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

Water Quality Control Plan for the Lahontan Region (as amended)

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

There is no site-specific numerical objective in the Lahontan Basin Plan for Total Nitrogen for this segment. The regionwide narrative objective for biostimulatory substances states: "Waters shall not contain biostimulatory substances in concentrations that promote aquatic growths to the extent that such growths cause nuisance or adversely affect the water for beneficial uses."

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

Samples were collected at East Walker River, at CA/NV state line (630EWK001).

Temporal Representation:

Samples were collected on August and November 2007.

Environmental Conditions:

QAPP Information:

2002 QAMP (Quality Assurance Management Plan) for the State of California's Surface Water Ambient Monitoring Program

QAPP Information Reference(s):

Quality Assurance Management Plan for the State of California's Surface Water Ambient Monitoring Program. Sacramento, CA. State Water Resources Control Board. SWAMP. December 2002 (1st version)

Line of Evidence (LOE) for Decision ID 169156, Nitrogen	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

96960

Pollutant:

Total Nitrogen as N

LOE Subgroup:

Pollutant-Water

Matrix:

Water

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 were collected by the Nevada Department of Environmental Protection at one site on the East Fork Walker River at the state line (21NEV1_WQX-NV09-301-EF-001) between 2011 and 2013. Concentrations in the raw data ranged from 0.4 to 1.1 mg/L. Three annual averages were computed and all of them exceeded the water quality objective.

Data Reference:

Water quality data for federal, state, and tribal agencies submitted through the US EPA STorage and RETrival (STORET) database for the 2018 listing cycle.

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

The site specific objective for total nitrogen in the East Walker River, as referenced in the Lahontan Basin Plan table 3-15, is an annual average concentration not to exceed 0.50 mg/L. While this objective is written to apply to waters upstream of Bridgeport Reservoir, it is being used to assess the waters downstream of the reservoir in recognition of the East Walker River as an interstate water which provides critical water resources to western Nevada.

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

Data were collected by the Nevada Department of Environmental Protection from one location (21NEV1_WQX-NV09-301-EF-001) located near the CA/NV state boundary.

Temporal Representation:

Data were collected between March 2011 and October 2013 on an irregular basis.

Environmental Conditions:

QAPP Information:

These are data from the US EPA STorage and RETrival (STORET) database that do not require a QAPP.

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 169156, Nitrogen	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

343137

Pollutant:

Total Nitrogen as N

LOE Subgroup:

Pollutant-Water

Matrix:

Water

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 SWAMP Perennial Stream Surveys data to determine beneficial use support and results are as follows:
1 of 1 samples exceeded the water quality threshold for Nitrogen, Total

Data Reference:

Benthic, Field, Habitat, WQ from the Surface Water Ambient Monitoring Program for the 2026 Integrated Report in Region 6

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

The Basin Plan objective for Nitrogen, Total in this water body is 0.5 (mg/L), (as a Mean).

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: East Walker River ~1mi below Murphy Pond (630PS0163)

Temporal Representation:

The samples were collected between the dates of 2015-06-15 and 2015-06-15

Environmental Conditions:

QAPP Information:

Generic SWAMP QAPrP

QAPP Information Reference(s):

Benthic, Field, Habitat, Tissue, Toxicity, WQ from the Surface Water Ambient Monitoring Program for the 2026 Integrated Report in Region 6

Line of Evidence (LOE) for Decision ID 169156, Nitrogen	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

343055

Pollutant:

Total Nitrogen as N

LOE Subgroup:

Pollutant-Water

Matrix:

Water

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 SWAMP RWB6 Monitoring data to determine beneficial use support and results are as follows:
1 of 4 samples exceeded the water quality threshold for Nitrogen, Total

Data Reference:

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

The Basin Plan objective for Nitrogen, Total in this water body is 0.5 (mg/L), (as a Mean).

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: East Walker River, at CA/NV state line (630EWK001)

Temporal Representation:

The samples were collected between the dates of 2016-03-17 and 2021-11-23

Environmental Conditions:

QAPP Information:

Generic SWAMP QAPrP

QAPP Information Reference(s):

Water Quality Assessment Data for the 2018 solicitation cycle submitted through CEDEN for the SWAMP RWB6 Monitoring (tissue and water).

Line of Evidence (LOE) for Decision ID 169156, Nitrogen	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

96895

Pollutant:

Total Nitrogen as N

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data were collected as part of regional routine SWAMP monitoring. Data were collected from one site between 2010 and 2015. Concentrations in the raw data ranged from 0.231 to 1.22 mg/L. Six annual averages were computed, four of which exceeded the water quality objective in 2010, 2012, 2013 and 2015.

Data Reference:

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

The site specific objective for total nitrogen in the East Walker River, as referenced in the Lahontan Basin Plan table 3-15, is an annual average concentration not to exceed 0.5 mg/L. While this objective is written to apply to waters above Bridgeport Reservoir it has been used to assess the waters below the reservoir in recognition of the East Walker River as an interstate water which provides critical water resources to western Nevada.

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

Data were collected from one location, 630EWK001, which is located just upstream of the CA/NV state boundary.

Temporal Representation:

Data were collected between October 2010 and October 2015 predominantly once per quarter.

Environmental Conditions:

QAPP Information:

Data were collected in accordance with the SWAMP QAPP.

QAPP Information Reference(s):

Quality Assurance Program Plans, Quality Assurance Project Plans, and Standard Operating Procedures for the SWAMP program


DECISION ID	161791	Region 6
East Walker River, below Bridgeport Reservoir

Pollutant:	Oxygen, Dissolved
Final Listing Decision:	Do Not Delist from 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	List on 303(d) list (TMDL required list)(2018)
Revision Status	Revised
Sources:	A Source Unknown
TMDL Priority:	Low
Impairment from Pollutant or Pollution:	Pollutant

Regional Board Conclusion:	This pollutant is being considered for removal from the CWA section 303(d) List under section 4.2 of the Listing Policy. Under this section a single line of evidence is necessary to assess listing status. Eleven lines of evidence are available in the administrative record to assess this parameter: 7 which assess dissolved oxygen concentration data and 4 which assess dissolved oxygen percent saturation data. Five of 71 samples are below the objective for minimum dissolved oxygen concentration. Eleven of 44 samples are below the objective for minimum dissolved oxygen percent saturation. Based on the readily available data and information, the weight of evidence indicates that there is sufficient justification against removing this water segment-pollutant combination from the CWA section 303(d) List. This conclusion is based on the staff findings that: 1. The data used satisfies the data quality requirements of section 6.1.4 of the Policy. 2. The data used satisfies the data quantity requirements of section 6.1.5 of the Policy. 3. Eleven of 44 samples are below the objective for minimum dissolved oxygen percent saturation and this exceeds the allowable frequency listed in Table 4.2 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 met.

Regional Board Decision Recommendation:	After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be removed from the section 303(d) list because applicable water quality standards for the pollutant are being exceeded.

State Board Review of Regional Board Conclusion and Recommendation:

State Board Decision Recommendation:

Line of Evidence (LOE) for Decision ID 161791, Oxygen, Dissolved	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

5815

Pollutant:

Dissolved oxygen saturation

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Cold Freshwater Habitat

Aquatic Life Use:

Fish Spawning

Number of Samples:

Number of Exceedances:

Data and Information Type:

Fixed station physical/chemical (conventional plus toxic pollutants)

Data Used to Assess Water Quality:

The U.S. Geological Survey measured percent saturation of dissolved oxygen quarterly between November 2003 and August 2005 under the Region 6 SWAMP program. Percent saturation in 6 measurements ranged from 88 to 119 percent. The objective was not violated.

Data Reference:

2007. SWAMP Data for the West Walker River and East Walker River Hydrologic Units

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

The Lahontan Basin Plan's narrative objective states that percent saturation shall not be depressed by more than 10 percent and minimum dissolved oxygen concentration shall not be less than 80 percent saturation.

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

One station, the East Walker River near state line, was sampled.

Temporal Representation:

Six quarterly measurements were taken between November 2003 and August 2006.

Environmental Conditions:

QAPP Information:

Data meet the quality assurance requirements of the SWAMP QAPP.

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 161791, Oxygen, Dissolved	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

44403

Pollutant:

Dissolved oxygen saturation

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

None

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 SWAMP data for East Walker River, below Bridgeport Reservoir to determine beneficial use support and results are as follows: 3 of 5 samples exceed the criterion for Oxygen, Saturation.

Data Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

The Water Quality Control Plan for the Lahontan Region's water quality objective states that the dissolved oxygen concentration shall not be less than 80 percent of saturation.

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

Data for this line of evidence for East Walker River, below Bridgeport Reservoir was collected at 1 monitoring site [ East Walker River, at CA/NV state line]

Temporal Representation:

Data was collected over the time period 8/14/2007-12/26/2007.

Environmental Conditions:

Staff is not aware of any special conditions that might affect interpretation of the data.

QAPP Information:

2002 QAMP (Quality Assurance Management Plan) for the State of California's Surface Water Ambient Monitoring Program

QAPP Information Reference(s):

Quality Assurance Management Plan for the State of California's Surface Water Ambient Monitoring Program. Sacramento, CA. State Water Resources Control Board. SWAMP. December 2002 (1st version)

Line of Evidence (LOE) for Decision ID 161791, Oxygen, Dissolved	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

339313

Pollutant:

Oxygen, Dissolved

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

None

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 SWAMP RWB6 Monitoring data for East Walker River, below Bridgeport Reservoir to determine beneficial use support and results are as follows: 0 of 19 samples exceeded the water quality threshold for Oxygen, Dissolved.

Data Reference:

Benthic, Field, Habitat, Tissue, Toxicity, WQ from the Surface Water Ambient Monitoring Program for the 2026 Integrated Report in Region 6

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

For waters with the beneficial uses of COLD, COLD with SPWN, WARM, and WARM with SPWN, the minimum dissolved oxygen concentration shall not be less than that specified in Table 3-6. (Water Quality Control Plan, Lahontan Region)

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 630EWK001 (East Walker River, at CA/NV state line).

Temporal Representation:

The samples were collected between the dates of 2016-06-22 and 2022-06-01

Environmental Conditions:

QAPP Information:

Generic SWAMP QAPrP

QAPP Information Reference(s):

WQX from the NWQMP for the 2026 Integrated Report in Region 6

Line of Evidence (LOE) for Decision ID 161791, Oxygen, Dissolved	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337707

Pollutant:

Oxygen, Dissolved

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

None

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:

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2018-01-10 and 2022-06-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633

Line of Evidence (LOE) for Decision ID 161791, Oxygen, Dissolved	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

339409

Pollutant:

Oxygen, Dissolved

LOE Subgroup:

Pollutant-Water

Matrix:

Water

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 SWAMP RWB6 Monitoring data for East Walker River, below Bridgeport Reservoir to determine beneficial use support and results are as follows: 3 of 19 samples exceeded the water quality threshold for Oxygen, Saturation.

Data Reference:

Benthic, Field, Habitat, Tissue, Toxicity, WQ from the Surface Water Ambient Monitoring Program for the 2026 Integrated Report in Region 6

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

The Water Quality Control Plan for the Lahontan Region's water quality objective states that the dissolved oxygen concentration shall not be less than 80 percent of saturation.

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 630EWK001 (East Walker River, at CA/NV state line).

Temporal Representation:

The samples were collected between the dates of 2016-06-22 and 2022-06-01

Environmental Conditions:

QAPP Information:

Generic SWAMP QAPrP

QAPP Information Reference(s):

Benthic, Field, Habitat, WQ from the Surface Water Ambient Monitoring Program for the 2026 Integrated Report in Region 6

Line of Evidence (LOE) for Decision ID 161791, Oxygen, Dissolved	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

339032

Pollutant:

Oxygen, Dissolved

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

None

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:

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 630PS0163 (East Walker River ~1mi below Murphy Pond).

Temporal Representation:

The samples were collected between the dates of 2015-06-15 and 2015-06-15

Environmental Conditions:

QAPP Information:

Generic SWAMP QAPrP

QAPP Information Reference(s):

Water Quality Assessment Data for the 2018 solicitation cycle submitted through CEDEN for the SWAMP RWB6 Monitoring (tissue and water).

Line of Evidence (LOE) for Decision ID 161791, Oxygen, Dissolved	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

130101

Pollutant:

Oxygen, Dissolved

LOE Subgroup:

Pollutant-Water

Matrix:

Water

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 SWAMP RWB6 Monitoring data for East Walker River, below Bridgeport Reservoir to determine beneficial use support and results are as follows: 5 of 15 samples exceeded the water quality standard for Oxygen, Saturation.

Data Reference:

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

The Water Quality Control Plan for the Lahontan Region's water quality objective states that the dissolved oxygen concentration shall not be less than 80 percent of saturation.

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site(s) (630EWK001)

Temporal Representation:

The samples were collected between the dates of 2010-09-13 and 2013-06-13

Environmental Conditions:

QAPP Information:

Quality Assurance Program Plan and Standard Operating Procedures for SWAMP program

QAPP Information Reference(s):

Quality Assurance Program Plans, Quality Assurance Project Plans, and Standard Operating Procedures for the SWAMP program

Line of Evidence (LOE) for Decision ID 161791, Oxygen, Dissolved	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

130019

Pollutant:

Oxygen, Dissolved

LOE Subgroup:

Pollutant-Water

Matrix:

Water

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 SWAMP RWB6 Monitoring data for East Walker River, below Bridgeport Reservoir to determine beneficial use support and results are as follows: 0 of 15 samples exceeded the water quality standard for Oxygen, Dissolved.

Data Reference:

Water Quality Assessment Data for the 2018 solicitation cycle submitted through CEDEN for the SWAMP RWB6 Monitoring (tissue and water).

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site(s) (630EWK001)

Temporal Representation:

The samples were collected between the dates of 2010-09-13 and 2013-06-13

Environmental Conditions:

QAPP Information:

Quality Assurance Program Plan and Standard Operating Procedures for SWAMP program

QAPP Information Reference(s):

Quality Assurance Program Plans, Quality Assurance Project Plans, and Standard Operating Procedures for the SWAMP program

Line of Evidence (LOE) for Decision ID 161791, Oxygen, Dissolved	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

32270

Pollutant:

Oxygen, Dissolved

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

None

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

One sample was below the 1 day minimum.

Data Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

The objective from Lahontan Basin Plan Table 3-6 with both cold and spawn beneficial uses shall not be less than a one-day minimum dissolved oxygen concentration of 8 mg/L.

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

Data were collected at the following station: 630EWK001-East Walker River, below Bridgeport Reservoir.

Temporal Representation:

Samples were collected between August and December 2007

Environmental Conditions:

QAPP Information:

2002 QAMP (Quality Assurance Management Plan) for the State of California's Surface Water Ambient Monitoring Program

QAPP Information Reference(s):

Quality Assurance Management Plan for the State of California's Surface Water Ambient Monitoring Program. Sacramento, CA. State Water Resources Control Board. SWAMP. December 2002 (1st version)

Line of Evidence (LOE) for Decision ID 161791, Oxygen, Dissolved	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

130033

Pollutant:

Oxygen, Dissolved

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

None

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 STORET data for East Walker River, below Bridgeport Reservoir to determine beneficial use support and results are as follows: 0 of 6 samples exceeded the water quality standard for Oxygen, Dissolved.

Data Reference:

Water quality data for federal, state, and tribal agencies submitted through the US EPA STorage and RETrival (STORET) database for the 2018 listing cycle.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site(s) (21NEV1_WQX-NV09-301-EF-001)

Temporal Representation:

The samples were collected between the dates of 2011-03-09 and 2012-08-07

Environmental Conditions:

QAPP Information:

QAPP not required for federal data

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 161791, Oxygen, Dissolved	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

5731

Pollutant:

Oxygen, Dissolved

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Cold Freshwater Habitat

Aquatic Life Use:

Fish Spawning

Number of Samples:

Number of Exceedances:

Data and Information Type:

Fixed station physical/chemical (conventional plus toxic pollutants)

Data Used to Assess Water Quality:

The U.S. Geological Survey measured dissolved oxygen quarterly between 2001 and 2005 under the Region 6 SWAMP program. Dissolved oxygen concentrations in 15 samples ranged from 7.1 to 12 mg/L. Four of 15 samples were below the 8 mg/L minimum concentration.

Data Reference:

2007. SWAMP Data for the West Walker River and East Walker River Hydrologic Units

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

For waters designated for the COLD and SPWN beneficial uses the 1- day minimum objective is 8 mg/L (Lahontan Basin Plan Table 3-6)

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

One station, the East Walker River near state line, was sampled.

Temporal Representation:

Fifteen quarterly samples were collected between August 2002 and August 2005.

Environmental Conditions:

QAPP Information:

Data meet the quality assurance requirements of the SWAMP QAPP.

QAPP Information Reference(s):


DECISION ID	163605	Region 6
East Walker River, below Bridgeport Reservoir

Pollutant:	Phosphorus
Final Listing Decision:	Do Not Delist from 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	List on 303(d) list (TMDL required list)(2018)
Revision Status	Revised
Sources:	A Source Unknown
TMDL Priority:	Low
Impairment from Pollutant or Pollution:	Pollutant

Regional Board Conclusion:	This pollutant is being considered for 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. 11 lines of evidence are available in the administrative record to assess pollutant. 17 of the 43 samples exceed the site-specific objective. Based on the readily available data and information, the weight of evidence indicates that there is sufficient justification against removing this water segment-pollutant combination from the CWA section 303(d) List. This conclusion is based on the staff findings that: 1. The data used satisfies the data quality requirements of section 6.1.4 of the Policy. 2. The data used satisfies the data quantity requirements of section 6.1.5 of the Policy. 3. 7 of the 43 samples exceed the site-specific objective and this exceeds 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 met.

Regional Board Decision Recommendation:	After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be removed from the section 303(d) list because applicable water quality standards for the pollutant are being exceeded.

State Board Review of Regional Board Conclusion and Recommendation:

State Board Decision Recommendation:

Line of Evidence (LOE) for Decision ID 163605, Phosphorus	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

343577

Pollutant:

Phosphorus

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Not Recorded

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 Nevada Division of Environmental Protection data to determine beneficial use support and results are as follows:
2 of 3 samples exceeded the water quality threshold for Phosphorus as P

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The Basin Plan objective for Phosphorus as P in this water body is 0.06 (mg/L), (as a Mean).

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: East Fork Walker River @ Stateline (21NEV1_WQX-NV09-301-EF-001)

Temporal Representation:

The samples were collected between the dates of 2018-04-04 and 2022-02-08

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633

Line of Evidence (LOE) for Decision ID 163605, Phosphorus	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

5049

Pollutant:

Phosphorus

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

Fixed station physical/chemical (conventional plus toxic pollutants)

Data Used to Assess Water Quality:

The U.S. Geological survey sampled the East Walker River under the Region 6 SWAMP program, at quarterly intervals between 2001 and 2005. Concentrations of total P in 15 samples ranged from 0.036 to 0.37 mg/L. No biological data are available for assessment of compliance with the objective for biostimulatory substances.

Data Reference:

2007. SWAMP Data for the West Walker River and East Walker River Hydrologic Units

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

There are no site specific numerical objectives for phosphorus for this segment. The regionwide narrative objective for biostimulatory substances states:

"Waters shall not contain biostimulatory substances in concentrations that promote aquatic growths to the extent that such growths cause nuisance or adversely affect the water for beneficial uses."

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

One station, East Walker River at the California-Nevada State Line, was sampled.

Temporal Representation:

Fifteen quarterly samples were taken between 2001 and 2005.

Environmental Conditions:

QAPP Information:

Data meet the quality assurance requirements of the SWAMP QAPP.

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 163605, Phosphorus	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

96959

Pollutant:

Phosphorus

LOE Subgroup:

Pollutant-Water

Matrix:

Water

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 were collected by the Nevada Department of Environmental Protection at one site on the East Fork Walker River at the state line (21NEV1_WQX-NV09-301-EF-001) between 2011 and 2013. Concentrations in the raw data ranged from 0.03 to 0.26 mg/L. Three annual averages were computed and all of them exceeded the water quality objective.

Data Reference:

Water quality data for federal, state, and tribal agencies submitted through the US EPA STorage and RETrival (STORET) database for the 2018 listing cycle.

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

The site specific objective for total phosphorous in the East Walker River, as referenced in the Lahontan Basin Plan table 3-15, is an annual average concentration not to exceed 0.06 mg/L. While this objective is written to apply to waters upstream of Bridgeport Reservoir, it is being used to assess the waters downstream of the reservoir in recognition of the East Walker River as an interstate water which provides critical water resources to western Nevada.

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

Data were collected by the Nevada Department of Environmental Protection from one location (21NEV1_WQX-NV09-301-EF-001) located near the CA/NV state boundary.

Temporal Representation:

Data were collected between March 2011 and October 2013 on an irregular basis.

Environmental Conditions:

QAPP Information:

These are data from the US EPA STorage and RETrival (STORET) database that do not require a QAPP.

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 163605, Phosphorus	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

27683

Pollutant:

Phosphorus

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

Fixed station physical/chemical (conventional plus toxic pollutants)

Data Used to Assess Water Quality:

The U.S. Geological Survey collected monthly samples at the gaging station below Bridgeport Reservoir between April 2000 and February 2001. The mean concentrations of these 11 samples was 0.083 mg/L. The mean annual cocentration in nine USGS samples for 2000 was 0.094 mg/L.

Data Reference:

Administrative Record of Lahontan RWQCB's 2001-2002 Section 303(d) List Update Process Resolution R6T-2002-0002

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The site-specific water quality objective used in the 2002 listing of the East Walker River included an annual mean total phosphorus concentration of 0.06 mg/L and a 90th percentile value of 0.10 mg/L. This objective actually applies to a station upstream of Bridgeport Reservoir.

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

Samples were collected at the USGS gaging station below Bridgeport Reservoir.

Temporal Representation:

Eleven samples were collected monthly between April 2000 and February 2001.

Environmental Conditions:

QAPP Information:

Sampling and analysis were done according to the SWAMP QAPP. However, in July 2009 an error was discovered in the QAPP related to holding times for total phosphorus samples that affects the validity of data for the Lahontan Region The holding time for samples that are not acid-preserved.should be 48 hours rather than 28 days as indicated in the QAPP. "Low level" phosphorus analyses, without acid preservation, are used in the Lahontan Region's SWAMP program. .

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 163605, Phosphorus	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

34530

Pollutant:

Phosphorus

LOE Subgroup:

Pollutant-Water

Matrix:

Water

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:

The annual average for 2007 exceeds the water quality objective for Total Phosphorus. Total Phosphorus was calculated by summing Orthophosphate as P and Phosphorus as P data. Phosphorus as P data were averaged when they were collected on the same day. 2 pairs were summed and then averaged for 2007 before comparing with the Total Phosphorus annual average objective.

Data Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

Table 3-15 of the Basin Plan states that the water quality objective for Total P for East Walker River below Bridgeport Reservoir is 0.06 mg/L as an annual average.

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

Samples were collected at East Walker River, at CA/NV state line (630EWK001).

Temporal Representation:

Samples were collected on August and November 2007.

Environmental Conditions:

QAPP Information:

2002 QAMP (Quality Assurance Management Plan) for the State of California's Surface Water Ambient Monitoring Program

QAPP Information Reference(s):

Quality Assurance Management Plan for the State of California's Surface Water Ambient Monitoring Program. Sacramento, CA. State Water Resources Control Board. SWAMP. December 2002 (1st version)

Line of Evidence (LOE) for Decision ID 163605, Phosphorus	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

96896

Pollutant:

Phosphorus

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data were collected as part of regional routine SWAMP monitoring. Data were collected from one site between 2010 and 2015. Concentrations in the raw data ranged from 0.005 to 0.104 mg/L. Six annual averages were computed, none of which exceeded the water quality objective.

Data Reference:

Water Quality Assessment Data for the 2018 solicitation cycle submitted through CEDEN for the SWAMP RWB6 Monitoring (tissue and water).

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

The site specific objective for total phosphorous in the East Walker River, as referenced in the Lahontan Basin Plan table 3-15, is an annual average concentration not to exceed 0.06 mg/L. While this objective is written to apply to waters above Bridgeport Reservoir it has been used to assess the waters below the reservoir in recognition of the East Walker River as an interstate water which provides critical water resources to western Nevada.

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

Data were collected from one location, 630EWK001, which is located just upstream of the CA/NV state boundary.

Temporal Representation:

Data were collected between October 2010 and October 2015 predominantly once per quarter.

Environmental Conditions:

QAPP Information:

Data were collected in accordance with the SWAMP QAPP.

QAPP Information Reference(s):

Quality Assurance Program Plans, Quality Assurance Project Plans, and Standard Operating Procedures for the SWAMP program

Line of Evidence (LOE) for Decision ID 163605, Phosphorus	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

343578

Pollutant:

Phosphorus

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Not Recorded

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 Nevada Division of Environmental Protection data to determine beneficial use support and results are as follows:
0 of 1 samples exceeded the water quality threshold for Phosphorus as P

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The Basin Plan objective for Phosphorus as P in this water body is 0.06 (mg/L), (as a Mean).

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: East Fork Walker River @ Stateline (21NEV1_WQX-NV09-301-EF-001)

Temporal Representation:

The samples were collected between the dates of 2018-04-04 and 2022-02-08

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633

Line of Evidence (LOE) for Decision ID 163605, Phosphorus	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

343217

Pollutant:

Phosphorus

LOE Subgroup:

Pollutant-Water

Matrix:

Water

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 SWAMP Perennial Stream Surveys data to determine beneficial use support and results are as follows:
1 of 1 samples exceeded the water quality threshold for Phosphorus as P

Data Reference:

Benthic, Field, Habitat, WQ from the Surface Water Ambient Monitoring Program for the 2026 Integrated Report in Region 6

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

The Basin Plan objective for Phosphorus as P in this water body is 0.06 (mg/L), (as a Mean).

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: East Walker River ~1mi below Murphy Pond (630PS0163)

Temporal Representation:

The samples were collected between the dates of 2015-06-15 and 2015-06-15

Environmental Conditions:

QAPP Information:

Generic SWAMP QAPrP

QAPP Information Reference(s):

Benthic, Field, Habitat, Tissue, Toxicity, WQ from the Surface Water Ambient Monitoring Program for the 2026 Integrated Report in Region 6

Line of Evidence (LOE) for Decision ID 163605, Phosphorus	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

343198

Pollutant:

Phosphorus

LOE Subgroup:

Pollutant-Water

Matrix:

Water

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 SWAMP RWB6 Monitoring data to determine beneficial use support and results are as follows:
5 of 5 samples exceeded the water quality threshold for Phosphorus as P

Data Reference:

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

The Basin Plan objective for Phosphorus as P in this water body is 0.06 (mg/L), (as a Mean).

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: East Walker River, at CA/NV state line (630EWK001)

Temporal Representation:

The samples were collected between the dates of 2016-03-17 and 2021-11-23

Environmental Conditions:

QAPP Information:

Generic SWAMP QAPrP

QAPP Information Reference(s):

WQX from the NWQMP for the 2026 Integrated Report in Region 6

Line of Evidence (LOE) for Decision ID 163605, Phosphorus	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

343576

Pollutant:

Phosphorus

LOE Subgroup:

Pollutant-Water

Matrix:

Water

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 Nevada Division of Environmental Protection data to determine beneficial use support and results are as follows:
1 of 3 samples exceeded the water quality threshold for Phosphorus as P

Data Reference:

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The Basin Plan objective for Phosphorus as P in this water body is 0.06 (mg/L), (as a Mean).

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: East Fork Walker River @ Stateline (21NEV1_WQX-NV09-301-EF-001)

Temporal Representation:

The samples were collected between the dates of 2018-01-10 and 2022-06-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633

Line of Evidence (LOE) for Decision ID 163605, Phosphorus	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

343670

Pollutant:

Phosphorus

LOE Subgroup:

Pollutant-Water

Matrix:

Water

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 Nevada Division of Environmental Protection data to determine beneficial use support and results are as follows:
3 of 4 samples exceeded the water quality threshold for Phosphorus as P

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The Basin Plan objective for Phosphorus as P in this water body is 0.06 (mg/L), (as a Mean).

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: East Fork Walker River @ Stateline (21NEV1_WQX-NV09-301-EF-001)

Temporal Representation:

The samples were collected between the dates of 2014-01-22 and 2017-10-03

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633


DECISION ID	161804	Region 6
East Walker River, below Bridgeport Reservoir

Pollutant:	Turbidity
Final Listing Decision:	Do Not Delist from 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	Do Not Delist from 303(d) list (TMDL required list)(2018)
Revision Status	Revised
Sources:	A Source Unknown
TMDL Priority:	Low
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 4.2 of the Listing Policy. Under this section a single line of evidence is necessary to assess listing status. 10 lines of evidence are available in the administrative record to assess this pollutant. 25 of the 105 samples exceed the MUN water quality objective (MCL). Based on the readily available data and information, the weight of evidence indicates that there is sufficient justification against removing this water segment-pollutant combination from the CWA section 303(d) List. This conclusion is based on the staff findings that: 1. The data used satisfies the data quality requirements of section 6.1.4 of the Policy. 2. The data used satisfies the data quantity requirements of section 6.1.5 of the Policy. 3. 25 of 105 samples exceeded the MUN water quality objective (MCL) and this exceeds the allowable frequency listed in Table 4.2 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 met.

Regional Board Decision Recommendation:	After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be removed from the section 303(d) list because applicable water quality standards for the pollutant are being exceeded.

State Board Review of Regional Board Conclusion and Recommendation:

State Board Decision Recommendation:

Line of Evidence (LOE) for Decision ID 161804, Turbidity	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337782

Pollutant:

Turbidity

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Not Recorded

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Water designated as MUN shall not contain concentrations of chemical constituents in excess of the maximum contaminant level (MCL) or secondary maximum contaminant level (SMCL) based upon drinking water standards specified in Title 22 of the California Code of Regulations. The Lahontan Basin Plan also has regionwide turbidity objective for other beneficial uses that states: Waters shall be free of changes in turbidity that cause nuisance or adversely affect the water for beneficial uses. Increases in turbidity shall not exceed natural levels by more than 10%.

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

California Maximum Contaminant Levels (MCLs) apply to ambient surface waters under the Lahontan Basin Plan's 'Chemical Constituents' objective. The Secondary MCL for turbidity is 5 NTU. Calculation of a numeric objective for other beneficial uses requires comparison with upstream or other background data which may not be available as part of the data used for water quality assessment.

Guideline Reference:

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

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2018-01-10 and 2022-06-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633

Line of Evidence (LOE) for Decision ID 161804, Turbidity	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

341972

Pollutant:

Turbidity

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Not Recorded

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

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

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2014-01-22 and 2017-10-03

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633

Line of Evidence (LOE) for Decision ID 161804, Turbidity	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

7718

Pollutant:

Turbidity

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

None

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

Fixed station physical/chemical (conventional plus toxic pollutants)

Data Used to Assess Water Quality:

The U.S. Geological Survey measured turbidity under the Region 6 SWAMP program at quarterly intervals between 2004 and 2005. Turbidity in 4 samples ranged from 2 to 4.2 NTRU. Since the MCL is expressed as NTU these samples cannot be used to assess compliance.

Data Reference:

2007. SWAMP Data for the West Walker River and East Walker River Hydrologic Units

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

California Maximum Contaminant Levels (MCLs) apply to ambient waters under the Lahontan Basin Plan's "Chemical Constituents" objective. The MCL for turbidity is 5 NTU.

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

One station, East Walker River at the California-Nevada State Line, was sampled.

Temporal Representation:

Four samples reported as NTRU were collected quarterly between 2004 and 2005.

Environmental Conditions:

QAPP Information:

Data meet the quality assurance requirements of the SWAMP QAPP.

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 161804, Turbidity	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

99085

Pollutant:

Turbidity

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

None

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

Water quality data for federal, state, and tribal agencies submitted through the US EPA STorage and RETrival (STORET) database for the 2018 listing cycle.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

California Maximum Contaminant Levels (MCLs) apply to ambient surface waters under the Lahontan Basin Plan's \Chemical Constituents\" objective. The Secondary MCL for turbidity is 5 NTU. Calculation of a numeric objective for other beneficial uses requires comparison with upstream or other background data which may not be available as part of the data used for water quality assessment. "

Guideline Reference:

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

Spatial Representation:

The samples were collected at 1 monitoring site(s) (21NEV1_WQX-NV09-301-EF-001)

Temporal Representation:

The samples were collected between the dates of 2011-03-09 and 2012-08-07

Environmental Conditions:

QAPP Information:

QAPP not required for federal data

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 161804, Turbidity	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

340897

Pollutant:

Turbidity

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:

Data Reference:

Benthic, Field, Habitat, WQ from the Surface Water Ambient Monitoring Program for the 2026 Integrated Report in Region 6

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

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

Spatial Representation:

The samples were collected at 1 monitoring site: 630PS0163 (East Walker River ~1mi below Murphy Pond).

