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

Supporting Information

Regional Board 5 - Central Valley Region

Water Body Name:	Mosher Slough (downstream of I-5; in Delta Waterways, eastern portion)
Water Body ID:	CAR5312000019990127153844
Water Body Type:	River & Stream


DECISION ID	131378	Region 5
Mosher Slough (downstream of I-5; in Delta Waterways, eastern portion)

Pollutant:	Chlorpyrifos
Final Listing Decision:	Delist from 303(d) list (being addressed by USEPA approved TMDL)
Last Listing Cycle's Final Listing Decision:	Do Not Delist from 303(d) list (being addressed with USEPA approved TMDL)(2018)
Revision Status	Revised
Reason for Delisting:	Applicable WQS attained; reason for recovery unspecified
TMDL Name:	Delta Diazinon and Chlorpyrifos Project
TMDL Project Code:	185
Date TMDL Approved by USEPA:	10/10/2007
Impairment from Pollutant or Pollution:	Pollutant

Regional Board Conclusion:	This pollutant is being considered for removal from the CWA section 303(d) List under section 4.11 of the Listing Policy. Under this section when all other delisting factors do not result in the delisting of a water segment but information indicates attainment of standards, a water segment shall be evaluated to determine whether the weight of evidence demonstrates that water quality standard is attained. If the weight of evidence indicates attainment, the water segment shall be removed from the CWA section 303(d) List. One line of evidence was used in this assessment. LOE 2682, 23108, 23124, and 23125 were not considered in this assessment as those data were collected prior to the approval of a TMDL and thus are no longer considered representative of conditions in the water body. Based on the readily available data and information, the weight of evidence indicates that there is sufficient justification for 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. Data collected prior to the USEPA approval of a TMDL in October of 2007 was not considered as part of this assessment in accordance with Section 6.1.5.3 of the Listing Policy. 3. The following information indicates that the water quality standard is attained: zero of 37 samples collected after approval of a TMDL exceed the objective for WARM. This is sufficient to determine beneficial use support according to the Listing Policy. 3. This process is scientifically defensible and reproducible.

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 131378, Chlorpyrifos	Region 5
Mosher Slough (downstream of I-5; in Delta Waterways, eastern portion)

LOE ID:

23124

Pollutant:

Chlorpyrifos

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Warm Freshwater Habitat

Aquatic Life Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

19 water samples were collected from Mosher Slough from January through April 2004, representing 13 4-day average concentrations and 19 1-hour average concentrations.5 of 13 4-day average concentrations exceeded the 4-day maximum concentration guideline of 0.015 ug/L.6 of 19 1-hour average concentrations exceeded the maximum 1-hour chlorpyrifos concentration of 0.025 ug/L.

Data Reference:

Zipped file of Central Valley Waterways Pesticide TMDL monitoring data spreadsheets and reports

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

No individual pesticide or combination of pesticides shall be present in concentrations that adversely affect beneficial uses (CVRWQCB, 2007).All waters shall be maintained free of toxic substances in concentrations that produce detrimental physiological responses in human, plant, animal, or aquatic life (CVRWQCB, 2007).

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:

California Department of Fish and Game Hazard Assessment Criteria - 0.015 ug/L 4-day average and 0.025 ug/L 1-hour average (Siepmann and Finlayson, 2000, with minor corrections to significant figures as described in Beaulaurier et al., 2005).

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 from Mosher Slough at Mariners Drive.

Temporal Representation:

Samples were collected daily during two storm events in February 2004 and weekly between March and April 2004.

Environmental Conditions:

QAPP Information:

Data quality: Good. Calanchini, H. 2006. Quality Assurance Project Plan, Sacramento and San Joaquin River Basins and Sacramento-San Joaquin Delta TMDL Monitoring for Organophosphorus Pesticides and Other Pesticides Identified as Posing a High Risk to Surface Waters. John Muir Institute of the Environment, U.C. Davis. Davis, CA.

