Final California 2020 Integrated Report (303(d) List/305(b) Report)

Supporting Information

Regional Board 9 - San Diego Region

Water Body Name:	Arroyo Trabuco Creek, Upper
Water Body ID:	CAR9012200020200716063560
Water Body Type:	River & Stream


DECISION ID	105540	Region 9
Arroyo Trabuco Creek, Upper

Pollutant:	Benthic Community Effects
Final Listing Decision:	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
Reason for Delisting:	Delisting due to spatial change or other CalWQA administrative reason
Expected TMDL Completion Date:	2025
Impairment from Pollutant or Pollution:	Pollutant

Regional Board Conclusion:	Benthic Community Effects is being considered for delisting from the CWA Section 303(d) list under sections 4.9 and 4.1 of the Listing Policy. Based on the readily available data and information, the weight of evidence provides sufficient justification for removing Benthic Community Effects in this water segment from 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. Pursuant to section 4.9 of the Listing Policy, the water does not exhibit significant degradation in biological populations and/or communities as compared to reference site(s) using the California Stream Condition Index. This segment was remapped during this cycle and CSCI scores within the segment do not warrant listing for impairment. 4. Pursuant to section 4.11 of the Listing Policy, additional data and information are available indicating that standards are being met.

Regional Board Decision Recommendation:	After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should be removed from the section 303(d) list because applicable water quality standards for the pollutant 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.

Line of Evidence (LOE) for Decision ID 105540, Benthic Community Effects	Region 9
Arroyo Trabuco Creek, Upper

LOE ID:

134409

Pollutant:

Benthic-Macroinvertebrate Bioassessments

LOE Subgroup:

Population/Community Degradation

Matrix:

Water

Fraction:

Not Recorded

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

Benthic macroinvertebrate surveys

Data Used to Assess Water Quality:

Seven samples were collected at two stations in upper Arroyo Trabuco. All scored samples were above the 0.79 threshold, and therefore not exceeding the water quality objective for the aquatic life beneficial use. One sample was not scored due to low organism counts.

Data Reference:

Statewide Ref Condition Management Plan 2008

Data for Various Waterbodies in Region 8 and Region 9, 2006-2009.

Region 9 CSCI Scores & Water Body Information

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

All waters shall be maintained free of toxic substances in concentrations that are toxic to, or that produce detrimental physiological responses in, human, plant or animal, or aquatic life. Compliance with this objective will be determined by use of indicator organisms, analysis of species diversity, population density, growth anomalies, bioassays of appropriate duration, or other appropriate methods as specified by the Regional Board. Region 9 Basin Plan.

Objective/Criterion Reference:

Water Quality Control Plan for the San Diego Basin

Evaluation Guideline:

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 (Rhen, 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.

Guideline Reference:

Bioassessment in complex environments: designing an index for consistent meaning in different settings

Spatial Representation:

The samples were collected at stations 901ATCAAS and REF-TCAS.

Temporal Representation:

The samples were collected from 2006 to 2009.

Environmental Conditions:

QAPP Information:

Data collected following SWAMP QA protocols for the County of Orange NPDES MS4 Copermittees Receiving Waters Monitoring and Reporting Program and for the SWAMP Statewide Reference Condition Management Plan 2008.

QAPP Information Reference(s):

Statewide Ref Condition Management Plan 2008

QAPP Information Reference(s):

Quality Assurance Project Plan for the Orange County Stormwater Program.

Line of Evidence (LOE) for Decision ID 105540, Benthic Community Effects	Region 9
Arroyo Trabuco Creek, Upper

LOE ID:

215716

Pollutant:

Benthic-Macroinvertebrate Bioassessments

LOE Subgroup:

Population/Community Degradation

Matrix:

Water

Fraction:

None

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

Benthic macroinvertebrate surveys

Data Used to Assess Water Quality:

Water Board staff assessed data for 901RFTCAS to determine beneficial use support and the results are as follows: 1 of 9 samples exceeded the threshold. CSCI scores were from 0.6607 to 1.019 .

Data Reference:

California Stream Condition Index Scores for the 2020 Integrated Report

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the San Diego Basin

Evaluation Guideline:

Guideline Reference:

Bioassessment in complex environments: designing an index for consistent meaning in different settings

Spatial Representation:

Samples were collected from station 901RFTCAS

Temporal Representation:

Samples were collected from 6/15/2011 to 6/1/2017.

Environmental Conditions:

QAPP Information:

The data was collected under a permit required receiving waters monitoring and reporting program

QAPP Information Reference(s):

Quality Assurance Project Plan for Southern California Regional Watershed Monitoring Program Bioassessment, Version 1.0, and Freshwater Bioassessment from Weston Solutions.


