug/L (acute)
Insufficient information is available to determine beneficial use support for this waterbody-pollutant combination with the statistical power and confidence required by the Listing Policy. Beneficial use support will be reassessed in a future cycle, if more data are available.
Regional Board Decision Recommendation:
After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list. The readily available data and information is insufficient to determine, with the power and confidence of the Listing Policy, the applicable beneficial use support rating.
State Board Review of Regional Board Conclusion and Recommendation:
State Board Decision Recommendation:
After review of the available data and information, SWRCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list because it cannot be determined if applicable water quality standards are not being exceeded.
Listing Extent:
Line of Evidence (LOE) for Decision ID 141721, Phenanthrene
Region 2
Arroyo Las Positas
LOE ID:
290112
Pollutant:
Phenanthrene
LOE Subgroup:
Pollutant-Sediment
Matrix:
Sediment
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Concentrations of Anthracene, fluorene, napthalene, phenanthrene, benz(a)anthracene, benzo(a)pyrene, chrysene, fluoranthrene, pyrene, PAH (total), PCB (total), chlordane, dieldrin, DDD/DDE/DDT, endrin, heptachlor epoxide, and HCH, gamma in one sediment sample collected in spring 2005 did not exceed the sediment quality guidelines.
Insufficient information is available to determine beneficial use support for this waterbody-pollutant combination with the statistical power and confidence required by the Listing Policy. Beneficial use support will be reassessed in a future cycle, if more data are available.
Regional Board Decision Recommendation:
After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list. The readily available data and information is insufficient to determine, with the power and confidence of the Listing Policy, the applicable beneficial use support rating.
State Board Review of Regional Board Conclusion and Recommendation:
State Board Decision Recommendation:
After review of this Regional Board decision, SWRCB staff recommend the decision be approved by the State Board.
Listing Extent:
Line of Evidence (LOE) for Decision ID 141722, PCBs (Polychlorinated biphenyls)
Region 2
Arroyo Las Positas
LOE ID:
290098
Pollutant:
PCBs (Polychlorinated biphenyls)
LOE Subgroup:
Pollutant-Sediment
Matrix:
Sediment
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Concentrations of Anthracene, fluorene, napthalene, phenanthrene, benz(a)anthracene, benzo(a)pyrene, chrysene, fluoranthrene, pyrene, PAH (total), PCB (total), chlordane, dieldrin, DDD/DDE/DDT, endrin, heptachlor epoxide, and HCH, gamma in one sediment sample collected in spring 2005 did not exceed the sediment quality guidelines.
Line of Evidence (LOE) for Decision ID 141722, PCBs (Polychlorinated biphenyls)
Region 2
Arroyo Las Positas
LOE ID:
290187
Pollutant:
PCBs (Polychlorinated biphenyls)
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
None
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
The Arroyo Las Positas Creek watershed was monitored as part of SWAMP assessment. Neither sample exceeded the water quality objectives for Chlorpyrifos, Dacthal, diazinon, disulfoton, endosulfan, Lindane/gamma Hexachlorocyclohexane (gamma-HCH), methyl parathion, thiobencarb.
All waters shall be maintained free of toxic substances that are lethal to or that produce other detrimental responses in aquatic organisms. There shall be no chronic toxicity in ambient waters. Chronic toxicity is a detrimental biological effect on growth rate, reproduction, fertilization success, larval development, population abundance, community composition, or any other relevant measure of the health of an organism, population, or community.Diazinon water quality objective, 0.1 ug/L (acute)
Insufficient information is available to determine beneficial use support for this waterbody-pollutant combination with the statistical power and confidence required by the Listing Policy. Beneficial use support will be reassessed in a future cycle, if more data are available.
Regional Board Decision Recommendation:
After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list. The readily available data and information is insufficient to determine, with the power and confidence of the Listing Policy, the applicable beneficial use support rating.
State Board Review of Regional Board Conclusion and Recommendation:
State Board Decision Recommendation:
After review of the available data and information, SWRCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list because it cannot be determined if applicable water quality standards are not being exceeded.
Listing Extent:
Line of Evidence (LOE) for Decision ID 141723, Pyrene
Region 2
Arroyo Las Positas
LOE ID:
290113
Pollutant:
Pyrene
LOE Subgroup:
Pollutant-Sediment
Matrix:
Sediment
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Concentrations of Anthracene, fluorene, napthalene, phenanthrene, benz(a)anthracene, benzo(a)pyrene, chrysene, fluoranthrene, pyrene, PAH (total), PCB (total), chlordane, dieldrin, DDD/DDE/DDT, endrin, heptachlor epoxide, and HCH, gamma in one sediment sample collected in spring 2005 did not exceed the sediment quality guidelines.
Insufficient information is available to determine beneficial use support for this waterbody-pollutant combination with the statistical power and confidence required by the Listing Policy. Beneficial use support will be reassessed in a future cycle, if more data are available.
Regional Board Decision Recommendation:
After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list. The readily available data and information is insufficient to determine, with the power and confidence of the Listing Policy, the applicable beneficial use support rating.
State Board Review of Regional Board Conclusion and Recommendation:
State Board Decision Recommendation:
After review of the available data and information, SWRCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list because it cannot be determined if applicable water quality standards are not being exceeded.
Listing Extent:
Line of Evidence (LOE) for Decision ID 141721, Phenanthrene
Region 2
Arroyo Las Positas
LOE ID:
290112
Pollutant:
Phenanthrene
LOE Subgroup:
Pollutant-Sediment
Matrix:
Sediment
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Concentrations of Anthracene, fluorene, napthalene, phenanthrene, benz(a)anthracene, benzo(a)pyrene, chrysene, fluoranthrene, pyrene, PAH (total), PCB (total), chlordane, dieldrin, DDD/DDE/DDT, endrin, heptachlor epoxide, and HCH, gamma in one sediment sample collected in spring 2005 did not exceed the sediment quality guidelines.
Insufficient information is available to determine beneficial use support for this waterbody-pollutant combination with the statistical power and confidence required by the Listing Policy. Beneficial use support will be reassessed in a future cycle, if more data are available.
Regional Board Decision Recommendation:
After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list. The readily available data and information is insufficient to determine, with the power and confidence of the Listing Policy, the applicable beneficial use support rating.
State Board Review of Regional Board Conclusion and Recommendation:
State Board Decision Recommendation:
After review of the available data and information, SWRCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list because it cannot be determined if applicable water quality standards are not being exceeded.
Listing Extent:
Line of Evidence (LOE) for Decision ID 141723, Pyrene
Region 2
Arroyo Las Positas
LOE ID:
290113
Pollutant:
Pyrene
LOE Subgroup:
Pollutant-Sediment
Matrix:
Sediment
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Concentrations of Anthracene, fluorene, napthalene, phenanthrene, benz(a)anthracene, benzo(a)pyrene, chrysene, fluoranthrene, pyrene, PAH (total), PCB (total), chlordane, dieldrin, DDD/DDE/DDT, endrin, heptachlor epoxide, and HCH, gamma in one sediment sample collected in spring 2005 did not exceed the sediment quality guidelines.
Do Not List on 303(d) list (TMDL required list)(2018)
Revision Status
Revised
Impairment from Pollutant or Pollution:
Pollutant
Regional Board Conclusion:
Insufficient information is available to determine beneficial use support for this waterbody-pollutant combination with the statistical power and confidence required by the Listing Policy. Beneficial use support will be reassessed in a future cycle, if more data are available.
Regional Board Decision Recommendation:
After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list. The readily available data and information is insufficient to determine, with the power and confidence of the Listing Policy, the applicable beneficial use support rating.
State Board Review of Regional Board Conclusion and Recommendation:
State Board Decision Recommendation:
After review of the available data and information, SWRCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list because it cannot be determined if applicable water quality standards are not being exceeded.
Listing Extent:
Selenium exceeded the Basin Plan chronic water quality objective in 2 spring samples out of 6 samples analyzed. There are high concentrations in native soils and data are now 15 years old (2001-2002). There is no fish tissue data available to confirm water quality impairment. Additional data should be collected to confirm impairment status.
Line of Evidence (LOE) for Decision ID 141724, Selenium
Region 2
Arroyo Las Positas
LOE ID:
28928
Pollutant:
Selenium, Total
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
6
Number of Exceedances:
2
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
The Arroyo Las Positas Creek watershed was monitored as part of SWAMP assessment. Two of the six samples exceeded the chronic water quality objective for selenium, both during the spring sampling. ALP010 at 5.13 ug/L (1.02 chronic exceedence factor), and ALP100 at 8.6 ug/L (1.72 chronic exceedence factor).
All waters shall be maintained free of toxic substances that are lethal to or that produce other detrimental responses in aquatic organisms.
Table 3-4 in the Basin Plan (2007) lists freshwater water quality objectives for toxic pollutants: selenium 5 ug/L 4-day average (chronic) and 20 ug/L 1-hour (acute) WQOs.
Data were collected at three sampling locations on Arroyo Las Positas Creek - ALP010 (El Charro), ALP100 (Altamont Creek), and ALP110 (Arroyo Las Positas).
Temporal Representation:
Samples were collected at all three sites during spring and dry seasons of the 2001-2002 sampling season.
Environmental Conditions:
QAPP Information:
All samples were collected and analyzed using procedures comparable with the SWAMP Quality Assurance Management Plan (SWRCB, 2002).
Line of Evidence (LOE) for Decision ID 141724, Selenium
Region 2
Arroyo Las Positas
LOE ID:
287787
Pollutant:
Selenium
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Dissolved
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed SWAMP RWB2 Monitoring data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Selenium.
The selenium criterion continuous concentration (expressed as a 4-day average) to protect aquatic life in freshwater is 5 ug/L (California Toxics Rule, 2000).
Line of Evidence (LOE) for Decision ID 141724, Selenium
Region 2
Arroyo Las Positas
LOE ID:
287501
Pollutant:
Selenium
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Dissolved
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed SWAMP RWB2 Monitoring data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Selenium.
The selenium criterion continuous concentration (expressed as a 4-day average) to protect aquatic life in freshwater is 5 ug/L (California Toxics Rule, 2000).
Do Not List on 303(d) list (TMDL required list)(2018)
Revision Status
Revised
Impairment from Pollutant or Pollution:
Pollutant
Regional Board Conclusion:
Insufficient information is available to determine beneficial use support for this waterbody-pollutant combination with the statistical power and confidence required by the Listing Policy. Beneficial use support will be reassessed in a future cycle, if more data are available.
Regional Board Decision Recommendation:
After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list. The readily available data and information is insufficient to determine, with the power and confidence of the Listing Policy, the applicable beneficial use support rating.
State Board Review of Regional Board Conclusion and Recommendation:
State Board Decision Recommendation:
After review of the available data and information, SWRCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list because it cannot be determined if applicable water quality standards are not being exceeded.
Listing Extent:
Selenium exceeded the Basin Plan chronic water quality objective in 2 spring samples out of 6 samples analyzed. There are high concentrations in native soils and data are now 15 years old (2001-2002). There is no fish tissue data available to confirm water quality impairment. Additional data should be collected to confirm impairment status.
Line of Evidence (LOE) for Decision ID 141724, Selenium
Region 2
Arroyo Las Positas
LOE ID:
28928
Pollutant:
Selenium, Total
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
6
Number of Exceedances:
2
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
The Arroyo Las Positas Creek watershed was monitored as part of SWAMP assessment. Two of the six samples exceeded the chronic water quality objective for selenium, both during the spring sampling. ALP010 at 5.13 ug/L (1.02 chronic exceedence factor), and ALP100 at 8.6 ug/L (1.72 chronic exceedence factor).
All waters shall be maintained free of toxic substances that are lethal to or that produce other detrimental responses in aquatic organisms.
Table 3-4 in the Basin Plan (2007) lists freshwater water quality objectives for toxic pollutants: selenium 5 ug/L 4-day average (chronic) and 20 ug/L 1-hour (acute) WQOs.
Data were collected at three sampling locations on Arroyo Las Positas Creek - ALP010 (El Charro), ALP100 (Altamont Creek), and ALP110 (Arroyo Las Positas).
Temporal Representation:
Samples were collected at all three sites during spring and dry seasons of the 2001-2002 sampling season.
Environmental Conditions:
QAPP Information:
All samples were collected and analyzed using procedures comparable with the SWAMP Quality Assurance Management Plan (SWRCB, 2002).
Line of Evidence (LOE) for Decision ID 141724, Selenium
Region 2
Arroyo Las Positas
LOE ID:
287787
Pollutant:
Selenium
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Dissolved
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed SWAMP RWB2 Monitoring data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Selenium.
The selenium criterion continuous concentration (expressed as a 4-day average) to protect aquatic life in freshwater is 5 ug/L (California Toxics Rule, 2000).
Line of Evidence (LOE) for Decision ID 141724, Selenium
Region 2
Arroyo Las Positas
LOE ID:
287501
Pollutant:
Selenium
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Dissolved
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed SWAMP RWB2 Monitoring data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Selenium.
The selenium criterion continuous concentration (expressed as a 4-day average) to protect aquatic life in freshwater is 5 ug/L (California Toxics Rule, 2000).
Insufficient information is available to determine beneficial use support for this waterbody-pollutant combination with the statistical power and confidence required by the Listing Policy. Beneficial use support will be reassessed in a future cycle, if more data are available.
Regional Board Decision Recommendation:
After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list. The readily available data and information is insufficient to determine, with the power and confidence of the Listing Policy, the applicable beneficial use support rating.
State Board Review of Regional Board Conclusion and Recommendation:
State Board Decision Recommendation:
After review of this Regional Board decision, SWRCB staff recommend the decision be approved by the State Board.
Listing Extent:
Line of Evidence (LOE) for Decision ID 141725, Silver
Region 2
Arroyo Las Positas
LOE ID:
290159
Pollutant:
Silver
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Dissolved
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
6
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
The Arroyo Las Positas Creek watershed was monitored as part of SWAMP assessment. None of the six samples exceeded the water quality objectives for arsenic, chromium VI, copper, lead, nickel, silver and zinc.Concentrations of total dissolved chromium were well below the objective for chromium VI.
All waters shall be maintained free of toxic substances that are lethal to or that produce other detrimental responses in aquatic organisms. Table 3-4 in the Basin Plan (2007) lists freshwater water quality objectives for toxic pollutants: arsenic- 150 ug/L, chromium VI- 11 ug/L, copper - 9.0 ug/L, lead - 2.5 ug/L; nickel - 52 ug/L, silver-3.4 ug/L and zinc - 120 ug/L.
Data were collected at three sampling locations on Arroyo Las Positas Creek - ALP010 (El Charro), ALP100 (Altamont Creek), and ALP110 (Arroyo Las Positas).
Temporal Representation:
Samples were collected at all three sites during spring and dry seasons of the 2001-2002 sampling season.
Environmental Conditions:
QAPP Information:
All samples were collected and analyzed using procedures comparable with the SWAMP Quality Assurance Management Plan (SWRCB, 2002).
Line of Evidence (LOE) for Decision ID 141725, Silver
Region 2
Arroyo Las Positas
LOE ID:
288020
Pollutant:
Silver
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Dissolved
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed SWAMP RWB2 Monitoring data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Silver.
The dissolved silver criterion maximum concentration (CMC) to protect aquatic life in freshwater is hardnesss dependent. The criterion when calculated using a default hardness of 100 mg/L is 3.4 ug/L. This criterion was divided by 2 in order to better represent a CMC value as specified in footnote (g) of Table (b)(1) of the California Toxics Rule, 2000.
Line of Evidence (LOE) for Decision ID 141725, Silver
Region 2
Arroyo Las Positas
LOE ID:
288038
Pollutant:
Silver
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Dissolved
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed SWAMP RWB2 Monitoring data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Silver.
The dissolved silver criterion maximum concentration (CMC) to protect aquatic life in freshwater is hardnesss dependent. The criterion when calculated using a default hardness of 100 mg/L is 3.4 ug/L. This criterion was divided by 2 in order to better represent a CMC value as specified in footnote (g) of Table (b)(1) of the California Toxics Rule, 2000.
Insufficient information is available to determine beneficial use support for this waterbody-pollutant combination with the statistical power and confidence required by the Listing Policy. Beneficial use support will be reassessed in a future cycle, if more data are available.
Regional Board Decision Recommendation:
After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list. The readily available data and information is insufficient to determine, with the power and confidence of the Listing Policy, the applicable beneficial use support rating.
State Board Review of Regional Board Conclusion and Recommendation:
State Board Decision Recommendation:
After review of this Regional Board decision, SWRCB staff recommend the decision be approved by the State Board.
Listing Extent:
Line of Evidence (LOE) for Decision ID 141725, Silver
Region 2
Arroyo Las Positas
LOE ID:
290159
Pollutant:
Silver
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Dissolved
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
6
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
The Arroyo Las Positas Creek watershed was monitored as part of SWAMP assessment. None of the six samples exceeded the water quality objectives for arsenic, chromium VI, copper, lead, nickel, silver and zinc.Concentrations of total dissolved chromium were well below the objective for chromium VI.
All waters shall be maintained free of toxic substances that are lethal to or that produce other detrimental responses in aquatic organisms. Table 3-4 in the Basin Plan (2007) lists freshwater water quality objectives for toxic pollutants: arsenic- 150 ug/L, chromium VI- 11 ug/L, copper - 9.0 ug/L, lead - 2.5 ug/L; nickel - 52 ug/L, silver-3.4 ug/L and zinc - 120 ug/L.
Data were collected at three sampling locations on Arroyo Las Positas Creek - ALP010 (El Charro), ALP100 (Altamont Creek), and ALP110 (Arroyo Las Positas).
Temporal Representation:
Samples were collected at all three sites during spring and dry seasons of the 2001-2002 sampling season.
Environmental Conditions:
QAPP Information:
All samples were collected and analyzed using procedures comparable with the SWAMP Quality Assurance Management Plan (SWRCB, 2002).
Line of Evidence (LOE) for Decision ID 141725, Silver
Region 2
Arroyo Las Positas
LOE ID:
288020
Pollutant:
Silver
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Dissolved
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed SWAMP RWB2 Monitoring data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Silver.
The dissolved silver criterion maximum concentration (CMC) to protect aquatic life in freshwater is hardnesss dependent. The criterion when calculated using a default hardness of 100 mg/L is 3.4 ug/L. This criterion was divided by 2 in order to better represent a CMC value as specified in footnote (g) of Table (b)(1) of the California Toxics Rule, 2000.
Line of Evidence (LOE) for Decision ID 141725, Silver
Region 2
Arroyo Las Positas
LOE ID:
288038
Pollutant:
Silver
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Dissolved
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed SWAMP RWB2 Monitoring data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Silver.
The dissolved silver criterion maximum concentration (CMC) to protect aquatic life in freshwater is hardnesss dependent. The criterion when calculated using a default hardness of 100 mg/L is 3.4 ug/L. This criterion was divided by 2 in order to better represent a CMC value as specified in footnote (g) of Table (b)(1) of the California Toxics Rule, 2000.
Insufficient information is available to determine beneficial use support for this waterbody-pollutant combination with the statistical power and confidence required by the Listing Policy. Beneficial use support will be reassessed in a future cycle, if more data are available.
Regional Board Decision Recommendation:
After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list. The readily available data and information is insufficient to determine, with the power and confidence of the Listing Policy, the applicable beneficial use support rating.
State Board Review of Regional Board Conclusion and Recommendation:
State Board Decision Recommendation:
After review of this Regional Board decision, SWRCB staff recommend the decision be approved by the State Board.
Listing Extent:
Line of Evidence (LOE) for Decision ID 141727, Thiobencarb/Bolero
Region 2
Arroyo Las Positas
LOE ID:
290197
Pollutant:
Thiobencarb/Bolero
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
None
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
The Arroyo Las Positas Creek watershed was monitored as part of SWAMP assessment. Neither sample exceeded the water quality objectives for Chlorpyrifos, Dacthal, diazinon, disulfoton, endosulfan, Lindane/gamma Hexachlorocyclohexane (gamma-HCH), methyl parathion, thiobencarb.
All waters shall be maintained free of toxic substances that are lethal to or that produce other detrimental responses in aquatic organisms. There shall be no chronic toxicity in ambient waters. Chronic toxicity is a detrimental biological effect on growth rate, reproduction, fertilization success, larval development, population abundance, community composition, or any other relevant measure of the health of an organism, population, or community.Diazinon water quality objective, 0.1 ug/L (acute)
Insufficient information is available to determine beneficial use support for this waterbody-pollutant combination with the statistical power and confidence required by the Listing Policy. Beneficial use support will be reassessed in a future cycle, if more data are available.
Regional Board Decision Recommendation:
After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list. The readily available data and information is insufficient to determine, with the power and confidence of the Listing Policy, the applicable beneficial use support rating.
State Board Review of Regional Board Conclusion and Recommendation:
State Board Decision Recommendation:
After review of this Regional Board decision, SWRCB staff recommend the decision be approved by the State Board.
Listing Extent:
Line of Evidence (LOE) for Decision ID 141727, Thiobencarb/Bolero
Region 2
Arroyo Las Positas
LOE ID:
290197
Pollutant:
Thiobencarb/Bolero
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
None
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
The Arroyo Las Positas Creek watershed was monitored as part of SWAMP assessment. Neither sample exceeded the water quality objectives for Chlorpyrifos, Dacthal, diazinon, disulfoton, endosulfan, Lindane/gamma Hexachlorocyclohexane (gamma-HCH), methyl parathion, thiobencarb.
All waters shall be maintained free of toxic substances that are lethal to or that produce other detrimental responses in aquatic organisms. There shall be no chronic toxicity in ambient waters. Chronic toxicity is a detrimental biological effect on growth rate, reproduction, fertilization success, larval development, population abundance, community composition, or any other relevant measure of the health of an organism, population, or community.Diazinon water quality objective, 0.1 ug/L (acute)
Insufficient information is available to determine beneficial use support for this waterbody-pollutant combination with the statistical power and confidence required by the Listing Policy. Beneficial use support will be reassessed in a future cycle, if more data are available.
Regional Board Decision Recommendation:
After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list. The readily available data and information is insufficient to determine, with the power and confidence of the Listing Policy, the applicable beneficial use support rating.
State Board Review of Regional Board Conclusion and Recommendation:
State Board Decision Recommendation:
After review of this Regional Board decision, SWRCB staff recommend the decision be approved by the State Board.
Listing Extent:
Line of Evidence (LOE) for Decision ID 141728, Turbidity
Region 2
Arroyo Las Positas
LOE ID:
289455
Pollutant:
Turbidity
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
6
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed SWAMP RWB2 Monitoring data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 6 samples exceeded the water quality threshold for Turbidity.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
Sigler et al. (1984) states that turbidities of 25 NTUs or greater caused reduction in juvenile salmonid growth due to interference with their ability to find food. The application of this evaluation guideline was restricted to the dry season (May to October) because Coho and steelhead early life stages are present during the dry season and feeding becomes infrequent during the winter months (Moyle 2002). Additionally, runoff and resuspension of fine substrate during storm events may naturally elevate turbidity compared to baseflow conditions. The magnitude and duration of these increases will vary depending on the watershed’s geology and land use and may not represent a chronic turbidity problem. Turbidity is naturally higher in tidal river systems, so sample locations with salinity regimes (i.e., Freshwater or Marine) designated as “Marine” were excluded from this analysis.
Line of Evidence (LOE) for Decision ID 141728, Turbidity
Region 2
Arroyo Las Positas
LOE ID:
302908
Pollutant:
Turbidity
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
5
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed SWAMP RWB2 Monitoring data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 5 samples exceeded the water quality threshold for Turbidity.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
Turbidities of 40 NTU or greater can cause a reduced foraging efficiency and a shift in prey selection in piscivorous fish (largemouth bass) due to interference with their ability to find prey (Shoup, D.E. and Wahl D.H., 2009). The application of this evaluation guideline was restricted to the dry season (May to October) because runoff and resuspension of fine substrate during storm events may naturally elevate turbidity compared to baseflow conditions. The magnitude and duration of these increases will vary depending on the watershed’s geology and land use and may not represent a chronic turbidity problem. Turbidity is naturally higher in tidal river systems, so sample locations with salinity regimes (i.e., Freshwater or Marine) designated as “Marine” were excluded from this analysis.
The samples were collected at 1 monitoring site: 204ALP075 (Arroyo las Positas at Paseo Laguna Seco apartments).
Temporal Representation:
The samples were collected between the dates of 2018-05-10 and 2019-08-26
Environmental Conditions:
QAPP Information:
DECISION ID
141728
Region 2
Arroyo Las Positas
Pollutant:
Turbidity
Final Listing Decision:
Do Not List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:
New Decision
Revision Status
Revised
Impairment from Pollutant or Pollution:
Pollutant
Regional Board Conclusion:
Insufficient information is available to determine beneficial use support for this waterbody-pollutant combination with the statistical power and confidence required by the Listing Policy. Beneficial use support will be reassessed in a future cycle, if more data are available.
Regional Board Decision Recommendation:
After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list. The readily available data and information is insufficient to determine, with the power and confidence of the Listing Policy, the applicable beneficial use support rating.
State Board Review of Regional Board Conclusion and Recommendation:
State Board Decision Recommendation:
After review of this Regional Board decision, SWRCB staff recommend the decision be approved by the State Board.
Listing Extent:
Line of Evidence (LOE) for Decision ID 141728, Turbidity
Region 2
Arroyo Las Positas
LOE ID:
289455
Pollutant:
Turbidity
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
6
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed SWAMP RWB2 Monitoring data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 6 samples exceeded the water quality threshold for Turbidity.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
Sigler et al. (1984) states that turbidities of 25 NTUs or greater caused reduction in juvenile salmonid growth due to interference with their ability to find food. The application of this evaluation guideline was restricted to the dry season (May to October) because Coho and steelhead early life stages are present during the dry season and feeding becomes infrequent during the winter months (Moyle 2002). Additionally, runoff and resuspension of fine substrate during storm events may naturally elevate turbidity compared to baseflow conditions. The magnitude and duration of these increases will vary depending on the watershed’s geology and land use and may not represent a chronic turbidity problem. Turbidity is naturally higher in tidal river systems, so sample locations with salinity regimes (i.e., Freshwater or Marine) designated as “Marine” were excluded from this analysis.
Line of Evidence (LOE) for Decision ID 141728, Turbidity
Region 2
Arroyo Las Positas
LOE ID:
302908
Pollutant:
Turbidity
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
5
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed SWAMP RWB2 Monitoring data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 5 samples exceeded the water quality threshold for Turbidity.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
Turbidities of 40 NTU or greater can cause a reduced foraging efficiency and a shift in prey selection in piscivorous fish (largemouth bass) due to interference with their ability to find prey (Shoup, D.E. and Wahl D.H., 2009). The application of this evaluation guideline was restricted to the dry season (May to October) because runoff and resuspension of fine substrate during storm events may naturally elevate turbidity compared to baseflow conditions. The magnitude and duration of these increases will vary depending on the watershed’s geology and land use and may not represent a chronic turbidity problem. Turbidity is naturally higher in tidal river systems, so sample locations with salinity regimes (i.e., Freshwater or Marine) designated as “Marine” were excluded from this analysis.
Line of Evidence (LOE) for Decision ID 141728, Turbidity
Region 2
Arroyo Las Positas
LOE ID:
302809
Pollutant:
Turbidity
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed SWAMP RWB2 Monitoring data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Turbidity.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
Turbidities of 40 NTU or greater can cause a reduced foraging efficiency and a shift in prey selection in piscivorous fish (largemouth bass) due to interference with their ability to find prey (Shoup, D.E. and Wahl D.H., 2009). The application of this evaluation guideline was restricted to the dry season (May to October) because runoff and resuspension of fine substrate during storm events may naturally elevate turbidity compared to baseflow conditions. The magnitude and duration of these increases will vary depending on the watershed’s geology and land use and may not represent a chronic turbidity problem. Turbidity is naturally higher in tidal river systems, so sample locations with salinity regimes (i.e., Freshwater or Marine) designated as “Marine” were excluded from this analysis.
Line of Evidence (LOE) for Decision ID 141728, Turbidity
Region 2
Arroyo Las Positas
LOE ID:
302809
Pollutant:
Turbidity
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed SWAMP RWB2 Monitoring data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Turbidity.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
Turbidities of 40 NTU or greater can cause a reduced foraging efficiency and a shift in prey selection in piscivorous fish (largemouth bass) due to interference with their ability to find prey (Shoup, D.E. and Wahl D.H., 2009). The application of this evaluation guideline was restricted to the dry season (May to October) because runoff and resuspension of fine substrate during storm events may naturally elevate turbidity compared to baseflow conditions. The magnitude and duration of these increases will vary depending on the watershed’s geology and land use and may not represent a chronic turbidity problem. Turbidity is naturally higher in tidal river systems, so sample locations with salinity regimes (i.e., Freshwater or Marine) designated as “Marine” were excluded from this analysis.
Line of Evidence (LOE) for Decision ID 141728, Turbidity
Region 2
Arroyo Las Positas
LOE ID:
302752
Pollutant:
Turbidity
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
6
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed SWAMP RWB2 Monitoring data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 6 samples exceeded the water quality threshold for Turbidity.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
Turbidities of 40 NTU or greater can cause a reduced foraging efficiency and a shift in prey selection in piscivorous fish (largemouth bass) due to interference with their ability to find prey (Shoup, D.E. and Wahl D.H., 2009). The application of this evaluation guideline was restricted to the dry season (May to October) because runoff and resuspension of fine substrate during storm events may naturally elevate turbidity compared to baseflow conditions. The magnitude and duration of these increases will vary depending on the watershed’s geology and land use and may not represent a chronic turbidity problem. Turbidity is naturally higher in tidal river systems, so sample locations with salinity regimes (i.e., Freshwater or Marine) designated as “Marine” were excluded from this analysis.
Line of Evidence (LOE) for Decision ID 141728, Turbidity
Region 2
Arroyo Las Positas
LOE ID:
302846
Pollutant:
Turbidity
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
10
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed SWAMP RWB2 Monitoring data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 10 samples exceeded the water quality threshold for Turbidity.
Water Board staff assessed SWAMP RWB2 Monitoring data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 6 samples exceeded the water quality threshold for Turbidity.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
Turbidities of 40 NTU or greater can cause a reduced foraging efficiency and a shift in prey selection in piscivorous fish (largemouth bass) due to interference with their ability to find prey (Shoup, D.E. and Wahl D.H., 2009). The application of this evaluation guideline was restricted to the dry season (May to October) because runoff and resuspension of fine substrate during storm events may naturally elevate turbidity compared to baseflow conditions. The magnitude and duration of these increases will vary depending on the watershed’s geology and land use and may not represent a chronic turbidity problem. Turbidity is naturally higher in tidal river systems, so sample locations with salinity regimes (i.e., Freshwater or Marine) designated as “Marine” were excluded from this analysis.
Line of Evidence (LOE) for Decision ID 141728, Turbidity
Region 2
Arroyo Las Positas
LOE ID:
302846
Pollutant:
Turbidity
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
10
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed SWAMP RWB2 Monitoring data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 10 samples exceeded the water quality threshold for Turbidity.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
Turbidities of 40 NTU or greater can cause a reduced foraging efficiency and a shift in prey selection in piscivorous fish (largemouth bass) due to interference with their ability to find prey (Shoup, D.E. and Wahl D.H., 2009). The application of this evaluation guideline was restricted to the dry season (May to October) because runoff and resuspension of fine substrate during storm events may naturally elevate turbidity compared to baseflow conditions. The magnitude and duration of these increases will vary depending on the watershed’s geology and land use and may not represent a chronic turbidity problem. Turbidity is naturally higher in tidal river systems, so sample locations with salinity regimes (i.e., Freshwater or Marine) designated as “Marine” were excluded from this analysis.
Line of Evidence (LOE) for Decision ID 141728, Turbidity
Region 2
Arroyo Las Positas
LOE ID:
289454
Pollutant:
Turbidity
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
10
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed SWAMP RWB2 Monitoring data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 10 samples exceeded the water quality threshold for Turbidity.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
Sigler et al. (1984) states that turbidities of 25 NTUs or greater caused reduction in juvenile salmonid growth due to interference with their ability to find food. The application of this evaluation guideline was restricted to the dry season (May to October) because Coho and steelhead early life stages are present during the dry season and feeding becomes infrequent during the winter months (Moyle 2002). Additionally, runoff and resuspension of fine substrate during storm events may naturally elevate turbidity compared to baseflow conditions. The magnitude and duration of these increases will vary depending on the watershed’s geology and land use and may not represent a chronic turbidity problem. Turbidity is naturally higher in tidal river systems, so sample locations with salinity regimes (i.e., Freshwater or Marine) designatedgn="left" valign="top" width="67%">SWAMP
Water Quality Objective/Criterion:
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
Turbidities of 40 NTU or greater can cause a reduced foraging efficiency and a shift in prey selection in piscivorous fish (largemouth bass) due to interference with their ability to find prey (Shoup, D.E. and Wahl D.H., 2009). The application of this evaluation guideline was restricted to the dry season (May to October) because runoff and resuspension of fine substrate during storm events may naturally elevate turbidity compared to baseflow conditions. The magnitude and duration of these increases will vary depending on the watershed’s geology and land use and may not represent a chronic turbidity problem. Turbidity is naturally higher in tidal river systems, so sample locations with salinity regimes (i.e., Freshwater or Marine) designated as “Marine” were excluded from this analysis.
Line of Evidence (LOE) for Decision ID 141728, Turbidity
Region 2
Arroyo Las Positas
LOE ID:
289454
Pollutant:
Turbidity
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
10
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed SWAMP RWB2 Monitoring data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 10 samples exceeded the water quality threshold for Turbidity.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
Sigler et al. (1984) states that turbidities of 25 NTUs or greater caused reduction in juvenile salmonid growth due to interference with their ability to find food. The application of this evaluation guideline was restricted to the dry season (May to October) because Coho and steelhead early life stages are present during the dry season and feeding becomes infrequent during the winter months (Moyle 2002). Additionally, runoff and resuspension of fine substrate during storm events may naturally elevate turbidity compared to baseflow conditions. The magnitude and duration of these increases will vary depending on the watershed’s geology and land use and may not represent a chronic turbidity problem. Turbidity is naturally higher in tidal river systems, so sample locations with salinity regimes (i.e., Freshwater or Marine) designated as “Marine” were excluded from this analysis.
Line of Evidence (LOE) for Decision ID 141728, Turbidity
Region 2
Arroyo Las Positas
LOE ID:
289408
Pollutant:
Turbidity
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
5
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed SWAMP RWB2 Monitoring data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 5 samples exceeded the water quality threshold for Turbidity.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
Sigler et al. (1984) states that turbidities of 25 NTUs or greater caused reduction in juvenile salmonid growth due to interference with their ability to find food. The application of this evaluation guideline was restricted to the dry season (May to October) because Coho and steelhead early life stages are present during the dry season and feeding becomes infrequent during the winter months (Moyle 2002). Additionally, runoff and resuspension of fine substrate during storm events may naturally elevate turbidity compared to baseflow conditions. The magnitude and duration of these increases will vary depending on the watershed’s geology and land use and may not represent a chronic turbidity problem. Turbidity is naturally higher in tidal river systems, so sample locations with salinity regimes (i.e., Freshwater or Marine) designated as “Marine” were excluded from this analysis.
Line of Evidence (LOE) for Decision ID 141728, Turbidity
Region 2
Arroyo Las Positas
LOE ID:
289408
Pollutant:
Turbidity
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
5
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed SWAMP RWB2 Monitoring data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 5 samples exceeded the water quality threshold for Turbidity.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
Sigler et al. (1984) states that turbidities of 25 NTUs or greater caused reduction in juvenile salmonid growth due to interference with their ability to find food. The application of this evaluation guideline was restricted to the dry season (May to October) because Coho and steelhead early life stages are present during the dry season and feeding becomes infrequent during the winter months (Moyle 2002). Additionally, runoff and resuspension of fine substrate during storm events may naturally elevate turbidity compared to baseflow conditions. The magnitude and duration of these increases will vary depending on the watershed’s geology and land use and may not represent a chronic turbidity problem. Turbidity is naturally higher in tidal river systems, so sample locations with salinity regimes (i.e., Freshwater or Marine) designated as “Marine” were excluded from this analysis.
Line of Evidence (LOE) for Decision ID 141728, Turbidity
Region 2
Arroyo Las Positas
LOE ID:
289341
Pollutant:
Turbidity
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed SWAMP RWB2 Monitoring data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Turbidity.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
Sigler et al. (1984) states that turbidities of 25 NTUs or greater caused reduction in juvenile salmonid growth due to interference with their ability to find food. The application of this evaluation guideline was restricted to the dry season (May to October) because Coho and steelhead early life stages are present during the dry season and feeding becomes infrequent during the winter months (Moyle 2002). Additionally, runoff and resuspension of fine substrate during storm events may naturally elevate turbidity compared to baseflow conditions. The magnitude and duration of these increases will vary depending on the watershed’s geology and land use and may not represent a chronic turbidity problem. Turbidity is naturally higher in tidal river systems, so sample locations with salinity regimes (i.e., Freshwater or Marine) designated as “Marine” were excluded from this analysis.
ign="top" width="67%">SWRCB. 2018. This is a placeholder reference for data that was collected after QAPP requirements were developed, but exempt from the requirements..
Line of Evidence (LOE) for Decision ID 141728, Turbidity
Region 2
Arroyo Las Positas
LOE ID:
289341
Pollutant:
Turbidity
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed SWAMP RWB2 Monitoring data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Turbidity.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
Sigler et al. (1984) states that turbidities of 25 NTUs or greater caused reduction in juvenile salmonid growth due to interference with their ability to find food. The application of this evaluation guideline was restricted to the dry season (May to October) because Coho and steelhead early life stages are present during the dry season and feeding becomes infrequent during the winter months (Moyle 2002). Additionally, runoff and resuspension of fine substrate during storm events may naturally elevate turbidity compared to baseflow conditions. The magnitude and duration of these increases will vary depending on the watershed’s geology and land use and may not represent a chronic turbidity problem. Turbidity is naturally higher in tidal river systems, so sample locations with salinity regimes (i.e., Freshwater or Marine) designated as “Marine” were excluded from this analysis.
Insufficient information is available to determine beneficial use support for this waterbody-pollutant combination with the statistical power and confidence required by the Listing Policy. Beneficial use support will be reassessed in a future cycle, if more data are available.
Regional Board Decision Recommendation:
After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list. The readily available data and information is insufficient to determine, with the power and confidence of the Listing Policy, the applicable beneficial use support rating.
State Board Review of Regional Board Conclusion and Recommendation:
State Board Decision Recommendation:
After review of this Regional Board decision, SWRCB staff recommend the decision be approved by the State Board.
Listing Extent:
Line of Evidence (LOE) for Decision ID 141729, Zinc
Region 2
Arroyo Las Positas
LOE ID:
290131
Pollutant:
Zinc
LOE Subgroup:
Pollutant-Sediment
Matrix:
Sediment
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Concentrations of arsenic, cadmium, copper, lead, mercury and zinc in one sediment sample collected in spring 2005 did not exceed the sediment quality guidelines.
Insufficient information is available to determine beneficial use support for this waterbody-pollutant combination with the statistical power and confidence required by the Listing Policy. Beneficial use support will be reassessed in a future cycle, if more data are available.
Regional Board Decision Recommendation:
After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list. The readily available data and information is insufficient to determine, with the power and confidence of the Listing Policy, the applicable beneficial use support rating.
State Board Review of Regional Board Conclusion and Recommendation:
State Board Decision Recommendation:
After review of this Regional Board decision, SWRCB staff recommend the decision be approved by the State Board.
Listing Extent:
Line of Evidence (LOE) for Decision ID 141729, Zinc
Region 2
Arroyo Las Positas
LOE ID:
290131
Pollutant:
Zinc
LOE Subgroup:
Pollutant-Sediment
Matrix:
Sediment
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Concentrations of arsenic, cadmium, copper, lead, mercury and zinc in one sediment sample collected in spring 2005 did not exceed the sediment quality guidelines.
Line of Evidence (LOE) for Decision ID 141729, Zinc
Region 2
Arroyo Las Positas
LOE ID:
289914
Pollutant:
Zinc
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Dissolved
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed SWAMP RWB2 Monitoring data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Zinc.
The dissolved zinc criterion continuous concentration (expressed as a 4-day average) to protect aquatic life in freshwater is hardness dependent. The criterion when calculated using a default hardness of 100 mg/L is 120 ug/L (California Toxics Rule, 2000).
Line of Evidence (LOE) for Decision ID 141729, Zinc
Region 2
Arroyo Las Positas
LOE ID:
289944
Pollutant:
Zinc
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Dissolved
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed SWAMP RWB2 Monitoring data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Zinc.
The dissolved zinc criterion continuous concentration (expressed as a 4-day average) to protect aquatic life in freshwater is hardness dependent. The criterion when calculated using a default hardness of 100 mg/L is 120 ug/L (California Toxics Rule, 2000).