Temporal Representation:

The samples were collected between the dates of 2015-06-15 and 2015-06-15

Environmental Conditions:

QAPP Information:

Generic SWAMP QAPrP

QAPP Information Reference(s):

2007. SWAMP Data for the West Walker River and East Walker River Hydrologic Units

Line of Evidence (LOE) for Decision ID 161804, Turbidity	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

5057

Pollutant:

Turbidity

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

None

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

Fixed station physical/chemical (conventional plus toxic pollutants)

Data Used to Assess Water Quality:

The U.S. Geological Survey measured turbidity under the Region 6 SWAMP program at quarterly intervals between 2001 and 2004. Turbidity in 12 samples ranged from below the detection level to 12 NTU. The MCL was exceeded in 9 of the 12 samples.

Data Reference:

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

California Maximum Contaminant Levels (MCLs) apply to ambient waters under the Lahontan Basin Plan's "Chemical Constituents" objective. The MCL for turbidity is 5 NTU.

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

One station, East Walker River at the California-Nevada State Line, was sampled.

Temporal Representation:

Twelve samples reported as NTU were collected quarterly between 2001 to 2004.

Environmental Conditions:

QAPP Information:

Data meet the quality assurance requirements of the SWAMP QAPP.

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 161804, Turbidity	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

5056

Pollutant:

Turbidity

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

None

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

Fixed station physical/chemical (conventional plus toxic pollutants)

Data Used to Assess Water Quality:

The U.S. Geological Survey measured turbidity under the Region 6 SWAMP program at quarterly intervals between 2001 and 2004. Twelve turbidity samples reported as NTU ranged from below the detection level to 12 NTU.

Data Reference:

2007. SWAMP Data for the West Walker River and East Walker River Hydrologic Units

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

The applicable objective in the Lahontan Basin Plan states: "Waters shall be free of changes in turbidity that cause nuisance or adversely affect the water for beneficial uses. Increases in turbidity shall not exceed natural levels by more than 10 percent."

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

One station, East Walker River at the California-Nevada State Line, was sampled.

Temporal Representation:

Twelve samples reported as NTU were collected quarterly from 2001 to 2004.

Environmental Conditions:

QAPP Information:

Data meet the quality assurance requirements of the SWAMP QAPP.

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 161804, Turbidity	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

7717

Pollutant:

Turbidity

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

None

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

Fixed station physical/chemical (conventional plus toxic pollutants)

Data Used to Assess Water Quality:

The U.S. Geological Survey measured turbidity under the Region 6 SWAMP program at quarterly intervals between 2004 and 2005. Turbidity in 4 samples ranged from 2 to 4.2 NTRU.

Data Reference:

2007. SWAMP Data for the West Walker River and East Walker River Hydrologic Units

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

One station, East Walker River at the California-Nevada State Line, was sampled.

Temporal Representation:

Four samples reported as NTU were collected quarterly in 2004 and 2005.

Environmental Conditions:

QAPP Information:

Data meet the quality assurance requirements of the SWAMP QAPP.

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 161804, Turbidity	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

340949

Pollutant:

Turbidity

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed SWAMP RWB6 Monitoring data for East Walker River, below Bridgeport Reservoir to determine beneficial use support and results are as follows: 3 of 18 samples exceeded the water quality threshold for Turbidity.

Data Reference:

Benthic, Field, Habitat, Tissue, Toxicity, WQ from the Surface Water Ambient Monitoring Program for the 2026 Integrated Report in Region 6

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

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

Spatial Representation:

The samples were collected at 1 monitoring site: 630EWK001 (East Walker River, at CA/NV state line).

Temporal Representation:

The samples were collected between the dates of 2016-03-17 and 2022-06-01

Environmental Conditions:

QAPP Information:

Generic SWAMP QAPrP

QAPP Information Reference(s):

Water Quality Assessment Data for the 2018 solicitation cycle submitted through CEDEN for the SWAMP RWB6 Monitoring (tissue and water).

Line of Evidence (LOE) for Decision ID 161804, Turbidity	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

96866

Pollutant:

Turbidity

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

None

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data were collected by Lahontan staff for the Surface Water Ambient Monitoring Program (SWAMP) RWB6 Monitoring program, and for a supplemental TMDL Integrated Report Special Study. The TMDL Special Study was developed by Lahontan Planning and SWAMP staff to provide additional data to the quarterly SWAMP monitoring. The purpose was to gain a better temporal understanding of levels of specific pollutants in the waterbody. To ensure the two datasets could be viably analyzed as one, the TMDL Special Study followed the same sampling protocol as SWAMP. Accordingly, the two datasets have been combined for this assessment to reflect the intended design and to best characterize conditions in the watershed. Data for the projects were collected between September 2010 and March 2017. Turbidity concentrations ranged from 1.25 to 8.67 NTU.

Data Reference:

Water Quality Assessment Data for the 2018 solicitation cycle submitted through CEDEN for the TMDL Intergrated Report Special Study.

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

California Maximum Contaminant Levels (MCLs) apply to ambient waters under the Lahontan Basin Plan's "Chemical Constituents" objective. The MCL for turbidity is 5 NTU.

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

Data were collected from one monitoring location, 630EWK001, which is located just upstream of the CA/NV stateline.

Temporal Representation:

Data were collected between September 2010 and March 2017 with predominately a twice-per-quarter frequency. More visits were made to the site in the warmer months compared with winter months.

Environmental Conditions:

QAPP Information:

Data meet the quality assurance requirements of the SWAMP QAPP.

QAPP Information Reference(s):

Quality Assurance Program Plans, Quality Assurance Project Plans, and Standard Operating Procedures for the SWAMP program


DECISION ID	161806	Region 6
East Walker River, below Bridgeport Reservoir

Pollutant:	2, 4 DB / 4-(2,4-dichlorophenoxy) butyric acid
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 161806, 2, 4 DB / 4-(2,4-dichlorophenoxy) butyric acid	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337573

Pollutant:

2, 4 DB / 4-(2,4-dichlorophenoxy) butyric acid

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Not Recorded

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:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

All waters shall be maintained free of toxic substances in concentrations that are toxic to, or that produce detrimental physiological responses in human, plant, animal, or aquatic life (Water Quality Control Plan, Lahontan Region).

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

The evaluation guideline for 2, 4 DB / 4-(2,4-dichlorophenoxy) butyric acid is the USEPA Aquatic Life Benchmark of 83 ug/L for a vascular plant (acute).

Guideline Reference:

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2019-12-16 and 2020-11-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 161806, 2, 4 DB / 4-(2,4-dichlorophenoxy) butyric acid	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337572

Pollutant:

2, 4 DB / 4-(2,4-dichlorophenoxy) butyric acid

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Not Recorded

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

The USEPA expected safe lifetime exposure limit in drinking water for 2,4-Dichlorophenoxybutyric Acid calculated using the IRIS Reference Dose, is 56 ug/L. This was calculated assuming 70 kg body weight, 2 liters/day water consumption, 20% relative source contribution from drinking water, and 0.008 mg/kg/day as the reference dose.

Guideline Reference:

IRIS Reference Summary (Various Pollutants)

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2019-12-16 and 2020-11-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633


DECISION ID	161789	Region 6
East Walker River, below Bridgeport Reservoir

Pollutant:	2,4-D (2,4-Dichlorophenoxy acetic acid)
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 161789, 2,4-D (2,4-Dichlorophenoxy acetic acid)	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337571

Pollutant:

2,4-D (2,4-Dichlorophenoxy acetic acid)

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Not Recorded

Beneficial Use:

Commercial or recreational collection of fish, shellfish, or organisms

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

The National Recommended Water Quality Criteria for 2,4-D for the protection of human health from the consumtion of organisms only is 1300 ug/L (National Recommended Water Quality Criteria 2016)

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2019-12-16 and 2020-11-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633

Line of Evidence (LOE) for Decision ID 161789, 2,4-D (2,4-Dichlorophenoxy acetic acid)	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337570

Pollutant:

2,4-D (2,4-Dichlorophenoxy acetic acid)

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Not Recorded

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:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

The evaluation guideline for Dichlorophenoxyacetic Acid, 2,4- is the USEPA Aquatic Life Benchmark of 299.2 ug/L for a vascular plant (acute).

Guideline Reference:

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2019-12-16 and 2020-11-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 161789, 2,4-D (2,4-Dichlorophenoxy acetic acid)	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337569

Pollutant:

2,4-D (2,4-Dichlorophenoxy acetic acid)

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Not Recorded

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The California Maximum Contaminant Level for 2, 4-D incorporated by reference in the Water Quality Control Plan, Lahontan Region is 70 ug/L (Water Quality Control Plan, Lahontan Region).

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2019-12-16 and 2020-11-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633


DECISION ID	161792	Region 6
East Walker River, below Bridgeport Reservoir

Pollutant:	2,4-Dinitrotoluene
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:

Line of Evidence (LOE) for Decision ID 161792, 2,4-Dinitrotoluene	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337585

Pollutant:

2,4-Dinitrotoluene

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Not Recorded

Beneficial Use:

Commercial or recreational collection of fish, shellfish, or organisms

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The 2, 4-Dinitrotoluene criteria for the protection of human health from the consumption of organisms only is 9.1 ug/L (California Toxics Rule, 2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2019-12-16 and 2019-12-16

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633

Line of Evidence (LOE) for Decision ID 161792, 2,4-Dinitrotoluene	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337586

Pollutant:

2,4-Dinitrotoluene

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Not Recorded

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The 2, 4-Dinitrotoluene criteria for the protection of human health from the consumption of water and organisms is 0.11 ug/L (California Toxics Rule, 2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2019-12-16 and 2019-12-16

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633


DECISION ID	161745	Region 6
East Walker River, below Bridgeport Reservoir

Pollutant:	Acifluorfen
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 161745, Acifluorfen	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337438

Pollutant:

Acifluorfen

LOE Subgroup:

Pollutant-Water

Matrix:

Water

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:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

The evaluation guideline for acifluorfen is the USEPA Aquatic Life Benchmark of 355 ug/L for nonvascular plants for sodium acifluorfen .

Guideline Reference:

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2019-12-16 and 2020-11-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):


DECISION ID	161817	Region 6
East Walker River, below Bridgeport Reservoir

Pollutant:	Alachlor
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 161817, Alachlor	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337439

Pollutant:

Alachlor

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:

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The California Maximum Contaminant Level for alachlor incorporated by reference in the Water Quality Control Plan, Lahontan Region is 2 ug/L (Water Quality Control Plan, Lahontan Region).

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2019-12-16 and 2020-11-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633

Line of Evidence (LOE) for Decision ID 161817, Alachlor	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337440

Pollutant:

Alachlor

LOE Subgroup:

Pollutant-Water

Matrix:

Water

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:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

The evaluation guideline for alachlor is the USEPA Aquatic Life Benchmark of 1.64 ug/L for a nonvascular plant (acute).

Guideline Reference:

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2019-12-16 and 2020-11-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):


DECISION ID	161820	Region 6
East Walker River, below Bridgeport Reservoir

Pollutant:	Aldicarb
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 161820, Aldicarb	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337441

Pollutant:

Aldicarb

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:

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

The USEPA Health Advisory for lifetime exposure to aldicarb as a drinking water level is a concentration of 0.007 mg/L.

Guideline Reference:

2018 Edition of the Drinking Water Standards and Health Advisories

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2019-12-16 and 2020-11-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633

Line of Evidence (LOE) for Decision ID 161820, Aldicarb	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337442

Pollutant:

Aldicarb

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Not Recorded

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 Nevada Division of Environmental Protection data for East Walker River, below Bridgeport Reservoir to determine beneficial use support, and the results are as follows: 0 of the 0 samples exceeded the evaluation guideline for Aldicarb. Although a total of 2 samples were collected, 2 of these samples were not included in the assessment because the laboratory data reporting limit(s) was above the water quality threshold 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:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

The evaluation guideline for aldicarb is the USEPA Aquatic Life Benchmark of 0.46 ug/L for a fish (chronic).

Guideline Reference:

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2019-12-16 and 2020-11-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 161820, Aldicarb	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337444

Pollutant:

Aldicarb

LOE Subgroup:

Pollutant-Water

Matrix:

Water

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:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

The evaluation guideline for aldicarb is the USEPA Aquatic Life Benchmark of 0.46 ug/L for a fish (chronic).

Guideline Reference:

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2019-12-16 and 2020-11-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 161820, Aldicarb	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337443

Pollutant:

Aldicarb

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Not Recorded

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

The USEPA Health Advisory for lifetime exposure to aldicarb as a drinking water level is a concentration of 0.007 mg/L.

Guideline Reference:

2018 Edition of the Drinking Water Standards and Health Advisories

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2019-12-16 and 2020-11-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633


DECISION ID	161821	Region 6
East Walker River, below Bridgeport Reservoir

Pollutant:	Aldrin
Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)(2018)
Revision Status	Revised
Impairment from Pollutant or Pollution:	Pollutant

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

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

State Board Review of Regional Board Conclusion and Recommendation:

State Board Decision Recommendation:	After review of 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 161821, Aldrin	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337445

Pollutant:

Aldrin

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed Nevada Division of Environmental Protection data for East Walker River, below Bridgeport Reservoir to determine beneficial use support, and the results are as follows: 0 of the 0 samples exceeded the evaluation guideline for Aldrin. Although a total of 2 samples were collected, 2 of these samples were not included in the assessment because the laboratory data reporting limit(s) was above the water quality threshold 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:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The aldrin criterion for the protection of human health from the consumption of water and organisms is 0.00013 ug/L (California Toxics Rule, 2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2019-12-16 and 2020-11-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633

Line of Evidence (LOE) for Decision ID 161821, Aldrin	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337446

Pollutant:

Aldrin

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:

Water Board staff assessed Nevada Division of Environmental Protection data for East Walker River, below Bridgeport Reservoir to determine beneficial use support, and the results are as follows: 0 of the 0 samples exceeded the evaluation guideline for Aldrin. Although a total of 2 samples were collected, 2 of these samples were not included in the assessment because the laboratory data reporting limit(s) was above the water quality threshold 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:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The aldrin criterion for the protection of human health from consumption of organisms only is 0.00014 ug/L (California Toxics Rule, 2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2019-12-16 and 2020-11-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633

Line of Evidence (LOE) for Decision ID 161821, Aldrin	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337447

Pollutant:

Aldrin

LOE Subgroup:

Pollutant-Water

Matrix:

Water

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:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The aldrin criterion maximum concentration (expressed as a 1-day average) to protect aquatic life in freshwater is 1.5 ug/L. The criterion of 3 ug/L provided in the California Toxics Rule is an instantaneous maximum concentration and was divided by 2 in order to better represent a criterion maximum concentration (CMC) value as specified in footnote (g) of Table (b)(1) of the California Toxics Rule (2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2019-12-16 and 2020-11-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633

Line of Evidence (LOE) for Decision ID 161821, Aldrin	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

99185

Pollutant:

Aldrin

LOE Subgroup:

Pollutant-Tissue

Matrix:

Tissue

Fraction:

Fish fillet

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 SWAMP Sportfish Rivers and Streams data for East Walker River, below Bridgeport Reservoir to determine beneficial use support and the results are as follows 0 of the 1 samples exceeded the water quality standard for Aldrin. Data were collected for 1 fish species (1 composite(s) of Sacramento Blackfish each composed of 5 fish per composite).

Data Reference:

Water Quality Assessment Data for the 2018 solicitation cycle submitted through CEDEN for SWAMP Sportfish Rivers and Streams.

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

National Academy of Science guidelines (NAS 1972) establish a maximum Aldrin concentration of 100 ug/Kg (wet weight) in tissue samples for protection of aquatic life from bioaccumulation of toxic substances.

Guideline Reference:

National Academy of Sciences. Water Quality Criteria 1972. EPA-R3-73-033. Washington, D.C.: U.S. Environmental Protection Agency

Spatial Representation:

Data was collected from 1 station(s) with the station code(s): 630EWK002.

Temporal Representation:

Data for this line of evidence were collected between 2011-08-29 and 2011-08-29

Environmental Conditions:

QAPP Information:

Quality Assurance Program Plan and Standard Operating Procedures for SWAMP program

QAPP Information Reference(s):

Quality Assurance Program Plans, Quality Assurance Project Plans, and Standard Operating Procedures for the SWAMP program


DECISION ID	161822	Region 6
East Walker River, below Bridgeport Reservoir

Pollutant:	Alkalinity as CaCO3
Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)(2018)
Revision Status	Revised
Impairment from Pollutant or Pollution:	Pollutant

Regional Board Conclusion:	This pollutant is being considered for placement on the CWA section 303(d) List under section 3.2 of the Listing Policy. Under section 3.2 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 of the 65 samples exceed the guideline for alkalinity. Based on the readily available data and information, the weight of evidence indicates that there is sufficient justification against placing this water segment-pollutant combination on the CWA section 303(d) List. This conclusion is based on the staff findings that: 1. The data used satisfies the data quality requirements of section 6.1.4 of the Policy. 2. The data used satisfies the data quantity requirements of section 6.1.5 of the Policy. 3. Zero of 65 samples exceeded the guideline and this does not exceed the allowable frequency listed in Table 3.2 of the Listing Policy. 4. Pursuant to section 3.11 of the Listing Policy, no additional data and information are available indicating that standards are not met.

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

State Board Review of Regional Board Conclusion and Recommendation:

State Board Decision Recommendation:

Line of Evidence (LOE) for Decision ID 161822, Alkalinity as CaCO3	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

98181

Pollutant:

Alkalinity as CaCO3

LOE Subgroup:

Pollutant-Water

Matrix:

Water

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 SWAMP RWB6 Monitoring data for East Walker River, below Bridgeport Reservoir to determine beneficial use support and results are as follows: 0 of 26 samples exceeded the water quality standard for Alkalinity as CaCO3.

Data Reference:

Water Quality Assessment Data for the 2018 solicitation cycle submitted through CEDEN for the SWAMP RWB6 Monitoring (tissue and water).

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

The National Recommended Water Quality Criteria for Alkalinity as CaCO3 for the protection of freshwater aquatic life is not less than 20000 ug/L. (National Recommended Water Quality Criteria 2016)

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site(s) (630EWK001)

Temporal Representation:

The samples were collected between the dates of 2010-09-13 and 2015-10-15

Environmental Conditions:

QAPP Information:

Quality Assurance Program Plan and Standard Operating Procedures for SWAMP program

QAPP Information Reference(s):

Quality Assurance Program Plans, Quality Assurance Project Plans, and Standard Operating Procedures for the SWAMP program

Line of Evidence (LOE) for Decision ID 161822, Alkalinity as CaCO3	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337849

Pollutant:

Alkalinity as CaCO3

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

None

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:

Benthic, Field, Habitat, Tissue, Toxicity, WQ from the Surface Water Ambient Monitoring Program for the 2026 Integrated Report in Region 6

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

The USEPA recommended alkalinity criterion continuous concentration (CCC) for the protection of aquatic life in freshwater is a minimum value of 20,000 ug/L (4-day average).

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 630EWK001 (East Walker River, at CA/NV state line).

Temporal Representation:

The samples were collected between the dates of 2016-03-17 and 2022-06-01

Environmental Conditions:

QAPP Information:

Generic SWAMP QAPrP

QAPP Information Reference(s):

WQX from the NWQMP for the 2026 Integrated Report in Region 6

Line of Evidence (LOE) for Decision ID 161822, Alkalinity as CaCO3	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

341010

Pollutant:

Alkalinity as CaCO3

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

None

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:

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

The USEPA recommended alkalinity criterion continuous concentration (CCC) for the protection of aquatic life in freshwater is a minimum value of 20,000 ug/L (4-day average).

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2014-01-22 and 2017-10-03

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633

Line of Evidence (LOE) for Decision ID 161822, Alkalinity as CaCO3	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

99039

Pollutant:

Alkalinity as CaCO3

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

None

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:

Water quality data for federal, state, and tribal agencies submitted through the US EPA STorage and RETrival (STORET) database for the 2018 listing cycle.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The National Recommended Water Quality Criteria for Alkalinity as CaCO3 for the protection of freshwater aquatic life is not less than 20000 ug/L. (National Recommended Water Quality Criteria 2016)

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site(s) (21NEV1_WQX-NV09-301-EF-001)

Temporal Representation:

The samples were collected between the dates of 2011-03-09 and 2012-08-07

Environmental Conditions:

QAPP Information:

QAPP not required for federal data

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 161822, Alkalinity as CaCO3	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337873

Pollutant:

Alkalinity as CaCO3

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

None

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:

Benthic, Field, Habitat, WQ from the Surface Water Ambient Monitoring Program for the 2026 Integrated Report in Region 6

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

The USEPA recommended alkalinity criterion continuous concentration (CCC) for the protection of aquatic life in freshwater is a minimum value of 20,000 ug/L (4-day average).

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 630PS0163 (East Walker River ~1mi below Murphy Pond).

Temporal Representation:

The samples were collected between the dates of 2015-06-15 and 2015-06-15

Environmental Conditions:

QAPP Information:

Generic SWAMP QAPrP

QAPP Information Reference(s):

2007. SWAMP Data for the West Walker River and East Walker River Hydrologic Units


DECISION ID	161826	Region 6
East Walker River, below Bridgeport Reservoir

Pollutant:	Aluminum
Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)(2018)
Revision Status	Revised
Impairment from Pollutant or Pollution:	Pollutant

Regional Board Conclusion:	This pollutant is being considered for 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. Nine lines of evidence are available in the administrative record to assess pollutant. 0 of the 17 samples exceeded the COLD criteria. One of 17 samples exceeds the MUN objective (secondary MCL). Based on the readily available data and information, the weight of evidence indicates that there is sufficient justification against removing this water segment-pollutant combination from the CWA section 303(d) List. This conclusion is based on the staff findings that: 1. The data used satisfies the data quality requirements of section 6.1.4 of the Policy. 2. The data used satisfies the data quantity requirements of section 6.1.5 of the Policy. 3. 0 of the 17 samples exceeded the COLD criteria. One of 17 samples exceeds the MUN objective (secondary MCL) and 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 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 161826, Aluminum	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

348111

Pollutant:

Aluminum

LOE Subgroup:

Pollutant-Water

Matrix:

Water

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:

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

The aluminum criterion for the protection of aquatic life, is pH, total hardness, and dissolved organic carbon (DOC) dependent. When total hardness or DOC data were not available, default values based on the level III ecoregions developed by U.S EPA were substituted (EPA, 2018). When pH data were not available, the median pH value for the ecoregion, a pH value from a comparable waterbody, or a pH value from a local study in the same waterbody was used as a comparable surrogate.

Guideline Reference:

Final Aquatic Life Ambient Water Quality Criteria for Aluminum. EPA-822-R-18-001. Washington, D.C.: Office of Water, USEPA.

Spatial Representation:

The samples were collected at 1 monitoring site: 630EWK001 (East Walker River at the California-Nevada State Line).

Temporal Representation:

The samples were collected between the dates of 2001-08-16 and 2002-06-28

Environmental Conditions:

QAPP Information:

Data meet the quality assurance requirements of the SWAMP QAPP.

QAPP Information Reference(s):

Quality Assurance Program Plans, Quality Assurance Project Plans, and Standard Operating Procedures for the SWAMP program

Line of Evidence (LOE) for Decision ID 161826, Aluminum	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

5065

Pollutant:

Aluminum

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

Fixed station physical/chemical (conventional plus toxic pollutants)

Data Used to Assess Water Quality:

The U.S. Geological survey sampled aluminum under the Region 6 SWAMP program in 2001 and 2002. Total recoverable aluminum concentrations in four samples ranged from 59 to 110 ug/L. The state MCLs were not exceeded.

Data Reference:

2007. SWAMP Data for the West Walker River and East Walker River Hydrologic Units

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

California Maximum Contaminant Levels apply to ambient waters under the Lahontan Basin Plan's "Chemical Constituents" objective. The primary MCL for aluminum is 1000 ug/L and the secondary MCL is 200 ug/L.

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

One station, East Walker River at the California-Nevada State Line, was sampled.

Temporal Representation:

Four quarterly samples were collected in 2001 and 2002.

Environmental Conditions:

QAPP Information:

Data meet the quality assurance requirements of the SWAMP QAPP.

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 161826, Aluminum	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337452

Pollutant:

Aluminum

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:

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The California Secondary MCL that is incorporated by reference in the Water Quality Control Plan, Lahontan Region for aluminum is 0.2 mg/L (Water Quality Control Plan, Lahontan Region).

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2018-04-04 and 2022-06-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633

Line of Evidence (LOE) for Decision ID 161826, Aluminum	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337454

Pollutant:

Aluminum

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The California Secondary MCL that is incorporated by reference in the Water Quality Control Plan, Lahontan Region for aluminum is 0.2 mg/L (Water Quality Control Plan, Lahontan Region).

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2018-04-04 and 2022-06-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633

Line of Evidence (LOE) for Decision ID 161826, Aluminum	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337455

Pollutant:

Aluminum

LOE Subgroup:

Pollutant-Water

Matrix:

Water

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:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Final Aquatic Life Ambient Water Quality Criteria for Aluminum. EPA-822-R-18-001. Washington, D.C.: Office of Water, USEPA.

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2018-04-04 and 2022-06-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633

Line of Evidence (LOE) for Decision ID 161826, Aluminum	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

348102

Pollutant:

Aluminum

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

2007. SWAMP Data for the West Walker River and East Walker River Hydrologic Units

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

The California Secondary MCL that is incorporated by reference in the Water Quality Control Plan, Lahontan Region for aluminum is 0.2 mg/L (Water Quality Control Plan, Lahontan Region).

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 630EWK001 (East Walker River at the California-Nevada State Line).

Temporal Representation:

The samples were collected between the dates of 2001-08-16 and 2002-06-28

Environmental Conditions:

QAPP Information:

Data meet the quality assurance requirements of the SWAMP QAPP.

QAPP Information Reference(s):

Quality Assurance Program Plans, Quality Assurance Project Plans, and Standard Operating Procedures for the SWAMP program

Line of Evidence (LOE) for Decision ID 161826, Aluminum	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

348110

Pollutant:

Aluminum

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

2007. SWAMP Data for the West Walker River and East Walker River Hydrologic Units

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Final Aquatic Life Ambient Water Quality Criteria for Aluminum. EPA-822-R-18-001. Washington, D.C.: Office of Water, USEPA.

Spatial Representation:

The samples were collected at 1 monitoring site: 630EWK001 (East Walker River at the California-Nevada State Line).

Temporal Representation:

The samples were collected between the dates of 2001-08-16 and 2002-06-28

Environmental Conditions:

QAPP Information:

Data meet the quality assurance requirements of the SWAMP QAPP.

QAPP Information Reference(s):

Quality Assurance Program Plans, Quality Assurance Project Plans, and Standard Operating Procedures for the SWAMP program

Line of Evidence (LOE) for Decision ID 161826, Aluminum	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337453

Pollutant:

Aluminum

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Final Aquatic Life Ambient Water Quality Criteria for Aluminum. EPA-822-R-18-001. Washington, D.C.: Office of Water, USEPA.

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2018-04-04 and 2022-06-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633

Line of Evidence (LOE) for Decision ID 161826, Aluminum	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

348114

Pollutant:

Aluminum

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:

Data Reference:

2007. SWAMP Data for the West Walker River and East Walker River Hydrologic Units

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

The California Secondary MCL that is incorporated by reference in the Water Quality Control Plan, Lahontan Region for aluminum is 0.2 mg/L (Water Quality Control Plan, Lahontan Region).

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 630EWK001 (East Walker River at the California-Nevada State Line).

Temporal Representation:

The samples were collected between the dates of 2001-08-16 and 2002-06-28

Environmental Conditions:

QAPP Information:

Data meet the quality assurance requirements of the SWAMP QAPP.

QAPP Information Reference(s):

Quality Assurance Program Plans, Quality Assurance Project Plans, and Standard Operating Procedures for the SWAMP program


DECISION ID	103814	Region 6
East Walker River, below Bridgeport Reservoir

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

Regional Board Conclusion:	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 line of evidence is available in the administrative record to assess this pollutant that consists of a single tissue sample. Zero of one samples exceed the guideline for Anatoxin-a. 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 samples exceeded the guideline 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. The readily available data and information is insufficient to determine, with the power and confidence of the Listing Policy, the applicable beneficial use support rating.

State Board Review of Regional Board Conclusion and Recommendation:

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

Line of Evidence (LOE) for Decision ID 103814, Anatoxin-A	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

99633

Pollutant:

Anatoxin-A

LOE Subgroup:

Pollutant-Tissue

Matrix:

Tissue

Fraction:

Fish fillet

Beneficial Use:

Commercial or recreational collection of fish, shellfish, or organisms

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed SWAMP Sportfish Rivers and Streams data for East Walker River, below Bridgeport Reservoir to determine beneficial use support and the results are as follows 0 of the 1 samples exceeded the water quality standard for Anatoxin-A. Data were collected for 1 fish species (1 composite(s) of Sacramento Blackfish each composed of 5 fish per composite).

Data Reference:

Water Quality Assessment Data for the 2018 solicitation cycle submitted through CEDEN for SWAMP Sportfish Rivers and Streams.

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

The 5000 ng/g wet weight action level for Anatoxin-A for edible sport fish and shellfish identifies the maximum concentration of cyanotoxins that a typical consumer (one meal per week) could ingest without exceeding the reference dose.(OEHHA 2012)

Guideline Reference:

Toxicological Summary and Suggested Action Levels to Reduce Potential Adverse Health Effects of Six Cyanotoxins

Spatial Representation:

Data was collected from 1 station(s) with the station code(s): 630EWK002.

Temporal Representation:

Data for this line of evidence were collected between 2011-08-29 and 2011-08-29

Environmental Conditions:

QAPP Information:

Quality Assurance Program Plan and Standard Operating Procedures for SWAMP program

QAPP Information Reference(s):

Quality Assurance Program Plans, Quality Assurance Project Plans, and Standard Operating Procedures for the SWAMP program


DECISION ID	161740	Region 6
East Walker River, below Bridgeport Reservoir

Pollutant:	Anthracene
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 161740, Anthracene	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337460

Pollutant:

Anthracene

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Commercial or recreational collection of fish, shellfish, or organisms

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The anthracene criterion for the protection of human health from consumption of organisms only is 110,000 ug/L (California Toxics Rule, 2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2019-12-16 and 2020-11-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633

Line of Evidence (LOE) for Decision ID 161740, Anthracene	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337461

Pollutant:

Anthracene

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:

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The anthracene criterion for the protection of human health from the consumption of water and organisms is 9,600 ug/L (California Toxics Rule, 2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2019-12-16 and 2020-11-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633


DECISION ID	161741	Region 6
East Walker River, below Bridgeport Reservoir

Pollutant:	Antimony
Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)(2018)
Revision Status	Revised
Impairment from Pollutant or Pollution:	Pollutant

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

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

State Board Review of Regional Board Conclusion and Recommendation:

State Board Decision Recommendation:	After review of 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 161741, Antimony	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

7716

Pollutant:

Antimony

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

Fixed station physical/chemical (conventional plus toxic pollutants)

Data Used to Assess Water Quality:

The U.S. Geological Survey sampled antimony under the Region 6 SWAMP program in 2001 and 2002. Four dissolved antimony samples all had concentrations below the detection limit. Per listing policy Section 6.1.5.5, the criteria are presumed to be attained.

Data Reference:

2007. SWAMP Data for the West Walker River and East Walker River Hydrologic Units

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

The USEPA Lowest Observed Effect Levels (LOEL) criteria for protection of aquatic life include an acute antimony value of 9000 ug/L, a chronic value of 1600 ug/L and a limit for toxicity to algae of 610 ug/L

Objective/Criterion Reference:

Compilation of Water Quality Goals

Objective/Criterion Reference:

Quality Criteria for Water 1986. United States Environmental Protection Agency. Office of Water. Regulations and Standards. Washington D.C. EPA 440/5-86-001.

