Draft California 2026 Integrated Report (303(d) List/305(b) Report)

Supporting Information

Regional Board 5 - Central Valley Region

Water Body Name:	Little Potato Slough (in Delta Waterways, central portion)
Water Body ID:	CAR5440000020101103102717
Water Body Type:	River & Stream


DECISION ID	167481	Region 5
Little Potato Slough (in Delta Waterways, central portion)

Pollutant:	Ammonia
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 3.1 of the Listing Policy. Zero samples exceeded the objectives, guidelines, or criteria for beneficial uses applicable to this water segment-pollutant combination, which is less than the minimum number of exceedances needed to place the water segment on the section CWA section 303(d) List for toxicants (Table 3.1 of the Listing Policy). The data used satisfies the data quality requirements (section 6.1.4) and data quantity requirements (section 6.1.5) of the Listing Policy. Pursuant to section 3.11 of the Listing Policy, no additional data and information are available indicating that standards are not met. 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.

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:

Line of Evidence (LOE) for Decision ID 167481, Ammonia	Region 5
Little Potato Slough (in Delta Waterways, central portion)

LOE ID:

321382

Pollutant:

Nitrogen, ammonia (Total Ammonia)

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Fish Spawning

Number of Samples:

126

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

None of 30-day averages exceeded the evaluation guideline for total ammonia as N. Ammonia samples that did not have corresponding pH and temperature data were not used to calculate averages.

Data Reference:

Data for Nutrients in Region 5, Jan. 1975 - Jan. 2007.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Water Quality Control Plan, Central Valley Region Sacramento River Basin and San Joaquin River Basin: waters shall not contain chemical constituents in concentrations that adversely affect beneficial uses.

Objective/Criterion Reference:

Water Quality Control Plan for the California Regional Water Quality Control Board Central Valley Region, Sacramento and San Joaquin River Basins. 4th ed

Evaluation Guideline:

The USEPA recommended freshwater aquatic life ambient water quality criteria for ammonia is based on pH, temperature, and the presence of early life stages of fish. The continuous concentration used is based on a 30-day average.

Guideline Reference:

1999 Update of Ambient Water Quality Criteria for Ammonia

Spatial Representation:

Samples were collected at stations: MD7A, Little Potato Slough @ Terminous

Temporal Representation:

Samples were collected from 1975 to 2010.

Environmental Conditions:

QAPP Information:

Samples were collected as part of a long term monitoring of water quality. No other description of the study were provided. None of the supporting documents describe the data collection during this time period.

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.


DECISION ID	131247	Region 5
Little Potato Slough (in Delta Waterways, central portion)

Pollutant:	Mercury
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 section 303(d) list under section 3.5 of the Listing Policy. Under section 3.5 a single line of evidence is necessary to assess listing status. 8 lines of evidence are available in the administrative record to assess the pollutant. WILD beneficial use: LOE 223281: 0 of 1 samples exceed the mercury objective and consist of 11 trophic level 4 fish. Fish lengths are within CDFW length limits. COMM beneficial use: LOE 223333: 0 of 1 samples exceed the mercury objective and consist of 11 trophic level 4 fish. Fish lengths are within CDFW length limits. LOE 191047: 0 of 4 samples exceed the mercury objective. LOE 191105: 0 of 4 samples exceed the mercury objective. WARM beneficial use: LOE 191142: 0 of 4 samples exceed the mercury objective. LOE 191144: 0 of 4 samples exceed the mercury objective. MUN beneficial use: LOE 191008: 0 of 4 samples exceed the mercury objective. LOE 191166: 0 of 4 samples exceed the mercury 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 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. 0 of 1 samples exceed the objective for the WILD beneficial use. For the COMM beneficial use, 0 of 1 samples exceed the sport fish objective, 0 of 4 samples exceed the objective for the dissolved fraction of mercury in the water column, and 0 of 4 samples exceed the objective for the total fraction of mercury in the water column. 0 of 8 samples exceed the objective for the WARM beneficial use. 0 of 8 samples exceed the objective for the MUN beneficial use. 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. 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:	This decision was made by SWRCB staff.

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 131247, Mercury	Region 5
Little Potato Slough (in Delta Waterways, central portion)

LOE ID:

191008

Pollutant:

Mercury

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed Delta RMP - Mercury data for Potato Slough, Little (San Joaquin County) to determine beneficial use support and results are as follows: 0 of 4 samples exceeded the water quality threshold for Mercury.