Line of Evidence (LOE) for Decision ID 141729, Zinc
Region 2
Arroyo Las Positas
LOE ID:
290160
Pollutant:
Zinc
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Dissolved
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
6
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
The Arroyo Las Positas Creek watershed was monitored as part of SWAMP assessment. None of the six samples exceeded the water quality objectives for arsenic, chromium VI, copper, lead, nickel, silver and zinc.Concentrations of total dissolved chromium were well below the objective for chromium VI.
All waters shall be maintained free of toxic substances that are lethal to or that produce other detrimental responses in aquatic organisms. Table 3-4 in the Basin Plan (2007) lists freshwater water quality objectives for toxic pollutants: arsenic- 150 ug/L, chromium VI- 11 ug/L, copper - 9.0 ug/L, lead - 2.5 ug/L; nickel - 52 ug/L, silver-3.4 ug/L and zinc - 120 ug/L.
Data were collected at three sampling locations on Arroyo Las Positas Creek - ALP010 (El Charro), ALP100 (Altamont Creek), and ALP110 (Arroyo Las Positas).
Temporal Representation:
Samples were collected at all three sites during spring and dry seasons of the 2001-2002 sampling season.
Environmental Conditions:
QAPP Information:
All samples were collected and analyzed using procedures comparable with the SWAMP Quality Assurance Management Plan (SWRCB, 2002).
Line of Evidence (LOE) for Decision ID 141729, Zinc
Region 2
Arroyo Las Positas
LOE ID:
289914
Pollutant:
Zinc
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Dissolved
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed SWAMP RWB2 Monitoring data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Zinc.
The dissolved zinc criterion continuous concentration (expressed as a 4-day average) to protect aquatic life in freshwater is hardness dependent. The criterion when calculated using a default hardness of 100 mg/L is 120 ug/L (California Toxics Rule, 2000).
Line of Evidence (LOE) for Decision ID 141729, Zinc
Region 2
Arroyo Las Positas
LOE ID:
289944
Pollutant:
Zinc
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Dissolved
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed SWAMP RWB2 Monitoring data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Zinc.
The dissolved zinc criterion continuous concentration (expressed as a 4-day average) to protect aquatic life in freshwater is hardness dependent. The criterion when calculated using a default hardness of 100 mg/L is 120 ug/L (California Toxics Rule, 2000).
Line of Evidence (LOE) for Decision ID 141729, Zinc
Region 2
Arroyo Las Positas
LOE ID:
290160
Pollutant:
Zinc
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Dissolved
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
6
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
The Arroyo Las Positas Creek watershed was monitored as part of SWAMP assessment. None of the six samples exceeded the water quality objectives for arsenic, chromium VI, copper, lead, nickel, silver and zinc.Concentrations of total dissolved chromium were well below the objective for chromium VI.
All waters shall be maintained free of toxic substances that are lethal to or that produce other detrimental responses in aquatic organisms. Table 3-4 in the Basin Plan (2007) lists freshwater water quality objectives for toxic pollutants: arsenic- 150 ug/L, chromium VI- 11 ug/L, copper - 9.0 ug/L, lead - 2.5 ug/L; nickel - 52 ug/L, silver-3.4 ug/L and zinc - 120 ug/L.
Data were collected at three sampling locations on Arroyo Las Positas Creek - ALP010 (El Charro), ALP100 (Altamont Creek), and ALP110 (Arroyo Las Positas).
Temporal Representation:
Samples were collected at all three sites during spring and dry seasons of the 2001-2002 sampling season.
Environmental Conditions:
QAPP Information:
All samples were collected and analyzed using procedures comparable with the SWAMP Quality Assurance Management Plan (SWRCB, 2002).
This pollutant is being considered for placement on the CWA section 303(d) List under section 3.1 of the Listing Policy. Under section 3.1 a single line of evidence is necessary to assess listing status.
Fifty-eight lines of evidence are available in the administrative record to assess this pollutant. Three of the fourteen ammonia (unionized) and three of thirty total ammonia samples exceed the evaluation guideline.
Based on the readily available data and information, the weight of evidence indicates that there is sufficient justification in favor of placing this water segment-pollutant combination on the CWA section 303(d) List.
This conclusion is based on the staff findings that: 1. The data used satisfies the data quality requirements of section 6.1.4 of the Policy. 2. The data used satisfies the data quantity requirements of section 6.1.5 of the Policy. 3. Three of the fourteen ammonia (unionized) and three of thirty total ammonia samples exceed the evaluation guideline and this exceeds the allowable frequency listed in Table 3.1 of the Listing Policy. 4. Pursuant to section 3.11 of the Listing Policy, no additional data and information are available indicating that standards are not met.
Regional Board Decision Recommendation:
After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should be placed on the section 303(d) list because applicable water quality standards are exceeded and a pollutant contributes to or causes the problem.
State Board Review of Regional Board Conclusion and Recommendation:
State Board Decision Recommendation:
After review of this Regional Board decision, SWRCB staff recommend the decision be approved by the State Board.
Listing Extent:
Line of Evidence (LOE) for Decision ID 150849, Ammonia
Region 2
Arroyo Las Positas
LOE ID:
279264
Pollutant:
Ammonia (Unionized)
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2019 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Ammonia as N, Unionized.
Water Quality Control Plan, San Francisco Bay Basin, Chapter III Water Quality Objectives, Section 3.3.20 Un-Ionized Ammonia: The discharge of wastes shall not cause receiving waters to contain concentrations of un-ionized ammonia in excess 0.025 mg/l (as N), expressed as an annual median.
Line of Evidence (LOE) for Decision ID 150849, Ammonia
Region 2
Arroyo Las Positas
LOE ID:
278480
Pollutant:
Nitrogen, ammonia (Total Ammonia)
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2014 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Ammonia as N.
The Total Ammonia criterion continuous concentration (expressed as a 30-day average) to protect aquatic life in freshwater is Temperature and pH dependent, and was calculated according to the formula listed in the Aquatic Life Ambient Water Quality Criteria for Ammonia - Freshwater 2013 document.
Line of Evidence (LOE) for Decision ID 150849, Ammonia
Region 2
Arroyo Las Positas
LOE ID:
279735
Pollutant:
Ammonia (Unionized)
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed SWAMP RWB2 Monitoring data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Ammonia as N, Unionized.
Water Quality Control Plan, San Francisco Bay Basin, Chapter III Water Quality Objectives, Section 3.3.20 Un-Ionized Ammonia: The discharge of wastes shall not cause receiving waters to contain concentrations of un-ionized ammonia in excess 0.025 mg/l (as N), expressed as an annual median.
Line of Evidence (LOE) for Decision ID 150849, Ammonia
Region 2
Arroyo Las Positas
LOE ID:
279539
Pollutant:
Ammonia (Unionized)
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2016 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Ammonia as N, Unionized.
Water Quality Control Plan, San Francisco Bay Basin, Chapter III Water Quality Objectives, Section 3.3.20 Un-Ionized Ammonia: The discharge of wastes shall not cause receiving waters to contain concentrations of un-ionized ammonia in excess 0.025 mg/l (as N), expressed as an annual median.
Line of Evidence (LOE) for Decision ID 150849, Ammonia
Region 2
Arroyo Las Positas
LOE ID:
279795
Pollutant:
Ammonia (Unionized)
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2016 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Ammonia as N, Unionized.
Water Quality Control Plan, San Francisco Bay Basin, Chapter III Water Quality Objectives, Section 3.3.20 Un-Ionized Ammonia: The discharge of wastes shall not cause receiving waters to contain concentrations of un-ionized ammonia in excess 0.025 mg/l (as N), expressed as an annual median.
Line of Evidence (LOE) for Decision ID 150849, Ammonia
Region 2
Arroyo Las Positas
LOE ID:
279730
Pollutant:
Ammonia (Unionized)
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed SWAMP RWB2 Monitoring data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Ammonia as N, Unionized.
Water Quality Control Plan, San Francisco Bay Basin, Chapter III Water Quality Objectives, Section 3.3.20 Un-Ionized Ammonia: The discharge of wastes shall not cause receiving waters to contain concentrations of un-ionized ammonia in excess 0.025 mg/l (as N), expressed as an annual median.
Line of Evidence (LOE) for Decision ID 150849, Ammonia
Region 2
Arroyo Las Positas
LOE ID:
278673
Pollutant:
Nitrogen, ammonia (Total Ammonia)
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
1
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2015 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 1 of 1 samples exceeded the water quality threshold for Ammonia as N.
The Total Ammonia criterion continuous concentration (expressed as a 30-day average) to protect aquatic life in freshwater is Temperature and pH dependent, and was calculated according to the formula listed in the Aquatic Life Ambient Water Quality Criteria for Ammonia - Freshwater 2013 document.
Line of Evidence (LOE) for Decision ID 150849, Ammonia
Region 2
Arroyo Las Positas
LOE ID:
278169
Pollutant:
Nitrogen, ammonia (Total Ammonia)
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2017 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Ammonia as N.
The Total Ammonia criterion continuous concentration (expressed as a 30-day average) to protect aquatic life in freshwater is Temperature and pH dependent, and was calculated according to the formula listed in the Aquatic Life Ambient Water Quality Criteria for Ammonia - Freshwater 2013 document.
Line of Evidence (LOE) for Decision ID 150849, Ammonia
Region 2
Arroyo Las Positas
LOE ID:
278208
Pollutant:
Nitrogen, ammonia (Total Ammonia)
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2012 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Ammonia as N.
The Total Ammonia criterion continuous concentration (expressed as a 30-day average) to protect aquatic life in freshwater is Temperature and pH dependent, and was calculated according to the formula listed in the Aquatic Life Ambient Water Quality Criteria for Ammonia - Freshwater 2013 document.
Line of Evidence (LOE) for Decision ID 150849, Ammonia
Region 2
Arroyo Las Positas
LOE ID:
278060
Pollutant:
Nitrogen, ammonia (Total Ammonia)
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
6
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed SWAMP RWB2 Monitoring data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 6 samples exceeded the water quality threshold for Ammonia as N.
The Total Ammonia criterion continuous concentration (expressed as a 30-day average) to protect aquatic life in freshwater is Temperature and pH dependent, and was calculated according to the formula listed in the Aquatic Life Ambient Water Quality Criteria for Ammonia - Freshwater 2013 document.
Line of Evidence (LOE) for Decision ID 150849, Ammonia
Region 2
Arroyo Las Positas
LOE ID:
277744
Pollutant:
Nitrogen, ammonia (Total Ammonia)
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
1
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2019 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 1 of 1 samples exceeded the water quality threshold for Ammonia as N.
The Total Ammonia criterion continuous concentration (expressed as a 30-day average) to protect aquatic life in freshwater is Temperature and pH dependent, and was calculated according to the formula listed in the Aquatic Life Ambient Water Quality Criteria for Ammonia - Freshwater 2013 document.
Line of Evidence (LOE) for Decision ID 150849, Ammonia
Region 2
Arroyo Las Positas
LOE ID:
278661
Pollutant:
Nitrogen, ammonia (Total Ammonia)
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
1
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2019 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 1 of 1 samples exceeded the water quality threshold for Ammonia as N.
The Total Ammonia criterion continuous concentration (expressed as a 30-day average) to protect aquatic life in freshwater is Temperature and pH dependent, and was calculated according to the formula listed in the Aquatic Life Ambient Water Quality Criteria for Ammonia - Freshwater 2013 document.
Line of Evidence (LOE) for Decision ID 150849, Ammonia
Region 2
Arroyo Las Positas
LOE ID:
278056
Pollutant:
Nitrogen, ammonia (Total Ammonia)
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2019 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Ammonia as N.
The Total Ammonia criterion continuous concentration (expressed as a 30-day average) to protect aquatic life in freshwater is Temperature and pH dependent, and was calculated according to the formula listed in the Aquatic Life Ambient Water Quality Criteria for Ammonia - Freshwater 2013 document.
Line of Evidence (LOE) for Decision ID 150849, Ammonia
Region 2
Arroyo Las Positas
LOE ID:
277777
Pollutant:
Nitrogen, ammonia (Total Ammonia)
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2014 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Ammonia as N.
The Total Ammonia criterion continuous concentration (expressed as a 30-day average) to protect aquatic life in freshwater is Temperature and pH dependent, and was calculated according to the formula listed in the Aquatic Life Ambient Water Quality Criteria for Ammonia - Freshwater 2013 document.
Line of Evidence (LOE) for Decision ID 150849, Ammonia
Region 2
Arroyo Las Positas
LOE ID:
278722
Pollutant:
Nitrogen, ammonia (Total Ammonia)
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2019 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Ammonia as N.
The Total Ammonia criterion continuous concentration (expressed as a 30-day average) to protect aquatic life in freshwater is Temperature and pH dependent, and was calculated according to the formula listed in the Aquatic Life Ambient Water Quality Criteria for Ammonia - Freshwater 2013 document.
Line of Evidence (LOE) for Decision ID 150849, Ammonia
Region 2
Arroyo Las Positas
LOE ID:
278548
Pollutant:
Nitrogen, ammonia (Total Ammonia)
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
4
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed SWAMP RWB2 Monitoring data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 4 samples exceeded the water quality threshold for Ammonia as N.
The Total Ammonia criterion continuous concentration (expressed as a 30-day average) to protect aquatic life in freshwater is Temperature and pH dependent, and was calculated according to the formula listed in the Aquatic Life Ambient Water Quality Criteria for Ammonia - Freshwater 2013 document.
Line of Evidence (LOE) for Decision ID 150849, Ammonia
Region 2
Arroyo Las Positas
LOE ID:
278059
Pollutant:
Nitrogen, ammonia (Total Ammonia)
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
9
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed SWAMP RWB2 Monitoring data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 9 samples exceeded the water quality threshold for Ammonia as N.
The Total Ammonia criterion continuous concentration (expressed as a 30-day average) to protect aquatic life in freshwater is Temperature and pH dependent, and was calculated according to the formula listed in the Aquatic Life Ambient Water Quality Criteria for Ammonia - Freshwater 2013 document.
Line of Evidence (LOE) for Decision ID 150849, Ammonia
Region 2
Arroyo Las Positas
LOE ID:
278168
Pollutant:
Nitrogen, ammonia (Total Ammonia)
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2017 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Ammonia as N.
The Total Ammonia criterion continuous concentration (expressed as a 30-day average) to protect aquatic life in freshwater is Temperature and pH dependent, and was calculated according to the formula listed in the Aquatic Life Ambient Water Quality Criteria for Ammonia - Freshwater 2013 document.
Line of Evidence (LOE) for Decision ID 150849, Ammonia
Region 2
Arroyo Las Positas
LOE ID:
278591
Pollutant:
Nitrogen, ammonia (Total Ammonia)
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
6
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed SWAMP RWB2 Monitoring data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 6 samples exceeded the water quality threshold for Ammonia as N.
The Total Ammonia criterion continuous concentration (expressed as a 30-day average) to protect aquatic life in freshwater is Temperature and pH dependent, and was calculated according to the formula listed in the Aquatic Life Ambient Water Quality Criteria for Ammonia - Freshwater 2013 document.
Line of Evidence (LOE) for Decision ID 150849, Ammonia
Region 2
Arroyo Las Positas
LOE ID:
277589
Pollutant:
Nitrogen, ammonia (Total Ammonia)
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
1
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2015 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 1 of 1 samples exceeded the water quality threshold for Ammonia as N.
The Total Ammonia criterion continuous concentration (expressed as a 30-day average) to protect aquatic life in freshwater is Temperature and pH dependent, and was calculated according to the formula listed in the Aquatic Life Ambient Water Quality Criteria for Ammonia - Freshwater 2013 document.
Line of Evidence (LOE) for Decision ID 150849, Ammonia
Region 2
Arroyo Las Positas
LOE ID:
278556
Pollutant:
Nitrogen, ammonia (Total Ammonia)
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
9
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed SWAMP RWB2 Monitoring data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 9 samples exceeded the water quality threshold for Ammonia as N.
The Total Ammonia criterion continuous concentration (expressed as a 30-day average) to protect aquatic life in freshwater is Temperature and pH dependent, and was calculated according to the formula listed in the Aquatic Life Ambient Water Quality Criteria for Ammonia - Freshwater 2013 document.
Line of Evidence (LOE) for Decision ID 150849, Ammonia
Region 2
Arroyo Las Positas
LOE ID:
277853
Pollutant:
Nitrogen, ammonia (Total Ammonia)
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2014 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Ammonia as N.
The Total Ammonia criterion continuous concentration (expressed as a 30-day average) to protect aquatic life in freshwater is Temperature and pH dependent, and was calculated according to the formula listed in the Aquatic Life Ambient Water Quality Criteria for Ammonia - Freshwater 2013 document.
Line of Evidence (LOE) for Decision ID 150849, Ammonia
Region 2
Arroyo Las Positas
LOE ID:
278058
Pollutant:
Nitrogen, ammonia (Total Ammonia)
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2020 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Ammonia as N.
The Total Ammonia criterion continuous concentration (expressed as a 30-day average) to protect aquatic life in freshwater is Temperature and pH dependent, and was calculated according to the formula listed in the Aquatic Life Ambient Water Quality Criteria for Ammonia - Freshwater 2013 document.
Line of Evidence (LOE) for Decision ID 150849, Ammonia
Region 2
Arroyo Las Positas
LOE ID:
278478
Pollutant:
Nitrogen, ammonia (Total Ammonia)
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
4
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed SWAMP RWB2 Monitoring data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 4 samples exceeded the water quality threshold for Ammonia as N.
The Total Ammonia criterion continuous concentration (expressed as a 30-day average) to protect aquatic life in freshwater is Temperature and pH dependent, and was calculated according to the formula listed in the Aquatic Life Ambient Water Quality Criteria for Ammonia - Freshwater 2013 document.
Line of Evidence (LOE) for Decision ID 150849, Ammonia
Region 2
Arroyo Las Positas
LOE ID:
278018
Pollutant:
Nitrogen, ammonia (Total Ammonia)
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2014 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Ammonia as N.
The Total Ammonia criterion continuous concentration (expressed as a 30-day average) to protect aquatic life in freshwater is Temperature and pH dependent, and was calculated according to the formula listed in the Aquatic Life Ambient Water Quality Criteria for Ammonia - Freshwater 2013 document.
Line of Evidence (LOE) for Decision ID 150849, Ammonia
Region 2
Arroyo Las Positas
LOE ID:
278536
Pollutant:
Nitrogen, ammonia (Total Ammonia)
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2017 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Ammonia as N.
The Total Ammonia criterion continuous concentration (expressed as a 30-day average) to protect aquatic life in freshwater is Temperature and pH dependent, and was calculated according to the formula listed in the Aquatic Life Ambient Water Quality Criteria for Ammonia - Freshwater 2013 document.
Line of Evidence (LOE) for Decision ID 150849, Ammonia
Region 2
Arroyo Las Positas
LOE ID:
278674
Pollutant:
Nitrogen, ammonia (Total Ammonia)
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2016 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Ammonia as N.
The Total Ammonia criterion continuous concentration (expressed as a 30-day average) to protect aquatic life in freshwater is Temperature and pH dependent, and was calculated according to the formula listed in the Aquatic Life Ambient Water Quality Criteria for Ammonia - Freshwater 2013 document.
The San Francisco Bay Regional Water Quality Board Basin Plan stated that the discharge of wastes shall not cause receiving water to contain concentrations of un-ionized ammonia in excess of 0.025mg/l annual median.For Total Ammonia: EPA's Lifetime Health advisory level for total ammonia is 30.0 mg/L as stated on page 8 of the 2006 edition of the drinking water standards and health advisories. This Advisory Level is defined as the concentration of a chemical in drinking water that is not expected to cause any adverse noncarcinogenic effects for up to ten days of exposure.
Line of Evidence (LOE) for Decision ID 150849, Ammonia
Region 2
Arroyo Las Positas
LOE ID:
278057
Pollutant:
Nitrogen, ammonia (Total Ammonia)
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
1
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2019 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 1 of 1 samples exceeded the water quality threshold for Ammonia as N.
The Total Ammonia criterion continuous concentration (expressed as a 30-day average) to protect aquatic life in freshwater is Temperature and pH dependent, and was calculated according to the formula listed in the Aquatic Life Ambient Water Quality Criteria for Ammonia - Freshwater 2013 document.
Line of Evidence (LOE) for Decision ID 150849, Ammonia
Region 2
Arroyo Las Positas
LOE ID:
279540
Pollutant:
Ammonia (Unionized)
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2017 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Ammonia as N, Unionized.
Water Quality Control Plan, San Francisco Bay Basin, Chapter III Water Quality Objectives, Section 3.3.20 Un-Ionized Ammonia: The discharge of wastes shall not cause receiving waters to contain concentrations of un-ionized ammonia in excess 0.025 mg/l (as N), expressed as an annual median.
Line of Evidence (LOE) for Decision ID 150849, Ammonia
Region 2
Arroyo Las Positas
LOE ID:
279491
Pollutant:
Ammonia (Unionized)
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
1
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2019 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 1 of 1 samples exceeded the water quality threshold for Ammonia as N, Unionized.
Water Quality Control Plan, San Francisco Bay Basin, Chapter III Water Quality Objectives, Section 3.3.20 Un-Ionized Ammonia: The discharge of wastes shall not cause receiving waters to contain concentrations of un-ionized ammonia in excess 0.025 mg/l (as N), expressed as an annual median.
Line of Evidence (LOE) for Decision ID 150849, Ammonia
Region 2
Arroyo Las Positas
LOE ID:
279544
Pollutant:
Ammonia (Unionized)
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
1
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2019 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 1 of 1 samples exceeded the water quality threshold for Ammonia as N, Unionized.
Water Quality Control Plan, San Francisco Bay Basin, Chapter III Water Quality Objectives, Section 3.3.20 Un-Ionized Ammonia: The discharge of wastes shall not cause receiving waters to contain concentrations of un-ionized ammonia in excess 0.025 mg/l (as N), expressed as an annual median.
Line of Evidence (LOE) for Decision ID 150849, Ammonia
Region 2
Arroyo Las Positas
LOE ID:
279268
Pollutant:
Ammonia (Unionized)
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed SWAMP RWB2 Monitoring data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Ammonia as N, Unionized.
Water Quality Control Plan, San Francisco Bay Basin, Chapter III Water Quality Objectives, Section 3.3.20 Un-Ionized Ammonia: The discharge of wastes shall not cause receiving waters to contain concentrations of un-ionized ammonia in excess 0.025 mg/l (as N), expressed as an annual median.
Line of Evidence (LOE) for Decision ID 150849, Ammonia
Region 2
Arroyo Las Positas
LOE ID:
279543
Pollutant:
Ammonia (Unionized)
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
1
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2019 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 1 of 1 samples exceeded the water quality threshold for Ammonia as N, Unionized.
Water Quality Control Plan, San Francisco Bay Basin, Chapter III Water Quality Objectives, Section 3.3.20 Un-Ionized Ammonia: The discharge of wastes shall not cause receiving waters to contain concentrations of un-ionized ammonia in excess 0.025 mg/l (as N), expressed as an annual median.
Line of Evidence (LOE) for Decision ID 150849, Ammonia
Region 2
Arroyo Las Positas
LOE ID:
279304
Pollutant:
Ammonia (Unionized)
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2017 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Ammonia as N, Unionized.
Water Quality Control Plan, San Francisco Bay Basin, Chapter III Water Quality Objectives, Section 3.3.20 Un-Ionized Ammonia: The discharge of wastes shall not cause receiving waters to contain concentrations of un-ionized ammonia in excess 0.025 mg/l (as N), expressed as an annual median.
Line of Evidence (LOE) for Decision ID 150849, Ammonia
Region 2
Arroyo Las Positas
LOE ID:
279387
Pollutant:
Ammonia (Unionized)
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2017 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Ammonia as N, Unionized.
Water Quality Control Plan, San Francisco Bay Basin, Chapter III Water Quality Objectives, Section 3.3.20 Un-Ionized Ammonia: The discharge of wastes shall not cause receiving waters to contain concentrations of un-ionized ammonia in excess 0.025 mg/l (as N), expressed as an annual median.
Line of Evidence (LOE) for Decision ID 150849, Ammonia
Region 2
Arroyo Las Positas
LOE ID:
279807
Pollutant:
Ammonia (Unionized)
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
1
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2015 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 1 of 1 samples exceeded the water quality threshold for Ammonia as N, Unionized.
Water Quality Control Plan, San Francisco Bay Basin, Chapter III Water Quality Objectives, Section 3.3.20 Un-Ionized Ammonia: The discharge of wastes shall not cause receiving waters to contain concentrations of un-ionized ammonia in excess 0.025 mg/l (as N), expressed as an annual median.
Line of Evidence (LOE) for Decision ID 150849, Ammonia
Region 2
Arroyo Las Positas
LOE ID:
279542
Pollutant:
Ammonia (Unionized)
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2019 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Ammonia as N, Unionized.
Water Quality Control Plan, San Francisco Bay Basin, Chapter III Water Quality Objectives, Section 3.3.20 Un-Ionized Ammonia: The discharge of wastes shall not cause receiving waters to contain concentrations of un-ionized ammonia in excess 0.025 mg/l (as N), expressed as an annual median.
Line of Evidence (LOE) for Decision ID 150849, Ammonia
Region 2
Arroyo Las Positas
LOE ID:
279734
Pollutant:
Ammonia (Unionized)
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2020 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Ammonia as N, Unionized.
Water Quality Control Plan, San Francisco Bay Basin, Chapter III Water Quality Objectives, Section 3.3.20 Un-Ionized Ammonia: The discharge of wastes shall not cause receiving waters to contain concentrations of un-ionized ammonia in excess 0.025 mg/l (as N), expressed as an annual median.
Line of Evidence (LOE) for Decision ID 150849, Ammonia
Region 2
Arroyo Las Positas
LOE ID:
279265
Pollutant:
Ammonia (Unionized)
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2020 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Ammonia as N, Unionized.
Water Quality Control Plan, San Francisco Bay Basin, Chapter III Water Quality Objectives, Section 3.3.20 Un-Ionized Ammonia: The discharge of wastes shall not cause receiving waters to contain concentrations of un-ionized ammonia in excess 0.025 mg/l (as N), expressed as an annual median.
Line of Evidence (LOE) for Decision ID 150849, Ammonia
Region 2
Arroyo Las Positas
LOE ID:
279416
Pollutant:
Ammonia (Unionized)
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2014 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Ammonia as N, Unionized.
Water Quality Control Plan, San Francisco Bay Basin, Chapter III Water Quality Objectives, Section 3.3.20 Un-Ionized Ammonia: The discharge of wastes shall not cause receiving waters to contain concentrations of un-ionized ammonia in excess 0.025 mg/l (as N), expressed as an annual median.
Line of Evidence (LOE) for Decision ID 150849, Ammonia
Region 2
Arroyo Las Positas
LOE ID:
278924
Pollutant:
Ammonia (Unionized)
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
1
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2015 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 1 of 1 samples exceeded the water quality threshold for Ammonia as N, Unionized.
Water Quality Control Plan, San Francisco Bay Basin, Chapter III Water Quality Objectives, Section 3.3.20 Un-Ionized Ammonia: The discharge of wastes shall not cause receiving waters to contain concentrations of un-ionized ammonia in excess 0.025 mg/l (as N), expressed as an annual median.
The San Francisco Bay Regional Water Quality Board Basin Plan stated that the discharge of wastes shall not cause receiving water to contain concentrations of un-ionized ammonia in excess of 0.025mg/l annual median.For Total Ammonia: EPA's Lifetime Health advisory level for total ammonia is 30.0 mg/L as stated on page 8 of the 2006 edition of the drinking water standards and health advisories. This Advisory Level is defined as the concentration of a chemical in drinking water that is not expected to cause any adverse noncarcinogenic effects for up to ten days of exposure.
Line of Evidence (LOE) for Decision ID 150849, Ammonia
Region 2
Arroyo Las Positas
LOE ID:
280241
Pollutant:
Ammonia (Unionized)
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2012 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Ammonia as N, Unionized.
Water Quality Control Plan, San Francisco Bay Basin, Chapter III Water Quality Objectives, Section 3.3.20 Un-Ionized Ammonia: The discharge of wastes shall not cause receiving waters to contain concentrations of un-ionized ammonia in excess 0.025 mg/l (as N), expressed as an annual median.
Line of Evidence (LOE) for Decision ID 150849, Ammonia
Region 2
Arroyo Las Positas
LOE ID:
279987
Pollutant:
Ammonia (Unionized)
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2014 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Ammonia as N, Unionized.
Water Quality Control Plan, San Francisco Bay Basin, Chapter III Water Quality Objectives, Section 3.3.20 Un-Ionized Ammonia: The discharge of wastes shall not cause receiving waters to contain concentrations of un-ionized ammonia in excess 0.025 mg/l (as N), expressed as an annual median.
Line of Evidence (LOE) for Decision ID 150849, Ammonia
Region 2
Arroyo Las Positas
LOE ID:
279755
Pollutant:
Ammonia (Unionized)
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed SWAMP RWB2 Monitoring data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Ammonia as N, Unionized.
Water Quality Control Plan, San Francisco Bay Basin, Chapter III Water Quality Objectives, Section 3.3.20 Un-Ionized Ammonia: The discharge of wastes shall not cause receiving waters to contain concentrations of un-ionized ammonia in excess 0.025 mg/l (as N), expressed as an annual median.
Line of Evidence (LOE) for Decision ID 150849, Ammonia
Region 2
Arroyo Las Positas
LOE ID:
280288
Pollutant:
Ammonia (Unionized)
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2014 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Ammonia as N, Unionized.
Water Quality Control Plan, San Francisco Bay Basin, Chapter III Water Quality Objectives, Section 3.3.20 Un-Ionized Ammonia: The discharge of wastes shall not cause receiving waters to contain concentrations of un-ionized ammonia in excess 0.025 mg/l (as N), expressed as an annual median.
Line of Evidence (LOE) for Decision ID 150849, Ammonia
Region 2
Arroyo Las Positas
LOE ID:
279417
Pollutant:
Ammonia (Unionized)
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2014 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Ammonia as N, Unionized.
Water Quality Control Plan, San Francisco Bay Basin, Chapter III Water Quality Objectives, Section 3.3.20 Un-Ionized Ammonia: The discharge of wastes shall not cause receiving waters to contain concentrations of un-ionized ammonia in excess 0.025 mg/l (as N), expressed as an annual median.
Line of Evidence (LOE) for Decision ID 150849, Ammonia
Region 2
Arroyo Las Positas
LOE ID:
279736
Pollutant:
Ammonia (Unionized)
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed SWAMP RWB2 Monitoring data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Ammonia as N, Unionized.
Water Quality Control Plan, San Francisco Bay Basin, Chapter III Water Quality Objectives, Section 3.3.20 Un-Ionized Ammonia: The discharge of wastes shall not cause receiving waters to contain concentrations of un-ionized ammonia in excess 0.025 mg/l (as N), expressed as an annual median.
Line of Evidence (LOE) for Decision ID 150849, Ammonia
Region 2
Arroyo Las Positas
LOE ID:
279267
Pollutant:
Ammonia (Unionized)
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed SWAMP RWB2 Monitoring data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Ammonia as N, Unionized.
Water Quality Control Plan, San Francisco Bay Basin, Chapter III Water Quality Objectives, Section 3.3.20 Un-Ionized Ammonia: The discharge of wastes shall not cause receiving waters to contain concentrations of un-ionized ammonia in excess 0.025 mg/l (as N), expressed as an annual median.
Line of Evidence (LOE) for Decision ID 150849, Ammonia
Region 2
Arroyo Las Positas
LOE ID:
279470
Pollutant:
Ammonia (Unionized)
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
1
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2019 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 1 of 1 samples exceeded the water quality threshold for Ammonia as N, Unionized.
Water Quality Control Plan, San Francisco Bay Basin, Chapter III Water Quality Objectives, Section 3.3.20 Un-Ionized Ammonia: The discharge of wastes shall not cause receiving waters to contain concentrations of un-ionized ammonia in excess 0.025 mg/l (as N), expressed as an annual median.
Line of Evidence (LOE) for Decision ID 150849, Ammonia
Region 2
Arroyo Las Positas
LOE ID:
279541
Pollutant:
Ammonia (Unionized)
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2017 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Ammonia as N, Unionized.
Water Quality Control Plan, San Francisco Bay Basin, Chapter III Water Quality Objectives, Section 3.3.20 Un-Ionized Ammonia: The discharge of wastes shall not cause receiving waters to contain concentrations of un-ionized ammonia in excess 0.025 mg/l (as N), expressed as an annual median.
Line of Evidence (LOE) for Decision ID 150849, Ammonia
Region 2
Arroyo Las Positas
LOE ID:
278524
Pollutant:
Nitrogen, ammonia (Total Ammonia)
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2020 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Ammonia as N.
The Total Ammonia criterion continuous concentration (expressed as a 30-day average) to protect aquatic life in freshwater is Temperature and pH dependent, and was calculated according to the formula listed in the Aquatic Life Ambient Water Quality Criteria for Ammonia - Freshwater 2013 document.
Line of Evidence (LOE) for Decision ID 150849, Ammonia
Region 2
Arroyo Las Positas
LOE ID:
278746
Pollutant:
Nitrogen, ammonia (Total Ammonia)
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2017 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Ammonia as N.
The Total Ammonia criterion continuous concentration (expressed as a 30-day average) to protect aquatic life in freshwater is Temperature and pH dependent, and was calculated according to the formula listed in the Aquatic Life Ambient Water Quality Criteria for Ammonia - Freshwater 2013 document.
Line of Evidence (LOE) for Decision ID 150849, Ammonia
Region 2
Arroyo Las Positas
LOE ID:
278766
Pollutant:
Nitrogen, ammonia (Total Ammonia)
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
1
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2019 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 1 of 1 samples exceeded the water quality threshold for Ammonia as N.
The Total Ammonia criterion continuous concentration (expressed as a 30-day average) to protect aquatic life in freshwater is Temperature and pH dependent, and was calculated according to the formula listed in the Aquatic Life Ambient Water Quality Criteria for Ammonia - Freshwater 2013 document.
Line of Evidence (LOE) for Decision ID 150849, Ammonia
Region 2
Arroyo Las Positas
LOE ID:
278017
Pollutant:
Nitrogen, ammonia (Total Ammonia)
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2012 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Ammonia as N.
The Total Ammonia criterion continuous concentration (expressed as a 30-day average) to protect aquatic life in freshwater is Temperature and pH dependent, and was calculated according to the formula listed in the Aquatic Life Ambient Water Quality Criteria for Ammonia - Freshwater 2013 document.
Line of Evidence (LOE) for Decision ID 150849, Ammonia
Region 2
Arroyo Las Positas
LOE ID:
277221
Pollutant:
Nitrogen, ammonia (Total Ammonia)
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2016 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Ammonia as N.
The Total Ammonia criterion continuous concentration (expressed as a 30-day average) to protect aquatic life in freshwater is Temperature and pH dependent, and was calculated according to the formula listed in the Aquatic Life Ambient Water Quality Criteria for Ammonia - Freshwater 2013 document.
Line of Evidence (LOE) for Decision ID 150849, Ammonia
Region 2
Arroyo Las Positas
LOE ID:
279269
Pollutant:
Ammonia (Unionized)
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2012 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Ammonia as N, Unionized.
Water Quality Control Plan, San Francisco Bay Basin, Chapter III Water Quality Objectives, Section 3.3.20 Un-Ionized Ammonia: The discharge of wastes shall not cause receiving waters to contain concentrations of un-ionized ammonia in excess 0.025 mg/l (as N), expressed as an annual median.
For the 2024 Integrated Report, USEPA disapproved 44 benthic community effects decisions that were placed in Category 3. The data and information demonstrated that the biological community is degraded, and the waterbody is listed on the 303(d) list with at least one pollutant impairment affecting an aquatic life beneficial use. This was an interim approach used to provide time to develop the methodology to associate the pollutant as a potential cause of the degraded biology. The USEPA reviewed the appropriateness of these category placements and indicated that the most appropriate classification for these 44 waterbody-pollutant combinations is Category 5. This decision was updated to reflect direction from USEPA.
Benthic Community Effects are being considered for placement on the CWA section 303(d) List under sections 3.9 of the Listing Policy. Under section 3.9, additional lines of evidence (LOEs) associating the Benthic Community Effects decision with a water or sediment concentration of pollutants other than benthic-macroinvertebrate bioassessment or habitat assessment LOEs are necessary to place a water body on the 303(d) List for Benthic Community Effects.
Twenty-one line(s) of evidence evaluating benthic-macroinvertebrate bioassessment data is/are available in the administrative record to assess this indicator. Twenty-one of 21 benthic-macroinvertebrate samples exceed the California Stream Condition Index (CSCI) impairment threshold. Additionally, there are associated pollutant impairments on the waterbody (including but not necessarily limited to Ammonia, Chloride, Temperature, and pH). Based on the readily available data and information, the weight of evidence indicates that there is sufficient justification for placing Benthic Community Effects in this waterbody segment on the CWA section 303(d) List.
This conclusion is based on the staff findings that:
1. The data used satisfies the data quality requirements of section 6.1.4 of the Policy. 2. The data used satisfies the data quantity requirements of section 6.1.5 of the Policy. 3. 21 of 21 benthic-macroinvertebrate bioassessment samples had CSCI scores below 0.79. Therefore, this water body is exceeding the water quality threshold for the protection of the WARM and/or COLD beneficial use. 4. Pursuant to section 3.9 of the Listing Policy, the water segment has associated pollutant(s) samples that exceed water quality objectives. 5. Pursuant to section 3.11 of the Listing Policy, no additional data and information are available indicating that standards are not met.
Regional Board Decision Recommendation:
After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list. The readily available data and information is insufficient to determine, with the power and confidence of the Listing Policy, the applicable beneficial use support rating.
State Board Review of Regional Board Conclusion and Recommendation:
State Board Decision Recommendation:
After review of this Regional Board decision, SWRCB staff recommend the decision be approved by the State Board.
Listing Extent:
Line of Evidence (LOE) for Decision ID 154220, Benthic Community Effects
Region 2
Arroyo Las Positas
LOE ID:
306910
Pollutant:
Benthic-Macroinvertebrate Bioassessments
LOE Subgroup:
Population/Community Degradation
Matrix:
Water
Fraction:
None
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
1
Data and Information Type:
Benthic macroinvertebrate surveys
Data Used to Assess Water Quality:
Water Board staff assessed data for 204R00068 to determine beneficial use support and the results are as follows: 1 of 1 samples exceeded the threshold. CSCI scores were from 0.508619 to 0.508619.
All waters shall be maintained free of toxic substances in concentrations that are lethal to or that produce significant alterations in population or community ecology or receiving water biota. In addition, the health and life history characteristics of aquatic organisms in waters affected by controllable water quality factors shall not differ significantly from those for the same waters in areas unaffected by controllable water quality factors.
The California Stream Condition Index (CSCI) is a biological scoring tool that helps aquatic resource managers translate complex data about benthic macroinvertebrates found living in a stream into an overall measure of stream health. The CSCI score is calculated by comparing the expected condition with actual (observed) results (Rehn, A.C. et al., 2015). CSCI scores range from 0 (highly degraded) to greater than 1 (equivalent to reference). CSCI scoring of biological condition are as follows (per the scientific paper supporting the development of the CSCI scoring tool): greater than or equal to 0.92 = likely intact condition, 0.91 to 0.80 = possibly altered condition, 0.79 to 0.63 = likely altered condition, less than or equal to 0.62 = very likely altered condition. Sites with scores below 0.79 are considered to have exceeded the water quality objective for the aquatic life beneficial use.Â
Line of Evidence (LOE) for Decision ID 154220, Benthic Community Effects
Region 2
Arroyo Las Positas
LOE ID:
286949
Pollutant:
pH
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
None
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
1
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2015 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 1 of 1 samples exceeded the water quality threshold for pH.
Water Quality Control Plan, San Francisco Bay Basin, Chapter III Water Quality Objectives, Section 3.3.9 pH states: The pH shall not be depressed below 6.5 nor raised above 8.5. This encompasses the pH range usually found in waters within the basin. Controllable water quality factors shall not cause changes greater than 0.5 units in normal ambient pH levels.
Line of Evidence (LOE) for Decision ID 154220, Benthic Community Effects
Region 2
Arroyo Las Positas
LOE ID:
306696
Pollutant:
Benthic-Macroinvertebrate Bioassessments
LOE Subgroup:
Population/Community Degradation
Matrix:
Water
Fraction:
None
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
1
Data and Information Type:
Benthic macroinvertebrate surveys
Data Used to Assess Water Quality:
Water Board staff assessed data for 204ALP080 to determine beneficial use support and the results are as follows: 1 of 1 samples exceeded the threshold. CSCI scores were from 0.471466909 to 0.471466909.
All waters shall be maintained free of toxic substances in concentrations that are lethal to or that produce significant alterations in population or community ecology or receiving water biota. In addition, the health and life history characteristics of aquatic organisms in waters affected by controllable water quality factors shall not differ significantly from those for the same waters in areas unaffected by controllable water quality factors.