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

One station, East Walker River at the California-Nevada State Line, was sampled.

Temporal Representation:

Four quarterly samples were collected in 2001 and 2002.

Environmental Conditions:

QAPP Information:

Data meet the quality assurance requirements of the SWAMP QAPP.

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 161741, Antimony	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

5122

Pollutant:

Antimony

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

Fixed station physical/chemical (conventional plus toxic pollutants)

Data Used to Assess Water Quality:

The U.S. Geological survey sampled antimony under the Region 6 SWAMP program in 2001 and 2002. Four total antimony samples all had concentrations below the detection limit. Per listing policy Section 6.1.5.5, the MCL and CTR standard are presumed to be attained.

Data Reference:

2007. SWAMP Data for the West Walker River and East Walker River Hydrologic Units

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

California Maximum Contaminant Levels (MCLs) apply to ambient waters under the Lahontan Basin Plan's "Chemical Constituents" objective. The California primary MCL for antimony is 6 ug/L. The California Toxics Rule water and fish consumption standard is 14 ug/L.

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

One station, East Walker River at the California-Nevada State Line, was sampled.

Temporal Representation:

Four quarterly samples were collected in 2001 and 2002.

Environmental Conditions:

QAPP Information:

Data meet the quality assurance requirements of the SWAMP QAPP.

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 161741, Antimony	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337474

Pollutant:

Antimony

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Commercial or recreational collection of fish, shellfish, or organisms

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The Antimony criterion for the protection of human health from consumption of organisms only is 4.3 mg/L (California Toxics Rule, 2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2020-12-02 and 2022-06-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633

Line of Evidence (LOE) for Decision ID 161741, Antimony	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337475

Pollutant:

Antimony

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

All waters shall be maintained free of toxic substances in concentrations which are toxic to, or which produce detrimental physiological responses in, human, plant, animal, or aquatic life (Water Quality Control Plan, Lahontan Region). The USEPA Lowest Observed Effect Levels (LOEL) criteria for protection of aquatic life include an acute antimony value of 9000 ug/L, a chronic value of 1600 ug/L and a limit for toxicity to algae of 610 ug/L . This data were compared to the most protective value of 610 ug/L.

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

The USEPA Quality Criteria for Water (Gold Book) states that for antimony toxicity to algae occurs at 610 ug/l. (USEPA, 1986)

Guideline Reference:

Quality Criteria for Water 1986. United States Environmental Protection Agency. Office of Water. Regulations and Standards. Washington D.C. EPA 440/5-86-001.

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2020-12-02 and 2022-06-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633

Line of Evidence (LOE) for Decision ID 161741, Antimony	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337476

Pollutant:

Antimony

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The California Maximum Contaminant Level for antimony incorporated by reference in the Water Quality Control Plan, Lahontan Region is 0.006 mg/L (Water Quality Control Plan, Lahontan Region).

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2020-12-02 and 2022-06-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633

Line of Evidence (LOE) for Decision ID 161741, Antimony	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337464

Pollutant:

Antimony

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Commercial or recreational collection of fish, shellfish, or organisms

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The Antimony criterion for the protection of human health from consumption of organisms only is 4.3 mg/L (California Toxics Rule, 2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2018-04-04 and 2022-06-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633

Line of Evidence (LOE) for Decision ID 161741, Antimony	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337465

Pollutant:

Antimony

LOE Subgroup:

Pollutant-Water

Matrix:

Water

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:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

The USEPA Quality Criteria for Water (Gold Book) states that for antimony toxicity to algae occurs at 610 ug/l. (USEPA, 1986)

Guideline Reference:

Quality Criteria for Water 1986. United States Environmental Protection Agency. Office of Water. Regulations and Standards. Washington D.C. EPA 440/5-86-001.

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2018-04-04 and 2022-06-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633

Line of Evidence (LOE) for Decision ID 161741, Antimony	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337466

Pollutant:

Antimony

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:

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The California Maximum Contaminant Level for antimony incorporated by reference in the Water Quality Control Plan, Lahontan Region is 0.006 mg/L (Water Quality Control Plan, Lahontan Region).

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2018-04-04 and 2022-06-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633


DECISION ID	161746	Region 6
East Walker River, below Bridgeport Reservoir

Pollutant:	Atrazine
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 161746, Atrazine	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337490

Pollutant:

Atrazine

LOE Subgroup:

Pollutant-Water

Matrix:

Water

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:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

The evaluation guideline for Atrazine is the USEPA Aquatic Life Benchmark of < 1 ug/L for a nonvascular plant (acute). The benchmark was derived from a 'less-than' value (for example, <1,500) and may underestimate toxicity.

Guideline Reference:

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2019-12-16 and 2020-11-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 161746, Atrazine	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337489

Pollutant:

Atrazine

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:

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The California Maximum Contaminant Level for atrazine incorporated by reference in the Water Quality Control Plan, Lahontan Region is 1 ug/L (Water Quality Control Plan, Lahontan Region).

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2019-12-16 and 2020-11-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633


DECISION ID	161747	Region 6
East Walker River, below Bridgeport Reservoir

Pollutant:	Barium
Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)(2018)
Revision Status	Revised
Impairment from Pollutant or Pollution:	Pollutant

Regional Board Conclusion:	This pollutant is being considered for placement on the CWA section 303(d) List under section 3.2 of the Listing Policy. Under section 3.2 a single line of evidence is necessary to assess listing status. four lines of evidence are available in the administrative record to assess this pollutant. Zero of the 17 samples exceed the MUN water quality objective (MCL) for barium. Based on the readily available data and information, the weight of evidence indicates that there is sufficient justification against placing this water segment-pollutant combination on the CWA section 303(d) List. This conclusion is based on the staff findings that: 1. The data used satisfies the data quality requirements of section 6.1.4 of the Policy. 2. The data used satisfies the data quantity requirements of section 6.1.5 of the Policy. 3. Zero of the 17 samples exceed the MUN water quality objective (MCL) for barium and this does not exceed the allowable frequency listed in Table 3.2 of the Listing Policy. 4. Pursuant to section 3.11 of the Listing Policy, no additional data and information are available indicating that standards are not met.

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

State Board Review of Regional Board Conclusion and Recommendation:

State Board Decision Recommendation:

Line of Evidence (LOE) for Decision ID 161747, Barium	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

341160

Pollutant:

Barium

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:

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The California Maximum Contaminant Level for barium incorporated by reference in the Water Quality Control Plan, Lahontan Region is 1 mg/L.

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2014-05-12 and 2017-10-03

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633

Line of Evidence (LOE) for Decision ID 161747, Barium	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337495

Pollutant:

Barium

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The California Maximum Contaminant Level for barium incorporated by reference in the Water Quality Control Plan, Lahontan Region is 1 mg/L.

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2020-12-02 and 2022-06-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633

Line of Evidence (LOE) for Decision ID 161747, Barium	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337496

Pollutant:

Barium

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:

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The California Maximum Contaminant Level for barium incorporated by reference in the Water Quality Control Plan, Lahontan Region is 1 mg/L.

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2018-04-04 and 2022-06-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633

Line of Evidence (LOE) for Decision ID 161747, Barium	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

98997

Pollutant:

Barium

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed STORET data for East Walker River, below Bridgeport Reservoir to determine beneficial use support and results are as follows: 0 of 3 samples exceeded the water quality standard for Barium.

Data Reference:

Water quality data for federal, state, and tribal agencies submitted through the US EPA STorage and RETrival (STORET) database for the 2018 listing cycle.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The California Maximum Contaminant Level for barium incorporated by reference in the Water Quality Control Plan, Lahontan Region is 1 mg/L.

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site(s) (21NEV1_WQX-NV09-301-EF-001)

Temporal Representation:

The samples were collected between the dates of 2011-03-09 and 2012-08-07

Environmental Conditions:

QAPP Information:

QAPP not required for federal data

QAPP Information Reference(s):

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


DECISION ID	161807	Region 6
East Walker River, below Bridgeport Reservoir

Pollutant:	Bentazon
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 161807, Bentazon	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337497

Pollutant:

Bentazon

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:

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The California Maximum Contaminant Level for Bentazon incorporated by reference in the Water Quality Control Plan, Lahontan Region is 18 ug/L (Water Quality Control Plan, Lahontan Region).

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2019-12-16 and 2020-11-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633

Line of Evidence (LOE) for Decision ID 161807, Bentazon	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337498

Pollutant:

Bentazon

LOE Subgroup:

Pollutant-Water

Matrix:

Water

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:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

The evaluation guideline for Bentazon is the USEPA Aquatic Life Benchmark of 4,500 ug/L for a nonvascular plant (acute).

Guideline Reference:

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2019-12-16 and 2020-11-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):


DECISION ID	171289	Region 6
East Walker River, below Bridgeport Reservoir

Pollutant:	Benthic Community Effects
Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)(2018)
Revision Status	Revised
Impairment from Pollutant or Pollution:	Pollutant

Regional Board Conclusion:	Benthic Community Effects are being considered for placement on the CWA section 303(d) List under sections 3.9 of the Listing Policy. Under section 3.9, additional lines of evidence (LOEs) associating the Benthic Community Effects decision with a water or sediment concentration of pollutants other than benthic-macroinvertebrate bioassessment or habitat assessment LOEs are necessary to place a water body on the 303(d) List for Benthic Community Effects. Two lines of evidence evaluating benthic-macroinvertebrate bioassessment data are available in the administrative record to assess this indicator. Zero of two benthic-macroinvertebrate samples exceed the California Stream Condition Index (CSCI) impairment threshold. The available information indicates that the waterbody is likely unimpaired for Benthic Community Effects and therefore no other pollutant LOEs need be associated with this decision at this time. However, a minimum of two benthic-macroinvertebrate samples are needed to fully assess listing status. Based on the readily available data and information, the weight of evidence indicates that there is insufficient information to justify placement of Benthic Community Effects in this waterbody segment on the CWA section 303(d) List. This conclusion is based on the staff findings that: 1. The data used satisfies the data quality requirements of section 6.1.4 of the Policy. 2. The data used satisfies the data quantity requirements of section 6.1.5 of the Policy. 3. Zero of two benthic-macroinvertebrate bioassessment samples had CSCI scores below 0.79. Therefore, this water body is not exceeding the water quality threshold for the protection of the COLD beneficial use. However, a minimum of two benthic-macroinvertebrate samples are needed to fully assess listing status. 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 171289, Benthic Community Effects	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

96350

Pollutant:

Benthic-Macroinvertebrate Bioassessments

LOE Subgroup:

Population/Community Degradation

Matrix:

Water

Fraction:

None

Beneficial Use:

Cold Freshwater Habitat

Aquatic Life Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

Benthic macroinvertebrate surveys

Data Used to Assess Water Quality:

The site had a CSCI score of 0.83583581. This score indicates that this site is supporting aquatic life beneficial uses and that the water quality objective is met.

Data Reference:

Water Quality Assessment Data for the 2018 solicitation cycle submitted through CEDEN for the SWAMP Perennial Stream Surveys.

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

All waters shall be maintained free of toxic substances in concentrations that are lethal to or that produce significant alterations in population or community ecology or receiving water biota. In addition, the health and life history characteristics of aquatic organisms in waters affected by controllable water quality factors shall not differ significantly from those for the same waters in areas unaffected by controllable water quality factors.

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

The California Stream Condition Index (CSCI) is a biological scoring tool that helps aquatic resource managers translate complex data about benthic macroinvertebrates found living in a stream into an overall measure of stream health. The CSCI score is calculated by comparing the expected condition with actual (observed) results (Rhen, A.C. et al., 2015). CSCI scores range from 0 (highly degraded) to greater than 1 (equivalent to reference). CSCI scoring of biological condition are as follows (per the scientific paper supporting the development of the CSCI scoring tool): greater than or equal to 0.92 = likely intact condition, 0.91 to 0.80 = possibly altered condition, 0.79 to 0.63 = likely altered condition, less than or equal to 0.62 = very likely altered condition. Sites with scores below 0.79 are considered to have exceeded the water quality objective for the aquatic life beneficial use.

Guideline Reference:

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

Spatial Representation:

Samples collected at site 630PS0163.

Temporal Representation:

Sample collected on 6/15/2015.

Environmental Conditions:

QAPP Information:

QAPP for SWAMP Perennial Stream Surveys

QAPP Information Reference(s):

Quality Assurance Program Plans, Quality Assurance Project Plans, and Standard Operating Procedures for the SWAMP program

Line of Evidence (LOE) for Decision ID 171289, Benthic Community Effects	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

352740

Pollutant:

Benthic-Macroinvertebrate Bioassessments

LOE Subgroup:

Population/Community Degradation

Matrix:

Water

Fraction:

None

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

Benthic macroinvertebrate surveys

Data Used to Assess Water Quality:

Water Board staff assessed data for 630PS0163 to determine beneficial use support and the results are as follows: 0 of 1 samples exceeded the water quality standard. CSCI scores were from 0.861201591 to 0.861201591 .

Data Reference:

Benthic, Field, Habitat, WQ from the Surface Water Ambient Monitoring Program for the 2026 Integrated Report in Region 6

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

All waters shall be maintained free of toxic substances in concentrations that are toxic to, or that produce detrimental physiological responses in, human, plant, animal, or aquatic life. (Lahontan Basin Plan)

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

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

Spatial Representation:

The samples were collected at 1 monitoring site: 630PS0163 (East Walker River ~1mi below Murphy Pond).

Temporal Representation:

Samples were collected from 2015-06-15 to 2015-06-15.

Environmental Conditions:

QAPP Information:

Generic SWAMP QAPrP

QAPP Information Reference(s):

WQX from the NWQMP for the 2026 Integrated Report in Region 6


DECISION ID	161748	Region 6
East Walker River, below Bridgeport Reservoir

Pollutant:	Benzo(a)pyrene
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 161748, Benzo(a)pyrene	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337500

Pollutant:

Benzo(a)pyrene

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Not Recorded

Beneficial Use:

Commercial or recreational collection of fish, shellfish, or organisms

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The benzo(a)pyrene criterion for the protection of human health from consumption of organisms only is 0.049 ug/L (California Toxics Rule, 2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2019-12-16 and 2020-11-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633

Line of Evidence (LOE) for Decision ID 161748, Benzo(a)pyrene	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337499

Pollutant:

Benzo(a)pyrene

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Not Recorded

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed Nevada Division of Environmental Protection data for East Walker River, below Bridgeport Reservoir to determine beneficial use support, and the results are as follows: 0 of the 0 samples exceeded the evaluation guideline for Benzo(a)pyrene. Although a total of 2 samples were collected, 2 of these samples were not included in the assessment because the laboratory data reporting limit(s) was above the water quality threshold 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:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The benzo(a)pyrene criterion for the protection of human health from the consumption of water and organisms is 0.0044 ug/L (California Toxics Rule, 2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2019-12-16 and 2020-11-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633


DECISION ID	161749	Region 6
East Walker River, below Bridgeport Reservoir

Pollutant:	Benzo[b]fluoranthene
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 161749, Benzo[b]fluoranthene	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337502

Pollutant:

Benzo[b]fluoranthene

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Not Recorded

Beneficial Use:

Commercial or recreational collection of fish, shellfish, or organisms

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The Benzo(b)fluoranthene criterion for the protection of human health from consumption of organisms only is 0.049 ug/L (California Toxics Rule, 2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2019-12-16 and 2020-11-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633

Line of Evidence (LOE) for Decision ID 161749, Benzo[b]fluoranthene	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337501

Pollutant:

Benzo[b]fluoranthene

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Not Recorded

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed Nevada Division of Environmental Protection data for East Walker River, below Bridgeport Reservoir to determine beneficial use support, and the results are as follows: 0 of the 0 samples exceeded the evaluation guideline for Benzo(b)fluoranthene. Although a total of 2 samples were collected, 2 of these samples were not included in the assessment because the laboratory data reporting limit(s) was above the water quality threshold 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:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The Benzo(b)Fluoranthene criterion for the protection of human health from the consumption of water and organisms is 0.0044 ug/L (California Toxics Rule, 2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2019-12-16 and 2020-11-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633


DECISION ID	161750	Region 6
East Walker River, below Bridgeport Reservoir

Pollutant:	Benzo[k]fluoranthene
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 161750, Benzo[k]fluoranthene	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337503

Pollutant:

Benzo[k]fluoranthene

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Not Recorded

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed Nevada Division of Environmental Protection data for East Walker River, below Bridgeport Reservoir to determine beneficial use support, and the results are as follows: 0 of the 0 samples exceeded the evaluation guideline for Benzo(k)fluoranthene. Although a total of 2 samples were collected, 2 of these samples were not included in the assessment because the laboratory data reporting limit(s) was above the water quality threshold 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:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The Benzo(k)Fluoranthene criterion for the protection of human health from the consumption of water and organisms is 0.0044 ug/L (California Toxics Rule, 2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2019-12-16 and 2020-11-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633

Line of Evidence (LOE) for Decision ID 161750, Benzo[k]fluoranthene	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337504

Pollutant:

Benzo[k]fluoranthene

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Not Recorded

Beneficial Use:

Commercial or recreational collection of fish, shellfish, or organisms

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The Benzo(k)Fluoranthene criterion for the protection of human health from consumption of organisms only is 0.049 ug/L (California Toxics Rule, 2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2019-12-16 and 2020-11-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633


DECISION ID	161751	Region 6
East Walker River, below Bridgeport Reservoir

Pollutant:	Beryllium
Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)(2018)
Revision Status	Revised
Impairment from Pollutant or Pollution:	Pollutant

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

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

State Board Review of Regional Board Conclusion and Recommendation:

State Board Decision Recommendation:	After review of 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 161751, Beryllium	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337515

Pollutant:

Beryllium

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:

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The California Maximum Contaminant Level for beryllium incorporated by reference in the Water Quality Control Plan, Lahontan Region is 0.004 mg/L.

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2018-04-04 and 2022-06-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633

Line of Evidence (LOE) for Decision ID 161751, Beryllium	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337507

Pollutant:

Beryllium

LOE Subgroup:

Pollutant-Water

Matrix:

Water

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:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

The Gold Book states that beryllium chronic toxicity to freshwater aquatic life occur at concentrations as low as 5.3 ug/L.

Guideline Reference:

Quality Criteria for Water 1986. United States Environmental Protection Agency. Office of Water. Regulations and Standards. Washington D.C. EPA 440/5-86-001.

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2018-04-04 and 2022-06-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633

Line of Evidence (LOE) for Decision ID 161751, Beryllium	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337510

Pollutant:

Beryllium

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The California Maximum Contaminant Level for beryllium incorporated by reference in the Water Quality Control Plan, Lahontan Region is 0.004 mg/L.

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2020-12-02 and 2022-06-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633

Line of Evidence (LOE) for Decision ID 161751, Beryllium	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337509

Pollutant:

Beryllium

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

The Gold Book states that beryllium chronic toxicity to freshwater aquatic life occur at concentrations as low as 5.3 ug/L.

Guideline Reference:

Quality Criteria for Water 1986. United States Environmental Protection Agency. Office of Water. Regulations and Standards. Washington D.C. EPA 440/5-86-001.

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2020-12-02 and 2022-06-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633

Line of Evidence (LOE) for Decision ID 161751, Beryllium	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

5068

Pollutant:

Beryllium

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

Fixed station physical/chemical (conventional plus toxic pollutants)

Data Used to Assess Water Quality:

The U.S. Geological Survey sampled beryllium under the Region 6 SWAMP program in 2001 and 2002. Four total recoverable beryllium samples had reported concentrations less than the detection limit. Per listing policy Section 6.1.5.5, the MCL is presumed to be attained.

Data Reference:

2007. SWAMP Data for the West Walker River and East Walker River Hydrologic Units

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

California Maximum Contaminant Levels (MCLs) apply to ambient waters under the Lahontan Basin Plan's "Chemical Constituents" objective. The MCL for beryllium is 4 ug/L.

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

One station, East Walker River at the California-Nevada State Line, was sampled.

Temporal Representation:

Four quarterly samples were collected in 2001 and 2002.

Environmental Conditions:

QAPP Information:

Data meet the quality assurance requirements of the SWAMP QAPP.

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 161751, Beryllium	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

5763

Pollutant:

Beryllium

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

Fixed station physical/chemical (conventional plus toxic pollutants)

Data Used to Assess Water Quality:

The U.S. Geological Survey sampled beryllium quarterly in the East Walker River under the Region 6 SWAMP program in 2001 and 2002. Four dissolved beryllium samples had reported concentrations below the detection level. Per listing policy Section 6.1.5.5, the objective is presumed to be attained.

Data Reference:

2007. SWAMP Data for the West Walker River and East Walker River Hydrologic Units

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

The U.S. Environmental Protection Agency's (USEPA's) freshwater aquatic life criteria for beryllium are as follows: acute (1 hour average) criterion = 130 ug/L; chronic (4 day average) criterion = 5.3 ug/L.

Objective/Criterion Reference:

2007. SWAMP Data for the West Walker River and East Walker River Hydrologic Units

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

One station, East Walker River at the California-Nevada State Line, was sampled.

Temporal Representation:

Four quarterly samples were collected in 2001 and 2002.

Environmental Conditions:

QAPP Information:

Data meet the quality assurance requirements of the SWAMP QAPP.

QAPP Information Reference(s):


DECISION ID	161752	Region 6
East Walker River, below Bridgeport Reservoir

Pollutant:	Bis(2ethylhexyl)phthalate (DEHP)
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 161752, Bis(2ethylhexyl)phthalate (DEHP)	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337517

Pollutant:

Bis(2ethylhexyl)phthalate (DEHP)

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Not Recorded

Beneficial Use:

Commercial or recreational collection of fish, shellfish, or organisms

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The bis(2-ethylhexyl)phthalate criteria for the protection of human health from consumption of organisms only is 5.9 ug/L (California Toxics Rule, 2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2019-12-16 and 2020-11-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633

Line of Evidence (LOE) for Decision ID 161752, Bis(2ethylhexyl)phthalate (DEHP)	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337518

Pollutant:

Bis(2ethylhexyl)phthalate (DEHP)

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Not Recorded

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The bis(2-Ethylhexyl)phthalate criteria for the protection of human health from the consumption of water and organisms is 1.8 ug/L (California Toxics Rule, 2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2019-12-16 and 2020-11-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633


DECISION ID	163603	Region 6
East Walker River, below Bridgeport Reservoir

Pollutant:	Boron
Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)(2018)
Revision Status	Revised
Impairment from Pollutant or Pollution:	Pollutant

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

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

State Board Review of Regional Board Conclusion and Recommendation:

State Board Decision Recommendation:	After review of 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 163603, Boron	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

7686

Pollutant:

Boron

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

Fixed station physical/chemical (conventional plus toxic pollutants)

Data Used to Assess Water Quality:

The U.S. Geological Survey sampled boron under the Region 6 SWAMP program, at quarterly intervals between 2002 and 2005. Boron concentrations in 9 samples ranged from 39 to 178 ug/L. The criterion was not exceeded.

Data Reference:

2007. SWAMP Data for the West Walker River and East Walker River Hydrologic Units

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

The California State Notification Level criterion for boron is 1000 ug/L.

Objective/Criterion Reference:

Drinking Water Notification and Response Levels: An Overview

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

One station, East Walker River at the California-Nevada State Line, was sampled.

Temporal Representation:

Nine quarterly samples were collected between 2002 and 2005.

Environmental Conditions:

QAPP Information:

Data meet the quality assurance requirements of the SWAMP QAPP.

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 163603, Boron	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

343542

Pollutant:

Boron

LOE Subgroup:

Pollutant-Water

Matrix:

Water

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 Nevada Division of Environmental Protection data to determine beneficial use support and results are as follows:
0 of 3 samples exceeded the water quality threshold for Boron

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The Basin Plan objective for Boron in this water body is 0.12 (mg/L), (as a Mean).

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: East Fork Walker River @ Stateline (21NEV1_WQX-NV09-301-EF-001)

Temporal Representation:

The samples were collected between the dates of 2018-04-04 and 2022-06-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633

Line of Evidence (LOE) for Decision ID 163603, Boron	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

343605

Pollutant:

Boron

LOE Subgroup:

Pollutant-Water

Matrix:

Water

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:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The Basin Plan objective for Boron in this water body is 0.12 (mg/L), (as a Mean).

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: East Fork Walker River @ Stateline (21NEV1_WQX-NV09-301-EF-001)

Temporal Representation:

The samples were collected between the dates of 2014-05-12 and 2017-03-14

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633

Line of Evidence (LOE) for Decision ID 163603, Boron	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

343545

Pollutant:

Boron

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The Basin Plan objective for Boron in this water body is 0.12 (mg/L), (as a Mean).

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: East Fork Walker River @ Stateline (21NEV1_WQX-NV09-301-EF-001)

Temporal Representation:

The samples were collected between the dates of 2020-12-02 and 2022-06-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633

Line of Evidence (LOE) for Decision ID 163603, Boron	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

342706

Pollutant:

Boron

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed SWAMP RWB6 Monitoring data to determine beneficial use support and results are as follows:
0 of 6 samples exceeded the water quality threshold for Boron

Data Reference:

Benthic, Field, Habitat, Tissue, Toxicity, WQ from the Surface Water Ambient Monitoring Program for the 2026 Integrated Report in Region 6

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

The Basin Plan objective for Boron in this water body is 0.12 (mg/L), (as a Mean).

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: East Walker River, at CA/NV state line (630EWK001)

Temporal Representation:

The samples were collected between the dates of 2016-03-17 and 2021-11-23

Environmental Conditions:

QAPP Information:

Generic SWAMP QAPrP

QAPP Information Reference(s):

WQX from the NWQMP for the 2026 Integrated Report in Region 6

Line of Evidence (LOE) for Decision ID 163603, Boron	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

343543

Pollutant:

Boron

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The Basin Plan objective for Boron in this water body is 0.12 (mg/L), (as a Mean).

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: East Fork Walker River @ Stateline (21NEV1_WQX-NV09-301-EF-001)

Temporal Representation:

The samples were collected between the dates of 2020-12-02 and 2022-06-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633

Line of Evidence (LOE) for Decision ID 163603, Boron	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

96893

Pollutant:

Boron

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data were collected as part of regional routine SWAMP monitoring. Data were collected from one site between 2010 and 2015. Concentrations in the raw data ranged from 0.0324 to 0.626 mg/L. Six annual averages were computed, two of which exceeded the water quality objective in 2014 and 2015.

Data Reference:

Water Quality Assessment Data for the 2018 solicitation cycle submitted through CEDEN for the SWAMP RWB6 Monitoring (tissue and water).

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

The site specific objective for boron in the East Walker River, as referenced in the Lahontan Basin Plan table 3-15, is an annual average concentration not to exceed 0.12 mg/L. While this objective is written to apply to waters above Bridgeport Reservoir it has been used to assess the waters below the reservoir in recognition of the East Walker River as an interstate water which provides critical water resources to western Nevada.

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

Data were collected from one location, 630EWK001, which is located just upstream of the CA/NV state boundary.

Temporal Representation:

Data were collected between October 2010 and October 2015 predominantly once per quarter.

Environmental Conditions:

QAPP Information:

Data were collected in accordance with the SWAMP QAPP.

QAPP Information Reference(s):

Quality Assurance Program Plans, Quality Assurance Project Plans, and Standard Operating Procedures for the SWAMP program

Line of Evidence (LOE) for Decision ID 163603, Boron	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

32242

Pollutant:

Boron

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

None

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Zero of 2 samples exceeded the California State Notification Level criterion.

Data Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

Waters shall not contain concentrations of chemical constituents in amounts that adversely affect the water for beneficial uses.

Objective/Criterion Reference:

Evaluation Guideline:

The California State Notification Level criterion for boron is 1 mg/L.

Guideline Reference:

Drinking Water Notification Levels and Response Levels

Spatial Representation:

Data was collected at the following station: 630EWK001 East Walker River, below Bridgeport Reservoir.

Temporal Representation:

Samples were collected: 11/8/2007 8/14/2007

Environmental Conditions:

QAPP Information:

2002 QAMP (Quality Assurance Management Plan) for the State of California's Surface Water Ambient Monitoring Program

QAPP Information Reference(s):

Quality Assurance Management Plan for the State of California's Surface Water Ambient Monitoring Program. Sacramento, CA. State Water Resources Control Board. SWAMP. December 2002 (1st version)

Line of Evidence (LOE) for Decision ID 163603, Boron	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

343544

Pollutant:

Boron

LOE Subgroup:

Pollutant-Water

Matrix:

Water

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:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The Basin Plan objective for Boron in this water body is 0.12 (mg/L), (as a Mean).

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: East Fork Walker River @ Stateline (21NEV1_WQX-NV09-301-EF-001)

Temporal Representation:

The samples were collected between the dates of 2018-04-04 and 2022-06-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633


DECISION ID	161808	Region 6
East Walker River, below Bridgeport Reservoir

Pollutant:	Bromacil
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 161808, Bromacil	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337520

Pollutant:

Bromacil

LOE Subgroup:

Pollutant-Water

Matrix:

Water

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:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

The evaluation guideline for Bromacil is the USEPA Aquatic Life Benchmark of 6.8 ug/L for a nonvascular plant (acute).

Guideline Reference:

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2019-12-16 and 2020-11-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 161808, Bromacil	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337519

Pollutant:

Bromacil

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:

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

The USEPA Health Advisory for lifetime exposure to Bromacil as a drinking water level is a concentration of 0.07 mg/L

Guideline Reference:

2012 Edition of the Drinking Water Standards and Health Advisories

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2019-12-16 and 2020-11-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633


DECISION ID	161818	Region 6
East Walker River, below Bridgeport Reservoir

Pollutant:	Bromobenzene
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:

Line of Evidence (LOE) for Decision ID 161818, Bromobenzene	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337521

Pollutant:

Bromobenzene

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:

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

USEPA's Drinking Water Health Advisory exposure limit for life-time exposure to Bromobenzen is a concentration of 0.06 mg/L

Guideline Reference:

2012 Edition of the Drinking Water Standards and Health Advisories

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2020-11-30 and 2020-11-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633


DECISION ID	161819	Region 6
East Walker River, below Bridgeport Reservoir

Pollutant:	Bromochloromethane
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:

Line of Evidence (LOE) for Decision ID 161819, Bromochloromethane	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337522

Pollutant:

Bromochloromethane

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:

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

USEPA's Drinking Water Health advisory for life-time exposure to Bromochloromethane is a concentration of 0.09 mg/L

Guideline Reference:

2012 Edition of the Drinking Water Standards and Health Advisories

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2020-11-30 and 2020-11-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633


DECISION ID	161743	Region 6
East Walker River, below Bridgeport Reservoir

Pollutant:	Butachlor
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 161743, Butachlor	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337523

Pollutant:

Butachlor

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:

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

The National Academy of Sciences Health Advisory for Butachlor is the lifetime suggested no-adverse effect level of 70 ug/L (National Acadamey of Sciences Summary Report: Drinking Water and Health, 1977).

Guideline Reference:

National Academy of Sciences - Volume I Drinking Water and Health

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2019-12-16 and 2020-11-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633


DECISION ID	161753	Region 6
East Walker River, below Bridgeport Reservoir

Pollutant:	Cadmium
Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)(2018)
Revision Status	Revised
Impairment from Pollutant or Pollution:	Pollutant

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

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

State Board Review of Regional Board Conclusion and Recommendation:

State Board Decision Recommendation:	After review of 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 161753, Cadmium	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

7689

Pollutant:

Cadmium

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

Fixed station physical/chemical (conventional plus toxic pollutants)

Data Used to Assess Water Quality:

The U.S. Geological survey sampled cadmium under the Region 6 SWAMP program in 2001 ad 2002. Four total cadmium samples had reported concentrations less than the detection limit. Per listing policy Section 6.1.5.5, the CTR standards are presumed to be attained.

Data Reference:

2007. SWAMP Data for the West Walker River and East Walker River Hydrologic Units

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

The California Toxics Rule (CTR) aquatic life standards for cadmium are hardness-based. At the hardness levels measured for this station, the acute toxicity standard ranges from 2.29 to 2.75 ug/L and the chronic toxicity standard ranges from 1.45 to 1.65 ug/L.

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

One station, East Walker River at the California-Nevada State Line, was sampled.