DECISION ID	105568	Region 9
Arroyo Trabuco Creek, Upper

Pollutant:	Diazinon
Final Listing Decision:	Delist from 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	Delist from 303(d) list (TMDL required list)(2018)
Revision Status	Revised
Reason for Delisting:	Delisting due to spatial change or other CalWQA administrative reason
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. Zero of the five samples exceed the water quality threshold. This sample size is insufficient to determine beneficial use support with the statistical power and confidence of the Listing Policy. Based on the readily available data and information, the weight of evidence indicates that there is sufficient justification for this water segment-pollutant combination to remain delisted from 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. Zero of the five samples exceed the water quality threshold, and this sample size is insufficient information in Table 3.1. 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.

Line of Evidence (LOE) for Decision ID 105568, Diazinon	Region 9
Arroyo Trabuco Creek, Upper

LOE ID:

216570

Pollutant:

Diazinon

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total Dissolved

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

Fixed station physical/chemical monitoring (conventional pollutants only)

Data Used to Assess Water Quality:

None of the five samples exceed the continuous concentration for Diazinon criteria of 0.1 ug/L.

Data Reference:

Data for Various Waterbodies in Region 8 and Region 9, 2006-2009.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

No individual pesticide or combination of pesticides shall be present in the water column, sediments or biota at concentration(s) that adversely affect beneficial uses.

Objective/Criterion Reference:

Water Quality Control Plan for the San Diego Basin

Evaluation Guideline:

The freshwater chronic value for diazinon is 0.1 ug/L, expressed as a continuous concentration (Finlayson, 2004).

Guideline Reference:

Water quality for diazinon. Memorandum to J. Karkoski, Central Valley RWQCB. Rancho Cordova, CA: Pesticide Investigation Unit, CA Department of Fish and Game

Spatial Representation:

Samples were collected at 1 monitoring site (REF-TCAS).

Temporal Representation:

Samples were collected from 9/26/2006 through 4/30/2009.

Environmental Conditions:

QAPP Information:

Data were submitted with the County of Orange Stormwater Program Quality Assurance Management Plan (QAMP) dated January 2010. However, data were collected prior to the development of this QAMP, therefore the quality of these data are unknown

QAPP Information Reference(s):

This is a placeholder for previously assessed data that does not have quality assurance information but would require it under newly developed policies. These LOEs were previously assessed and approved at the Regional, State and Federal level in past cycles. The LOEs needed to be moved and/or reassessed but required this reference code for movement within the decision making database.

Line of Evidence (LOE) for Decision ID 105568, Diazinon	Region 9
Arroyo Trabuco Creek, Upper

LOE ID:

216560

Pollutant:

Diazinon

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total Dissolved

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

Fixed station physical/chemical monitoring (conventional pollutants only)

Data Used to Assess Water Quality:

None of the five samples exceed the CADPH Notification Level for Diazinon criteria.

Data Reference:

Data for Various Waterbodies in Region 8 and Region 9, 2006-2009.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

No individual pesticide or combination of pesticides shall be present in the water column, sediments or biota at concentration(s) that adversely affect beneficial uses.

Objective/Criterion Reference:

Water Quality Control Plan for the San Diego Basin

Evaluation Guideline:

The California Department of Public Health (CDPH) Notification Level for Diazinon is 1.2 ug/L.

Guideline Reference:

Drinking Water Notification and Response Levels: An Overview

Spatial Representation:

Samples were collected at 1 monitoring site (REF-TCAS).

Temporal Representation:

Samples were collected from 9/26/2006 through 4/30/2009.

Environmental Conditions:

QAPP Information:

QAPP Information Reference(s):


DECISION ID	105545	Region 9
Arroyo Trabuco Creek, Upper

Pollutant:	Malathion
Final Listing Decision:	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
Reason for Delisting:	Flaws in original listing
Expected TMDL Completion Date:	2029
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.

Line of Evidence (LOE) for Decision ID 105545, Malathion	Region 9
Arroyo Trabuco Creek, Upper

LOE ID:

216540

Pollutant:

Malathion

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total Dissolved

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

Fixed station physical/chemical monitoring (conventional pollutants only)

Data Used to Assess Water Quality:

Zero of five samples exceed the maximum (Instantaneous) concentration for Malathion in freshwater of 100 ng/L.

Data Reference:

Data for Various Waterbodies in Region 8 and Region 9, 2006-2009.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

No individual pesticide or combination of pesticides shall be present in the water column, sediments or biota at concentration(s) that adversely affect beneficial uses.

Objective/Criterion Reference:

Water Quality Control Plan for the San Diego Basin

Evaluation Guideline:

The maximum (Instantaneous) concentration for Malathion in freshwater is 100 ng/L.

Guideline Reference:

Quality Criteria for Water. USEPA Office of Water and Hazardous Materials. Washington, D.C

Spatial Representation:

Samples were collected at 1 monitoring site (REF-TCAS).

Temporal Representation:

Samples were collected from 9/26/2006 through 4/30/2009.

