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

Supporting Information

Regional Board 5 - Central Valley Region

Water Body Name:	Calaveras River, Lower (from Stockton Diverting Canal to the Delta Waterways)
Water Body ID:	CAR5313000020221114032492
Water Body Type:	River & Stream


DECISION ID	160568	Region 5
Calaveras River, Lower (from Stockton Diverting Canal to the Delta Waterways)

Pollutant:	Chlorpyrifos
Final Listing Decision:	Delist from 303(d) list (being addressed by USEPA approved TMDL)
Last Listing Cycle's Final Listing Decision:	Delist from 303(d) list (being addressed by USEPA approved TMDL)(2024)
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 waterbody was split as part of the 2024 cycle Delta Remapping Project. Decisions were reassessed based on the new spatial representation, which resulted in a delisting. This pollutant is being considered for removal from the CWA section 303(d) List under section 4.1 of the Listing Policy. Under this section a single line of evidence is necessary to assess listing status. Five lines of evidence are available in the administrative record to assess this pollutant. Zero out of two samples exceed the evaluation guideline for COLD. Two of the 32 samples exceeded the evaluation guideline for WARM. 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. The data used satisfies the data quantity requirements of section 6.1.5 of the Policy. 3. Zero out of two samples exceed the evaluation guideline for COLD. Two of the 32 samples exceeded the evaluation guideline for WARM and this does not exceed the allowable frequency listed in Table 4.1 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 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:

Line of Evidence (LOE) for Decision ID 160568, Chlorpyrifos	Region 5
Calaveras River, Lower (from Stockton Diverting Canal to the Delta Waterways)

LOE ID:

309691

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:

One of sixteen water samples collected from the lower Calaveras River by the Central Valley Water Board, Pesticide TMDL program between June 2002 and September 2003, exceeded the 4-day average criterion of 0.015 ug/L. Zero of sixteen water samples exceeded the 1-hour average criterion of 0.025 ug/L. The water sample that exceeded the 4-day average criterion was collected on 18 March 2003.

Data Reference:

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

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

All waters shall be maintained free of toxic substances in concentrations that produce detrimental physiological responses in human, plant, animal, or aquatic life.

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 chlorpyrifos criteria for the protection of freshwater aquatic life: 0.015 ug/L (4-day average concentration), and 0.025 ug/L (1-hour average concentration), not to be exceeded more than once every three years.

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 the lower Calaveras River at Ijams Road.

Temporal Representation:

Seven water samples were collected approximately monthly from 18 June 2002 to18 February 2003, and 9 water samples were collected approximately weekly from 3 March 2003 to 19 May 2003.

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 160568, Chlorpyrifos	Region 5
Calaveras River, Lower (from Stockton Diverting Canal to the Delta Waterways)

LOE ID:

333132

Pollutant:

Chlorpyrifos

LOE Subgroup:

Pollutant-Sediment

Matrix:

Sediment

Fraction:

Total

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

Field, Habitat, Toxicity, WQ from the City of Stockton and San Joaquin County Stormwater Program receiving water monitoring for the 2026 Integrated Report in Region 5

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. Discharges shall not result in pesticide concentrations in bottom sediments or aquatic life that adversely affect beneficial uses. (Water Quality Control Plan, Central Valley Region, Sacramento River Basin 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:

The evaluation guideline for chlorpyrifos, 0.177 ug/g, is one-tenth of the median lethal concentration (LC50; 1.77 ug/g) and is normalized by the percentage of organic carbon in the sediment sample (Amweg and Weston, 2007).

Guideline Reference:

Whole-sediment toxicity identification evaluation tools for pyrethroid insecticides: I. piperonyl butoxide addition. Environ. Toxicol. Chem. 26:2389-2396.

Spatial Representation:

Data were collected from 1 station(s). Station Code(s): CR-46RPP (Calaveras River receiving water - Pathogen Plan CR-46RPP).

Temporal Representation:

Data for this waterbody were collected over the date range 2016-10-17 to 2017-06-01

Environmental Conditions:

QAPP Information:

Stockton NPDES QAPP - City of Stockton & San Joaquin Co. Rec Water Mont.

QAPP Information Reference(s):

SWRCB - Region5 - Stockton NPDES QAPP - City of Stockton & San Joaquin Co. Rec Water Mont. - 402686

Line of Evidence (LOE) for Decision ID 160568, Chlorpyrifos	Region 5
Calaveras River, Lower (from Stockton Diverting Canal to the Delta Waterways)

LOE ID:

309698

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:

Five water samples were collected from the lower Calaveras River, under the Central Valley Water Board's pesticide TMDL program, in March and April 2005, representing five calculated 4-day average concentrations and five 1-hour average concentrations. Zero of the five calculated 4-day average concentrations exceeded the 4-day average criterion of 0.100 ug/L. Zero of the five 1-hour average concentrations exceeded the 1-hour average criterion 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:

All waters shall be maintained free of toxic substances in concentrations that produce detrimental physiological responses in human, plant, animal, or aquatic life.

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 Fish and Game Hazard Assessment chlorpyrifos criteria for freshwater aquatic life protection: 0.025 ug/L (1-hour average) and 0.015 ug/L (4-day average) concentrations, not to be exceeded more than once every three years.

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:

Water samples were collected from the lower Calaveras River at Ijams Road.

Temporal Representation:

Samples were collected weekly between 2 March and 6 April 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):

Line of Evidence (LOE) for Decision ID 160568, Chlorpyrifos	Region 5
Calaveras River, Lower (from Stockton Diverting Canal to the Delta Waterways)

LOE ID:

309693

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:

Fifteen water samples were collected from the lower Calaveras River, under the Central Valley Water Board, Pesticide TMDL program, between February and April 2004. The fifteen water samples represent nine calculated 4-day average concentrations and fifteen 1-hour average concentrations. One of the nine calculated 4-day average concentrations exceeded the 4-day average criterion of 0.015 ug/L. Zero of the fifteen 1-hour average concentrations exceeded the 1-hour average criterion of 0.025 ug/L.

Data Reference:

Revised Draft of the 2007 Review of the Monitoring Data for the Irrigated Lands Regulatory Conditional Waiver Program

Monitoring and Reporting Program, Order Nos. R5-2003-0826, R5-2005-0833, and R5-2008-0005 for Coalition Groups Under Resolution No. R5-2003-0105, Conditional Waiver of Waste Discharge Requirements for Discharges From Irrigated Lands Within the Central Valley Region

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

All waters shall be maintained free of toxic substances in concentrations that produce detrimental physiological responses in human, plant, animal, or aquatic life.

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 chlorpyrifos criteria for freshwater aquatic life protection: 0.015 ug/L (4-day average concentration), and 0.025 ug/L (1-hour average concentration), not to be exceeded more than once every three years.

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:

Water samples were collected from the lower Calaveras River at Ijams Road.

Temporal Representation:

Samples were collected from the lower Calaveras River daily during two storm events (2 February to 6 February 2004 and 16 February to 20 February 2004), weekly in March, and once in early April 2004.

Environmental Conditions:

Water samples were collected during, and after, two storm events in February 2004.

QAPP Information:

Data quality: Good. Monitoring was conducted in accordance with Central Valley Water Board Monitoring and Reporting Program (order number R5-2003-0826) requirements.