Temporal Representation:

Four quarterly samples were collected in 2001 and 2002.

Environmental Conditions:

QAPP Information:

Data meet the quality assurance requirements of the SWAMP QAPP.

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 161753, Cadmium	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337529

Pollutant:

Cadmium

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The California Maximum Contaminant Level for cadmium incorporated by reference in the Basin Plan is 0.005 mg/L (Water Quality Control Plan, Lahontan Region).

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2018-04-04 and 2022-06-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633

Line of Evidence (LOE) for Decision ID 161753, Cadmium	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

5070

Pollutant:

Cadmium

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

Fixed station physical/chemical (conventional plus toxic pollutants)

Data Used to Assess Water Quality:

Data Reference:

2007. SWAMP Data for the West Walker River and East Walker River Hydrologic Units

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

California Maximum Contaminant Levels (MCLs) apply to ambient waters under the Lahontan Basin Plan's "Chemical Constituent" objective. The MCL for cadmium is 5 ug/L.

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

One station, East Walker River at the California-Nevada State Line, was sampled.

Temporal Representation:

Four quarterly samples were collected in 2001 and 2002.

Environmental Conditions:

QAPP Information:

Data meet the quality assurance requirements of the SWAMP QAPP.

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 161753, Cadmium	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337526

Pollutant:

Cadmium

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The dissolved cadmium criterion continuous concentration (expressed as a 4-day average) to protect aquatic life in freshwater is hardness dependent. The criterion when calculated using a default hardness of 100 mg/L is 2.2 ug/L (California Toxics Rule, 2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2018-04-04 and 2022-06-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633

Line of Evidence (LOE) for Decision ID 161753, Cadmium	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337531

Pollutant:

Cadmium

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The California Maximum Contaminant Level for cadmium incorporated by reference in the Basin Plan is 0.005 mg/L (Water Quality Control Plan, Lahontan Region).

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2018-04-04 and 2022-06-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633


DECISION ID	161754	Region 6
East Walker River, below Bridgeport Reservoir

Pollutant:	Carbaryl
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 161754, Carbaryl	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337534

Pollutant:

Carbaryl

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:

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

The USEPA Health Advisory for carbaryl as a drinking water level with a one in a million cancer risk is 0.04 mg/L.

Guideline Reference:

2012 Edition of the Drinking Water Standards and Health Advisories

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2019-12-16 and 2020-11-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633

Line of Evidence (LOE) for Decision ID 161754, Carbaryl	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337533

Pollutant:

Carbaryl

LOE Subgroup:

Pollutant-Water

Matrix:

Water

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:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

The USEPA National Recommended Aquatic Life criteria pursuant to Section 304(a) of the Clean Water Act for Carbaryl is 2.1 ug/L.

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2019-12-16 and 2020-11-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633


DECISION ID	161755	Region 6
East Walker River, below Bridgeport Reservoir

Pollutant:	Chlordane
Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)(2018)
Revision Status	Revised
Impairment from Pollutant or Pollution:	Pollutant

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

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

State Board Review of Regional Board Conclusion and Recommendation:

State Board Decision Recommendation:

Line of Evidence (LOE) for Decision ID 161755, Chlordane	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337773

Pollutant:

Chlordane

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:

Water Board staff assessed Nevada Division of Environmental Protection data for East Walker River, below Bridgeport Reservoir to determine beneficial use support, and the results are as follows: 0 of the 0 samples exceeded the evaluation guideline for Total Chlordane. Although a total of 2 samples were collected, 2 of these samples were not included in the assessment because the laboratory data reporting limit(s) was above the water quality threshold 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:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The chlordane criterion for the protection of human health from consumption of organisms only is 0.00059 ug/L (California Toxics Rule, 2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2019-12-16 and 2020-11-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633

Line of Evidence (LOE) for Decision ID 161755, Chlordane	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

99523

Pollutant:

Chlordane

LOE Subgroup:

Pollutant-Tissue

Matrix:

Tissue

Fraction:

Fish fillet

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 SWAMP Sportfish Rivers and Streams data for East Walker River, below Bridgeport Reservoir to determine beneficial use support and the results are as follows 0 of the 1 samples exceeded the water quality standard for Total Chlordanes. Data were collected for 1 fish species (1 composite(s) of Sacramento Blackfish each composed of 5 fish per composite).

Data Reference:

Water Quality Assessment Data for the 2018 solicitation cycle submitted through CEDEN for SWAMP Sportfish Rivers and Streams.

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

National Academy of Science guidelines (NAS 1972) establish a maximum total Chlordane concentration of 100 ug/Kg (wet weight) in tissue samples for protection of aquatic life from bioaccumulation of toxic substances.

Guideline Reference:

National Academy of Sciences. Water Quality Criteria 1972. EPA-R3-73-033. Washington, D.C.: U.S. Environmental Protection Agency

Spatial Representation:

Data was collected from 1 station(s) with the station code(s): 630EWK002.

Temporal Representation:

Data for this line of evidence were collected between 2011-08-29 and 2011-08-29

Environmental Conditions:

QAPP Information:

Quality Assurance Program Plan and Standard Operating Procedures for SWAMP program

QAPP Information Reference(s):

Quality Assurance Program Plans, Quality Assurance Project Plans, and Standard Operating Procedures for the SWAMP program

Line of Evidence (LOE) for Decision ID 161755, Chlordane	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337772

Pollutant:

Chlordane

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed Nevada Division of Environmental Protection data for East Walker River, below Bridgeport Reservoir to determine beneficial use support, and the results are as follows: 0 of the 0 samples exceeded the evaluation guideline for Total Chlordane. Although a total of 2 samples were collected, 2 of these samples were not included in the assessment because the laboratory data reporting limit(s) was above the water quality threshold 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:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The chlordane criterion for the protection of human health from the consumption of water and organisms is 0.00057 ug/L (California Toxics Rule, 2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2019-12-16 and 2020-11-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633

Line of Evidence (LOE) for Decision ID 161755, Chlordane	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337771

Pollutant:

Chlordane

LOE Subgroup:

Pollutant-Water

Matrix:

Water

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 Nevada Division of Environmental Protection data for East Walker River, below Bridgeport Reservoir to determine beneficial use support, and the results are as follows: 0 of the 0 samples exceeded the evaluation guideline for Total Chlordane. Although a total of 2 samples were collected, 2 of these samples were not included in the assessment because the laboratory data reporting limit(s) was above the water quality threshold 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:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The chlordane criterion continuous concentration (expressed as a 4-day average) to protect aquatic life in freshwater is 0.0043 ug/L (California Toxics Rule, 2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2019-12-16 and 2020-11-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633

Line of Evidence (LOE) for Decision ID 161755, Chlordane	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

99522

Pollutant:

Chlordane

LOE Subgroup:

Pollutant-Tissue

Matrix:

Tissue

Fraction:

Fish fillet

Beneficial Use:

Commercial or recreational collection of fish, shellfish, or organisms

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed SWAMP Sportfish Rivers and Streams data for East Walker River, below Bridgeport Reservoir to determine beneficial use support and the results are as follows 0 of the 1 samples exceeded the water quality standard for Total Chlordanes. Data were collected for 1 fish species (1 composite(s) of Sacramento Blackfish each composed of 5 fish per composite).

Data Reference:

Water Quality Assessment Data for the 2018 solicitation cycle submitted through CEDEN for SWAMP Sportfish Rivers and Streams.

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

The modified OEHHA Fish Contaminant Goal for total chlordane in fish tissue is 3.9 ppb. This screening level assumes an average body weight of 70 kg and a consumption rate of 32 g/day for a 30 year exposure over a 70-year lifetime. This constituent is a carcinogen therefore the risk level is set to one in a million. A cooking reduction factor of 1 is applied for skin-off fillets. (Klasing, S., and R. Brodberg, 2008)

Guideline Reference:

Development of Fish Contaminant Goals and Advisory Tissue Levels for Common Contaminants in California Sport Fish: Chlordane, DDTs, Dieldrin, Methylmercury, PCBs, Selenium, and Toxaphene

Spatial Representation:

Data was collected from 1 station(s) with the station code(s): 630EWK002.

Temporal Representation:

Data for this line of evidence were collected between 2011-08-29 and 2011-08-29

Environmental Conditions:

QAPP Information:

Quality Assurance Program Plan and Standard Operating Procedures for SWAMP program

QAPP Information Reference(s):

Quality Assurance Program Plans, Quality Assurance Project Plans, and Standard Operating Procedures for the SWAMP program


DECISION ID	163604	Region 6
East Walker River, below Bridgeport Reservoir

Pollutant:	Chloride
Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)(2018)
Revision Status	Revised
Impairment from Pollutant or Pollution:	Pollutant

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

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

State Board Review of Regional Board Conclusion and Recommendation:

State Board Decision Recommendation:	After review of 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 163604, Chloride	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

342784

Pollutant:

Chloride

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed SWAMP Perennial Stream Surveys data to determine beneficial use support and results are as follows:
1 of 1 samples exceeded the water quality threshold for Chloride

Data Reference:

Benthic, Field, Habitat, WQ from the Surface Water Ambient Monitoring Program for the 2026 Integrated Report in Region 6

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

The Basin Plan objective for Chloride in this water body is 4 (mg/L), (as a Mean).

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: East Walker River ~1mi below Murphy Pond (630PS0163)

Temporal Representation:

The samples were collected between the dates of 2015-06-15 and 2015-06-15

Environmental Conditions:

QAPP Information:

Generic SWAMP QAPrP

QAPP Information Reference(s):

Benthic, Field, Habitat, Tissue, Toxicity, WQ from the Surface Water Ambient Monitoring Program for the 2026 Integrated Report in Region 6

Line of Evidence (LOE) for Decision ID 163604, Chloride	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

342733

Pollutant:

Chloride

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed SWAMP RWB6 Monitoring data to determine beneficial use support and results are as follows:
0 of 6 samples exceeded the water quality threshold for Chloride

Data Reference:

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

The Basin Plan objective for Chloride in this water body is 4 (mg/L), (as a Mean).

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: East Walker River, at CA/NV state line (630EWK001)

Temporal Representation:

The samples were collected between the dates of 2016-03-17 and 2021-11-23

Environmental Conditions:

QAPP Information:

Generic SWAMP QAPrP

QAPP Information Reference(s):

WQX from the NWQMP for the 2026 Integrated Report in Region 6

Line of Evidence (LOE) for Decision ID 163604, Chloride	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

343550

Pollutant:

Chloride

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The Basin Plan objective for Chloride in this water body is 4 (mg/L), (as a Mean).

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: East Fork Walker River @ Stateline (21NEV1_WQX-NV09-301-EF-001)

Temporal Representation:

The samples were collected between the dates of 2020-12-02 and 2022-06-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633

Line of Evidence (LOE) for Decision ID 163604, Chloride	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

343622

Pollutant:

Chloride

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed Nevada Division of Environmental Protection data to determine beneficial use support and results are as follows:
3 of 3 samples exceeded the water quality threshold for Chloride

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The Basin Plan objective for Chloride in this water body is 4 (mg/L), (as a Mean).

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: East Fork Walker River @ Stateline (21NEV1_WQX-NV09-301-EF-001)

Temporal Representation:

The samples were collected between the dates of 2014-05-12 and 2016-05-04

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633

Line of Evidence (LOE) for Decision ID 163604, Chloride	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

343551

Pollutant:

Chloride

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The Basin Plan objective for Chloride in this water body is 4 (mg/L), (as a Mean).

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: East Fork Walker River @ Stateline (21NEV1_WQX-NV09-301-EF-001)

Temporal Representation:

The samples were collected between the dates of 2020-12-02 and 2022-06-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633

Line of Evidence (LOE) for Decision ID 163604, Chloride	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

32229

Pollutant:

Chloride

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total Dissolved

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Zero of 2 samples exceeded the Secondary MCLs.

Data Reference:

Secondary Maximum Contaminant Levels and Compliance. CCR Title 22 section 64449.

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

California Secondary Maximum Contaminant Levels (SMCLs) apply to ambient waters under the Lahontan Basin Plan's "Chemical Constituents" objective. The SMCL for chloride is 250 mg/L.

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

Data were collected at the following station: 630EWK001-East Walker River, below Bridgeport Reservoir.

Temporal Representation:

Samples were collected on the following dates: 8/14/2007 11/8/2007

Environmental Conditions:

QAPP Information:

2002 QAMP (Quality Assurance Management Plan) for the State of California's Surface Water Ambient Monitoring Program

QAPP Information Reference(s):

Quality Assurance Management Plan for the State of California's Surface Water Ambient Monitoring Program. Sacramento, CA. State Water Resources Control Board. SWAMP. December 2002 (1st version)

Line of Evidence (LOE) for Decision ID 163604, Chloride	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

5040

Pollutant:

Chloride

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

Fixed station physical/chemical (conventional plus toxic pollutants)

Data Used to Assess Water Quality:

The U.S. Geological Survey sampled chloride under the Region 6 SWAMP program, at quarterly intervals between 2002 and 2005. Chloride concentrations in 16 samples ranged from 0.58 to 5.35 mg/L. The MCL was not violated.

Data Reference:

2007. SWAMP Data for the West Walker River and East Walker River Hydrologic Units

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

California Maximum Contaminant Levels (MCLs) apply to ambient waters under the Lahontan Basin Plan's "Chemical Constituents" objective. The MCL for chloride is 250 mg/L.

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

One station, East Walker River at the California-Nevada State Line, was sampled.

Temporal Representation:

Sixteen quarterly samples (2 to 4 samples per year) were collected between 2001 and 2005.

Environmental Conditions:

QAPP Information:

Data meet the quality assurance requirements of the SWAMP QAPP.

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 163604, Chloride	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

96894

Pollutant:

Chloride

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data were collected as part of regional routine SWAMP monitoring. Data were collected from one site between 2010 and 2015. Concentrations in the raw data ranged from 0.83 to 5.35 mg/L. Six annual averages were computed, one of which exceeded the water quality objective in 2015.

Data Reference:

Water Quality Assessment Data for the 2018 solicitation cycle submitted through CEDEN for the SWAMP RWB6 Monitoring (tissue and water).

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

The site specific objective for chloride in the East Walker River, as referenced in the Lahontan Basin Plan table 3-15, is an annual average concentration not to exceed 4.0 mg/L. While this objective is written to apply to waters above Bridgeport Reservoir it has been used to assess the waters below the reservoir in recognition of the East Walker River as an interstate water which provides critical water resources to western Nevada.

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

Data were collected from one location, 630EWK001, which is located just upstream of the CA/NV state boundary.

Temporal Representation:

Data were collected between October 2010 and October 2015 predominantly once per quarter.

Environmental Conditions:

QAPP Information:

Data were collected in accordance with the SWAMP QAPP.

QAPP Information Reference(s):

Quality Assurance Program Plans, Quality Assurance Project Plans, and Standard Operating Procedures for the SWAMP program


DECISION ID	161823	Region 6
East Walker River, below Bridgeport Reservoir

Pollutant:	Chromium
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 161823, Chromium	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337541

Pollutant:

Chromium

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The California Maximum Contaminant Level for total chromium incorporated by reference in the Water Quality Control Plan, Lahontan Region is 0.05 mg/L.

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2018-04-04 and 2022-06-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633

Line of Evidence (LOE) for Decision ID 161823, Chromium	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337540

Pollutant:

Chromium

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The California Maximum Contaminant Level for total chromium incorporated by reference in the Water Quality Control Plan, Lahontan Region is 0.05 mg/L.

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2018-04-04 and 2022-06-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633

Line of Evidence (LOE) for Decision ID 161823, Chromium	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337536

Pollutant:

Chromium

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The dissolved chromium (III) criterion continuous concentration (expressed as a 4-day average) to protect aquatic life in freshwater is is hardness dependent as described in Table 1 of paragraph (b)(1). The value calculated when using a default hardness of 100 mg/L is 180 ug/L (California Toxics Rule, 2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2018-04-04 and 2022-06-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633


DECISION ID	161756	Region 6
East Walker River, below Bridgeport Reservoir

Pollutant:	Chrysene (C1-C4)
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 161756, Chrysene (C1-C4)	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337545

Pollutant:

Chrysene (C1-C4)

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Commercial or recreational collection of fish, shellfish, or organisms

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The Chrysene criteria for the protection of human health from consumption of organisms only is 0.049 ug/L (California Toxics Rule, 2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2019-12-16 and 2020-11-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633

Line of Evidence (LOE) for Decision ID 161756, Chrysene (C1-C4)	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337546

Pollutant:

Chrysene (C1-C4)

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed Nevada Division of Environmental Protection data for East Walker River, below Bridgeport Reservoir to determine beneficial use support, and the results are as follows: 0 of the 0 samples exceeded the evaluation guideline for Chrysene. Although a total of 2 samples were collected, 2 of these samples were not included in the assessment because the laboratory data reporting limit(s) was above the water quality threshold 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:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The Chrysene criteria for the protection of human health from the consumption of water and organisms is 0.0044 ug/L (California Toxics Rule, 2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2019-12-16 and 2020-11-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633


DECISION ID	161757	Region 6
East Walker River, below Bridgeport Reservoir

Pollutant:	Cobalt
Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)(2018)
Revision Status	Revised
Impairment from Pollutant or Pollution:	Pollutant

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

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

State Board Review of Regional Board Conclusion and Recommendation:

State Board Decision Recommendation:	After review of 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 161757, Cobalt	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

7698

Pollutant:

Cobalt

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

Fixed station physical/chemical (conventional plus toxic pollutants)

Data Used to Assess Water Quality:

The U.S. Geological Survey sampled the East Walker River under the Region 6 SWAMP program in 2001 and 2002. Concentrations of dissolved cobalt in four samples ranged from 0.07 to 0.168 ug/L.

Data Reference:

2007. SWAMP Data for the West Walker River and East Walker River Hydrologic Units

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

There are no state or federal standards or criteria for cobalt for the protection of freshwater aquatic life.

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

One station, East Walker River at the California-Nevada State Line, was sampled.

Temporal Representation:

Four quarterly samples were collected in 2001 and 2002.

Environmental Conditions:

QAPP Information:

Data meet the quality assurance requirements of the SWAMP QAPP.

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 161757, Cobalt	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337551

Pollutant:

Cobalt

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Agricultural Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Waters designated as AGR shall not contain concentrations of chemical constituents in amounts that adversely affect the water for beneficial uses (Water Quality Control Plan, Lahontan Region).

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Water Quality for Agriculture, published by the Food and Agriculture Organization of the United Nations in 1985, contains criteria protective of various agricultural uses of water. These criteria were used to translate narrative water quality objectives for chemical constituents that prohibit chemicals in concentrations that would impair agricultural uses of water. A 0.05 mg/L criteria is the recommended maximum concentration of cobalt in irrigation water.

Guideline Reference:

Water Quality for Agriculture, Food and Agriculture Organization of the United Nations - Irrigation and Drainage Paper No. 29, Rev 1, Rome (1985)

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2020-12-02 and 2022-06-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633

Line of Evidence (LOE) for Decision ID 161757, Cobalt	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337550

Pollutant:

Cobalt

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Agricultural Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Waters designated as AGR shall not contain concentrations of chemical constituents in amounts that adversely affect the water for beneficial uses (Water Quality Control Plan, Lahontan Region).

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Water Quality for Agriculture, Food and Agriculture Organization of the United Nations - Irrigation and Drainage Paper No. 29, Rev 1, Rome (1985)

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2020-12-02 and 2022-06-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633

Line of Evidence (LOE) for Decision ID 161757, Cobalt	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

7700

Pollutant:

Cobalt

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

Fixed station physical/chemical (conventional plus toxic pollutants)

Data Used to Assess Water Quality:

The U.S. Geological Survey sampled the East Walker River under the Region 6 SWAMP program in 2001 and 2002. Four samples had concentrations of total recoverable cobalt below the detection level.

Data Reference:

2007. SWAMP Data for the West Walker River and East Walker River Hydrologic Units

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

There are no state or federal standards or criteria for cobalt for the protection of human health.

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

One station, East Walker River at the California-Nevada State Line, was sampled.

Temporal Representation:

Four quarterly samples were collected in 2001 and 2002.

Environmental Conditions:

QAPP Information:

Data meet the quality assurance requirements of the SWAMP QAPP.

QAPP Information Reference(s):


DECISION ID	161758	Region 6
East Walker River, below Bridgeport Reservoir

Pollutant:	Copper
Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)(2018)
Revision Status	Revised
Impairment from Pollutant or Pollution:	Pollutant

Regional Board Conclusion:	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. Eleven lines of evidence are available in the administrative record to assess this pollutant. Zero of 20 samples exceed the MUN water quality objective (MCL) and zero of 12 samples exceed the CTR criteria 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 20 samples exceed the MUN water quality objective (MCL) and zero of 12 samples exceed the CTV criteria 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. 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:

Line of Evidence (LOE) for Decision ID 161758, Copper	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

5069

Pollutant:

Copper

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

Fixed station physical/chemical (conventional plus toxic pollutants)

Data Used to Assess Water Quality:

The U.S. Geological Survey sampled copper under the Region 6 SWAMP program in 2001 and 2002. Dissolved copper concentrations in 4 samples ranged from 0.7 to 1.6 ug/L. The CTR standards were not violated.

Data Reference:

2007. SWAMP Data for the West Walker River and East Walker River Hydrologic Units

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

The California Toxics Rule (CTR) freshwater aquatic life standards for copper are hardness-dependent, At the hardness levels reported for this station, the acute (1 hour average) standard ranges from 8.00 to 9.31 ug/L The chronic (4 day average) standard ranges from 5.60 to 6.42 ug/L.

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

One station, East Walker River at the California-Nevada State Line, was sampled.

Temporal Representation:

Four quarterly samples were collected in 2001 and 2002.

Environmental Conditions:

QAPP Information:

Data meet the quality assurance requirements of the SWAMP QAPP.

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 161758, Copper	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337560

Pollutant:

Copper

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The dissolved copper criterion continuous concentration (expressed as a 4-day average) to protect aquatic life in freshwater is hardness dependent. The criterion when calculated using a default hardness of 100 mg/L is 9 ug/L (California Toxics Rule, 2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2018-04-04 and 2022-06-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633

Line of Evidence (LOE) for Decision ID 161758, Copper	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

341278

Pollutant:

Copper

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:

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The California Secondary Maximum Contaminant Level for total Copper incorporated by reference in the Water Quality Control Plan, Lahontan Region is 1.0 mg/L.

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2014-05-12 and 2014-07-24

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633

Line of Evidence (LOE) for Decision ID 161758, Copper	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337559

Pollutant:

Copper

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:

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The California Secondary Maximum Contaminant Level for total Copper incorporated by reference in the Water Quality Control Plan, Lahontan Region is 1.0 mg/L.

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2018-04-04 and 2022-06-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633

Line of Evidence (LOE) for Decision ID 161758, Copper	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

341284

Pollutant:

Copper

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2014-05-12 and 2014-07-24

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633

Line of Evidence (LOE) for Decision ID 161758, Copper	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337561

Pollutant:

Copper

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The California Secondary Maximum Contaminant Level for total Copper incorporated by reference in the Water Quality Control Plan, Lahontan Region is 1.0 mg/L.

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2018-04-04 and 2022-06-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633

Line of Evidence (LOE) for Decision ID 161758, Copper	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

341271

Pollutant:

Copper

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The California Secondary Maximum Contaminant Level for total Copper incorporated by reference in the Water Quality Control Plan, Lahontan Region is 1.0 mg/L.

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2014-05-12 and 2014-07-24

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633

Line of Evidence (LOE) for Decision ID 161758, Copper	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

130092

Pollutant:

Copper

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed STORET data for East Walker River, below Bridgeport Reservoir to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality standard for Copper.

Data Reference:

Water quality data for federal, state, and tribal agencies submitted through the US EPA STorage and RETrival (STORET) database for the 2018 listing cycle.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The California Secondary Maximum Contaminant Level for total Copper incorporated by reference in the Water Quality Control Plan, Lahontan Region is 1.0 mg/L.

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site(s) (21NEV1_WQX-NV09-301-EF-001)

Temporal Representation:

The samples were collected between the dates of 2012-08-07 and 2012-08-07

Environmental Conditions:

QAPP Information:

QAPP not required for federal data

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 161758, Copper	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

5076

Pollutant:

Copper

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

Fixed station physical/chemical (conventional plus toxic pollutants)

Data Used to Assess Water Quality:

The U.S. Geological Survey sampled copper under the Region 6 SWAMP program in 2001 and 2002. Total recoverable copper concentrations in 4 samples ranged from 1.0. to 1.4 ug/L. The MCLs were not exceeded.

Data Reference:

2007. SWAMP Data for the West Walker River and East Walker River Hydrologic Units

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

California Maximum Contaminant Levels (MCLs) are applicable under the Lahontan Basin Plan's Chemical Constituents objective. The primary MCL for copper is 1300 ug/L and the secondary MCL is 1000 ug/L.

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

One station, East Walker River at the California-Nevada State Line, was sampled.

Temporal Representation:

Four quarterly samples were collected in 2001 and 2002.

Environmental Conditions:

QAPP Information:

Data meet the quality assurance requirements of the SWAMP QAPP.

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 161758, Copper	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

99074

Pollutant:

Copper

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

Water quality data for federal, state, and tribal agencies submitted through the US EPA STorage and RETrival (STORET) database for the 2018 listing cycle.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

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

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site(s) (21NEV1_WQX-NV09-301-EF-001)

Temporal Representation:

The samples were collected between the dates of 2012-08-07 and 2012-08-07

Environmental Conditions:

QAPP Information:

QAPP not required for federal data

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 161758, Copper	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

130044

Pollutant:

Copper

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

Water quality data for federal, state, and tribal agencies submitted through the US EPA STorage and RETrival (STORET) database for the 2018 listing cycle.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The California Secondary Maximum Contaminant Level for total Copper incorporated by reference in the Water Quality Control Plan, Lahontan Region is 1.0 mg/L.

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site(s) (21NEV1_WQX-NV09-301-EF-001)

Temporal Representation:

The samples were collected between the dates of 2012-08-07 and 2012-08-07

Environmental Conditions:

QAPP Information:

QAPP not required for federal data

QAPP Information Reference(s):

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


DECISION ID	161759	Region 6
East Walker River, below Bridgeport Reservoir

Pollutant:	Cumene
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:

Line of Evidence (LOE) for Decision ID 161759, Cumene	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337630

Pollutant:

Cumene

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:

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

The USEPA expected safe lifetime exposure limit in drinking water for Isopropylbenzene, calculated using the IRIS Reference Dose, is 0.7 mg/L. This was calculated assuming 70 kg body weight, 2 liters/day water consumption, 20% relative source contribution from drinking water, and 0.1 mg/kg/day as the reference dose.

Guideline Reference:

2012 Edition of the Drinking Water Standards and Health Advisories

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2020-11-30 and 2020-11-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633


DECISION ID	103816	Region 6
East Walker River, below Bridgeport Reservoir

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

Regional Board Conclusion:	This pollutant is being considered for placement on the CWA section 303(d) List under section 3.1 of the Listing Policy. Under section 3.1 a single line of evidence is necessary to assess listing status. Two lines of evidence are available in the administrative record to assess this pollutant that assess the same single tissue sample for COMM and COLD. Zero of one samples exceed the COLD guideline and zero of one samples exceed the COMM guideline for Total DDT. 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 samples exceed the COLD guideline and zero of one samples exceed the COMM guideline 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. The readily available data and information is insufficient to determine, with the power and confidence of the Listing Policy, the applicable beneficial use support rating.

State Board Review of Regional Board Conclusion and Recommendation:

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

Line of Evidence (LOE) for Decision ID 103816, DDT (Dichlorodiphenyltrichloroethane)	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

99339

Pollutant:

Total DDT (sum of 4,4'- and 2,4'- isomers of DDT, DDE, and DDD)

LOE Subgroup:

Pollutant-Tissue

Matrix:

Tissue

Fraction:

Fish fillet

Beneficial Use:

Commercial or recreational collection of fish, shellfish, or organisms

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed SWAMP Sportfish Rivers and Streams data for East Walker River, below Bridgeport Reservoir to determine beneficial use support and the results are as follows 0 of the 1 samples exceeded the water quality standard for Total DDT (sum of 4,4'- and 2,4'- isomers of DDT, DDE, and DDD). Data were collected for 1 fish species (1 composite(s) of Sacramento Blackfish each composed of 5 fish per composite).

Data Reference:

Water Quality Assessment Data for the 2018 solicitation cycle submitted through CEDEN for SWAMP Sportfish Rivers and Streams.

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

The modified OEHHA Fish Contaminant Goal for total DDT in fish tissue is 15 ppb. This screening level assumes an average body weight of 70 kg and a consumption rate of 32 g/day for a 30 year exposure over a 70-year lifetime. This constituent is a carcinogen therefore the risk level is set to one in a million. A cooking reduction factor of 1 is applied for skin-off fillets. (Klasing, S., and R. Brodberg, 2008)

Guideline Reference:

Development of Fish Contaminant Goals and Advisory Tissue Levels for Common Contaminants in California Sport Fish: Chlordane, DDTs, Dieldrin, Methylmercury, PCBs, Selenium, and Toxaphene

Spatial Representation:

Data was collected from 1 station(s) with the station code(s): 630EWK002.

Temporal Representation:

Data for this line of evidence were collected between 2011-08-29 and 2011-08-29

Environmental Conditions:

QAPP Information:

Quality Assurance Program Plan and Standard Operating Procedures for SWAMP program

QAPP Information Reference(s):

Quality Assurance Program Plans, Quality Assurance Project Plans, and Standard Operating Procedures for the SWAMP program

Line of Evidence (LOE) for Decision ID 103816, DDT (Dichlorodiphenyltrichloroethane)	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

99338

Pollutant:

Total DDT (sum of 4,4'- and 2,4'- isomers of DDT, DDE, and DDD)

LOE Subgroup:

Pollutant-Tissue

Matrix:

Tissue

Fraction:

Fish fillet

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 SWAMP Sportfish Rivers and Streams data for East Walker River, below Bridgeport Reservoir to determine beneficial use support and the results are as follows 0 of the 1 samples exceeded the water quality standard for Total DDT (sum of 4,4'- and 2,4'- isomers of DDT, DDE, and DDD). Data were collected for 1 fish species (1 composite(s) of Sacramento Blackfish each composed of 5 fish per composite).

Data Reference:

Water Quality Assessment Data for the 2018 solicitation cycle submitted through CEDEN for SWAMP Sportfish Rivers and Streams.

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

National Academy of Science guidelines (NAS 1972) establish a maximum total DDT concentration of 1000 ug/Kg (wet weight) in tissue samples for protection of aquatic life from bioaccumulation of toxic substances.

Guideline Reference:

National Academy of Sciences. Water Quality Criteria 1972. EPA-R3-73-033. Washington, D.C.: U.S. Environmental Protection Agency

Spatial Representation:

Data was collected from 1 station(s) with the station code(s): 630EWK002.

Temporal Representation:

Data for this line of evidence were collected between 2011-08-29 and 2011-08-29

Environmental Conditions:

QAPP Information:

Quality Assurance Program Plan and Standard Operating Procedures for SWAMP program

QAPP Information Reference(s):

Quality Assurance Program Plans, Quality Assurance Project Plans, and Standard Operating Procedures for the SWAMP program


DECISION ID	161760	Region 6
East Walker River, below Bridgeport Reservoir

Pollutant:	Dacthal
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:

Line of Evidence (LOE) for Decision ID 161760, Dacthal	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337563

Pollutant:

Dacthal

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Not Recorded

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

The USEPA Lifetime Health advisory level for Dacthal is 0.07 mg/L.

Guideline Reference:

2012 Edition of the Drinking Water Standards and Health Advisories

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2019-12-16 and 2019-12-16

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633

Line of Evidence (LOE) for Decision ID 161760, Dacthal	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337562

Pollutant:

Dacthal

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Not Recorded

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:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

The evaluation guideline for Dacthal is the USEPA Aquatic Life Benchmark of >11000 ug/L for a nonvascular plant (acute) and vascular plant (acute). The benchmark was derived from a greater-than value (for example, > 265,000) and may overestimate toxicity.