Environmental Conditions:

QAPP Information:

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 105545, Malathion	Region 9
Arroyo Trabuco Creek, Upper

LOE ID:

216564

Pollutant:

Malathion

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total Dissolved

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

Fixed station physical/chemical monitoring (conventional pollutants only)

Data Used to Assess Water Quality:

None of five samples exceed the CDPH notification level for Malathion criteria of 160.0 ug/L.

Data Reference:

Data for Various Waterbodies in Region 8 and Region 9, 2006-2009.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

No individual pesticide or combination of pesticides shall be present in the water column, sediments or biota at concentration(s) that adversely affect beneficial uses.

Objective/Criterion Reference:

Water Quality Control Plan for the San Diego Basin

Evaluation Guideline:

The California Department of Public Health (CDPH) notification level criteria for malathion in freshwater is 160.0 ug/L.

Guideline Reference:

2006 edition of the drinking water standards and health advisories. EPA 822-R-03-013

Spatial Representation:

Samples were collected at 1 monitoring site (REF-TCAS).

Temporal Representation:

Samples were collected from 9/26/2006 through 4/30/2009.

Environmental Conditions:

QAPP Information:

QAPP Information Reference(s):


DECISION ID	105539	Region 9
Arroyo Trabuco Creek, Upper

Pollutant:	Toxicity
Final Listing Decision:	Do Not Delist from 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	Do Not Delist from 303(d) list (TMDL required list)(2018)
Revision Status	Revised
Sources:	A Source Unknown
Expected TMDL Completion Date:	2019
Impairment from Pollutant or Pollution:	Pollutant

Regional Board Conclusion:	This pollutant is being considered for removal from the CWA section 303(d) List under sections 4.1 and 4.6 of the Listing Policy. Under sections 4.1 and 4.6, at least one line of evidence is necessary to assess listing status. Six lines of evidence are available in the administrative record to assess this pollutant. Two of eight water samples exhibited toxicity, and one of one sediment sample exhibited toxicity. Based on the readily available data and information, the weight of evidence indicates that there is sufficient justification against removing this water segment-pollutant combination from 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. Two of eight water samples and two of four sediment samples exhibited toxicity, and this sample size is sufficient to determine beneficial use support, with the power and confidence of the Listing Policy. 4. Pursuant to section 4.11 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 removed from the section 303(d) list because applicable water quality standards for the pollutant are 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.

Line of Evidence (LOE) for Decision ID 105539, Toxicity	Region 9
Arroyo Trabuco Creek, Upper

LOE ID:

216565

Pollutant:

Toxicity

LOE Subgroup:

Toxicity

Matrix:

Sediment

Fraction:

Not Recorded

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

TOXICITY TESTING

Data Used to Assess Water Quality:

One of the one samples collected show significant toxicity levels (SL) to Hyalella azteca survival (%) according to results from the Surface Ambient Monitoring Program results (SWAMP, 2007).

Data Reference:

Monitoring data for Region 9

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

From the Basin Plan, all waters shall be free of toxic substances that are toxic to, or that produce detrimental physiological responses in human, plant, animal, or aquatic life (RWQCB, 2007).

Objective/Criterion Reference:

Water Quality Control Plan for the San Diego Basin

Evaluation Guideline:

According to SWAMP, waters are considered toxic when samples show significant toxicity levels (SWAMP code SL) when compared to a negative control. Significant toxicity is determined when statistical tests result in an alpha of less than 5% and percent control values less than the evaluation threshold.

Guideline Reference:

Short-term Methods for Estimating the Chronic Toxicity of Effluents and Receiving Waters to Freshwater Organisms. Fourth Edition. Office of Water, U.S. Environmental Protection Agency. Washington, D.C. EPA-821-R-02-013

Spatial Representation:

The samples were collected at 1 monitoring site (901SJATC2).

Temporal Representation:

Sediment samples were collected on 5/12/2013.

Environmental Conditions:

QAPP Information:

Quality control for this study was conducted in accordance with the California's Surface Water Ambient Monitoring Program.

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 105539, Toxicity	Region 9
Arroyo Trabuco Creek, Upper

LOE ID:

216551

Pollutant:

Toxicity

LOE Subgroup:

Toxicity

Matrix:

Water

Fraction:

None

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

TOXICITY TESTING

Data Used to Assess Water Quality:

Six samples were collected to test for toxicity. Zero of the six samples exhibited statistically and biologically significant toxicity.

Data Reference:

Data for Various Waterbodies in Region 8 and Region 9, 2006-2009.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

From the Basin Plan, all waters shall be free of toxic substances that are toxic to, or that produce detrimental physiological responses in human, plant, animal, or aquatic life (RWQCB, 2007).