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 160568, Chlorpyrifos	Region 5
Calaveras River, Lower (from Stockton Diverting Canal to the Delta Waterways)

LOE ID:

309692

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:

Five water samples were collected from the lower Calaveras River, under the Central Valley Regional Board's Pesticide TMDL program, daily between 15 February and 19 February 2005, representing two calculated 4-day average chlorpyrifos concentrations and five 1-hour average chlorpyrifos concentrations. Zero of the two calculated 4-day average chlorpyrifos concentrations exceeded the 4-day average chlorpyrifos criterion of 0.015 ug/L. Zero of the five 1-hour average chlorpyrifos concentrations exceeded the 1-hour average chlorpyrifos criterion 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:

All waters shall be maintained free of toxic substances in concentrations that produce detrimental physiological responses in human, plant, animal, or aquatic life.

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:

Water samples were collected from the lower Calaveras River at Ijams Road.

Temporal Representation:

Samples were collected daily during a storm event, between 15 February and 19 February 2005.

Environmental Conditions:

QAPP Information:

QAPP Information Reference(s):


DECISION ID	160569	Region 5
Calaveras River, Lower (from Stockton Diverting Canal to the Delta Waterways)

Pollutant:	Diazinon
Final Listing Decision:	Delist from 303(d) list (being addressed by USEPA approved TMDL)
Last Listing Cycle's Final Listing Decision:	Delist from 303(d) list (being addressed by USEPA approved TMDL)(2024)
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 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. Five lines of evidence are available in the administrative record to assess this pollutant. The four 2010 Cycle LOEs 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. Zero of one sediment samples exceed the guideline for COLD. 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 one sediment samples exceed the guideline for COLD 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:

Line of Evidence (LOE) for Decision ID 160569, Diazinon	Region 5
Calaveras River, Lower (from Stockton Diverting Canal to the Delta Waterways)

LOE ID:

333191

Pollutant:

Diazinon

LOE Subgroup:

Pollutant-Sediment

Matrix:

Sediment

Fraction:

Total

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

Field, Habitat, Toxicity, WQ from the City of Stockton and San Joaquin County Stormwater Program receiving water monitoring for the 2026 Integrated Report in Region 5

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Evaluation Guideline:

The evaluation guideline for diazinon, 1.1 ug/g, is one-tenth of the median lethal concentration for H. azteca(LC50; 11 ug/g) and is normalized by the percentage of organic carbon in the sediment sample. The LC50 11 ug/g is the geometric mean of LC50 values for diazinon from Ding et al. (2011).

Guideline Reference:

Toxicity of Sediment-Associated Pesticides to Chironomus dilutus and Hyalella azteca. Arch. Environ. Contam. Toxicol. 61:83¿92.

Spatial Representation:

Data were collected from 1 station(s). Station Code(s): CR-46RPP (Calaveras River receiving water - Pathogen Plan CR-46RPP).

Temporal Representation:

Data for this waterbody were collected over the date range 2017-06-01 to 2017-06-01

Environmental Conditions:

QAPP Information:

Stockton NPDES QAPP - City of Stockton & San Joaquin Co. Rec Water Mont.

QAPP Information Reference(s):

SWRCB - Region5 - Stockton NPDES QAPP - City of Stockton & San Joaquin Co. Rec Water Mont. - 402686

Line of Evidence (LOE) for Decision ID 160569, Diazinon	Region 5
Calaveras River, Lower (from Stockton Diverting Canal to the Delta Waterways)

LOE ID:

309697

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:

Data Reference:

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

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

All waters shall be maintained free of toxic substances in concentrations that produce detrimental physiological responses in human, plant, animal, or aquatic life.

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 Fish and Game Hazard Assessment diazinon criteria for freshwater aquatic life protection: 0.160 ug/L (1-hour average) and 0.100 ug/L (4-day average) concentrations, not to be exceeded more than once every three years.

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

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:

Water samples were collected from the lower Calaveras River at Ijams Road.

Temporal Representation:

Samples were collected weekly between 2 March and 6 April 2005.

Environmental Conditions:

QAPP Information:

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 160569, Diazinon	Region 5
Calaveras River, Lower (from Stockton Diverting Canal to the Delta Waterways)

LOE ID:

309696

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:

Sixteen water samples were collected from the lower Calaveras River between 18 June 2002 and 19 May 2003, representing sixteen calculated 4-day average concentrations and sixteen 1-hour average concentrations. Six of the sixteen 4-day average concentrations exceeded the 4-day average criterion of 0.100 ug/L. Three of the sixteen 1-hour average concentrations exceeded the 1-hour average criterion 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:

All waters shall be maintained free of toxic substances in concentrations that produce detrimental physiological responses in human, plant, animal, or aquatic life.

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

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:

Water samples were collected from the lower Calaveras River at Ijams Road.

Temporal Representation:

Samples were collected monthly between 18 June and 17 September 2002; on 19 December 2002; on 22 January 2003 and 18 February 2003; and nine times, either weekly or every two weeks, between 3 March and 19 May 2003.

Environmental Conditions:

QAPP Information:

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 160569, Diazinon	Region 5
Calaveras River, Lower (from Stockton Diverting Canal to the Delta Waterways)

LOE ID:

309695

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:

Five water samples were collected daily from the lower Calaveras River between 15 February and 19 February 2005, representing two calculated 4-day average concentrations and five 1-hour average concentrations. Zero of the two calculated 4-day average concentrations exceeded the 4-day average criterion of 0.100 ug/L. Zero of the five 1-hour average concentrations exceeded the 1-hour average criterion 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:

All waters shall be maintained free of toxic substances in concentrations that produce detrimental physiological responses in human, plant, animal, or aquatic life.

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

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:

Water samples were collected from the lower Calaveras River at Ijams Road.

Temporal Representation:

Samples were collected daily during a storm event, between 15 February and 19 February 2005.

Environmental Conditions:

QAPP Information:

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 160569, Diazinon	Region 5
Calaveras River, Lower (from Stockton Diverting Canal to the Delta Waterways)

LOE ID:

309694

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:

Fifteen water samples were collected from the lower Calaveras River, under the Central Valley Water Board's Pesticide TMDL program, between February and April 2004, representing nine calculated 4-day average concentrations and fifteen 1-hour average concentrations. Two of nine calculated 4-day average concentrations (2 February to 5 February 2005, and 16 February to 19 February 2005) exceeded the 4-day average criterion of 0.100 ug/L. Four of fifteen 1-hour average concentrations (2 February, 3 February, 26 February, and 17 February 2005) exceeded the 1-hour average criterion 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:

All waters shall be maintained free of toxic substances in concentrations that produce detrimental physiological responses in human, plant, animal, or aquatic life.

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

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:

Water samples were collected from the lower Calaveras River at Ijams Road.

Temporal Representation:

Samples were collected from the lower Calaveras River daily during two storm events (2 February to 6 February 2004 and 16 February to 20 February 2004), weekly in March, and once in early April 2004.

Environmental Conditions:

Water samples were collected during, and after, two storm events in February 2004.