The California Stream Condition Index (CSCI) is a biological scoring tool that helps aquatic resource managers translate complex data about benthic macroinvertebrates found living in a stream into an overall measure of stream health. The CSCI score is calculated by comparing the expected condition with actual (observed) results (Rehn, A.C. et al., 2015). CSCI scores range from 0 (highly degraded) to greater than 1 (equivalent to reference). CSCI scoring of biological condition are as follows (per the scientific paper supporting the development of the CSCI scoring tool): greater than or equal to 0.92 = likely intact condition, 0.91 to 0.80 = possibly altered condition, 0.79 to 0.63 = likely altered condition, less than or equal to 0.62 = very likely altered condition. Sites with scores below 0.79 are considered to have exceeded the water quality objective for the aquatic life beneficial use.Â
Line of Evidence (LOE) for Decision ID 154220, Benthic Community Effects
Region 2
Arroyo Las Positas
LOE ID:
306947
Pollutant:
Benthic-Macroinvertebrate Bioassessments
LOE Subgroup:
Population/Community Degradation
Matrix:
Water
Fraction:
None
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
1
Data and Information Type:
Benthic macroinvertebrate surveys
Data Used to Assess Water Quality:
Water Board staff assessed data for 204ALP105 to determine beneficial use support and the results are as follows: 1 of 1 samples exceeded the threshold. CSCI scores were from 0.308794066 to 0.308794066.
All waters shall be maintained free of toxic substances in concentrations that are lethal to or that produce significant alterations in population or community ecology or receiving water biota. In addition, the health and life history characteristics of aquatic organisms in waters affected by controllable water quality factors shall not differ significantly from those for the same waters in areas unaffected by controllable water quality factors.
The California Stream Condition Index (CSCI) is a biological scoring tool that helps aquatic resource managers translate complex data about benthic macroinvertebrates found living in a stream into an overall measure of stream health. The CSCI score is calculated by comparing the expected condition with actual (observed) results (Rehn, A.C. et al., 2015). CSCI scores range from 0 (highly degraded) to greater than 1 (equivalent to reference). CSCI scoring of biological condition are as follows (per the scientific paper supporting the development of the CSCI scoring tool): greater than or equal to 0.92 = likely intact condition, 0.91 to 0.80 = possibly altered condition, 0.79 to 0.63 = likely altered condition, less than or equal to 0.62 = very likely altered condition. Sites with scores below 0.79 are considered to have exceeded the water quality objective for the aquatic life beneficial use.Â
Line of Evidence (LOE) for Decision ID 154220, Benthic Community Effects
Region 2
Arroyo Las Positas
LOE ID:
306936
Pollutant:
Benthic-Macroinvertebrate Bioassessments
LOE Subgroup:
Population/Community Degradation
Matrix:
DECISION ID
150849
Region 2
Arroyo Las Positas
Pollutant:
Ammonia
Final Listing Decision:
List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:
New Decision
Revision Status
Revised
Sources:
A Source Unknown
TMDL Priority:
Low
Impairment from Pollutant or Pollution:
Pollutant
Regional Board Conclusion:
This pollutant is being considered for placement on the CWA section 303(d) List under section 3.1 of the Listing Policy. Under section 3.1 a single line of evidence is necessary to assess listing status.
Fifty-eight lines of evidence are available in the administrative record to assess this pollutant. Three of the fourteen ammonia (unionized) and three of thirty total ammonia samples exceed the evaluation guideline.
Based on the readily available data and information, the weight of evidence indicates that there is sufficient justification in favor of placing this water segment-pollutant combination on the CWA section 303(d) List.
This conclusion is based on the staff findings that: 1. The data used satisfies the data quality requirements of section 6.1.4 of the Policy. 2. The data used satisfies the data quantity requirements of section 6.1.5 of the Policy. 3. Three of the fourteen ammonia (unionized) and three of thirty total ammonia samples exceed the evaluation guideline and this exceeds the allowable frequency listed in Table 3.1 of the Listing Policy. 4. Pursuant to section 3.11 of the Listing Policy, no additional data and information are available indicating that standards are not met.
Regional Board Decision Recommendation:
After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should be placed on the section 303(d) list because applicable water quality standards are exceeded and a pollutant contributes to or causes the problem.
State Board Review of Regional Board Conclusion and Recommendation:
State Board Decision Recommendation:
After review of this Regional Board decision, SWRCB staff recommend the decision be approved by the State Board.
Listing Extent:
Line of Evidence (LOE) for Decision ID 150849, Ammonia
Region 2
Arroyo Las Positas
LOE ID:
279264
Pollutant:
Ammonia (Unionized)
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2019 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Ammonia as N, Unionized.
Water Board staff assessed data for 204R03737 to determine beneficial use support and the results are as follows: 1 of 1 samples exceeded the threshold. CSCI scores were from 0.24344593 to 0.24344593.
All waters shall be maintained free of toxic substances in concentrations that are lethal to or that produce significant alterations in population or community ecology or receiving water biota. In addition, the health and life history characteristics of aquatic organisms in waters affected by controllable water quality factors shall not differ significantly from those for the same waters in areas unaffected by controllable water quality factors.
The California Stream Condition Index (CSCI) is a biological scoring tool that helps aquatic resource managers translate complex data about benthic macroinvertebrates found living in a stream into an overall measure of stream health. The CSCI score is calculated by comparing the expected condition with actual (observed) results (Rehn, A.C. et al., 2015). CSCI scores range from 0 (highly degraded) to greater than 1 (equivalent to reference). CSCI scoring of biological condition are as follows (per the scientific paper supporting the development of the CSCI scoring tool): greater than or equal to 0.92 = likely intact condition, 0.91 to 0.80 = possibly altered condition, 0.79 to 0.63 = likely altered condition, less than or equal to 0.62 = very likely altered condition. Sites with scores below 0.79 are considered to have exceeded the water quality objective for the aquatic life beneficial use.Â
Line of Evidence (LOE) for Decision ID 154220, Benthic Community Effects
Region 2
Arroyo Las Positas
LOE ID:
306946
Pollutant:
Benthic-Macroinvertebrate Bioassessments
LOE Subgroup:
Population/Community Degradation
Matrix:
Water
Fraction:
None
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
2
Number of Exceedances:
2
Data and Information Type:
Benthic macroinvertebrate surveys
Data Used to Assess Water Quality:
Water Board staff assessed data for 204ALP075 to determine beneficial use support and the results are as follows: 2 of 2 samples exceeded the threshold. CSCI scores were from 0.487324516 to 0.570380695.
Water Quality Objective/7%">Water Quality Control Plan, San Francisco Bay Basin, Chapter III Water Quality Objectives, Section 3.3.20 Un-Ionized Ammonia: The discharge of wastes shall not cause receiving waters to contain concentrations of un-ionized ammonia in excess 0.025 mg/l (as N), expressed as an annual median.
Line of Evidence (LOE) for Decision ID 150849, Ammonia
Region 2
Arroyo Las Positas
LOE ID:
278480
Pollutant:
Nitrogen, ammonia (Total Ammonia)
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2014 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Ammonia as N.
The Total Ammonia criterion continuous concentration (expressed as a 30-day average) to protect aquatic life in freshwater is Temperature and pH dependent, and was calculated according to the formula listed in the Aquatic Life Ambient Water Quality Criteria for Ammonia - Freshwater 2013 document.
Line of Evidence (LOE) for Decision ID 150849, Ammonia
Region 2
Arroyo Las Positas
All waters shall be maintained free of toxic substances in concentrations that are lethal to or that produce significant alterations in population or community ecology or receiving water biota. In addition, the health and life history characteristics of aquatic organisms in waters affected by controllable water quality factors shall not differ significantly from those for the same waters in areas unaffected by controllable water quality factors.
The California Stream Condition Index (CSCI) is a biological scoring tool that helps aquatic resource managers translate complex data about benthic macroinvertebrates found living in a stream into an overall measure of stream health. The CSCI score is calculated by comparing the expected condition with actual (observed) results (Rehn, A.C. et al., 2015). CSCI scores range from 0 (highly degraded) to greater than 1 (equivalent to reference). CSCI scoring of biological condition are as follows (per the scientific paper supporting the development of the CSCI scoring tool): greater than or equal to 0.92 = likely intact condition, 0.91 to 0.80 = possibly altered condition, 0.79 to 0.63 = likely altered condition, less than or equal to 0.62 = very likely altered condition. Sites with scores below 0.79 are considered to have exceeded the water quality objective for the aquatic life beneficial use.Â
Line of Evidence (LOE) for Decision ID 154220, Benthic Community Effects
Region 2
Arroyo Las Positas
LOE ID:
306923
Pollutant:
Benthic-Macroinvertebrate Bioassessments
LOE Subgroup:
Population/Community Degradation
Matrix:
Water
Fraction:
None
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
1
Data and Information Type:
Benthic macroinvertebrate surveys
Data Used to Assess Water Quality:
Water Board staff assessed data for 204R01945 to determine beneficial use support and the results are as follows: 1 of 1 samples exceeded the threshold. CSCI scores were from 0.370353 to 0.370353.
All waters shall be maintained free of toxic substances in concentrations that are lethal to or that produce significant alterations in population or community ecology or receiving water biota. In addition, the health and life history characteristics of aquatic organisms in waters affected by controllable water quality factors shall not differ significantly from those for the same waters in areas unaffected by controllable water quality factors.
The California Stream Condition Index (CSCI) is a biological scoring tool that helps aquatic resource managers translate complex data about benthic macroinvertebrates found living in a stream into an overall measure of stream health. The CSCI score is calculated by comparing the expected condition with actual (observed) results (Rehn, A.C. et al., 2015). CSCI scores range from 0 (highly degraded) to greater than 1 (equivalent to reference). CSCI scoring of biological condition are as follows (per the scientific paper supporting the development of the CSCI scoring tool): greater than or equal to 0.92 = likely intact condition, 0.91 to 0.80 = possibly alter/td>
LOE ID:
279735
Pollutant:
Ammonia (Unionized)
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed SWAMP RWB2 Monitoring data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Ammonia as N, Unionized.
Water Quality Control Plan, San Francisco Bay Basin, Chapter III Water Quality Objectives, Section 3.3.20 Un-Ionized Ammonia: The discharge of wastes shall not cause receiving waters to contain concentrations of un-ionized ammonia in excess 0.025 mg/l (as N), expressed as an annual median.
Line of Evidence (LOE) for Decision ID 150849, Ammonia
Region 2
Arroyo Las Positas
LOE ID:
279539
Pollutant:
Ammonia (Unionized)
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2016 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Ammonia as N, Unionized.
Water Quality Control Plan, San Francisco Bay Basin, Chapter III Water Quality Objectives, Section 3.3.20 Un-Ionized Ammonia: The discharge of wastes shall not cause receiving waters to contain concentrations of un-ionized ammonia in excess 0.025 mg/l (as N), expressed as an annual median.
Line of Evidence (LOE) for Decision ID 154220, Benthic Community Effects
Region 2
Arroyo Las Positas
LOE ID:
306924
Pollutant:
Benthic-Macroinvertebrate Bioassessments
LOE Subgroup:
Population/Community Degradation
Matrix:
Water
Fraction:
None
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
1
Data and Information Type:
Benthic macroinvertebrate surveys
Data Used to Assess Water Quality:
Water Board staff assessed data for 204R02116 to determine beneficial use support and the results are as follows: 1 of 1 samples exceeded the threshold. CSCI scores were from 0.5312 to 0.5312.
All waters shall be maintained free of toxic substances in concentrations that are lethal to or that produce significant alterations in population or community ecology or receiving water biota. In addition, the health and life history characteristics of aquatic organisms in waters affected by controllable water quality factors shall not differ significantly from those for the same waters in areas unaffected by controllable water quality factors.
The California Stream Condition Index (CSCI) is a biological scoring tool that helps aquatic resource managers translate complex data about benthic macroinvertebrates found living in a stream into an overall measure of stream health. The CSCI score is calculated by comparing the expected condition with actual (observed) results (Rehn, A.C. et al., 2015). CSCI scores range from 0 (highly degraded) to greater than 1 (equivalent to reference). CSCI scoring of biological condition are as follows (per the scientific paper supporting the development of the CSCI scoring tool): greater than or equal to 0.92 = likely intact condition, 0.91 to 0.80 = possibly altered condition, 0.79 to 0.63 = likely altered condition, less than or equal to 0.62 = very likely altered condition. Sites with scores below 0.79 are considered to have exceeded the water quality objective for the aquatic life beneficial use.Â
Line of Evidence (LOE) for Decision ID 150849, Ammonia
Region 2
Arroyo Las Positas
LOE ID:
279795
Pollutant:
Ammonia (Unionized)
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2016 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Ammonia as N, Unionized.
Water Quality Control Plan, San Francisco Bay Basin, Chapter III Water Quality Objectives, Section 3.3.20 Un-Ionized Ammonia: The discharge of wastes shall not cause receiving waters to contain concentrations of un-ionized ammonia in excess 0.025 mg/l (as N), expressed as an annual median.
Line of Evidence (LOE) for Decision ID 150849, Ammonia
Region 2
Arroyo Las Positas
LOE ID:
279730
Pollutant:
Ammonia (Unionized)
LOE Subgroup:
Pollutant-Water
Line of Evidence (LOE) for Decision ID 154220, Benthic Community Effects
Region 2
Arroyo Las Positas
LOE ID:
306912
Pollutant:
Benthic-Macroinvertebrate Bioassessments
LOE Subgroup:
Population/Community Degradation
Matrix:
Water
Fraction:
None
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
1
Data and Information Type:
Benthic macroinvertebrate surveys
Data Used to Assess Water Quality:
Water Board staff assessed data for 204R01023 to determine beneficial use support and the results are as follows: 1 of 1 samples exceeded the threshold. CSCI scores were from 0.359973 to 0.359973.
All waters shall be maintained free of toxic substances in concentrations that are lethal to or that produce significant alterations in population or community ecology or receiving water biota. In addition, the health and life history characteristics of aquatic organisms in waters affected by controllable water quality factors shall not differ significantly from those for the same waters in areas unaffected by controllable water quality factors.
The California Stream Condition Index (CSCI) is a biological scoring tool that helps aquatic resource managers translate complex data about benthic macroinvertebrates found living in a stream into an overall measure of stream health. The CSCI score is calculated by comparing the expected condition with actual (observed) results (Rehn, A.C. et al., 2015). CSCI scores range from 0 (highly degraded) to greater than 1 (equivalent to reference). CSCI scoring of biological condition are as follows (per the scientific paper supporting the development of the CSCI scoring tool): greater than or equal to 0.92 = likely intact condition, 0.91 to 0.80 = possibly altered condition, 0.79 to 0.63 = likely altered condition, less than or equal to 0.62 = very likely altered condition. Sites with scores below 0.79 are considered to have exceeded the water quality objective for the aquatic life beneficial use.Â
Line of Evidence (LOE) for Decision ID 154220, Benthic Community Effects
Region 2
Arroyo Las Positas
LOE ID:
306935
Pollutant:
Benthic-Macroinvertebrate Bioassessments
LOE Subgroup:
Population/Community Degradation
Matrix:
Water
Fraction:
None
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
1
Data and Information Type:
Benthic macroinvertebrate surveys
Data Used to Assess Water Quality:
Water Board staff assessed data for 204R03327 to determine beneficial use support and the results are as follows: 1 of 1 samples exceeded the threshold. CSCI scores were from 0.483150561 to 0.483150561.
All waters shall be maintained free of toxic substances in concentrations that are lethal to or that produce significant alterations in population or community ecology or receiving water biota. In addition, the health and life history characteristics of aquatic organisms in waters affected by controllable water quality factors shall not differ significantly from those for the same waters in areas unaffected by controllable water quality factors.
The California Stream Condition Index (CSCI) is a biological scoring tool that helps aquatic resource managers translate complex data about benthic macroinvertebrates found living in a stream into an overall measure of stream health. The CSCI score is calculated by comparing the expected condition with actual (observed) results (Rehn, A.C. et al., 2015). CSCI scores range from 0 (highly degraded) to greater than 1 (equivalent to reference). CSCI scoring of biological condition are as follows (per the scientific paper supporting the development of the CSCI scoring tool): greater than or equal to 0.92 = likely intact condition, 0.91 to 0.80 = possibly altered condition, 0.79 to 0.63 = likely altered condition, less than or equal to 0.62 = very likely altered condition. Sites with scores below 0.79 are considered to have exceeded the water quality objective for the aquatic life beneficial use.Â
Line of Evidence (LOE) for Decision ID 154220, Benthic Community Effects
Region 2
Arroyo Las Positas
LOE ID:
306911
Pollutant:
Benthic-Macroinvertebrate Bioassessments
LOE Subgroup:
Population/Community Degradation
Matrix:
Water
Fraction:
None
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
1
Data and Information Type:
Benthic macroinvertebrate surveys
Data Used to Assess Water Quality:
Water Board staff assessed data for 204R00665 to determine beneficial use support and the results are as follows: 1 of 1 samples exceeded the threshold. CSCI scores were from 0.616622 to 0.616622.
All waters shall be maintained free of toxic substances in concentrations that are lethal to or that produce significant alterations in population or community ecology or receiving water biota. In /tr>
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed SWAMP RWB2 Monitoring data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Ammonia as N, Unionized.
Water Quality Control Plan, San Francisco Bay Basin, Chapter III Water Quality Objectives, Section 3.3.20 Un-Ionized Ammonia: The discharge of wastes shall not cause receiving waters to contain concentrations of un-ionized ammonia in excess 0.025 mg/l (as N), expressed as an annual median.
Line of Evidence (LOE) for Decision ID 150849, Ammonia
Region 2
Arroyo Las Positas
LOE ID:
278673
Pollutant:
Nitrogen, ammonia (Total Ammonia)
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
1
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2015 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 1 of 1 samples exceeded the water quality threshold for Ammonia as N.
The Total Ammonia criterion continuous concentration (expressed as a 30-day average) to protect aquatic life in freshwater is Temperature and pH dependent, and was calculated according to the formula listed in the Aquatic Life Ambient Water Quality Criteria for Ammonia - Freshwater 2013 document.
The California Stream Condition Index (CSCI) is a biological scoring tool that helps aquatic resource managers translate complex data about benthic macroinvertebrates found living in a stream into an overall measure of stream health. The CSCI score is calculated by comparing the expected condition with actual (observed) results (Rehn, A.C. et al., 2015). CSCI scores range from 0 (highly degraded) to greater than 1 (equivalent to reference). CSCI scoring of biological condition are as follows (per the scientific paper supporting the development of the CSCI scoring tool): greater than or equal to 0.92 = likely intact condition, 0.91 to 0.80 = possibly altered condition, 0.79 to 0.63 = likely altered condition, less than or equal to 0.62 = very likely altered condition. Sites with scores below 0.79 are considered to have exceeded the water quality objective for the aquatic life beneficial use.Â
Line of Evidence (LOE) for Decision ID 154220, Benthic Community Effects
Region 2
Arroyo Las Positas
LOE ID:
306922
Pollutant:
Benthic-Macroinvertebrate Bioassessments
LOE Subgroup:
Population/Community Degradation
Matrix:
Water
Fraction:
None
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
1
Data and Information Type:
Benthic macroinvertebrate surveys
Data Used to Assess Water Quality:
Water Board staff assessed data for 204R01433 to determine beneficial use support and the results are as follows: 1 of 1 samples exceeded the threshold. CSCI scores were from 0.342084 to 0.342084.
All waters shall be maintained free of toxic substances in concentrations that are lethal to or that produce significant alterations in population or community ecology or receiving water biota. In addition, the health and life history characteristics of aquatic organisms in waters affected by controllable water quality factors shall not differ significantly from those for the same waters in areas unaffected by controllable water quality factors.
The California Stream Condition Index (CSCI) is a biological scoring tool that helps aquatic resource managers translate complex data about benthic macroinvertebrates found living in a stream into an overall measure of stream health. The CSCI score is calculated by comparing the expected condition with actual (observed) results (Rehn, A.C. et al., 2015). CSCI scores range from 0 (highly degraded) to greater than 1 (equivalent to reference). CSCI scoring of biological condition are as follows (per the scientific paper supporting the development of the CSCI scoring tool): greater than or equal to 0.92 = likely intact condition, 0.91 to 0.80 = possibly altered condition, 0.79 to 0.63 = likely altered condition, less than or equal to 0.62 = very likely altered condition. Sites with scores below 0.79 are considered to have exceeded the water quality objective for the aquatic life beneficial use.Â
Line of Evidence (LOE) for Decision ID 150849, Ammonia
Region 2
Arroyo Las Positas
LOE ID:
278169
Pollutant:
Nitrogen, ammonia (Total Ammonia)
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2017 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Ammonia as N.
The Total Ammonia criterion continuous concentration (expressed as a 30-day average) to protect aquatic life in freshwater is Temperature and pH dependent, and was calculated according to the formula listed in the Aquatic Life Ambient Water Quality Criteria for Ammonia - Freshwater 2013 document.
Line of Evidence (LOE) for Decision ID 154220, Benthic Community Effects
Region 2
Arroyo Las Positas
LOE ID:
286749
Pollutant:
pH
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
None
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
12
Number of Exceedances:
2
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed SWAMP RWB2 Monitoring data for Arroyo Las Positas to determine beneficial use support and results are as follows: 2 of 12 samples exceeded the water quality threshold for pH.
Water Quality Control Plan, San Francisco Bay Basin, Chapter III Water Quality Objectives, Section 3.3.9 pH states: The pH shall not be depressed below 6.5 nor raised above 8.5. This encompasses the pH range usually found in waters within the basin. Controllable water quality factors shall not cause changes greater than 0.5 units in normal ambient pH levels.
Line of Evidence (LOE) for Decision ID 154220, Benthic Community Effects
Region 2
Arroyo Las Positas
LOE ID:
286357
Pollutant:
pH
LOE Subgroup:
Pollutant-Water
Matrix:">Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2012 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Ammonia as N.
The Total Ammonia criterion continuous concentration (expressed as a 30-day average) to protect aquatic life in freshwater is Temperature and pH dependent, and was calculated according to the formula listed in the Aquatic Life Ambient Water Quality Criteria for Ammonia - Freshwater 2013 document.
Line of Evidence (LOE) for Decision ID 150849, Ammonia
Region 2
Arroyo Las Positas
LOE ID:
278060
Pollutant:
Nitrogen, ammonia (Total Ammonia)
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
6
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed SWAMP RWB2 Monitoring data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 6 samples exceeded the water quality threshold for Ammonia as N.
The Total Ammonia criterion continuous concentration (expressed as a 30-day average) to protect aquatic life in freshwater is Temperature and pH dependent, and was calculated according to the formula listed in the Aquatic Life Ambient Water Quality Criteria for Ammonia - Freshwater 2013 document.
The samples were collected at 1 monitoring site: 204ALP105 (Altamont-Springtown).
Temporal Representation:
The samples were collected between the dates of 2011-03-02 and 2019-07-23
Water
Fraction:
None
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
15
Number of Exceedances:
7
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed SWAMP RWB2 Monitoring data for Arroyo Las Positas to determine beneficial use support and results are as follows: 7 of 15 samples exceeded the water quality threshold for pH.
Water Quality Control Plan, San Francisco Bay Basin, Chapter III Water Quality Objectives, Section 3.3.9 pH states: The pH shall not be depressed below 6.5 nor raised above 8.5. This encompasses the pH range usually found in waters within the basin. Controllable water quality factors shall not cause changes greater than 0.5 units in normal ambient pH levels.
Line of Evidence (LOE) for Decision ID 154220, Benthic Community Effects
Region 2
Arroyo Las Positas
LOE ID:
306898
Pollutant:
Benthic-Macroinvertebrate Bioassessments
LOE Subgroup:
Population/Community Degradation
Matrix:
Water
Fraction:
None
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
1
Data and Information Type:
Benthic macroinvertebrate surveys
Data Used to Assess Water Quality:
Water Board staff assessed data for 204ALP100 to determine beneficial use support and the results are as follows: 1 of 1 samples exceeded the threshold. CSCI scores were from 0.382736 to 0.382736.
All waters shall be maintained free of toxic substances in concentrations that are lethal to or that produce significant alterations in population or community ecology or receiving water biota. In addition, the health and life history characteristics of aquatic organisms in waters affected by controllable water quality factors shall not differ significantly from those for the same waters in areas unaffected by controllable water quality factors.
Line of Evidence (LOE) for Decision ID 150849, Ammonia
Region 2
Arroyo Las Positas
LOE ID:
277744
Pollutant:
Nitrogen, ammonia (Total Ammonia)
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
1
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2019 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 1 of 1 samples exceeded the water quality threshold for Ammonia as N.
The Total Ammonia criterion continuous concentration (expressed as a 30-day average) to protect aquatic life in freshwater is Temperature and pH dependent, and was calculated according to the formula listed in the Aquatic Life Ambient Water Quality Criteria for Ammonia - Freshwater 2013 document.
Line of Evidence (LOE) for Decision ID 150849, Ammonia
Region 2
Arroyo Las Positas
LOE ID:
278661
Pollutant:
Nitrogen, ammonia (Total Ammonia)
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
1
Data and Info Stream Condition Index (CSCI) is a biological scoring tool that helps aquatic resource managers translate complex data about benthic macroinvertebrates found living in a stream into an overall measure of stream health. The CSCI score is calculated by comparing the expected condition with actual (observed) results (Rehn, A.C. et al., 2015). CSCI scores range from 0 (highly degraded) to greater than 1 (equivalent to reference). CSCI scoring of biological condition are as follows (per the scientific paper supporting the development of the CSCI scoring tool): greater than or equal to 0.92 = likely intact condition, 0.91 to 0.80 = possibly altered condition, 0.79 to 0.63 = likely altered condition, less than or equal to 0.62 = very likely altered condition. Sites with scores below 0.79 are considered to have exceeded the water quality objective for the aquatic life beneficial use.Â
Line of Evidence (LOE) for Decision ID 154220, Benthic Community Effects
Region 2
Arroyo Las Positas
LOE ID:
306694
Pollutant:
Benthic-Macroinvertebrate Bioassessments
LOE Subgroup:
Population/Community Degradation
Matrix:
Water
Fraction:
None
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
2
Number of Exceedances:
2
Data and Information Type:
Benthic macroinvertebrate surveys
Data Used to Assess Water Quality:
Water Board staff assessed data for 204ALP040 to determine beneficial use support and the results are as follows: 2 of 2 samples exceeded the threshold. CSCI scores were from 0.294759168 to 0.437916901.
All waters shall be maintained free of toxic substances in concentrations that are lethal to or that produce significant alterations in population or community ecology or receiving water biota. In addition, the health and life history characteristics of aquatic organisms in waters affected by controllable water quality factors shall not differ significantly from those for the same waters in areas unaffected by controllable water quality factors.
The California Stream Condition Index (CSCI) is a biological scoring tool that helps aquatic resource managers translate complex data about benthic macroinvertebrates found living in a stream into an overall measure of stream health. The CSCI score is calculated by comparing the expected condition with actual (observed) results (Rehn, A.C. et al., 2015). CSCI scores range from 0 (highly degraded) to greater than 1 (equivalent to reference). CSCI scoring of biological condition are as follows (per the scientific paper supporting the development of the CSCI scoring tool): greater than or equal to 0.92 = likely intact condition, 0.91 to 0.80 = possibly altered condition, 0.79 to 0.63 = likely altered condition, less than or equal to 0.62 = very likely altered condition. Sites with scores below 0.79 are considered to have exceeded the water quality objective for the aquatic life beneficial use.Â
Samples were collected from 4/26/2001 to 6/12/2019.
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2019 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 1 of 1 samples exceeded the water quality threshold for Ammonia as N.
The Total Ammonia criterion continuous concentration (expressed as a 30-day average) to protect aquatic life in freshwater is Temperature and pH dependent, and was calculated according to the formula listed in the Aquatic Life Ambient Water Quality Criteria for Ammonia - Freshwater 2013 document.
Line of Evidence (LOE) for Decision ID 150849, Ammonia
Region 2
Arroyo Las Positas
LOE ID:
278056
Pollutant:
Nitrogen, ammonia (Total Ammonia)
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2019 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Ammonia as N.
The Total Ammonia criterion continuous concentration (expressed as a 30-day average) to protect aquatic life in freshwater is Temperature and pH dependent, and was calculated according to the formula listed in the Aquatic Life Ambient Water Quality Criteria for Ammonia - Freshwater 2013 document.
Line of Evidence (LOE) for Decision ID 154220, Benthic Community Effects
Region 2
Arroyo Las Positas
LOE ID:
306695
Pollutant:
Benthic-Macroinvertebrate Bioassessments
LOE Subgroup:
Population/Community Degradation
Matrix:
Water
Fraction:
None
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
1
Data and Information Type:
Benthic macroinvertebrate surveys
Data Used to Assess Water Quality:
Water Board staff assessed data for 204ALP070 to determine beneficial use support and the results are as follows: 1 of 1 samples exceeded the threshold. CSCI scores were from 0.471220175 to 0.471220175.
All waters shall be maintained free of toxic substances in concentrations that are lethal to or that produce significant alterations in population or community ecology or receiving water biota. In addition, the health and life history characteristics of aquatic organisms in waters affected by controllable water quality factors shall not differ significantly from those for the same waters in areas unaffected by controllable water quality factors.
The California Stream Condition Index (CSCI) is a biological scoring tool that helps aquatic resource managers translate complex data about benthic macroinvertebrates found living in a stream into an overall measure of stream health. The CSCI score is calculated by comparing the expected condition with actual (observed) results (Rehn, A.C. et al., 2015). CSCI scores range from 0 (highly degraded) to greater than 1 (equivalent to reference). CSCI scoring of biological condition are as follows (per the scientific paper supporting the development of the CSCI scoring tool): greater than or equal to 0.92 = likely intact condition, 0.91 to 0.80 = possibly altered condition, 0.79 to 0.63 = likely altered condition, less than or equal to 0.62 = very likely altered condition. Sites with scores below 0.79 are considered to have exceeded the water quality objective for the aquatic life beneficial use.Â
Line of Evidence (LOE) for Decision ID 154220, Benthic Community Effects
Region 2
Arroyo Las Positas
LOE ID:
306660
Pollutant:
Benthic-Macroinvertebrate Bioassessments
LOE Subgroup:
Population/Community Degradation
Matrix:
Water
Fraction:
None
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
1
Data and Information Type:
Benthic macroinvertebrate surveys
Data Used to Assess Water Quality:
Water Board staff assessed data for 204ALP010 to determine beneficial use support and the results are as follows: 1 of 1 samples exceeded the threshold. CSCI scores were from 0.585281271 to 0.585281271.
All waters shall be maintained free of toxic substances in concentrations that are lethal to or that produce significant alterations in population or community ecology or receiving water biota. In addition, the health and life history characteristics of aquatic organisms in waters affected by controllable water quality factors shall not differ significantly from those for the same waters in areas unaffected by controllable water quality factors.
The California Stream Condition Index (CSCI) is a biological scoring tool that helps aquatic resource managers translate complex data about benthic macroinvertebrates found living in a stream into an overall measure of stream health. The CSCI score is calculated by comparing the expected condition with actual (observed) results (Rehn, A.C. et al., 2015). CSCI scores range from 0 (highly degraded) to greater than 1 (equivalent to reference). CSCI scoring of biological condition are as follows (per the scientific paper supporting the development of the CSCI scoring tool): greater than or equal to 0.92 = likely intact condition, 0.91 to 0.80 = possibly altered condition, 0.79 to 0.63 = likely altered condition, less than or equal to 0.62 = very likely altered condition. Sites with scores below 0.79 are considered to have exceeded the water quality objective for the aquatic life beneficial use.Â
Line of Evidence (LOE) for Decision ID 150849, Ammonia
Region 2
Arroyo Las Positas
LOE ID:
277777
Pollutant:
Nitrogen, ammonia (Total Ammonia)
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2014 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Ammonia as N.
The Total Ammonia criterion continuous concentration (expressed as a 30-day average) to protect aquatic life in freshwater is Temperature and pH dependent, and was calculated according to the formula listed in the Aquatic Life Ambient Water Quality Criteria for Ammonia - Freshwater 2013 document.
Line of Evidence (LOE) for Decision ID 150849, Ammonia
Region 2
Arroyo Las Positas
LOE ID:
278722
Pollutant:
Nitrogen, ammonia (Total Ammonia)
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2019 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Ammonia as N.
All waters shall be maintained free of toxic substances in concentrations that are lethal to or that produce significant alterations in population or community ecology or receiving water biota. In addition, the health and life history characteristics of aquatic organisms in waters affected by controllable water quality factors shall not differ significantly from those for the same waters in areas unaffected by controllable water quality factors.
The California Stream Condition Index (CSCI) is a biological scoring tool that helps aquatic resource managers translate complex data about benthic macroinvertebrates found living in a stream into an overall measure of stream health. The CSCI score is calculated by comparing the expected condition with actual (observed) results (Rehn, A.C. et al., 2015). CSCI scores range from 0 (highly degraded) to greater than 1 (equivalent to reference). CSCI scoring of biological condition are as follows (per the scientific paper supporting the development of the CSCI scoring tool): greater than or equal to 0.92 = likely intact condition, 0.91 to 0.80 = possibly altered condition, 0.79 to 0.63 = likely altered condition, less than or equal to 0.62 = very likely altered condition. Sites with scores below 0.79 are considered to have exceeded the water quality objective for the aquatic life beneficial use.Â
Line of Evidence (LOE) for Decision ID 154220, Benthic Community Effects
Region 2
Arroyo Las Positas
LOE ID:
306934
Pollutant:
Benthic-Macroinvertebrate Bioassessments
LOE Subgroup:
Population/Community Degradation
Matrix:
Water
Fraction:
None
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
2
Number of Exceedances:
2
Data and Information Type:
Benthic macroinvertebrate surveys
Data Used to Assess Water Quality:
Water Board staff assessed data for 204R03481 to determine beneficial use support and the results are as follows: 2 of 2 samples exceeded the threshold. CSCI scores were from 0.300410439 to 0.384844659.
All waters shall be maintained free of toxic substances in concentrations that are lethal to or that produce significant alterations in population or community ecology or receiving water biota. In addition, the health and life history characteristics of aquatic organisms in waters affected by controllable water quality factors shall not differ significantly from those for the same waters in areas unaffected by controllable water quality factors.
The Total Ammonia criterion continuous concentration (expressed as a 30-day average) to protect aquatic life in freshwater is Temperature and pH dependent, and was calculated according to the formula listed in the Aquatic Life Ambient Water Quality Criteria for Ammonia - Freshwater 2013 document.
Line of Evidence (LOE) for Decision ID 150849, Ammonia
Region 2
Arroyo Las Positas
LOE ID:
278548
Pollutant:
Nitrogen, ammonia (Total Ammonia)
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
4
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed SWAMP RWB2 Monitoring data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 4 samples exceeded the water quality threshold for Ammonia as N.
The Total Ammonia criterion continuous concentration (expressed as a 30-day average) to protect aquatic life in freshwater is Temperature and pH dependent, and was calculated according to the formula listed in the Aquatic Life Ambient Water Quality Criteria for Ammonia - Freshwater 2013 document.
Line of Evidence (LOE) for Decision ID 154220, Benthic Community Effects
Region 2
Arroyo Las Positas
LOE ID:
279491
Pollutant:
Ammonia (Unionized)
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
1
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2019 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 1 of 1 samples exceeded the water quality threshold for Ammonia as N, Unionized.
Water Quality Control Plan, San Francisco Bay Basin, Chapter III Water Quality Objectives, Section 3.3.20 Un-Ionized Ammonia: The discharge of wastes shall not cause receiving waters to contain concentrations of un-ionized ammonia in excess 0.025 mg/l (as N), expressed as an annual median.
Line of Evidence (LOE) for Decision ID 154220, Benthic Community Effects
Region 2 &ld; PADDING-BOTTOM: 3px; WIDTH: 100%; text-align: left; PADDING-TOP: 3px; font-smooth: always">Line of Evidence (LOE) for Decision ID 150849, Ammonia
Region 2
Arroyo Las Positas
LOE ID:
278059
Pollutant:
Nitrogen, ammonia (Total Ammonia)
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
9
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed SWAMP RWB2 Monitoring data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 9 samples exceeded the water quality threshold for Ammonia as N.
The Total Ammonia criterion continuous concentration (expressed as a 30-day average) to protect aquatic life in freshwater is Temperature and pH dependent, and was calculated according to the formula listed in the Aquatic Life Ambient Water Quality Criteria for Ammonia - Freshwater 2013 document.
Line of Evidence (LOE) for Decision ID 150849, Ammonia
Region 2
Arroyo Las Positas
LOE ID:
278168
Pollutant:
Nitrogen, ammonia (Total Ammonia)
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2017 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Ammonia as N.
Water Board staff assessed BASMAA RMC Monitoring in WY2015 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 1 of 1 samples exceeded the water quality threshold for Ammonia as N, Unionized.
Water Quality Control Plan, San Francisco Bay Basin, Chapter III Water Quality Objectives, Section 3.3.20 Un-Ionized Ammonia: The discharge of wastes shall not cause receiving waters to contain concentrations of un-ionized ammonia in excess 0.025 mg/l (as N), expressed as an annual median.
Line of Evidence (LOE) for Decision ID 154220, Benthic Community Effects
Region 2
Arroyo Las Positas
LOE ID:
279470
Pollutant:
Ammonia (Unionized)
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
1
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2019 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 1 of 1 samples exceeded the water quality threshold for Ammonia as N, Unionized.
Water Quality Control Plan, San Francisco Bay Basin, Chapter III Water Quality Objectives, Section 3.3.20 Un-Ionized Ammonia: The discharge of wastes shall not cause receiving waters to contain concentrations of un-ionized ammonia in exc"top" width="33%">SWAMP Data:
Non-SWAMP
Water Quality Objective/Criterion:
The Total Ammonia criterion continuous concentration (expressed as a 30-day average) to protect aquatic life in freshwater is Temperature and pH dependent, and was calculated according to the formula listed in the Aquatic Life Ambient Water Quality Criteria for Ammonia - Freshwater 2013 document.
Line of Evidence (LOE) for Decision ID 150849, Ammonia
Region 2
Arroyo Las Positas
LOE ID:
278591
Pollutant:
Nitrogen, ammonia (Total Ammonia)
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
6
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed SWAMP RWB2 Monitoring data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 6 samples exceeded the water quality threshold for Ammonia as N.
The Total Ammonia criterion continuous concentration (expressed as a 30-day average) to protect aquatic life in freshwater is Temperature and pH dependent, and was calculated according to the formula listed in the Aquatic Life Ambient Water Quality Criteria for Ammonia - Freshwater 2013 document.
Line of Evidence (LOE) for Decision ID 154220, Benthic Community Effects
Region 2
Arroyo Las Positas
LOE ID:
281866
Pollutant:
Chloride
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
1
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2017 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 1 of 1 samples exceeded the water quality threshold for Chloride.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
The chloride criterion continuous concentration (expressed as a 4-day average) to protect aquatic life in freshwater is 230000 ug/L (230 mg/L)(USEPA National Recommended Water Quality Criteria, 2006).
Line of Evidence (LOE) for Decision ID 154220, Benthic Community Effects
Region 2
Arroyo Las Positas
LOE ID:
277589
Pollutant:
Nitrogen, ammonia (Total Ammonia)
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
1
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2015 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 1 of 1 samples exceeded the water quality threshold for Ammonia as N.
The Total Ammonia criterion continuous concentration (expressed as a 30-day average) to protect aquatic life in freshwater is Temperature and pH dependent, and was calculated according to the formula listed in the Aquatic Life Ambient Water Quality Criteria for Ammonia - Freshwater 2013 document.
Line of Evidence (LOE) for Decision ID 150849, Ammonia
Region 2
Arroyo Las Positas
LOE ID:
278556
Pollutant:
Nitrogen, ammonia (Total Ammonia)
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
9
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed SWAMP RWB2 Monitoring data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 9 samples exceeded the water quality threshold for Ammonia as N.
The Total Ammonia criterion continuous concentratioING-TOP: 3px; font-smooth: always">Region 2
Arroyo Las Positas
LOE ID:
280970
Pollutant:
Chloride
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Dissolved
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
3
Number of Exceedances:
2
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed SWAMP RWB2 Monitoring data for Arroyo Las Positas to determine beneficial use support and results are as follows: 2 of 3 samples exceeded the water quality threshold for Chloride.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
The chloride criterion continuous concentration (expressed as a 4-day average) to protect aquatic life in freshwater is 230000 ug/L (230 mg/L)(USEPA National Recommended Water Quality Criteria, 2006).
Line of Evidence (LOE) for Decision ID 154220, Benthic Community Effects
Region 2
Arroyo Las Positas
LOE ID:
281126
Pollutant:
Chloride
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Dissolved
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
4
Number of Exceedances:
2
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed SWAMP RWB2 Monitoring data for Arroyo Las Positas to determine beneficial use support and results are as follows: 2 of 4 samples exceeded the water quality threshold for Chloride.
Line of Evidence (LOE) for Decision ID 150849, Ammonia
Region 2
Arroyo Las Positas
LOE ID:
277853
Pollutant:
Nitrogen, ammonia (Total Ammonia)
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2014 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Ammonia as N.
The Total Ammonia criterion continuous concentration (expressed as a 30-day average) to protect aquatic life in freshwater is Temperature and pH dependent, and was calculated according to the formula listed in the Aquatic Life Ambient Water Quality Criteria for Ammonia - Freshwater 2013 document.