Guideline Reference:

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2019-12-16 and 2019-12-16

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):


DECISION ID	161761	Region 6
East Walker River, below Bridgeport Reservoir

Pollutant:	Diazinon
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 161761, Diazinon	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337564

Pollutant:

Diazinon

LOE Subgroup:

Pollutant-Water

Matrix:

Water

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:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

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

Guideline Reference:

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

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2019-12-16 and 2020-11-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633

Line of Evidence (LOE) for Decision ID 161761, Diazinon	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337565

Pollutant:

Diazinon

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:

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

The USEPA drinking water health advisory for diazinon rounded to one significant figure is 1 ug/L.

Guideline Reference:

2018 Edition of the Drinking Water Standards and Health Advisories

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2019-12-16 and 2020-11-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633


DECISION ID	161809	Region 6
East Walker River, below Bridgeport Reservoir

Pollutant:	Dicamba
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 161809, Dicamba	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337566

Pollutant:

Dicamba

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:

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

The USEPA Health Advisory for lifetime exposure to Dicamba as a drinking water level is a concentration of 4 mg/L.

Guideline Reference:

2012 Edition of the Drinking Water Standards and Health Advisories

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2019-12-16 and 2020-11-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633

Line of Evidence (LOE) for Decision ID 161809, Dicamba	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337567

Pollutant:

Dicamba

LOE Subgroup:

Pollutant-Water

Matrix:

Water

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:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

The evaluation guideline for Dicamba is the USEPA Aquatic Life Benchmark of 61 ug/L for a nonvascular plant (acute) for Dicamba acid.

Guideline Reference:

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2019-12-16 and 2020-11-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):


DECISION ID	161762	Region 6
East Walker River, below Bridgeport Reservoir

Pollutant:	Dichlorodifluoromethane
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:

Line of Evidence (LOE) for Decision ID 161762, Dichlorodifluoromethane	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337568

Pollutant:

Dichlorodifluoromethane

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:

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

USEPA's Drinking Water Health advisory for life-time exposure is a concentration for dichlorofluoromethane of 1 mg/L

Guideline Reference:

2012 Edition of the Drinking Water Standards and Health Advisories

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2020-11-30 and 2020-11-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633


DECISION ID	161763	Region 6
East Walker River, below Bridgeport Reservoir

Pollutant:	Dieldrin
Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)(2018)
Revision Status	Revised
Impairment from Pollutant or Pollution:	Pollutant

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

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

State Board Review of Regional Board Conclusion and Recommendation:

State Board Decision Recommendation:	After review of 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 161763, Dieldrin	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

99101

Pollutant:

Dieldrin

LOE Subgroup:

Pollutant-Tissue

Matrix:

Tissue

Fraction:

Fish fillet

Beneficial Use:

Commercial or recreational collection of fish, shellfish, or organisms

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed SWAMP Sportfish Rivers and Streams data for East Walker River, below Bridgeport Reservoir to determine beneficial use support and the results are as follows 1 of the 1 samples exceeded the water quality standard for Dieldrin. Data were collected for 1 fish species (1 composite(s) of Sacramento Blackfish each composed of 5 fish per composite). Of these, 1 species (Sacramento Blackfish) exceeded the water quality standard.

Data Reference:

Water Quality Assessment Data for the 2018 solicitation cycle submitted through CEDEN for SWAMP Sportfish Rivers and Streams.

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

The modified OEHHA Fish Contaminant Goal for dieldrin in fish tissue is 0.32 ppb. This screening level assumes an average body weight of 70 kg and a consumption rate of 32 g/day for a 30 year exposure over a 70-year lifetime. This constituent is a carcinogen therefore the risk level is set to one in a million. A cooking reduction factor of 1 is applied for skin-off fillets. (Klasing, S., and R. Brodberg, 2008)

Guideline Reference:

Development of Fish Contaminant Goals and Advisory Tissue Levels for Common Contaminants in California Sport Fish: Chlordane, DDTs, Dieldrin, Methylmercury, PCBs, Selenium, and Toxaphene

Spatial Representation:

Data was collected from 1 station(s) with the station code(s): 630EWK002.

Temporal Representation:

Data for this line of evidence were collected between 2011-08-29 and 2011-08-29

Environmental Conditions:

QAPP Information:

Quality Assurance Program Plan and Standard Operating Procedures for SWAMP program

QAPP Information Reference(s):

Quality Assurance Program Plans, Quality Assurance Project Plans, and Standard Operating Procedures for the SWAMP program

Line of Evidence (LOE) for Decision ID 161763, Dieldrin	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337574

Pollutant:

Dieldrin

LOE Subgroup:

Pollutant-Water

Matrix:

Water

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:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The dieldrin criterion continuous concentration (expressed as a 4-day average) to protect aquatic life in freshwater is 0.056 ug/L (California Toxics Rule, 2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2019-12-16 and 2020-11-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633

Line of Evidence (LOE) for Decision ID 161763, Dieldrin	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

99099

Pollutant:

Dieldrin

LOE Subgroup:

Pollutant-Tissue

Matrix:

Tissue

Fraction:

Fish fillet

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 SWAMP Sportfish Rivers and Streams data for East Walker River, below Bridgeport Reservoir to determine beneficial use support and the results are as follows 0 of the 1 samples exceeded the water quality standard for Dieldrin. Data were collected for 1 fish species (1 composite(s) of Sacramento Blackfish each composed of 5 fish per composite).

Data Reference:

Water Quality Assessment Data for the 2018 solicitation cycle submitted through CEDEN for SWAMP Sportfish Rivers and Streams.

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

National Academy of Science guidelines (NAS 1972) establish a maximum Dieldrin concentration of 100 ug/Kg (wet weight) in tissue samples for protection of aquatic life from bioaccumulation of toxic substances.

Guideline Reference:

National Academy of Sciences. Water Quality Criteria 1972. EPA-R3-73-033. Washington, D.C.: U.S. Environmental Protection Agency

Spatial Representation:

Data was collected from 1 station(s) with the station code(s): 630EWK002.

Temporal Representation:

Data for this line of evidence were collected between 2011-08-29 and 2011-08-29

Environmental Conditions:

QAPP Information:

Quality Assurance Program Plan and Standard Operating Procedures for SWAMP program

QAPP Information Reference(s):

Quality Assurance Program Plans, Quality Assurance Project Plans, and Standard Operating Procedures for the SWAMP program

Line of Evidence (LOE) for Decision ID 161763, Dieldrin	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337576

Pollutant:

Dieldrin

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed Nevada Division of Environmental Protection data for East Walker River, below Bridgeport Reservoir to determine beneficial use support, and the results are as follows: 0 of the 0 samples exceeded the evaluation guideline for Dieldrin. Although a total of 2 samples were collected, 2 of these samples were not included in the assessment because the laboratory data reporting limit(s) was above the water quality threshold 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:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The Dieldrin criteria for the protection of human health from the consumption of water and organisms is 0.00014 ug/L (California Toxics Rule, 2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2019-12-16 and 2020-11-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633

Line of Evidence (LOE) for Decision ID 161763, Dieldrin	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337575

Pollutant:

Dieldrin

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:

Water Board staff assessed Nevada Division of Environmental Protection data for East Walker River, below Bridgeport Reservoir to determine beneficial use support, and the results are as follows: 0 of the 0 samples exceeded the evaluation guideline for Dieldrin. Although a total of 2 samples were collected, 2 of these samples were not included in the assessment because the laboratory data reporting limit(s) was above the water quality threshold 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:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The Dieldrin criteria for the protection of human health from consumption of organisms only is 0.00014 ug/L (California Toxics Rule, 2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2019-12-16 and 2020-11-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633


DECISION ID	161764	Region 6
East Walker River, below Bridgeport Reservoir

Pollutant:	Diethyl phthalate
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:

Line of Evidence (LOE) for Decision ID 161764, Diethyl phthalate	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337580

Pollutant:

Diethyl phthalate

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Not Recorded

Beneficial Use:

Commercial or recreational collection of fish, shellfish, or organisms

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The Diethylphthalate criteria for the protection of human health from consumption of organisms only is 120,000 ug/L (California Toxics Rule, 2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2020-11-30 and 2020-11-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633

Line of Evidence (LOE) for Decision ID 161764, Diethyl phthalate	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337578

Pollutant:

Diethyl phthalate

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Not Recorded

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The Diethylphthalate criteria for the protection of human health from the consumption of water and organisms is 23,000 ug/L (California Toxics Rule, 2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2020-11-30 and 2020-11-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633

Line of Evidence (LOE) for Decision ID 161764, Diethyl phthalate	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337579

Pollutant:

Diethyl phthalate

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:

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The Diethylphthalate criteria for the protection of human health from the consumption of water and organisms is 23,000 ug/L (California Toxics Rule, 2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2019-12-16 and 2019-12-16

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633

Line of Evidence (LOE) for Decision ID 161764, Diethyl phthalate	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337577

Pollutant:

Diethyl phthalate

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Commercial or recreational collection of fish, shellfish, or organisms

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The Diethylphthalate criteria for the protection of human health from consumption of organisms only is 120,000 ug/L (California Toxics Rule, 2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2019-12-16 and 2019-12-16

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633


DECISION ID	161813	Region 6
East Walker River, below Bridgeport Reservoir

Pollutant:	Dimethoate
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 161813, Dimethoate	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337581

Pollutant:

Dimethoate

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:

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Drinking water notification levels are published by the Division of Drinking Water and are for chemicals for which there is no drinking water MCL. If a notification level is exceeded, local government notification is required and customer notification is recommended. The notification level for dimethoate is 1 ug/L.

Guideline Reference:

CDPH Archived Advisory Levels for Drinking Water. Archived Advisory Levels are currently considered Notification Levels.

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2019-12-16 and 2020-11-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633

Line of Evidence (LOE) for Decision ID 161813, Dimethoate	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337582

Pollutant:

Dimethoate

LOE Subgroup:

Pollutant-Water

Matrix:

Water

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:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

The evaluation guideline for dimethoate is the USEPA Aquatic Life Benchmark of 0.5 ug/L for an invertebrate (chronic).

Guideline Reference:

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2019-12-16 and 2020-11-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):


DECISION ID	161765	Region 6
East Walker River, below Bridgeport Reservoir

Pollutant:	Dimethyl phthalate
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:

Line of Evidence (LOE) for Decision ID 161765, Dimethyl phthalate	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337584

Pollutant:

Dimethyl phthalate

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:

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The Dimethylphthalate criteria for the protection of human health from the consumption of water and organisms is 313,000 ug/L (California Toxics Rule, 2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2019-12-16 and 2019-12-16

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633

Line of Evidence (LOE) for Decision ID 161765, Dimethyl phthalate	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337583

Pollutant:

Dimethyl phthalate

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Commercial or recreational collection of fish, shellfish, or organisms

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The Dimethylphthalate criteria for the protection of human health from consumption of organisms only is 2,900,000 ug/L (California Toxics Rule, 2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2019-12-16 and 2019-12-16

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633


DECISION ID	161766	Region 6
East Walker River, below Bridgeport Reservoir

Pollutant:	Dinoseb
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 161766, Dinoseb	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337587

Pollutant:

Dinoseb

LOE Subgroup:

Pollutant-Water

Matrix:

Water

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:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

The evaluation guideline for Dinoseb is the LC50 of 44 ug/L for Salvelinus namaycush (Lake trout) (USEPA Office of Pesticide Programs Ecotoxicity database).

Guideline Reference:

OPP Pesticide Ecotoxicity Database.

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2019-12-16 and 2020-11-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633

Line of Evidence (LOE) for Decision ID 161766, Dinoseb	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337588

Pollutant:

Dinoseb

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:

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The California Maximum Contaminant Level for Dinoseb incorporated by reference in the Water Quality Control Plan, Lahontan Region is 7 ug/L (Water Quality Control Plan, Lahontan Region).

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2019-12-16 and 2020-11-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633


DECISION ID	161767	Region 6
East Walker River, below Bridgeport Reservoir

Pollutant:	Diquat
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 161767, Diquat	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337590

Pollutant:

Diquat

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:

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The California Maximum Contaminant Level for Diquat incorporated by reference in the Water Quality Control Plan, Lahontan Region is 20 ug/L (Water Quality Control Plan, Lahontan Region).

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2019-12-16 and 2020-11-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633

Line of Evidence (LOE) for Decision ID 161767, Diquat	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337589

Pollutant:

Diquat

LOE Subgroup:

Pollutant-Water

Matrix:

Water

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:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

The evaluation guideline for diquat is the USEPA Aquatic Life Benchmark of 0.75 ug/L for a vascular plant (acute).

Guideline Reference:

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2019-12-16 and 2020-11-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):


DECISION ID	102638	Region 6
East Walker River, below Bridgeport Reservoir

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

Regional Board Conclusion:	This pollutant is being considered for placement on the CWA section 303(d) List under section 3.1 of the Listing Policy. Under section 3.1 a single line of evidence is necessary to assess listing status. Two lines of evidence are available in the administrative record to assess this pollutant both based on the same single tissue sample assessed for COLD and COMM. The single tissue sample does not exceed the guideline for either COLD or COMM. 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 samples exceeded the tissue guideline for COLD or for COMM 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. The readily available data and information is insufficient to determine, with the power and confidence of the Listing Policy, the applicable beneficial use support rating.

State Board Review of Regional Board Conclusion and Recommendation:

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

Line of Evidence (LOE) for Decision ID 102638, Endosulfan	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

99154

Pollutant:

Endosulfan

LOE Subgroup:

Pollutant-Tissue

Matrix:

Tissue

Fraction:

Fish fillet

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 SWAMP Sportfish Rivers and Streams data for East Walker River, below Bridgeport Reservoir to determine beneficial use support and the results are as follows 0 of the 1 samples exceeded the water quality standard for Endosulfan. Data were collected for 1 fish species (1 composite(s) of Sacramento Blackfish each composed of 5 fish per composite).

Data Reference:

Water Quality Assessment Data for the 2018 solicitation cycle submitted through CEDEN for SWAMP Sportfish Rivers and Streams.

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

National Academy of Science guidelines (NAS 1972) establish a maximum Endosulfan, Total concentration of 100 ug/Kg (wet weight) in tissue samples for protection of aquatic life from bioaccumulation of toxic substances.

Guideline Reference:

National Academy of Sciences. Water Quality Criteria 1972. EPA-R3-73-033. Washington, D.C.: U.S. Environmental Protection Agency

Spatial Representation:

Data was collected from 1 station(s) with the station code(s): 630EWK002.

Temporal Representation:

Data for this line of evidence were collected between 2011-08-29 and 2011-08-29

Environmental Conditions:

QAPP Information:

Quality Assurance Program Plan and Standard Operating Procedures for SWAMP program

QAPP Information Reference(s):

Quality Assurance Program Plans, Quality Assurance Project Plans, and Standard Operating Procedures for the SWAMP program

Line of Evidence (LOE) for Decision ID 102638, Endosulfan	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

99153

Pollutant:

Endosulfan

LOE Subgroup:

Pollutant-Tissue

Matrix:

Tissue

Fraction:

Fish fillet

Beneficial Use:

Commercial or recreational collection of fish, shellfish, or organisms

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed SWAMP Sportfish Rivers and Streams data for East Walker River, below Bridgeport Reservoir to determine beneficial use support and the results are as follows 0 of the 1 samples exceeded the water quality standard for Endosulfan. Data were collected for 1 fish species (1 composite(s) of Sacramento Blackfish each composed of 5 fish per composite).

Data Reference:

Water Quality Assessment Data for the 2018 solicitation cycle submitted through CEDEN for SWAMP Sportfish Rivers and Streams.

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

The modified OEHHA Fish Contaminant Goal for endosulfan (l and ll) in fish tissue is 13,000 ppb. This screening level assumes an average body weight of 70 kg and a consumption rate of 32 g/day. A cooking reduction factor of 1 is applied for skin-off fillets. (Klasing, S., and R. Brodberg, 2008; USEPA, 2000)

Guideline Reference:

Development of Fish Contaminant Goals and Advisory Tissue Levels for Common Contaminants in California Sport Fish: Chlordane, DDTs, Dieldrin, Methylmercury, PCBs, Selenium, and Toxaphene

Guideline Reference:

Guidance for Assessing Chemical Contaminant Data for Use In Fish Advisories Volume 1: Fish Sampling and Analysis

Spatial Representation:

Data was collected from 1 station(s) with the station code(s): 630EWK002.

Temporal Representation:

Data for this line of evidence were collected between 2011-08-29 and 2011-08-29

Environmental Conditions:

QAPP Information:

Quality Assurance Program Plan and Standard Operating Procedures for SWAMP program

QAPP Information Reference(s):

Quality Assurance Program Plans, Quality Assurance Project Plans, and Standard Operating Procedures for the SWAMP program


DECISION ID	161768	Region 6
East Walker River, below Bridgeport Reservoir

Pollutant:	Endothall
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 161768, Endothall	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337591

Pollutant:

Endothall

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:

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The California Maximum Contaminant Level for Endothall incorporated by reference in the Water Quality Control Plan, Lahontan Region is 100 ug/L (Water Quality Control Plan, Lahontan Region).

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2019-12-16 and 2020-11-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633


DECISION ID	161769	Region 6
East Walker River, below Bridgeport Reservoir

Pollutant:	Endrin
Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)(2018)
Revision Status	Revised
Impairment from Pollutant or Pollution:	Pollutant

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

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

State Board Review of Regional Board Conclusion and Recommendation:

State Board Decision Recommendation:	After review of 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 161769, Endrin	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337593

Pollutant:

Endrin

LOE Subgroup:

Pollutant-Water

Matrix:

Water

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:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The endrin criterion continuous concentration (expressed as a 4-day average) to protect aquatic life in freshwater is 0.036 ug/L (California Toxics Rule, 2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2019-12-16 and 2020-11-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633

Line of Evidence (LOE) for Decision ID 161769, Endrin	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337594

Pollutant:

Endrin

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Commercial or recreational collection of fish, shellfish, or organisms

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The Endrin criteria for the protection of human health from consumption of organisms only is 0.81ug/L (California Toxics Rule, 2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2019-12-16 and 2020-11-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633

Line of Evidence (LOE) for Decision ID 161769, Endrin	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

99125

Pollutant:

Endrin

LOE Subgroup:

Pollutant-Tissue

Matrix:

Tissue

Fraction:

Fish fillet

Beneficial Use:

Commercial or recreational collection of fish, shellfish, or organisms

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed SWAMP Sportfish Rivers and Streams data for East Walker River, below Bridgeport Reservoir to determine beneficial use support and the results are as follows 0 of the 1 samples exceeded the water quality standard for Endrin. Data were collected for 1 fish species (1 composite(s) of Sacramento Blackfish each composed of 5 fish per composite).

Data Reference:

Water Quality Assessment Data for the 2018 solicitation cycle submitted through CEDEN for SWAMP Sportfish Rivers and Streams.

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

The modified OEHHA Fish Contaminant Goal for endrin in fish tissue is 660 ppb. This screening level assumes an average body weight of 70 kg and a consumption rate of 32 g/day. A cooking reduction factor of 1 is applied for skin-off fillets. (Klasing, S., and R. Brodberg, 2008; USEPA, 2000)

Guideline Reference:

Development of Fish Contaminant Goals and Advisory Tissue Levels for Common Contaminants in California Sport Fish: Chlordane, DDTs, Dieldrin, Methylmercury, PCBs, Selenium, and Toxaphene

Guideline Reference:

Guidance for Assessing Chemical Contaminant Data for Use In Fish Advisories Volume 1: Fish Sampling and Analysis

Spatial Representation:

Data was collected from 1 station(s) with the station code(s): 630EWK002.

Temporal Representation:

Data for this line of evidence were collected between 2011-08-29 and 2011-08-29

Environmental Conditions:

QAPP Information:

Quality Assurance Program Plan and Standard Operating Procedures for SWAMP program

QAPP Information Reference(s):

Quality Assurance Program Plans, Quality Assurance Project Plans, and Standard Operating Procedures for the SWAMP program

Line of Evidence (LOE) for Decision ID 161769, Endrin	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

99123

Pollutant:

Endrin

LOE Subgroup:

Pollutant-Tissue

Matrix:

Tissue

Fraction:

Fish fillet

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 SWAMP Sportfish Rivers and Streams data for East Walker River, below Bridgeport Reservoir to determine beneficial use support and the results are as follows 0 of the 1 samples exceeded the water quality standard for Endrin. Data were collected for 1 fish species (1 composite(s) of Sacramento Blackfish each composed of 5 fish per composite).

Data Reference:

Water Quality Assessment Data for the 2018 solicitation cycle submitted through CEDEN for SWAMP Sportfish Rivers and Streams.

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

National Academy of Science guidelines (NAS 1972) establish a maximum Endrin concentration of 100 ug/Kg (wet weight) in tissue samples for protection of aquatic life from bioaccumulation of toxic substances.

Guideline Reference:

National Academy of Sciences. Water Quality Criteria 1972. EPA-R3-73-033. Washington, D.C.: U.S. Environmental Protection Agency

Spatial Representation:

Data was collected from 1 station(s) with the station code(s): 630EWK002.

Temporal Representation:

Data for this line of evidence were collected between 2011-08-29 and 2011-08-29

Environmental Conditions:

QAPP Information:

Quality Assurance Program Plan and Standard Operating Procedures for SWAMP program

QAPP Information Reference(s):

Quality Assurance Program Plans, Quality Assurance Project Plans, and Standard Operating Procedures for the SWAMP program

Line of Evidence (LOE) for Decision ID 161769, Endrin	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337592

Pollutant:

Endrin

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:

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The Endrin criteria for the protection of human health from the consumption of water and organisms is 0.76 ug/L (California Toxics Rule, 2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2019-12-16 and 2020-11-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633


DECISION ID	161770	Region 6
East Walker River, below Bridgeport Reservoir

Pollutant:	Fluorene
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 161770, Fluorene	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337595

Pollutant:

Fluorene

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:

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The fluorene criterion for the protection of human health from the consumption of water and organisms is 1,300 ug/L (California Toxics Rule, 2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2019-12-16 and 2020-11-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633

Line of Evidence (LOE) for Decision ID 161770, Fluorene	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337596

Pollutant:

Fluorene

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Commercial or recreational collection of fish, shellfish, or organisms

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The fluorene criterion for the protection of human health from consumption of organisms only is 14,000 ug/L (California Toxics Rule, 2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2019-12-16 and 2020-11-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633


DECISION ID	161771	Region 6
East Walker River, below Bridgeport Reservoir

Pollutant:	Fluoride
Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)(2018)
Revision Status	Revised
Impairment from Pollutant or Pollution:	Pollutant

Regional Board Conclusion:	This pollutant is being considered for placement on the CWA section 303(d) List under section 3.2 of the Listing Policy. Under section 3.2 a single line of evidence is necessary to assess listing status. 11 lines of evidence are available in the administrative record to assess this pollutant. Zero of the 60 samples exceed the MUN water quality objective, and zero of 35 samples exceed the AGR evaluation guideline for fluoride. Based on the readily available data and information, the weight of evidence indicates that there is sufficient justification against placing this water segment-pollutant combination on the CWA section 303(d) List. This conclusion is based on the staff findings that: 1. The data used satisfies the data quality requirements of section 6.1.4 of the Policy. 2. The data used satisfies the data quantity requirements of section 6.1.5 of the Policy. 3. Zero of the 60 samples exceed the MUN water quality objective, and zero of 35 samples exceed the AGR evaluation guideline for fluoride and this does not exceed the allowable frequency listed in Table 3.2 of the Listing Policy. 4. Pursuant to section 3.11 of the Listing Policy, no additional data and information are available indicating that standards are not met.

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

State Board Review of Regional Board Conclusion and Recommendation:

State Board Decision Recommendation:

Line of Evidence (LOE) for Decision ID 161771, Fluoride	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

99002

Pollutant:

Fluoride

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:

Data Reference:

Water quality data for federal, state, and tribal agencies submitted through the US EPA STorage and RETrival (STORET) database for the 2018 listing cycle.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The California Maximum Contaminant Level for Fluoride incorporated by reference in the Water Quality Control Plan, Lahontan Region is 2 mg/L (Water Quality Control Plan, Lahontan Region).

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site(s) (21NEV1_WQX-NV09-301-EF-001)

Temporal Representation:

The samples were collected between the dates of 2011-03-09 and 2012-08-07

Environmental Conditions:

QAPP Information:

QAPP not required for federal data

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 161771, Fluoride	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

338634

Pollutant:

Fluoride

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed SWAMP RWB6 Monitoring data for East Walker River, below Bridgeport Reservoir to determine beneficial use support and results are as follows: 0 of 14 samples exceeded the water quality threshold for Fluoride.

Data Reference:

Benthic, Field, Habitat, Tissue, Toxicity, WQ from the Surface Water Ambient Monitoring Program for the 2026 Integrated Report in Region 6

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

The California Maximum Contaminant Level for Fluoride incorporated by reference in the Water Quality Control Plan, Lahontan Region is 2 mg/L (Water Quality Control Plan, Lahontan Region).

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 630EWK001 (East Walker River, at CA/NV state line).

Temporal Representation:

The samples were collected between the dates of 2016-03-17 and 2020-03-11

Environmental Conditions:

QAPP Information:

Generic SWAMP QAPrP

QAPP Information Reference(s):

WQX from the NWQMP for the 2026 Integrated Report in Region 6

Line of Evidence (LOE) for Decision ID 161771, Fluoride	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337600

Pollutant:

Fluoride

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Agricultural Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Waters designated as AGR shall not contain concentrations of chemical constituents in amounts that adversely affect the water for beneficial uses (i.e., agricultural purposes). (Water Quality Control Plan, Lahontan Region)

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Water Quality for Agriculture, published by the Food and Agriculture Organization of the United Nations in 1985, contains criteria protective of various agricultural uses of water. These criteria were used to translate narrative water quality objectives for chemical constituents that prohibit chemicals in concentrations that would impair agricultural uses of water. A 1 mg/L criteria is the recommended maximum concentration of Fluoride in irrigation water.

Guideline Reference:

Water Quality for Agriculture, Food and Agriculture Organization of the United Nations - Irrigation and Drainage Paper No. 29, Rev 1, Rome (1985)

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2018-01-10 and 2022-06-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633

Line of Evidence (LOE) for Decision ID 161771, Fluoride	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

341323

Pollutant:

Fluoride

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Agricultural Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Water Quality for Agriculture, published by the Food and Agriculture Organization of the United Nations in 1985, contains criteria protective of various agricultural uses of water. These criteria were used to translate narrative water quality objectives for chemical constituents that prohibit chemicals in concentrations that would impair agricultural uses of water. A 1 mg/L criteria is the recommended maximum concentration of Fluoride in irrigation water.

Guideline Reference:

Water Quality for Agriculture, Food and Agriculture Organization of the United Nations - Irrigation and Drainage Paper No. 29, Rev 1, Rome (1985)

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2014-05-12 and 2017-03-14

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633

Line of Evidence (LOE) for Decision ID 161771, Fluoride	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

341320

Pollutant:

Fluoride

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:

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The California Maximum Contaminant Level for Fluoride incorporated by reference in the Water Quality Control Plan, Lahontan Region is 2 mg/L (Water Quality Control Plan, Lahontan Region).

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2014-05-12 and 2017-03-14

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633

Line of Evidence (LOE) for Decision ID 161771, Fluoride	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

338592

Pollutant:

Fluoride

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Agricultural Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed SWAMP RWB6 Monitoring data for East Walker River, below Bridgeport Reservoir to determine beneficial use support and results are as follows: 0 of 4 samples exceeded the water quality threshold for Fluoride.

Data Reference:

Benthic, Field, Habitat, Tissue, Toxicity, WQ from the Surface Water Ambient Monitoring Program for the 2026 Integrated Report in Region 6

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Water Quality for Agriculture, published by the Food and Agriculture Organization of the United Nations in 1985, contains criteria protective of various agricultural uses of water. These criteria were used to translate narrative water quality objectives for chemical constituents that prohibit chemicals in concentrations that would impair agricultural uses of water. A 1 mg/L criteria is the recommended maximum concentration of Fluoride in irrigation water.

Guideline Reference:

Water Quality for Agriculture, Food and Agriculture Organization of the United Nations - Irrigation and Drainage Paper No. 29, Rev 1, Rome (1985)

Spatial Representation:

The samples were collected at 1 monitoring site: 630EWK001 (East Walker River, at CA/NV state line).

Temporal Representation:

The samples were collected between the dates of 2017-11-01 and 2021-11-23

Environmental Conditions:

QAPP Information:

Generic SWAMP QAPrP

QAPP Information Reference(s):

Benthic, Field, Habitat, Tissue, Toxicity, WQ from the Surface Water Ambient Monitoring Program for the 2026 Integrated Report in Region 6

Line of Evidence (LOE) for Decision ID 161771, Fluoride	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

338606

Pollutant:

Fluoride

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Agricultural Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Water Quality for Agriculture, published by the Food and Agriculture Organization of the United Nations in 1985, contains criteria protective of various agricultural uses of water. These criteria were used to translate narrative water quality objectives for chemical constituents that prohibit chemicals in concentrations that would impair agricultural uses of water. A 1 mg/L criteria is the recommended maximum concentration of Fluoride in irrigation water.

Guideline Reference:

Water Quality for Agriculture, Food and Agriculture Organization of the United Nations - Irrigation and Drainage Paper No. 29, Rev 1, Rome (1985)

Spatial Representation:

The samples were collected at 1 monitoring site: 630EWK001 (East Walker River, at CA/NV state line).

Temporal Representation:

The samples were collected between the dates of 2016-03-17 and 2020-03-11

Environmental Conditions:

QAPP Information:

Generic SWAMP QAPrP

QAPP Information Reference(s):

WQX from the NWQMP for the 2026 Integrated Report in Region 6

Line of Evidence (LOE) for Decision ID 161771, Fluoride	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337602

Pollutant:

Fluoride

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:

Data Reference:

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The California Maximum Contaminant Level for Fluoride incorporated by reference in the Water Quality Control Plan, Lahontan Region is 2 mg/L (Water Quality Control Plan, Lahontan Region).

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2018-01-10 and 2022-06-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633

Line of Evidence (LOE) for Decision ID 161771, Fluoride	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

32237

Pollutant:

Fluoride

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

None

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Zero of 2 samples exceed the MCL for Flouride.

Data Reference:

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

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

California Maximum Contaminant Levels (MCLs) apply to ambient waters under the Lahontan Basin Plan's "Chemical Constituents" objective. The MCL for Fluoride is 2.0 mg/L.

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

Data were collected at the following station: 630EWK001-East Walker River, below Bridgeport Reservoir.

Temporal Representation:

Samples were collected on the following dates: 8/14/2007 11/8/2007

Environmental Conditions:

QAPP Information:

2002 QAMP (Quality Assurance Management Plan) for the State of California's Surface Water Ambient Monitoring Program

QAPP Information Reference(s):

Quality Assurance Management Plan for the State of California's Surface Water Ambient Monitoring Program. Sacramento, CA. State Water Resources Control Board. SWAMP. December 2002 (1st version)

Line of Evidence (LOE) for Decision ID 161771, Fluoride	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

97231

Pollutant:

Fluoride

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

Water Quality Assessment Data for the 2018 solicitation cycle submitted through CEDEN for the SWAMP RWB6 Monitoring (tissue and water).

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

The California Maximum Contaminant Level for Fluoride incorporated by reference in the Water Quality Control Plan, Lahontan Region is 2 mg/L (Water Quality Control Plan, Lahontan Region).

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site(s) (630EWK001)

Temporal Representation:

The samples were collected between the dates of 2010-10-22 and 2015-10-15

Environmental Conditions:

QAPP Information:

Quality Assurance Program Plan and Standard Operating Procedures for SWAMP program

QAPP Information Reference(s):

Quality Assurance Program Plans, Quality Assurance Project Plans, and Standard Operating Procedures for the SWAMP program

Line of Evidence (LOE) for Decision ID 161771, Fluoride	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

338581

Pollutant:

Fluoride

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:

Data Reference:

Benthic, Field, Habitat, Tissue, Toxicity, WQ from the Surface Water Ambient Monitoring Program for the 2026 Integrated Report in Region 6

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

The California Maximum Contaminant Level for Fluoride incorporated by reference in the Water Quality Control Plan, Lahontan Region is 2 mg/L (Water Quality Control Plan, Lahontan Region).

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 630EWK001 (East Walker River, at CA/NV state line).