QAPP Information Reference(s):

Quality Assurance Project Plan. Sacramento and San Joaquin River Basins and Sacramento-San Joaquin Delta TMDL Monitoring for Organophosphorus Pesticides and Other Pesticides Identified as Posing a High Risk to Surface Waters. Final. SWAMP Project ID 02TM5001 (Revision 0.0). John Muir Institute of the Environment, U.C. Davis. Davis, CA. January 26, 2006

Line of Evidence (LOE) for Decision ID 131378, Chlorpyrifos	Region 5
Mosher Slough (downstream of I-5; in Delta Waterways, eastern portion)

LOE ID:

2682

Pollutant:

Chlorpyrifos

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Not Recorded

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

Not Specified

Data Used to Assess Water Quality:

Unspecified--This LOE is a placeholder to support a 303(d) listing decision made prior to 2006.

Data Reference:

Placeholder reference 2006 303(d)

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

Temporal Representation:

Environmental Conditions:

QAPP Information:

QA Info Missing

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 131378, Chlorpyrifos	Region 5
Mosher Slough (downstream of I-5; in Delta Waterways, eastern portion)

LOE ID:

23108

Pollutant:

Chlorpyrifos

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Warm Freshwater Habitat

Aquatic Life Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

28 water samples were collected from Mosher Slough from June 2002 through May 2003, representing 20 4-day average concentrations and 28 1-hour average concentrations.4 of 20 available 4-day average concentrations exceeded the 4-day maximum concentration guideline of 0.015 ug/L.3 of 28 1-hour average concentrations exceeded the maximum 1-hour chlorpyrifos concentration of 0.025 ug/L.

Data Reference:

Zipped file of Central Valley Waterways Pesticide TMDL monitoring data spreadsheets and reports

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

Objective/Criterion 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

Evaluation Guideline:

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 from Mosher Slough at Mariners Drive.

Temporal Representation:

Samples were collected daily in two storm events in January and February 2003, and at variable intervals (4 days, weekly and monthly) between June 2002 and May 2003.

Environmental Conditions:

QAPP Information:

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 131378, Chlorpyrifos	Region 5
Mosher Slough (downstream of I-5; in Delta Waterways, eastern portion)

LOE ID:

231389

Pollutant:

Chlorpyrifos

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:

Water Board staff assessed data collected by the City of Stockton and County of San Joaquin for the Mosher Slough to determine beneficial use support and results are as follows: 0 of 37 samples exceeded the water quality threshold for chlorpyrifos. One sample was not considered because the method detection limit for the analysis exceeded the water quality threshold. Data collected prior to the USEPA approval of a TMDL in October of 2007 was not considered.

Data Reference:

Receiving water data for diazinon and chlorpyrifos, 1997-2016

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The freshwater criterion continuous concentration for chlorpyrifos to protect aquatic organisms is 0.015 ug/L (4 day average)

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:

Guideline Reference:

Spatial Representation:

Data was collected at one site: Mosher Slough at Mariners Drive (MS-14R)

Temporal Representation:

Data were collected between 1/4/08 and 5/24/16.

Environmental Conditions:

QAPP Information:

This data was collected after QAPP requirements were developed, but exempt from the requirements.

QAPP Information Reference(s):

This is a placeholder reference for data that was collected after QAPP requirements were developed, but exempt from the requirements.

Line of Evidence (LOE) for Decision ID 131378, Chlorpyrifos	Region 5
Mosher Slough (downstream of I-5; in Delta Waterways, eastern portion)

LOE ID:

23125

Pollutant:

Chlorpyrifos

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Warm Freshwater Habitat

Aquatic Life Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

5 water samples were collected from Mosher Slough in February 2005, representing 2 4-day average concentrations and 5 1-hour average concentrations.1 of 2 4-day average concentrations exceeded the 4-day maximum concentration guideline of 0.015 ug/L.1 of 5 1-hour average concentrations exceeded the maximum 1-hour chlorpyrifos concentration of 0.025 ug/L.

Data Reference:

Zipped file of Central Valley Waterways Pesticide TMDL monitoring data spreadsheets and reports

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:

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 from Mosher Slough at Mariners Drive.

Temporal Representation:

Samples were collected daily during one storm event in February 2005.