QAPP Information:

QAPP Information Reference(s):


DECISION ID	152349	Region 5
Calaveras River, Lower (from Stockton Diverting Canal to the Delta Waterways)

Pollutant:	Indicator Bacteria
Final Listing Decision:	Do Not Delist from 303(d) list (being addressed with USEPA approved TMDL)
Last Listing Cycle's Final Listing Decision:	List on 303(d) list (being addressed by USEPA approved TMDL)(2018)
Revision Status	Revised
Sources:	Urban Runoff/Storm Sewers
TMDL Name:	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:	This waterbody was split as part of the 2024 cycle Delta Remapping Project. Decisions were reassessed based on the new spatial representation. There is sufficient justification to place this pollutant on the Being Addressed portion of the 303(d) list, because a TMDL has been completed and approved by RWQCB and USEPA, and it is expected to result in attainment of the standard.. The Stockton Urban Waterbodies Pathogen TMDL has been approved by the Central Valley Water Board in 2008 and approved by USEPA on 13 may 2008. Pursuant to section 3.11 of the Listing Policy, no 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 placed on the Being Addressed portion of the section 303(d) list because a TMDL has been completed and approved by USEPA and is expected to result in attainment of the standard. No new data or information was available during the 2024 Integrated Report cycle to reassess this water body segment and pollutant. 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 152349, Indicator Bacteria	Region 5
Calaveras River, Lower (from Stockton Diverting Canal to the Delta Waterways)

LOE ID:

309690

Pollutant:

Escherichia coli (E. coli)

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

None

Beneficial Use:

Water Contact Recreation

Number of Samples:

Number of Exceedances:

Data and Information Type:

PATHOGEN MONITORING

Data Used to Assess Water Quality:

Total Maximum Daily Load Report for Pathogens in: Five-Mile Slough, Lower Calaveras River, Mormon Slough, Mosher Slough, Smith Canal and Walker Slough, Final Staff Report, Appendix A, Unpublished Water Quality Data. Though included in the datasets for this LOE, the data described in this section does not include Deltakeeper water samples and results assessed in LOE 7003 (ref2932). Twelve of the 57 daily average results for water samples collected by the Deltakeeper exceeded the E. coli Evaluation Guideline value of 235 MPN/100 ml; the dates (and daily average E. coli MPN values) for the exceedances at "Diverting Canal" was: 21 October 2004 (754 MPN); at "UOP" was: 4 February 2004 (6,867 MPN); at "UOP footbridge" were: 21 April 2001 (1,302 MPN); 20 July 2001 (294 MPN); 8 March 2003 (>24,192 MPN); 11 April 2002 (472 MPN); 20 May 2002 (1,872 MPN); 14 April 2003 (3,609 MPN); and 6 February 2004 (419 MPN); at "DR Dock" were: 27 October 2004 (3,464 MPN); and 7 December 2004 (759 MPN); and at an unspecified location on 11 December 2003 (3,783 MPN) . Eight of the 17 daily average results for water samples collected by the CVRWQCB exceeded the E. coli Evaluation Guideline value of 235 MPN/100 ml; the dates (and daily average E. coli MPN values) for the exceedances at "Deltakeeper" were: 17 November 2005 (240 MPN); 19 December 2005 (850 MPN); and 20 December 2005 (700 MPN); at "McAllen Rd" were: 12 October 2005 (260 MPN); 25 October 2005 (600 MPN); and 17 November 2005 (300 MPN); at "UOP" were: 12 October 2005 (550 MPN); and 19 December 2005 (850 MPN).

Data Reference:

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

All waters shall be maintained free of toxic substances in concentrations that produce detrimental physiological responses in human, plant, animal, or aquatic life. This objective applies regardless of whether the toxicity is caused by a single substance or the interactive effect of multiple substances. (CRWQCB, 2006)

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:

E. coli bacteria levels should not exceed 235 MPN/100 mL in any single sample (USEPA E. coli objective).

Guideline Reference:

Ambient Water Quality Criteria for Bacteria - 1986. EPA440/5-84-002

Spatial Representation:

Though included in the datasets for this LOE, the data described in this section does not include water samples and results assessed in LOE 7003 (ref2932). Water samples were collected by Deltakeeper from the Calaveras River at "Deltakeeper's Dock", "Diverting Canal", "DR Dock", "UOP", "UOP footbridge", and 1 or more unspecified locations (the latter data was not assessed). Water samples were collected by the CVRWQCB from the Calaveras River at "Deltakeeper", McAllen Rd", and "UOP".

Temporal Representation:

Though included in the datasets for this LOE, the data described in this section does not include water samples and results collected by Deltakeeper and assessed as described in LOE 7003 (ref2932). Water samples were collected from the Calaveras River by Deltakeeper at "Diverting Canal" on: 21 October 2004; at "DR Dock" on: 27 March 2003; 8 April 2003; 12, 17,21 and 25 May 2004; 1, 5, 12, 19 and 27 July 2004; 1, 15, 22, and 30 September 2004; 27 October 2004; 7, 13, 20 and 27 December 2004; 5 January 2005; and 26 May 2005; at "UOP" on: 4 February 2004; at "UOP footbridge" on: 12 and 21 April 2001; 30 May 2001; 28 June 2001; 7 and 20 July 2001; 24 and 28 January 2002; 8, 11, 14 and 24 February 2002; 4, 8, 14, 20 and 29 March 2002; 11, 18 and 25 April 2002; 2, 9, 14, 20 and 31 May 2002; 27 March 2003; 14 April 2003; 2, 6 and 9 February 2004; and 26 March 2004; and at unspecified location(s) on: 11 December 2003; 25 April 2000; 2 May 2000; 13 June 2000; and 9 August 2000. Water samples were collected from the Calaveras River by the CVRWQCB at "Deltakeeper" on: 12 and 25 October 2005; 11, 17 and 28 November 2005; and 6, 19 and 20 December 2005; at "McAllen Rd" on: 12 and 25 October 2005; and 17 November 2005; at "UOP" on: 12 and 25 October 2005; 11, 17 and 28 November 2005; and 6, 19 and 20 December 2005.

Environmental Conditions:

QAPP Information:

Good. Monitoring was conducted by Deltakeeper and by the Central Valley Water Board for the San Joaquin River TMDL for pathogens

QAPP Information Reference(s):


DECISION ID	160574	Region 5
Calaveras River, Lower (from Stockton Diverting Canal to the Delta Waterways)

Pollutant:	Cyfluthrin
Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	New Decision
Revision Status	Revised
Impairment from Pollutant or Pollution:	Pollutant

Regional Board Conclusion:	Insufficient information is available to determine beneficial use support for this waterbody-pollutant combination with the statistical power and confidence required by the Listing Policy. Beneficial use support will be reassessed in a future cycle, if more data are available

Regional Board Decision Recommendation:	After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list. The readily available data and information is insufficient to determine, with the power and confidence of the Listing Policy, the applicable beneficial use support rating.

State Board Review of Regional Board Conclusion and Recommendation:

State Board Decision Recommendation:	After review of the available data and information, SWRCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list because it cannot be determined if applicable water quality standards are not being exceeded.

Line of Evidence (LOE) for Decision ID 160574, Cyfluthrin	Region 5
Calaveras River, Lower (from Stockton Diverting Canal to the Delta Waterways)

LOE ID:

333158

Pollutant:

Cyfluthrin

LOE Subgroup:

Pollutant-Sediment

Matrix:

Sediment

Fraction:

Total

Beneficial Use:

Cold 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 City of Stockton & San Joaquin Co. Rec Water Mont. data for Calaveras River, Lower (from Stockton Diverting Canal to the Delta Waterways) to determine beneficial use support and the results are as follows: 1 of the 2 samples exceeded the evaluation guideline for Cyfluthrin, total. Although a total of 3 samples were collected, 1 of these samples were not included in the assessment because the laboratory data reporting limit(s) was above the objective and therefore the results could not be quantified with the level of certainty required by the Listing Policy Section 6.1.5.5.