Objective/Criterion Reference:

Water Quality Control Plan for the San Diego Basin

Evaluation Guideline:

Toxicity is defined as a statistically significant effect in the sample exposure compared to the control using EPA-recommended hypothesis testing. The t-test is used to determine if there is a statistically significant decrease in organism response in the sample as compared to the control. Additionally, the biological significance of the sample is evaluated by determining whether the sample response is lower than the evaluation threshold.

Guideline Reference:

Methods for Measuring the Acute Toxicity of Effluents and Receiving Waters to Freshwater and Marine Organisms, Fifth Edition. EPA-821-R-02-012

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site (REF-TCAS).

Temporal Representation:

The samples were collected from 6/30/2006 to 4/30/2009.

Environmental Conditions:

QAPP Information:

The data collected under the Quality Assurance Management Plan for The Orange County Stormwater Program. The SWAMP measurement quality objectives were followed for toxicity data. The performance of toxicity bioassays and evaluation of reference toxicants were performed using USEPA and Standard Methods.

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 105539, Toxicity	Region 9
Arroyo Trabuco Creek, Upper

LOE ID:

216566

Pollutant:

Toxicity

LOE Subgroup:

Toxicity

Matrix:

Water

Fraction:

Not Recorded

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

TOXICITY TESTING

Data Used to Assess Water Quality:

Two of the two samples collected show significant toxicity levels (SL) for Ceriodaphnia dubia young/female (#) (SWAMP, 2007).

Data Reference:

Monitoring data for Region 9

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

From the Basin Plan, all waters shall be free of toxic substances that are toxic to, or that produce detrimental physiological responses in human, plant, animal, or aquatic life (RWQCB, 2007).

Objective/Criterion Reference:

Water Quality Control Plan for the San Diego Basin

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site (901SJATC2).

Temporal Representation:

Water samples were collected from 4/14/2003 through 5/12/2003.

Environmental Conditions:

QAPP Information:

Quality control for this study was conducted in accordance with the California's Surface Water Ambient Monitoring Program.

QAPP Information Reference(s):


DECISION ID	105543	Region 9
Arroyo Trabuco Creek, Upper

Pollutant:	Arsenic
Final Listing Decision:	Do Not 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
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. Zero of the 47 samples exceed the water quality threshold. 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 in the Water Quality Limited Segments category. 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. Zero of the 47 samples exceed the water quality threshold, and this does not exceed 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 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.

Line of Evidence (LOE) for Decision ID 105543, Arsenic	Region 9
Arroyo Trabuco Creek, Upper

LOE ID:

134356

Pollutant:

Arsenic

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

Fixed station physical/chemical (conventional plus toxic pollutants)

Data Used to Assess Water Quality:

None of the 45 samples exceeded the water quality objective for arsenic.

Data Reference:

Data for Various Waterbodies in Region 8 and Region 9, 2006-2009.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

All waters shall be maintained free of toxic substances in concentrations that are toxic to, or that produce detrimental physiological responses in human, plant, animal, or aquatic life. Inland surface waters, enclosed bays, and estuaries shall not contain toxic pollutants in excess of the numerical objectives applicable to California specified in 40 CFR 131.36 (section 131.36 revised at 57 FR 60848, December 22, 1992).

Objective/Criterion Reference:

Water Quality Control Plan for the San Diego Basin

Evaluation Guideline:

California Toxics Rule (CTR) lists criterion continuous concentrations (4-day average) to protect aquatic life in freshwater. The CTR for arsenic is 150 ug/L.

Guideline Reference:

Code of Federal Regulations 40 part 131.38 Establishment of numeric criteria for priority toxic pollutants for the State of California. 7/1/2011 Edition

Spatial Representation:

Samples were collected from Arroyo Trabuco Creek / Alder Spring (REF-TCAS).

Temporal Representation:

The samples were collected from REF-TCAS on 9/26/06, 6/1/07, 11/6/07, 5/20/08, and 4/30/09.

Environmental Conditions:

The samples are representative of dry weather conditions.

QAPP Information:

Samples were collected and analyzed in accordance with the signed and certified, Quality Assurance Management Plan for the Orange County Stormwater Program.

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 105543, Arsenic	Region 9
Arroyo Trabuco Creek, Upper

LOE ID:

216607

Pollutant:

Arsenic

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

Fixed station physical/chemical (conventional plus toxic pollutants)

Data Used to Assess Water Quality:

Zero of the two samples exceeded the water quality objective for arsenic.

Data Reference:

Data for Various Waterbodies in Region 8 and Region 9, 2006-2009.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the San Diego Basin

Evaluation Guideline:

California Toxics Rule (CTR) lists criterion continuous concentrations (4-day average) to protect aquatic life in freshwater. The CTR for arsenic is 150 ug/L.

Guideline Reference:

Code of Federal Regulations 40 part 131.38 Establishment of numeric criteria for priority toxic pollutants for the State of California. 7/1/2011 Edition

Spatial Representation:

Samples were collected from 1 monitoring site (REF-TCAS).