Environmental Conditions:

QAPP Information:

QAPP Information Reference(s):


DECISION ID	131379	Region 5
Mosher Slough (downstream of I-5; in Delta Waterways, eastern portion)

Pollutant:	Diazinon
Final Listing Decision:	Delist from 303(d) list (being addressed by USEPA approved TMDL)
Last Listing Cycle's Final Listing Decision:	Do Not Delist from 303(d) list (being addressed with USEPA approved TMDL)(2018)
Revision Status	Revised
Reason for Delisting:	Applicable WQS attained; reason for recovery unspecified
TMDL Name:	Delta Diazinon and Chlorpyrifos Project
TMDL Project Code:	185
Date TMDL Approved by USEPA:	10/10/2007
Impairment from Pollutant or Pollution:	Pollutant

Regional Board Conclusion:	This pollutant is being considered for removal from the CWA section 303(d) List under section 4.11 of the Listing Policy. Under this section when all other delisting factors do not result in the delisting of a water segment but information indicates attainment of standards, a water segment shall be evaluated to determine whether the weight of evidence demonstrates that water quality standard is attained. If the weight of evidence indicates attainment, the water segment shall be removed from the CWA section 303(d) List. One line of evidence was used in this assessment. LOE 2683, 23126, 23127, and 23141 were not considered in this assessment as those data were collected prior to the approval of a TMDL and thus are no longer considered representative of conditions in the water body. Based on the readily available data and information, the weight of evidence indicates that there is sufficient justification for 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. Data collected prior to the USEPA approval of a TMDL in October of 2007 was not considered as part of this assessment in accordance with Section 6.1.5.3 of the Listing Policy. 3. The following information indicates that the water quality standard is attained: zero of 29 samples collected after approval of a TMDL exceed the objective for WARM. This is sufficient to determine beneficial use support according to the Listing Policy. 3. This process is scientifically defensible and reproducible.

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 131379, Diazinon	Region 5
Mosher Slough (downstream of I-5; in Delta Waterways, eastern portion)

LOE ID:

231390

Pollutant:

Diazinon

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:

Water Board staff assessed data collected by the City of Stockton and County of San Joaquin for the Mosher Slough to determine beneficial use support and results are as follows: 0 of 29 samples exceeded the water quality threshold for diazinon. One sample was not considered because the method detection limit for the analysis exceeded the water quality threshold. Data collected prior to the USEPA approval of a TMDL in October of 2007 was not considered.

Data Reference:

Receiving water data for diazinon and chlorpyrifos, 1997-2016

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The freshwater criterion continuous concentration for diazinon to protect aquatic organisms is 0.1 ug/L (4 day average)

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

Data was collected at one site: Mosher Slough at Mariners Drive (MS-14R)

Temporal Representation:

Data were collected between 1/4/08 and 5/29/15.

Environmental Conditions:

QAPP Information:

This data was collected after QAPP requirements were developed, but exempt from the requirements.

QAPP Information Reference(s):

This is a placeholder reference for data that was collected after QAPP requirements were developed, but exempt from the requirements.

Line of Evidence (LOE) for Decision ID 131379, Diazinon	Region 5
Mosher Slough (downstream of I-5; in Delta Waterways, eastern portion)

LOE ID:

23126

Pollutant:

Diazinon

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Warm Freshwater Habitat

Aquatic Life Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

28 water samples were collected from Mosher Slough from June 2002 through May 2003, representing 20 4-day average concentrations and 28 1-hour average concentrations.8 of 20 four-day average concentrations exceeded the four day maximum concentration guideline of 0.10 ug/L.3 of 28 one-hour average concentrations exceeded the maximum 1-hour concentration of 0.16 ug/L.

Data Reference:

Zipped file of Central Valley Waterways Pesticide TMDL monitoring data spreadsheets and reports

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

No individual pesticide or combination of pesticides shall be present in concentrations that adversely affect beneficial uses (CVRWQCB, 2007). All waters shall be maintained free of toxic substances in concentrations that produce detrimental physiological responses in human, plant, animal, or aquatic life (CVRWQCB, 2007).

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

Objective/Criterion 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

Evaluation Guideline:

California Fish and Game Hazard Assessment Criteria - 0.160 ug/L 1-hour average and 0.100 ug/L 4-day average concentration not to be exceeded more than once every three years (Siepmann and Finlayson, 2000 and Finlayson, 2004).

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 from Five Mosher Slough at Mariners Drive.

Temporal Representation:

Samples were collected daily during two storms in January and February 2003, and at variable intervals (biweekly, weekly, monthly) from June 2002 through February 2003.