Temporal Representation:

The samples were collected between the dates of 2017-11-01 and 2021-11-23

Environmental Conditions:

QAPP Information:

Generic SWAMP QAPrP

QAPP Information Reference(s):

WQX from the NWQMP for the 2026 Integrated Report in Region 6


DECISION ID	161772	Region 6
East Walker River, below Bridgeport Reservoir

Pollutant:	Glyphosate
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 161772, Glyphosate	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337603

Pollutant:

Glyphosate

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:

Data Reference:

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The California Maximum Contaminant Level for Glyphosate incorporated by reference in the Water Quality Control Plan, Lahontan Region is 700 ug/L (Water Quality Control Plan, Lahontan Region).

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2019-12-16 and 2020-11-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633

Line of Evidence (LOE) for Decision ID 161772, Glyphosate	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337604

Pollutant:

Glyphosate

LOE Subgroup:

Pollutant-Water

Matrix:

Water

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:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

The evaluation guideline for Glyphosate is the USEPA Aquatic Life Benchmark of 11900 ug/L for a vascular plant (acute).

Guideline Reference:

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2019-12-16 and 2020-11-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):


DECISION ID	161773	Region 6
East Walker River, below Bridgeport Reservoir

Pollutant:	Heptachlor
Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)(2018)
Revision Status	Revised
Impairment from Pollutant or Pollution:	Pollutant

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

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

State Board Review of Regional Board Conclusion and Recommendation:

State Board Decision Recommendation:

Line of Evidence (LOE) for Decision ID 161773, Heptachlor	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337608

Pollutant:

Heptachlor

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:

Water Board staff assessed Nevada Division of Environmental Protection data for East Walker River, below Bridgeport Reservoir to determine beneficial use support, and the results are as follows: 0 of the 0 samples exceeded the evaluation guideline for Heptachlor. Although a total of 2 samples were collected, 2 of these samples were not included in the assessment because the laboratory data reporting limit(s) was above the water quality threshold 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:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The heptachlor criterion for the protection of human health from consumption of organisms only is 0.00021 ug/L (California Toxics Rule, 2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2019-12-16 and 2020-11-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633

Line of Evidence (LOE) for Decision ID 161773, Heptachlor	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337610

Pollutant:

Heptachlor

LOE Subgroup:

Pollutant-Water

Matrix:

Water

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 Nevada Division of Environmental Protection data for East Walker River, below Bridgeport Reservoir to determine beneficial use support, and the results are as follows: 0 of the 0 samples exceeded the evaluation guideline for Heptachlor. Although a total of 2 samples were collected, 2 of these samples were not included in the assessment because the laboratory data reporting limit(s) was above the water quality threshold 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:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The heptachlor criterion continuous concentration (expressed as a 4-day average) to protect aquatic life in freshwater is 0.0038 ug/L (California Toxics Rule, 2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2019-12-16 and 2020-11-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633

Line of Evidence (LOE) for Decision ID 161773, Heptachlor	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337606

Pollutant:

Heptachlor

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Not Recorded

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 Nevada Division of Environmental Protection data for East Walker River, below Bridgeport Reservoir to determine beneficial use support, and the results are as follows: 0 of the 0 samples exceeded the evaluation guideline for Heptachlor. Although a total of 1 samples were collected, 1 of these samples were not included in the assessment because the laboratory data reporting limit(s) was above the water quality threshold 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:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The heptachlor criterion continuous concentration (expressed as a 4-day average) to protect aquatic life in freshwater is 0.0038 ug/L (California Toxics Rule, 2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2020-11-30 and 2020-11-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633

Line of Evidence (LOE) for Decision ID 161773, Heptachlor	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337607

Pollutant:

Heptachlor

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed Nevada Division of Environmental Protection data for East Walker River, below Bridgeport Reservoir to determine beneficial use support, and the results are as follows: 0 of the 0 samples exceeded the evaluation guideline for Heptachlor. Although a total of 2 samples were collected, 2 of these samples were not included in the assessment because the laboratory data reporting limit(s) was above the water quality threshold 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:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The heptachlor criterion for the protection of human health from the consumption of water and organisms is 0.00021 ug/L (California Toxics Rule, 2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2019-12-16 and 2020-11-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633

Line of Evidence (LOE) for Decision ID 161773, Heptachlor	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337609

Pollutant:

Heptachlor

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Not Recorded

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:

Water Board staff assessed Nevada Division of Environmental Protection data for East Walker River, below Bridgeport Reservoir to determine beneficial use support, and the results are as follows: 0 of the 0 samples exceeded the evaluation guideline for Heptachlor. Although a total of 1 samples were collected, 1 of these samples were not included in the assessment because the laboratory data reporting limit(s) was above the water quality threshold 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:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The heptachlor criterion for the protection of human health from consumption of organisms only is 0.00021 ug/L (California Toxics Rule, 2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2020-11-30 and 2020-11-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633

Line of Evidence (LOE) for Decision ID 161773, Heptachlor	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

99202

Pollutant:

Heptachlor

LOE Subgroup:

Pollutant-Tissue

Matrix:

Tissue

Fraction:

Fish fillet

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 SWAMP Sportfish Rivers and Streams data for East Walker River, below Bridgeport Reservoir to determine beneficial use support and the results are as follows 0 of the 1 samples exceeded the water quality standard for Heptachlor. Data were collected for 1 fish species (1 composite(s) of Sacramento Blackfish each composed of 5 fish per composite).

Data Reference:

Water Quality Assessment Data for the 2018 solicitation cycle submitted through CEDEN for SWAMP Sportfish Rivers and Streams.

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

National Academy of Science guidelines (NAS 1972) establish a maximum Heptachlor concentration of 100 ug/Kg (wet weight) in tissue samples for protection of aquatic life from bioaccumulation of toxic substances.

Guideline Reference:

National Academy of Sciences. Water Quality Criteria 1972. EPA-R3-73-033. Washington, D.C.: U.S. Environmental Protection Agency

Spatial Representation:

Data was collected from 1 station(s) with the station code(s): 630EWK002.

Temporal Representation:

Data for this line of evidence were collected between 2011-08-29 and 2011-08-29

Environmental Conditions:

QAPP Information:

Quality Assurance Program Plan and Standard Operating Procedures for SWAMP program

QAPP Information Reference(s):

Quality Assurance Program Plans, Quality Assurance Project Plans, and Standard Operating Procedures for the SWAMP program

Line of Evidence (LOE) for Decision ID 161773, Heptachlor	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337605

Pollutant:

Heptachlor

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Not Recorded

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed Nevada Division of Environmental Protection data for East Walker River, below Bridgeport Reservoir to determine beneficial use support, and the results are as follows: 0 of the 0 samples exceeded the evaluation guideline for Heptachlor. Although a total of 1 samples were collected, 1 of these samples were not included in the assessment because the laboratory data reporting limit(s) was above the water quality threshold 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:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The heptachlor criterion for the protection of human health from the consumption of water and organisms is 0.00021 ug/L (California Toxics Rule, 2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2020-11-30 and 2020-11-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633


DECISION ID	161774	Region 6
East Walker River, below Bridgeport Reservoir

Pollutant:	Heptachlor epoxide
Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)(2018)
Revision Status	Revised
Impairment from Pollutant or Pollution:	Pollutant

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

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

State Board Review of Regional Board Conclusion and Recommendation:

State Board Decision Recommendation:

Line of Evidence (LOE) for Decision ID 161774, Heptachlor epoxide	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337613

Pollutant:

Heptachlor epoxide

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Not Recorded

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 Nevada Division of Environmental Protection data for East Walker River, below Bridgeport Reservoir to determine beneficial use support, and the results are as follows: 0 of the 0 samples exceeded the evaluation guideline for Heptachlor Epoxide. Although a total of 1 samples were collected, 1 of these samples were not included in the assessment because the laboratory data reporting limit(s) was above the water quality threshold 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:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The heptachlor epoxide criterion continuous concentration (expressed as a 4-day average) to protect aquatic life in freshwater is 0.0038 ug/L (California Toxics Rule, 2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2019-12-16 and 2019-12-16

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633

Line of Evidence (LOE) for Decision ID 161774, Heptachlor epoxide	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337611

Pollutant:

Heptachlor epoxide

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Not Recorded

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed Nevada Division of Environmental Protection data for East Walker River, below Bridgeport Reservoir to determine beneficial use support, and the results are as follows: 0 of the 0 samples exceeded the evaluation guideline for Heptachlor Epoxide. Although a total of 1 samples were collected, 1 of these samples were not included in the assessment because the laboratory data reporting limit(s) was above the water quality threshold 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:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The Heptachlor Epoxide criteria for the protection of human health from the consumption of water and organisms is 0.00010 ug/L (California Toxics Rule, 2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2019-12-16 and 2019-12-16

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633

Line of Evidence (LOE) for Decision ID 161774, Heptachlor epoxide	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

99459

Pollutant:

Heptachlor epoxide

LOE Subgroup:

Pollutant-Tissue

Matrix:

Tissue

Fraction:

Fish fillet

Beneficial Use:

Commercial or recreational collection of fish, shellfish, or organisms

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Waterboard staff assessed SWAMP Sportfish Rivers and Streams data for East Walker River, below Bridgeport Reservoir to determine beneficial use support and the results are as follows: Zero of Zero samples exceeded the water quality standard for Heptachlor Epoxide. Although data was collected for 1 fish species (1 composite(s) of Sacramento Blackfish each composed of 5 fish per composite), all 1 sample(s) had to be thrown out due to quantitation issues.

Data Reference:

Water Quality Assessment Data for the 2018 solicitation cycle submitted through CEDEN for SWAMP Sportfish Rivers and Streams.

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

The modified OEHHA Fish Contaminant Goal for heptachlor epoxide in fish tissue is 0.93 ppb. This screening level assumes an average body weight of 70 kg and a consumption rate of 32 g/day for a 30 year exposure over a 70-year lifetime. This constituent is a carcinogen therefore the risk level is set to one in a million. A cooking reduction factor of 1 is applied for skin-off fillets. (Klasing, S., and R. Brodberg, 2008; OEHHA, 1999)

Guideline Reference:

Development of Fish Contaminant Goals and Advisory Tissue Levels for Common Contaminants in California Sport Fish: Chlordane, DDTs, Dieldrin, Methylmercury, PCBs, Selenium, and Toxaphene

Guideline Reference:

Public Health Goal for Heptachlor and Heptachlor Epoxide in Drinking Water

Spatial Representation:

Data was collected from 1 station(s) with the station code(s): 630EWK002.

Temporal Representation:

Data for this line of evidence were collected between 2011-08-29 and 2011-08-29

Environmental Conditions:

QAPP Information:

Quality Assurance Program Plan and Standard Operating Procedures for SWAMP program

QAPP Information Reference(s):

Quality Assurance Program Plans, Quality Assurance Project Plans, and Standard Operating Procedures for the SWAMP program

Line of Evidence (LOE) for Decision ID 161774, Heptachlor epoxide	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

99461

Pollutant:

Heptachlor epoxide

LOE Subgroup:

Pollutant-Tissue

Matrix:

Tissue

Fraction:

Fish fillet

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 SWAMP Sportfish Rivers and Streams data for East Walker River, below Bridgeport Reservoir to determine beneficial use support and the results are as follows 0 of the 1 samples exceeded the water quality standard for Heptachlor Epoxide. Data were collected for 1 fish species (1 composite(s) of Sacramento Blackfish each composed of 5 fish per composite).

Data Reference:

Water Quality Assessment Data for the 2018 solicitation cycle submitted through CEDEN for SWAMP Sportfish Rivers and Streams.

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

National Academy of Science guidelines (NAS 1972) establish a maximum Heptachlor Epoxide concentration of 100 ug/Kg (wet weight) in tissue samples for protection of aquatic life from bioaccumulation of toxic substances.

Guideline Reference:

National Academy of Sciences. Water Quality Criteria 1972. EPA-R3-73-033. Washington, D.C.: U.S. Environmental Protection Agency

Spatial Representation:

Data was collected from 1 station(s) with the station code(s): 630EWK002.

Temporal Representation:

Data for this line of evidence were collected between 2011-08-29 and 2011-08-29

Environmental Conditions:

QAPP Information:

Quality Assurance Program Plan and Standard Operating Procedures for SWAMP program

QAPP Information Reference(s):

Quality Assurance Program Plans, Quality Assurance Project Plans, and Standard Operating Procedures for the SWAMP program

Line of Evidence (LOE) for Decision ID 161774, Heptachlor epoxide	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337612

Pollutant:

Heptachlor epoxide

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Not Recorded

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:

Water Board staff assessed Nevada Division of Environmental Protection data for East Walker River, below Bridgeport Reservoir to determine beneficial use support, and the results are as follows: 0 of the 0 samples exceeded the evaluation guideline for Heptachlor Epoxide. Although a total of 1 samples were collected, 1 of these samples were not included in the assessment because the laboratory data reporting limit(s) was above the water quality threshold 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:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The Heptachlor Epoxide criteria for the protection of human health from consumption of organisms only is 0.00011 ug/L (California Toxics Rule, 2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2019-12-16 and 2019-12-16

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633


DECISION ID	161775	Region 6
East Walker River, below Bridgeport Reservoir

Pollutant:	Hexachlorobenzene/ HCB
Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)(2018)
Revision Status	Revised
Impairment from Pollutant or Pollution:	Pollutant

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

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

State Board Review of Regional Board Conclusion and Recommendation:

State Board Decision Recommendation:

Line of Evidence (LOE) for Decision ID 161775, Hexachlorobenzene/ HCB	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337614

Pollutant:

Hexachlorobenzene/ HCB

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed Nevada Division of Environmental Protection data for East Walker River, below Bridgeport Reservoir to determine beneficial use support, and the results are as follows: 0 of the 0 samples exceeded the evaluation guideline for Hexachlorobenzene. Although a total of 2 samples were collected, 2 of these samples were not included in the assessment because the laboratory data reporting limit(s) was above the water quality threshold 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:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The Hexachlorobenzene criteria for the protection of human health from the consumption of water and organisms is 0.00075 ug/L (California Toxics Rule, 2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2019-12-16 and 2020-11-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633

Line of Evidence (LOE) for Decision ID 161775, Hexachlorobenzene/ HCB	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

99431

Pollutant:

Hexachlorobenzene/ HCB

LOE Subgroup:

Pollutant-Tissue

Matrix:

Tissue

Fraction:

Fish fillet

Beneficial Use:

Commercial or recreational collection of fish, shellfish, or organisms

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed SWAMP Sportfish Rivers and Streams data for East Walker River, below Bridgeport Reservoir to determine beneficial use support and the results are as follows 0 of the 1 samples exceeded the water quality standard for Hexachlorobenzene. Data were collected for 1 fish species (1 composite(s) of Sacramento Blackfish each composed of 5 fish per composite).

Data Reference:

Water Quality Assessment Data for the 2018 solicitation cycle submitted through CEDEN for SWAMP Sportfish Rivers and Streams.

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

The modified OEHHA Fish Contaminant Goal for hexachlorobenzene in fish tissue is 2.8 ppb. This screening level assumes an average body weight of 70 kg and a consumption rate of 32 g/day for a 30 year exposure over a 70-year lifetime. This constituent is a carcinogen therefore the risk level is set to one in a million. A cooking reduction factor of 1 is applied for skin-off fillets. (Klasing, S., and R. Brodberg, 2008; OEHHA, 2005)

Guideline Reference:

Development of Fish Contaminant Goals and Advisory Tissue Levels for Common Contaminants in California Sport Fish: Chlordane, DDTs, Dieldrin, Methylmercury, PCBs, Selenium, and Toxaphene

Guideline Reference:

Air Toxics Hotspots Program Risk Assessment Guidelines. Part ll Technical Support Document for Describing Available Cancer Potency Values.

Spatial Representation:

Data was collected from 1 station(s) with the station code(s): 630EWK002.

Temporal Representation:

Data for this line of evidence were collected between 2011-08-29 and 2011-08-29

Environmental Conditions:

QAPP Information:

Quality Assurance Program Plan and Standard Operating Procedures for SWAMP program

QAPP Information Reference(s):

Quality Assurance Program Plans, Quality Assurance Project Plans, and Standard Operating Procedures for the SWAMP program

Line of Evidence (LOE) for Decision ID 161775, Hexachlorobenzene/ HCB	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337615

Pollutant:

Hexachlorobenzene/ HCB

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:

Water Board staff assessed Nevada Division of Environmental Protection data for East Walker River, below Bridgeport Reservoir to determine beneficial use support, and the results are as follows: 0 of the 0 samples exceeded the evaluation guideline for Hexachlorobenzene. Although a total of 2 samples were collected, 2 of these samples were not included in the assessment because the laboratory data reporting limit(s) was above the water quality threshold 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:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The Hexachlorobenzene criteria for the protection of human health from consumption of organisms only is 0.00077 ug/L (California Toxics Rule, 2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2019-12-16 and 2020-11-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633


DECISION ID	161776	Region 6
East Walker River, below Bridgeport Reservoir

Pollutant:	Hexachlorobutadiene
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:

Line of Evidence (LOE) for Decision ID 161776, Hexachlorobutadiene	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337617

Pollutant:

Hexachlorobutadiene

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Commercial or recreational collection of fish, shellfish, or organisms

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The Hexachlorobutadiene criteria for the protection of human health from consumption of organisms only is 50 ug/L (California Toxics Rule, 2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2020-11-30 and 2020-11-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633

Line of Evidence (LOE) for Decision ID 161776, Hexachlorobutadiene	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337616

Pollutant:

Hexachlorobutadiene

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed Nevada Division of Environmental Protection data for East Walker River, below Bridgeport Reservoir to determine beneficial use support, and the results are as follows: 0 of the 0 samples exceeded the evaluation guideline for Hexachlorobutadiene. Although a total of 1 samples were collected, 1 of these samples were not included in the assessment because the laboratory data reporting limit(s) was above the water quality threshold 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:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The Hexachlorobutadiene criteria for the protection of human health from the consumption of water and organisms is 0.44 ug/L (California Toxics Rule, 2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2020-11-30 and 2020-11-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633


DECISION ID	161777	Region 6
East Walker River, below Bridgeport Reservoir

Pollutant:	Hexachlorocyclopentadiene
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 161777, Hexachlorocyclopentadiene	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337619

Pollutant:

Hexachlorocyclopentadiene

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Commercial or recreational collection of fish, shellfish, or organisms

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The Hexachlorocyclopentadiene criteria for the protection of human health from consumption of organisms only is 17,000 ug/L (California Toxics Rule, 2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2019-12-16 and 2020-11-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633

Line of Evidence (LOE) for Decision ID 161777, Hexachlorocyclopentadiene	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337618

Pollutant:

Hexachlorocyclopentadiene

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:

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The California Maximum Contaminant Level for Hexachlorocyclopentadiene incorporated by reference in the Water Quality Control Plan, Lahontan Region is 50 ug/L (Water Quality Control Plan, Lahontan Region).

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2019-12-16 and 2020-11-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633


DECISION ID	168736	Region 6
East Walker River, below Bridgeport Reservoir

Pollutant:	Indicator Bacteria
Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)(2018)
Revision Status	Revised
Impairment from Pollutant or Pollution:	Pollutant

Regional Board Conclusion:	This pollutant is being considered for placement on the CWA section 303(d) List under section 3.2 of the Listing Policy. Under section 3.2 a single line of evidence is necessary to assess listing status. Four lines of evidence are available in the administrative record to assess this pollutant. 0 of 52 samples exceed the objective. (Fecal coliform lines of evidence used in previous indicator bacteria decisions in the Lahontan Region have been removed, starting in the 2026 Integrated Report, since the Lahontan Region's fecal coliform water quality objective was removed from the Basin Plan in 2024). Based on the readily available data and information, the weight of evidence indicates that there is sufficient justification against placing this water segment-pollutant combination on the CWA section 303(d) List. This conclusion is based on the staff findings that: 1. The data used satisfies the data quality requirements of section 6.1.4 of the Policy. 2. The data used satisfies the data quantity requirements of section 6.1.5 of the Policy. 3. 0 of 52 samples exceeded the objective and this does not exceed the allowable frequency listed in Table 3.2 of the Listing Policy. 4. Pursuant to section 3.11 of the Listing Policy, no additional data and information are available indicating that standards are not met.

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

State Board Review of Regional Board Conclusion and Recommendation:

State Board Decision Recommendation:

Line of Evidence (LOE) for Decision ID 168736, Indicator Bacteria	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

99702

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:

Water Board staff assessed RWB6_BACT_Monitoring data for East Walker River, below Bridgeport Reservoir to determine beneficial use support and the results are as follows: 0 of the 2 samples exceeded the Statistical Threshold Value (STV) water quality standard for E. coli. The STV is based on a 10% exceedance rate that is calculated monthly.

Data Reference:

Water Quality Assessment Data for the 2018 solicitation cycle submitted through CEDEN for Regional Water Board 6 Bacteria Monitoring.

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

The bacteria water quality objective applicable to all waters, except Lake Tahoe, where the salinity is less than 10 parts per thousand (ppth) 95 percent or more of the time is a STATISTICAL THRESHOLD VALUE (STV) of 320 cfu/100 mL not to be exceeded more than 10 percent of the time (calculated monthly).

Objective/Criterion Reference:

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

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site(s), station(s): 630EWK001

Temporal Representation:

The samples were collected between the days of 2015-08-19 and 2016-09-28 .

Environmental Conditions:

QAPP Information:

Quality Assurance Program Plan and Standard Operating Procedures for SWAMP program

QAPP Information Reference(s):

Quality Assurance Program Plans, Quality Assurance Project Plans, and Standard Operating Procedures for the SWAMP program

Line of Evidence (LOE) for Decision ID 168736, Indicator Bacteria	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

336882

Pollutant:

Escherichia coli (E. coli)

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

STV

Beneficial Use:

Water Contact Recreation

Number of Samples:

Number of Exceedances:

Data and Information Type:

PATHOGEN MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed Nevada Division of Environmental Protection data for East Walker River, below Bridgeport Reservoir to determine beneficial use support and the results are as follows: 0 of the 6 samples exceeded the Statistical Threshold Value (STV) water quality threshold for E. coli. The STV is based on a 10% exceedance rate that is calculated monthly.

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The bacteria water quality objective to protect the REC-1 beneficial use in waters other than Lake Thaoe, where the salinity is less than 1 parts per thousand 95 percent or more of the time applies a statistical threshold value to E. coli of 320 cfu/100 mL, not to be exceeded by more than 10 percent of samples within a calendar month (ISWEBE 2018).

Objective/Criterion Reference:

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

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site(s), station(s): 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the days of 2012-06-04 and 2016-10-10 .

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633

Line of Evidence (LOE) for Decision ID 168736, Indicator Bacteria	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

336842

Pollutant:

Escherichia coli (E. coli)

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

STV

Beneficial Use:

Water Contact Recreation

Number of Samples:

Number of Exceedances:

Data and Information Type:

PATHOGEN MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed SWAMP RWB6 Monitoring data for East Walker River, below Bridgeport Reservoir to determine beneficial use support and the results are as follows: 0 of the 14 samples exceeded the Statistical Threshold Value (STV) water quality threshold for E. coli. The STV is based on a 10% exceedance rate that is calculated monthly.

Data Reference:

Benthic, Field, Habitat, Tissue, Toxicity, WQ from the Surface Water Ambient Monitoring Program for the 2026 Integrated Report in Region 6

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

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

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site(s), station(s): 630EWK001 (East Walker River, at CA/NV state line).

Temporal Representation:

The samples were collected between the days of 2016-01-19 and 2021-11-23 .

Environmental Conditions:

QAPP Information:

Generic SWAMP QAPrP

QAPP Information Reference(s):

Water Quality Assessment Data for the 2018 solicitation cycle submitted through CEDEN for the SWAMP RWB6 Monitoring (tissue and water).

Line of Evidence (LOE) for Decision ID 168736, Indicator Bacteria	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

96927

Pollutant:

Escherichia coli (E. coli)

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

STV

Beneficial Use:

Water Contact Recreation

Number of Samples:

Number of Exceedances:

Data and Information Type:

PATHOGEN MONITORING

Data Used to Assess Water Quality:

Data were collected by Lahontan staff for the Surface Water Ambient Monitoring Program (SWAMP) RWB6 Monitoring program, and for a supplemental TMDL Integrated Report Special Study. The TMDL Special Study was developed by Lahontan Planning and SWAMP staff to provide additional data to the quarterly SWAMP monitoring. The purpose was to gain a better temporal understanding of levels of specific pollutants in the waterbody. To ensure the two datasets could be viably analyzed as one, the TMDL Special Study followed the same sampling protocol as SWAMP. Accordingly, the two datasets have been combined for this assessment to reflect the intended design and to best characterize conditions in the watershed. Water Board staff determined beneficial use support, and the results are as follows: 0 of the 30 samples exceeded exceeded the Statistical Threshold Value (STV) water quality standard for E. coli. The STV is based on a 10% exceedance rate that is calculated monthly.

Data Reference:

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

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

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site, station: 630EWK001

Temporal Representation:

The samples were collected between the days of 2011-06-13 and 2016-22-12 .

Environmental Conditions:

QAPP Information:

Quality Assurance Program Plan and Standard Operating Procedures for SWAMP program

QAPP Information Reference(s):

Quality Assurance Program Plans, Quality Assurance Project Plans, and Standard Operating Procedures for the SWAMP program


DECISION ID	161779	Region 6
East Walker River, below Bridgeport Reservoir

Pollutant:	Isophorone
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 161779, Isophorone	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337628

Pollutant:

Isophorone

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Commercial or recreational collection of fish, shellfish, or organisms

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The Isophorone criteria for the protection of human health from consumption of organisms only is 600 ug/L (California Toxics Rule, 2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2019-12-16 and 2020-11-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633

Line of Evidence (LOE) for Decision ID 161779, Isophorone	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337629

Pollutant:

Isophorone

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:

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The Isophorone criteria for the protection of human health from the consumption of water and organisms is 8.4 ug/L (California Toxics Rule, 2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2019-12-16 and 2020-11-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633


DECISION ID	161780	Region 6
East Walker River, below Bridgeport Reservoir

Pollutant:	Lead
Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)(2018)
Revision Status	Revised
Impairment from Pollutant or Pollution:	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 161780, Lead	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

5120

Pollutant:

Lead

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

Fixed station physical/chemical (conventional plus toxic pollutants)

Data Used to Assess Water Quality:

The U.S. Geological survey sampled lead under the Region 6 SWAMP program in 2001 and 2002. Concentrations of total recoverable lead in four quarterly samples were below the detection limit. Per listing policy Section 6.1.5.5, the MCL is presumed to be attained.

Data Reference:

2007. SWAMP Data for the West Walker River and East Walker River Hydrologic Units

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

California Maximum Contaminant Levels (MCLs) apply to ambient waters under the Lahontan Basin Plan's "Chemical Constituents" objective. The MCL for lead is 15 ug/L.

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

One station, East Walker River at the California-Nevada State Line, was sampled.

Temporal Representation:

Four quarterly samples were collected in 2001 and 2002.

Environmental Conditions:

QAPP Information:

Data meet the quality assurance requirements of the SWAMP QAPP.

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 161780, Lead	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337636

Pollutant:

Lead

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

California Maximum Contaminant Levels (MCLs) apply to ambient waters under the Lahontan Basin Plan's 'Chemical Constituents' objective. The MCL for lead is 15 ug/L.

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2018-04-04 and 2022-06-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633

Line of Evidence (LOE) for Decision ID 161780, Lead	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

5121

Pollutant:

Lead

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

Fixed station physical/chemical (conventional plus toxic pollutants)

Data Used to Assess Water Quality:

The U.S. Geological survey sampled lead under the Region 6 SWAMP program in 2001 and 2002. Dissolved lead concentrations in four samples included two values below the detection level, one estimated value, and one 0.16 ug/L value. The CTR standards were not exceeded.

Data Reference:

2007. SWAMP Data for the West Walker River and East Walker River Hydrologic Units

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

The California Toxic Rule (CTR) standards for lead are dependent on hardness. At the reported hardness levels for this station, the acute (1 hour average) standard ranged from 32.06 to 39.33 ug/L. The chronic (4 day average) standard ranged from 1.25 to 1.53 ug/L.

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

One station, East Walker River at the California-Nevada State Line, was sampled.

Temporal Representation:

Four quarterly samples were collected in 2001 and 2002.

Environmental Conditions:

QAPP Information:

Data meet the quality assurance requirements of the SWAMP QAPP.

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 161780, Lead	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337633

Pollutant:

Lead

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The dissolved lead criterion continuous concentration (expressed as a 4-day average) to protect aquatic life in freshwater is hardness dependent. The criterion when calculated using a default hardness of 100 mg/L is 2.5 ug/L (California Toxics Rule, 2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2018-04-04 and 2022-06-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633

Line of Evidence (LOE) for Decision ID 161780, Lead	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337631

Pollutant:

Lead

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:

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

California Maximum Contaminant Levels (MCLs) apply to ambient waters under the Lahontan Basin Plan's 'Chemical Constituents' objective. The MCL for lead is 15 ug/L.

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2018-04-04 and 2022-06-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633


DECISION ID	102643	Region 6
East Walker River, below Bridgeport Reservoir

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

Regional Board Conclusion:	This pollutant is being considered for placement on the CWA section 303(d) List under section 3.1 of the Listing Policy. Under section 3.1 a single line of evidence is necessary to assess listing status. Two lines of evidence are available in the administrative record to assess this pollutant that are both based on the same single fish tissue sample assessed for COLD and COMM. The single sample does not exceed the guideline for either COLD or COMM. 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 samples exceeded the guideline for both COLD and COMM 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. The readily available data and information is insufficient to determine, with the power and confidence of the Listing Policy, the applicable beneficial use support rating.

State Board Review of Regional Board Conclusion and Recommendation:

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

Line of Evidence (LOE) for Decision ID 102643, Lindane/gamma Hexachlorocyclohexane (gamma-HCH)	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

99385

Pollutant:

Lindane/gamma Hexachlorocyclohexane (gamma-HCH)

LOE Subgroup:

Pollutant-Tissue

Matrix:

Tissue

Fraction:

Fish fillet

Beneficial Use:

Commercial or recreational collection of fish, shellfish, or organisms

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed SWAMP Sportfish Rivers and Streams data for East Walker River, below Bridgeport Reservoir to determine beneficial use support and the results are as follows 0 of the 1 samples exceeded the water quality standard for HCH, gamma-. Data were collected for 1 fish species (1 composite(s) of Sacramento Blackfish each composed of 5 fish per composite).

Data Reference:

Water Quality Assessment Data for the 2018 solicitation cycle submitted through CEDEN for SWAMP Sportfish Rivers and Streams.

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

The modified OEHHA Fish Contaminant Goal for lindane in fish tissue is 4.6 ppb. This screening level assumes an average body weight of 70 kg and a consumption rate of 32 g/day for a 30 year exposure over a 70-year lifetime. This constituent is a carcinogen therefore the risk level is set to one in a million. A cooking reduction factor of 1 is applied for skin-off fillets. (Klasing, S., and R. Brodberg, 2008; OEHHA, 2005)

Guideline Reference:

Development of Fish Contaminant Goals and Advisory Tissue Levels for Common Contaminants in California Sport Fish: Chlordane, DDTs, Dieldrin, Methylmercury, PCBs, Selenium, and Toxaphene

Guideline Reference:

Air Toxics Hotspots Program Risk Assessment Guidelines. Part ll Technical Support Document for Describing Available Cancer Potency Values.

Spatial Representation:

Data was collected from 1 station(s) with the station code(s): 630EWK002.

Temporal Representation:

Data for this line of evidence were collected between 2011-08-29 and 2011-08-29

Environmental Conditions:

QAPP Information:

Quality Assurance Program Plan and Standard Operating Procedures for SWAMP program

QAPP Information Reference(s):

Quality Assurance Program Plans, Quality Assurance Project Plans, and Standard Operating Procedures for the SWAMP program

Line of Evidence (LOE) for Decision ID 102643, Lindane/gamma Hexachlorocyclohexane (gamma-HCH)	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

99386

Pollutant:

Lindane/gamma Hexachlorocyclohexane (gamma-HCH)

LOE Subgroup:

Pollutant-Tissue

Matrix:

Tissue

Fraction:

Fish fillet

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 SWAMP Sportfish Rivers and Streams data for East Walker River, below Bridgeport Reservoir to determine beneficial use support and the results are as follows 0 of the 1 samples exceeded the water quality standard for HCH, gamma-. Data were collected for 1 fish species (1 composite(s) of Sacramento Blackfish each composed of 5 fish per composite).