Line of Evidence (LOE) for Decision ID 150849, Ammonia
Region 2
Arroyo Las Positas
SWAMP Data:
SWAMP
Water Quality Objective/Criterion:
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
The chloride criterion continuous concentration (expressed as a 4-day average) to protect aquatic life in freshwater is 230000 ug/L (230 mg/L)(USEPA National Recommended Water Quality Criteria, 2006).
Line of Evidence (LOE) for Decision ID 154220, Benthic Community Effects
Region 2
Arroyo Las Positas
LOE ID:
281315
Pollutant:
Chloride
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Dissolved
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
2
Number of Exceedances:
2
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed SWAMP RWB2 Monitoring data for Arroyo Las Positas to determine beneficial use support and results are as follows: 2 of 2 samples exceeded the water quality threshold for Chloride.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
The chloride criterion continuous concentration (expressed as a 4-day average) to protect aquatic life in freshwater is 230000 ug/L (230 mg/L)(USEPA National Recommended Water Quality Criteria, 2006).
The samples were collected at 1 monitoring site: 204ALP075 (Arroyo las Positas at Paseo Laguna Seco apartments).
Temporal Representation:
The samples were collected between the dates of 2018-05-10 and 2019-06-11
Environmental Conditions:
LOE ID:
278058
Pollutant:
Nitrogen, ammonia (Total Ammonia)
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2020 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Ammonia as N.
The Total Ammonia criterion continuous concentration (expressed as a 30-day average) to protect aquatic life in freshwater is Temperature and pH dependent, and was calculated according to the formula listed in the Aquatic Life Ambient Water Quality Criteria for Ammonia - Freshwater 2013 document.
Line of Evidence (LOE) for Decision ID 150849, Ammonia
Region 2
Arroyo Las Positas
LOE ID:
278478
Pollutant:
Nitrogen, ammonia (Total Ammonia)
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
4
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed SWAMP RWB2 Monitoring data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 4 samples exceeded the water quality threshold for Ammonia as N.
The Total Ammonia criterion continuous concentration (expressed as a 30-day average) to protect aquatic life in freshwater is Temperature and pH dependent, and was calculated according to the formula listed in the Aquatic Life Ambient Water Quality Criteria for Ammonia - Freshwater 2013 document.
Line of Evidence (LOE) for Decision ID 150849, Ammonia
Region 2
Arroyo Las Positas
LOE ID:
278018
Pollutant:
Nitrogen, ammonia (Total Ammonia)
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2014 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Ammonia as N.
The Total Ammonia criterion continuous concentration (expressed as a 30-day average) to protect aquatic life in freshwater is Temperature and pH dependent, and was calculated according to the formula listed in the Aquatic Life Ambient Water Quality Criteria for Ammonia - Freshwater 2013 document.
Line of Evidence (LOE) for Decision ID 154220, Benthic Community Effects
Region 2
Arroyo Las Positas
LOE ID:
281494
Pollutant:
Chloride
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
1
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2012 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 1 of 1 samples exceeded the water quality threshold for Chloride.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
The chloride criterion continuous concentration (expressed as a 4-day average) to protect aquatic life in freshwater is 230000 ug/L (230 mg/L)(USEPA National Recommended Water Quality Criteria, 2006).
Line of Evidence (LOE) for Decision ID 154220, Benthic Community Effects
Region 2
Arroyo Las Positas
LOE ID:
281888
Pollutant:
Chloride
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
1
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2016 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 1 of 1 samples exceeded the water quality threshold for Chloride.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
The chloride criterion continuous concentration (expressed as a 4-day average) to protect aquatic life in freshwater is 230000 ug/L (230 mg/L)(USEPA National Recommended Water Quality Criteria, 2006).
Line of Evidence (LOE) for Decision ID 154220, Benthic Community Effects
Region 2
Arroyo Las Positas
LOE ID:
281506
Pollutant:
Chloride
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
4
Number of Exceedances:
2
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2019 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 2 of 4 samples exceeded the water quality threshold for Chloride.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
The chloride criterion continuous concentration (expressed as a 4-day average) to protect aquatic life in freshwater is 230000 ug/L (230 mg/L)(USEPA National Recommended Water Quality Crit%">LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2017 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Ammonia as N.
The Total Ammonia criterion continuous concentration (expressed as a 30-day average) to protect aquatic life in freshwater is Temperature and pH dependent, and was calculated according to the formula listed in the Aquatic Life Ambient Water Quality Criteria for Ammonia - Freshwater 2013 document.
Line of Evidence (LOE) for Decision ID 150849, Ammonia
Region 2
Arroyo Las Positas
LOE ID:
278674
Pollutant:
Nitrogen, ammonia (Total Ammonia)
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2016 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Ammonia as N.
The Total Ammonia criterion continuous concentration (expressed as a 30-day average) to protect aquatic life in freshwater is Temperature and pH dependent, and was calculated according to the formula listed in the Aquatic Life Ambient Water Quality Criteria for Ammonia - Freshwater 2013 document.
The San Francisco Bay Regional Water Quality Board Basin Plan stated that the discharge of wastes shall not cause receiving water to contain concentrations of un-ionized ammonia in excess of 0.025mg/l annual median.For Total Ammonia: EPA's Lifetime Health advisory level for total ammonia is 30.0 mg/L as stated on page 8 of the 2006 edition of the drinking water standards and health advisories. This Advisory Level is defined as the concentration of a chemical in drinking water that is not expected to cause any adverse noncarcinogenic effects for up to ten days of exposure.
Line of Evidence (LOE) for Decision ID 154220, Benthic Community Effects
Region 2
Arroyo Las Positas
LOE ID:
281331
Pollutant:
Chloride
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
1
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2014 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 1 of 1 samples exceeded the water quality threshold for Chloride.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
The chloride criterion continuous concentration (expressed as a 4-day average) to protect aquatic life in freshwater is 230000 ug/L (230 mg/L)(USEPA National Recommended Water Quality Criteria, 2006).
Line of Evidence (LOE) for Decision ID 154220, Benthic Community Effects
Region 2
Arroyo Las Positas
LOE ID:
281511
Pollutant:
Chloride
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
1
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2015 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 1 of 1 samples exceeded the water quality threshold for Chloride.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
The chloride criterion continuous concentration (expressed as a 4-day average) to protect aquatic life in freshwater is 230000 ug/L (230 mg/L)(USEPA National Recommended Water Quality Criteria, 2006).
Line of Evidence (LOE) for Decision ID 154220, Benthic Community Effects
Region 2
Arroyo Las Positas
LOE ID:
281141
Pollutant:
Chloride
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
4
Number of Exceedances:
3
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2019 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 3 of 4 samples exceeded the water quality threshold for Chloride.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall-LEFT: 0%; FONT-WEIGHT: bold; PADDING-BOTTOM: 3px; WIDTH: 100%; text-align: left; PADDING-TOP: 3px; font-smooth: always">Arroyo Las Positas
LOE ID:
278057
Pollutant:
Nitrogen, ammonia (Total Ammonia)
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
1
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2019 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 1 of 1 samples exceeded the water quality threshold for Ammonia as N.
The Total Ammonia criterion continuous concentration (expressed as a 30-day average) to protect aquatic life in freshwater is Temperature and pH dependent, and was calculated according to the formula listed in the Aquatic Life Ambient Water Quality Criteria for Ammonia - Freshwater 2013 document.
Line of Evidence (LOE) for Decision ID 150849, Ammonia
Region 2
Arroyo Las Positas
LOE ID:
279540
Pollutant:
Ammonia (Unionized)
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2017 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Ammonia as N, Unionized.
Water Quality Control Plan, San Francisco Bay Basin, Chapter III Water Quality Objectives, Section 3.3.20 Un-Ionized Ammonia: The discharge of wastes shall not cause receiving waters to contain concentrations of un-ionized ammonia in excess 0.025 mg/l (as N), expressed as an annual median.
Line of Evidence (LOE) for Decision ID 150849, Ammonia
Region 2
Arroyo Las Positas
LOE ID:
279491
Pollutant:
Ammonia (Unionized)
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
1
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2019 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 1 of 1 samples exceeded the water quality threshold for Ammonia as N, Unionized.
Water Quality Control Plan, San Francisco Bay Basin, Chapter III Water Quality Objectives, Section 3.3.20 Un-Ionized Ammonia: The discharge of wastes shall not cause receiving waters to contain concentrations of un-ionized ammonia in excess 0.025 mg/l (as N), expressed as an annual median.
The chloride criterion continuous concentration (expressed as a 4-day average) to protect aquatic life in freshwater is 230000 ug/L (230 mg/L)(USEPA National Recommended Water Quality Criteria, 2006).
Line of Evidence (LOE) for Decision ID 154220, Benthic Community Effects
Region 2
Arroyo Las Positas
LOE ID:
281864
Pollutant:
Chloride
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
1
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2014 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 1 of 1 samples exceeded the water quality threshold for Chloride.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
The chloride criterion continuous concentration (expressed as a 4-day average) to protect aquatic life in freshwater is 230000 ug/L (230 mg/L)(USEPA National Recommended Water Quality Criteria, 2006).
Line of Evidence (LOE) for Decision ID 154220, Benthic Community Effects
Region 2
Arroyo Las Positas
LOE ID:
281403
Pollutant:
Chloride
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
1
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2017 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 1 of 1 samples exceeded the water quality threshold for Chloride.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
The chloride criterion continuous concentration (expressed as a 4-day average) to protect aquatic life in freshwater is 230000 ug/L (230 mg/L)(USEPA National Recommended Water Quality Criteria, 2006).
Line of Evidence (LOE) for Decision ID 154220, Benthic Community Effects
Region 2
Arroyo Las Positas
LOE ID:
30213
Pollutant:
Temperature, water
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
None
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
13
Number of Exceedances:
7
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Ammonia (Unionized)
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
1
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2019 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 1 of 1 samples exceeded the water quality threshold for Ammonia as N, Unionized.
Water Quality Control Plan, San Francisco Bay Basin, Chapter III Water Quality Objectives, Section 3.3.20 Un-Ionized Ammonia: The discharge of wastes shall not cause receiving waters to contain concentrations of un-ionized ammonia in excess 0.025 mg/l (as N), expressed as an annual median.
Line of Evidence (LOE) for Decision ID 150849, Ammonia
Region 2
Arroyo Las Positas
LOE ID:
279268
Pollutant:
Ammonia (Unionized)
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed SWAMP RWB2 Monitoring data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Ammonia as N, Unionized.
Water Quality Control Plan, San Francisco Bay Basin, Chapter III Water Quality Objectives, Section 3.3.20 Un-Ionized Ammonia: The discharge of wastes shall not cause receiving waters to contain concentrations of un-ionized ammonia in excess 0.025 mg/l (as N), expressed as an annual median.
Guid">Water quality assessment was conducted at the Arroyo Las Positas watershed as part of SWAMP study in 2002. Continuous field monitoring at 15 minute increments of temperature, dissolved oxygen, pH and specific conductance was conducted to determine temporal variability in basic water quality at three locations. Continuous monitoring sondes were deployed 13 times at 3 or 5 monitoring locations during winter wet, spring wet and summer dry seasons. The measured temperatures ranged from 3.89oC to 32.1oC and varied with season and location. The 7-day mean temperature threshold for steelhead of 17 °C was exceeded during 7 out of 13 deployments. The 7-day moving average was consistently high (above 20oC) at all 5 monitoring locations during summer sampling season only (June-July 2002).
Temperature objectives for enclosed bays and estuaries are specified in the "Water Quality Control Plan for Control of Temperature in the Coastal and Interstate Waters and Enclosed Bays of California" including any revisions to the plan. In addition, the following temperature objectives apply to surface waters: The natural receiving water temperature of intrastate waters shall not be altered unless it can be demonstrated to the satisfaction of the Regional Board that such an alteration does not adversely affect beneficial uses. The temperature of any cold or warm freshwater habitat shall not be increased by more than 5°F (2.8°C) above natural receiving water temperature.
Sullivan et al. (2000) reviewed a wide range of studies incorporating information from laboratory-based research, field observations, and risk assessment approaches and developed criteria for assessing temperature risk to aquatic life. The 7-day mean temperature (maximum value of a 7-day moving average of the daily mean temperature) of 14.8°C was established as the upper threshold criterion for coho salmon and 17.0°C for steelhead trout. The risk assessment approach used by Sullivan et al. (2000)suggest that temperatures exceeding the above thresholds will cause a 10% reduction in average growth compared to optimal conditions.
Temperature was measured at three or five sites in the Arroyo Las Positas watershead. Four monitoring sites are located in the mainstream of Arroyo Las Positas Creek while one site (ALP105) is located in Altamont Creek that is believed to be intermittent in the upstream section.
Temporal Representation:
In 2002 the SWAMP Program performed continuous monitoring of temperature at 15 minute intervals for periods of 1-2 weeks in each of three different seasons: winter (3 sites), spring (5 sites), and summer dry season (5 sites).
Environmental Conditions:
QAPP Information:
All samples were collected and analyzed using procedures comparable with the SWAMP Quality Assurance Management Plan (SWRCB 2002).
Line of Evidence (LOE) for Decision ID 154220, Benthic Community Effects
Region 2
Arroyo Las Positas
LOE ID:
288502
Pollutant:
Temperature, water
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Not Recorded
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
16
Number of Exceedances:
8
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed SWAMP RWB2 Monitoring data for Arroyo Las Positas to determine beneficial use support and results are as follows: 8 of 16 samples exceeded the water quality threshold for Temperature.
Spatial Representation:
The samples were collected at 1 monitoring site: 204ALP040 (Airway Blvd. Exit).
Temporal Representation:
The samples were collected between the dates of 2019-07-23 and 2019-07-23
Environmental Conditions:
QAPP Information:
SWRCB. 2018. This is a placeholder reference for data that was collected after QAPP requirements were developed, but exempt from the requirements..
Line of Evidence (LOE) for Decision ID 150849, Ammonia
Region 2
Arroyo Las Positas
LOE ID:
279543
Pollutant:
Ammonia (Unionized)
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
1
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2019 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 1 of 1 samples exceeded the water quality threshold for Ammonia as N, Unionized.
Water Quality Control Plan, San Francisco Bay Basin, Chapter III Water Quality Objectives, Section 3.3.20 Un-Ionized Ammonia: The discharge of wastes shall not cause receiving waters to contain concentrations of un-ionized ammonia in excess 0.025 mg/l (as N), expressed as an annual median.
Temperature objectives for surface waters are specified in the San Francisco Bay Regional Water Quality Control Plan. The following temperature objectives apply to surface waters: “- The natural receiving water temperature of inland surface waters shall not be altered unless it can be demonstrated to the satisfaction of the Regional Board that such alteration in temperature does not adversely affect beneficial uses. - The temperature of any cold or warm freshwater habitat shall not be increased by more than 5°F (2.8°C) above natural receiving water temperature.”
Per Effects of Temperature, Dissolved Oxygen/Total Dissolved Gas, Ammonia, and pH on Salmonids (Carter 2008, Moyle 1976, and USEPA 1977), the lethal temperature evaluation guideline for both the steelhead adult migration and holding and the steelhead juvenile growth and rearing life stages is 24°C.
Line of Evidence (LOE) for Decision ID 154220, Benthic Community Effects
Region 2
Arroyo Las Positas
LOE ID:
306899
Pollutant:
Benthic-Macroinvertebrate Bioassessments
LOE Subgroup:
Population/Community Degradation
Matrix:
Water
Fraction:
None
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
1
Data and Information Type:
Benthic macroinvertebrate surveys
Data Used to Assess Water Quality:
Water Board staff assessed data for 204ALP110 to determine beneficial use support and the results are as follows: 1 of 1 samples exceeded the threshold. CSCI scores were from 0.42352 to 0.42352.
All waters shall be maintained free of toxic substances in concentrations that are lethal to or that produce significant alterations in population or community ecology or receiving water biota. In addition, the health and life history characteristics of aquatic organisms in waters affected by controllable water quality factors shall not differ significantly from those for the same waters in areas unaffected by controllable water quality factors.
The California Stream Condition Index (CSCI) is a biological scoring tool that helps aquatic resource managers translate complex data about benthic macroinvertebrates found living in a stream into an overall measure of stream health. The CSCI score is calculated by comparing the expected condition with actual (observed) results (Rehn, A.C. et al., 2015). CSCI scores range from 0 (highly degraded) to greater than 1 (equivalent to reference). CSCI scoring of biological condition are as follows (per the scientific paper supporting the development of the CSCI scoring tool): greater than or equal to 0.92 = likely intact condition, 0.91 to 0.80 = possibly altered condition, 0.79 to 0.63 = likely altered condition, less than or equal to 0.62 = very likely altered condition. Sites with scores below 0.79 are considered to have exceeded the water quality objective for the aquatic life beneficial use.Â
Water Board staff assessed BASMAA RMC Monitoring in WY2017 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Ammonia as N, Unionized.
Water Quality Control Plan, San Francisco Bay Basin, Chapter III Water Quality Objectives, Section 3.3.20 Un-Ionized Ammonia: The discharge of wastes shall not cause receiving waters to contain concentrations of un-ionized ammonia in excess 0.025 mg/l (as N), expressed as an annual median.
Line of Evidence (LOE) for Decision ID 150849, Ammonia
Region 2
Arroyo Las Positas
LOE ID:
279387
Pollutant:
Ammonia (Unionized)
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2017 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Ammonia as N, Unionized.
Water Quality Control Plan, San Francisco Bay Basin, Chapter III Water Quality Objectives, Section 3.3.20 Un-Ionized Ammonia: The discharge of wastes shall not cause receiving waters to contain concentrations of un-ionized ammonia in excess 0.025 mg/l (as N), expressed as an annual median.
Line of Evidence (LOE) for Decision ID 150849, Ammonia
Region 2
Arroyo Las Positas
LOE ID:
279807
Pollutant:
Ammonia (Unionized)
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
1
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2015 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 1 of 1 samples exceeded the water quality threshold for Ammonia as N, Unionized.
Water Quality Control Plan, San Francisco Bay Basin, Chapter III Water Quality Objectives, Section 3.3.20 Un-Ionized Ammonia: The discharge of wastes shall not cause receiving waters to contain concentrations of un-ionized ammonia in excess 0.025 mg/l (as N), expressed as an annual median.
Line of Evidence (LOE) for Decision ID 150849, Ammonia
Region 2
Arroyo Las Positas
LOE ID:
279542
Pollutant:
Ammonia (Unionized)
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
DECISION ID
141699
Region 2
Arroyo Las Positas
Pollutant:
Chloride
Final Listing Decision:
List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:
New Decision
Revision Status
Revised
Sources:
A Source Unknown
TMDL Priority:
Low
Impairment from Pollutant or Pollution:
Pollutant
Regional Board Conclusion:
This pollutant is being considered for placement on the CWA section 303(d) List under section 3.2 of the Listing Policy. Under section 3.2 a single line of evidence is necessary to assess listing status.
30 lines of evidence are available in the administrative record to assess this pollutant. 6 of 9 dissolved samples and 12 of 18 total samples for both COLD and WARM Beneficial Uses exceed the evaluation guidelines.
Based on the readily available data and information, the weight of evidence indicates that there is sufficient justification in favor of placing this water segment-pollutant combination on the CWA section 303(d) List.
This conclusion is based on the staff findings that: 1. The data used satisfies the data quality requirements of section 6.1.4 of the Policy. 2. The data used satisfies the data quantity requirements of section 6.1.5 of the Policy. 3. 18 of 27 total samples exceed the evaluation criteria and this exceeds the allowable frequency listed in Table 3.2 of the Listing Policy. 4. Pursuant to section 3.11 of the Listing Policy, no additional data and information are available indicating that standards are not met.
Regional Board Decision Recommendation:
After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should be placed on the section 303(d) list because applicable water quality standards are exceeded and a pollutant contributes to or causes the problem.
State Board Review of Regional Board Conclusion and Recommendation:
State Board Decision Recommendation:
After review of this Regional Board decision, SWRCB staff recommend the decision be approved by the State Board.
Listing Extent:
Line of Evidence (LOE) for Decision ID 141699, Chloride
Region 2
Arroyo Las Positas
LOE ID:
281388
Pollutant:
Chloride
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
1
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2015 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 1 of 1 samples exceeded the water quality threshold for Chloride.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factoh="33%">Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2019 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Ammonia as N, Unionized.
Water Quality Control Plan, San Francisco Bay Basin, Chapter III Water Quality Objectives, Section 3.3.20 Un-Ionized Ammonia: The discharge of wastes shall not cause receiving waters to contain concentrations of un-ionized ammonia in excess 0.025 mg/l (as N), expressed as an annual median.
Line of Evidence (LOE) for Decision ID 150849, Ammonia
Region 2
Arroyo Las Positas
LOE ID:
279734
Pollutant:
Ammonia (Unionized)
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2020 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Ammonia as N, Unionized.
Water Quality Control Plan, San Francisco Bay Basin, Chapter III Water Quality Objectives, Section 3.3.20 Un-Ionized Ammonia: The discharge of wastes shall not cause receiving waters to contain concentrations of un-ionized ammonia in excess 0.025 mg/l (as N), expressed as an annual median.
The samples were collected at 1 monitoring site: 204R04816 (Arroyo Las Positas approx 350m west of Portola Ave).
Temporal Representation:
The samples were collected between the dates of 2020-06-04 and 2020-06-04
Environmental Conditions:
QAPP Information:
EOA, Inc.. 2000. Creek Status anrs shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
The chloride criterion continuous concentration (expressed as a 4-day average) to protect aquatic life in freshwater is 230000 ug/L (230 mg/L)(USEPA National Recommended Water Quality Criteria, 2006).
Line of Evidence (LOE) for Decision ID 141699, Chloride
Region 2
Arroyo Las Positas
LOE ID:
281055
Pollutant:
Chloride
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
1
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2016 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 1 of 1 samples exceeded the water quality threshold for Chloride.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
The chloride criterion continuous concentration (expressed as a 4-day average) to protect aquatic life in freshwater is 230000 ug/L (230 mg/L)(USEPA National Recommended Water Quality Criteria, 2006).
Line of Evidence (LOE) for Decision ID 141699, Chloride
Region 2
Arroyo Las Positas
LOE ID:
281506
Pollutant:
Chloride
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
4
Number of Exceedances:
2
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2019 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 2 of 4 samples exceeded the water quality threshold for Chloride.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
The chloride criterion continuous concentration (expressed as a 4-day average) to protect aquatic life in freshwater is 230000 ug/L (230 mg/L)(USEPA National Recommended Water Quality Criteria, 2006).
Line of Evidence (LOE) for Decision ID 141699, Chloride
Region 2
Arroyo Las Positas
LOE ID:
280881
Pollutant:
Chloride
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2020 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceededd Pesticides & Toxicity Monitoring Quality Assurance Project.
Line of Evidence (LOE) for Decision ID 150849, Ammonia
Region 2
Arroyo Las Positas
LOE ID:
279265
Pollutant:
Ammonia (Unionized)
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2020 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Ammonia as N, Unionized.
Water Quality Control Plan, San Francisco Bay Basin, Chapter III Water Quality Objectives, Section 3.3.20 Un-Ionized Ammonia: The discharge of wastes shall not cause receiving waters to contain concentrations of un-ionized ammonia in excess 0.025 mg/l (as N), expressed as an annual median.
Line of Evidence (LOE) for Decision ID 150849, Ammonia
Region 2
Arroyo Las Positas
LOE ID:
279416
Pollutant:
Ammonia (Unionized)
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2014 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Ammonia as N, Unionized.
Water Quality Control Plan, San Francisco Bay Basin, Chapter III Water Quality Objectives, Section 3.3.20 Un-Ionized Ammonia: The discharge of wastes shall not cause receiving waters to contain concentrations of un-ionized ammonia in excess 0.025 mg/l (as N), expressed as an annual median.
Line of Evidence (LOE) for Decision ID 150849, Ammonia
Region 2
Arroyo Las Positas
LOE ID:
278924
Pollutant:
Ammonia (Unionized)
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
1
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2015 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 1 of 1 samples exceeded the water quality threshold for Ammonia as N, Unionized.
Water Quality Control Plan, San Francisco Bay Basin, Chapter III Water Quality Objectives, Section 3.3.20 Un-Ionized Ammonia: The discharge of wastes shall not cause receiving waters to contain concentrations of un-ionized ammonia in excess 0.025 mg/l (as N), expressed as an annual median.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
The chloride criterion continuous concentration (expressed as a 4-day average) to protect aquatic life in freshwater is 230000 ug/L (230 mg/L)(USEPA National Recommended Water Quality Criteria, 2006).
Line of Evidence (LOE) for Decision ID 141699, Chloride
Region 2
Arroyo Las Positas
LOE ID:
281511
Pollutant:
Chloride
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
1
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2015 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 1 of 1 samples exceeded the water quality threshold for Chloride.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
The chloride criterion continuous concentration (expressed as a 4-day average) to protect aquatic life in freshwater is 230000 ug/L (230 mg/L)(USEPA National Recommended Water Quality Criteria, 2006).
The San Francisco Bay Regional Water Quality Board Basin Plan stated that the discharge of wastes shall not cause receiving water to contain concentrations of un-ionized ammonia in excess of 0.025mg/l annual median.For Total Ammonia: EPA's Lifetime Health advisory level for total ammonia is 30.0 mg/L as stated on page 8 of the 2006 edition of the drinking water standards and health advisories. This Advisory Level is defined as the concentration of a chemical in drinking water that is not expected to cause any adverse noncarcinogenic effects for up to ten days of exposure.
Line of Evidence (LOE) for Decision ID 141699, Chloride
Region 2
Arroyo Las Positas
LOE ID:
281204
Pollutant:
Chloride
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
4
Number of Exceedances:
3
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2019 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 3 of 4 samples exceeded the water quality threshold for Chloride.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
The chloride criterion continuous concentration (expressed as a 4-day average) to protect aquatic life in freshwater is 230000 ug/L (230 mg/L)(USEPA National Recommended Water Quality Criteria, 2006).
Line of Evidence (LOE) for Decision ID 141699, Chloride
Region 2
Arroyo Las Positas
LOE ID:
281126
Pollutant:
Chloride
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Dissolved
Beneficial Use:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2012 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Ammonia as N, Unionized.
Water Quality Control Plan, San Francisco Bay Basin, Chapter III Water Quality Objectives, Section 3.3.20 Un-Ionized Ammonia: The discharge of wastes shall not cause receiving waters to contain concentrations of un-ionized ammonia in excess 0.025 mg/l (as N), expressed as an annual median.
Line of Evidence (LOE) for Decision ID 150849, Ammonia
Region 2
Arroyo Las Positas
LOE ID:
279987
Pollutant:
Ammonia (Unionized)
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2014 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Ammonia as N, Unionized.
Water Quality Control Plan, San Francisco Bay Basin, Chapter III Water Quality Objectives, Section 3.3.20 Un-Ionized Ammonia: The discharge of wastes shall not cause receiving waters to contain concentrations of un-ionized ammonia in excess 0.025 mg/l (as N), expressed as an annual median.
Water Board staff assessed SWAMP RWB2 Monitoring data for Arroyo Las Positas to determine beneficial use support and results are as follows: 2 of 4 samples exceeded the water quality threshold for Chloride.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
The chloride criterion continuous concentration (expressed as a 4-day average) to protect aquatic life in freshwater is 230000 ug/L (230 mg/L)(USEPA National Recommended Water Quality Criteria, 2006).
Line of Evidence (LOE) for Decision ID 141699, Chloride
Region 2
Arroyo Las Positas
LOE ID:
281198
Pollutant:
Chloride
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2020 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Chloride.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
The chloride criterion continuous concentration (expressed as a 4-day average) to protect aquatic life in freshwater is 230000 ug/L (230 mg/L)(USEPA National Recommended Water Quality Criteria, 2006).
Line of Evidence (LOE) for Decision ID 141699, Chloride
Region 2
Arroyo Las Positas
LOE ID:
281230
Pollutant:
Chloride
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
4
Number of Exceedances:
2
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2019 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 2 of 4 samples exceeded the water quality threshold for Chloride.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
The chloride criterion continuous concentration (expressed as a 4-day average) to protect aquatic life in freshwater is 230000 ug/L (230 mg/L)(USEPA National Recommended Water Quality Criteria, 2006).
Line of Evidence (LOE) for Decision ID 141699, Chloride
Region 2
Creek Status Monitoring Program
Quality Assurance Project Plan
Line of Evidence (LOE) for Decision ID 150849, Ammonia
Region 2
Arroyo Las Positas
LOE ID:
279755
Pollutant:
Ammonia (Unionized)
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed SWAMP RWB2 Monitoring data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Ammonia as N, Unionized.
Water Quality Control Plan, San Francisco Bay Basin, Chapter III Water Quality Objectives, Section 3.3.20 Un-Ionized Ammonia: The discharge of wastes shall not cause receiving waters to contain concentrations of un-ionized ammonia in excess 0.025 mg/l (as N), expressed as an annual median.
Line of Evidence (LOE) for Decision ID 150849, Ammonia
Region 2
Arroyo Las Positas
LOE ID:
280288
Pollutant:
Ammonia (Unionized)
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2014 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Ammonia as N, Unionized.
Data RefeWIDTH: 100%; text-align: left; PADDING-TOP: 3px; font-smooth: always">Arroyo Las Positas
LOE ID:
281864
Pollutant:
Chloride
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
1
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2014 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 1 of 1 samples exceeded the water quality threshold for Chloride.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
The chloride criterion continuous concentration (expressed as a 4-day average) to protect aquatic life in freshwater is 230000 ug/L (230 mg/L)(USEPA National Recommended Water Quality Criteria, 2006).
Line of Evidence (LOE) for Decision ID 141699, Chloride
Region 2
Arroyo Las Positas
LOE ID:
281015
Pollutant:
Chloride
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2019 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Chloride.
Water Quality Control Plan, San Francisco Bay Basin, Chapter III Water Quality Objectives, Section 3.3.20 Un-Ionized Ammonia: The discharge of wastes shall not cause receiving waters to contain concentrations of un-ionized ammonia in excess 0.025 mg/l (as N), expressed as an annual median.
Line of Evidence (LOE) for Decision ID 150849, Ammonia
Region 2
Arroyo Las Positas
LOE ID:
279417
Pollutant:
Ammonia (Unionized)
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2014 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Ammonia as N, Unionized.
Water Quality Control Plan, San Francisco Bay Basin, Chapter III Water Quality Objectives, Section 3.3.20 Un-Ionized Ammonia: The discharge of wastes shall not cause receiving waters to contain concentrations of un-ionized ammonia in excess 0.025 mg/l (as N), expressed as an annual median.
Line of Evidence (LOE) f"67%">Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
The chloride criterion continuous concentration (expressed as a 4-day average) to protect aquatic life in freshwater is 230000 ug/L (230 mg/L)(USEPA National Recommended Water Quality Criteria, 2006).
Line of Evidence (LOE) for Decision ID 141699, Chloride
Region 2
Arroyo Las Positas
LOE ID:
281494
Pollutant:
Chloride
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
1
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2012 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 1 of 1 samples exceeded the water quality threshold for Chloride.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
The chloride criterion continuous concentration (expressed as a 4-day average) to protect aquatic life in freshwater is 230000 ug/L (230 mg/L)(USEPA National Recommended Water Quality Criteria, 2006).
Water Board staff assessed SWAMP RWB2 Monitoring data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Ammonia as N, Unionized.
Water Quality Control Plan, San Francisco Bay Basin, Chapter III Water Quality Objectives, Section 3.3.20 Un-Ionized Ammonia: The discharge of wastes shall not cause receiving waters to contain concentrations of un-ionized ammonia in excess 0.025 mg/l (as N), expressed as an annual median.
Line of Evidence (LOE) for Decision ID 150849, Ammonia
Region 2
Arroyo Las Positas
LOE ID:
279267
Pollutant:
Ammonia (Unionized)
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed SWAMP RWB2 Monitoring data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Ammonia as N, Unionized.
Line of Evidence (LOE) for Decision ID 141699, Chloride
Region 2
Arroyo Las Positas
LOE ID:
281205
Pollutant:
Chloride
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2019 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Chloride.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
The chloride criterion continuous concentration (expressed as a 4-day average) to protect aquatic life in freshwater is 230000 ug/L (230 mg/L)(USEPA National Recommended Water Quality Criteria, 2006).
Line of Evidence (LOE) for Decision ID 141699, Chloride
Region 2
Arroyo Las Positas
LOE ID:
281141
Pollutant:
Chloride
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
4
Number of Exceedances:
3
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2019 data for Arroyo Las Positas to "left" valign="top" width="33%">Water Quality Objective/Criterion:
Water Quality Control Plan, San Francisco Bay Basin, Chapter III Water Quality Objectives, Section 3.3.20 Un-Ionized Ammonia: The discharge of wastes shall not cause receiving waters to contain concentrations of un-ionized ammonia in excess 0.025 mg/l (as N), expressed as an annual median.
Line of Evidence (LOE) for Decision ID 150849, Ammonia
Region 2
Arroyo Las Positas
LOE ID:
279470
Pollutant:
Ammonia (Unionized)
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
1
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2019 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 1 of 1 samples exceeded the water quality threshold for Ammonia as N, Unionized.
Water Quality Control Plan, San Francisco Bay Basin, Chapter III Water Quality Objectives, Section 3.3.20 Un-Ionized Ammonia: The discharge of wastes shall not cause receiving waters to contain concentrations of un-ionized ammonia in excess 0.025 mg/l (as N), expressed as an annual median.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
The chloride criterion continuous concentration (expressed as a 4-day average) to protect aquatic life in freshwater is 230000 ug/L (230 mg/L)(USEPA National Recommended Water Quality Criteria, 2006).
Line of Evidence (LOE) for Decision ID 141699, Chloride
Region 2
Arroyo Las Positas
LOE ID:
281866
Pollutant:
Chloride
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
1
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2017 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 1 of 1 samples exceeded the water quality threshold for Chloride.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
The chloride criterion continuous concentration (expressed as a 4-day average) to protect aquatic life in freshwater is 230000 ug/L (230 mg/L)(USEPA National Recommended Water Quality Criteria, 2006).
Water Board staff assessed BASMAA RMC Monitoring in WY2017 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Ammonia as N, Unionized.
Water Quality Control Plan, San Francisco Bay Basin, Chapter III Water Quality Objectives, Section 3.3.20 Un-Ionized Ammonia: The discharge of wastes shall not cause receiving waters to contain concentrations of un-ionized ammonia in excess 0.025 mg/l (as N), expressed as an annual median.
Line of Evidence (LOE) for Decision ID 150849, Ammonia
Region 2
Arroyo Las Positas
LOE ID:
278524
Pollutant:
Nitrogen, ammonia (Total Ammonia)
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2020 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Ammonia as N.
The Total Ammonia criterion continuous concentration (expressed as a 30-day average) to protect aquatic life in freshwater is Temperature and pH dependent, and was calculated accordresentation:
The samples were collected between the dates of 2017-05-25 and 2017-05-25
Environmental Conditions:
QAPP Information:
EOA, Inc., Applied Marine Sciences, Armand Ruby Consulting . 2016. BASMAA Regional Monitoring Coalition Creek Status and Pesticides & Toxicity Monitoring Quality Assurance Project Plan.
Line of Evidence (LOE) for Decision ID 141699, Chloride
Region 2
Arroyo Las Positas
LOE ID:
281493
Pollutant:
Chloride
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Dissolved
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
4
Number of Exceedances:
2
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed SWAMP RWB2 Monitoring data for Arroyo Las Positas to determine beneficial use support and results are as follows: 2 of 4 samples exceeded the water quality threshold for Chloride.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
The chloride criterion continuous concentration (expressed as a 4-day average) to protect aquatic life in freshwater is 230000 ug/L (230 mg/L)(USEPA National Recommended Water Quality Criteria, 2006).
Line of Evidence (LOE) for Decision ID 150849, Ammonia
Region 2
Arroyo Las Positas
LOE ID:
278746
Pollutant:
Nitrogen, ammonia (Total Ammonia)
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2017 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Ammonia as N.
The Total Ammonia criterion continuous concentration (expressed as a 30-day average) to protect aquatic life in freshwater is Temperature and pH dependent, and was calculated according to the formula listed in the Aquatic Life Ambient Water Quality Criteria for Ammonia - Freshwater 2013 document.
Line of Evidence (LOE) for Decision ID 150849, Ammonia
Region 2
Arroyo Las Positas
Water
Fraction:
Dissolved
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
2
Number of Exceedances:
2
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed SWAMP RWB2 Monitoring data for Arroyo Las Positas to determine beneficial use support and results are as follows: 2 of 2 samples exceeded the water quality threshold for Chloride.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
The chloride criterion continuous concentration (expressed as a 4-day average) to protect aquatic life in freshwater is 230000 ug/L (230 mg/L)(USEPA National Recommended Water Quality Criteria, 2006).
Line of Evidence (LOE) for Decision ID 141699, Chloride
Region 2
Arroyo Las Positas
LOE ID:
281390
Pollutant:
Chloride
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
1
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2017 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 1 of 1 samples exceeded the water quality threshold for Chloride.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
Objective/Criterion Reference:
LOE ID:
278766
Pollutant:
Nitrogen, ammonia (Total Ammonia)
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
1
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2019 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 1 of 1 samples exceeded the water quality threshold for Ammonia as N.
The Total Ammonia criterion continuous concentration (expressed as a 30-day average) to protect aquatic life in freshwater is Temperature and pH dependent, and was calculated according to the formula listed in the Aquatic Life Ambient Water Quality Criteria for Ammonia - Freshwater 2013 document.
Line of Evidence (LOE) for Decision ID 150849, Ammonia
Region 2
Arroyo Las Positas
LOE ID:
278017
Pollutant:
Nitrogen, ammonia (Total Ammonia)
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2012 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Ammonia as N.
The Total Ammonia criterion continuous concentration (expressed as a 30-day average) to protect aquatic life in freshwater is Temperature and pH dependent, and was calculated according to the formula listed in the Aquatic Life Ambient Water Quality Criteria for Ammonia - Freshwater 2013 document.
Line of Evidence (LOE) for Decision ID 150849, Ammonia
Region 2
Arroyo Las Positas
LOE ID:
277221
Pollutant:
Nitrogen, ammonia (Total Ammonia)
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2016 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Ammonia as N.
The Total Ammonia criterion continuous concentration (expressed as a 30-day average) to protect aquatic life in freshwater is Temperature and pH dependent, and was calculated according to the formula listed in the Aquatic Life Ambient Water Quality Criteria for Ammonia - Freshwater 2013 document.
Line of Evidence (LOE) for Decision ID 150849, Ammonia
Region 2
Arroyo Las Positas
LOE ID:
279269
Pollutant:
Ammonia (Unionized)
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2012 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Ammonia as N, Unionized.
Water Quality Control Plan, San Francisco Bay Basin, Chapter III Water Quality Objectives, Section 3.3.20 Un-Ionized Ammonia: The discharge of wastes shall not cause receiving waters to contain concentrations of un-ionized ammonia in excess 0.025 mg/l (as N), expressed as an annual median.
ds.ca.gov/water_issues/programs/tmdl/records/region_2/2010/ref3754.pdf" >Water Quality Control Plan (Basin Plan) San Francisco Bay Basin (Region 2)
Evaluation Guideline:
The chloride criterion continuous concentration (expressed as a 4-day average) to protect aquatic life in freshwater is 230000 ug/L (230 mg/L)(USEPA National Recommended Water Quality Criteria, 2006).
Line of Evidence (LOE) for Decision ID 141699, Chloride
Region 2
Arroyo Las Positas
LOE ID:
281229
Pollutant:
Chloride
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
1
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2017 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 1 of 1 samples exceeded the water quality threshold for Chloride.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
The chloride criterion continuous concentration (expressed as a 4-day average) to protect aquatic life in freshwater is 230000 ug/L (230 mg/L)(USEPA National Recommended Water Quality Criteria, 2006).
Line of Evidence (LOE) for Decision ID 141699, Chloride
Region 2
Arroyo Las Positas
LOE ID:
280898
Pollutant:
Chloride
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
1
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2014 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 1 of 1 samples exceeded the water quality threshold for Chloride.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
The chloride criterion continuous concentration (expressed as a 4-day average) to protect aquatic life in freshwater is 230000 ug/L (230 mg/L)(USEPA National Recommended Water Quality Criteria, 2006).
Line of Evidence (LOE) for Decision ID 141699, Chloride
Region 2
Arroyo Las Positas
LOE ID:
281888
Pollutant:
Chloride
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
1
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2016 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 1 of 1 samples exceeded the water quality threshold for Chloride.
DECISION ID
154220
Region 2
Arroyo Las Positas
Pollutant:
Benthic Community Effects
Final Listing Decision:
List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:
New Decision
Revision Status
Revised
Sources:
A Source Unknown
TMDL Priority:
Low
Impairment from Pollutant or Pollution:
Pollutant
Regional Board Conclusion:
For the 2024 Integrated Report, USEPA disapproved 44 benthic community effects decisions that were placed in Category 3. The data and information demonstrated that the biological community is degraded, and the waterbody is listed on the 303(d) list with at least one pollutant impairment affecting an aquatic life beneficial use. This was an interim approach used to provide time to develop the methodology to associate the pollutant as a potential cause of the degraded biology. The USEPA reviewed the appropriateness of these category placements and indicated that the most appropriate classification for these 44 waterbody-pollutant combinations is Category 5. This decision was updated to reflect direction from USEPA.