Environmental Conditions:

QAPP Information:

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 131379, Diazinon	Region 5
Mosher Slough (downstream of I-5; in Delta Waterways, eastern portion)

LOE ID:

23127

Pollutant:

Diazinon

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Warm Freshwater Habitat

Aquatic Life Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

19 water samples were collected from Mosher Slough from January to April 2004, representing 13 4-day average concentrations and 19 1-hour average concentrations.4 of 13 four-day average concentrations exceeded the four day maximum concentration guideline of 0.100 ug/L.6 of 19 one-hour average concentrations exceeded the maximum 1-hour concentration of 0.160 ug/L.

Data Reference:

Zipped file of Central Valley Waterways Pesticide TMDL monitoring data spreadsheets and reports

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

No individual pesticide or combination of pesticides shall be present in concentrations that adversely affect beneficial uses. (CVRWQCB, 2007) All waters shall be maintained free of toxic substances in concentrations that produce detrimental physiological responses in human, plant, animal, or aquatic life. (CVRWQCB, 2007)

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

Objective/Criterion 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

Evaluation Guideline:

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 collected from Mosher Slough at Mariners Drive.

Temporal Representation:

Samples were collected at daily intervals during two storm events in January and February 2004, and weekly in March and April 2004.

Environmental Conditions:

QAPP Information:

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 131379, Diazinon	Region 5
Mosher Slough (downstream of I-5; in Delta Waterways, eastern portion)

LOE ID:

2683

Pollutant:

Diazinon

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Not Recorded

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

Not Specified

Data Used to Assess Water Quality:

Unspecified--This LOE is a placeholder to support a 303(d) listing decision made prior to 2006.

Data Reference:

Placeholder reference 2006 303(d)

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

Temporal Representation:

Environmental Conditions:

QAPP Information:

QA Info Missing

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 131379, Diazinon	Region 5
Mosher Slough (downstream of I-5; in Delta Waterways, eastern portion)

LOE ID:

23141

Pollutant:

Diazinon

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Warm Freshwater Habitat

Aquatic Life Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

5 water samples were collected from Mosher Slough in February 2005, representing 2 4-day average concentrations and 5 1-hour average concentrations.0 of 2 four-day average concentrations exceeded the four day maximum concentration guideline of 0.10 ug/L.0 of 5 one-hour average concentrations exceeded the maximum 1-hour concentration of 0.16 ug/L.

Data Reference:

Zipped file of Central Valley Waterways Pesticide TMDL monitoring data spreadsheets and reports

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:

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 collected from Mosher Slough at Mariners Drive.

Temporal Representation:

Samples were collected at daily intervals during one storm event in February 2005.

Environmental Conditions:

QAPP Information:

Data quality: Excellent. Calanchini, H. 2006. Quality Assurance Project Plan, Sacramento and San Joaquin River Basins and Sacramento-San Joaquin Delta TMDL Monitoring for Organophosphorus Pesticides and Other Pesticides Identified as Posing a High Risk to Surface Waters. John Muir Institute of the Environment, U.C. Davis. Davis, CA.

QAPP Information Reference(s):


DECISION ID	71786	Region 5
Mosher Slough (downstream of I-5; in Delta Waterways, eastern portion)

Pollutant:	Organic Enrichment/Low Dissolved Oxygen
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)(2016)
Revision Status	Original
Sources:	A Source Unknown
Expected TMDL Completion Date:	2027
Impairment from Pollutant or Pollution:	Pollutant

Regional Board Conclusion:	The decision has not changed. No new Region 5 data were assessed for 2014. The Regional Boards will update this decision when new data and information become available and are assessed.

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 71786, Organic Enrichment/Low Dissolved Oxygen	Region 5
Mosher Slough (downstream of I-5; in Delta Waterways, eastern portion)

LOE ID:

4485

Pollutant:

Organic Enrichment/Low Dissolved Oxygen

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Not Recorded

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

Not Specified

Data Used to Assess Water Quality:

Unspecified--This LOE is a placeholder to support a 303(d) listing decision made prior to 2006.