Data Reference:

Water Quality Assessment Data for the 2018 solicitation cycle submitted through CEDEN for SWAMP Sportfish Rivers and Streams.

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

National Academy of Science guidelines (NAS 1972) establish a maximum Lindane concentration of 100 ug/Kg (wet weight) in tissue samples for protection of aquatic life from bioaccumulation of toxic substances.

Guideline Reference:

National Academy of Sciences. Water Quality Criteria 1972. EPA-R3-73-033. Washington, D.C.: U.S. Environmental Protection Agency

Spatial Representation:

Data was collected from 1 station(s) with the station code(s): 630EWK002.

Temporal Representation:

Data for this line of evidence were collected between 2011-08-29 and 2011-08-29

Environmental Conditions:

QAPP Information:

Quality Assurance Program Plan and Standard Operating Procedures for SWAMP program

QAPP Information Reference(s):

Quality Assurance Program Plans, Quality Assurance Project Plans, and Standard Operating Procedures for the SWAMP program


DECISION ID	170625	Region 6
East Walker River, below Bridgeport Reservoir

Pollutant:	Mercury
Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)(2018)
Revision Status	Revised
Impairment from Pollutant or Pollution:	Pollutant

Regional Board Conclusion:	This pollutant is being considered for placement on the CWA section 303(d) List under section 3.1 of the Listing Policy. Under section 3.1 a single line of evidence is necessary to assess listing status. Ten lines of evidence are available in the administrative record to assess this pollutant, two that assess for mercury in water and eight that assess fish tissue. One of one fish tissues samples exceed the COMM tissue objective for mercury. One of one samples exceed the WILD tissue objective. Zero of 14 water samples exceed the COLD criteria. Zero of four samples exceed the MUN critera. The exceedances in the fish tissue data indicate this waterbody is likely impaired for mercury, however more data is needed to confirm this. 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. One of one fish tissues samples exceed the COMM tissue objective for mercury. One of one samples exceed the WILD tissue objective. Zero of 14 samples exceed the COLD criteria for mercury in water. Zero of four samples exceed the MUN criteria. 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. Since the single sample did exceed the mercury tissue objectives for COMM and WILD, this indicates mercury impairment is probable for this water body.

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:

Line of Evidence (LOE) for Decision ID 170625, Mercury	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

133156

Pollutant:

Mercury

LOE Subgroup:

Pollutant-Tissue

Matrix:

Tissue

Fraction:

Fish fillet

Beneficial Use:

Wildlife Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed SWAMP Sportfish Rivers and Streams data for East Walker River, below Bridgeport Reservoir to determine beneficial use support and the results are as follows: 1 of the 1 samples exceeded the water quality standard for Mercury. This LOE contains data only for trophic level 3 fish. The concentration of Mercury in fish collected within the same calendar year, for the same trophic level were averaged into a single sample for comparison with the objective. A total of 7 fish were aggregated into 1 annual averages, which consisted of 2 fish species (1 composite(s) of Rainbow Trout each composed of 1 fish per composite, 6 composite(s) of Sacramento Blackfish each composed of 1 fish per composite). Of these annual averages, 1 average(s), (Year(s): 2011) exceeded the objective.

Data Reference:

Water Quality Assessment Data for the 2018 solicitation cycle submitted through CEDEN for SWAMP Sportfish Rivers and Streams.

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

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

Guideline Reference:

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

Spatial Representation:

Data was collected from 1 station(s) with the station code(s): 630EWK002.

Temporal Representation:

Data for this line of evidence were collected between 2011-08-29 and 2011-09-06

Environmental Conditions:

QAPP Information:

Quality Assurance Program Plan and Standard Operating Procedures for SWAMP program

QAPP Information Reference(s):

Quality Assurance Program Plans, Quality Assurance Project Plans, and Standard Operating Procedures for the SWAMP program

Line of Evidence (LOE) for Decision ID 170625, Mercury	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337658

Pollutant:

Mercury

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

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

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2018-04-04 and 2022-06-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633

Line of Evidence (LOE) for Decision ID 170625, Mercury	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337655

Pollutant:

Mercury

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Commercial or recreational collection of fish, shellfish, or organisms

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed Nevada Division of Environmental Protection data for East Walker River, below Bridgeport Reservoir to determine beneficial use support, and the results are as follows: 0 of the 0 samples exceeded the evaluation guideline for Mercury. Although a total of 5 samples were collected, 5 of these samples were not included in the assessment because the laboratory data reporting limit(s) was above the water quality threshold 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:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

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

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2018-04-04 and 2022-06-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633

Line of Evidence (LOE) for Decision ID 170625, Mercury	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337657

Pollutant:

Mercury

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed Nevada Division of Environmental Protection data for East Walker River, below Bridgeport Reservoir to determine beneficial use support, and the results are as follows: 0 of the 0 samples exceeded the evaluation guideline for Mercury. Although a total of 5 samples were collected, 5 of these samples were not included in the assessment because the laboratory data reporting limit(s) was above the water quality threshold 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:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

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

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2018-04-04 and 2022-06-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633

Line of Evidence (LOE) for Decision ID 170625, Mercury	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337660

Pollutant:

Mercury

LOE Subgroup:

Pollutant-Water

Matrix:

Water

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:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

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

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2018-04-04 and 2022-06-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633

Line of Evidence (LOE) for Decision ID 170625, Mercury	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337648

Pollutant:

Mercury

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed Nevada Division of Environmental Protection data for East Walker River, below Bridgeport Reservoir to determine beneficial use support, and the results are as follows: 0 of the 0 samples exceeded the evaluation guideline for Mercury. Although a total of 5 samples were collected, 5 of these samples were not included in the assessment because the laboratory data reporting limit(s) was above the water quality threshold 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:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

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

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2018-04-04 and 2022-06-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633

Line of Evidence (LOE) for Decision ID 170625, Mercury	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337659

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:

Water Board staff assessed Nevada Division of Environmental Protection data for East Walker River, below Bridgeport Reservoir to determine beneficial use support, and the results are as follows: 0 of the 0 samples exceeded the evaluation guideline for Mercury. Although a total of 5 samples were collected, 5 of these samples were not included in the assessment because the laboratory data reporting limit(s) was above the water quality threshold 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:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

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

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2018-04-04 and 2022-06-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633

Line of Evidence (LOE) for Decision ID 170625, Mercury	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

5082

Pollutant:

Mercury

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

Fixed station physical/chemical (conventional plus toxic pollutants)

Data Used to Assess Water Quality:

The U.S. Geological Survey sampled mercury under the Region 6 SWAMP program in 2001 and 2002. Mercury concentrations in four samples ranged from less than 0.01 ug/L to 0.01 ug/L. The MCL was not violated.

Data Reference:

2007. SWAMP Data for the West Walker River and East Walker River Hydrologic Units

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

California Maximum Contaminant Levels apply to ambient waters under the Lahontan Basin Plan's "Chemical Constituents" objective. The MCL tor inorganic mercury is 2 ug/L.

The California Toxics Rule water and fish consumption standard for mercury is 0.050 ug/L.

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

One station, East Walker River at the California-Nevada State Line, was sampled.

Temporal Representation:

Four quarterly samples were collected in 2001 and 2002.

Environmental Conditions:

QAPP Information:

Data meet the quality assurance requirements of the SWAMP QAPP.

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 170625, Mercury	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

5764

Pollutant:

Mercury

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

Fixed station physical/chemical (conventional plus toxic pollutants)

Data Used to Assess Water Quality:

The U.S. Geological Survey sampled mercury quarterly in the East Walker River under the Region 6 SWAMP program in 2001 and 2002. Three of four total mercury samples were below the detection level, and one was 0.01 ug/L The criteria were not violated.

Data Reference:

2007. SWAMP Data for the West Walker River and East Walker River Hydrologic Units

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

The U.S. Environmental Protection Agency (USEPA) freshwater aquatic life criteria (expressed as total mercury) are a 4- day average of 0.77 ug/L and a 1-hour maximum of 1.4 ug/L

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

2007. SWAMP Data for the West Walker River and East Walker River Hydrologic Units

Spatial Representation:

One station, East Walker River at the California-Nevada State Line, was sampled.

Temporal Representation:

Four quarterly samples were collected in 2001 and 2002.

Environmental Conditions:

QAPP Information:

Data meet the quality assurance requirements of the SWAMP QAPP.

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 170625, Mercury	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

133071

Pollutant:

Mercury

LOE Subgroup:

Pollutant-Tissue

Matrix:

Tissue

Fraction:

Fish fillet

Beneficial Use:

Commercial or recreational collection of fish, shellfish, or organisms

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed SWAMP Sportfish Rivers and Streams data for East Walker River, below Bridgeport Reservoir to determine beneficial use support and the results are as follows: 1 of the 1 samples exceeded the water quality standard for Mercury. This LOE contains data only for trophic level 3 fish. The concentration of Mercury in fish collected within the same calendar year, for the same trophic level were averaged into a single sample for comparison with the objective. A total of 7 fish were aggregated into 1 annual averages, which consisted of 2 fish species (1 composite(s) of Rainbow Trout each composed of 1 fish per composite, 6 composite(s) of Sacramento Blackfish each composed of 1 fish per composite). Of these annual averages, 1 average(s), (Year(s): 2011) exceeded the objective. This LOE does not contain data from fish whos average length was outside of the legal size limits as described by the California Department of Fish and Wildlife Fishing Regulations.

Data Reference:

Water Quality Assessment Data for the 2018 solicitation cycle submitted through CEDEN for SWAMP Sportfish Rivers and Streams.

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

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

Guideline Reference:

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

Spatial Representation:

Data was collected from 1 station(s) with the station code(s): 630EWK002.

Temporal Representation:

Data for this line of evidence were collected between 2011-08-29 and 2011-09-06

Environmental Conditions:

QAPP Information:

Quality Assurance Program Plan and Standard Operating Procedures for SWAMP program

QAPP Information Reference(s):

Quality Assurance Program Plans, Quality Assurance Project Plans, and Standard Operating Procedures for the SWAMP program


DECISION ID	161810	Region 6
East Walker River, below Bridgeport Reservoir

Pollutant:	Methiocarb
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 161810, Methiocarb	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337664

Pollutant:

Methiocarb

LOE Subgroup:

Pollutant-Water

Matrix:

Water

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:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

The evaluation guideline for methiocarb is the USEPA Aquatic Life Benchmark of 2.75 ug/L for an invertebrate (acute).

Guideline Reference:

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2019-12-16 and 2020-11-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):


DECISION ID	161811	Region 6
East Walker River, below Bridgeport Reservoir

Pollutant:	Methomyl
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 161811, Methomyl	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337665

Pollutant:

Methomyl

LOE Subgroup:

Pollutant-Water

Matrix:

Water

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:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

The evaluation guideline for methomyl is the USEPA Aquatic Life Benchmark of 0.6 ug/L for an invertebrate (chronic).

Guideline Reference:

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2019-12-16 and 2020-11-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 161811, Methomyl	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337666

Pollutant:

Methomyl

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:

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

The USEPA drinking water lifetime health advisory for methomyl is 200 ug/L.

Guideline Reference:

2018 Edition of the Drinking Water Standards and Health Advisories

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2019-12-16 and 2020-11-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633


DECISION ID	161782	Region 6
East Walker River, below Bridgeport Reservoir

Pollutant:	Methoxychlor
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 161782, Methoxychlor	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337667

Pollutant:

Methoxychlor

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:

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The California Maximum Contaminant Level for Methoxychlor incorporated by reference in the Water Quality Control Plan, Lahontan Region is 30 ug/L (Water Quality Control Plan, Lahontan Region).

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2019-12-16 and 2020-11-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633

Line of Evidence (LOE) for Decision ID 161782, Methoxychlor	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337668

Pollutant:

Methoxychlor

LOE Subgroup:

Pollutant-Water

Matrix:

Water

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 Nevada Division of Environmental Protection data for East Walker River, below Bridgeport Reservoir to determine beneficial use support, and the results are as follows: 0 of the 0 samples exceeded the evaluation guideline for Methoxychlor. Although a total of 2 samples were collected, 2 of these samples were not included in the assessment because the laboratory data reporting limit(s) was above the water quality threshold 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:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

The USEPA national ambient water quality criterion for freshwater aquatic life Criterion Continuous Concentration (CCC) expressed as a 4-day average for methoxychlor is 0.03 ug/L.

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2019-12-16 and 2020-11-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633


DECISION ID	161783	Region 6
East Walker River, below Bridgeport Reservoir

Pollutant:	Methyl chloride (Chloromethane)
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:

Line of Evidence (LOE) for Decision ID 161783, Methyl chloride (Chloromethane)	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337535

Pollutant:

Methyl chloride (Chloromethane)

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Not Recorded

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

The USEPA Health Advisory for 10 day exposure of a 10 kg-Child to chloromethane as a drinking water level is a concentration of 0.4 mg/L.

Guideline Reference:

2012 Edition of the Drinking Water Standards and Health Advisories

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2020-11-30 and 2020-11-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633


DECISION ID	161784	Region 6
East Walker River, below Bridgeport Reservoir

Pollutant:	Methyl isobutyl ketone (Methyl-2-Pentanone)
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:

Line of Evidence (LOE) for Decision ID 161784, Methyl isobutyl ketone (Methyl-2-Pentanone)	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337669

Pollutant:

Methyl isobutyl ketone (Methyl-2-Pentanone)

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Not Recorded

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Drinking Water Notification and Response Levels: An Overview

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2020-11-30 and 2020-11-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633


DECISION ID	161814	Region 6
East Walker River, below Bridgeport Reservoir

Pollutant:	Metolachlor
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 161814, Metolachlor	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337671

Pollutant:

Metolachlor

LOE Subgroup:

Pollutant-Water

Matrix:

Water

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:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

The evaluation guideline for metolachlor is the USEPA Aquatic Life Benchmark of 8 ug/L for nonvascular plants.

Guideline Reference:

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2019-12-16 and 2020-11-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 161814, Metolachlor	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337670

Pollutant:

Metolachlor

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:

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

The USEPA Water Quality Advisory for Metolachlor is 0.044 mg/L. (USEPA Water Quality Advisory, March 1986, p. 15)

Guideline Reference:

Water Quality Health Advisory document for Metolachlor

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2019-12-16 and 2020-11-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633


DECISION ID	161815	Region 6
East Walker River, below Bridgeport Reservoir

Pollutant:	Metribuzin
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 161815, Metribuzin	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337673

Pollutant:

Metribuzin

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:

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

The USEPA Health Advisory for lifetime exposure to Metribuzin as a drinking water level is a concentration of 0.07 mg/L.

Guideline Reference:

2012 Edition of the Drinking Water Standards and Health Advisories

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2019-12-16 and 2020-11-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633

Line of Evidence (LOE) for Decision ID 161815, Metribuzin	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337672

Pollutant:

Metribuzin

LOE Subgroup:

Pollutant-Water

Matrix:

Water

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:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

The evaluation guideline for metribuzin is the USEPA Aquatic Life Benchmark of 8.1 ug/L for a nonvascular plant (acute).

Guideline Reference:

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2019-12-16 and 2020-11-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):


DECISION ID	102644	Region 6
East Walker River, below Bridgeport Reservoir

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

Regional Board Conclusion:	This pollutant is being considered for placement on the CWA section 303(d) List under section 3.1 of the Listing Policy. 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 that are all based on the same single tissue sample analyzed for different forms of microcystin. Zero of one samples exceed the guideline for all four of the forms of microcystin analyzed. 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 samples exceed the guideline for all four of the forms of microcystin 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. The readily available data and information is insufficient to determine, with the power and confidence of the Listing Policy, the applicable beneficial use support rating.

State Board Review of Regional Board Conclusion and Recommendation:

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

Line of Evidence (LOE) for Decision ID 102644, Microcystins	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

99251

Pollutant:

Microcystins

LOE Subgroup:

Pollutant-Tissue

Matrix:

Tissue

Fraction:

Fish fillet

Beneficial Use:

Commercial or recreational collection of fish, shellfish, or organisms

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed SWAMP Sportfish Rivers and Streams data for East Walker River, below Bridgeport Reservoir to determine beneficial use support and the results are as follows 0 of the 1 samples exceeded the water quality standard for Microcystins. Data were collected for 1 fish species (1 composite(s) of Sacramento Blackfish each composed of 5 fish per composite).

Data Reference:

Water Quality Assessment Data for the 2018 solicitation cycle submitted through CEDEN for SWAMP Sportfish Rivers and Streams.

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

The 10 ng/g wet weight action level for microcystins for edible sport fish and shellfish containing microcystins identifies the maximum concentration of cyanotoxins that a typical consumer (one meal per week) could ingest without exceeding the reference dose, and is equal to the sum of the Microcystin congeners LA, LR, RR, and LY.(OEHHA 2012)

Guideline Reference:

Toxicological Summary and Suggested Action Levels to Reduce Potential Adverse Health Effects of Six Cyanotoxins

Spatial Representation:

Data was collected from 1 station(s) with the station code(s): 630EWK002.

Temporal Representation:

Data for this line of evidence were collected between 2011-08-29 and 2011-08-29

Environmental Conditions:

QAPP Information:

Quality Assurance Program Plan and Standard Operating Procedures for SWAMP program

QAPP Information Reference(s):

Quality Assurance Program Plans, Quality Assurance Project Plans, and Standard Operating Procedures for the SWAMP program

Line of Evidence (LOE) for Decision ID 102644, Microcystins	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

99244

Pollutant:

Microcystin-YR

LOE Subgroup:

Pollutant-Tissue

Matrix:

Tissue

Fraction:

Fish fillet

Beneficial Use:

Commercial or recreational collection of fish, shellfish, or organisms

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed SWAMP Sportfish Rivers and Streams data for East Walker River, below Bridgeport Reservoir to determine beneficial use support and the results are as follows 0 of the 1 samples exceeded the water quality standard for Microcystin-YR. Data were collected for 1 fish species (1 composite(s) of Sacramento Blackfish each composed of 5 fish per composite).

Data Reference:

Water Quality Assessment Data for the 2018 solicitation cycle submitted through CEDEN for SWAMP Sportfish Rivers and Streams.

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

The 10 ng/g wet weight action level for microcystins for edible sport fish and shellfish containing Microcystin-YR identifies the maximum concentration of cyanotoxins that a typical consumer (one meal per week) could ingest without exceeding the reference dose.(OEHHA 2012)

Guideline Reference:

Toxicological Summary and Suggested Action Levels to Reduce Potential Adverse Health Effects of Six Cyanotoxins

Spatial Representation:

Data was collected from 1 station(s) with the station code(s): 630EWK002.

Temporal Representation:

Data for this line of evidence were collected between 2011-08-29 and 2011-08-29

Environmental Conditions:

QAPP Information:

Quality Assurance Program Plan and Standard Operating Procedures for SWAMP program

QAPP Information Reference(s):

Quality Assurance Program Plans, Quality Assurance Project Plans, and Standard Operating Procedures for the SWAMP program

Line of Evidence (LOE) for Decision ID 102644, Microcystins	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

99489

Pollutant:

Microcystin-RR

LOE Subgroup:

Pollutant-Tissue

Matrix:

Tissue

Fraction:

Fish fillet

Beneficial Use:

Commercial or recreational collection of fish, shellfish, or organisms

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed SWAMP Sportfish Rivers and Streams data for East Walker River, below Bridgeport Reservoir to determine beneficial use support and the results are as follows 0 of the 1 samples exceeded the water quality standard for Microcystin-RR. Data were collected for 1 fish species (1 composite(s) of Sacramento Blackfish each composed of 5 fish per composite).

Data Reference:

Water Quality Assessment Data for the 2018 solicitation cycle submitted through CEDEN for SWAMP Sportfish Rivers and Streams.

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

The 10 ng/g wet weight action level for microcystins for edible sport fish and shellfish containing Microcystin-RR identifies the maximum concentration of cyanotoxins that a typical consumer (one meal per week) could ingest without exceeding the reference dose.(OEHHA 2012)

Guideline Reference:

Toxicological Summary and Suggested Action Levels to Reduce Potential Adverse Health Effects of Six Cyanotoxins

Spatial Representation:

Data was collected from 1 station(s) with the station code(s): 630EWK002.

Temporal Representation:

Data for this line of evidence were collected between 2011-08-29 and 2011-08-29

Environmental Conditions:

QAPP Information:

Quality Assurance Program Plan and Standard Operating Procedures for SWAMP program

QAPP Information Reference(s):

Quality Assurance Program Plans, Quality Assurance Project Plans, and Standard Operating Procedures for the SWAMP program

Line of Evidence (LOE) for Decision ID 102644, Microcystins	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

99483

Pollutant:

Microcystin-LR

LOE Subgroup:

Pollutant-Tissue

Matrix:

Tissue

Fraction:

Fish fillet

Beneficial Use:

Commercial or recreational collection of fish, shellfish, or organisms

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed SWAMP Sportfish Rivers and Streams data for East Walker River, below Bridgeport Reservoir to determine beneficial use support and the results are as follows 0 of the 1 samples exceeded the water quality standard for Microcystin-LR. Data were collected for 1 fish species (1 composite(s) of Sacramento Blackfish each composed of 5 fish per composite).

Data Reference:

Water Quality Assessment Data for the 2018 solicitation cycle submitted through CEDEN for SWAMP Sportfish Rivers and Streams.

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

The 10 ng/g wet weight action level for microcystins for edible sport fish and shellfish containing Microcystin-LR identifies the maximum concentration of cyanotoxins that a typical consumer (one meal per week) could ingest without exceeding the reference dose.(OEHHA 2012)

Guideline Reference:

Toxicological Summary and Suggested Action Levels to Reduce Potential Adverse Health Effects of Six Cyanotoxins

Spatial Representation:

Data was collected from 1 station(s) with the station code(s): 630EWK002.

Temporal Representation:

Data for this line of evidence were collected between 2011-08-29 and 2011-08-29

Environmental Conditions:

QAPP Information:

Quality Assurance Program Plan and Standard Operating Procedures for SWAMP program

QAPP Information Reference(s):

Quality Assurance Program Plans, Quality Assurance Project Plans, and Standard Operating Procedures for the SWAMP program

Line of Evidence (LOE) for Decision ID 102644, Microcystins	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

99477

Pollutant:

Microcystin-LA

LOE Subgroup:

Pollutant-Tissue

Matrix:

Tissue

Fraction:

Fish fillet

Beneficial Use:

Commercial or recreational collection of fish, shellfish, or organisms

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed SWAMP Sportfish Rivers and Streams data for East Walker River, below Bridgeport Reservoir to determine beneficial use support and the results are as follows 0 of the 1 samples exceeded the water quality standard for Microcystin-LA. Data were collected for 1 fish species (1 composite(s) of Sacramento Blackfish each composed of 5 fish per composite).

Data Reference:

Water Quality Assessment Data for the 2018 solicitation cycle submitted through CEDEN for SWAMP Sportfish Rivers and Streams.

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

The 10 ng/g wet weight action level for microcystins for edible sport fish and shellfish containing Microcystin-LA identifies the maximum concentration of cyanotoxins that a typical consumer (one meal per week) could ingest without exceeding the reference dose.(OEHHA 2012)

Guideline Reference:

Toxicological Summary and Suggested Action Levels to Reduce Potential Adverse Health Effects of Six Cyanotoxins

Spatial Representation:

Data was collected from 1 station(s) with the station code(s): 630EWK002.

Temporal Representation:

Data for this line of evidence were collected between 2011-08-29 and 2011-08-29

Environmental Conditions:

QAPP Information:

Quality Assurance Program Plan and Standard Operating Procedures for SWAMP program

QAPP Information Reference(s):

Quality Assurance Program Plans, Quality Assurance Project Plans, and Standard Operating Procedures for the SWAMP program


DECISION ID	103815	Region 6
East Walker River, below Bridgeport Reservoir

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

Regional Board Conclusion:	This pollutant is being considered for placement on the CWA section 303(d) List under section 3.1 of the Listing Policy. 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 that consists of a single tissue sample however it could not be assessed due to quantitation issues. Zero of zero samples exceed the guideline for mirex. 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 zero samples exceeded the guideline 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. The readily available data and information is insufficient to determine, with the power and confidence of the Listing Policy, the applicable beneficial use support rating.

State Board Review of Regional Board Conclusion and Recommendation:

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

Line of Evidence (LOE) for Decision ID 103815, Mirex	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

99269

Pollutant:

Mirex

LOE Subgroup:

Pollutant-Tissue

Matrix:

Tissue

Fraction:

Fish fillet

Beneficial Use:

Commercial or recreational collection of fish, shellfish, or organisms

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Waterboard staff assessed SWAMP Sportfish Rivers and Streams data for East Walker River, below Bridgeport Reservoir to determine beneficial use support and the results are as follows: Zero of Zero samples exceeded the water quality standard for Mirex. Although data was collected for 1 fish species (1 composite(s) of Sacramento Blackfish each composed of 5 fish per composite), all 1 sample(s) had to be thrown out due to quantitation issues.

Data Reference:

Water Quality Assessment Data for the 2018 solicitation cycle submitted through CEDEN for SWAMP Sportfish Rivers and Streams.

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

The modified OEHHA Fish Contaminant Goal for mirex in fish tissue is 0.28 ppb. This screening level assumes an average body weight of 70 kg and a consumption rate of 32 g/day. This constituent is a carcinogen therefore the risk level is set to one in a million. A cooking reduction factor of 1 is applied for skin-off fillets. (Klasing, S., and R. Brodberg, 2008; OEHHA, 1992)

Guideline Reference:

Development of Fish Contaminant Goals and Advisory Tissue Levels for Common Contaminants in California Sport Fish: Chlordane, DDTs, Dieldrin, Methylmercury, PCBs, Selenium, and Toxaphene

Guideline Reference:

Expedited Cancer Potency Values and Proposed Regulatory Levels for Certain Proposition 65 Carcinogens.

Spatial Representation:

Data was collected from 1 station(s) with the station code(s): 630EWK002.

Temporal Representation:

Data for this line of evidence were collected between 2011-08-29 and 2011-08-29

Environmental Conditions:

QAPP Information:

Quality Assurance Program Plan and Standard Operating Procedures for SWAMP program

QAPP Information Reference(s):

Quality Assurance Program Plans, Quality Assurance Project Plans, and Standard Operating Procedures for the SWAMP program


DECISION ID	161785	Region 6
East Walker River, below Bridgeport Reservoir

Pollutant:	Molinate
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 161785, Molinate	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337674

Pollutant:

Molinate

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:

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The California Maximum Contaminant Level for Molinate incorporated by reference in the Water Quality Control Plan, Lahontan Region is 20 ug/L (Water Quality Control Plan, Lahontan Region).

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2019-12-16 and 2020-11-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633

Line of Evidence (LOE) for Decision ID 161785, Molinate	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337675

Pollutant:

Molinate

LOE Subgroup:

Pollutant-Water

Matrix:

Water

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:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

The evaluation guideline for molinate is the USEPA Aquatic Life Benchmark of 105 ug/L for a fish (acute).

Guideline Reference:

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2019-12-16 and 2020-11-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):


DECISION ID	161786	Region 6
East Walker River, below Bridgeport Reservoir

Pollutant:	Molybdenum
Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)(2018)
Revision Status	Revised
Impairment from Pollutant or Pollution:	Pollutant

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

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

State Board Review of Regional Board Conclusion and Recommendation:

State Board Decision Recommendation:	After review of 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 161786, Molybdenum	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337683

Pollutant:

Molybdenum

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

EPA Drinking Water Lifetime Health advisory level for Molybdenum is 0.04 mg/L.

Guideline Reference:

2012 Edition of the Drinking Water Standards and Health Advisories

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2020-12-02 and 2022-06-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633

Line of Evidence (LOE) for Decision ID 161786, Molybdenum	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337681

Pollutant:

Molybdenum

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Agricultural Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Waters designated as AGR shall not contain concentrations of chemical constituents in amounts that adversely affect the water for beneficial uses (Water Quality Control Plan, Lahontan Region).

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Water Quality for Agriculture, published by the Food and Agriculture Organization of the United Nations in 1985, contains criteria protective of various agricultural uses of water. These criteria were used to translate narrative water quality objectives for chemical constituents that prohibit chemicals in concentrations that would impair agricultural uses of water. The recommended maximum concentration of molybdenum in irrigation water is 0.01 mg/L.

Guideline Reference:

Water Quality for Agriculture, Food and Agriculture Organization of the United Nations - Irrigation and Drainage Paper No. 29, Rev 1, Rome (1985)

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2020-12-02 and 2022-06-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633

Line of Evidence (LOE) for Decision ID 161786, Molybdenum	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

7707

Pollutant:

Molybdenum

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

Fixed station physical/chemical (conventional plus toxic pollutants)

Data Used to Assess Water Quality:

The U.S. Geological Survey sampled the East Walker River under the Region 6 SWAMP program in 2001 and 2002. Total recoverable molybdenum concentrations in four samples ranged from 4.4 to 4.9 ug/L.

Data Reference:

2007. SWAMP Data for the West Walker River and East Walker River Hydrologic Units

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

There are no applicable state or federal standards or criteria for molybdenum for protection of the Municipal and Domestic Supply use.

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

One station, East Walker River at the California-Nevada State Line, was sampled.

Temporal Representation:

Four quarterly samples were collected in 2001 and 2002.

Environmental Conditions:

QAPP Information:

Data meet the quality assurance requirements of the SWAMP QAPP.

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 161786, Molybdenum	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

7709

Pollutant:

Molybdenum

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

Fixed station physical/chemical (conventional plus toxic pollutants)

Data Used to Assess Water Quality:

The U.S. Geological Survey sampled the East Walker River under the Region 6 SWAMP program in 2001 and 2002. Concentrations of dissolved molybdenum in four samples ranged from 4.3 to 4.8 ug/L.

Data Reference:

2007. SWAMP Data for the West Walker River and East Walker River Hydrologic Units

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

There are no state or federal standards or criteria for cobalt for the protection of freshwater aquatic life.

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

One station, East Walker River at the California-Nevada State Line, was sampled.

Temporal Representation:

Four quarterly samples were collected in 2001 and 2002.

Environmental Conditions:

QAPP Information:

Data meet the quality assurance requirements of the SWAMP QAPP.

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 161786, Molybdenum	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337676

Pollutant:

Molybdenum

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:

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

EPA Drinking Water Lifetime Health advisory level for Molybdenum is 0.04 mg/L.

Guideline Reference:

2012 Edition of the Drinking Water Standards and Health Advisories

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2018-04-04 and 2022-06-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633

Line of Evidence (LOE) for Decision ID 161786, Molybdenum	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337677

Pollutant:

Molybdenum

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Agricultural Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Waters designated as AGR shall not contain concentrations of chemical constituents in amounts that adversely affect the water for beneficial uses (Water Quality Control Plan, Lahontan Region).

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Water Quality for Agriculture, published by the Food and Agriculture Organization of the United Nations in 1985, contains criteria protective of various agricultural uses of water. These criteria were used to translate narrative water quality objectives for chemical constituents that prohibit chemicals in concentrations that would impair agricultural uses of water. The recommended maximum concentration of molybdenum in irrigation water is 0.01 mg/L.

Guideline Reference:

Water Quality for Agriculture, Food and Agriculture Organization of the United Nations - Irrigation and Drainage Paper No. 29, Rev 1, Rome (1985)

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2018-04-04 and 2022-06-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633


DECISION ID	161787	Region 6
East Walker River, below Bridgeport Reservoir

Pollutant:	Naphthalene
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:

Line of Evidence (LOE) for Decision ID 161787, Naphthalene	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337689

Pollutant:

Naphthalene

LOE Subgroup:

Pollutant-Water

Matrix:

Water

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:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

The USEPA recommended naphthalene criterion for the protection of freshwater aquatic life is 620 ug/l. (EPA 440/5-80-059)

Guideline Reference:

Ambient Water Quality Criteria for Naphthalene

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2020-11-30 and 2020-11-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633

Line of Evidence (LOE) for Decision ID 161787, Naphthalene	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337688

Pollutant:

Naphthalene

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:

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Drinking Water Notification and Response Levels: An Overview

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2020-11-30 and 2020-11-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633


DECISION ID	161788	Region 6
East Walker River, below Bridgeport Reservoir

Pollutant:	Nickel
Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)(2018)
Revision Status	Revised
Impairment from Pollutant or Pollution:	Pollutant

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

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

State Board Review of Regional Board Conclusion and Recommendation:

State Board Decision Recommendation:	After review of 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 161788, Nickel	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337692

Pollutant:

Nickel

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The Water Quality Control Plan for the Lahontan Region?s Objective for Municipal and Domestic Supply uses of inland surface waters states that waters designated as MUN shall not contain concentrations of chemical constituents in excess of the maximum contaminant level (MCL) or secondary maximum contaminant level (SMCL). This is based upon drinking water standards specified in the following provisions of Title 22 of the California Code of Regulations which are incorporated by reference into the Water Quality Control Plan: Table 64431-A of Section 64431 (Inorganic Chemicals), Table 64431-B of Section 64431 (Fluoride), Table 64444-A of Section 64444 (Organic Chemicals), Table 64449-A of Section 64449 (Secondary Maximum Contaminant Levels-Ranges). The maximum contaminant level listed in Table 64431-A for nickel is 0.1 mg/L.