Benthic Community Effects are being considered for placement on the CWA section 303(d) List under sections 3.9 of the Listing Policy. Under section 3.9, additional lines of evidence (LOEs) associating the Benthic Community Effects decision with a water or sediment concentration of pollutants other than benthic-macroinvertebrate bioassessment or habitat assessment LOEs are necessary to place a water body on the 303(d) List for Benthic Community Effects.
Twenty-one line(s) of evidence evaluating benthic-macroinvertebrate bioassessment data is/are available in the administrative record to assess this indicator. Twenty-one of 21 benthic-macroinvertebrate samples exceed the California Stream Condition Index (CSCI) impairment threshold. Additionally, there are associated pollutant impairments on the waterbody (including but not necessarily limited to Ammonia, Chloride, Temperature, and pH). Based on the readily available data and information, the weight of evidence indicates that there is sufficient justification for placing Benthic Community Effects in this waterbody segment on the CWA section 303(d) List.
This conclusion is based on the staff findings that:
1. The data used satisfies the data quality requirements of section 6.1.4 of the Policy. 2. The data used satisfies the data quantity requirements of section 6.1.5 of the Policy. 3. 21 of 21 benthic-macroinvertebrate bioassessment samples had CSCI scores below 0.79. Therefore, this water body is exceeding the water quality threshold for the protection of the WARM and/or COLD beneficial use. 4. Pursuant to section 3.9 of the Listing Policy, the water segment has associated pollutant(s) samples that exceed water quality objectives. 5. Pursuant to section 3.11 of the Listing Policy, no additional data and information are available indicating that standards are not met.
Regional Board Decision Recommendation:
After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list. The readily available data and information is insufficient to determine, with the power and confidence of the Listing Policy, the applicable beneficial use support rating.
State Board Review of Regional Board Conclusion and Recommendation:
State Board Decision Recommendation:
After review of this Regional Board decision, SWRCB staff recommend the decision be approved by the State Board.
Listing Extent:
Line of Evidence (LOE) for Decision ID 154220, Benthic Community Effects
Region 2
Arroyo Las Positas
LOE ID:
306910
Pollutant:
Benthic-Macroinvertebrate Bioassessments
LOE Subgroup:
Population/Community Degradation
Matrix:
Water
Fraction:
None
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
1
Data and Information Type:
Benthic macroinvertebrate surveys
Data Used to Assess Water Quality:
Water Board staff assessed data for 204R00068 to determine beneficial use support and the results are as follows: 1 of 1 samples exceeded the threshold. CSCI scores were from 0.508619 to 0.508619.
All waters shall be maintained free of toxic substances in concentrations that are lethal to or that produce significant alterations in population or community ecology or receiving water biota. In addition, the health and life history characteristics of aquatic organisms in waters affected by controllable water quality factors shall not differ significantly from those for the same waters in areas unaffected by controllable water quality factors.
The California Stream Condition Index (CSCI) is a biological scoring tool that helps aquatic resource managers translate complex data about benthic macroinvertebrates found living in a stream into an overall measure of stream health. The CSCI score is calculated by comparing the expected condition with actual (observed) results (Rehn, A.C. et al., 2015). CSCI scores range from 0 (highly degraded) to greater than 1 (equivalent to reference). CSCI scoring of biological condition are as follows (per the scientific paper supporting the development of the CSCI scoring tool): greater than or equal to 0.92 = likely intact condition, 0.91 to 0.80 = possibly altered condition, 0.79 to 0.63 = likely altered condition, less than or equal to 0.62 = very likely altered condition. Sites with scores below 0.79 are considered to have exceeded the water quality objective for the aquatic life beneficial use.Â
Line of Evidence (LOE) for Decision ID 154220, Benthic Community Effects
Region 2
Arroyo Las Positas
LOE ID:
286949
Pollutant:
pH
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
None
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
1
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2015 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 1 of 1 samples exceeded the water quality threshold for pH.
Water Quality Control Plan, San Francisco Bay Basin, Chapter III Water Quality Objectives, Section 3.3.9 pH states: The pH shall not be depressed below 6.5 nor raised above 8.5. This encompasses the pH range usually found in waters within the basin. Controllable water quality factors shall not cause changes greater than 0.5 units in normal ambient pH levels.
Line of Evidence (LOE) for Decision ID 154220, Benthic Community Effects
Region 2
Arroyo Las Positas
LOE ID:
306696
Pollutant:
Benthic-Macroinvertebrate Bioassessments
LOE Subgroup:
Population/Community Degradation
Matrix:
Water
Fraction:
None
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
1
Data and Information Type:
Benthic macroinvertebrate surveys
Data Used to Assess Water Quality:
Water Board staff assessed data for 204ALP080 to determine beneficial use support and the results are as follows: 1 of 1 samples exceeded the threshold. CSCI scores were from 0.471466909 to 0.471466909.
All waters shall be maintained free of toxic substances in concentrations that are lethal to or that produce significant alterations in population or community ecology or receiving water biota. In addition, the health and life history characteristics of aquatic organisms in waters affected by controllable water quality factors shall not differ significantly from those for the same waters in areas unaffected by controllable water quality factors.
The California Stream Condition Index (CSCI) is a biological scoring tool that helps aquatic resource managers translate complex data about benthic macroinvertebrates found living in a stream into an overall measure of stream health. The CSCI score is calculated by comparing the expected condition with actual (observed) results (Rehn, A.C. et al., 2015). CSCI scores range from 0 (highly degraded) to greater than 1 (equivalent to reference). CSCI scoring of biological condition are as follows (per the scientific paper supporting the development of the CSCI scoring tool): greater than or equal to 0.92 = likely intact condition, 0.91 to 0.80 = possibly altered condition, 0.79 to 0.63 = likely altered condition, less than or equal to 0.62 = very likely altered condition. Sites with scores below 0.79 are considered to have exceeded the water quality objective for the aquatic life beneficial use.Â
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
The chloride criterion continuous concentration (expressed as a 4-day average) to protect aquatic life in freshwater is 230000 ug/L (230 mg/L)(USEPA National Recommended Water Quality Criteria, 2006).
Line of Evidence (LOE) for Decision ID 141699, Chloride
Region 2
Arroyo Las Positas
LOE ID:
280723
Pollutant:
Chloride
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
1
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2012 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 1 of 1 samples exceeded the water quality threshold for Chloride.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
The chloride criterion continuous concentration (expressed as a 4-day average) to protect aquatic life in freshwater is 230000 ug/L (230 mg/L)(USEPA National Recommended Water Quality Criteria, 2006).
Line of Evidence (LOE) for Decision ID 141699, Chloride
Region 2
Arroyo Las Positas
LOE ID:
281383
Pollutant:
Chloride
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Dissolved
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
3
Number of Exceedances:
2
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed SWAMP RWB2 Monitoring data for Arroyo Las Positas to determine beneficial use support and results are as follows: 2 of 3 samples exceeded the water quality threshold for Chloride.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
The chloride criterion continuous concentration (expressed as a 4-day average) to protect aquatic life in freshwater is 230000 ug/L (230 mg/L)(USEPA National Recommended Water Quality Criteria, 2006).
Line of Evidence (LOE) for Decision ID 141699, Chloride
Region 2
Arroyo Las Positas
LOE ID:
280970
Pollutant:
Chloride
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Dissolved
Beneficial Useference for data that was collected after QAPP requirements were developed, but exempt from the requirements.
Line of Evidence (LOE) for Decision ID 154220, Benthic Community Effects
Region 2
Arroyo Las Positas
LOE ID:
306947
Pollutant:
Benthic-Macroinvertebrate Bioassessments
LOE Subgroup:
Population/Community Degradation
Matrix:
Water
Fraction:
None
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
1
Data and Information Type:
Benthic macroinvertebrate surveys
Data Used to Assess Water Quality:
Water Board staff assessed data for 204ALP105 to determine beneficial use support and the results are as follows: 1 of 1 samples exceeded the threshold. CSCI scores were from 0.308794066 to 0.308794066.
All waters shall be maintained free of toxic substances in concentrations that are lethal to or that produce significant alterations in population or community ecology or receiving water biota. In addition, the health and life history characteristics of aquatic organisms in waters affected by controllable water quality factors shall not differ significantly from those for the same waters in areas unaffected by controllable water quality factors.
The California Stream Condition Index (CSCI) is a biological scoring tool that helps aquatic resource managers translate complex data about benthic macroinvertebrates found living in a stream into an overall measure of stream health. The CSCI score is calculated by comparing the expected condition with actual (observed) results (Rehn, A.C. et al., 2015). CSCI scores range from 0 (highly degraded) to greater than 1 (equivalent to reference). CSCI scoring of biological condition are as follows (per the scientific paper supporting the development of the CSCI scoring tool): greater than or equal to 0.92 = likely intact condition, 0.91 to 0.80 = possibly altered condition, 0.79 to 0.63 = likely altered condition, less than or equal to 0.62 = very likely altered condition. Sites with scores below 0.79 are considered to have exceeded the water quality objective for the aquatic life beneficial use.Â
Line of Evidence (LOE) for Decision ID 154220, Benthic Community Effects
Region 2
Arroyo Las Positas
LOE ID:
306936
Pollutant:
Benthic-Macroinvertebrate Bioassessments
LOE Subgroup:
Population/Community Degradation
Matrix:
Water
Fraction:
None
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
1
Data and Information Type:
Benthic macroinvertebrate surveys
Data Used to Assess Water Quality:
Water Board staff assessed data for 204R03737 to determine beneficial use support and the results are as follows: 1 of 1 samples exceeded the threshold. CSCI scores were from 0.24344593 to 0.24344593.
All waters shall be maintained free of toxic substances in concentrations that are lethal to or that produce significant alterations in population or community ecology or receiving water biota. In addition, the health and life history characteristics of aquatic organisms in waters affected by controllable water quality factors shall not differ significantly from those for the same waters in areas unaffected by controllable water quality factors.
The California Stream Condition Index (CSCI) is a biological scoring tool that helps aquatic resource managers translate complex data about benthic macroinvertebrates found living in a stream into an overall measure of stream health. The CSCI score is calculated by comparing the expected condition with actual (observed) results (Rehn, A.C. et al., 2015). CSCI scores range from 0 (highly degraded) to greater than 1 (equivalent to reference). CSCI scoring of biological condition are as follows (per the scientific paper supporting the development of the CSCI scoring tool): greater than or equal to 0.92 = likely intact condition, 0.91 to 0.80 = possibly altered condition, 0.79 to 0.63 = likely altered condition, less than or equal to 0.62 = very likely altered condition. Sites with scores below 0.79 are considered to have exceeded the water quality objective for the aquatic life beneficial use.Â
Line of Evidence (LOE) for Decision ID 154220, Benthic Community Effects
Region 2
Arroyo Las Positas
LOE ID:
306946
Pollutant:
Benthic-Macroinvertebrate Bioassessments
LOE Subgroup:
Population/Community Degradation
Matrix:
Water
Fraction:
None
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
2
Number of Exceedances:
2
Data and Information Type:
Benthic macroinvertebrate surveys
Data Used to Assess Water Quality:
Water Board staff assessed data for 204ALP075 to determine beneficial use support and the results are as follows: 2 of 2 samples exceeded the threshold. CSCI scores were from 0.487324516 to 0.570380695.
Water Board staff assessed SWAMP RWB2 Monitoring data for Arroyo Las Positas to determine beneficial use support and results are as follows: 2 of 3 samples exceeded the water quality threshold for Chloride.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
The chloride criterion continuous concentration (expressed as a 4-day average) to protect aquatic life in freshwater is 230000 ug/L (230 mg/L)(USEPA National Recommended Water Quality Criteria, 2006).
Line of Evidence (LOE) for Decision ID 141699, Chloride
Region 2
Arroyo Las Positas
LOE ID:
281403
Pollutant:
Chloride
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
1
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2017 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 1 of 1 samples exceeded the water quality threshold for Chloride.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
All waters shall be maintained free of toxic substances in concentrations that are lethal to or that produce significant alterations in population or community ecology or receiving water biota. In addition, the health and life history characteristics of aquatic organisms in waters affected by controllable water quality factors shall not differ significantly from those for the same waters in areas unaffected by controllable water quality factors.
The California Stream Condition Index (CSCI) is a biological scoring tool that helps aquatic resource managers translate complex data about benthic macroinvertebrates found living in a stream into an overall measure of stream health. The CSCI score is calculated by comparing the expected condition with actual (observed) results (Rehn, A.C. et al., 2015). CSCI scores range from 0 (highly degraded) to greater than 1 (equivalent to reference). CSCI scoring of biological condition are as follows (per the scientific paper supporting the development of the CSCI scoring tool): greater than or equal to 0.92 = likely intact condition, 0.91 to 0.80 = possibly altered condition, 0.79 to 0.63 = likely altered condition, less than or equal to 0.62 = very likely altered condition. Sites with scores below 0.79 are considered to have exceeded the water quality objective for the aquatic life beneficial use.Â
Line of Evidence (LOE) for Decision ID 154220, Benthic Community Effects
Region 2
Arroyo Las Positas
LOE ID:
306923
Pollutant:
Benthic-Macroinvertebrate Bioassessments
LOE Subgroup:
Population/Community Degradation
Matrix:
Water
Fraction:
None
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
1
Data and Information Type:
Benthic macroinvertebrate surveys
Data Used to Assess Water Quality:
Water Board staff assessed data for 204R01945 to determine beneficial use support and the results are as follows: 1 of 1 samples exceeded the threshold. CSCI scores were from 0.370353 to 0.370353.
All waters shall be maintained free of toxic substances in concentrations that are lethal to or that produce significant alterations in population or community ecology or receiving water biota. In addition, the health and life history characteristics of aquatic organisms in waters affected by controllable water quality factors shall not differ significantly from those for the same waters in areas unaffected by controllable water quality factors.
The California Stream Condition Index (CSCI) is a biological scoring tool that helps aquatic resource managers translate complex data about benthic macroinvertebrates found living in a stream into an overall measure of stream health. The CSCI score is calculated by comparing the expected condition with actual (observed) results (Rehn, A.C. et al., 2015). CSCI scores range from 0 (highly degraded) to greater than 1 (equivalent to reference). CSCI scoring of biological condition are as follows (per the scientific paper supporting the development of the CSCI scoring tool): greater than or equal to 0.92 = likely intact condition, 0.91 to 0.80 = possibly alterride criterion continuous concentration (expressed as a 4-day average) to protect aquatic life in freshwater is 230000 ug/L (230 mg/L)(USEPA National Recommended Water Quality Criteria, 2006).
Line of Evidence (LOE) for Decision ID 141699, Chloride
Region 2
Arroyo Las Positas
LOE ID:
281330
Pollutant:
Chloride
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2014 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Chloride.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
The chloride criterion continuous concentration (expressed as a 4-day average) to protect aquatic life in freshwater is 230000 ug/L (230 mg/L)(USEPA National Recommended Water Quality Criteria, 2006).
Line of Evidence (LOE) for Decision ID 141699, Chloride
Region 2
Arroyo Las Positas
LOE ID:
281331
Pollutant:
Chloride
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
1
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2014 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 1 of 1 samples exceeded the water quality threshold for Chloride.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
The chloride criterion continuous concentration (expressed as a 4-day average) to protect aquatic life in freshwater is 230000 ug/L (230 mg/L)(USEPA National Recommended Water Quality Criteria, 2006).
Line of Evidence (LOE) for Decision ID 141699, Chloride
Region 2
Arroyo Las Positas
LOE ID:
281183
Pollutant:
Chloride
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2014 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Chloride.
Line of Evidence (LOE) for Decision ID 154220, Benthic Community Effects
Region 2
Arroyo Las Positas
LOE ID:
306924
Pollutant:
Benthic-Macroinvertebrate Bioassessments
LOE Subgroup:
Population/Community Degradation
Matrix:
Water
Fraction:
None
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
1
Data and Information Type:
Benthic macroinvertebrate surveys
Data Used to Assess Water Quality:
Water Board staff assessed data for 204R02116 to determine beneficial use support and the results are as follows: 1 of 1 samples exceeded the threshold. CSCI scores were from 0.5312 to 0.5312.
All waters shall be maintained free of toxic substances in concentrations that are lethal to or that produce significant alterations in population or community ecology or receiving water biota. In addition, the health and life history characteristics of aquatic organisms in waters affected by controllable water quality factors shall not differ significantly from those for the same waters in areas unaffected by controllable water quality factors.
The California Stream Condition Index (CSCI) is a biological scoring tool that helps aquatic resource managers translate complex data about benthic macroinvertebrates found living in a stream into an overall measure of stream health. The CSCI score is calculated by comparing the expected condition with actual (observed) results (Rehn, A.C. et al., 2015). CSCI scores range from 0 (highly degraded) to greater than 1 (equivalent to reference). CSCI scoring of biological condition are as follows (per the scientific paper supporting the development of the CSCI scoring tool): greater than or equal to 0.92 = likely intact condition, 0.91 to 0.80 = possibly altered condition, 0.79 to 0.63 = likely altered condition, less than or equal to 0.62 = very likely altered condition. Sites with scores below 0.79 are considered to have exceeded the water quality objective for the aquatic life beneficial use.Â
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
The chloride criterion continuous concentration (expressed as a 4-day average) to protect aquatic life in freshwater is 230000 ug/L (230 mg/L)(USEPA National Recommended Water Quality Criteria, 2006).
Line of Evidence (LOE) for Decision ID 141699, Chloride
Region 2
Arroyo Las Positas
LOE ID:
280985
Pollutant:
Chloride
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Dissolved
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
2
Number of Exceedances:
2
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed SWAMP RWB2 Monitoring data for Arroyo Las Positas to determine beneficial use support and results are as follows: 2 of 2 samples exceeded the water quality threshold for Chloride.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
The chloride criterion continuous concentration (expressed as a 4-day average) to protect aquatic life in freshwater is 230000 ug/L (230 mg/L)(USEPA National Recommended Water Quality Criteria, 2006).
Line of Evidence (LOE) for Decision ID 141699, Chloride
Region 2
Arroyo Las Positas
LOE ID:
281027
Pollutant:
Chloride
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
1
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2014 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 1 of 1 samples exceeded the water quality threshold for Chloride.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
The chloride criterion continuous concentration (expressed as a 4-day average) to protect aquatic life in freshwater is 230000 ug/L (230 mg/L)(USEPA National Recommended Water Quality Criteria, 2006).
Line of Evidence (LOE) for Decision ID 154220, Benthic Community Effects
Region 2
Arroyo Las Positas
LOE ID:
306912
Pollutant:
Benthic-Macroinvertebrate Bioassessments
LOE Subgroup:
Population/Community Degradation
Matrix:
Water
Fraction:
None
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
1
Data and Information Type:
Benthic macroinvertebrate surveys
Data Used to Assess Water Quality:
Water Board staff assessed data for 204R01023 to determine beneficial use support and the results are as follows: 1 of 1 samples exceeded the threshold. CSCI scores were from 0.359973 to 0.359973.
All waters shall be maintained free of toxic substances in concentrations that are lethal to or that produce significant alterations in population or community ecology or receiving water biota. In addition, the health and life history characteristics of aquatic organisms in waters affected by controllable water quality factors shall not differ significantly from those for the same waters in areas unaffected by controllable water quality factors.
The California Stream Condition Index (CSCI) is a biological scoring tool that helps aquatic resource managers translate complex data about benthic macroinvertebrates found living in a stream into an overall measure of stream health. The CSCI score is calculated by comparing the expected condition with actual (observed) results (Rehn, A.C. et al., 2015). CSCI scores range from 0 (highly degraded) to greater than 1 (equivalent to reference). CSCI scoring of biological condition are as follows (per the scientific paper supporting the development of the CSCI scoring tool): greater than or equal to 0.92 = likely intact condition, 0.91 to 0.80 = possibly altered condition, 0.79 to 0.63 = likely altered condition, less than or equal to 0.62 = very likely altered condition. Sites with scores below 0.79 are considered to have exceeded the water quality objective for the aquatic life beneficial use.Â
Line of Evidence (LOE) for Decision ID 154220, Benthic Community Effects
Region 2
Arroyo Las Positas
LOE ID:
306935
Pollutant:
Benthic-Macroinvertebrate Bioassessments
LOE Subgroup:
Population/Community Degradation
Matrix:
Water
Fraction:
None
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
1
Data and Information Type:
Benthic macroinvertebrate surveys
Data Used to Assess Water Quality:
Water Board staff assessed data for 204R03327 to determine beneficial use support and the results are as follows: 1 of 1 samples exceeded the threshold. CSCI scores were from 0.483150561 to 0.483150561.
All waters shall be maintained free of toxic substances in concentrations that are lethal to or that produce significant alterations in population or community ecology or receiving water biota. In addition, the health and life history characteristics of aquatic organisms in waters affected by controllable water quality factors shall not differ significantly from those for the same waters in areas unaffected by controllable water quality factors.
The California Stream Condition Index (CSCI) is a biological scoring tool that helps aquatic resource managers translate complex data about benthic macroinvertebrates found living in a stream into an overall measure of stream health. The CSCI score is calculated by comparing the expected condition with actual (observed) results (Rehn, A.C. et al., 2015). CSCI scores range from 0 (highly degraded) to greater than 1 (equivalent to reference). CSCI scoring of biological condition are as follows (per the scientific paper supporting the development of the CSCI scoring tool): greater than or equal to 0.92 = likely intact condition, 0.91 to 0.80 = possibly altered condition, 0.79 to 0.63 = likely altered condition, less than or equal to 0.62 = very likely altered condition. Sites with scores below 0.79 are considered to have exceeded the water quality objective for the aquatic life beneficial use.Â
Line of Evidence (LOE) for Decision ID 154220, Benthic Community Effects
Region 2
Arroyo Las Positas
LOE ID:
306911
Pollutant:
Benthic-Macroinvertebrate Bioassessments
LOE Subgroup:
Population/Community Degradation
Matrix:
Water
Fraction:
None
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
1
Data and Information Type:
Benthic macroinvertebrate surveys
Data Used to Assess Water Quality:
Water Board staff assessed data for 204R00665 to determine beneficial use support and the results are as follows: 1 of 1 samples exceeded the threshold. CSCI scores were from 0.616622 to 0.616622.
All waters shall be maintained free of toxic substances in concentrations that are lethal to or that produce significant alterations in population or community ecology or receiving water biota. In
DECISION ID
141726
Region 2
Arroyo Las Positas
Pollutant:
Temperature, water
Final Listing Decision:
List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:
Do Not List on 303(d) list (TMDL required list)(2018)
Revision Status
Revised
Sources:
A Source Unknown
TMDL Priority:
Low
Impairment from Pollutant or Pollution:
Pollutant
Regional Board Conclusion:
This pollutant is being considered for placement on the CWA section 303(d) List under section 3.2 of the Listing Policy. Under section 3.2 a single line of evidence is necessary to assess listing status.
35 lines of evidence are available in the administrative record to assess this pollutant. Nine of fifty-three grab samples exceed the 24C lethal threshold protecting the COLD Beneficial Use. Seven of thirteen samples exceed the 17C threshold for the 7-day average of daily mean temperature, and twenty-two of fifty-one samples exceed the threshold for the protection of the fish migration Beneficial Use.
Based on the readily available data and information, the weight of evidence indicates that there is sufficient justification in favor of placing this water segment-pollutant combination on the CWA section 303(d) List.
This conclusion is based on the staff findings that: 1. The data used satisfies the data quality requirements of section 6.1.4 of the Policy. 2. The data used satisfies the data quantity requirements of section 6.1.5 of the Policy. 3. Nine of fifty-three grab samples exceed the 24C lethal threshold protecting the COLD Beneficial Use. Seven of thirteen samples exceed the 17C threshold for the 7-day average of daily mean temperature, and twenty-two of fifty-one samples exceed the threshold for the protection of the fish migration Beneficial Use and this exceeds the allowable frequency listed in Table 3.2 of the Listing Policy. 4. Pursuant to section 3.11 of the Listing Policy, no additional data and information are available indicating that standards are not met.
Regional Board Decision Recommendation:
After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should be placed on the section 303(d) list because applicable water quality standards are exceeded and a pollutant contributes to or causes the problem.
State Board Review of Regional Board Conclusion and Recommendation:
State Board Decision Recommendation:
After review of this Regional Board decision, SWRCB staff recommend the decision be approved by the State Board.
Listing Extent:
Line of Evidence (LOE) for Decision ID 141726, Temperature, water
Region 2
Arroyo Las Positas
LOE ID:
30213
Pollutant:
Temperature, water
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
None
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
13
Number of Exceedances:
7
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water quality assessment was conducted at the Arroyo Las Positas watershed as part of SWAMP study in 2002. Continuous field monitoring at 15 minute increments of temperature, dissolved oxygen, pH and specific conductance was conducted to determine temporal variability in basic water quality at three locations. Continuous monitoring sondes were deployed 13 times at 3 or 5 monitoring locations during winter wet, spring wet and summer dry seasons. The measured temperatures ranged from 3.89oC to 32.1oC and varied with season and location. The 7-day mean temperature threshold for steelhead of 17 °C was exceeded during 7 out of 13 deployments. The 7-day moving average was consistently high (above 20oC) at all 5 monitoring locations during summer sampling season only (June-July 2002).
Temperature objectives for enclosed bays and estuaries are specified in the "Water Quality Control Plan for Control of Temperature in the Coastal and Interstate Waters and Enclosed Bays of California" including any revisions to the plan. In addition, the following temperature objectives apply to surface waters: The natural receiving water temperature of intrastate waters shall not be altered unless it can be demonstrated to the satisfaction of the Regional Board that such an alteration does not adversely affect beneficial uses. The temperature of any cold or warm freshwater habitat shall not be increased by more than 5°F (2.8°C) above natural receiving water temperature.
Sullivan et al. (2000) reviewed a wide range of studies incorporating information from laboratory-based research, field observations, and risk assessment approaches and developed criteria for assessing temperature risk to aquatic life. The 7-day mean temperature (maximum value of a 7-day moving average of the daily mean temperature) of 14.8°C was established as the upper threshold criterion for coho salmon and 17.0°C for steelhead trout. The risk assessment approach used by Sullivan et al. (2000)suggest that temperatures exceeding the above thresholds will cause a 10% reduction in average growth compared to optimal conditions.
Temperature was measured at three or five sites in the Arroyo Las Positas watershead. Four monitoring sites are located in the mainstream of Arroyo Las Positas Creek while one site (ALP105) is located in Altamont Creek that is believed to be intermittent in the upstream section.
Temporal Representation:
In 2002 the SWAMP Program performed continuous monitoring of temperature at 15 minute intervals for periods of 1-2 weeks in each of three different seasons: winter (3 sites), spring (5 sites), and summer dry season (5 sites).
Environmental Conditions:
QAPP Information:
All samples were collected and analyzed using procedures comparable with the SWAMP Quality Assurance Management Plan (SWRCB 2002).
Line of Evidence (LOE) for Decision ID 141726, Temperature, water
Region 2
Arroyo Las Positas
LOE ID:
288883
Pollutant:
Temperature, water
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Not Recorded
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2019 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Temperature.
Non-SWAMPaddition, the health and life history characteristics of aquatic organisms in waters affected by controllable water quality factors shall not differ significantly from those for the same waters in areas unaffected by controllable water quality factors.
The California Stream Condition Index (CSCI) is a biological scoring tool that helps aquatic resource managers translate complex data about benthic macroinvertebrates found living in a stream into an overall measure of stream health. The CSCI score is calculated by comparing the expected condition with actual (observed) results (Rehn, A.C. et al., 2015). CSCI scores range from 0 (highly degraded) to greater than 1 (equivalent to reference). CSCI scoring of biological condition are as follows (per the scientific paper supporting the development of the CSCI scoring tool): greater than or equal to 0.92 = likely intact condition, 0.91 to 0.80 = possibly altered condition, 0.79 to 0.63 = likely altered condition, less than or equal to 0.62 = very likely altered condition. Sites with scores below 0.79 are considered to have exceeded the water quality objective for the aquatic life beneficial use.Â
Line of Evidence (LOE) for Decision ID 154220, Benthic Community Effects
Region 2
Arroyo Las Positas
LOE ID:
306922
Pollutant:
Benthic-Macroinvertebrate Bioassessments
LOE Subgroup:
Population/Community Degradation
Matrix:
Water
Fraction:
None
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
1
Data and Information Type:
Benthic macroinvertebrate surveys
Data Used to Assess Water Quality:
Water Board staff assessed data for 204R01433 to determine beneficial use support and the results are as follows: 1 of 1 samples exceeded the threshold. CSCI scores were from 0.342084 to 0.342084.
All waters shall be maintained free of toxic substances in concentrations that are lethal to or that produce significant alterations in population or community ecology or receiving water biota. In addition, the health and life history characteristics of aquatic organisms in waters affected by controllable water quality factors shall not differ significantly from those for the same waters in areas unaffected by controllable water quality factors.
The California Stream Condition Index (CSCI) is a biological scoring tool that helps aquatic resource managers translate complex data about benthic macroinvertebrates found living in a stream into an overall measure of stream health. The CSCI score is calculated by comparing the expected condition with actual (observed) results (Rehn, A.C. et al., 2015). CSCI scores range from 0 (highly degraded) to greater than 1 (equivalent to reference). CSCI scoring of biological condition are as follows (per the scientific paper supporting the development of the CSCI scoring tool): greater than or equal to 0.92 = likely intact condition, 0.91 to 0.80 = possibly altered condition, 0.79 to 0.63 = likely altered condition, less than or equal to 0.62 = very likely altered condition. Sites with scores below 0.79 are considered to have exceeded the water quality objective for the aquatic life beneficial use.Â
Guideline Ref
Water Quality Objective/Criterion:
Temperature objectives for surface waters are specified in the San Francisco Bay Regional Water Quality Control Plan. The following temperature objectives apply to surface waters: “- The natural receiving water temperature of inland surface waters shall not be altered unless it can be demonstrated to the satisfaction of the Regional Board that such alteration in temperature does not adversely affect beneficial uses. - The temperature of any cold or warm freshwater habitat shall not be increased by more than 5°F (2.8°C) above natural receiving water temperature.”
Per Effects of Temperature, Dissolved Oxygen/Total Dissolved Gas, Ammonia, and pH on Salmonids (Carter 2008, Moyle 1976, and USEPA 1977), the lethal temperature evaluation guideline for both the steelhead adult migration and holding and the steelhead juvenile growth and rearing life stages is 24°C.
Line of Evidence (LOE) for Decision ID 141726, Temperature, water
Region 2
Arroyo Las Positas
LOE ID:
288910
Pollutant:
Temperature, water
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Not Recorded
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2017 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Temperature.
Temperature objectives for surface waters are specified in the San Francisco Bay Regional Water Quality Control Plan. The following temperature objectives apply to surface waters: “- The natural receiving water temperature of inland surface waters shall not be altered unless it can be demonstrated to the satisfaction of the Regional Board that such alteration in temperature does not adversely affect beneficial uses. - The temperature of any cold or warm freshwater habitat shall not be increased by more than 5°F (2.8°C) above natural receiving water temperature.”
Per Effects of Temperature, Dissolved Oxygen/Total Dissolved Gas, Ammonia, and pH on Salmonids (Carter 2008, Moyle 1976, and USEPA 1977), the lethal temperature evaluation guideline for both the steelhead adult migration and holding and the steelhead juvenile growth and rearing life stages is 24°C.
Line of Evidence (LOE) for Decision ID 141726, Temperature, water
Region 2
Arroyo Las Positas
LOE ID:
288723
Pollutant:
Temperature, water
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Not Recorded
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2020 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Temperature.
Temperature objectives for surface waters are specified in the San Francisco Bay Regional Water Quality Control Plan. The following temperature objectives apply to surface waters: “- The natural receiving water temperature of inland surface waters shall not be altered unless it can be demonstrated to the satisfaction of the Regional Board that such alteration in temperature does not adversely affect beneficial uses. - The temperature of any cold or warm freshwater habitat shall not be increased by more than 5°F (2.8°C) above natural receiving water temperature.”
Per Effects of Temperature, Dissolved Oxygen/Total Dissolved Gas, Ammonia, and pH on Salmonids (Carter 2008, Moyle 1976, and USEPA 1977), the lethal temperature evaluation guideline for both the steelhead adult migration and holding and the steelhead juvenile growth and rearing life stages is 24°C.
Line of Evidence (LOE) for Decision ID 154220, Benthic Community Effects
Region 2
Arroyo Las Positas
LOE ID:
286749
Pollutant:
pH
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
None
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
12
Number of Exceedances:
2
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed SWAMP RWB2 Monitoring data for Arroyo Las Positas to determine beneficial use support and results are as follows: 2 of 12 samples exceeded the water quality threshold for pH.
Water Quality Control Plan, San Francisco Bay Basin, Chapter III Water Quality Objectives, Section 3.3.9 pH states: The pH shall not be depressed below 6.5 nor raised above 8.5. This encompasses the pH range usually found in waters within the basin. Controllable water quality factors shall not cause changes greater than 0.5 units in normal ambient pH levels.
Line of Evidence (LOE) for Decision ID 141726, Temperature, water
Region 2
Arroyo Las Positas
LOE ID:
288502
Pollutant:
Temperature, water
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Not Recorded
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
16
Number of Exceedances:
8
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed SWAMP RWB2 Monitoring data for Arroyo Las Positas to determine beneficial use support and results are as follows: 8 of 16 samples exceeded the water quality threshold for Temperature.
Temperature objectives for surface waters are specified in the San Francisco Bay Regional Water Quality Control Plan. The following temperature objectives apply to surface waters: “- The natural receiving water temperature of inland surface waters shall not be altered unless it can be demonstrated to the satisfaction of the Regional Board that such alteration in temperature does not adversely affect beneficial uses. - The temperature of any cold or warm freshwater habitat shall not be increased by more than 5°F (2.8°C) above natural receiving water temperature.”
Per Effects of Temperature, Dissolved Oxygen/Total Dissolved Gas, Ammonia, and pH on Salmonids (Carter 2008, Moyle 1976, and USEPA 1977), the lethal temperature evaluation guideline for both the steelhead adult migration and holding and the steelhead juvenile growth and rearing life stages is 24°C.
The samples were collected at 1 monitoring site: 204ALP040 (Airway Blvd. Exit).
Temporal Representation:
The samples were collected between the dates of 2011-03-02 and 2019-08-29
Environmental Conditions:
QAPP Information:
SWRCB. 2018. This is a placeholder reference for data that was collected after QAPP requirements were developed, but exempt from the requirements..
Water
Fraction:
None
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
15
Number of Exceedances:
7
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed SWAMP RWB2 Monitoring data for Arroyo Las Positas to determine beneficial use support and results are as follows: 7 of 15 samples exceeded the water quality threshold for pH.
Water Quality Control Plan, San Francisco Bay Basin, Chapter III Water Quality Objectives, Section 3.3.9 pH states: The pH shall not be depressed below 6.5 nor raised above 8.5. This encompasses the pH range usually found in waters within the basin. Controllable water quality factors shall not cause changes greater than 0.5 units in normal ambient pH levels.
Line of Evidence (LOE) for Decision ID 154220, Benthic Community Effects
Region 2
Arroyo Las Positas
LOE ID:
306898
Pollutant:
Benthic-Macroinvertebrate Bioassessments
LOE Subgroup:
Population/Community Degradation
Matrix:
Water
Fraction:
None
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
1
Data and Information Type:
Benthic macroinvertebrate surveys
Data Used to Assess Water Quality:
Water Board staff assessed data for 204ALP100 to determine beneficial use support and the results are as follows: 1 of 1 samples exceeded the threshold. CSCI scores were from 0.382736 to 0.382736.
All waters shall be maintained free of toxic substances in concentrations that are lethal to or that produce significant alterations in population or community ecology or receiving water biota. In addition, the health and life history characteristics of aquatic organisms in waters affected by controllable water quality factors shall not differ significantly from those for the same waters in areas unaffected by controllable water quality factors.
Line of Evidence (LOE) for Decision ID 141726, Temperature, water
Region 2
Arroyo Las Positas
LOE ID:
288636
Pollutant:
Temperature, water
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Not Recorded
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
11
Number of Exceedances:
1
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed SWAMP RWB2 Monitoring data for Arroyo Las Positas to determine beneficial use support and results are as follows: 1 of 11 samples exceeded the water quality threshold for Temperature.
Temperature objectives for surface waters are specified in the San Francisco Bay Regional Water Quality Control Plan. The following temperature objectives apply to surface waters: “- The natural receiving water temperature of inland surface waters shall not be altered unless it can be demonstrated to the satisfaction of the Regional Board that such alteration in temperature does not adversely affect beneficial uses. - The temperature of any cold or warm freshwater habitat shall not be increased by more than 5°F (2.8°C) above natural receiving water temperature.”
Per Effects of Temperature, Dissolved Oxygen/Total Dissolved Gas, Ammonia, and pH on Salmonids (Carter 2008, Moyle 1976, and USEPA 1977), the lethal temperature evaluation guideline for both the steelhead adult migration and holding and the steelhead juvenile growth and rearing life stages is 24°C.
Line of Evidence (LOE) for Decision ID 154220, Benthic Community Effects
Region 2
Arroyo Las Positas
LOE ID:
306694
Pollutant:
Benthic-Macroinvertebrate Bioassessments
LOE Subgroup:
Population/Community Degradation
Matrix:
Water
Fraction:
None
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
2
Number of Exceedances:
2
Data and Information Type:
Benthic macroinvertebrate surveys
Data Used to Assess Water Quality:
Water Board staff assessed data for 204ALP040 to determine beneficial use support and the results are as follows: 2 of 2 samples exceeded the threshold. CSCI scores were from 0.294759168 to 0.437916901.
All waters shall be maintained free of toxic substances in concentrations that are lethal to or that produce significant alterations in population or community ecology or receiving water biota. In addition, the health and life history characteristics of aquatic organisms in waters affected by controllable water quality factors shall not differ significantly from those for the same waters in areas unaffected by controllable water quality factors.
The California Stream Condition Index (CSCI) is a biological scoring tool that helps aquatic resource managers translate complex data about benthic macroinvertebrates found living in a stream into an overall measure of stream health. The CSCI score is calculated by comparing the expected condition with actual (observed) results (Rehn, A.C. et al., 2015). CSCI scores range from 0 (highly degraded) to greater than 1 (equivalent to reference). CSCI scoring of biological condition are as follows (per the scientific paper supporting the development of the CSCI scoring tool): greater than or equal to 0.92 = likely intact condition, 0.91 to 0.80 = possibly altered condition, 0.79 to 0.63 = likely altered condition, less than or equal to 0.62 = very likely altered condition. Sites with scores below 0.79 are considered to have exceeded the water quality objective for the aquatic life beneficial use.Â
Samples were collected from 4/26/2001 to 6/12/2019.
<00%; text-align: left; PADDING-TOP: 3px; font-smooth: always">Arroyo Las Positas
LOE ID:
288597
Pollutant:
Temperature, water
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Not Recorded
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2014 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Temperature.
Temperature objectives for surface waters are specified in the San Francisco Bay Regional Water Quality Control Plan. The following temperature objectives apply to surface waters: “- The natural receiving water temperature of inland surface waters shall not be altered unless it can be demonstrated to the satisfaction of the Regional Board that such alteration in temperature does not adversely affect beneficial uses. - The temperature of any cold or warm freshwater habitat shall not be increased by more than 5°F (2.8°C) above natural receiving water temperature.”
Per Effects of Temperature, Dissolved Oxygen/Total Dissolved Gas, Ammonia, and pH on Salmonids (Carter 2008, Moyle 1976, and USEPA 1977), the lethal temperature evaluation guideline for both the steelhead adult migration and holding and the steelhead juvenile growth and rearing life stages is 24°C.
Line of Evidence (LOE) for Decision ID 154220, Benthic Community Effects
Region 2
Arroyo Las Positas
LOE ID:
306695
Pollutant:
Benthic-Macroinvertebrate Bioassessments
LOE Subgroup:
Population/Community Degradation
Matrix:
Water
Fraction:
None
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
1
Data and Information Type:
Benthic macroinvertebrate surveys
Data Used to Assess Water Quality:
Water Board staff assessed data for 204ALP070 to determine beneficial use support and the results are as follows: 1 of 1 samples exceeded the threshold. CSCI scores were from 0.471220175 to 0.471220175.
All waters shall be maintained free of toxic substances in concentrations that are lethal to or that produce significant alterations in population or community ecology or receiving water biota. In addition, the health and life history characteristics of aquatic organisms in waters affected by controllable water quality factors shall not differ significantly from those for the same waters in areas unaffected by controllable water quality factors.