Data Reference:

Placeholder reference pre-2006 303(d)

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Unspecified

Objective/Criterion Reference:

Placeholder reference pre-2006 303(d)

Evaluation Guideline:

Unspecified

Guideline Reference:

Placeholder reference pre-2006 303(d)

Spatial Representation:

Unspecified

Temporal Representation:

Unspecified

Environmental Conditions:

Unspecified

QAPP Information:

Unspecified

QAPP Information Reference(s):


DECISION ID	73460	Region 5
Mosher Slough (downstream of I-5; in Delta Waterways, eastern portion)

Pollutant:	Azinphos-methyl (Guthion)
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)(2016)
Revision Status	Original
Impairment from Pollutant or Pollution:	Pollutant

Regional Board Conclusion:	This pollutant is being considered for placement on the section 303(d) list under section 3.1 of the Listing Policy. Under section 3.1 a single line of evidence is necessary to assess listing status. Three lines of evidence are available in the administrative record to assess this pollutant. Two of the samples exceed the water quality 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 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. Two of 58 samples exceeded the water quality criterion 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:	This is a decision previously approved by the State Water Resources Control Board and the USEPA. No new data were assessed by the Regional Board for the current cycle. The decision has not changed.

State Board Review of Regional Board Conclusion and Recommendation:

State Board Decision Recommendation:	After review of this Regional Board decision, SWRCB staff recommend the decision be approved by the State Board.

Line of Evidence (LOE) for Decision ID 73460, Azinphos-methyl (Guthion)	Region 5
Mosher Slough (downstream of I-5; in Delta Waterways, eastern portion)

LOE ID:

23107

Pollutant:

Azinphos-methyl (Guthion)

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Warm Freshwater Habitat

Aquatic Life Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

11 water samples were collected from Mosher Slough from February through April 2005, representing 11 concentrations.1 of 11 available concentrations exceeded the water quality criterion (0.01 ug/L).

Data Reference:

Zipped file of Central Valley Waterways Pesticide TMDL monitoring data spreadsheets and reports

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

Objective/Criterion Reference:

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

Evaluation Guideline:

Water quality criterion is 0.01 ug/L for freshwater and marine aquatic life in the U.S. Environmental Protection Agency, Quality Criteria for Water [The Red Book] (USEPA, 1976). http://www.epa.gov/waterscience/criteria/redbook.pdf

Guideline Reference:

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

Spatial Representation:

Samples were collected from Mosher Slough at Mariners Drive.

Temporal Representation:

Samples were collected daily during one storm event in February 2005, and weekly in March 2005.

Environmental Conditions:

QAPP Information:

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 73460, Azinphos-methyl (Guthion)	Region 5
Mosher Slough (downstream of I-5; in Delta Waterways, eastern portion)

LOE ID:

23106

Pollutant:

Azinphos-methyl (Guthion)

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Warm Freshwater Habitat

Aquatic Life Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

19 water samples were collected from Mosher Slough from February to April 2004, representing 19 concentrations.0 of 19 available concentrations exceeded the water quality criterion (0.01 ug/L).

Data Reference:

Zipped file of Central Valley Waterways Pesticide TMDL monitoring data spreadsheets and reports

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

Objective/Criterion Reference:

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

Evaluation Guideline:

Guideline Reference:

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

Spatial Representation:

Samples were collected from Mosher Slough at Mariners Drive.

Temporal Representation:

Samples were collected daily during two storm events in February 2004 and weekly between March and April 2004.

Environmental Conditions:

QAPP Information:

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 73460, Azinphos-methyl (Guthion)	Region 5
Mosher Slough (downstream of I-5; in Delta Waterways, eastern portion)

LOE ID:

23105

Pollutant:

Azinphos-methyl (Guthion)

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Warm Freshwater Habitat

Aquatic Life Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

28 water samples were collected from Mosher Slough from June 2002 through May 2003, representing 28 concentrations.1 of 28 available concentrations exceeded the water quality criterion (0.01 ug/L).

Data Reference:

Zipped file of Central Valley Waterways Pesticide TMDL monitoring data spreadsheets and reports

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

Objective/Criterion Reference:

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

Evaluation Guideline:

Guideline Reference:

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

Spatial Representation:

Samples were collected from Mosher Slough at Mariners Drive.

Temporal Representation:

Samples were collected daily in two storm events in January and February 2003, and at variable intervals (4 days, weekly and monthly) between June 2002 and May 2003.

Environmental Conditions:

QAPP Information:

QAPP Information Reference(s):


DECISION ID	74611	Region 5
Mosher Slough (downstream of I-5; in Delta Waterways, eastern portion)

Pollutant:	Simazine
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)(2016)
Revision Status	Original
Impairment from Pollutant or Pollution:	Pollutant

Regional Board Conclusion:	This pollutant is being considered for placement on the section 303(d) list under section 3.1 of the Listing Policy. Under section 3.1 a single line of evidence is necessary to assess listing status. Three lines of evidence are available in the administrative record to assess this pollutant. One of the samples exceed the water quality 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 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. One of 59 samples exceeded the drinking water standard (4 µg/L) 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:	This is a decision previously approved by the State Water Resources Control Board and the USEPA. No new data were assessed by the Regional Board for the current cycle. The decision has not changed.