Data Reference:

Tissue, Water data for the 2020/2022 integrated report in Region 5.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The mercury criteria for the protection of human health from the consumption of water and organisms is 0.050 ug/L (California Toxics Rule, 2000).

Objective/Criterion Reference:

Water Quality Standards 2000. Establishment of numeric criteria for priority toxic pollutants for the State of California: Rules and regulations. Federal Register Vol. 65, No. 97. Washington, D.C.: Environmental Protection Agency

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site (544LILPSL)

Temporal Representation:

The samples were collected between the dates of 2016-08-22 and 2017-04-25

Environmental Conditions:

QAPP Information:

San Francisco Estuary Institute (SFEI). 2016. Delta Regional Monitoring Program Quality Assurance Program Plan (Delta RMP QAPP 2016) .

QAPP Information Reference(s):

Delta Regional Monitoring Program Quality Assurance Program Plan (Delta RMP QAPP 2016)

Line of Evidence (LOE) for Decision ID 131247, Mercury	Region 5
Little Potato Slough (in Delta Waterways, central portion)

LOE ID:

191047

Pollutant:

Mercury

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Commercial or recreational collection of fish, shellfish, or organisms

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

Tissue, Water data for the 2020/2022 integrated report in Region 5.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The mercury criteria for the protection of human health from consumption of organisms only is 0.051 ug/L (California Toxics Rule, 2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site (544LILPSL)

Temporal Representation:

The samples were collected between the dates of 2016-08-22 and 2017-04-25

Environmental Conditions:

QAPP Information:

San Francisco Estuary Institute (SFEI). 2016. Delta Regional Monitoring Program Quality Assurance Program Plan (Delta RMP QAPP 2016) .

QAPP Information Reference(s):

Delta Regional Monitoring Program Quality Assurance Program Plan (Delta RMP QAPP 2016)

Line of Evidence (LOE) for Decision ID 131247, Mercury	Region 5
Little Potato Slough (in Delta Waterways, central portion)

LOE ID:

191105

Pollutant:

Mercury

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Commercial or recreational collection of fish, shellfish, or organisms

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

Tissue, Water data for the 2020/2022 integrated report in Region 5.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The mercury criteria for the protection of human health from consumption of organisms only is 0.051 ug/L (California Toxics Rule, 2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site (544LILPSL)

Temporal Representation:

The samples were collected between the dates of 2016-08-22 and 2017-04-25

Environmental Conditions:

QAPP Information:

San Francisco Estuary Institute (SFEI). 2016. Delta Regional Monitoring Program Quality Assurance Program Plan (Delta RMP QAPP 2016) .

QAPP Information Reference(s):

Delta Regional Monitoring Program Quality Assurance Program Plan (Delta RMP QAPP 2016)

Line of Evidence (LOE) for Decision ID 131247, Mercury	Region 5
Little Potato Slough (in Delta Waterways, central portion)

LOE ID:

191144

Pollutant:

Mercury

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:

Data Reference:

Tissue, Water data for the 2020/2022 integrated report in Region 5.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

All waters shall be maintained free of toxic substances in concentrations which are toxic to, or which produce detrimental physiological responses in, human, plant, animal, or aquatic life. (Water Quality Control Plan for the Sacramento and San Joaquin River Basins).

Objective/Criterion Reference:

Water Quality Control Plan for the California Regional Water Quality Control Board Central Valley Region, Sacramento and San Joaquin River Basins; Fifth Edition. Revised May 2018 (with approved amendments)

Evaluation Guideline:

National Recommended Water Quality Criteria Continuous Concentrations (4-day average concentrations) for freshwater aquatic organisms exposure to total mercury is 0.77 ug/L.

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site (544LILPSL)

Temporal Representation:

The samples were collected between the dates of 2016-08-22 and 2017-04-25

Environmental Conditions:

QAPP Information:

San Francisco Estuary Institute (SFEI). 2016. Delta Regional Monitoring Program Quality Assurance Program Plan (Delta RMP QAPP 2016) .

QAPP Information Reference(s):

Delta Regional Monitoring Program Quality Assurance Program Plan (Delta RMP QAPP 2016)

Line of Evidence (LOE) for Decision ID 131247, Mercury	Region 5
Little Potato Slough (in Delta Waterways, central portion)

LOE ID:

191142

Pollutant:

Mercury

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

Tissue, Water data for the 2020/2022 integrated report in Region 5.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Evaluation Guideline:

National Recommended Water Quality Criteria Continuous Concentrations (4-day average concentrations) for freshwater aquatic organisms exposure to total mercury is 0.77 ug/L.