Data Reference:

Field, Habitat, Toxicity, WQ from the City of Stockton and San Joaquin County Stormwater Program receiving water monitoring for the 2026 Integrated Report in Region 5

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Evaluation Guideline:

The evaluation guideline for cyfluthrin, 0.11 ug/g, is one-tenth of the median lethal concentration (LC50; 1.1 ug/g) and is normalized by the percentage of organic carbon in the sediment sample. The LC50 1.1 ug/g is the geometric mean of LC50 values for cyfluthrin from Amweg et al. (2005).

Guideline Reference:

Use and Toxicity of Pyrethroid Pesticides in the Central Valley, California, USA. Environmental Toxicology and Chemistry, 24:966-972, with erratum 24:No. 5

Guideline Reference:

Whole-sediment toxicity identification evaluation tools for pyrethroid insecticides: I. piperonyl butoxide addition. Environ. Toxicol. Chem. 26:2389-2396.

Spatial Representation:

Data were collected from 1 station(s). Station Code(s): CR-46RPP (Calaveras River receiving water - Pathogen Plan CR-46RPP).

Temporal Representation:

Data for this waterbody were collected over the date range 2016-10-17 to 2017-06-01

Environmental Conditions:

QAPP Information:

Stockton NPDES QAPP - City of Stockton & San Joaquin Co. Rec Water Mont.

QAPP Information Reference(s):

SWRCB - Region5 - Stockton NPDES QAPP - City of Stockton & San Joaquin Co. Rec Water Mont. - 402686


DECISION ID	160578	Region 5
Calaveras River, Lower (from Stockton Diverting Canal to the Delta Waterways)

Pollutant:	Esfenvalerate/Fenvalerate
Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	New Decision
Revision Status	Revised
Impairment from Pollutant or Pollution:	Pollutant

Regional Board Conclusion:	Insufficient information is available to determine beneficial use support for this waterbody-pollutant combination with the statistical power and confidence required by the Listing Policy. Beneficial use support will be reassessed in a future cycle, if more data are available

Regional Board Decision Recommendation:	After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list. The readily available data and information is insufficient to determine, with the power and confidence of the Listing Policy, the applicable beneficial use support rating.

State Board Review of Regional Board Conclusion and Recommendation:

State Board Decision Recommendation:	After review of the available data and information, SWRCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list because it cannot be determined if applicable water quality standards are not being exceeded.

Line of Evidence (LOE) for Decision ID 160578, Esfenvalerate/Fenvalerate	Region 5
Calaveras River, Lower (from Stockton Diverting Canal to the Delta Waterways)

LOE ID:

333199

Pollutant:

Esfenvalerate/Fenvalerate

LOE Subgroup:

Pollutant-Sediment

Matrix:

Sediment

Fraction:

Total

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

Field, Habitat, Toxicity, WQ from the City of Stockton and San Joaquin County Stormwater Program receiving water monitoring for the 2026 Integrated Report in Region 5

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Evaluation Guideline:

The evaluation guideline for esfenvalerate/fenvalerate, 0.15 ug/g, is one-tenth of the median lethal concentration (LC50; 1.5 ug/g) and is normalized by the percentage of organic carbon in the sediment sample. The LC50 1.5 ug/g is the geometric mean of LC50 values for esfenvalerate/fenvalerate from Amweg et al. (2005).

Guideline Reference:

Use and Toxicity of Pyrethroid Pesticides in the Central Valley, California, USA. Environmental Toxicology and Chemistry, 24:966-972, with erratum 24:No. 5

Guideline Reference:

Whole-sediment toxicity identification evaluation tools for pyrethroid insecticides: I. piperonyl butoxide addition. Environ. Toxicol. Chem. 26:2389-2396.

Spatial Representation:

Data were collected from 1 station(s). Station Code(s): CR-46RPP (Calaveras River receiving water - Pathogen Plan CR-46RPP).

Temporal Representation:

Data for this waterbody were collected over the date range 2016-10-17 to 2017-06-01

Environmental Conditions:

QAPP Information:

Stockton NPDES QAPP - City of Stockton & San Joaquin Co. Rec Water Mont.

QAPP Information Reference(s):

SWRCB - Region5 - Stockton NPDES QAPP - City of Stockton & San Joaquin Co. Rec Water Mont. - 402686


DECISION ID	160577	Region 5
Calaveras River, Lower (from Stockton Diverting Canal to the Delta Waterways)

Pollutant:	Fenpropathrin
Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	New Decision
Revision Status	Revised
Impairment from Pollutant or Pollution:	Pollutant

Regional Board Conclusion:	Insufficient information is available to determine beneficial use support for this waterbody-pollutant combination with the statistical power and confidence required by the Listing Policy. Beneficial use support will be reassessed in a future cycle, if more data are available

Regional Board Decision Recommendation:	After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list. The readily available data and information is insufficient to determine, with the power and confidence of the Listing Policy, the applicable beneficial use support rating.

State Board Review of Regional Board Conclusion and Recommendation:

State Board Decision Recommendation:	After review of the available data and information, SWRCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list because it cannot be determined if applicable water quality standards are not being exceeded.

Line of Evidence (LOE) for Decision ID 160577, Fenpropathrin	Region 5
Calaveras River, Lower (from Stockton Diverting Canal to the Delta Waterways)

LOE ID:

333207

Pollutant:

Fenpropathrin

LOE Subgroup:

Pollutant-Sediment

Matrix:

Sediment

Fraction:

Total

Beneficial Use:

Cold 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 City of Stockton & San Joaquin Co. Rec Water Mont. data for Calaveras River, Lower (from Stockton Diverting Canal to the Delta Waterways) to determine beneficial use support and the results are as follows: 0 of the 1 samples exceeded the evaluation guideline for Fenpropathrin. Although a total of 2 samples were collected, 1 of these samples were not included in the assessment because the laboratory data reporting limit(s) was above the objective and therefore the results could not be quantified with the level of certainty required by the Listing Policy Section 6.1.5.5.

Data Reference:

Field, Habitat, Toxicity, WQ from the City of Stockton and San Joaquin County Stormwater Program receiving water monitoring for the 2026 Integrated Report in Region 5

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Evaluation Guideline:

The evaluation guideline for fenpropathrin, 0.1 ug/g, is one-tenth of the median lethal concentration (LC50; 1 ug/g) and is normalized by the percentage of organic carbon in the sediment sample. The LC50 1 ug/g is the geometric mean of LC50 values for fenpropathrin from Ding et al. ( 2011).

Guideline Reference:

Toxicity of Sediment-Associated Pesticides to Chironomus dilutus and Hyalella azteca. Arch. Environ. Contam. Toxicol. 61:83¿92.

Spatial Representation:

Data were collected from 1 station(s). Station Code(s): CR-46RPP (Calaveras River receiving water - Pathogen Plan CR-46RPP).

Temporal Representation:

Data for this waterbody were collected over the date range 2016-10-17 to 2017-06-01

Environmental Conditions:

QAPP Information:

Stockton NPDES QAPP - City of Stockton & San Joaquin Co. Rec Water Mont.