State Board Review of Regional Board Conclusion and Recommendation:

State Board Decision Recommendation:	After review of this Regional Board decision, SWRCB staff recommend the decision be approved by the State Board.

Line of Evidence (LOE) for Decision ID 74611, Simazine	Region 5
Mosher Slough (downstream of I-5; in Delta Waterways, eastern portion)

LOE ID:

23089

Pollutant:

Simazine

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:

11 water samples were collected from Mosher Slough from February and April 2005, representing 11 concentrations.0 of 11 concentrations exceeded the MCL (4 ug/L).

Data Reference:

Zipped file of Central Valley Waterways Pesticide TMDL monitoring data spreadsheets and reports

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

At a minimum, water designated for use as domestic or municipal supply (MUN) shall not contain concentrations of chemical constituents in excess of the maximum contaminant levels (MCLs) specified in the following provisions of Title 22 of the California Code of Regulations, which are incorporated by reference into this plan: Tables 64431-A (Inorganic Chemicals) and 64431-B (Fluoride) of Section 64431, Table 64444-A (Organic Chemicals) of Section 64444, and Tables 64449-A (Secondary Maximum Contaminant Levels-Consumer Acceptance Limits) and 64449-B (Secondary Maximum Contaminant Levels-Ranges) of Section 64449.

The Maximum Contaminant Level (MCL) for simazine is 4 ug/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

Objective/Criterion Reference:

California Code of Regulations, Title 22, Division 4, Chapter 15. Domestic Water Quality and Monitoring

Evaluation Guideline:

Guideline Reference:

California Code of Regulations, Title 22, Division 4, Chapter 15. Domestic Water Quality and Monitoring

Spatial Representation:

Samples were collected from Mosher Slough at Mariners Drive.

Temporal Representation:

Samples were collected daily during one storm event in February 2005 and biweekly between March and April 2005.

Environmental Conditions:

QAPP Information:

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 74611, Simazine	Region 5
Mosher Slough (downstream of I-5; in Delta Waterways, eastern portion)

LOE ID:

23087

Pollutant:

Simazine

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:

28 water samples were collected from Mosher Slough from June 2002 through May 2003, representing 28 concentrations.0 of 28 available concentrations exceeded MCL (4 ug/L).

Data Reference:

Zipped file of Central Valley Waterways Pesticide TMDL monitoring data spreadsheets and reports

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

Objective/Criterion Reference:

California Code of Regulations, Title 22, Division 4, Chapter 15. Domestic Water Quality and Monitoring

Evaluation Guideline:

Guideline Reference:

California Code of Regulations, Title 22, Division 4, Chapter 15. Domestic Water Quality and Monitoring

Spatial Representation:

Samples were collected from Mosher Slough at Mariners Drive.

Temporal Representation:

Samples were collected daily in two storm events in January and February 2003, and at variable intervals (4 days, weekly and monthly) between June 2002 and May 2003.

Environmental Conditions:

QAPP Information:

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 74611, Simazine	Region 5
Mosher Slough (downstream of I-5; in Delta Waterways, eastern portion)

LOE ID:

23088

Pollutant:

Simazine

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:

20 water samples were collected from Mosher Slough from January through April 2004, representing 20 concentrations.1 of 20 available concentrations exceeded MCL (4 ug/L).

Data Reference:

Zipped file of Central Valley Waterways Pesticide TMDL monitoring data spreadsheets and reports

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

Objective/Criterion Reference:

California Code of Regulations, Title 22, Division 4, Chapter 15. Domestic Water Quality and Monitoring

Evaluation Guideline:

Guideline Reference:

California Code of Regulations, Title 22, Division 4, Chapter 15. Domestic Water Quality and Monitoring

Spatial Representation:

Samples were collected from Mosher Slough at Mariners Drive.

Temporal Representation:

Samples were collected daily during two storm events in February 2004 and weekly between March and April 2004.