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site (544LILPSL)

Temporal Representation:

The samples were collected between the dates of 2016-08-22 and 2017-04-25

Environmental Conditions:

QAPP Information:

San Francisco Estuary Institute (SFEI). 2016. Delta Regional Monitoring Program Quality Assurance Program Plan (Delta RMP QAPP 2016) .

QAPP Information Reference(s):

Delta Regional Monitoring Program Quality Assurance Program Plan (Delta RMP QAPP 2016)

Line of Evidence (LOE) for Decision ID 131247, Mercury	Region 5
Little Potato Slough (in Delta Waterways, central portion)

LOE ID:

223281

Pollutant:

Mercury

LOE Subgroup:

Pollutant-Tissue

Matrix:

Tissue

Fraction:

Fish fillet

Beneficial Use:

Wildlife Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed Delta RMP - Mercury data for Potato Slough, Little (San Joaquin County) to determine beneficial use support and the results are as follows: 0 of the 1 samples exceeded the water quality threshold for Mercury. This LOE contains data only for trophic level 4 fish. The concentration of Mercury in fish collected within the same calendar year, for the same trophic level were averaged into a single sample for comparison with the objective. A total of 11 fish were aggregated into 1 annual averages, which consisted of 1 fish species (11 composite(s) of Largemouth Bass each composed of 1 fish per composite). This LOE does not contain data from fish who's average length was outside of the legal size limits as described by the California Department of Fish and Wildlife Fishing Regulations.

Data Reference:

Tissue, Water data for the 2020/2022 integrated report in Region 5.

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. (Water Quality Control Plan for the California Regional Water Quality Control Board Central Valley Region, Sacramento and San Joaquin River Basins)

Objective/Criterion Reference:

Water Quality Control Plan for the California Regional Water Quality Control Board Central Valley Region, Sacramento and San Joaquin River Basins. 4th ed

Evaluation Guideline:

The Statewide Sport Fish Water Quality Objective for the protection of Wildlife Habitat comes from the Statewide Water Quality Control Plan for Inland Surface Waters, Enclosed Bays, and Estuaries of California, and is 0.2 mg/Kg wet weight skinless fillet samples of trophic level 3, or trophic level 4 fish (whichever is highest in the water body) over a one year averaging period. If trophic level 3 fish are used in the assessment then the Prey Fish Water Quality Objective must also be used to determine that the Sport Fish Objective is being met. Trophic levels of applicable fish are defined in, but not limited to those in Attachment C of the Final Regulatory Language document (Appendix A) of State Water Resources Control Board Resolution No. 2017-0027.

Guideline Reference:

Inland Surface Waters, Enclosed Bays, and Estuaries Plan. Part 1: Trash Provisions; Part 2: Tribal Subsistence Beneficial Uses and Mercury Provisions; Part 3: Bacteria Provisions and Variance Policy

Spatial Representation:

Data was collected from 1 station(s) with the station code(s): 544LILPSL.

Temporal Representation:

Data for this line of evidence were collected between 2016-08-23 and 2016-08-23. When composited fish were collected over multiple days, the first day of fish collection was used as the sample date in the LOE, both for LOE writing, and for averaging period purposes.

Environmental Conditions:

QAPP Information:

San Francisco Estuary Institute (SFEI). 2016. Delta Regional Monitoring Program Quality Assurance Program Plan (Delta RMP QAPP 2016) .

QAPP Information Reference(s):

Delta Regional Monitoring Program Quality Assurance Program Plan (Delta RMP QAPP 2016)

Line of Evidence (LOE) for Decision ID 131247, Mercury	Region 5
Little Potato Slough (in Delta Waterways, central portion)

LOE ID:

223333

Pollutant:

Mercury

LOE Subgroup:

Pollutant-Tissue

Matrix:

Tissue

Fraction:

Fish fillet

Beneficial Use:

Commercial or recreational collection of fish, shellfish, or organisms

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

Tissue, Water data for the 2020/2022 integrated report in Region 5.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the California Regional Water Quality Control Board Central Valley Region, Sacramento and San Joaquin River Basins. 4th ed

Evaluation Guideline:

The Statewide Sport Fish Water Quality Objective for the protection of the Commercial and Sport Fishing beneficial comes from the Statewide Water Quality Control Plan for Inland Surface Waters, Enclosed Bays, and Estuaries of California, and is 0.2 mg/Kg wet weight skinless fillet samples of trophic level 3, or trophic level 4 fish (whichever is highest in the water body) over a one year averaging period. Trophic levels of applicable fish are defined in, but not limited to those in Attachment C of the Final Regulatory Language document (Appendix A) of State Water Resources Control Board Resolution No. 2017-0027.