The California Stream Condition Index (CSCI) is a biological scoring tool that helps aquatic resource managers translate complex data about benthic macroinvertebrates found living in a stream into an overall measure of stream health. The CSCI score is calculated by comparing the expected condition with actual (observed) results (Rehn, A.C. et al., 2015). CSCI scores range from 0 (highly degraded) to greater than 1 (equivalent to reference). CSCI scoring of biological condition are as follows (per the scientific paper supporting the development of the CSCI scoring tool): greater than or equal to 0.92 = likely intact condition, 0.91 to 0.80 = possibly altered condition, 0.79 to 0.63 = likely altered condition, less than or equal to 0.62 = very likely altered condition. Sites with scores below 0.79 are considered to have exceeded the water quality objective for the aquatic life beneficial use.Â
Line of Evidence (LOE) for Decision ID 154220, Benthic Community Effects
Region 2
Arroyo Las Positas
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2015 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Temperature.
Temperature objectives for surface waters are specified in the San Francisco Bay Regional Water Quality Control Plan. The following temperature objectives apply to surface waters: “- The natural receiving water temperature of inland surface waters shall not be altered unless it can be demonstrated to the satisfaction of the Regional Board that such alteration in temperature does not adversely affect beneficial uses. - The temperature of any cold or warm freshwater habitat shall not be increased by more than 5°F (2.8°C) above natural receiving water temperature.”
Per Effects of Temperature, Dissolved Oxygen/Total Dissolved Gas, Ammonia, and pH on Salmonids (Carter 2008, Moyle 1976, and USEPA 1977), the lethal temperature evaluation guideline for both the steelhead adult migration and holding and the steelhead juvenile growth and rearing life stages is 24°C.
Line of Evidence (LOE) for Decision ID 141726, Temperature, water
Region 2
Arroyo Las Positas
LOE ID:
298757
Pollutant:
Temperature, water
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Not Recorded
Beneficial Use:
Fish Migration
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2014 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Temperature.
Water Board staff assessed data for 204ALP010 to determine beneficial use support and the results are as follows: 1 of 1 samples exceeded the threshold. CSCI scores were from 0.585281271 to 0.585281271.
All waters shall be maintained free of toxic substances in concentrations that are lethal to or that produce significant alterations in population or community ecology or receiving water biota. In addition, the health and life history characteristics of aquatic organisms in waters affected by controllable water quality factors shall not differ significantly from those for the same waters in areas unaffected by controllable water quality factors.
The California Stream Condition Index (CSCI) is a biological scoring tool that helps aquatic resource managers translate complex data about benthic macroinvertebrates found living in a stream into an overall measure of stream health. The CSCI score is calculated by comparing the expected condition with actual (observed) results (Rehn, A.C. et al., 2015). CSCI scores range from 0 (highly degraded) to greater than 1 (equivalent to reference). CSCI scoring of biological condition are as follows (per the scientific paper supporting the development of the CSCI scoring tool): greater than or equal to 0.92 = likely intact condition, 0.91 to 0.80 = possibly altered condition, 0.79 to 0.63 = likely altered condition, less than or equal to 0.62 = very likely altered condition. Sites with scores below 0.79 are considered to have exceeded the water quality objective for the aquatic life beneficial use.Â
Line of Evidence (LOE) for Decision ID 154220, Benthic Community Effects
Region 2
Arroyo Las Positas
LOE ID:
306900
Pollutant:
Benthic-Macroinvertebrate Bioassessments
LOE Subgroup:
Population/Community Degradation
Matrix:
Water
Fraction:
None
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
1
Data and Information Type:
Benthic macroinvertebrate surveys
Data Used to Assess Water Quality:
Water Board staff assessed data for 204ALP140 to determine beneficial use support and the results are as follows: 1 of 1 samples exceede waters are specified in the San Francisco Bay Regional Water Quality Control Plan. The following temperature objectives apply to surface waters: The natural receiving water temperature of inland surface waters shall not be altered unless it can be demonstrated to the satisfaction of the Regional Board that such alteration in temperature does not adversely affect beneficial uses. The temperature of any cold or warm freshwater habitat shall not be increased by more than 5 degrees F (2.8 degrees C) above natural receiving water temperature.
Scientific literature reviewed by the Washington Department of Ecology and U.S. EPA indicates that stream temperatures higher than 21C are associated with avoidance behavior and migration blockages in steelhead trout.
Line of Evidence (LOE) for Decision ID 141726, Temperature, water
Region 2
Arroyo Las Positas
LOE ID:
298762
Pollutant:
Temperature, water
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Not Recorded
Beneficial Use:
Fish Migration
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2012 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Temperature.
Temperature objectives for surface waters are specified in the San Francisco Bay Regional Water Quality Control Plan. The following temperature objectives apply to surface waters: The natural receiving water temperature of inland surface waters shall not be altered unless it can be demonstrated to the satisfaction of the Regional Board that such alteration in temperature does not adversely affect beneficial uses. The temperature of any cold or warm freshwater habitat shall not be increased by more than 5 degrees F (2.8 degrees C)ed the threshold. CSCI scores were from 0.575051 to 0.575051.
All waters shall be maintained free of toxic substances in concentrations that are lethal to or that produce significant alterations in population or community ecology or receiving water biota. In addition, the health and life history characteristics of aquatic organisms in waters affected by controllable water quality factors shall not differ significantly from those for the same waters in areas unaffected by controllable water quality factors.
The California Stream Condition Index (CSCI) is a biological scoring tool that helps aquatic resource managers translate complex data about benthic macroinvertebrates found living in a stream into an overall measure of stream health. The CSCI score is calculated by comparing the expected condition with actual (observed) results (Rehn, A.C. et al., 2015). CSCI scores range from 0 (highly degraded) to greater than 1 (equivalent to reference). CSCI scoring of biological condition are as follows (per the scientific paper supporting the development of the CSCI scoring tool): greater than or equal to 0.92 = likely intact condition, 0.91 to 0.80 = possibly altered condition, 0.79 to 0.63 = likely altered condition, less than or equal to 0.62 = very likely altered condition. Sites with scores below 0.79 are considered to have exceeded the water quality objective for the aquatic life beneficial use.Â
Line of Evidence (LOE) for Decision ID 154220, Benthic Community Effects
Region 2
Arroyo Las Positas
LOE ID:
306934
Pollutant:
Benthic-Macroinvertebrate Bioassessments
LOE Subgroup:
Population/Community Degradation
Matrix:
Water
Fraction:
None
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
2
Number of Exceedances:
2
Data and Information Type:
Benthic macroinvertebrate surveys
Data Used to Assess Water Quality:
Water Board staff assessed data for 204R03481 to determine beneficial use support and the results are as follows: 2 of 2 samples exceeded the threshold. CSCI scores were from 0.300410439 to 0.384844659.
All waters shall be maintained free of toxic substances in concentrations that are lethal to or that produce significant alterations in population or community ecology or receiving water biota. In addition, the health and life history characteristics of aquatic organisms in waters affected by controllable water quality factors shall not differ significantly from those for the same waters in areas unaffected by controllable water quality factors.
Scientific literature reviewed by the Washington Department of Ecology and U.S. EPA indicates that stream temperatures higher than 21C are associated with avoidance behavior and migration blockages in steelhead trout.
Line of Evidence (LOE) for Decision ID 141726, Temperature, water
Region 2
Arroyo Las Positas
LOE ID:
298580
Pollutant:
Temperature, water
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Not Recorded
Beneficial Use:
Fish Migration
Number of Samples:
10
Number of Exceedances:
3
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed SWAMP RWB2 Monitoring data for Arroyo Las Positas to determine beneficial use support and results are as follows: 3 of 10 samples exceeded the water quality threshold for Temperature.
Temperature objectives for surface waters are specified in the San Francisco Bay Regional Water Quality Control Plan. The following temperature objectives apply to surface waters: The natural receiving water temperature of inland surface waters shall not be altered unless it can be demonstrated to the satisfaction of the Regional Board that such alteration in temperature does not adversely affect beneficial uses. The temperature of any cold or warm freshwater habitat shall not be increased by more than 5 degrees F (2.8 degrees C) above natural receiving water temperature.
Scientific literature reviewed by the Washington Department of Ecology and U.S. EPA indicates that stream temperatures higher than 21C are associated with avoidance behavior and migration blockages in steelhead trout.
Line of Evidence (LOE) for Decision ID 141726, Temperature, water
Region 2
Arroyo Las Positas
LOE ID:
288402
Pollutant:
Temperature, water
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Not Recorded
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2017 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Temperature.
Temperature objectives for surface waters are specified in the San Francisco Bay Regional Water Quality Control Plan. The following temperature objectives apply to surface waters: “- The natural receiving water temperature of inland surface waters shall not be altered unless it can be demonstrated to the satisfaction of the Regional Board that such alteration in temperature does not adversely affect beneficial uses. - The temperature of any cold or warm freshwater habitat shall not be increased by more than 5°F (2.8°C) above natural receiving water temperature.”
Per Effects of Temperature, Dissolved Oxygen/Total Dissolved Gas, Ammonia, and pH on Salmonids (Carter 2008, Moyle 1976, and USEPA 1977), the lethal temperature evaluation guideline for both the steelhead adult migration and holding and the steelhead juvenile growth and rearing life stages is 24°C.
Line of Evidence (LOE) for Decision ID 154220, Benthic Community Effects
Region 2
Arroyo Las Positas
LOE ID:
279491
Pollutant:
Ammonia (Unionized)
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
1
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2019 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 1 of 1 samples exceeded the water quality threshold for Ammonia as N, Unionized.
Water Quality Control Plan, San Francisco Bay Basin, Chapter III Water Quality Objectives, Section 3.3.20 Un-Ionized Ammonia: The discharge of wastes shall not cause receiving waters to contain concentrations of un-ionized ammonia in excess 0.025 mg/l (as N), expressed as an annual median.
Line of Evidence (LOE) for Decision ID 141726, Temperature, water
Region 2
Arroyo Las Positas
LOE ID:
288221
Pollutant:
Temperature, water
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Not Recorded
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2016 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Temperature.
Temperature objectives for surface waters are specified in the San Francisco Bay Regional Water Quality Control Plan. The following temperature objectives apply to surface waters: “- The natural receiving water temperature of inland surface waters shall not be altered unless it can be demonstrated to the satisfaction of the Regional Board that such alteration in temperature does not adversely affect beneficial uses. - The temperature of any cold or warm freshwater habitat shall not be increased by more than 5°F (2.8°C) above natural receiving water temperature.”
Per Effects of Temperature, Dissolved Oxygen/Total Dissolved Gas, Ammonia, and pH on Salmonids (Carter 2008, Moyle 1976, and USEPA 1977), the lethal temperature evaluation guideline for both the steelhead adult migration and holding and the steelhead juvenile growth and rearing life stages is 24°C.
Water Board staff assessed BASMAA RMC Monitoring in WY2015 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 1 of 1 samples exceeded the water quality threshold for Ammonia as N, Unionized.
Water Quality Control Plan, San Francisco Bay Basin, Chapter III Water Quality Objectives, Section 3.3.20 Un-Ionized Ammonia: The discharge of wastes shall not cause receiving waters to contain concentrations of un-ionized ammonia in excess 0.025 mg/l (as N), expressed as an annual median.
Line of Evidence (LOE) for Decision ID 154220, Benthic Community Effects
Region 2
Arroyo Las Positas
LOE ID:
279470
Pollutant:
Ammonia (Unionized)
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
1
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2019 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 1 of 1 samples exceeded the water quality threshold for Ammonia as N, Unionized.
Water Quality Control Plan, San Francisco Bay Basin, Chapter III Water Quality Objectives, Section 3.3.20 Un-Ionized Ammonia: The discharge of wastes shall not cause receiving waters to contain concentrations of un-ionized ammonia in excnbsp;
Spatial Representation:
The samples were collected at 1 monitoring site: 204R02116 (Arroyo Las Positas approx 300m upstream of Airway Blvd.).
Temporal Representation:
The samples were collected between the dates of 2016-05-25 and 2016-05-25
Environmental Conditions:
QAPP Information:
EOA, Inc.. 2016. Creek Status and Pesticides & Toxicity Monitoring Quality Assurance Project.
Line of Evidence (LOE) for Decision ID 141726, Temperature, water
Region 2
Arroyo Las Positas
LOE ID:
288596
Pollutant:
Temperature, water
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Not Recorded
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2014 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Temperature.
Temperature objectives for surface waters are specified in the San Francisco Bay Regional Water Quality Control Plan. The following temperature objectives apply to surface waters: “- The natural receiving water temperature of inland surface waters shall not be altered unless it can be demonstrated to the satisfaction of the Regional Board that such alteration in temperature does not adversely affect beneficial uses. - The temperature of any cold or warm freshwater habitat shall not be increased by more than 5°F (2.8°C) above natural receiving water temperature.”
Per Effects of Temperature, Dissolved Oxygen/Total Dissolved Gas, Ammonia, and pH on Salmonids (Carter 2008, Moyle 1976, and USEPA 1977), the lethal temperature evaluation guideline for both the steelhead adult migration and holding and the steelhead juvenile growth and rearing life stages is 24°C.
Line of Evidence (LOE) for Decision ID 141726, Temperature, water
Region 2
Arroyo Las Positas
LOE ID:
288889
Pollutant:
Temperature, water
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Not Recorded
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed SWAMP RWB2 Monitoring data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Temperature.
Temperature objectives for surface waters are specified in the San Francisco Bay Regional Water Quality Control Plan. The following temperature objectives apply to surface waters: “- The natural receiving water temperature of inland surface waters shall not be altered unless it can be demonstrated to the satisfaction of the Regional Board that such alteration in temperature does not adversely affect beneficial uses. - The temperature of any cold or warm freshwater habitat shall not be increased by more than 5°F (2.8°C) above natural receiving water temperature.”
Per Effects of Temperature, Dissolved Oxygen/Total Dissolved Gas, Ammonia, and pH on Salmonids (Carter 2008, Moyle 1976, and USEPA 1977), the lethal temperature evaluation guideline for both the steelhead adult migration and holding and the steelhead juvenile growth and rearing life stages is 24°C.
Line of Evidence (LOE) for Decision ID 141726, Temperature, water
Region 2
Arroyo Las Positas
LOE ID:
288555
Pollutant:
Temperature, water
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Not Recorded
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2012 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Temperature.
Temperature objectives for surface waters are specified in the San Francisco Bay Regional Water Quality Control Plan. The following temperature objectives apply to surface waters: “- The natural receiving water temperature of inland surface waters shall not be altered unless it can be demonstrated to the satisfaction of the Regional Board that such alteration in temperature does not adversely affect beneficial uses. - The temperature of any cold or warm freshwater habitat shall not be increased by more than 5°F (2.8°C) above natural receiving water temperature.”
Per Effects of Temperature, Dissolved Oxygen/Total Dissolved Gas, Ammonia, and pH on Salmonids (Carter 2008, Moyle 1976, and USEPA 1977), the lethal temperature evaluation guideline for both the steelhead adult migration and holding and the steelhead juvenile growth and rearing life stages is 24°C.
Line of Evidence (LOE) for Decision ID 141726, Temperature, water
Region 2
Arroyo Las Positas
LOE ID:
288581
Pollutant:
Temperature, water
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Not Recorded
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2012 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 sampleess 0.025 mg/l (as N), expressed as an annual median.
Line of Evidence (LOE) for Decision ID 154220, Benthic Community Effects
Region 2
Arroyo Las Positas
LOE ID:
281866
Pollutant:
Chloride
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
1
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2017 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 1 of 1 samples exceeded the water quality threshold for Chloride.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
The chloride criterion continuous concentration (expressed as a 4-day average) to protect aquatic life in freshwater is 230000 ug/L (230 mg/L)(USEPA National Recommended Water Quality Criteria, 2006).
Temperature objectives for surface waters are specified in the San Francisco Bay Regional Water Quality Control Plan. The following temperature objectives apply to surface waters: “- The natural receiving water temperature of inland surface waters shall not be altered unless it can be demonstrated to the satisfaction of the Regional Board that such alteration in temperature does not adversely affect beneficial uses. - The temperature of any cold or warm freshwater habitat shall not be increased by more than 5°F (2.8°C) above natural receiving water temperature.”
Per Effects of Temperature, Dissolved Oxygen/Total Dissolved Gas, Ammonia, and pH on Salmonids (Carter 2008, Moyle 1976, and USEPA 1977), the lethal temperature evaluation guideline for both the steelhead adult migration and holding and the steelhead juvenile growth and rearing life stages is 24°C.
Line of Evidence (LOE) for Decision ID 141726, Temperature, water
Region 2
Arroyo Las Positas
LOE ID:
288850
Pollutant:
Temperature, water
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Not Recorded
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2019 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Temperature.
Temperature objectives for surface waters are specified in the San Francisco Bay Regional Water Quality Control Plan. The following temperature objectives apply to surface waters: “- The natural receiving water temperature of inland surface waters shall not be altered unless it can be demonstrated to the satisfaction of the Regional Board that such alteration in temperature does not adversely affect beneficial uses. - The temperature of any cold or warm freshwater habitat shall not be increased by mING-TOP: 3px; font-smooth: always">Region 2
Arroyo Las Positas
LOE ID:
280970
Pollutant:
Chloride
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Dissolved
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
3
Number of Exceedances:
2
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed SWAMP RWB2 Monitoring data for Arroyo Las Positas to determine beneficial use support and results are as follows: 2 of 3 samples exceeded the water quality threshold for Chloride.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
The chloride criterion continuous concentration (expressed as a 4-day average) to protect aquatic life in freshwater is 230000 ug/L (230 mg/L)(USEPA National Recommended Water Quality Criteria, 2006).
Line of Evidence (LOE) for Decision ID 154220, Benthic Community Effects
Region 2
Arroyo Las Positas
LOE ID:
281126
Pollutant:
Chloride
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Dissolved
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
4
Number of Exceedances:
2
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed SWAMP RWB2 Monitoring data for Arroyo Las Positas to determine beneficial use support and results are as follows: 2 of 4 samples exceeded the water quality threshold for Chloride.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
The chloride criterion continuous concentration (expressed as a 4-day average) to protect aquatic life in freshwater is 230000 ug/L (230 mg/L)(USEPA National Recommended Water Quality Criteria, 2006).
Line of Evidence (LOE) for Decision ID 154220, Benthic Community Effects
Region 2
Arroyo Las Positas
LOE ID:
281315
Pollutant:
Chloride
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Dissolved
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
2
Number of Exceedances:
2
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed SWAMP RWB2 Monitoring data for Arroyo Las Positas to determine beneficial use support and results are as follows: 2 of 2 samples exceeded the water quality threshold for Chloride.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
The chloride criterion continuous concentration (expressed as a 4-day average) to protect aquatic life in freshwater is 230000 ug/L (230 mg/L)(USEPA National Recommended Water Quality Criteria, 2006).
Per Effects of Temperature, Dissolved Oxygen/Total Dissolved Gas, Ammonia, and pH on Salmonids (Carter 2008, Moyle 1976, and USEPA 1977), the lethal temperature evaluation guideline for both the steelhead adult migration and holding and the steelhead juvenile growth and rearing life stages is 24°C.
Line of Evidence (LOE) for Decision ID 141726, Temperature, water
Region 2
Arroyo Las Positas
LOE ID:
288800
Pollutant:
Temperature, water
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Not Recorded
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
12
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed SWAMP RWB2 Monitoring data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 12 samples exceeded the water quality threshold for Temperature.
Temperature objectives for surface waters are specified in the San Francisco Bay Regional Water Quality Control Plan. The following temperature objectives apply to surface waters: “- The natural receiving water temperature of inland surface waters shall not be altered unless it can be demonstrated to the satisfaction of the Regional Board that such alteration in temperature does not adversely affect beneficial uses. - The temperature of any cold or warm freshwater habitat shall not be increased by more than 5°F (2.8°C) above natural receiving water temperature.”
Per Effects of Temperature, Dissolved Oxygen/Total Dissolved Gas, Ammonia, and pH on Salmonids (Carter 2008, Moyle 1976, and USEPA 1977), the lethal temperature evaluation guideline for both the steelhead adult migration and holding and the steelhead juvenile growth and rearing life stages is 24°C.
Line of Evidence (LOE) for Decision ID 141726, Temperature, water
Region 2
Arroyo Las Positas
LOE ID:
288882
Pollutant:
Temperature, water
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Not Recorded
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2019 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Temperature.
Temperature objectives for surface waters are specified in the San Francisco Bay Regional Water Quality Control Plan. The following temperature objectives apply to surface waters: “- The natural receiving water temperature of inland surface waters shall not be altered unless it can be demonstrated to the satisfaction of the Regional Board that such alteration in temperature does not adversely affect beneficial uses. - The temperature of any cold or warm freshwater habitat shall not be increased by more than 5°F (2.8°C) above natural receiving water temperature.”
Per Effects of Temperature, Dissolved Oxygen/Total Dissolved Gas, Ammonia, and pH on Salmonids (Carter 2008, Moyle 1976, and USEPA 1977), the lethal temperature evaluation guideline for both the steelhead adult migration and holding and the steelhead juvenile growth and rearing life stages is 24°C.
Line of Evidence (LOE) for Decision ID 154220, Benthic Community Effects
Region 2
Arroyo Las Positas
LOE ID:
281494
Pollutant:
Chloride
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
1
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2012 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 1 of 1 samples exceeded the water quality threshold for Chloride.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
The chloride criterion continuous concentration (expressed as a 4-day average) to protect aquatic life in freshwater is 230000 ug/L (230 mg/L)(USEPA National Recommended Water Quality Criteria, 2006).
Line of Evidence (LOE) for Decision ID 154220, Benthic Community Effects
Region 2
Arroyo Las Positas
LOE ID:
281888
Pollutant:
Chloride
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
1
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2016 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 1 of 1 samples exceeded the water quality threshold for Chloride.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
The chloride criterion continuous concentration (expressed as a 4-day average) to protect aquatic life in freshwater is 230000 ug/L (230 mg/L)(USEPA National Recommended Water Quality Criteria, 2006).
Line of Evidence (LOE) for Decision ID 154220, Benthic Community Effects
Region 2
Arroyo Las Positas
LOE ID:
281506
Pollutant:
Chloride
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
4
Number of Exceedances:
2
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2019 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 2 of 4 samples exceeded the water quality threshold for Chloride.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
The chloride criterion continuous concentration (expressed as a 4-day average) to protect aquatic life in freshwater is 230000 ug/L (230 mg/L)(USEPA National Recommended Water Quality Critign="top" width="67%">The samples were collected between the dates of 2019-05-15 and 2019-05-15
Environmental Conditions:
QAPP Information:
EOA, Inc.. 2014. Creek Status Monitoring Program Quality Assurance Project Plan.
Line of Evidence (LOE) for Decision ID 141726, Temperature, water
Region 2
Arroyo Las Positas
LOE ID:
288588
Pollutant:
Temperature, water
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Not Recorded
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2018 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Temperature.
Temperature objectives for surface waters are specified in the San Francisco Bay Regional Water Quality Control Plan. The following temperature objectives apply to surface waters: “- The natural receiving water temperature of inland surface waters shall not be altered unless it can be demonstrated to the satisfaction of the Regional Board that such alteration in temperature does not adversely affect beneficial uses. - The temperature of any cold or warm freshwater habitat shall not be increased by more than 5°F (2.8°C) above natural receiving water temperature.”
Per Effects of Temperature, Dissolved Oxygen/Total Dissolved Gas, Ammonia, and pH on Salmonids (Carter 2008, Moyle 1976, and USEPA 1977), the lethal temperature evaluation guideline for both the steelhead adult migration and holding and the steelhead juvenile growth and rearing life stages is 24°C.
Line of Evidence (LOE) for Decision ID 141726, Temperature, water
Region 2
Arroyo Las Positas
LOE ID:
298816
Pollutant:
Temperature, water
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Not Recorded
Beneficial Use:
Fish Migration
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2015 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Temperature.
Temperature objectives for surface waters are specified in the San Francisco Bay Regional Water Quality Control Plan. The following temperature objectives apply to surface waters: The natural receiving water temperature of inland surface waters shall not be altered unless it can be demonstrated to the satisfaction of the Regional Board that such alteration in temperature does not adversely affect beneficial uses. The temperature of any cold or warm freshwater habitat shall not be increased by more than 5 degrees F (2.8 degrees C) above natural receiving water temperature.
Scientific literature reviewed by the Washington Department of Ecology and U.S. EPA indicates that stream temperatures higher than 21C are associated with avoidance behavior and migration blockages in steelhead trout.
Line of Evidence (LOE) for Decision ID 154220, Benthic Community Effects
Region 2
Arroyo Las Positas
LOE ID:
281331
Pollutant:
Chloride
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
1
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2014 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 1 of 1 samples exceeded the water quality threshold for Chloride.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
The chloride criterion continuous concentration (expressed as a 4-day average) to protect aquatic life in freshwater is 230000 ug/L (230 mg/L)(USEPA National Recommended Water Quality Criteria, 2006).
Line of Evidence (LOE) for Decision ID 154220, Benthic Community Effects
Region 2
Arroyo Las Positas
d>
298953
Pollutant:
Temperature, water
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Not Recorded
Beneficial Use:
Fish Migration
Number of Samples:
12
Number of Exceedances:
8
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed SWAMP RWB2 Monitoring data for Arroyo Las Positas to determine beneficial use support and results are as follows: 8 of 12 samples exceeded the water quality threshold for Temperature.
Temperature objectives for surface waters are specified in the San Francisco Bay Regional Water Quality Control Plan. The following temperature objectives apply to surface waters: The natural receiving water temperature of inland surface waters shall not be altered unless it can be demonstrated to the satisfaction of the Regional Board that such alteration in temperature does not adversely affect beneficial uses. The temperature of any cold or warm freshwater habitat shall not be increased by more than 5 degrees F (2.8 degrees C) above natural receiving water temperature.
Scientific literature reviewed by the Washington Department of Ecology and U.S. EPA indicates that stream temperatures higher than 21C are associated with avoidance behavior and migration blockages in steelhead trout.
Line of Evidence (LOE) for Decision ID 141726, Temperature, water
Region 2
Arroyo Las Positas
LOE ID:
298517
Pollutant:
Temperature, water
LOE Subgroup:
Pollutant-Water
LOE ID:
281511
Pollutant:
Chloride
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
1
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2015 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 1 of 1 samples exceeded the water quality threshold for Chloride.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
The chloride criterion continuous concentration (expressed as a 4-day average) to protect aquatic life in freshwater is 230000 ug/L (230 mg/L)(USEPA National Recommended Water Quality Criteria, 2006).
Line of Evidence (LOE) for Decision ID 154220, Benthic Community Effects
Region 2
Arroyo Las Positas
LOE ID:
281141
Pollutant:
Chloride
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
4
Number of Exceedances:
3
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2019 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 3 of 4 samples exceeded the water quality threshold for Chloride.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shalld align="left" valign="top" width="33%">Matrix:
Water
Fraction:
Not Recorded
Beneficial Use:
Fish Migration
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2014 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Temperature.
Temperature objectives for surface waters are specified in the San Francisco Bay Regional Water Quality Control Plan. The following temperature objectives apply to surface waters: The natural receiving water temperature of inland surface waters shall not be altered unless it can be demonstrated to the satisfaction of the Regional Board that such alteration in temperature does not adversely affect beneficial uses. The temperature of any cold or warm freshwater habitat shall not be increased by more than 5 degrees F (2.8 degrees C) above natural receiving water temperature.
Scientific literature reviewed by the Washington Department of Ecology and U.S. EPA indicates that stream temperatures higher than 21C are associated with avoidance behavior and migration blockages in steelhead trout.
Line of Evidence (LOE) for Decision ID 141726, Temperature, water
Region 2
Arroyo Las Positas
LOE ID:
298648
Pollutant:
Temperature, water
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Not Recorded
Beneficial Use:
Fish Migration
Number of Samples:
15
Number of Exceedances:
9
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed SWAMP RWB2 Monitoring data for Arroyo Las Positas to determine beneficial use support and results are as follows: 9 of 15 samples exceeded the water quality threshold for Temperature.
Temperature objectives for surface waters are specified in the San Francisco Bay Regional Water Quality Control Plan. The following temperature objectives apply to surface waters: The natural receiving water temperature of inland surface waters shall not be altered unless it can be demonstrated to the satisfaction of the Regional Board that such alteration in temperature does not adversely affect beneficial uses. The temperature of any cold or warm freshwater habitat shall not be increased by more than 5 degrees F (2.8 degrees C) above natural receiving water temperature.
Scientific literature reviewed by the Washington Department of Ecology and U.S. EPA indicates that stream temperatures higher than 21C are associated with avoidance behavior and migration blockages in steelhead trout.
The chloride criterion continuous concentration (expressed as a 4-day average) to protect aquatic life in freshwater is 230000 ug/L (230 mg/L)(USEPA National Recommended Water Quality Criteria, 2006).
Line of Evidence (LOE) for Decision ID 154220, Benthic Community Effects
Region 2
Arroyo Las Positas
LOE ID:
281864
Pollutant:
Chloride
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
1
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2014 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 1 of 1 samples exceeded the water quality threshold for Chloride.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
The chloride criterion continuous concentration (expressed as a 4-day average) to protect aquatic life in freshwater is 230000 ug/L (230 mg/L)(USEPA National Recommended Water Quality Criteria, 2006).
Water Board staff assessed BASMAA RMC Monitoring in WY2019 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Temperature.
Temperature objectives for surface waters are specified in the San Francisco Bay Regional Water Quality Control Plan. The following temperature objectives apply to surface waters: The natural receiving water temperature of inland surface waters shall not be altered unless it can be demonstrated to the satisfaction of the Regional Board that such alteration in temperature does not adversely affect beneficial uses. The temperature of any cold or warm freshwater habitat shall not be increased by more than 5 degrees F (2.8 degrees C) above natural receiving water temperature.
Scientific literature reviewed by the Washington Department of Ecology and U.S. EPA indicates that stream temperatures higher than 21C are associated with avoidance behavior and migration blockages in steelhead trout.
Line of Evidence (LOE) for Decision ID 141726, Temperature, water
Region 2
Arroyo Las Positas
LOE ID:
298991
Pollutant:
Temperature, water
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Not Recorded
Beneficial Use:
Fish Migration
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2017 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Temperature.
Water Board staff assessed BASMAA RMC Monitoring in WY2017 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 1 of 1 samples exceeded the water quality threshold for Chloride.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
The chloride criterion continuous concentration (expressed as a 4-day average) to protect aquatic life in freshwater is 230000 ug/L (230 mg/L)(USEPA National Recommended Water Quality Criteria, 2006).
Line of Evidence (LOE) for Decision ID 154220, Benthic Community Effects
Region 2
Arroyo Las Positas
LOE ID:
30213
Pollutant:
Temperature, water
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
None
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
13
Number of Exceedances:
7
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Field, Habitat, Toxicity, WQ data from the California Environmental Data Exchange Network assembled for the 2024 Integrated Report in Region 2.
SWAMP Data:
Non-SWAMP
Water Quality Objective/Criterion:
Temperature objectives for surface waters are specified in the San Francisco Bay Regional Water Quality Control Plan. The following temperature objectives apply to surface waters: The natural receiving water temperature of inland surface waters shall not be altered unless it can be demonstrated to the satisfaction of the Regional Board that such alteration in temperature does not adversely affect beneficial uses. The temperature of any cold or warm freshwater habitat shall not be increased by more than 5 degrees F (2.8 degrees C) above natural receiving water temperature.
Scientific literature reviewed by the Washington Department of Ecology and U.S. EPA indicates that stream temperatures higher than 21C are associated with avoidance behavior and migration blockages in steelhead trout.
Line of Evidence (LOE) for Decision ID 141726, Temperature, water
Region 2
Arroyo Las Positas
LOE ID:
298990
Pollutant:
Temperature, water
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Not Recorded
Beneficial Use:
Fish Migration
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2017 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Temperature.
<">Water quality assessment was conducted at the Arroyo Las Positas watershed as part of SWAMP study in 2002. Continuous field monitoring at 15 minute increments of temperature, dissolved oxygen, pH and specific conductance was conducted to determine temporal variability in basic water quality at three locations. Continuous monitoring sondes were deployed 13 times at 3 or 5 monitoring locations during winter wet, spring wet and summer dry seasons. The measured temperatures ranged from 3.89oC to 32.1oC and varied with season and location. The 7-day mean temperature threshold for steelhead of 17 °C was exceeded during 7 out of 13 deployments. The 7-day moving average was consistently high (above 20oC) at all 5 monitoring locations during summer sampling season only (June-July 2002).
Temperature objectives for enclosed bays and estuaries are specified in the "Water Quality Control Plan for Control of Temperature in the Coastal and Interstate Waters and Enclosed Bays of California" including any revisions to the plan. In addition, the following temperature objectives apply to surface waters: The natural receiving water temperature of intrastate waters shall not be altered unless it can be demonstrated to the satisfaction of the Regional Board that such an alteration does not adversely affect beneficial uses. The temperature of any cold or warm freshwater habitat shall not be increased by more than 5°F (2.8°C) above natural receiving water temperature.
Sullivan et al. (2000) reviewed a wide range of studies incorporating information from laboratory-based research, field observations, and risk assessment approaches and developed criteria for assessing temperature risk to aquatic life. The 7-day mean temperature (maximum value of a 7-day moving average of the daily mean temperature) of 14.8°C was established as the upper threshold criterion for coho salmon and 17.0°C for steelhead trout. The risk assessment approach used by Sullivan et al. (2000)suggest that temperatures exceeding the above thresholds will cause a 10% reduction in average growth compared to optimal conditions.
Temperature was measured at three or five sites in the Arroyo Las Positas watershead. Four monitoring sites are located in the mainstream of Arroyo Las Positas Creek while one site (ALP105) is located in Altamont Creek that is believed to be intermittent in the upstream section.
Temporal Representation:
In 2002 the SWAMP Program performed continuous monitoring of temperature at 15 minute intervals for periods of 1-2 weeks in each of three different seasons: winter (3 sites), spring (5 sites), and summer dry season (5 sites).
Environmental Conditions:
QAPP Information:
All samples were collected and analyzed using procedures comparable with the SWAMP Quality Assurance Management Plan (SWRCB 2002).
Line of Evidence (LOE) for Decision ID 154220, Benthic Community Effects
Region 2
Arroyo Las Positas
LOE ID:
288502
Pollutant:
Temperature, water
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Not Recorded
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
16
Number of Exceedances:
8
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed SWAMP RWB2 Monitoring data for Arroyo Las Positas to determine beneficial use support and results are as follows: 8 of 16 samples exceeded the water quality threshold for Temperature.
Water Quality Objective/Criterion:
Temperature objectives for surface waters are specified in the San Francisco Bay Regional Water Quality Control Plan. The following temperature objectives apply to surface waters: The natural receiving water temperature of inland surface waters shall not be altered unless it can be demonstrated to the satisfaction of the Regional Board that such alteration in temperature does not adversely affect beneficial uses. The temperature of any cold or warm freshwater habitat shall not be increased by more than 5 degrees F (2.8 degrees C) above natural receiving water temperature.
Scientific literature reviewed by the Washington Department of Ecology and U.S. EPA indicates that stream temperatures higher than 21C are associated with avoidance behavior and migration blockages in steelhead trout.
Line of Evidence (LOE) for Decision ID 141726, Temperature, water
Region 2
Arroyo Las Positas
LOE ID:
298753
Pollutant:
Temperature, water
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Not Recorded
Beneficial Use:
Fish Migration
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2020 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Temperature.
Temperature objectives for surface waters are specified in the San Francisco Bay Regional Water Quality Control Plan. The following temperature objectives apply to surface waters: The natural receiving w%">Data Reference:
Temperature objectives for surface waters are specified in the San Francisco Bay Regional Water Quality Control Plan. The following temperature objectives apply to surface waters: “- The natural receiving water temperature of inland surface waters shall not be altered unless it can be demonstrated to the satisfaction of the Regional Board that such alteration in temperature does not adversely affect beneficial uses. - The temperature of any cold or warm freshwater habitat shall not be increased by more than 5°F (2.8°C) above natural receiving water temperature.”
Per Effects of Temperature, Dissolved Oxygen/Total Dissolved Gas, Ammonia, and pH on Salmonids (Carter 2008, Moyle 1976, and USEPA 1977), the lethal temperature evaluation guideline for both the steelhead adult migration and holding and the steelhead juvenile growth and rearing life stages is 24°C.
Line of Evidence (LOE) for Decision ID 154220, Benthic Community Effects
Region 2
Arroyo Las Positas
LOE ID:
306899
Pollutant:
Benthic-Macroinvertebrate Bioassessments
LOE Subgroup:
Population/Community Degradation
Matrix:
Water
Fraction:
None
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
1
Data and Information Type:
Benthic macroinvertebrate surveys
Data Used to Assess Water Quality:
Water Board staff assessed data for 204ALP110 to determine beneficial use support and the results are as follows: 1 of 1 samples exceeded the threshold. CSCI scores were from 0.42352 to 0.42352.
All waters shall be maintained free of toxic substances in concentrations that are lethal to or that produce significant alterations in population or community ecology or receiving water biota. In addition, the health and life history characteristics of aquatic organisms in waters affected by controllable water quality factors shall not differ significantly from those for the same waters in areas unaffected by controllable water quality factors.
The California Stream Condition Index (CSCI) is a biological scoring tool that helps aquatic resource managers translate complex data about benthic macroinvertebrates found living in a stream into an overall measure of stream health. The CSCI score is calculated by comparing the expected condition with actual (observed) results (Rehn, A.C. et al., 2015). CSCI scores range from 0 (highly degraded) to greater than 1 (equivalent to reference). CSCI scoring of biological condition are as follows (per the scientific paper supporting the development of the CSCI scoring tool): greater than or equal to 0.92 = likely intact condition, 0.91 to 0.80 = possibly altered condition, 0.79 to 0.63 = likely altered condition, less than or equal to 0.62 = very likely altered condition. Sites with scores below 0.79 are considered to have exceeded the water quality objective for the aquatic life beneficial use.Â
ater temperature of inland surface waters shall not be altered unless it can be demonstrated to the satisfaction of the Regional Board that such alteration in temperature does not adversely affect beneficial uses. The temperature of any cold or warm freshwater habitat shall not be increased by more than 5 degrees F (2.8 degrees C) above natural receiving water temperature.
Scientific literature reviewed by the Washington Department of Ecology and U.S. EPA indicates that stream temperatures higher than 21C are associated with avoidance behavior and migration blockages in steelhead trout.
Line of Evidence (LOE) for Decision ID 141726, Temperature, water
Region 2
Arroyo Las Positas
LOE ID:
298989
Pollutant:
Temperature, water
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Not Recorded
Beneficial Use:
Fish Migration
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2018 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Temperature.
Temperature objectives for surface waters are specified in the San Francisco Bay Regional Water Quality Control Plan. The following temperature objectives apply to surface waters: The natural receiving water temperature of inland surface waters shall not be altered unless it can be demonstrated to the satisfaction of the Regional Board that such alteration in temperature does not adversely affect beneficial uses. The temperature of any cold or warm freshwater habitat shall not be increased by more than 5 degrees F (2.8 degrees C) above natural receiving water temperature.
Scientific literature reviewed by the Washington Department of Ecology and U.S. EPA indicates that stream temperatures higher than 21C are associated with avoidance behavior and migration blockages in steelhead trout.
Line of Evidence (LOE) for Decision ID 141726, Temperature, water
Region 2
Arroyo Las Positas
LOE ID:
298598
Pollutant:
Temperature, water
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Not Recorded
Beneficial Use:
Fish Migration
Number of Samples:
1
Number of Exceedances:
1
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2012 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 1 of 1 samples exceeded the water quality threshold for Temperature.
Temperature objectives for surface waters are specified in the San Francisco Bay Regional Water Quality Control Plan. The following temperature objectives apply to surface waters: The natural receiving water temperature of inland surface waters shall not be altered unless it can be demonstrated to the satisfaction of the Regional Board that such alteration in temperature does not adversely affect beneficial uses. The temperature of any cold or warm freshwater habitat shall not be increased by more than 5 degrees F (2.8 degrees C) above natural receiving water temperature.
Scientific literature reviewed by the Washington Department of Ecology and U.S. EPA indicates that stream temperatures higher than 21C are associated with avoidance behavior and migration blockages in steelhead trout.
Line of Evidence (LOE) for Decision ID 141726, Temperature, water
Region 2
Arroyo Las Positas
LOE ID:
298861
Pollutant:
Temperature, water
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Not Recorded
Beneficial Use:
Fish Migration
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2019 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Temperature.
Temperature objectives for surface waters are specified in the San Francisco Bay Regional Water Quality Control Plan. The following temperature objectives apply to surface waters: The natural receiving water temperature of inland surface waters shall not be altered unless it can be demonstrated to the satisfaction of the Regional Board that such alteration in temperature does not adversely affect beneficial uses. The temperature of any cold or warm freshwater habitat shall not be increased by more than 5 degrees F (2.8 degrees C) above natural receiving water temperature.
Scientific literature reviewed by the Washington Department of Ecology and U.S. EPA indicates that stream temperatures higher than 21C are associated with avoidance behavior and migration blockages in steelhead trout.
Line of Evidence (LOE) for Decision ID 141726, Temperature, water
Region 2
Arroyo Las Positas
LOE ID:
298863
Pollutant:
Temperature, water
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Not Recorded
Beneficial Use:
Fish Migration
Number of Samples:
1
Number of Exceedances:
1
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed SWAMP RWB2 Monitoring data for Arroyo Las Positas to determine beneficial use support and results are as follows: 1 of 1 samples exceeded the water quality threshold for Temperature.