Environmental Conditions:

QAPP Information:

QAPP Information Reference(s):


DECISION ID	77640	Region 5
Mosher Slough (downstream of I-5; in Delta Waterways, eastern portion)

Pollutant:	Indicator Bacteria
Final Listing Decision:	List on 303(d) list (being addressed by USEPA approved TMDL)
Last Listing Cycle's Final Listing Decision:	List on 303(d) list (being addressed by USEPA approved TMDL)(2016)
Revision Status	Original
Sources:	A Source Unknown
TMDL Name:	Stockton Area Sloughs and Rivers - Pathogens
TMDL Project Code:	721
Date TMDL Approved by USEPA:	05/13/2008
Impairment from Pollutant or Pollution:	Pollutant

Regional Board Conclusion:	The decision has not changed. No new Region 5 data were assessed for 2014. The Regional Boards will update this decision when new data and information become available and are assessed.

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 77640, Indicator Bacteria	Region 5
Mosher Slough (downstream of I-5; in Delta Waterways, eastern portion)

LOE ID:

4486

Pollutant:

Pathogens

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Not Recorded

Beneficial Use:

Water Contact Recreation

Number of Samples:

Number of Exceedances:

Data and Information Type:

Not Specified

Data Used to Assess Water Quality:

Unspecified--This LOE is a placeholder to support a 303(d) listing decision made prior to 2006.

Data Reference:

Placeholder reference pre-2006 303(d)

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Unspecified

Objective/Criterion Reference:

Placeholder reference pre-2006 303(d)

Evaluation Guideline:

Unspecified

Guideline Reference:

Placeholder reference pre-2006 303(d)

Spatial Representation:

Unspecified

Temporal Representation:

Unspecified

Environmental Conditions:

Unspecified

QAPP Information:

Unspecified

QAPP Information Reference(s):


DECISION ID	75781	Region 5
Mosher Slough (downstream of I-5; in Delta Waterways, eastern portion)

Pollutant:	Mercury
Final Listing Decision:	List on 303(d) list (being addressed by USEPA approved TMDL)
Last Listing Cycle's Final Listing Decision:	List on 303(d) list (being addressed by USEPA approved TMDL)(2016)
Revision Status	Original
Sources:	Agricultural Return Flows \| Atmospheric Deposition \| Highway/Road/Bridge Runoff \| Industrial Point Sources \| Municipal Point Sources \| Natural Sources \| Resource Extraction \| See TMDL documentation \| Urban Runoff/Storm Sewers
TMDL Name:	Delta Methylmercury TMDL Project
TMDL Project Code:	128
Date TMDL Approved by USEPA:	10/20/2011
Impairment from Pollutant or Pollution:	Pollutant

Regional Board Conclusion:	This pollutant is being considered for placement on the section 303(d) list under section 3.1 of the Listing Policy. Under section 3.1 a single line of evidence is necessary to assess listing status. One line of evidence is available in the administrative record to assess this pollutant. Nine of the samples exceed the water quality objective. Based on the readily available data and information, the weight of evidence indicates that there is sufficient justification in favor of placing this water segment-pollutant combination on the 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. Nine of 14 water samples exceed the USEPA CTR criteria limit for total recoverable mercury of 50 ng/L based on human consumption of water and fish, 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:	This is a decision previously approved by the State Water Resources Control Board and the USEPA. No new data were assessed by the Regional Board for the current cycle. The USEPA approved the Delta methylmercury TMDL on 10/20/2011.

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 75781, Mercury	Region 5
Mosher Slough (downstream of I-5; in Delta Waterways, eastern portion)

LOE ID:

26129

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:

Nine of 14 water samples collected from Mosher Slough between April 2003 and June 2006 exceeded the CTR/USEPA criterion for total recoverable mercury of 50 ng/L.

Data Reference:

City of Stockton NPDES Municipal Stormwater Program Report of Waste Discharge

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The USEPA California Toxics Rule Criteria (CTR) Inland Surface Waters for the protection of human health for the consumption of both water and fish that live in the water is 50 ng/L (30-day average) for total recoverable mercury.

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:

Samples were collected from Mosher Slough at Mariners Drive.

Temporal Representation:

Samples were collected monthly, every two months, or every three months between April 2003 and June 2006.

Environmental Conditions:

QAPP Information:

Analysis done by labs with approved QAQC programs, in accordance with stormwater permit requirements.

QAPP Information Reference(s):