Guideline Reference:

Inland Surface Waters, Enclosed Bays, and Estuaries Plan. Part 1: Trash Provisions; Part 2: Tribal Subsistence Beneficial Uses and Mercury Provisions; Part 3: Bacteria Provisions and Variance Policy

Spatial Representation:

Data was collected from 1 station(s) with the station code(s): 544LILPSL.

Temporal Representation:

Environmental Conditions:

QAPP Information:

San Francisco Estuary Institute (SFEI). 2016. Delta Regional Monitoring Program Quality Assurance Program Plan (Delta RMP QAPP 2016) .

QAPP Information Reference(s):

Delta Regional Monitoring Program Quality Assurance Program Plan (Delta RMP QAPP 2016)

Line of Evidence (LOE) for Decision ID 131247, Mercury	Region 5
Little Potato Slough (in Delta Waterways, central portion)

LOE ID:

191166

Pollutant:

Mercury

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

Tissue, Water data for the 2020/2022 integrated report in Region 5.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The mercury criteria for the protection of human health from the consumption of water and organisms is 0.050 ug/L (California Toxics Rule, 2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site (544LILPSL)

Temporal Representation:

The samples were collected between the dates of 2016-08-22 and 2017-04-25

Environmental Conditions:

QAPP Information:

San Francisco Estuary Institute (SFEI). 2016. Delta Regional Monitoring Program Quality Assurance Program Plan (Delta RMP QAPP 2016) .

QAPP Information Reference(s):

Delta Regional Monitoring Program Quality Assurance Program Plan (Delta RMP QAPP 2016)


DECISION ID	156835	Region 5
Little Potato Slough (in Delta Waterways, central portion)

Pollutant:	Nitrate/Nitrite (Nitrite + Nitrate as N)
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 decision was developed as part of the Sacramento-San Joaquin Delta remapping project. Data has been reassessed and decisions revised due to their spatial representation. This pollutant is being considered for placement on the CWA section 303(d) List under section 3.1 of the Listing Policy. Zero samples exceeded the objectives, guidelines, or criteria for beneficial uses applicable to this water segment-pollutant combination, which is less than the minimum number of exceedances needed to place the water segment on the section CWA section 303(d) List for toxicants (Table 3.1 of the Listing Policy). The data used satisfies the data quality requirements (section 6.1.4) and data quantity requirements (section 6.1.5) of the Listing Policy. Pursuant to section 3.11 of the Listing Policy, no additional data and information are available indicating that standards are not met. 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.

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:

Line of Evidence (LOE) for Decision ID 156835, Nitrate/Nitrite (Nitrite + Nitrate as N)	Region 5
Little Potato Slough (in Delta Waterways, central portion)

LOE ID:

321455

Pollutant:

Nitrate/Nitrite (Nitrite + Nitrate as N)

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

189

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

None of samples collected at the sampling locations exceeded the objective for nitrate + nitrite (as N).

Data Reference:

Data for Nutrients in Region 5, Jan. 1975 - Jan. 2007.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Water Quality Control Plan, Central Valley Region Sacramento River Basin and San Joaquin River Basin: At a minimum, water designated for MUN shall not contain concentrations of chemical constituents in excess of the MCL specified in Title 22 of the California Code of Regulations. The MCL for nitrate + nitrite (as N) is 10 mg/L.

Objective/Criterion Reference:

Water Quality Control Plan for the California Regional Water Quality Control Board Central Valley Region, Sacramento and San Joaquin River Basins. 4th ed

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

Samples were collected at stations: MD7A, Little Potato Slough @ Terminous

Temporal Representation:

Samples were collected from 1975 to 2007.

Environmental Conditions:

QAPP Information:

Samples were collected as part of a long term monitoring of water quality. No other description of the study were provided. A modified method comparable to other standard methods was used to measure results from 1996 to 2004.