Temperature objectives for surface waters are specified in the San Francisco Bay Regional Water Quality Control Plan. The following temperature objectives apply to surface waters: The natural receiving water temperature of inland surface waters shall not be altered unless it can be demonstrated to the satisfaction of the Regional Board that such alteration in temperature does not adversely affect beneficial uses. The temperature of any cold or warm freshwater habitat shall not be increased by more than 5 degrees F (2.8 degrees C) above natural receiving water temperature.
Scientific literature reviewed by the Washington Department of Ecology and U.S. EPA indicates that stream temperatures higher than 21C are associated with avoidance behavior and migration blockages in steelhead trout.
This pollutant is being considered for placement on the CWA section 303(d) List under section 3.2 of the Listing Policy. Under section 3.2 a single line of evidence is necessary to assess listing status.
30 lines of evidence are available in the administrative record to assess this pollutant. 6 of 9 dissolved samples and 12 of 18 total samples for both COLD and WARM Beneficial Uses exceed the evaluation guidelines.
Based on the readily available data and information, the weight of evidence indicates that there is sufficient justification in favor of placing this water segment-pollutant combination on the CWA section 303(d) List.
This conclusion is based on the staff findings that: 1. The data used satisfies the data quality requirements of section 6.1.4 of the Policy. 2. The data used satisfies the data quantity requirements of section 6.1.5 of the Policy. 3. 18 of 27 total samples exceed the evaluation criteria and this exceeds the allowable frequency listed in Table 3.2 of the Listing Policy. 4. Pursuant to section 3.11 of the Listing Policy, no additional data and information are available indicating that standards are not met.
Regional Board Decision Recommendation:
After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should be placed on the section 303(d) list because applicable water quality standards are exceeded and a pollutant contributes to or causes the problem.
State Board Review of Regional Board Conclusion and Recommendation:
State Board Decision Recommendation:
After review of this Regional Board decision, SWRCB staff recommend the decision be approved by the State Board.
Listing Extent:
Line of Evidence (LOE) for Decision ID 141699, Chloride
Region 2
Arroyo Las Positas
LOE ID:
281388
Pollutant:
Chloride
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
1
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2015 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 1 of 1 samples exceeded the water quality threshold for Chloride.
Line of Evidence (LOE) for Decision ID 141726, Temperature, water
Region 2
Arroyo Las Positas
LOE ID:
298534
Pollutant:
Temperature, water
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Not Recorded
Beneficial Use:
Fish Migration
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2019 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Temperature.
Temperature objectives for surface waters are specified in the San Francisco Bay Regional Water Quality Control Plan. The following temperature objectives apply to surface waters: The natural receiving water temperature of inland surface waters shall not be altered unless it can be demonstrated to the satisfaction of the Regional Board that such alteration in temperature does not adversely affect beneficial uses. The temperature of any cold or warm freshwater habitat shall not be increased by more than 5 degrees F (2.8 degrees C) above natural receiving water temperature.
Scientific literature reviewed by the Washington Department of Ecology and U.S. EPA indicates that stream temperatures higher than 21C are associated with avoidance behavior and migration blockages in steelhead trout.
The chloride criterion continuous concentration (expressed as a 4-day average) to protect aquatic life in freshwater is 230000 ug/L (230 mg/L)(USEPA National Recommended Water Quality Criteria, 2006).
Line of Evidence (LOE) for Decision ID 141699, Chloride
Region 2
Arroyo Las Positas
LOE ID:
281055
Pollutant:
Chloride
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
1
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2016 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 1 of 1 samples exceeded the water quality threshold for Chloride.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
The chloride criterion continuous concentration (expressed as a 4-day average) to protect aquatic life in freshwater is 230000 ug/L (230 mg/L)(USEPA National Recommended Water Quality Criteria, 2006).
Line of Evidence (LOE) for Decision ID 141726, Temperature, water
Region 2
Arroyo Las Positas
LOE ID:
299010
Pollutant:
Temperature, water
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Not Recorded
Beneficial Use:
Fish Migration
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2016 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Temperature.
Temperature objectives for surface waters are specified in the San Francisco Bay Regional Water Quality Control Plan. The following temperature objectives apply to surface waters: The natural receiving water temperature of inland surface waters shall not be altered unless it can be demonstrated to the satisfaction of the Regional Board that such alteration in temperature does not adversely affect beneficial uses. The temperature of any cold or warm freshwater habitat shall not be increased by more than 5 degrees F (2.8 degrees C) above natural receiving water temperature.
Scientific literature reviewed by the Washington Department of Ecology and U.S. EPA indicates that stream temperatures higher than 21C are associated with avoidance behavior and migration blockages in steelhead trout.
Line of Evidence (LOE) for Decision ID 141699, Chloride
Region 2
Arroyo Las Positas
LOE ID:
281506
Pollutant:
Chloride
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
4
Number of Exceedances:
2
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2019 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 2 of 4 samples exceeded the water quality threshold for Chloride.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
The chloride criterion continuous concentration (expressed as a 4-day average) to protect aquatic life in freshwater is 230000 ug/L (230 mg/L)(USEPA National Recommended Water Quality Criteria, 2006).
Line of Evidence (LOE) for Decision ID 141699, Chloride
Region 2
Arroyo Las Positas
LOE ID:
280881
Pollutant:
Chloride
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2020 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Chloride.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
The chloride criterion continuous concentration (expressed as a 4-day average) to protect aquatic life in freshwater is 230000 ug/L (230 mg/L)(USEPA National Recommended Water Quality Criteria, 2006).
Line of Evidence (LOE) for Decision ID 141699, Chloride
Region 2
Arroyo Las Positas
LOE ID:
281511
Pollutant:
Chloride
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
1
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2015 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 1 of 1 samples exceeded the water quality threshold for Chloride.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
The chloride criterion continuous concentration (expressed as a 4-day average) to protect aquatic life in freshwater is 230000 ug/L (230 mg/L)(USEPA National Recommended Water Quality Criteria, 2006).
The samples were collected at 1 monitoring site: 204R01945 (Altamont Creek approx 75 m north of Bluebell Dr.).
Temporal Representation:
DECISION ID
141720
Region 2
Arroyo Las Positas
Pollutant:
pH
Final Listing Decision:
List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:
New Decision
Revision Status
Revised
Sources:
A Source Unknown
TMDL Priority:
Low
Impairment from Pollutant or Pollution:
Pollutant
Regional Board Conclusion:
This pollutant is being considered for placement on the CWA section 303(d) List under section 3.2 of the Listing Policy. Under section 3.2 a single line of evidence is necessary to assess listing status.
One line of evidence are available in the administrative record to assess this pollutant. Ten of the fifty-one samples exceed the Basin Plan objective.
Based on the readily available data and information, the weight of evidence indicates that there is sufficient justification in favor of placing this water segment-pollutant combination on the CWA section 303(d) List.
This conclusion is based on the staff findings that: 1. The data used satisfies the data quality requirements of section 6.1.4 of the Policy. 2. The data used satisfies the data quantity requirements of section 6.1.5 of the Policy. 3. Ten of fifty-one samples exceed the Basin Plan objective and this exceeds the allowable frequency listed in Table 3.2 of the Listing Policy. 4. Pursuant to section 3.11 of the Listing Policy, no additional data and information are available indicating that standards are not met.
Regional Board Decision Recommendation:
After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should be placed on the section 303(d) list because applicable water quality standards are exceeded and a pollutant contributes to or causes the problem.
State Board Review of Regional Board Conclusion and Recommendation:
State Board Decision Recommendation:
After review of this Regional Board decision, SWRCB staff recommend the decision be approved by the State Board.
Listing Extent:
Line of Evidence (LOE) for Decision ID 141720, pH
Region 2
Arroyo Las Positas
LOE ID:
286949
Pollutant:
pH
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
None
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
1
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2015 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 1 of 1 samples exceeded the water quality threshold for pH.
Water Quality Control Plan, San Francisco Bay Basin, Chapter III Water Quality Objectives, Section 3.3.9 pH states: The pH shall not be depressed below 6.5 nor raised above 8.5.op" width="67%">The samples were collected between the dates of 2015-05-11 and 2015-05-11
Environmental Conditions:
QAPP Information:
EOA, Inc.. 2014. Creek Status Monitoring Program Quality Assurance Project Plan.
Line of Evidence (LOE) for Decision ID 141699, Chloride
Region 2
Arroyo Las Positas
LOE ID:
281204
Pollutant:
Chloride
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
4
Number of Exceedances:
3
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2019 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 3 of 4 samples exceeded the water quality threshold for Chloride.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
The chloride criterion continuous concentration (expressed as a 4-day average) to protect aquatic life in freshwater is 230000 ug/L (230 mg/L)(USEPA National Recommended Water Quality Criteria, 2006).
Water Board staff assessed SWAMP RWB2 Monitoring data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for pH.
Water Quality Control Plan, San Francisco Bay Basin, Chapter III Water Quality Objectives, Section 3.3.9 pH states: The pH shall not be depressed below 6.5 nor raised above 8.5. This encompasses the pH range usually found in waters within the basin. Controllable water quality factors shall not cause changes greater than 0.5 units in normal ambient pH levels.
Water Board staff assessed SWAMP RWB2 Monitoring data for Arroyo Las Positas to determine beneficial use support and results are as follows: 2 of 4 samples exceeded the water quality threshold for Chloride.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
The chloride criterion continuous concentration (expressed as a 4-day average) to protect aquatic life in freshwater is 230000 ug/L (230 mg/L)(USEPA National Recommended Water Quality Criteria, 2006).
Line of Evidence (LOE) for Decision ID 141699, Chloride
Region 2
Arroyo Las Positas
LOE ID:
281198
Pollutant:
Chloride
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2020 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Chloride.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
The chloride criterion continuous concentration (ex>
LOE ID:
286744
Pollutant:
pH
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
None
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2016 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for pH.
Water Quality Control Plan, San Francisco Bay Basin, Chapter III Water Quality Objectives, Section 3.3.9 pH states: The pH shall not be depressed below 6.5 nor raised above 8.5. This encompasses the pH range usually found in waters within the basin. Controllable water quality factors shall not cause changes greater than 0.5 units in normal ambient pH levels.
Water Board staff assessed SWAMP RWB2 Monitoring data for Arroyo Las Positas to determine beneficial use support and results are as follows: 7 of 15 samples exceeded the water quality threshold for pH.
Water Quality Control Plan, San Francisco Bay Basin, Chapter III Water Quality Objectives, Section 3.3.9 pH states: The pH shall not be depressed below 6.5 nor raised above 8.5. This encompasses the pH range usually found in waters within the basin. Controllable water quality factors shall not cause changes greater than 0.5 units in normal ambient pH levels.
Line of Evidence (LOE) for Decision ID 141699, Chloride
Region 2
Arroyo Las Positas
LOE ID:
281230
Pollutant:
Chloride
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
4
Number of Exceedances:
2
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2019 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 2 of 4 samples exceeded the water quality threshold for Chloride.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
The chloride criterion continuous concentration (expressed as a 4-day average) to protect aquatic life in freshwater is 230000 ug/L (230 mg/L)(USEPA National Recommended Water Quality Criteria, 2006).
Water Board staff assessed BASMAA RMC Monitoring in WY2012 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for pH.
Water Quality Control Plan, San Francisco Bay Basin, Chapter III Water Quality Objectives, Section 3.3.9 pH states: The pH shall not be depressed below 6.5 nor raised above 8.5. This encompasses the pH range usually found in waters within the basin. Controllable water quality factors shall not cause changes greater than 0.5 units in normal ambient pH levels.
WIDTH: 100%; text-align: left; PADDING-TOP: 3px; font-smooth: always">Arroyo Las Positas
LOE ID:
281864
Pollutant:
Chloride
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
1
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2014 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 1 of 1 samples exceeded the water quality threshold for Chloride.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
The chloride criterion continuous concentration (expressed as a 4-day average) to protect aquatic life in freshwater is 230000 ug/L (230 mg/L)(USEPA National Recommended Water Quality Criteria, 2006).
Line of Evidence (LOE) for Decision ID 141699, Chloride
Region 2
Arroyo Las Positas
LOE ID:
281015
Pollutant:
Chloride
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2019 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Chloride.
Water Board staff assessed BASMAA RMC Monitoring in WY2014 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for pH.
Water Quality Control Plan, San Francisco Bay Basin, Chapter III Water Quality Objectives, Section 3.3.9 pH states: The pH shall not be depressed below 6.5 nor raised above 8.5. This encompasses the pH range usually found in waters within the basin. Controllable water quality factors shall not cause changes greater than 0.5 units in normal ambient pH levels.
Water Board staff assessed BASMAA RMC Monitoring in WY2019 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for pH.
Water Quality Control Plan, San Francisco Bay Basin, Chapter III Water Quality Objectives, Section 3.3.9 pH states: The pH shall not be depressed below 6.5 nor raised above 8.5. This encompasses the pH range usually found in waters within the basin. Controllable water quality factors shall not cause changes greater than 0.5 units in normal ambient pH levels.
Spat"67%">Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
The chloride criterion continuous concentration (expressed as a 4-day average) to protect aquatic life in freshwater is 230000 ug/L (230 mg/L)(USEPA National Recommended Water Quality Criteria, 2006).
Line of Evidence (LOE) for Decision ID 141699, Chloride
Region 2
Arroyo Las Positas
LOE ID:
281494
Pollutant:
Chloride
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
1
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2012 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 1 of 1 samples exceeded the water quality threshold for Chloride.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
The chloride criterion continuous concentration (expressed as a 4-day average) to protect aquatic life in freshwater is 230000 ug/L (230 mg/L)(USEPA National Recommended Water Quality Criteria, 2006).
Line of Evidence (LOE) for Decision ID 141699, Chloride
Region 2
Arroyo Las Positas
LOE ID:
281205
Pollutant:
Chloride
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2019 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Chloride.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
The chloride criterion continuous concentration (expressed as a 4-day average) to protect aquatic life in freshwater is 230000 ug/L (230 mg/L)(USEPA National Recommended Water Quality Criteria, 2006).
Water Board staff assessed BASMAA RMC Monitoring in WY2014 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for pH.
Water Quality Control Plan, San Francisco Bay Basin, Chapter III Water Quality Objectives, Section 3.3.9 pH states: The pH shall not be depressed below 6.5 nor raised above 8.5. This encompasses the pH range usually found in waters within the basin. Controllable water quality factors shall not cause changes greater than 0.5 units in normal ambient pH levels.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
The chloride criterion continuous concentration (expressed as a 4-day average) to protect aquatic life in freshwater is 230000 ug/L (230 mg/L)(USEPA National Recommended Water Quality Criteria, 2006).
Line of Evidence (LOE) for Decision ID 141699, Chloride
Region 2
Arroyo Las Positas
LOE ID:
281866
Pollutant:
Chloride
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
1
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2017 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 1 of 1 samples exceeded the water quality threshold for Chloride.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
The chloride criterion continuous concentration (expressed as a 4-day average) to protect aquatic life in freshwater is 230000 ug/L (230 mg/L)(USEPA National Recommended Water Quality Criteria, 2006).
The samples were collected at 1 monitoring site: 204R03481 (Altamont Creek upstream of Springtown).
Temporal Reptop" width="67%">1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2017 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for pH.
Water Quality Control Plan, San Francisco Bay Basin, Chapter III Water Quality Objectives, Section 3.3.9 pH states: The pH shall not be depressed below 6.5 nor raised above 8.5. This encompasses the pH range usually found in waters within the basin. Controllable water quality factors shall not cause changes greater than 0.5 units in normal ambient pH levels.
Water Board staff assessed SWAMP RWB2 Monitoring data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 10 samples exceeded the water quality threshold for pH.
Water Quality Control Plan, San Francisco Bay Basin, Chapter III Water Quality Objectives, Section 3.3.9 pH states: The pH shall not be depressed below 6.5 nor raised above 8.5. This encompasses the pH range usually found in waters within the basin. Controllable water quality factors shall not cause changes greater than 0.5 units in normal ambient pH levels.
Line of Evidence (LOE) for Decision ID 141699, Chloride
Region 2
Arroyo Las Positas
LOE ID:
281493
Pollutant:
Chloride
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Dissolved
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
4
Number of Exceedances:
2
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed SWAMP RWB2 Monitoring data for Arroyo Las Positas to determine beneficial use support and results are as follows: 2 of 4 samples exceeded the water quality threshold for Chloride.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
The chloride criterion continuous concentration (expressed as a 4-day average) to protect aquatic life in freshwater is 230000 ug/L (230 mg/L)(USEPA National Recommended Water Quality Criteria, 2006).
Water Board staff assessed BASMAA RMC Monitoring in WY2018 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for pH.
Water Quality Control Plan, San Francisco Bay Basin, Chapter III Water Quality Objectives, Section 3.3.9 pH states: The pH shall not be depressed below 6.5 nor raised above 8.5. This encompasses the pH range usually found in waters within the basin. Controllable water quality factors shall not cause changes greater than 0.5 units in normal ambient pH levels.
Water Board staff assessed SWAMP RWB2 Monitoring data for Arroyo Las Positas to determine beneficial use support and results are as follows: 2 of 2 samples exceeded the water quality threshold for Chloride.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
The chloride criterion continuous concentration (expressed as a 4-day average) to protect aquatic life in freshwater is 230000 ug/L (230 mg/L)(USEPA National Recommended Water Quality Criteria, 2006).
Line of Evidence (LOE) for Decision ID 141699, Chloride
Region 2
Arroyo Las Positas
LOE ID:
281390
Pollutant:
Chloride
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
1
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2017 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 1 of 1 samples exceeded the water quality threshold for Chloride.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
Water Board staff assessed BASMAA RMC Monitoring in WY2019 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for pH.
Water Quality Control Plan, San Francisco Bay Basin, Chapter III Water Quality Objectives, Section 3.3.9 pH states: The pH shall not be depressed below 6.5 nor raised above 8.5. This encompasses the pH range usually found in waters within the basin. Controllable water quality factors shall not cause changes greater than 0.5 units in normal ambient pH levels.
Water Board staff assessed BASMAA RMC Monitoring in WY2019 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for pH.
Water Quality Control Plan, San Francisco Bay Basin, Chapter III Water Quality Objectives, Section 3.3.9 pH states: The pH shall not be depressed below 6.5 nor raised above 8.5. This encompasses the pH range usually found in waters within the basin. Controllable water quality factors shall not cause changes greater than 0.5 units in normal ambient pH levels.
The samples were collected at 1 monitoring site: 204R03481 (Altamont Creek upstream of Springtown).
Temporal Representation:
The samples were collected between the dates of 2019-05-15 and 2019-05-15
Environmental Conditions:
QAPP Information:
EOA, Inc.. 2014. Creek Status Monitoring Program Quality Assurance Project Plan.
QAPP Information ds.ca.gov/water_issues/programs/tmdl/records/region_2/2010/ref3754.pdf" >Water Quality Control Plan (Basin Plan) San Francisco Bay Basin (Region 2)
Evaluation Guideline:
The chloride criterion continuous concentration (expressed as a 4-day average) to protect aquatic life in freshwater is 230000 ug/L (230 mg/L)(USEPA National Recommended Water Quality Criteria, 2006).
Line of Evidence (LOE) for Decision ID 141699, Chloride
Region 2
Arroyo Las Positas
LOE ID:
281229
Pollutant:
Chloride
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
1
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2017 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 1 of 1 samples exceeded the water quality threshold for Chloride.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
The chloride criterion continuous concentration (expressed as a 4-day average) to protect aquatic life in freshwater is 230000 ug/L (230 mg/L)(USEPA National Recommended Water Quality Criteria, 2006).
Line of Evidence (LOE) for Decision ID 141699, Chloride
Region 2
Arroyo Las Positas
LOE ID:
280898
Pollutant:
Chloride
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
1
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2014 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 1 of 1 samples exceeded the water quality threshold for Chloride.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
The chloride criterion continuous concentration (expressed as a 4-day average) to protect aquatic life in freshwater is 230000 ug/L (230 mg/L)(USEPA National Recommended Water Quality Criteria, 2006).
Line of Evidence (LOE) for Decision ID 141699, Chloride
Region 2
Arroyo Las Positas
LOE ID:
281888
Pollutant:
Chloride
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
1
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2016 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 1 of 1 samples exceeded the water quality threshold for Chloride.
Water Board staff assessed BASMAA RMC Monitoring in WY2017 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for pH.
Water Quality Control Plan, San Francisco Bay Basin, Chapter III Water Quality Objectives, Section 3.3.9 pH states: The pH shall not be depressed below 6.5 nor raised above 8.5. This encompasses the pH range usually found in waters within the basin. Controllable water quality factors shall not cause changes greater than 0.5 units in normal ambient pH levels.
Water Board staff assessed BASMAA RMC Monitoring in WY2012 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for pH.
Water Quality Control Plan, San Francisco Bay Basin, Chapter III Water Quality Objectives, Section 3.3.9 pH states: The pH shall not be depressed below 6.5 nor raised above 8.5. This encompasses the pH range usually found in waters within the basin. Controllable water quality factors shall not cause changes greater than 0.5 units in normal ambient pH levels.
Water Board staff assessed BASMAA RMC Monitoring in WY2020 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for pH.
Water Quality Control Plan, San Francisco Bay Basin, Chapter III Water Quality Objectives, Section 3.3.9 pH states: The pH shall not be depressed below 6.5 nor raised above 8.5. This encompasses the pH range usually found in waters within the basin. Controllable water quality factors shall not cause changes greater than 0.5 units in normal ambient pH levels.
Water Board staff assessed SWAMP RWB2 Monitoring data for Arroyo Las Positas to determine beneficial use support and results are as follows: 2 of 12 samples exceeded the water quality threshold for pH.
Water Quality Control Plan, San Francisco Bay Basin, Chapter III Water Quality Objectives, Section 3.3.9 pH states: The pH shall not be depressed below 6.5 nor raised above 8.5. This encompasses the pH range usually found in waters within the basin. Controllable water quality factors shall not cause changes greater than 0.5 units in normal ambient pH levels.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
The chloride criterion continuous concentration (expressed as a 4-day average) to protect aquatic life in freshwater is 230000 ug/L (230 mg/L)(USEPA National Recommended Water Quality Criteria, 2006).
Line of Evidence (LOE) for Decision ID 141699, Chloride
Region 2
Arroyo Las Positas
LOE ID:
280723
Pollutant:
Chloride
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
1
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2012 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 1 of 1 samples exceeded the water quality threshold for Chloride.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
The chloride criterion continuous concentration (expressed as a 4-day average) to protect aquatic life in freshwater is 230000 ug/L (230 mg/L)(USEPA National Recommended Water Quality Criteria, 2006).
Line of Evidence (LOE) for Decision ID 141699, Chloride
Region 2
Arroyo Las Positas
LOE ID:
281383
Pollutant:
Chloride
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Dissolved
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
3
Number of Exceedances:
2
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed SWAMP RWB2 Monitoring data for Arroyo Las Positas to determine beneficial use support and results are as follows: 2 of 3 samples exceeded the water quality threshold for Chloride.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
The chloride criterion continuous concentration (expressed as a 4-day average) to protect aquatic life in freshwater is 230000 ug/L (230 mg/L)(USEPA National Recommended Water Quality Criteria, 2006).
Line of Evidence (LOE) for Decision ID 141699, Chloride
Region 2
Arroyo Las Positas
LOE ID:
280970
Pollutant:
Chloride
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Dissolved
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
3
Number of Exceedances:
2
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed SWAMP RWB2 Monitoring data for Arroyo Las Positas to determine beneficial use support and results are as follows: 2 of 3 samples exceeded the water quality threshold for Chloride.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
The chloride criterion continuous concentration (expressed as a 4-day average) to protect aquatic life in freshwater is 230000 ug/L (230 mg/L)(USEPA National Recommended Water Quality Criteria, 2006).
Line of Evidence (LOE) for Decision ID 141699, Chloride
Region 2
Arroyo Las Positas
LOE ID:
281403
Pollutant:
Chloride
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
1
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2017 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 1 of 1 samples exceeded the water quality threshold for Chloride.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
The chloride criterion continuous concentration (expressed as a 4-day average) to protect aquatic life in freshwater is 230000 ug/L (230 mg/L)(USEPA National Recommended Water Quality Criteria, 2006).
Line of Evidence (LOE) for Decision ID 141699, Chloride
Region 2
Arroyo Las Positas
LOE ID:
281330
Pollutant:
Chloride
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2014 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Chloride.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
The chloride criterion continuous concentration (expressed as a 4-day average) to protect aquatic life in freshwater is 230000 ug/L (230 mg/L)(USEPA National Recommended Water Quality Criteria, 2006).
Line of Evidence (LOE) for Decision ID 141699, Chloride
Region 2
Arroyo Las Positas
LOE ID:
281331
Pollutant:
Chloride
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
1
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2014 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 1 of 1 samples exceeded the water quality threshold for Chloride.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
The chloride criterion continuous concentration (expressed as a 4-day average) to protect aquatic life in freshwater is 230000 ug/L (230 mg/L)(USEPA National Recommended Water Quality Criteria, 2006).
Line of Evidence (LOE) for Decision ID 141699, Chloride
Region 2
Arroyo Las Positas
LOE ID:
281183
Pollutant:
Chloride
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2014 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Chloride.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
The chloride criterion continuous concentration (expressed as a 4-day average) to protect aquatic life in freshwater is 230000 ug/L (230 mg/L)(USEPA National Recommended Water Quality Criteria, 2006).
Line of Evidence (LOE) for Decision ID 141699, Chloride
Region 2
Arroyo Las Positas
LOE ID:
280985
Pollutant:
Chloride
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Dissolved
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
2
Number of Exceedances:
2
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed SWAMP RWB2 Monitoring data for Arroyo Las Positas to determine beneficial use support and results are as follows: 2 of 2 samples exceeded the water quality threshold for Chloride.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
The chloride criterion continuous concentration (expressed as a 4-day average) to protect aquatic life in freshwater is 230000 ug/L (230 mg/L)(USEPA National Recommended Water Quality Criteria, 2006).
Line of Evidence (LOE) for Decision ID 141699, Chloride
Region 2
Arroyo Las Positas
LOE ID:
281027
Pollutant:
Chloride
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Total
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
1
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2014 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 1 of 1 samples exceeded the water quality threshold for Chloride.
Water Quality Control Plan for the San Francisco Bay Basin: Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
The chloride criterion continuous concentration (expressed as a 4-day average) to protect aquatic life in freshwater is 230000 ug/L (230 mg/L)(USEPA National Recommended Water Quality Criteria, 2006).
Do Not List on 303(d) list (TMDL required list)(2018)
Revision Status
Revised
Sources:
A Source Unknown
TMDL Priority:
Low
Impairment from Pollutant or Pollution:
Pollutant
Regional Board Conclusion:
This pollutant is being considered for placement on the CWA section 303(d) List under section 3.2 of the Listing Policy. Under section 3.2 a single line of evidence is necessary to assess listing status.
35 lines of evidence are available in the administrative record to assess this pollutant. Nine of fifty-three grab samples exceed the 24C lethal threshold protecting the COLD Beneficial Use. Seven of thirteen samples exceed the 17C threshold for the 7-day average of daily mean temperature, and twenty-two of fifty-one samples exceed the threshold for the protection of the fish migration Beneficial Use.
Based on the readily available data and information, the weight of evidence indicates that there is sufficient justification in favor of placing this water segment-pollutant combination on the CWA section 303(d) List.
This conclusion is based on the staff findings that: 1. The data used satisfies the data quality requirements of section 6.1.4 of the Policy. 2. The data used satisfies the data quantity requirements of section 6.1.5 of the Policy. 3. Nine of fifty-three grab samples exceed the 24C lethal threshold protecting the COLD Beneficial Use. Seven of thirteen samples exceed the 17C threshold for the 7-day average of daily mean temperature, and twenty-two of fifty-one samples exceed the threshold for the protection of the fish migration Beneficial Use and this exceeds the allowable frequency listed in Table 3.2 of the Listing Policy. 4. Pursuant to section 3.11 of the Listing Policy, no additional data and information are available indicating that standards are not met.
Regional Board Decision Recommendation:
After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should be placed on the section 303(d) list because applicable water quality standards are exceeded and a pollutant contributes to or causes the problem.
State Board Review of Regional Board Conclusion and Recommendation:
State Board Decision Recommendation:
After review of this Regional Board decision, SWRCB staff recommend the decision be approved by the State Board.
Listing Extent:
Line of Evidence (LOE) for Decision ID 141726, Temperature, water
Region 2
Arroyo Las Positas
LOE ID:
30213
Pollutant:
Temperature, water
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
None
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
13
Number of Exceedances:
7
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water quality assessment was conducted at the Arroyo Las Positas watershed as part of SWAMP study in 2002. Continuous field monitoring at 15 minute increments of temperature, dissolved oxygen, pH and specific conductance was conducted to determine temporal variability in basic water quality at three locations. Continuous monitoring sondes were deployed 13 times at 3 or 5 monitoring locations during winter wet, spring wet and summer dry seasons. The measured temperatures ranged from 3.89oC to 32.1oC and varied with season and location. The 7-day mean temperature threshold for steelhead of 17 °C was exceeded during 7 out of 13 deployments. The 7-day moving average was consistently high (above 20oC) at all 5 monitoring locations during summer sampling season only (June-July 2002).
Temperature objectives for enclosed bays and estuaries are specified in the "Water Quality Control Plan for Control of Temperature in the Coastal and Interstate Waters and Enclosed Bays of California" including any revisions to the plan. In addition, the following temperature objectives apply to surface waters: The natural receiving water temperature of intrastate waters shall not be altered unless it can be demonstrated to the satisfaction of the Regional Board that such an alteration does not adversely affect beneficial uses. The temperature of any cold or warm freshwater habitat shall not be increased by more than 5°F (2.8°C) above natural receiving water temperature.
Sullivan et al. (2000) reviewed a wide range of studies incorporating information from laboratory-based research, field observations, and risk assessment approaches and developed criteria for assessing temperature risk to aquatic life. The 7-day mean temperature (maximum value of a 7-day moving average of the daily mean temperature) of 14.8°C was established as the upper threshold criterion for coho salmon and 17.0°C for steelhead trout. The risk assessment approach used by Sullivan et al. (2000)suggest that temperatures exceeding the above thresholds will cause a 10% reduction in average growth compared to optimal conditions.
Temperature was measured at three or five sites in the Arroyo Las Positas watershead. Four monitoring sites are located in the mainstream of Arroyo Las Positas Creek while one site (ALP105) is located in Altamont Creek that is believed to be intermittent in the upstream section.
Temporal Representation:
In 2002 the SWAMP Program performed continuous monitoring of temperature at 15 minute intervals for periods of 1-2 weeks in each of three different seasons: winter (3 sites), spring (5 sites), and summer dry season (5 sites).
Environmental Conditions:
QAPP Information:
All samples were collected and analyzed using procedures comparable with the SWAMP Quality Assurance Management Plan (SWRCB 2002).
Line of Evidence (LOE) for Decision ID 141726, Temperature, water
Region 2
Arroyo Las Positas
LOE ID:
288883
Pollutant:
Temperature, water
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Not Recorded
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2019 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Temperature.
Temperature objectives for surface waters are specified in the San Francisco Bay Regional Water Quality Control Plan. The following temperature objectives apply to surface waters: “- The natural receiving water temperature of inland surface waters shall not be altered unless it can be demonstrated to the satisfaction of the Regional Board that such alteration in temperature does not adversely affect beneficial uses. - The temperature of any cold or warm freshwater habitat shall not be increased by more than 5°F (2.8°C) above natural receiving water temperature.”
Per Effects of Temperature, Dissolved Oxygen/Total Dissolved Gas, Ammonia, and pH on Salmonids (Carter 2008, Moyle 1976, and USEPA 1977), the lethal temperature evaluation guideline for both the steelhead adult migration and holding and the steelhead juvenile growth and rearing life stages is 24°C.
Line of Evidence (LOE) for Decision ID 141726, Temperature, water
Region 2
Arroyo Las Positas
LOE ID:
288910
Pollutant:
Temperature, water
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Not Recorded
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2017 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Temperature.
Temperature objectives for surface waters are specified in the San Francisco Bay Regional Water Quality Control Plan. The following temperature objectives apply to surface waters: “- The natural receiving water temperature of inland surface waters shall not be altered unless it can be demonstrated to the satisfaction of the Regional Board that such alteration in temperature does not adversely affect beneficial uses. - The temperature of any cold or warm freshwater habitat shall not be increased by more than 5°F (2.8°C) above natural receiving water temperature.”
Per Effects of Temperature, Dissolved Oxygen/Total Dissolved Gas, Ammonia, and pH on Salmonids (Carter 2008, Moyle 1976, and USEPA 1977), the lethal temperature evaluation guideline for both the steelhead adult migration and holding and the steelhead juvenile growth and rearing life stages is 24°C.
Line of Evidence (LOE) for Decision ID 141726, Temperature, water
Region 2
Arroyo Las Positas
LOE ID:
288723
Pollutant:
Temperature, water
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Not Recorded
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2020 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Temperature.
Temperature objectives for surface waters are specified in the San Francisco Bay Regional Water Quality Control Plan. The following temperature objectives apply to surface waters: “- The natural receiving water temperature of inland surface waters shall not be altered unless it can be demonstrated to the satisfaction of the Regional Board that such alteration in temperature does not adversely affect beneficial uses. - The temperature of any cold or warm freshwater habitat shall not be increased by more than 5°F (2.8°C) above natural receiving water temperature.”
Per Effects of Temperature, Dissolved Oxygen/Total Dissolved Gas, Ammonia, and pH on Salmonids (Carter 2008, Moyle 1976, and USEPA 1977), the lethal temperature evaluation guideline for both the steelhead adult migration and holding and the steelhead juvenile growth and rearing life stages is 24°C.
Line of Evidence (LOE) for Decision ID 141726, Temperature, water
Region 2
Arroyo Las Positas
LOE ID:
288502
Pollutant:
Temperature, water
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Not Recorded
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
16
Number of Exceedances:
8
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed SWAMP RWB2 Monitoring data for Arroyo Las Positas to determine beneficial use support and results are as follows: 8 of 16 samples exceeded the water quality threshold for Temperature.
Temperature objectives for surface waters are specified in the San Francisco Bay Regional Water Quality Control Plan. The following temperature objectives apply to surface waters: “- The natural receiving water temperature of inland surface waters shall not be altered unless it can be demonstrated to the satisfaction of the Regional Board that such alteration in temperature does not adversely affect beneficial uses. - The temperature of any cold or warm freshwater habitat shall not be increased by more than 5°F (2.8°C) above natural receiving water temperature.”
Per Effects of Temperature, Dissolved Oxygen/Total Dissolved Gas, Ammonia, and pH on Salmonids (Carter 2008, Moyle 1976, and USEPA 1977), the lethal temperature evaluation guideline for both the steelhead adult migration and holding and the steelhead juvenile growth and rearing life stages is 24°C.
Line of Evidence (LOE) for Decision ID 141726, Temperature, water
Region 2
Arroyo Las Positas
LOE ID:
288636
Pollutant:
Temperature, water
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Not Recorded
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
11
Number of Exceedances:
1
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed SWAMP RWB2 Monitoring data for Arroyo Las Positas to determine beneficial use support and results are as follows: 1 of 11 samples exceeded the water quality threshold for Temperature.
Temperature objectives for surface waters are specified in the San Francisco Bay Regional Water Quality Control Plan. The following temperature objectives apply to surface waters: “- The natural receiving water temperature of inland surface waters shall not be altered unless it can be demonstrated to the satisfaction of the Regional Board that such alteration in temperature does not adversely affect beneficial uses. - The temperature of any cold or warm freshwater habitat shall not be increased by more than 5°F (2.8°C) above natural receiving water temperature.”
Per Effects of Temperature, Dissolved Oxygen/Total Dissolved Gas, Ammonia, and pH on Salmonids (Carter 2008, Moyle 1976, and USEPA 1977), the lethal temperature evaluation guideline for both the steelhead adult migration and holding and the steelhead juvenile growth and rearing life stages is 24°C.
Line of Evidence (LOE) for Decision ID 141726, Temperature, water
Region 2
Arroyo Las Positas
LOE ID:
288597
Pollutant:
Temperature, water
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Not Recorded
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2014 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Temperature.
Temperature objectives for surface waters are specified in the San Francisco Bay Regional Water Quality Control Plan. The following temperature objectives apply to surface waters: “- The natural receiving water temperature of inland surface waters shall not be altered unless it can be demonstrated to the satisfaction of the Regional Board that such alteration in temperature does not adversely affect beneficial uses. - The temperature of any cold or warm freshwater habitat shall not be increased by more than 5°F (2.8°C) above natural receiving water temperature.”
Per Effects of Temperature, Dissolved Oxygen/Total Dissolved Gas, Ammonia, and pH on Salmonids (Carter 2008, Moyle 1976, and USEPA 1977), the lethal temperature evaluation guideline for both the steelhead adult migration and holding and the steelhead juvenile growth and rearing life stages is 24°C.
Line of Evidence (LOE) for Decision ID 141726, Temperature, water
Region 2
Arroyo Las Positas
LOE ID:
288187
Pollutant:
Temperature, water
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Not Recorded
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2015 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Temperature.
Temperature objectives for surface waters are specified in the San Francisco Bay Regional Water Quality Control Plan. The following temperature objectives apply to surface waters: “- The natural receiving water temperature of inland surface waters shall not be altered unless it can be demonstrated to the satisfaction of the Regional Board that such alteration in temperature does not adversely affect beneficial uses. - The temperature of any cold or warm freshwater habitat shall not be increased by more than 5°F (2.8°C) above natural receiving water temperature.”
Per Effects of Temperature, Dissolved Oxygen/Total Dissolved Gas, Ammonia, and pH on Salmonids (Carter 2008, Moyle 1976, and USEPA 1977), the lethal temperature evaluation guideline for both the steelhead adult migration and holding and the steelhead juvenile growth and rearing life stages is 24°C.
Line of Evidence (LOE) for Decision ID 141726, Temperature, water
Region 2
Arroyo Las Positas
LOE ID:
298757
Pollutant:
Temperature, water
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Not Recorded
Beneficial Use:
Fish Migration
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2014 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Temperature.
Temperature objectives for surface waters are specified in the San Francisco Bay Regional Water Quality Control Plan. The following temperature objectives apply to surface waters: The natural receiving water temperature of inland surface waters shall not be altered unless it can be demonstrated to the satisfaction of the Regional Board that such alteration in temperature does not adversely affect beneficial uses. The temperature of any cold or warm freshwater habitat shall not be increased by more than 5 degrees F (2.8 degrees C) above natural receiving water temperature.
Scientific literature reviewed by the Washington Department of Ecology and U.S. EPA indicates that stream temperatures higher than 21C are associated with avoidance behavior and migration blockages in steelhead trout.
Line of Evidence (LOE) for Decision ID 141726, Temperature, water
Region 2
Arroyo Las Positas
LOE ID:
298762
Pollutant:
Temperature, water
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Not Recorded
Beneficial Use:
Fish Migration
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2012 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Temperature.
Temperature objectives for surface waters are specified in the San Francisco Bay Regional Water Quality Control Plan. The following temperature objectives apply to surface waters: The natural receiving water temperature of inland surface waters shall not be altered unless it can be demonstrated to the satisfaction of the Regional Board that such alteration in temperature does not adversely affect beneficial uses. The temperature of any cold or warm freshwater habitat shall not be increased by more than 5 degrees F (2.8 degrees C) above natural receiving water temperature.
Scientific literature reviewed by the Washington Department of Ecology and U.S. EPA indicates that stream temperatures higher than 21C are associated with avoidance behavior and migration blockages in steelhead trout.
Line of Evidence (LOE) for Decision ID 141726, Temperature, water
Region 2
Arroyo Las Positas
LOE ID:
298580
Pollutant:
Temperature, water
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Not Recorded
Beneficial Use:
Fish Migration
Number of Samples:
10
Number of Exceedances:
3
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed SWAMP RWB2 Monitoring data for Arroyo Las Positas to determine beneficial use support and results are as follows: 3 of 10 samples exceeded the water quality threshold for Temperature.
Temperature objectives for surface waters are specified in the San Francisco Bay Regional Water Quality Control Plan. The following temperature objectives apply to surface waters: The natural receiving water temperature of inland surface waters shall not be altered unless it can be demonstrated to the satisfaction of the Regional Board that such alteration in temperature does not adversely affect beneficial uses. The temperature of any cold or warm freshwater habitat shall not be increased by more than 5 degrees F (2.8 degrees C) above natural receiving water temperature.
Scientific literature reviewed by the Washington Department of Ecology and U.S. EPA indicates that stream temperatures higher than 21C are associated with avoidance behavior and migration blockages in steelhead trout.
Line of Evidence (LOE) for Decision ID 141726, Temperature, water
Region 2
Arroyo Las Positas
LOE ID:
288402
Pollutant:
Temperature, water
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Not Recorded
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2017 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Temperature.