Temporal Representation:

Samples were collected from 5/20/08 to 4/30/09.

Environmental Conditions:

QAPP Information:

Samples were collected and analyzed in accordance with the signed and certified, Quality Assurance Management Plan for the Orange County Stormwater Program.

QAPP Information Reference(s):


DECISION ID	105561	Region 9
Arroyo Trabuco Creek, Upper

Pollutant:	Cadmium
Final Listing Decision:	Do Not 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
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.

Line of Evidence (LOE) for Decision ID 105561, Cadmium	Region 9
Arroyo Trabuco Creek, Upper

LOE ID:

216556

Pollutant:

Cadmium

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

Fixed station physical/chemical (conventional plus toxic pollutants)

Data Used to Assess Water Quality:

Zero of the five samples exceeded the hardness adjusted water quality objective for cadmium.

Data Reference:

Data for Various Waterbodies in Region 8 and Region 9, 2006-2009.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the San Diego Basin

Evaluation Guideline:

California Toxics Rule (CTR) lists criterion continuous concentrations (4-day average) to protect aquatic life in freshwater. The dissolved criterion in freshwater is hardness dependent for each sample and varies based on the ambient hardness during sampling. Section (b)(1) in CTR contains the hardness dependent formula for the metals criterion.

Guideline Reference:

Code of Federal Regulations 40 part 131.38 Establishment of numeric criteria for priority toxic pollutants for the State of California. 7/1/2011 Edition

Spatial Representation:

Samples were collected from 1 monitoring site (REF-TCAS).

Temporal Representation:

Samples were collected from 9/26/2006 through 4/30/2009.

Environmental Conditions:

QAPP Information:

Samples were collected and analyzed in accordance with the signed and certified, Quality Assurance Management Plan for the Orange County Stormwater Program.

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 105561, Cadmium	Region 9
Arroyo Trabuco Creek, Upper

LOE ID:

216569

Pollutant:

Cadmium

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

Fixed station physical/chemical (conventional plus toxic pollutants)

Data Used to Assess Water Quality:

Zero of the five samples exceeded the water quality objective for cadmium.

Data Reference:

Data for Various Waterbodies in Region 8 and Region 9, 2006-2009.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the San Diego Basin

Evaluation Guideline:

Total cadmium levels should not exceed the California Department of Public Health Primary MCL of 5 ug/L.

Guideline Reference:

Public Health Goal for Cadmium in Drinking Water

Guideline Reference:

MCLs for Regulated Drinking Water Contaminants, California Department of Public Health.

Spatial Representation:

Samples were collected from 1 monitoring site (REF-TCAS).

Temporal Representation:

The samples were collected from 9/26/06 through 4/30/09.

Environmental Conditions:

QAPP Information:

Samples were collected and analyzed in accordance with the signed and certified, Quality Assurance Management Plan for the Orange County Stormwater Program.

QAPP Information Reference(s):


DECISION ID	105563	Region 9
Arroyo Trabuco Creek, Upper

Pollutant:	Chlorpyrifos
Final Listing Decision:	Do Not 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
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.

Line of Evidence (LOE) for Decision ID 105563, Chlorpyrifos	Region 9
Arroyo Trabuco Creek, Upper

LOE ID:

216557

Pollutant:

Chlorpyrifos

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total Dissolved

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

Fixed station physical/chemical monitoring (conventional pollutants only)

Data Used to Assess Water Quality:

None of five samples exceed the continuous concentration for Chlorpyrifos criteria of 14.0 ng/L, however for six samples the reporting limit was greater than the evaluation guideline, therefore these data are not of sufficient resolution to determine if water quality standards are being achieved.

Data Reference:

Data for Various Waterbodies in Region 8 and Region 9, 2006-2009.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

No individual pesticide or combination of pesticides shall be present in the water column, sediments or biota at concentration(s) that adversely affect beneficial uses.

Objective/Criterion Reference:

Water Quality Control Plan for the San Diego Basin

Evaluation Guideline:

The Criteria Continuous Concentration (four day average) for chlorpyrifos in freshwater is 14.0 ng/L. Ref12

Guideline Reference:

Water quality criteria for diazinon and chlorpyrifos. Administrative Report 00-3. Rancho Cordova, CA: Pesticide Investigations Unit, Office of Spills and Response. CA Department of Fish and Game

Spatial Representation:

Samples were collected at 1 monitoring sites (REF-TCAS).

Temporal Representation:

Samples were collected from 9/26/2006 through 4/30/2009.

Environmental Conditions:

QAPP Information:

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 105563, Chlorpyrifos	Region 9
Arroyo Trabuco Creek, Upper

LOE ID:

216542

Pollutant:

Chlorpyrifos

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total Dissolved

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

Fixed station physical/chemical monitoring (conventional pollutants only)

Data Used to Assess Water Quality:

None of five samples exceed the USEPA Health Advisory 2011 ed., criteria for chlorpyrifos.