QAPP Information Reference(s):

SWRCB - Region5 - Stockton NPDES QAPP - City of Stockton & San Joaquin Co. Rec Water Mont. - 402686


DECISION ID	160579	Region 5
Calaveras River, Lower (from Stockton Diverting Canal to the Delta Waterways)

Pollutant:	Permethrin
Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	New Decision
Revision Status	Revised
Impairment from Pollutant or Pollution:	Pollutant

Regional Board Conclusion:	Insufficient information is available to determine beneficial use support for this waterbody-pollutant combination with the statistical power and confidence required by the Listing Policy. Beneficial use support will be reassessed in a future cycle, if more data are available

Regional Board Decision Recommendation:	After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list. The readily available data and information is insufficient to determine, with the power and confidence of the Listing Policy, the applicable beneficial use support rating.

State Board Review of Regional Board Conclusion and Recommendation:

State Board Decision Recommendation:	After review of the available data and information, SWRCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list because it cannot be determined if applicable water quality standards are not being exceeded.

Line of Evidence (LOE) for Decision ID 160579, Permethrin	Region 5
Calaveras River, Lower (from Stockton Diverting Canal to the Delta Waterways)

LOE ID:

333247

Pollutant:

Permethrin

LOE Subgroup:

Pollutant-Sediment

Matrix:

Sediment

Fraction:

Total

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

Field, Habitat, Toxicity, WQ from the City of Stockton and San Joaquin County Stormwater Program receiving water monitoring for the 2026 Integrated Report in Region 5

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Evaluation Guideline:

The evaluation guideline for permethrin, 0.89 ug/g, is one-tenth of the median lethal concentration (LC50; 8.9 ug/g) and is normalized by the percentage of organic carbon in the sediment sample. The LC50 8.9 ug/g is the geometric mean of LC50 values for permethrin from Amweg et al. (2005).

Guideline Reference:

Use and Toxicity of Pyrethroid Pesticides in the Central Valley, California, USA. Environmental Toxicology and Chemistry, 24:966-972, with erratum 24:No. 5

Guideline Reference:

Whole-sediment toxicity identification evaluation tools for pyrethroid insecticides: I. piperonyl butoxide addition. Environ. Toxicol. Chem. 26:2389-2396.

Spatial Representation:

Data were collected from 1 station(s). Station Code(s): CR-46RPP (Calaveras River receiving water - Pathogen Plan CR-46RPP).

Temporal Representation:

Data for this waterbody were collected over the date range 2016-10-17 to 2017-06-01

Environmental Conditions:

QAPP Information:

Stockton NPDES QAPP - City of Stockton & San Joaquin Co. Rec Water Mont.

QAPP Information Reference(s):

SWRCB - Region5 - Stockton NPDES QAPP - City of Stockton & San Joaquin Co. Rec Water Mont. - 402686


DECISION ID	160572	Region 5
Calaveras River, Lower (from Stockton Diverting Canal to the Delta Waterways)

Pollutant:	Bifenthrin
Final Listing Decision:	List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	New Decision
Revision Status	Revised
Sources:	A Source Unknown
TMDL Priority:	Low
Impairment from Pollutant or Pollution:	Pollutant

Regional Board Conclusion:	This pollutant is being considered for placement on the CWA section 303(d) List under section 3.6 of the Listing Policy. Under section 3.6 at least two lines of evidence are necessary to assess listing status for pollutants sediment, and pollutant concentrations in sediment must be associated with sediment toxicity to justify adding that pollutant to the CWA section 303(d) List. Two lines of evidence are available in the administrative record to assess this pollutant. Two of the two sediment samples exceed the evaluation guideline for COLD. Two of the two samples exhibited associated sediment toxicity. The water quality objective for pesticides states, in relevant part, that "discharges shall not result in pesticide concentrations in bottom sediments or aquatic life that adversely affect beneficial uses." Pesticides are not naturally occurring in the environment so any measured concentrations of pesticides are presumed to be the result of discharges. Based on the readily available data and information, the weight of evidence indicates that there is sufficient justification for 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. Two of the two sediment samples exceed the evaluation guideline and this sample size is sufficient to determine beneficial use support, with the power and confidence of the Listing Policy. There is associated sediment toxicity data as required by Section 3.6 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. The water quality objective for pesticides states, in relevant part, that "discharges shall not result in pesticide concentrations in bottom sediments or aquatic life that adversely affect beneficial uses." Pesticides are not naturally occurring in the environment so any measured concentrations of pesticides are presumed to be the result of discharges.

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:

Line of Evidence (LOE) for Decision ID 160572, Bifenthrin	Region 5
Calaveras River, Lower (from Stockton Diverting Canal to the Delta Waterways)

LOE ID:

333108

Pollutant:

Bifenthrin

LOE Subgroup:

Pollutant-Sediment

Matrix:

Sediment

Fraction:

Total

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

Field, Habitat, Toxicity, WQ from the City of Stockton and San Joaquin County Stormwater Program receiving water monitoring for the 2026 Integrated Report in Region 5

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Evaluation Guideline:

The evaluation guideline for bifenthrin, 0.043 ug/g, is one-tenth of the median lethal concentration (LC50; 0.43 ug/g) and is normalized by the percentage of organic carbon in the sediment sample. The LC50 0.43 ug/g is the geometric mean of LC50 values for bifenthrin from Amweg et al. (2005) and Amweg and Weston (2007).

Guideline Reference:

Use and Toxicity of Pyrethroid Pesticides in the Central Valley, California, USA. Environmental Toxicology and Chemistry, 24:966-972, with erratum 24:No. 5

Guideline Reference:

Whole-sediment toxicity identification evaluation tools for pyrethroid insecticides: I. piperonyl butoxide addition. Environ. Toxicol. Chem. 26:2389-2396.

Spatial Representation:

Data were collected from 1 station(s). Station Code(s): CR-46RPP (Calaveras River receiving water - Pathogen Plan CR-46RPP).

Temporal Representation:

Data for this waterbody were collected over the date range 2016-10-17 to 2017-06-01

Environmental Conditions:

QAPP Information:

Stockton NPDES QAPP - City of Stockton & San Joaquin Co. Rec Water Mont.

QAPP Information Reference(s):

SWRCB - Region5 - Stockton NPDES QAPP - City of Stockton & San Joaquin Co. Rec Water Mont. - 402686

Line of Evidence (LOE) for Decision ID 160572, Bifenthrin	Region 5
Calaveras River, Lower (from Stockton Diverting Canal to the Delta Waterways)

LOE ID:

347454

Pollutant:

Toxicity

LOE Subgroup:

Toxicity

Matrix:

Sediment

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:

3 of the 3 samples collected by City of Stockton & San Joaquin Co. Rec Water Mont. for Calaveras River, Lower (from Stockton Diverting Canal to the Delta Waterways) exhibited toxicity. A sample may have multiple toxicity test results, but will only be counted once. A sample is defined as being collected on the same day and the same location. The following organisms and parameters were utilized for the toxicity tests: Hyalella azteca for Survival, Hyalella azteca for Growth (wt/surv indiv). The following tests exhibited toxicity: Hyalella azteca for Survival on 2016-10-17, Hyalella azteca for Growth (wt/surv indiv) on 2016-10-17, Hyalella azteca for Growth (wt/surv indiv) on 2017-03-14, Hyalella azteca for Survival on 2017-06-01.