QAPP Information Reference(s):


DECISION ID	73877	Region 5
Little Potato Slough (in Delta Waterways, central portion)

Pollutant:	Toxicity
Final Listing Decision:	List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	List on 303(d) list (TMDL required list)(2016)
Revision Status	Original
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 and 3.6 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. Three of twelve water samples exhibited significant toxicity. The toxicity tests included survival of Ceriodaphnia dubia, total cell count of Selenastrum capricornutum and survival of Pimephales promelas. Zero of one sediment sample tested with Hyalella azteca exhibited significant toxicity. 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 twelve water samples exhibited significant toxicity 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.

Line of Evidence (LOE) for Decision ID 73877, Toxicity	Region 5
Little Potato Slough (in Delta Waterways, central portion)

LOE ID:

59302

Pollutant:

Toxicity

LOE Subgroup:

Toxicity

Matrix:

Sediment

Fraction:

None

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

TOXICITY TESTING

Data Used to Assess Water Quality:

One sample was collected to evaluate sediment toxicity. The sample did not exhibit significant toxicity. The toxicity tests included survival of Hyalella azteca. One sample can have multiple toxicity test results but will be counted only once. One sample is defined as being collected on the same day at the same location with the same lab sample id (if provided).

Data Reference:

Data for Various Pollutants in Sacramento Valley Water Quality Coalition, 2005-2009.

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. Region 5 Basin Plan.

Objective/Criterion Reference:

Water Quality Control Plan for the California Regional Water Quality Control Board Central Valley Region, Sacramento and San Joaquin River Basins. 4th ed

Evaluation Guideline:

Toxicity is defined as a statistically significant effect in the sample exposure compared to the control using EPA-recommended hypothesis testing. For SWAMP data exceedances are counted using the significant effect code: S equals significant, SG equals significantly greater and SL equals significantly lower. If a sample has any one of these codes, it will be considered an exceedance.

Guideline Reference:

Methods for Measuring the Toxicity and Bioaccumulation of Sediment-associated Contaminants with Freshwater Invertebrates, Second Edition. U.S. Environmental Protection Agency Office of Research and Development, Duluth, MI , U.S. Environmental Protection Agency Office of Water, Washington, DC EPA-600/R-99/064

Spatial Representation:

The sample was collected at Potato Slough at Hwy 12.

Temporal Representation:

The sample was collected in September 2004.

Environmental Conditions:

QAPP Information:

Quality Assurance Project Plan For Monitoring By The San Joaquin County & Delta Water Quality Coalition.

QAPP Information Reference(s):

Quality Assurance Project Plan for Sacramento Valley Water Quality Coalition.

Line of Evidence (LOE) for Decision ID 73877, Toxicity	Region 5
Little Potato Slough (in Delta Waterways, central portion)

LOE ID:

59301

Pollutant:

Toxicity

LOE Subgroup:

Toxicity

Matrix:

Water

Fraction:

None

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

TOXICITY TESTING

Data Used to Assess Water Quality:

Twelve samples were collected to evaluate water toxicity. Three of the samples exhibited significant toxicity. The toxicity tests included survival of Ceriodaphnia dubia, total cell count of Selenastrum capricornutum and survival of Pimephales promelas. One sample can have multiple toxicity test results but will be counted only once. One sample is defined as being collected on the same day at the same location with the same lab sample id (if provided).

Data Reference:

Data for Various Pollutants in San Joaquin and Delta Water Quality Coalition, 2004-2010.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the California Regional Water Quality Control Board Central Valley Region, Sacramento and San Joaquin River Basins. 4th ed

Evaluation Guideline:

Toxicity is defined as a statistically significant effect in the sample exposure compared to the control using EPA-recommended hypothesis testing. For SWAMP data exceedances are counted with the significant effect code SL. SL is defined as the result being significant compared to the negative control based on a statistical test, less than stated the alpha level, AND less than the evaluation threshold. This data set reports a simple pass/fail (Yes/No) code to report toxicity that is equivalent to the SWAMP SL code.

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 Potato Slough at Hwy 12.

Temporal Representation:

The samples were collected from August 2004 to March 2006.

Environmental Conditions:

QAPP Information:

Quality Assurance Project Plan For Monitoring By The San Joaquin County & Delta Water Quality Coalition.

QAPP Information Reference(s):