Temperature objectives for surface waters are specified in the San Francisco Bay Regional Water Quality Control Plan. The following temperature objectives apply to surface waters: “- The natural receiving water temperature of inland surface waters shall not be altered unless it can be demonstrated to the satisfaction of the Regional Board that such alteration in temperature does not adversely affect beneficial uses. - The temperature of any cold or warm freshwater habitat shall not be increased by more than 5°F (2.8°C) above natural receiving water temperature.”
Per Effects of Temperature, Dissolved Oxygen/Total Dissolved Gas, Ammonia, and pH on Salmonids (Carter 2008, Moyle 1976, and USEPA 1977), the lethal temperature evaluation guideline for both the steelhead adult migration and holding and the steelhead juvenile growth and rearing life stages is 24°C.
Line of Evidence (LOE) for Decision ID 141726, Temperature, water
Region 2
Arroyo Las Positas
LOE ID:
288221
Pollutant:
Temperature, water
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Not Recorded
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2016 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Temperature.
Temperature objectives for surface waters are specified in the San Francisco Bay Regional Water Quality Control Plan. The following temperature objectives apply to surface waters: “- The natural receiving water temperature of inland surface waters shall not be altered unless it can be demonstrated to the satisfaction of the Regional Board that such alteration in temperature does not adversely affect beneficial uses. - The temperature of any cold or warm freshwater habitat shall not be increased by more than 5°F (2.8°C) above natural receiving water temperature.”
Per Effects of Temperature, Dissolved Oxygen/Total Dissolved Gas, Ammonia, and pH on Salmonids (Carter 2008, Moyle 1976, and USEPA 1977), the lethal temperature evaluation guideline for both the steelhead adult migration and holding and the steelhead juvenile growth and rearing life stages is 24°C.
Line of Evidence (LOE) for Decision ID 141726, Temperature, water
Region 2
Arroyo Las Positas
LOE ID:
288596
Pollutant:
Temperature, water
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Not Recorded
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2014 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Temperature.
Temperature objectives for surface waters are specified in the San Francisco Bay Regional Water Quality Control Plan. The following temperature objectives apply to surface waters: “- The natural receiving water temperature of inland surface waters shall not be altered unless it can be demonstrated to the satisfaction of the Regional Board that such alteration in temperature does not adversely affect beneficial uses. - The temperature of any cold or warm freshwater habitat shall not be increased by more than 5°F (2.8°C) above natural receiving water temperature.”
Per Effects of Temperature, Dissolved Oxygen/Total Dissolved Gas, Ammonia, and pH on Salmonids (Carter 2008, Moyle 1976, and USEPA 1977), the lethal temperature evaluation guideline for both the steelhead adult migration and holding and the steelhead juvenile growth and rearing life stages is 24°C.
Line of Evidence (LOE) for Decision ID 141726, Temperature, water
Region 2
Arroyo Las Positas
LOE ID:
288889
Pollutant:
Temperature, water
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Not Recorded
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed SWAMP RWB2 Monitoring data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Temperature.
Temperature objectives for surface waters are specified in the San Francisco Bay Regional Water Quality Control Plan. The following temperature objectives apply to surface waters: “- The natural receiving water temperature of inland surface waters shall not be altered unless it can be demonstrated to the satisfaction of the Regional Board that such alteration in temperature does not adversely affect beneficial uses. - The temperature of any cold or warm freshwater habitat shall not be increased by more than 5°F (2.8°C) above natural receiving water temperature.”
Per Effects of Temperature, Dissolved Oxygen/Total Dissolved Gas, Ammonia, and pH on Salmonids (Carter 2008, Moyle 1976, and USEPA 1977), the lethal temperature evaluation guideline for both the steelhead adult migration and holding and the steelhead juvenile growth and rearing life stages is 24°C.
Line of Evidence (LOE) for Decision ID 141726, Temperature, water
Region 2
Arroyo Las Positas
LOE ID:
288555
Pollutant:
Temperature, water
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Not Recorded
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2012 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Temperature.
Temperature objectives for surface waters are specified in the San Francisco Bay Regional Water Quality Control Plan. The following temperature objectives apply to surface waters: “- The natural receiving water temperature of inland surface waters shall not be altered unless it can be demonstrated to the satisfaction of the Regional Board that such alteration in temperature does not adversely affect beneficial uses. - The temperature of any cold or warm freshwater habitat shall not be increased by more than 5°F (2.8°C) above natural receiving water temperature.”
Per Effects of Temperature, Dissolved Oxygen/Total Dissolved Gas, Ammonia, and pH on Salmonids (Carter 2008, Moyle 1976, and USEPA 1977), the lethal temperature evaluation guideline for both the steelhead adult migration and holding and the steelhead juvenile growth and rearing life stages is 24°C.
Line of Evidence (LOE) for Decision ID 141726, Temperature, water
Region 2
Arroyo Las Positas
LOE ID:
288581
Pollutant:
Temperature, water
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Not Recorded
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2012 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Temperature.
Temperature objectives for surface waters are specified in the San Francisco Bay Regional Water Quality Control Plan. The following temperature objectives apply to surface waters: “- The natural receiving water temperature of inland surface waters shall not be altered unless it can be demonstrated to the satisfaction of the Regional Board that such alteration in temperature does not adversely affect beneficial uses. - The temperature of any cold or warm freshwater habitat shall not be increased by more than 5°F (2.8°C) above natural receiving water temperature.”
Per Effects of Temperature, Dissolved Oxygen/Total Dissolved Gas, Ammonia, and pH on Salmonids (Carter 2008, Moyle 1976, and USEPA 1977), the lethal temperature evaluation guideline for both the steelhead adult migration and holding and the steelhead juvenile growth and rearing life stages is 24°C.
Line of Evidence (LOE) for Decision ID 141726, Temperature, water
Region 2
Arroyo Las Positas
LOE ID:
288850
Pollutant:
Temperature, water
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Not Recorded
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2019 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Temperature.
Temperature objectives for surface waters are specified in the San Francisco Bay Regional Water Quality Control Plan. The following temperature objectives apply to surface waters: “- The natural receiving water temperature of inland surface waters shall not be altered unless it can be demonstrated to the satisfaction of the Regional Board that such alteration in temperature does not adversely affect beneficial uses. - The temperature of any cold or warm freshwater habitat shall not be increased by more than 5°F (2.8°C) above natural receiving water temperature.”
Per Effects of Temperature, Dissolved Oxygen/Total Dissolved Gas, Ammonia, and pH on Salmonids (Carter 2008, Moyle 1976, and USEPA 1977), the lethal temperature evaluation guideline for both the steelhead adult migration and holding and the steelhead juvenile growth and rearing life stages is 24°C.
Line of Evidence (LOE) for Decision ID 141726, Temperature, water
Region 2
Arroyo Las Positas
LOE ID:
288800
Pollutant:
Temperature, water
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Not Recorded
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
12
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed SWAMP RWB2 Monitoring data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 12 samples exceeded the water quality threshold for Temperature.
Temperature objectives for surface waters are specified in the San Francisco Bay Regional Water Quality Control Plan. The following temperature objectives apply to surface waters: “- The natural receiving water temperature of inland surface waters shall not be altered unless it can be demonstrated to the satisfaction of the Regional Board that such alteration in temperature does not adversely affect beneficial uses. - The temperature of any cold or warm freshwater habitat shall not be increased by more than 5°F (2.8°C) above natural receiving water temperature.”
Per Effects of Temperature, Dissolved Oxygen/Total Dissolved Gas, Ammonia, and pH on Salmonids (Carter 2008, Moyle 1976, and USEPA 1977), the lethal temperature evaluation guideline for both the steelhead adult migration and holding and the steelhead juvenile growth and rearing life stages is 24°C.
Line of Evidence (LOE) for Decision ID 141726, Temperature, water
Region 2
Arroyo Las Positas
LOE ID:
288882
Pollutant:
Temperature, water
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Not Recorded
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2019 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Temperature.
Temperature objectives for surface waters are specified in the San Francisco Bay Regional Water Quality Control Plan. The following temperature objectives apply to surface waters: “- The natural receiving water temperature of inland surface waters shall not be altered unless it can be demonstrated to the satisfaction of the Regional Board that such alteration in temperature does not adversely affect beneficial uses. - The temperature of any cold or warm freshwater habitat shall not be increased by more than 5°F (2.8°C) above natural receiving water temperature.”
Per Effects of Temperature, Dissolved Oxygen/Total Dissolved Gas, Ammonia, and pH on Salmonids (Carter 2008, Moyle 1976, and USEPA 1977), the lethal temperature evaluation guideline for both the steelhead adult migration and holding and the steelhead juvenile growth and rearing life stages is 24°C.
Line of Evidence (LOE) for Decision ID 141726, Temperature, water
Region 2
Arroyo Las Positas
LOE ID:
288588
Pollutant:
Temperature, water
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Not Recorded
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2018 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Temperature.
Temperature objectives for surface waters are specified in the San Francisco Bay Regional Water Quality Control Plan. The following temperature objectives apply to surface waters: “- The natural receiving water temperature of inland surface waters shall not be altered unless it can be demonstrated to the satisfaction of the Regional Board that such alteration in temperature does not adversely affect beneficial uses. - The temperature of any cold or warm freshwater habitat shall not be increased by more than 5°F (2.8°C) above natural receiving water temperature.”
Per Effects of Temperature, Dissolved Oxygen/Total Dissolved Gas, Ammonia, and pH on Salmonids (Carter 2008, Moyle 1976, and USEPA 1977), the lethal temperature evaluation guideline for both the steelhead adult migration and holding and the steelhead juvenile growth and rearing life stages is 24°C.
Line of Evidence (LOE) for Decision ID 141726, Temperature, water
Region 2
Arroyo Las Positas
LOE ID:
298816
Pollutant:
Temperature, water
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Not Recorded
Beneficial Use:
Fish Migration
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2015 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Temperature.
Temperature objectives for surface waters are specified in the San Francisco Bay Regional Water Quality Control Plan. The following temperature objectives apply to surface waters: The natural receiving water temperature of inland surface waters shall not be altered unless it can be demonstrated to the satisfaction of the Regional Board that such alteration in temperature does not adversely affect beneficial uses. The temperature of any cold or warm freshwater habitat shall not be increased by more than 5 degrees F (2.8 degrees C) above natural receiving water temperature.
Scientific literature reviewed by the Washington Department of Ecology and U.S. EPA indicates that stream temperatures higher than 21C are associated with avoidance behavior and migration blockages in steelhead trout.
Line of Evidence (LOE) for Decision ID 141726, Temperature, water
Region 2
Arroyo Las Positas
LOE ID:
298953
Pollutant:
Temperature, water
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Not Recorded
Beneficial Use:
Fish Migration
Number of Samples:
12
Number of Exceedances:
8
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed SWAMP RWB2 Monitoring data for Arroyo Las Positas to determine beneficial use support and results are as follows: 8 of 12 samples exceeded the water quality threshold for Temperature.
Temperature objectives for surface waters are specified in the San Francisco Bay Regional Water Quality Control Plan. The following temperature objectives apply to surface waters: The natural receiving water temperature of inland surface waters shall not be altered unless it can be demonstrated to the satisfaction of the Regional Board that such alteration in temperature does not adversely affect beneficial uses. The temperature of any cold or warm freshwater habitat shall not be increased by more than 5 degrees F (2.8 degrees C) above natural receiving water temperature.
Scientific literature reviewed by the Washington Department of Ecology and U.S. EPA indicates that stream temperatures higher than 21C are associated with avoidance behavior and migration blockages in steelhead trout.
Line of Evidence (LOE) for Decision ID 141726, Temperature, water
Region 2
Arroyo Las Positas
LOE ID:
298517
Pollutant:
Temperature, water
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Not Recorded
Beneficial Use:
Fish Migration
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2014 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Temperature.
Temperature objectives for surface waters are specified in the San Francisco Bay Regional Water Quality Control Plan. The following temperature objectives apply to surface waters: The natural receiving water temperature of inland surface waters shall not be altered unless it can be demonstrated to the satisfaction of the Regional Board that such alteration in temperature does not adversely affect beneficial uses. The temperature of any cold or warm freshwater habitat shall not be increased by more than 5 degrees F (2.8 degrees C) above natural receiving water temperature.
Scientific literature reviewed by the Washington Department of Ecology and U.S. EPA indicates that stream temperatures higher than 21C are associated with avoidance behavior and migration blockages in steelhead trout.
Line of Evidence (LOE) for Decision ID 141726, Temperature, water
Region 2
Arroyo Las Positas
LOE ID:
298648
Pollutant:
Temperature, water
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Not Recorded
Beneficial Use:
Fish Migration
Number of Samples:
15
Number of Exceedances:
9
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed SWAMP RWB2 Monitoring data for Arroyo Las Positas to determine beneficial use support and results are as follows: 9 of 15 samples exceeded the water quality threshold for Temperature.
Temperature objectives for surface waters are specified in the San Francisco Bay Regional Water Quality Control Plan. The following temperature objectives apply to surface waters: The natural receiving water temperature of inland surface waters shall not be altered unless it can be demonstrated to the satisfaction of the Regional Board that such alteration in temperature does not adversely affect beneficial uses. The temperature of any cold or warm freshwater habitat shall not be increased by more than 5 degrees F (2.8 degrees C) above natural receiving water temperature.
Scientific literature reviewed by the Washington Department of Ecology and U.S. EPA indicates that stream temperatures higher than 21C are associated with avoidance behavior and migration blockages in steelhead trout.
Line of Evidence (LOE) for Decision ID 141726, Temperature, water
Region 2
Arroyo Las Positas
LOE ID:
298930
Pollutant:
Temperature, water
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Not Recorded
Beneficial Use:
Fish Migration
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2019 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Temperature.
Temperature objectives for surface waters are specified in the San Francisco Bay Regional Water Quality Control Plan. The following temperature objectives apply to surface waters: The natural receiving water temperature of inland surface waters shall not be altered unless it can be demonstrated to the satisfaction of the Regional Board that such alteration in temperature does not adversely affect beneficial uses. The temperature of any cold or warm freshwater habitat shall not be increased by more than 5 degrees F (2.8 degrees C) above natural receiving water temperature.
Scientific literature reviewed by the Washington Department of Ecology and U.S. EPA indicates that stream temperatures higher than 21C are associated with avoidance behavior and migration blockages in steelhead trout.
Line of Evidence (LOE) for Decision ID 141726, Temperature, water
Region 2
Arroyo Las Positas
LOE ID:
298991
Pollutant:
Temperature, water
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Not Recorded
Beneficial Use:
Fish Migration
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2017 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Temperature.
Temperature objectives for surface waters are specified in the San Francisco Bay Regional Water Quality Control Plan. The following temperature objectives apply to surface waters: The natural receiving water temperature of inland surface waters shall not be altered unless it can be demonstrated to the satisfaction of the Regional Board that such alteration in temperature does not adversely affect beneficial uses. The temperature of any cold or warm freshwater habitat shall not be increased by more than 5 degrees F (2.8 degrees C) above natural receiving water temperature.
Scientific literature reviewed by the Washington Department of Ecology and U.S. EPA indicates that stream temperatures higher than 21C are associated with avoidance behavior and migration blockages in steelhead trout.
Line of Evidence (LOE) for Decision ID 141726, Temperature, water
Region 2
Arroyo Las Positas
LOE ID:
298990
Pollutant:
Temperature, water
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Not Recorded
Beneficial Use:
Fish Migration
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2017 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Temperature.
Temperature objectives for surface waters are specified in the San Francisco Bay Regional Water Quality Control Plan. The following temperature objectives apply to surface waters: The natural receiving water temperature of inland surface waters shall not be altered unless it can be demonstrated to the satisfaction of the Regional Board that such alteration in temperature does not adversely affect beneficial uses. The temperature of any cold or warm freshwater habitat shall not be increased by more than 5 degrees F (2.8 degrees C) above natural receiving water temperature.
Scientific literature reviewed by the Washington Department of Ecology and U.S. EPA indicates that stream temperatures higher than 21C are associated with avoidance behavior and migration blockages in steelhead trout.
Line of Evidence (LOE) for Decision ID 141726, Temperature, water
Region 2
Arroyo Las Positas
LOE ID:
298753
Pollutant:
Temperature, water
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Not Recorded
Beneficial Use:
Fish Migration
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2020 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Temperature.
Temperature objectives for surface waters are specified in the San Francisco Bay Regional Water Quality Control Plan. The following temperature objectives apply to surface waters: The natural receiving water temperature of inland surface waters shall not be altered unless it can be demonstrated to the satisfaction of the Regional Board that such alteration in temperature does not adversely affect beneficial uses. The temperature of any cold or warm freshwater habitat shall not be increased by more than 5 degrees F (2.8 degrees C) above natural receiving water temperature.
Scientific literature reviewed by the Washington Department of Ecology and U.S. EPA indicates that stream temperatures higher than 21C are associated with avoidance behavior and migration blockages in steelhead trout.
Line of Evidence (LOE) for Decision ID 141726, Temperature, water
Region 2
Arroyo Las Positas
LOE ID:
298989
Pollutant:
Temperature, water
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Not Recorded
Beneficial Use:
Fish Migration
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2018 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Temperature.
Temperature objectives for surface waters are specified in the San Francisco Bay Regional Water Quality Control Plan. The following temperature objectives apply to surface waters: The natural receiving water temperature of inland surface waters shall not be altered unless it can be demonstrated to the satisfaction of the Regional Board that such alteration in temperature does not adversely affect beneficial uses. The temperature of any cold or warm freshwater habitat shall not be increased by more than 5 degrees F (2.8 degrees C) above natural receiving water temperature.
Scientific literature reviewed by the Washington Department of Ecology and U.S. EPA indicates that stream temperatures higher than 21C are associated with avoidance behavior and migration blockages in steelhead trout.
Line of Evidence (LOE) for Decision ID 141726, Temperature, water
Region 2
Arroyo Las Positas
LOE ID:
298598
Pollutant:
Temperature, water
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Not Recorded
Beneficial Use:
Fish Migration
Number of Samples:
1
Number of Exceedances:
1
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2012 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 1 of 1 samples exceeded the water quality threshold for Temperature.
Temperature objectives for surface waters are specified in the San Francisco Bay Regional Water Quality Control Plan. The following temperature objectives apply to surface waters: The natural receiving water temperature of inland surface waters shall not be altered unless it can be demonstrated to the satisfaction of the Regional Board that such alteration in temperature does not adversely affect beneficial uses. The temperature of any cold or warm freshwater habitat shall not be increased by more than 5 degrees F (2.8 degrees C) above natural receiving water temperature.
Scientific literature reviewed by the Washington Department of Ecology and U.S. EPA indicates that stream temperatures higher than 21C are associated with avoidance behavior and migration blockages in steelhead trout.
Line of Evidence (LOE) for Decision ID 141726, Temperature, water
Region 2
Arroyo Las Positas
LOE ID:
298861
Pollutant:
Temperature, water
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Not Recorded
Beneficial Use:
Fish Migration
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2019 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Temperature.
Temperature objectives for surface waters are specified in the San Francisco Bay Regional Water Quality Control Plan. The following temperature objectives apply to surface waters: The natural receiving water temperature of inland surface waters shall not be altered unless it can be demonstrated to the satisfaction of the Regional Board that such alteration in temperature does not adversely affect beneficial uses. The temperature of any cold or warm freshwater habitat shall not be increased by more than 5 degrees F (2.8 degrees C) above natural receiving water temperature.
Scientific literature reviewed by the Washington Department of Ecology and U.S. EPA indicates that stream temperatures higher than 21C are associated with avoidance behavior and migration blockages in steelhead trout.
Line of Evidence (LOE) for Decision ID 141726, Temperature, water
Region 2
Arroyo Las Positas
LOE ID:
298863
Pollutant:
Temperature, water
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Not Recorded
Beneficial Use:
Fish Migration
Number of Samples:
1
Number of Exceedances:
1
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed SWAMP RWB2 Monitoring data for Arroyo Las Positas to determine beneficial use support and results are as follows: 1 of 1 samples exceeded the water quality threshold for Temperature.
Temperature objectives for surface waters are specified in the San Francisco Bay Regional Water Quality Control Plan. The following temperature objectives apply to surface waters: The natural receiving water temperature of inland surface waters shall not be altered unless it can be demonstrated to the satisfaction of the Regional Board that such alteration in temperature does not adversely affect beneficial uses. The temperature of any cold or warm freshwater habitat shall not be increased by more than 5 degrees F (2.8 degrees C) above natural receiving water temperature.
Scientific literature reviewed by the Washington Department of Ecology and U.S. EPA indicates that stream temperatures higher than 21C are associated with avoidance behavior and migration blockages in steelhead trout.
Line of Evidence (LOE) for Decision ID 141726, Temperature, water
Region 2
Arroyo Las Positas
LOE ID:
298534
Pollutant:
Temperature, water
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Not Recorded
Beneficial Use:
Fish Migration
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2019 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Temperature.
Temperature objectives for surface waters are specified in the San Francisco Bay Regional Water Quality Control Plan. The following temperature objectives apply to surface waters: The natural receiving water temperature of inland surface waters shall not be altered unless it can be demonstrated to the satisfaction of the Regional Board that such alteration in temperature does not adversely affect beneficial uses. The temperature of any cold or warm freshwater habitat shall not be increased by more than 5 degrees F (2.8 degrees C) above natural receiving water temperature.
Scientific literature reviewed by the Washington Department of Ecology and U.S. EPA indicates that stream temperatures higher than 21C are associated with avoidance behavior and migration blockages in steelhead trout.
Line of Evidence (LOE) for Decision ID 141726, Temperature, water
Region 2
Arroyo Las Positas
LOE ID:
299010
Pollutant:
Temperature, water
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
Not Recorded
Beneficial Use:
Fish Migration
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2016 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Temperature.
Temperature objectives for surface waters are specified in the San Francisco Bay Regional Water Quality Control Plan. The following temperature objectives apply to surface waters: The natural receiving water temperature of inland surface waters shall not be altered unless it can be demonstrated to the satisfaction of the Regional Board that such alteration in temperature does not adversely affect beneficial uses. The temperature of any cold or warm freshwater habitat shall not be increased by more than 5 degrees F (2.8 degrees C) above natural receiving water temperature.
Scientific literature reviewed by the Washington Department of Ecology and U.S. EPA indicates that stream temperatures higher than 21C are associated with avoidance behavior and migration blockages in steelhead trout.
This pollutant is being considered for placement on the CWA section 303(d) List under section 3.2 of the Listing Policy. Under section 3.2 a single line of evidence is necessary to assess listing status.
One line of evidence are available in the administrative record to assess this pollutant. Ten of the fifty-one samples exceed the Basin Plan objective.
Based on the readily available data and information, the weight of evidence indicates that there is sufficient justification in favor of placing this water segment-pollutant combination on the CWA section 303(d) List.
This conclusion is based on the staff findings that: 1. The data used satisfies the data quality requirements of section 6.1.4 of the Policy. 2. The data used satisfies the data quantity requirements of section 6.1.5 of the Policy. 3. Ten of fifty-one samples exceed the Basin Plan objective and this exceeds the allowable frequency listed in Table 3.2 of the Listing Policy. 4. Pursuant to section 3.11 of the Listing Policy, no additional data and information are available indicating that standards are not met.
Regional Board Decision Recommendation:
After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should be placed on the section 303(d) list because applicable water quality standards are exceeded and a pollutant contributes to or causes the problem.
State Board Review of Regional Board Conclusion and Recommendation:
State Board Decision Recommendation:
After review of this Regional Board decision, SWRCB staff recommend the decision be approved by the State Board.
Listing Extent:
Line of Evidence (LOE) for Decision ID 141720, pH
Region 2
Arroyo Las Positas
LOE ID:
286949
Pollutant:
pH
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
None
Beneficial Use:
Cold Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
1
Data and Information Type:
PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality:
Water Board staff assessed BASMAA RMC Monitoring in WY2015 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 1 of 1 samples exceeded the water quality threshold for pH.
Water Quality Control Plan, San Francisco Bay Basin, Chapter III Water Quality Objectives, Section 3.3.9 pH states: The pH shall not be depressed below 6.5 nor raised above 8.5. This encompasses the pH range usually found in waters within the basin. Controllable water quality factors shall not cause changes greater than 0.5 units in normal ambient pH levels.
Water Board staff assessed SWAMP RWB2 Monitoring data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for pH.
Water Quality Control Plan, San Francisco Bay Basin, Chapter III Water Quality Objectives, Section 3.3.9 pH states: The pH shall not be depressed below 6.5 nor raised above 8.5. This encompasses the pH range usually found in waters within the basin. Controllable water quality factors shall not cause changes greater than 0.5 units in normal ambient pH levels.
Water Board staff assessed BASMAA RMC Monitoring in WY2016 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for pH.
Water Quality Control Plan, San Francisco Bay Basin, Chapter III Water Quality Objectives, Section 3.3.9 pH states: The pH shall not be depressed below 6.5 nor raised above 8.5. This encompasses the pH range usually found in waters within the basin. Controllable water quality factors shall not cause changes greater than 0.5 units in normal ambient pH levels.
Water Board staff assessed SWAMP RWB2 Monitoring data for Arroyo Las Positas to determine beneficial use support and results are as follows: 7 of 15 samples exceeded the water quality threshold for pH.
Water Quality Control Plan, San Francisco Bay Basin, Chapter III Water Quality Objectives, Section 3.3.9 pH states: The pH shall not be depressed below 6.5 nor raised above 8.5. This encompasses the pH range usually found in waters within the basin. Controllable water quality factors shall not cause changes greater than 0.5 units in normal ambient pH levels.
Water Board staff assessed BASMAA RMC Monitoring in WY2012 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for pH.
Water Quality Control Plan, San Francisco Bay Basin, Chapter III Water Quality Objectives, Section 3.3.9 pH states: The pH shall not be depressed below 6.5 nor raised above 8.5. This encompasses the pH range usually found in waters within the basin. Controllable water quality factors shall not cause changes greater than 0.5 units in normal ambient pH levels.
Water Board staff assessed BASMAA RMC Monitoring in WY2014 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for pH.
Water Quality Control Plan, San Francisco Bay Basin, Chapter III Water Quality Objectives, Section 3.3.9 pH states: The pH shall not be depressed below 6.5 nor raised above 8.5. This encompasses the pH range usually found in waters within the basin. Controllable water quality factors shall not cause changes greater than 0.5 units in normal ambient pH levels.
Water Board staff assessed BASMAA RMC Monitoring in WY2019 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for pH.
Water Quality Control Plan, San Francisco Bay Basin, Chapter III Water Quality Objectives, Section 3.3.9 pH states: The pH shall not be depressed below 6.5 nor raised above 8.5. This encompasses the pH range usually found in waters within the basin. Controllable water quality factors shall not cause changes greater than 0.5 units in normal ambient pH levels.
Water Board staff assessed BASMAA RMC Monitoring in WY2014 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for pH.
Water Quality Control Plan, San Francisco Bay Basin, Chapter III Water Quality Objectives, Section 3.3.9 pH states: The pH shall not be depressed below 6.5 nor raised above 8.5. This encompasses the pH range usually found in waters within the basin. Controllable water quality factors shall not cause changes greater than 0.5 units in normal ambient pH levels.
Water Board staff assessed BASMAA RMC Monitoring in WY2017 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for pH.
Water Quality Control Plan, San Francisco Bay Basin, Chapter III Water Quality Objectives, Section 3.3.9 pH states: The pH shall not be depressed below 6.5 nor raised above 8.5. This encompasses the pH range usually found in waters within the basin. Controllable water quality factors shall not cause changes greater than 0.5 units in normal ambient pH levels.
Water Board staff assessed SWAMP RWB2 Monitoring data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 10 samples exceeded the water quality threshold for pH.
Water Quality Control Plan, San Francisco Bay Basin, Chapter III Water Quality Objectives, Section 3.3.9 pH states: The pH shall not be depressed below 6.5 nor raised above 8.5. This encompasses the pH range usually found in waters within the basin. Controllable water quality factors shall not cause changes greater than 0.5 units in normal ambient pH levels.
Water Board staff assessed BASMAA RMC Monitoring in WY2018 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for pH.
Water Quality Control Plan, San Francisco Bay Basin, Chapter III Water Quality Objectives, Section 3.3.9 pH states: The pH shall not be depressed below 6.5 nor raised above 8.5. This encompasses the pH range usually found in waters within the basin. Controllable water quality factors shall not cause changes greater than 0.5 units in normal ambient pH levels.
Water Board staff assessed BASMAA RMC Monitoring in WY2019 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for pH.
Water Quality Control Plan, San Francisco Bay Basin, Chapter III Water Quality Objectives, Section 3.3.9 pH states: The pH shall not be depressed below 6.5 nor raised above 8.5. This encompasses the pH range usually found in waters within the basin. Controllable water quality factors shall not cause changes greater than 0.5 units in normal ambient pH levels.
Water Board staff assessed BASMAA RMC Monitoring in WY2019 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for pH.
Water Quality Control Plan, San Francisco Bay Basin, Chapter III Water Quality Objectives, Section 3.3.9 pH states: The pH shall not be depressed below 6.5 nor raised above 8.5. This encompasses the pH range usually found in waters within the basin. Controllable water quality factors shall not cause changes greater than 0.5 units in normal ambient pH levels.
Water Board staff assessed BASMAA RMC Monitoring in WY2017 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for pH.
Water Quality Control Plan, San Francisco Bay Basin, Chapter III Water Quality Objectives, Section 3.3.9 pH states: The pH shall not be depressed below 6.5 nor raised above 8.5. This encompasses the pH range usually found in waters within the basin. Controllable water quality factors shall not cause changes greater than 0.5 units in normal ambient pH levels.
Water Board staff assessed BASMAA RMC Monitoring in WY2012 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for pH.
Water Quality Control Plan, San Francisco Bay Basin, Chapter III Water Quality Objectives, Section 3.3.9 pH states: The pH shall not be depressed below 6.5 nor raised above 8.5. This encompasses the pH range usually found in waters within the basin. Controllable water quality factors shall not cause changes greater than 0.5 units in normal ambient pH levels.
Water Board staff assessed BASMAA RMC Monitoring in WY2020 data for Arroyo Las Positas to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for pH.
Water Quality Control Plan, San Francisco Bay Basin, Chapter III Water Quality Objectives, Section 3.3.9 pH states: The pH shall not be depressed below 6.5 nor raised above 8.5. This encompasses the pH range usually found in waters within the basin. Controllable water quality factors shall not cause changes greater than 0.5 units in normal ambient pH levels.
Water Board staff assessed SWAMP RWB2 Monitoring data for Arroyo Las Positas to determine beneficial use support and results are as follows: 2 of 12 samples exceeded the water quality threshold for pH.
Water Quality Control Plan, San Francisco Bay Basin, Chapter III Water Quality Objectives, Section 3.3.9 pH states: The pH shall not be depressed below 6.5 nor raised above 8.5. This encompasses the pH range usually found in waters within the basin. Controllable water quality factors shall not cause changes greater than 0.5 units in normal ambient pH levels.
Do Not List on 303(d) list (TMDL required list)(2016)
Revision Status
Original
Impairment from Pollutant or Pollution:
Pollutant
Regional Board Conclusion:
This pollutant is being considered for placement on the CWA section 303(d) List under section 3.1 of the Listing Policy. Under section 3.1 a single line of evidence is necessary to assess listing status.
Two lines of evidence are available in the administrative record to assess this pollutant. Four of six samples exceed the guideline.
A 2007 SWAMP study identified 1500 microSiemens per centimeter as an electrical conductivity (EC) limit for Selenastrum capricornutum in standard toxicity tests and recommended that sample waters exceeding this EC level be tested against high EC controls of similar salinity to differentiate actual toxicity from reductions in growth due to elevated EC. This protocol was not in effect for the data collected in 2001 and 2002. Specific conductance exceeded 1500 microSiemens per centimeter in three of the five samples that showed significant S. capricornutum growth reductions in laboratory tests (Spring sample at 204ALP010 and dry season and Spring samples at 204APL100). It is highly likely that the algae growth results for up to three samples would be reported as not significantly toxic under the updated testing guidelines. Thus, the SWAMP data do not present a reasonable basis for this proposed listing and are deemed insufficient information.
Based on the readily available data and information, the weight of evidence indicates that there is not sufficient justification in favor of placing this water segment-pollutant combination on the CWA section 303(d) List.
This conclusion is based on the staff findings that:
1. The data used do not satisfy the data quality requirements of section 6.1.4 of the Policy (see above).
2. The data used satisfies the data quantity requirements of section 6.1.5 of the Policy.
3. Four of six samples exceed the guideline and this exceeds the allowable frequency listed in Table 3.1 of the Listing Policy.
4. Pursuant to section 3.11 of the Listing Policy, no additional data and information are available indicating that standards are not met.
Regional Board Decision Recommendation:
After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list. The readily available data and information is insufficient to determine, with the power and confidence of the Listing Policy, the applicable beneficial use support rating.
State Board Review of Regional Board Conclusion and Recommendation:
State Board Decision Recommendation:
After review of this Regional Board decision, SWRCB staff recommend the decision be approved by the State Board.
Listing Extent:
Line of Evidence (LOE) for Decision ID 88265, Toxicity
Region 2
Arroyo Las Positas
LOE ID:
28993
Pollutant:
Toxicity
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
None
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
6
Number of Exceedances:
4
Data and Information Type:
TOXICITY TESTING
Data Used to Assess Water Quality:
Six samples were collected in 2001 to evaluate water toxicity at two monitoring locations in Arroyo Las Positas Creek. The toxicity tests included survival and reproduction of Ceriodaphnia, survival and growth of fathead minnow, and growth of Selenastrum. Selenastrum growth was significantly lower than the control in four out of six samples (all spring samples and one of the dry season samples). Growth ranged between 55.6 and 79.5 percent of the control for these samples.
All waters shall be maintained free of toxic substances that are lethal to or that produce other detrimental responses in aquatic organisms.
There shall be no chronic toxicity in ambient waters. Chronic toxicity is a detrimental biological effect on growth rate, reproduction, fertilization success, larval development, population abundance, community composition, or any other relevant measure of the health of an organism, population, or community.
Water toxicity was evaluated according to the SWAMP methodology. The U.S.EPA whole effluent toxicity protocol (U.S.EPA 1994) was used to test the effect of water samples on three freshwater test organisms. Statistical evaluation (alpha = 0.05) and a default threshold of 80% of the control value were used to establish whether water exhibited significant toxicity adversely impacting aquatic organisms.
Data were collected at three sampling locations, ALP010, (El Charro), ALP100 (Altamont Creek), and ALP110 (Arroyo Las Positas) representing the mainstem of Arroyo Las Positas Creek.
Temporal Representation:
SWAMP samples were collected during winter wet season, spring season, and dry season of 2001.
Environmental Conditions:
QAPP Information:
All samples were collected and analyzed using procedures comparable with the SWAMP Quality Assurance Management Plan (SWRCB, 2002).
Line of Evidence (LOE) for Decision ID 88265, Toxicity
Region 2
Arroyo Las Positas
LOE ID:
28831
Pollutant:
Sediment Toxicity
LOE Subgroup:
Pollutant-Sediment
Matrix:
Sediment
Fraction:
None
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
Toxicity testing of sediments
Data Used to Assess Water Quality:
Data used to evaluate sediment toxicity comprise one sediment sample collected by the SWAMP in 2001. No toxicity or adverse affects were exhibited for Hyallela azteca.
All waters shall be maintained free of toxic substances that are lethal to or that produce other detrimental responses in aquatic organisms.
There shall be no chronic toxicity in ambient waters. Chronic toxicity is a detrimental biological effect on growth rate, reproduction, fertilization success, larval development, population abundance, community composition, or any other relevant measure of the health of an organism, population, or community.
Sediment toxicity was evaluated according to the SWAMP methodology. Sample toxicity was determined by comparing mean organism response in samples and in negative controls. Statistical evaluation (alpha = 0.05) and a default threshold of 80% of the control value were used to establish whether the sediment exhibited significant toxicity adversely impacting aquatic organisms.
Do Not List on 303(d) list (TMDL required list)(2016)
Revision Status
Original
Impairment from Pollutant or Pollution:
Pollutant
Regional Board Conclusion:
This pollutant is being considered for placement on the CWA section 303(d) List under section 3.1 of the Listing Policy. Under section 3.1 a single line of evidence is necessary to assess listing status.
Two lines of evidence are available in the administrative record to assess this pollutant. Four of six samples exceed the guideline.
A 2007 SWAMP study identified 1500 microSiemens per centimeter as an electrical conductivity (EC) limit for Selenastrum capricornutum in standard toxicity tests and recommended that sample waters exceeding this EC level be tested against high EC controls of similar salinity to differentiate actual toxicity from reductions in growth due to elevated EC. This protocol was not in effect for the data collected in 2001 and 2002. Specific conductance exceeded 1500 microSiemens per centimeter in three of the five samples that showed significant S. capricornutum growth reductions in laboratory tests (Spring sample at 204ALP010 and dry season and Spring samples at 204APL100). It is highly likely that the algae growth results for up to three samples would be reported as not significantly toxic under the updated testing guidelines. Thus, the SWAMP data do not present a reasonable basis for this proposed listing and are deemed insufficient information.
Based on the readily available data and information, the weight of evidence indicates that there is not sufficient justification in favor of placing this water segment-pollutant combination on the CWA section 303(d) List.
This conclusion is based on the staff findings that:
1. The data used do not satisfy the data quality requirements of section 6.1.4 of the Policy (see above).
2. The data used satisfies the data quantity requirements of section 6.1.5 of the Policy.
3. Four of six samples exceed the guideline and this exceeds the allowable frequency listed in Table 3.1 of the Listing Policy.
4. Pursuant to section 3.11 of the Listing Policy, no additional data and information are available indicating that standards are not met.
Regional Board Decision Recommendation:
After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list. The readily available data and information is insufficient to determine, with the power and confidence of the Listing Policy, the applicable beneficial use support rating.
State Board Review of Regional Board Conclusion and Recommendation:
State Board Decision Recommendation:
After review of this Regional Board decision, SWRCB staff recommend the decision be approved by the State Board.
Listing Extent:
Line of Evidence (LOE) for Decision ID 88265, Toxicity
Region 2
Arroyo Las Positas
LOE ID:
28993
Pollutant:
Toxicity
LOE Subgroup:
Pollutant-Water
Matrix:
Water
Fraction:
None
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
6
Number of Exceedances:
4
Data and Information Type:
TOXICITY TESTING
Data Used to Assess Water Quality:
Six samples were collected in 2001 to evaluate water toxicity at two monitoring locations in Arroyo Las Positas Creek. The toxicity tests included survival and reproduction of Ceriodaphnia, survival and growth of fathead minnow, and growth of Selenastrum. Selenastrum growth was significantly lower than the control in four out of six samples (all spring samples and one of the dry season samples). Growth ranged between 55.6 and 79.5 percent of the control for these samples.
All waters shall be maintained free of toxic substances that are lethal to or that produce other detrimental responses in aquatic organisms.
There shall be no chronic toxicity in ambient waters. Chronic toxicity is a detrimental biological effect on growth rate, reproduction, fertilization success, larval development, population abundance, community composition, or any other relevant measure of the health of an organism, population, or community.
Water toxicity was evaluated according to the SWAMP methodology. The U.S.EPA whole effluent toxicity protocol (U.S.EPA 1994) was used to test the effect of water samples on three freshwater test organisms. Statistical evaluation (alpha = 0.05) and a default threshold of 80% of the control value were used to establish whether water exhibited significant toxicity adversely impacting aquatic organisms.
Data were collected at three sampling locations, ALP010, (El Charro), ALP100 (Altamont Creek), and ALP110 (Arroyo Las Positas) representing the mainstem of Arroyo Las Positas Creek.
Temporal Representation:
SWAMP samples were collected during winter wet season, spring season, and dry season of 2001.
Environmental Conditions:
QAPP Information:
All samples were collected and analyzed using procedures comparable with the SWAMP Quality Assurance Management Plan (SWRCB, 2002).
Line of Evidence (LOE) for Decision ID 88265, Toxicity
Region 2
Arroyo Las Positas
LOE ID:
28831
Pollutant:
Sediment Toxicity
LOE Subgroup:
Pollutant-Sediment
Matrix:
Sediment
Fraction:
None
Beneficial Use:
Warm Freshwater Habitat
Number of Samples:
1
Number of Exceedances:
0
Data and Information Type:
Toxicity testing of sediments
Data Used to Assess Water Quality:
Data used to evaluate sediment toxicity comprise one sediment sample collected by the SWAMP in 2001. No toxicity or adverse affects were exhibited for Hyallela azteca.
All waters shall be maintained free of toxic substances that are lethal to or that produce other detrimental responses in aquatic organisms.
There shall be no chronic toxicity in ambient waters. Chronic toxicity is a detrimental biological effect on growth rate, reproduction, fertilization success, larval development, population abundance, community composition, or any other relevant measure of the health of an organism, population, or community.
Sediment toxicity was evaluated according to the SWAMP methodology. Sample toxicity was determined by comparing mean organism response in samples and in negative controls. Statistical evaluation (alpha = 0.05) and a default threshold of 80% of the control value were used to establish whether the sediment exhibited significant toxicity adversely impacting aquatic organisms.