Data Reference:

Field, Habitat, Toxicity, WQ from the City of Stockton and San Joaquin County Stormwater Program receiving water monitoring for the 2026 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 produce detrimental physiological responses in human, plant, animal, or aquatic life.

Objective/Criterion Reference:

Evaluation Guideline:

The sample is toxic when the response of the organisms exposed to the sample is significantly different (worse) than the response of the organisms exposed to the laboratory control based on statistical hypothesis testing. An exceedance is counted when the significant effect code is "Significant; Less Similarity," which means that the sample result is significantly different than the control result, and the percent effect is greater than the evaluation threshold. The default evaluation threshold is 20% unless otherwise stated.

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 monitoring site: CR-46RPP ( Calaveras River receiving water - Pathogen Plan CR-46RPP ).

Temporal Representation:

The samples were collected between the dates of 2016-10-17 and 2017-06-01.

Environmental Conditions:

QAPP Information:

Stockton NPDES QAPP - City of Stockton & San Joaquin Co. Rec Water Mont.

QAPP Information Reference(s):

SWRCB - Region5 - Stockton NPDES QAPP - City of Stockton & San Joaquin Co. Rec Water Mont. - 402686


DECISION ID	160576	Region 5
Calaveras River, Lower (from Stockton Diverting Canal to the Delta Waterways)

Pollutant:	Cyhalothrin, Lambda
Final Listing Decision:	List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	New Decision
Revision Status	Revised
Sources:	A Source Unknown
TMDL Priority:	Low
Impairment from Pollutant or Pollution:	Pollutant

Regional Board Conclusion:	This pollutant is being considered for placement on the CWA section 303(d) List under section 3.6 of the Listing Policy. Under section 3.6 at least two lines of evidence are necessary to assess listing status for pollutants sediment, and pollutant concentrations in sediment must be associated with sediment toxicity to justify adding that pollutant to the CWA section 303(d) List. Two lines of evidence are available in the administrative record to assess this pollutant. Two of two samples exceed the evaluation guideline for COLD. Two exceeding sediment samples exhibited sediment toxicity. The water quality objective for pesticides states, in relevant part, that "discharges shall not result in pesticide concentrations in bottom sediments or aquatic life that adversely affect beneficial uses." Pesticides are not naturally occurring in the environment so any measured concentrations of pesticides are presumed to be the result of discharges. Based on the readily available data and information, the weight of evidence indicates that there is sufficient justification for 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. Two of the two sediment samples exceed the evaluation guideline and this sample size is sufficient to determine beneficial use support, with the power and confidence of the Listing Policy. There is associated sediment toxicity as required by Section 3.6 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:

Line of Evidence (LOE) for Decision ID 160576, Cyhalothrin, Lambda	Region 5
Calaveras River, Lower (from Stockton Diverting Canal to the Delta Waterways)

LOE ID:

347454

Pollutant:

Toxicity

LOE Subgroup:

Toxicity

Matrix:

Sediment

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:

Data Reference:

Field, Habitat, Toxicity, WQ from the City of Stockton and San Joaquin County Stormwater Program receiving water monitoring for the 2026 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 produce detrimental physiological responses in human, plant, animal, or aquatic life.

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at monitoring site: CR-46RPP ( Calaveras River receiving water - Pathogen Plan CR-46RPP ).

Temporal Representation:

The samples were collected between the dates of 2016-10-17 and 2017-06-01.

Environmental Conditions:

QAPP Information:

Stockton NPDES QAPP - City of Stockton & San Joaquin Co. Rec Water Mont.

QAPP Information Reference(s):

SWRCB - Region5 - Stockton NPDES QAPP - City of Stockton & San Joaquin Co. Rec Water Mont. - 402686

Line of Evidence (LOE) for Decision ID 160576, Cyhalothrin, Lambda	Region 5
Calaveras River, Lower (from Stockton Diverting Canal to the Delta Waterways)

LOE ID:

333162

Pollutant:

Cyhalothrin, Lambda

LOE Subgroup:

Pollutant-Sediment

Matrix:

Sediment

Fraction:

Total

Beneficial Use:

Cold 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 City of Stockton & San Joaquin Co. Rec Water Mont. data for Calaveras River, Lower (from Stockton Diverting Canal to the Delta Waterways) to determine beneficial use support and the results are as follows: 2 of the 2 samples exceeded the evaluation guideline for Cyhalothrin, Total lambda-. Although a total of 3 samples were collected, 1 of these samples were not included in the assessment because the laboratory data reporting limit(s) was above the objective and therefore the results could not be quantified with the level of certainty required by the Listing Policy Section 6.1.5.5.

Data Reference:

Field, Habitat, Toxicity, WQ from the City of Stockton and San Joaquin County Stormwater Program receiving water monitoring for the 2026 Integrated Report in Region 5

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Evaluation Guideline:

The evaluation guideline for lambda-cyhalothrin, 0.044 ug/g, is one-tenth of the median lethal concentration (LC50; 0.44 ug/g) and is normalized by the percentage of organic carbon in the sediment sample. The LC50 0.44 ug/g is the geometric mean of LC50 values for lambda-cyhalothrin from Amweg et al. (2005).

Guideline Reference:

Use and Toxicity of Pyrethroid Pesticides in the Central Valley, California, USA. Environmental Toxicology and Chemistry, 24:966-972, with erratum 24:No. 5

Guideline Reference:

Whole-sediment toxicity identification evaluation tools for pyrethroid insecticides: I. piperonyl butoxide addition. Environ. Toxicol. Chem. 26:2389-2396.

Spatial Representation:

Data were collected from 1 station(s). Station Code(s): CR-46RPP (Calaveras River receiving water - Pathogen Plan CR-46RPP).

Temporal Representation:

Data for this waterbody were collected over the date range 2016-10-17 to 2017-06-01

Environmental Conditions:

QAPP Information:

Stockton NPDES QAPP - City of Stockton & San Joaquin Co. Rec Water Mont.

QAPP Information Reference(s):

SWRCB - Region5 - Stockton NPDES QAPP - City of Stockton & San Joaquin Co. Rec Water Mont. - 402686


DECISION ID	160573	Region 5
Calaveras River, Lower (from Stockton Diverting Canal to the Delta Waterways)

Pollutant:	Cypermethrin
Final Listing Decision:	List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	New Decision
Revision Status	Revised
Sources:	A Source Unknown
TMDL Priority:	Low
Impairment from Pollutant or Pollution:	Pollutant

Regional Board Conclusion:	This pollutant is being considered for placement on the CWA section 303(d) List under section 3.6 of the Listing Policy. Under section 3.6 at least two lines of evidence are necessary to assess listing status for pollutants sediment, and pollutant concentrations in sediment must be associated with sediment toxicity to justify adding that pollutant to the CWA section 303(d) List. Two lines of evidence are available in the administrative record to assess this pollutant. Two of the two sediment exceed the evaluation guideline for COLD. Two of two exceeding sediment samples exhibited sediment toxicity. The water quality objective for pesticides states, in relevant part, that "discharges shall not result in pesticide concentrations in bottom sediments or aquatic life that adversely affect beneficial uses." Pesticides are not naturally occurring in the environment so any measured concentrations of pesticides are presumed to be the result of discharges. Based on the readily available data and information, the weight of evidence indicates that there is sufficient justification for 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. Two of the two sediment samples exceed the evaluation guideline for COLD and this sample size is sufficient to determine beneficial use support, with the power and confidence of the Listing Policy. There is associated sediment toxicity data as required by Section 3.6 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:

Line of Evidence (LOE) for Decision ID 160573, Cypermethrin	Region 5
Calaveras River, Lower (from Stockton Diverting Canal to the Delta Waterways)

LOE ID:

347454

Pollutant:

Toxicity

LOE Subgroup:

Toxicity

Matrix:

Sediment

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:

Data Reference:

Field, Habitat, Toxicity, WQ from the City of Stockton and San Joaquin County Stormwater Program receiving water monitoring for the 2026 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 produce detrimental physiological responses in human, plant, animal, or aquatic life.