Data Reference:

Data for Various Waterbodies in Region 8 and Region 9, 2006-2009.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

No individual pesticide or combination of pesticides shall be present in the water column, sediments or biota at concentration(s) that adversely affect beneficial uses.

Objective/Criterion Reference:

Water Quality Control Plan for the San Diego Basin

Evaluation Guideline:

USEPA Health Advisory 2011 ed., criteria for chlorpyrifos in freshwater is 2.0 ug/L (represents a life-time risk).

Guideline Reference:

2012 Edition of the Drinking Water Standards and Health Advisories

Spatial Representation:

Samples were collected at 1 monitoring site (REF-TCAS).

Temporal Representation:

Samples were collected from 9/26/2006 through 4/30/2009.

Environmental Conditions:

QAPP Information:

QAPP Information Reference(s):


DECISION ID	105565	Region 9
Arroyo Trabuco Creek, Upper

Pollutant:	Chromium
Final Listing Decision:	Do Not 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
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.

Line of Evidence (LOE) for Decision ID 105565, Chromium	Region 9
Arroyo Trabuco Creek, Upper

LOE ID:

216573

Pollutant:

Chromium

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

Fixed station physical/chemical (conventional plus toxic pollutants)

Data Used to Assess Water Quality:

None of the five samples exceeded the hardness adjusted water quality objective for chromium.

Data Reference:

Data for Various Waterbodies in Region 8 and Region 9, 2006-2009.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the San Diego Basin

Evaluation Guideline:

Guideline Reference:

Code of Federal Regulations 40 part 131.38 Establishment of numeric criteria for priority toxic pollutants for the State of California. 7/1/2011 Edition

Spatial Representation:

Samples were collected from 1 monitoring site (REF-TCAS).

Temporal Representation:

Samples were collected from 9/26/2006 through 4/30/2009.

Environmental Conditions:

QAPP Information:

Samples were collected and analyzed in accordance with the signed and certified, Quality Assurance Management Plan for the Orange County Stormwater Program.

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 105565, Chromium	Region 9
Arroyo Trabuco Creek, Upper

LOE ID:

216544

Pollutant:

Chromium

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

Fixed station physical/chemical (conventional plus toxic pollutants)

Data Used to Assess Water Quality:

None of the five samples exceeded the water quality objective for chromium.

Data Reference:

Data for Various Waterbodies in Region 8 and Region 9, 2006-2009.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the San Diego Basin

Evaluation Guideline:

The CDPH Primary MCL for chromium is 50 ug/L.

Guideline Reference:

Maximum Contaminant Levels for organic and inorganic chemicals. CCR Title 22

Spatial Representation:

Samples were collected from 1 monitoring site (REF-TCAS).

Temporal Representation:

The samples were collected from 9/26/2006 through 4/30/2009.

Environmental Conditions:

QAPP Information:

Samples were collected and analyzed in accordance with the signed and certified, Quality Assurance Management Plan for the Orange County Stormwater Program.

QAPP Information Reference(s):


DECISION ID	105567	Region 9
Arroyo Trabuco Creek, Upper

Pollutant:	Copper
Final Listing Decision:	Do Not 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
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.

Line of Evidence (LOE) for Decision ID 105567, Copper	Region 9
Arroyo Trabuco Creek, Upper

LOE ID:

216572

Pollutant:

Copper

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

Fixed station physical/chemical (conventional plus toxic pollutants)

Data Used to Assess Water Quality:

None of the five samples collected for dissolved copper exceeded the hardness adjusted water quality objective for copper.

Data Reference:

Data for Various Waterbodies in Region 8 and Region 9, 2006-2009.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the San Diego Basin

Evaluation Guideline:

Guideline Reference:

Code of Federal Regulations 40 part 131.38 Establishment of numeric criteria for priority toxic pollutants for the State of California. 7/1/2011 Edition

Spatial Representation:

Samples were collected from 1 monitoring site (REF-TCAS).

Temporal Representation:

Samples were collected from 9/26/2006 through 4/30/2009.

Environmental Conditions:

QAPP Information:

Samples were collected and analyzed in accordance with the signed and certified, Quality Assurance Management Plan for the Orange County Stormwater Program.

QAPP Information Reference(s):


DECISION ID	105571	Region 9
Arroyo Trabuco Creek, Upper

Pollutant:	Lead
Final Listing Decision:	Do Not 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
Impairment from Pollutant or Pollution:	Pollution

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.

Line of Evidence (LOE) for Decision ID 105571, Lead	Region 9
Arroyo Trabuco Creek, Upper

LOE ID:

216561

Pollutant:

Lead

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

Fixed station physical/chemical (conventional plus toxic pollutants)

Data Used to Assess Water Quality:

Zero of five samples exceeded the hardness adjusted water quality objective for lead.