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at monitoring site: CR-46RPP ( Calaveras River receiving water - Pathogen Plan CR-46RPP ).

Temporal Representation:

The samples were collected between the dates of 2016-10-17 and 2017-06-01.

Environmental Conditions:

QAPP Information:

Stockton NPDES QAPP - City of Stockton & San Joaquin Co. Rec Water Mont.

QAPP Information Reference(s):

SWRCB - Region5 - Stockton NPDES QAPP - City of Stockton & San Joaquin Co. Rec Water Mont. - 402686

Line of Evidence (LOE) for Decision ID 160573, Cypermethrin	Region 5
Calaveras River, Lower (from Stockton Diverting Canal to the Delta Waterways)

LOE ID:

333172

Pollutant:

Cypermethrin

LOE Subgroup:

Pollutant-Sediment

Matrix:

Sediment

Fraction:

Total

Beneficial Use:

Cold 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 City of Stockton & San Joaquin Co. Rec Water Mont. data for Calaveras River, Lower (from Stockton Diverting Canal to the Delta Waterways) to determine beneficial use support and the results are as follows: 2 of the 2 samples exceeded the evaluation guideline for Cypermethrin, Total. Although a total of 3 samples were collected, 1 of these samples were not included in the assessment because the laboratory data reporting limit(s) was above the objective and therefore the results could not be quantified with the level of certainty required by the Listing Policy Section 6.1.5.5.

Data Reference:

Field, Habitat, Toxicity, WQ from the City of Stockton and San Joaquin County Stormwater Program receiving water monitoring for the 2026 Integrated Report in Region 5

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Evaluation Guideline:

The evaluation guideline for cypermethrin, 0.03 ug/g, is one-tenth of the median lethal concentration (LC50; 0.3 ug/g) and is normalized by the percentage of organic carbon in the sediment sample. The LC50 0.3 ug/g is the geometric mean of LC50 values for cypermethrin from Maund et al. (2002).

Guideline Reference:

Partitioning, bioavailability, and toxicity of the pyrethroid insecticide cypermethrin in sediments. Environmental Toxicology and Chemistry 21:9-15

Spatial Representation:

Data were collected from 1 station(s). Station Code(s): CR-46RPP (Calaveras River receiving water - Pathogen Plan CR-46RPP).

Temporal Representation:

Data for this waterbody were collected over the date range 2016-10-17 to 2017-06-01

Environmental Conditions:

QAPP Information:

Stockton NPDES QAPP - City of Stockton & San Joaquin Co. Rec Water Mont.

QAPP Information Reference(s):

SWRCB - Region5 - Stockton NPDES QAPP - City of Stockton & San Joaquin Co. Rec Water Mont. - 402686


DECISION ID	160575	Region 5
Calaveras River, Lower (from Stockton Diverting Canal to the Delta Waterways)

Pollutant:	Deltamethrin
Final Listing Decision:	List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	New Decision
Revision Status	Revised
Sources:	A Source Unknown
TMDL Priority:	Low
Impairment from Pollutant or Pollution:	Pollutant

Regional Board Conclusion:	This pollutant is being considered for placement on the CWA section 303(d) List under section 3.6 of the Listing Policy. Under section 3.6 at least two lines of evidence are necessary to assess listing status for pollutants sediment, and pollutant concentrations in sediment must be associated with sediment toxicity to justify adding that pollutant to the CWA section 303(d) List. Two lines of evidence are available in the administrative record to assess this pollutant. Two of the two sediment samples exceed the evaluation guideline for COLD. Two of two exceeding sediment samples exhibited sediment toxicity. The water quality objective for pesticides states, in relevant part, that "discharges shall not result in pesticide concentrations in bottom sediments or aquatic life that adversely affect beneficial uses." Pesticides are not naturally occurring in the environment so any measured concentrations of pesticides are presumed to be the result of discharges. Based on the readily available data and information, the weight of evidence indicates that there is sufficient justification for 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. Two of the two sediment samples exceed the evaluation guideline and this sample size is sufficient to determine beneficial use support, with the power and confidence of the Listing Policy. There is associated sediment toxicity data as required by Section 3.6 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:

Line of Evidence (LOE) for Decision ID 160575, Deltamethrin	Region 5
Calaveras River, Lower (from Stockton Diverting Canal to the Delta Waterways)

LOE ID:

333187

Pollutant:

Deltamethrin

LOE Subgroup:

Pollutant-Sediment

Matrix:

Sediment

Fraction:

Total

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

Field, Habitat, Toxicity, WQ from the City of Stockton and San Joaquin County Stormwater Program receiving water monitoring for the 2026 Integrated Report in Region 5

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Evaluation Guideline:

The evaluation guideline for deltamethrin, 0.079 ug/g, is one-tenth of the median lethal concentration (LC50; 0.79 ug/g) and is normalized by the percentage of organic carbon in the sediment sample. The LC50 0.79 ug/g is the geometric mean of LC50 values for deltamethrin from Amweg et al. (2005).

Guideline Reference:

Use and Toxicity of Pyrethroid Pesticides in the Central Valley, California, USA. Environmental Toxicology and Chemistry, 24:966-972, with erratum 24:No. 5

Guideline Reference:

Whole-sediment toxicity identification evaluation tools for pyrethroid insecticides: I. piperonyl butoxide addition. Environ. Toxicol. Chem. 26:2389-2396.

Spatial Representation:

Data were collected from 1 station(s). Station Code(s): CR-46RPP (Calaveras River receiving water - Pathogen Plan CR-46RPP).

Temporal Representation:

Data for this waterbody were collected over the date range 2016-10-17 to 2017-06-01

Environmental Conditions:

QAPP Information:

Stockton NPDES QAPP - City of Stockton & San Joaquin Co. Rec Water Mont.

QAPP Information Reference(s):

SWRCB - Region5 - Stockton NPDES QAPP - City of Stockton & San Joaquin Co. Rec Water Mont. - 402686

Line of Evidence (LOE) for Decision ID 160575, Deltamethrin	Region 5
Calaveras River, Lower (from Stockton Diverting Canal to the Delta Waterways)

LOE ID:

347454

Pollutant:

Toxicity

LOE Subgroup:

Toxicity

Matrix:

Sediment

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:

Data Reference:

Field, Habitat, Toxicity, WQ from the City of Stockton and San Joaquin County Stormwater Program receiving water monitoring for the 2026 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 produce detrimental physiological responses in human, plant, animal, or aquatic life.

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at monitoring site: CR-46RPP ( Calaveras River receiving water - Pathogen Plan CR-46RPP ).

Temporal Representation:

The samples were collected between the dates of 2016-10-17 and 2017-06-01.

Environmental Conditions:

QAPP Information:

Stockton NPDES QAPP - City of Stockton & San Joaquin Co. Rec Water Mont.

QAPP Information Reference(s):

SWRCB - Region5 - Stockton NPDES QAPP - City of Stockton & San Joaquin Co. Rec Water Mont. - 402686


DECISION ID	160571	Region 5
Calaveras River, Lower (from Stockton Diverting Canal to the Delta Waterways)

Pollutant:	Pyrethroids
Final Listing Decision:	List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	New Decision
Revision Status	Revised
Sources:	A Source Unknown
TMDL Priority:	Low
Impairment from Pollutant or Pollution:	Pollutant

Regional Board Conclusion:	This pollutant is being considered for placement on the CWA section 303(d) List under section 3.6 of the Listing Policy. Under section 3.6 at least two lines of evidence are necessary to assess listing status for pollutants sediment, and pollutant concentrations in sediment must be associated with sediment toxicity to justify adding that pollutant to the CWA section 303(d) List. Two lines of evidence are available in the administrative record to assess this pollutant. Two of the two sediment samples exceed the evaluation guideline for COLD. Two of two exceeding samples exhibited sediment toxicity. The water quality objective for pesticides states, in relevant part, that "discharges shall not result in pesticide concentrations in bottom sediments or aquatic life that adversely affect beneficial uses." Pesticides are not naturally occurring in the environment so any measured concentrations of pesticides are presumed to be the result of discharges. Based on the readily available data and information, the weight of evidence indicates that there is sufficient justification for 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. Two of the two sediment samples exceed the evaluation guideline for COLD and this sample size is sufficient to determine beneficial use support, with the power and confidence of the Listing Policy. There is associated sediment toxicity as required by Section 3.6 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:

Line of Evidence (LOE) for Decision ID 160571, Pyrethroids	Region 5
Calaveras River, Lower (from Stockton Diverting Canal to the Delta Waterways)

LOE ID:

333261

Pollutant:

Pyrethroids

LOE Subgroup:

Pollutant-Sediment

Matrix:

Sediment

Fraction:

Total

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

Field, Habitat, Toxicity, WQ from the City of Stockton and San Joaquin County Stormwater Program receiving water monitoring for the 2026 Integrated Report in Region 5

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Evaluation Guideline:

The evaluation guideline for the protection of aquatic life from pyrethroids is one toxic unit. Individual pyrethroid concentrations in sediment were normalized to organic carbon content, divided by the respective 1/10 LC50 and then summed. A sum over over one toxic unit is an exceedance of the evaluation guideline (Amweg et al. 2006).

Guideline Reference:

Use and Toxicity of Pyrethroid Pesticides in the Central Valley, California, USA. Environmental Toxicology and Chemistry, 24:966-972, with erratum 24:No. 5

Guideline Reference:

Partitioning, bioavailability, and toxicity of the pyrethroid insecticide cypermethrin in sediments. Environmental Toxicology and Chemistry 21:9-15

Guideline Reference:

Toxicity of Sediment-Associated Pesticides to Chironomus dilutus and Hyalella azteca. Arch. Environ. Contam. Toxicol. 61:83¿92.

Guideline Reference:

Whole-sediment toxicity identification evaluation tools for pyrethroid insecticides: I. piperonyl butoxide addition. Environ. Toxicol. Chem. 26:2389-2396.

Guideline Reference:

Compilation of freshwater OC-normalized sediment toxicity data for pyrethroids

Guideline Reference:

Pyrethroid insecticides and sediment toxicity in urban creeks from California and Tennessee. Environmental Science and Technology, 40(5): 1700-1706

Spatial Representation:

Data were collected from 1 station(s). Station Code(s): CR-46RPP (Calaveras River receiving water - Pathogen Plan CR-46RPP).

Temporal Representation:

Data for this waterbody were collected over the date range 2016-10-17 to 2017-06-01

Environmental Conditions:

QAPP Information:

Stockton NPDES QAPP - City of Stockton & San Joaquin Co. Rec Water Mont.

QAPP Information Reference(s):

SWRCB - Region5 - Stockton NPDES QAPP - City of Stockton & San Joaquin Co. Rec Water Mont. - 402686

Line of Evidence (LOE) for Decision ID 160571, Pyrethroids	Region 5
Calaveras River, Lower (from Stockton Diverting Canal to the Delta Waterways)

LOE ID:

347454

Pollutant:

Toxicity

LOE Subgroup:

Toxicity

Matrix:

Sediment

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:

Data Reference:

Field, Habitat, Toxicity, WQ from the City of Stockton and San Joaquin County Stormwater Program receiving water monitoring for the 2026 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 produce detrimental physiological responses in human, plant, animal, or aquatic life.

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at monitoring site: CR-46RPP ( Calaveras River receiving water - Pathogen Plan CR-46RPP ).

Temporal Representation:

The samples were collected between the dates of 2016-10-17 and 2017-06-01.

Environmental Conditions:

QAPP Information:

Stockton NPDES QAPP - City of Stockton & San Joaquin Co. Rec Water Mont.

QAPP Information Reference(s):

SWRCB - Region5 - Stockton NPDES QAPP - City of Stockton & San Joaquin Co. Rec Water Mont. - 402686


DECISION ID	168340	Region 5
Calaveras River, Lower (from Stockton Diverting Canal to the Delta Waterways)

Pollutant:	Toxicity
Final Listing Decision:	List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	New Decision
Revision Status	Revised
Sources:	A Source Unknown
TMDL Priority:	Low
Impairment from Pollutant or Pollution:	Pollutant

Regional Board Conclusion:	This pollutant is being considered for placement on the CWA section 303(d) List under section 3.1 of the Listing Policy. Under section 3.1 a single line of evidence is necessary to assess listing status. One lines of evidence are available in the administrative record to assess this pollutant. Three of the three samples exceed the objective for the aquatic life beneficial use. Based on the readily available data and information, the weight of evidence indicates that there is sufficient justification in favor of placing this water segment-pollutant combination on the CWA section 303(d) List. This conclusion is based on the staff findings that: 1. The data used satisfies the data quality requirements of section 6.1.4 of the Policy. 2. The data used satisfies the data quantity requirements of section 6.1.5 of the Policy. 3. Three of the three samples exceed the objective for the aquatic life beneficial use, 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:

Line of Evidence (LOE) for Decision ID 168340, Toxicity	Region 5
Calaveras River, Lower (from Stockton Diverting Canal to the Delta Waterways)

LOE ID:

347454

Pollutant:

Toxicity

LOE Subgroup:

Toxicity

Matrix:

Sediment

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:

Data Reference:

Field, Habitat, Toxicity, WQ from the City of Stockton and San Joaquin County Stormwater Program receiving water monitoring for the 2026 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 produce detrimental physiological responses in human, plant, animal, or aquatic life.

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at monitoring site: CR-46RPP ( Calaveras River receiving water - Pathogen Plan CR-46RPP ).

Temporal Representation:

The samples were collected between the dates of 2016-10-17 and 2017-06-01.

Environmental Conditions:

QAPP Information:

Stockton NPDES QAPP - City of Stockton & San Joaquin Co. Rec Water Mont.

QAPP Information Reference(s):

SWRCB - Region5 - Stockton NPDES QAPP - City of Stockton & San Joaquin Co. Rec Water Mont. - 402686