Data Reference:

Data for Various Waterbodies in Region 8 and Region 9, 2006-2009.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the San Diego Basin

Evaluation Guideline:

Guideline Reference:

Code of Federal Regulations 40 part 131.38 Establishment of numeric criteria for priority toxic pollutants for the State of California. 7/1/2011 Edition

Spatial Representation:

Samples were collected from 1 monitoring site (REF-TCAS).

Temporal Representation:

Samples were collected from 9/26/2006 through 4/30/2009.

Environmental Conditions:

QAPP Information:

Samples were collected and analyzed in accordance with the signed and certified, Quality Assurance Management Plan for the Orange County Stormwater Program.

QAPP Information Reference(s):


DECISION ID	105548	Region 9
Arroyo Trabuco Creek, Upper

Pollutant:	Nickel
Final Listing Decision:	Do Not 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
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.

Line of Evidence (LOE) for Decision ID 105548, Nickel	Region 9
Arroyo Trabuco Creek, Upper

LOE ID:

216577

Pollutant:

Nickel

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

Fixed station physical/chemical (conventional plus toxic pollutants)

Data Used to Assess Water Quality:

None of the five samples exceeded the hardness adjusted water quality objective for nickel.

Data Reference:

Data for Various Waterbodies in Region 8 and Region 9, 2006-2009.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the San Diego Basin

Evaluation Guideline:

Guideline Reference:

Code of Federal Regulations 40 part 131.38 Establishment of numeric criteria for priority toxic pollutants for the State of California. 7/1/2011 Edition

Spatial Representation:

Samples were collected from 1 monitoring site (REF-TCAS).

Temporal Representation:

Samples were collected from 9/26/2006 through 4/30/2009.

Environmental Conditions:

QAPP Information:

Samples were collected and analyzed in accordance with the signed and certified, Quality Assurance Management Plan for the Orange County Stormwater Program.

QAPP Information Reference(s):


DECISION ID	105550	Region 9
Arroyo Trabuco Creek, Upper

Pollutant:	Oxygen, Dissolved
Final Listing Decision:	Do Not 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
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.

Line of Evidence (LOE) for Decision ID 105550, Oxygen, Dissolved	Region 9
Arroyo Trabuco Creek, Upper

LOE ID:

134366

Pollutant:

Oxygen, Dissolved

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

The sample collected did not exceed the objective.

Data Reference:

Statewide Ref Condition Management Plan 2008

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

Dissolved oxygen levels shall not be less than 5.0 mg/l in inland surface waters with designated MAR or WARM beneficial uses or less than 6.0 mg/l in waters with designated COLD beneficial uses. The annual mean dissolved oxygen concentration shall not be less than 7 mg/l more than 10% of the time

Objective/Criterion Reference:

Water Quality Control Plan for the San Diego Basin

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

Samples were collected from the 901ATCAAS station.

Temporal Representation:

One sample was collected on 6/5/2008

Environmental Conditions:

QAPP Information:

SWAMP QAPP

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 105550, Oxygen, Dissolved	Region 9
Arroyo Trabuco Creek, Upper

LOE ID:

216579

Pollutant:

Oxygen, Dissolved

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Zero of the five samples exceeded the objective.

Data Reference:

Data for Various Waterbodies in Region 8 and Region 9, 2006-2009.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the San Diego Basin

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

Samples were collected from 1 monitoring site (REF-TCAS).

Temporal Representation:

Samples were collected from 9/26/2006 through 4/30/2009.

Environmental Conditions:

QAPP Information:

NPDES quality assurance.

QAPP Information Reference(s):


DECISION ID	105554	Region 9
Arroyo Trabuco Creek, Upper

Pollutant:	Selenium
Final Listing Decision:	Do Not 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
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.

Line of Evidence (LOE) for Decision ID 105554, Selenium	Region 9
Arroyo Trabuco Creek, Upper

LOE ID:

216547

Pollutant:

Selenium

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

Fixed station physical/chemical (conventional plus toxic pollutants)

Data Used to Assess Water Quality:

None of the two samples exceeded the water quality objective for selenium. Non-detect samples with reporting limits greater than the water quality threshold were not used in this assessment.

Data Reference:

Data for Various Waterbodies in Region 8 and Region 9, 2006-2009.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the San Diego Basin

Evaluation Guideline:

California Toxics Rule (CTR) lists criterion continuous concentrations (4-day average) to protect aquatic life in freshwater. The CTR for selenium is 5.0 ug/L.

Guideline Reference:

Code of Federal Regulations 40 part 131.38 Establishment of numeric criteria for priority toxic pollutants for the State of California. 7/1/2011 Edition

Spatial Representation:

Samples were collected from 1 monitoring site (REF-TCAS).

Temporal Representation:

Samples were collected from 5/20/2008 through 4/30/2009.

Environmental Conditions:

QAPP Information:

Samples were collected and analyzed in accordance with the signed and certified, Quality Assurance Management Plan for the Orange County Stormwater Program.

QAPP Information Reference(s):


DECISION ID	105556	Region 9
Arroyo Trabuco Creek, Upper

Pollutant:	Silver
Final Listing Decision:	Do Not 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
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.

Line of Evidence (LOE) for Decision ID 105556, Silver	Region 9
Arroyo Trabuco Creek, Upper

LOE ID:

216548

Pollutant:

Silver

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

Fixed station physical/chemical (conventional plus toxic pollutants)

Data Used to Assess Water Quality:

None of the five samples exceeded the hardness adjusted water quality objective for silver.

Data Reference:

Data for Various Waterbodies in Region 8 and Region 9, 2006-2009.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the San Diego Basin

Evaluation Guideline:

California Toxics Rule (CTR) lists criterion maximum concentrations for silver to protect aquatic life in freshwater (1-hour average). The dissolved silver criterion in freshwater is hardness dependent for each sample and varies based on the ambient hardness during sampling. Section (b)(1) in CTR contains the hardness dependent formula for the metals criterion. If no hardness data were available, a value of 100 mg/L was used.

Guideline Reference:

Code of Federal Regulations 40 part 131.38 Establishment of numeric criteria for priority toxic pollutants for the State of California. 7/1/2011 Edition

Spatial Representation:

Samples were collected from 1 monitoring site (REF-TCAS).

Temporal Representation:

Samples were collected from 9/26/2006 through 4/30/2009.

Environmental Conditions:

QAPP Information:

Samples were collected and analyzed in accordance with the signed and certified, Quality Assurance Management Plan for the Orange County Stormwater Program.

QAPP Information Reference(s):


DECISION ID	105559	Region 9
Arroyo Trabuco Creek, Upper

Pollutant:	Zinc
Final Listing Decision:	Do Not 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
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.

Line of Evidence (LOE) for Decision ID 105559, Zinc	Region 9
Arroyo Trabuco Creek, Upper

LOE ID:

216554

Pollutant:

Zinc

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

Fixed station physical/chemical (conventional plus toxic pollutants)

Data Used to Assess Water Quality:

None of the five samples exceeded the hardness adjusted water quality objective for zinc.

Data Reference:

Data for Various Waterbodies in Region 8 and Region 9, 2006-2009.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the San Diego Basin

Evaluation Guideline:

Guideline Reference:

Code of Federal Regulations 40 part 131.38 Establishment of numeric criteria for priority toxic pollutants for the State of California. 7/1/2011 Edition

Spatial Representation:

Samples were collected from 1 monitoring site (REF-TCAS).

Temporal Representation:

Samples were collected from 9/26/2006 through 4/30/2009.

Environmental Conditions:

QAPP Information:

Samples were collected and analyzed in accordance with the signed and certified, Quality Assurance Management Plan for the Orange County Stormwater Program.

QAPP Information Reference(s):


DECISION ID	105552	Region 9
Arroyo Trabuco Creek, Upper

Pollutant:	pH
Final Listing Decision:	Do Not 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
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.

Line of Evidence (LOE) for Decision ID 105552, pH	Region 9
Arroyo Trabuco Creek, Upper

LOE ID:

216576

Pollutant:

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

None of the five samples exceeded the water quality threshold for pH.

Data Reference:

Data for Various Waterbodies in Region 8 and Region 9, 2006-2009.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The pH of all inland surface waters shall not be depressed below 6.5 or raised above 8.5 as a result of waste discharges.

Objective/Criterion Reference:

Water Quality Control Plan for the San Diego Basin

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

Samples were collected from 1 monitoring site (REF-TCAS).

Temporal Representation:

Samples were collected from 9/26/2006 through 4/30/2009.

Environmental Conditions:

QAPP Information:

NPDES quality assurance.

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 105552, pH	Region 9
Arroyo Trabuco Creek, Upper

LOE ID:

134371

Pollutant:

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

0 of 0 samples exceed the water quality objective. The data are reported as non-detects and have been omitted from the sample count.

Data Reference:

Statewide Ref Condition Management Plan 2008

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

Water Quality Control Plan, San Diego Region (SDRWQCB 2007): In inland surface waters the pH shall not be depressed below 6.5 nor raised above 8.5.

Objective/Criterion Reference:

Water Quality Control Plan for the San Diego Basin

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

Samples were collected at 901ATCAAS (Arroyo Trabuco).

Temporal Representation:

Sample collected 6/5/2008.

Environmental Conditions:

QAPP Information:

SWAMP QAPP (2008) was followed.

QAPP Information Reference(s):

Surface Water Ambient Monitoring Program Quality Assurance Program Plan