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2018-04-04 and 2022-06-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633

Line of Evidence (LOE) for Decision ID 161788, Nickel	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

341559

Pollutant:

Nickel

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Commercial or recreational collection of fish, shellfish, or organisms

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The nickel criterion for the protection of human health from consumption of organisms only is 4.6 mg/L (California Toxics Rule, 2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2014-05-12 and 2014-07-24

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633

Line of Evidence (LOE) for Decision ID 161788, Nickel	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337690

Pollutant:

Nickel

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Commercial or recreational collection of fish, shellfish, or organisms

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The nickel criterion for the protection of human health from consumption of organisms only is 4.6 mg/L (California Toxics Rule, 2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2018-04-04 and 2022-06-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633

Line of Evidence (LOE) for Decision ID 161788, Nickel	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

341541

Pollutant:

Nickel

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:

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2014-05-12 and 2014-07-24

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633

Line of Evidence (LOE) for Decision ID 161788, Nickel	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337698

Pollutant:

Nickel

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Commercial or recreational collection of fish, shellfish, or organisms

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The nickel criterion for the protection of human health from consumption of organisms only is 4.6 mg/L (California Toxics Rule, 2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2018-04-04 and 2022-06-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633

Line of Evidence (LOE) for Decision ID 161788, Nickel	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337695

Pollutant:

Nickel

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The dissolved nickel criterion continuous concentration (expressed as a 4-day average) to protect aquatic life in freshwater is hardness dependent. The criterion when calculated using a default hardness of 100 mg/L is 52 ug/L (California Toxics Rule, 2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2018-04-04 and 2022-06-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633

Line of Evidence (LOE) for Decision ID 161788, Nickel	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

341563

Pollutant:

Nickel

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2014-05-12 and 2014-07-24

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633

Line of Evidence (LOE) for Decision ID 161788, Nickel	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

341557

Pollutant:

Nickel

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2014-05-12 and 2014-07-24

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633

Line of Evidence (LOE) for Decision ID 161788, Nickel	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337702

Pollutant:

Nickel

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:

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2018-04-04 and 2022-06-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633

Line of Evidence (LOE) for Decision ID 161788, Nickel	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

341561

Pollutant:

Nickel

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Commercial or recreational collection of fish, shellfish, or organisms

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The nickel criterion for the protection of human health from consumption of organisms only is 4.6 mg/L (California Toxics Rule, 2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2014-05-12 and 2014-07-24

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633

Line of Evidence (LOE) for Decision ID 161788, Nickel	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

5089

Pollutant:

Nickel

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

Fixed station physical/chemical (conventional plus toxic pollutants)

Data Used to Assess Water Quality:

The U.S. Geological survey sampled nickel under the Region 6 SWAMP program in 2001 and 2002. Dissolved nickel concentrations in 4 samples ranged from less than 0.06 ug/L to 0.28 ug/L. The CTR standards were not exceeded.

Data Reference:

2007. SWAMP Data for the West Walker River and East Walker River Hydrologic Units

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

The California Toxics Rule (CTR) freshwater aquatic life standards for nickel are dependent on hardness. At the hardness levels reported for this station, the acute (1-hour average) standard ranges from 234.01 to 336.75 ug/L. The chronic (4-day average) standard ranges from 32.69 to 37.44 ug/L.

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

One station, East Walker River at the California-Nevada State Line, was sampled.

Temporal Representation:

Four quarterly samples were collected in 2001 and 2002.

Environmental Conditions:

QAPP Information:

Data meet the quality assurance requirements of the SWAMP QAPP.

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 161788, Nickel	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

5119

Pollutant:

Nickel

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

Fixed station physical/chemical (conventional plus toxic pollutants)

Data Used to Assess Water Quality:

Data Reference:

2007. SWAMP Data for the West Walker River and East Walker River Hydrologic Units

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

California Maximum Contaminant Levels (MCLs) apply to ambient waters under the Lahontan Basin Plan's "Chemical Constituents" objective. The MCL for nickel is 100 ug/L.

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

One station, East Walker River at the California-Nevada State Line, was sampled.

Temporal Representation:

Four quarterly samples were collected in 2001 and 2002.

Environmental Conditions:

QAPP Information:

Data meet the quality assurance requirements of the SWAMP QAPP.

QAPP Information Reference(s):


DECISION ID	73024	Region 6
East Walker River, below Bridgeport Reservoir

Pollutant:	Nitrate/Nitrite (Nitrite + Nitrate as N)
Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)(2016)
Revision Status	Revised
Impairment from Pollutant or Pollution:	Pollutant

Regional Board Conclusion:	This pollutant is being considered for placement on the CWA section 303(d) List under section 3.1 of the Listing Policy. Under section 3.1 a single line of evidence is necessary to assess listing status. Six lines of evidence are available in the administrative record to assess this pollutant. Zero of 48 samples exceed the guideline for nitrate/nitrite as N. 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 48 samples exceeded the guideline and this does not exceed the allowable frequency listed in Table 3.1 of the Listing Policy. 4. Pursuant to section 3.11 of the Listing Policy, no additional data and information are available indicating that standards are not met.

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

State Board Review of Regional Board Conclusion and Recommendation:

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

Line of Evidence (LOE) for Decision ID 73024, Nitrate/Nitrite (Nitrite + Nitrate as N)	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

99048

Pollutant:

Nitrate/Nitrite (Nitrite + Nitrate as N)

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:

Data Reference:

Water quality data for federal, state, and tribal agencies submitted through the US EPA STorage and RETrival (STORET) database for the 2018 listing cycle.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The California Maximum Contaminant Level for nitrate + nitrite (as N) that is incorporated by reference in the Water Quality Control Plan, Lahontan Region is 10.0 mg/L (Water Quality Control Plan, Lahontan Region).

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site(s) (21NEV1_WQX-NV09-301-EF-001)

Temporal Representation:

The samples were collected between the dates of 2011-03-09 and 2012-08-07

Environmental Conditions:

QAPP Information:

QAPP not required for federal data

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 73024, Nitrate/Nitrite (Nitrite + Nitrate as N)	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

97080

Pollutant:

Nitrate/Nitrite (Nitrite + Nitrate as N)

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Not Recorded

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed SWAMP RWB6 Monitoring data for East Walker River, below Bridgeport Reservoir to determine beneficial use support and results are as follows: 0 of 7 samples exceeded the water quality standard for Nitrate + Nitrite as N.

Data Reference:

Water Quality Assessment Data for the 2018 solicitation cycle submitted through CEDEN for the SWAMP RWB6 Monitoring (tissue and water).

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site(s) (630EWK001)

Temporal Representation:

The samples were collected between the dates of 2011-01-06 and 2011-08-01

Environmental Conditions:

QAPP Information:

Quality Assurance Program Plan and Standard Operating Procedures for SWAMP program

QAPP Information Reference(s):

Quality Assurance Program Plans, Quality Assurance Project Plans, and Standard Operating Procedures for the SWAMP program

Line of Evidence (LOE) for Decision ID 73024, Nitrate/Nitrite (Nitrite + Nitrate as N)	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

44326

Pollutant:

Nitrate/Nitrite (Nitrite + Nitrate as N)

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

None

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed SWAMP data for East Walker River, below Bridgeport Reservoir to determine beneficial use support and results are as follows: 0 of 2 samples exceed the criterion for Nitrate/Nitrite as N.

Data Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

Data for this line of evidence for East Walker River, below Bridgeport Reservoir was collected at 1 monitoring site [ East Walker River, at CA/NV state line]

Temporal Representation:

Data was collected over the time period 8/14/2007-11/8/2007.

Environmental Conditions:

Staff is not aware of any special conditions that might affect interpretation of the data.

QAPP Information:

2002 QAMP (Quality Assurance Management Plan) for the State of California's Surface Water Ambient Monitoring Program

QAPP Information Reference(s):

Quality Assurance Management Plan for the State of California's Surface Water Ambient Monitoring Program. Sacramento, CA. State Water Resources Control Board. SWAMP. December 2002 (1st version)

Line of Evidence (LOE) for Decision ID 73024, Nitrate/Nitrite (Nitrite + Nitrate as N)	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

5034

Pollutant:

Nitrate/Nitrite (Nitrite + Nitrate as N)

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

Fixed station physical/chemical (conventional plus toxic pollutants)

Data Used to Assess Water Quality:

The U.S. Geological Survey sampled this station under the Region 6 SWAMP program between 2001 and 2005. Concentrations of nitrite plus nitrate in 16 quarterly samples ranged from below detection level to 0.42 mg/L. One sample was an estimated value. The MCL was not exceeded.

Data Reference:

2007. SWAMP Data for the West Walker River and East Walker River Hydrologic Units

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

California Maximum Contaminant Levels (MCLs) apply to ambient waters under the Lahontan Basin Plan's "Chemical Constituents" objective. The MCL for nitrite plus nitrate is 10 mg/L expressed "as nitrogen."

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

One station, East Walker River at the California-Nevada State Line, was sampled.

Temporal Representation:

Sixteen quarterly samples were collected between 2001 and 2005.

Environmental Conditions:

QAPP Information:

Data meet the quality assurance requirements of the SWAMP QAPP.

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 73024, Nitrate/Nitrite (Nitrite + Nitrate as N)	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

98545

Pollutant:

Nitrate/Nitrite (Nitrite + Nitrate as N)

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed SWAMP RWB6 Monitoring data for East Walker River, below Bridgeport Reservoir to determine beneficial use support and results are as follows: 0 of 3 samples exceeded the water quality standard for Nitrate + Nitrite as N.

Data Reference:

Water Quality Assessment Data for the 2018 solicitation cycle submitted through CEDEN for the SWAMP RWB6 Monitoring (tissue and water).

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site(s) (630EWK001)

Temporal Representation:

The samples were collected between the dates of 2010-09-13 and 2010-11-01

Environmental Conditions:

QAPP Information:

Quality Assurance Program Plan and Standard Operating Procedures for SWAMP program

QAPP Information Reference(s):

Quality Assurance Program Plans, Quality Assurance Project Plans, and Standard Operating Procedures for the SWAMP program

Line of Evidence (LOE) for Decision ID 73024, Nitrate/Nitrite (Nitrite + Nitrate as N)	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

97250

Pollutant:

Nitrate/Nitrite (Nitrite + Nitrate as N)

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed SWAMP RWB6 Monitoring data for East Walker River, below Bridgeport Reservoir to determine beneficial use support and results are as follows: 0 of 16 samples exceeded the water quality standard for Nitrate + Nitrite as N.

Data Reference:

Water Quality Assessment Data for the 2018 solicitation cycle submitted through CEDEN for the SWAMP RWB6 Monitoring (tissue and water).

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site(s) (630EWK001)

Temporal Representation:

The samples were collected between the dates of 2012-04-05 and 2015-10-15

Environmental Conditions:

QAPP Information:

Quality Assurance Program Plan and Standard Operating Procedures for SWAMP program

QAPP Information Reference(s):

Quality Assurance Program Plans, Quality Assurance Project Plans, and Standard Operating Procedures for the SWAMP program


DECISION ID	75810	Region 6
East Walker River, below Bridgeport Reservoir

Pollutant:	Nitrogen, Nitrite
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	Revised
Impairment from Pollutant or Pollution:	Pollutant

Regional Board Conclusion:	This pollutant is being considered for placement on the CWA section 303(d) List under section 3.1 of the Listing Policy. Under section 3.1 a single line of evidence is necessary to assess listing status. Four lines of evidence are available in the administrative record to assess this pollutant. Zero of the six samples exceed the guideline for nitrite. 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 six samples exceeded the guideline 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. The readily available data and information is insufficient to determine, with the power and confidence of the Listing Policy, the applicable beneficial use support rating.

State Board Review of Regional Board Conclusion and Recommendation:

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

Line of Evidence (LOE) for Decision ID 75810, Nitrogen, Nitrite	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

99051

Pollutant:

Nitrogen, Nitrite

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed STORET data for East Walker River, below Bridgeport Reservoir to determine beneficial use support and results are as follows: 0 of 2 samples exceeded the water quality standard for Nitrite as N.

Data Reference:

Water quality data for federal, state, and tribal agencies submitted through the US EPA STorage and RETrival (STORET) database for the 2018 listing cycle.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The Water Quality Control Plan, Lahontan Basin, Objective for Municipal and Domestic Supply uses of inland surface waters states the following: waters shall not contain concentrations of inorganic chemicals in excess of the limits specified in California Code of Regulations, Title 22, Table 64431-A of section 64431 (Inorganic Chemicals). The maximum contaminant level listed in Table 64431-A for Nitrite as N is 1.0 mg/L.

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site(s) (21NEV1_WQX-NV09-301-EF-001)

Temporal Representation:

The samples were collected between the dates of 2011-12-08 and 2012-08-07

Environmental Conditions:

QAPP Information:

QAPP not required for federal data

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 75810, Nitrogen, Nitrite	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

97141

Pollutant:

Nitrogen, Nitrite

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed SWAMP RWB6 Monitoring data for East Walker River, below Bridgeport Reservoir to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality standard for Nitrite as N.

Data Reference:

Water Quality Assessment Data for the 2018 solicitation cycle submitted through CEDEN for the SWAMP RWB6 Monitoring (tissue and water).

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site(s) (630EWK001)

Temporal Representation:

The samples were collected between the dates of 2010-09-13 and 2010-09-13

Environmental Conditions:

QAPP Information:

Quality Assurance Program Plan and Standard Operating Procedures for SWAMP program

QAPP Information Reference(s):

Quality Assurance Program Plans, Quality Assurance Project Plans, and Standard Operating Procedures for the SWAMP program

Line of Evidence (LOE) for Decision ID 75810, Nitrogen, Nitrite	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

7747

Pollutant:

Nitrite as Nitrite NO2

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

Fixed station physical/chemical (conventional plus toxic pollutants)

Data Used to Assess Water Quality:

The U.S. Geological Survey collected one NO2-N sample under the Region 6 SWAMP program on 6/28/2002. The nitrite concentration was 0.011 mg/L. The MCL was not violated.

Data Reference:

2007. SWAMP Data for the West Walker River and East Walker River Hydrologic Units

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

California Maximum Contaminant Levels (MCLs) apply to ambient waters under the Lahontan Basin Plan's "Chemical Constituents" objective. The MCL for nitrite is 1 mg/L.

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

One station, East Walker River at the California-Nevada State Line, was sampled.

Temporal Representation:

One sample was collected on 6/28/2002.

Environmental Conditions:

QAPP Information:

Data meet the quality assurance requirements of the SWAMP QAPP.

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 75810, Nitrogen, Nitrite	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

44346

Pollutant:

Nitrite as Nitrite NO2

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

None

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

Data for this line of evidence for East Walker River, below Bridgeport Reservoir was collected at 1 monitoring site [ East Walker River, at CA/NV state line]

Temporal Representation:

Data was collected over the time period 8/14/2007-11/8/2007.

Environmental Conditions:

Staff is not aware of any special conditions that might affect interpretation of the data.

QAPP Information:

2002 QAMP (Quality Assurance Management Plan) for the State of California's Surface Water Ambient Monitoring Program

QAPP Information Reference(s):

Quality Assurance Management Plan for the State of California's Surface Water Ambient Monitoring Program. Sacramento, CA. State Water Resources Control Board. SWAMP. December 2002 (1st version)


DECISION ID	161790	Region 6
East Walker River, below Bridgeport Reservoir

Pollutant:	Oxamyl (Vydate)
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 161790, Oxamyl (Vydate)	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337705

Pollutant:

Oxamyl (Vydate)

LOE Subgroup:

Pollutant-Water

Matrix:

Water

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:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

The evaluation guideline for oxamyl is the USEPA Aquatic Life Benchmark of 27 ug/L for an invertebrate (chronic).

Guideline Reference:

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2019-12-16 and 2020-11-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 161790, Oxamyl (Vydate)	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337706

Pollutant:

Oxamyl (Vydate)

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:

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The California Maximum Contaminant Level for Oxamyl incorporated by reference in the Water Quality Control Plan, Lahontan Region is 50 ug/L (Water Quality Control Plan, Lahontan Region).

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2019-12-16 and 2020-11-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633


DECISION ID	161824	Region 6
East Walker River, below Bridgeport Reservoir

Pollutant:	Paraquat
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:

Line of Evidence (LOE) for Decision ID 161824, Paraquat	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337708

Pollutant:

Paraquat

LOE Subgroup:

Pollutant-Water

Matrix:

Water

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 Nevada Division of Environmental Protection data for East Walker River, below Bridgeport Reservoir to determine beneficial use support, and the results are as follows: 0 of the 0 samples exceeded the evaluation guideline for Paraquat. Although a total of 2 samples were collected, 2 of these samples were not included in the assessment because the laboratory data reporting limit(s) was above the water quality threshold 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:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

The evaluation guideline for paraquat is the USEPA Aquatic Life Benchmark of 0.396 ug/L for a nonvascular plant (acute) for Paraquat dichloride.

Guideline Reference:

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2019-12-16 and 2020-11-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):


DECISION ID	161793	Region 6
East Walker River, below Bridgeport Reservoir

Pollutant:	Pentachlorophenol (PCP)
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 161793, Pentachlorophenol (PCP)	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337709

Pollutant:

Pentachlorophenol (PCP)

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:

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The pentachlorophenol criterion for the protection of human health from the consumption of water and organisms is 0.28 ug/L (California Toxics Rule, 2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2019-12-16 and 2020-11-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633

Line of Evidence (LOE) for Decision ID 161793, Pentachlorophenol (PCP)	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337711

Pollutant:

Pentachlorophenol (PCP)

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Commercial or recreational collection of fish, shellfish, or organisms

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The pentachlorophenol criterion for the protection of human health from consumption of organisms only is 8.2 ug/L (California Toxics Rule, 2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2019-12-16 and 2020-11-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633

Line of Evidence (LOE) for Decision ID 161793, Pentachlorophenol (PCP)	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337710

Pollutant:

Pentachlorophenol (PCP)

LOE Subgroup:

Pollutant-Water

Matrix:

Water

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:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The pentachlorophenol criterion continuous concentration (expressed as a 4-day average) to protect aquatic life in freshwater is pH dependent. The criterion using a default pH value of 7.8 (when pH data is not present) is 15 ug/L. (California Toxics Rule, 2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2019-12-16 and 2020-11-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633


DECISION ID	161816	Region 6
East Walker River, below Bridgeport Reservoir

Pollutant:	Propachlor
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 161816, Propachlor	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337719

Pollutant:

Propachlor

LOE Subgroup:

Pollutant-Water

Matrix:

Water

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:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

The evaluation guideline for propachlor is the USEPA Aquatic Life Benchmark of 13.5 ug/L for a nonvascular plant (acute).

Guideline Reference:

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2019-12-16 and 2020-11-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 161816, Propachlor	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337718

Pollutant:

Propachlor

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:

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

The USEPA Health Advisory for propachlor as a drinking water level with a one in a million cancer risk is 0.001 mg/L.

Guideline Reference:

2018 Edition of the Drinking Water Standards and Health Advisories

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2019-12-16 and 2020-11-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633


DECISION ID	161795	Region 6
East Walker River, below Bridgeport Reservoir

Pollutant:	Propoxur
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 161795, Propoxur	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337721

Pollutant:

Propoxur

LOE Subgroup:

Pollutant-Water

Matrix:

Water

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:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

The evaluation guideline for propoxur is the USEPA Aquatic Life Benchmark of 5.5 ug/L for invertebrates (acute).

Guideline Reference:

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2019-12-16 and 2020-11-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 161795, Propoxur	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337720

Pollutant:

Propoxur

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:

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

The USEPA Health Advisory for lifetime exposure to propoxur as a drinking water level is a concentration of 0.003 mg/L.

Guideline Reference:

2018 Edition of the Drinking Water Standards and Health Advisories

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2019-12-16 and 2020-11-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633


DECISION ID	161796	Region 6
East Walker River, below Bridgeport Reservoir

Pollutant:	Selenium
Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)(2018)
Revision Status	Revised
Impairment from Pollutant or Pollution:	Pollutant

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

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

State Board Review of Regional Board Conclusion and Recommendation:

State Board Decision Recommendation:	After review of 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 161796, Selenium	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337732

Pollutant:

Selenium

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed Nevada Division of Environmental Protection data for East Walker River, below Bridgeport Reservoir to determine beneficial use support and the results are as follows: 0 of the 2 samples exceeded the water quality threshold for Selenium. Although a total of 5 samples were collected, 3 of these samples were not included in the assessment because the laboratory data reporting limit(s) was above the water quality threshold 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:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The selenium criterion continuous concentration (expressed as a 4-day average) to protect aquatic life in freshwater is 0.005 mg/L (California Toxics Rule, 2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site (21NEV1_WQX-NV09-301-EF-001).

Temporal Representation:

The samples were collected between the dates of 2018-04-04 and 2022-06-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633

Line of Evidence (LOE) for Decision ID 161796, Selenium	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

5123

Pollutant:

Selenium

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

Fixed station physical/chemical (conventional plus toxic pollutants)

Data Used to Assess Water Quality:

The U.S. Geological Survey sampled selenium under the Region 6 SWAMP program in 2001 and 2002. Dissolved selenium concentrations in 3 of 4 samples were below the detection level. The concentration in the remaining sample was an estimated value. The CTR standards were not exceeded.

Data Reference:

2007. SWAMP Data for the West Walker River and East Walker River Hydrologic Units

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

The California Toxics Rule (CTR) standards for protection of freshwater aquatic life are as follows: 4 day average = 5.0 ug/L; 1-hour average = 20 ug/L.

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

One station, East Walker River at the California-Nevada State Line, was sampled.

Temporal Representation:

Four quarterly samples were collected in 2001 and 2002.

Environmental Conditions:

QAPP Information:

Data meet the quality assurance requirements of the SWAMP QAPP.

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 161796, Selenium	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

99285

Pollutant:

Selenium

LOE Subgroup:

Pollutant-Tissue

Matrix:

Tissue

Fraction:

Fish fillet

Beneficial Use:

Commercial or recreational collection of fish, shellfish, or organisms

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed SWAMP Sportfish Rivers and Streams data for East Walker River, below Bridgeport Reservoir to determine beneficial use support and the results are as follows 0 of the 1 samples exceeded the water quality standard for Selenium. Data were collected for 1 fish species (1 composite(s) of Sacramento Blackfish each composed of 5 fish per composite).

Data Reference:

Water Quality Assessment Data for the 2018 solicitation cycle submitted through CEDEN for SWAMP Sportfish Rivers and Streams.

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

The OEHHA Fish Contaminant Goal for selenium in fish tissue is 7.4 ppm. This screening level assumes an average body weight of 70 kg and a consumption rate of 32 g/day. A background dietary consumption rate of 0.114 mg/day is applied for this micronutrient. (Klasing, S., and R. Brodberg, 2008)

Guideline Reference:

Development of Fish Contaminant Goals and Advisory Tissue Levels for Common Contaminants in California Sport Fish: Chlordane, DDTs, Dieldrin, Methylmercury, PCBs, Selenium, and Toxaphene

Spatial Representation:

Data was collected from 1 station(s) with the station code(s): 630EWK002.

Temporal Representation:

Data for this line of evidence were collected between 2011-08-29 and 2011-08-29

Environmental Conditions:

QAPP Information:

Quality Assurance Program Plan and Standard Operating Procedures for SWAMP program

QAPP Information Reference(s):

Quality Assurance Program Plans, Quality Assurance Project Plans, and Standard Operating Procedures for the SWAMP program

Line of Evidence (LOE) for Decision ID 161796, Selenium	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

7713

Pollutant:

Selenium

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

Fixed station physical/chemical (conventional plus toxic pollutants)

Data Used to Assess Water Quality:

The U.S. Geological survey sampled selenium under the Region 6 SWAMP program in 2001 and 2002. Concentrations of total selenium in 3 of 4 samples were estimated values, and the fourth sample was below the detection level. The MCL was not exceeded.

Data Reference:

2007. SWAMP Data for the West Walker River and East Walker River Hydrologic Units

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

California Maximum Contaminant Levels (MCLs) apply to ambient waters under the Lahontan Basin Plan's "Chemical Constituents" objective. The MCL for selenium is 50 ug/L.

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

One station, East Walker River at the California-Nevada State Line, was sampled.

Temporal Representation:

Four quarterly samples were collected in 2001 and 2002.

Environmental Conditions:

QAPP Information:

Data meet the quality assurance requirements of the SWAMP QAPP.

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 161796, Selenium	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337722

Pollutant:

Selenium

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:

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The California Maximum Contaminant Level for selenium incorporated by reference in the Water Quality Control Plan, Lahontan Region is 0.05 mg/L.

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2018-04-04 and 2022-06-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633

Line of Evidence (LOE) for Decision ID 161796, Selenium	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337727

Pollutant:

Selenium

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The California Maximum Contaminant Level for selenium incorporated by reference in the Water Quality Control Plan, Lahontan Region is 0.05 mg/L.

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2018-04-04 and 2022-06-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633

Line of Evidence (LOE) for Decision ID 161796, Selenium	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337726

Pollutant:

Selenium

LOE Subgroup:

Pollutant-Water

Matrix:

Water

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 Nevada Division of Environmental Protection data for East Walker River, below Bridgeport Reservoir to determine beneficial use support and the results are as follows: 0 of the 2 samples exceeded the water quality threshold for Selenium. Although a total of 5 samples were collected, 3 of these samples were not included in the assessment because the laboratory data reporting limit(s) was above the water quality threshold 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:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The selenium criterion continuous concentration (expressed as a 4-day average) to protect aquatic life in freshwater is 0.005 mg/L (California Toxics Rule, 2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site (21NEV1_WQX-NV09-301-EF-001).

Temporal Representation:

The samples were collected between the dates of 2018-04-04 and 2022-06-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633


DECISION ID	161797	Region 6
East Walker River, below Bridgeport Reservoir

Pollutant:	Silver
Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)(2018)
Revision Status	Revised
Impairment from Pollutant or Pollution:	Pollutant

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

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

State Board Review of Regional Board Conclusion and Recommendation:

State Board Decision Recommendation:	After review of 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 161797, Silver	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

5061

Pollutant:

Silver

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

Fixed station physical/chemical (conventional plus toxic pollutants)

Data Used to Assess Water Quality:

The U.S. Geological survey sampled silver under the Region 6 SWAMP program. Four dissolved silver samples had concentrations less than 1.0 ug/L, the presumed detection limit. Per listing policy Section 6.1.5.5, the objective and CTR standards are presumed to be attained.

Data Reference:

2007. SWAMP Data for the West Walker River and East Walker River Hydrologic Units

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

The California Toxics Rule standard for silver (for protection of freshwater aquatic life) is dependent on hardness. At the hardness values reported for this station, the instantaneous maximum standard ranges from 1.34 to 1.77 ug/L

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

One station, East Walker River at the California-Nevada State Line, was sampled.

Temporal Representation:

Four quarterly samples were collected in 2001 and 2002.

Environmental Conditions:

QAPP Information:

Data meet the quality assurance requirements of the SWAMP QAPP.

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 161797, Silver	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337738

Pollutant:

Silver

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The California Secondary MCL that is incorporated by reference in the Water Quality Control Plan, Lahontan Region for silver is 0.1 mg/L (Water Quality Control Plan, Lahontan Region).

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2018-04-04 and 2022-06-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633

Line of Evidence (LOE) for Decision ID 161797, Silver	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337735

Pollutant:

Silver

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:

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The California Secondary MCL that is incorporated by reference in the Water Quality Control Plan, Lahontan Region for silver is 0.1 mg/L (Water Quality Control Plan, Lahontan Region).

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2020-12-02 and 2022-06-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633

Line of Evidence (LOE) for Decision ID 161797, Silver	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337742

Pollutant:

Silver

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed Nevada Division of Environmental Protection data for East Walker River, below Bridgeport Reservoir to determine beneficial use support, and the results are as follows: 0 of the 0 samples exceeded the evaluation guideline for Silver. Although a total of 5 samples were collected, 5 of these samples were not included in the assessment because the laboratory data reporting limit(s) was above the water quality threshold 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:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The dissolved silver criterion maximum concentration (CMC) to protect aquatic life in freshwater is hardnesss dependent. The criterion when calculated using a default hardness of 100 mg/L is 3.4 ug/L. This criterion was divided by 2 in order to better represent a CMC value as specified in footnote (g) of Table (b)(1) of the California Toxics Rule, 2000.

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2018-04-04 and 2022-06-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633

Line of Evidence (LOE) for Decision ID 161797, Silver	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

5064

Pollutant:

Silver

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

Fixed station physical/chemical (conventional plus toxic pollutants)

Data Used to Assess Water Quality:

The U.S. Geological survey sampled silver under the Region 6 SWAMP program. Four total silver samples had concentrations less than 0.05 ug/L, the detection limit. Per listing policy Section 6.1.5.5, the objective is presumed to be attained.

Data Reference:

2007. SWAMP Data for the West Walker River and East Walker River Hydrologic Units

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

California Maximum Contaminant Levels apply to ambient waters under the Lahontan Basin Plan's "Chemical Constituents" objective. The MCL for silver is 100 ug/L.

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

One station, East Walker River at the California-Nevada State Line, was sampled.

Temporal Representation:

Four quarterly samples were collected in 2001 and 2002.

Environmental Conditions:

QAPP Information:

Data meet the quality assurance requirements of the SWAMP QAPP.

QAPP Information Reference(s):


DECISION ID	161798	Region 6
East Walker River, below Bridgeport Reservoir

Pollutant:	Simazine
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 161798, Simazine	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337743

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:

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The California Maximum Contaminant Level for Simazine incorporated by reference in the Water Quality Control Plan, Lahontan Region is 4 ug/L (Water Quality Control Plan, Lahontan Region).

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2019-12-16 and 2020-11-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633

Line of Evidence (LOE) for Decision ID 161798, Simazine	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337744

Pollutant:

Simazine

LOE Subgroup:

Pollutant-Water

Matrix:

Water

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:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

The evaluation guideline for simazine is the USEPA Aquatic Life Benchmark of 6 ug/L for a nonvascular plant (acute).

Guideline Reference:

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2019-12-16 and 2020-11-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):


DECISION ID	102607	Region 6
East Walker River, below Bridgeport Reservoir

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

Regional Board Conclusion:	This pollutant is being considered for placement on the CWA section 303(d) List under section 3.2 of the Listing Policy. Under section 3.2 a single line of evidence is necessary to assess listing status. Four lines of evidence are available in the administrative record to assess this pollutant, two that assess for MUN and two that assess for AGR. Three of 23 samples exceed the MUN guideline and zero of 23 samples exceed the AGR guideline for sodium. Based on the readily available data and information, the weight of evidence indicates that there is sufficient justification against placing this water segment-pollutant combination on the CWA section 303(d) List. This conclusion is based on the staff findings that: 1. The data used satisfies the data quality requirements of section 6.1.4 of the Policy. 2. The data used satisfies the data quantity requirements of section 6.1.5 of the Policy. 3. Three of 23 samples exceed the MUN guideline and zero of 23 samples exceed the AGR guideline and this does not exceed the allowable frequency listed in Table 3.2 of the Listing Policy. 4. Pursuant to section 3.11 of the Listing Policy, no additional data and information are available indicating that standards are not met.

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

State Board Review of Regional Board Conclusion and Recommendation:

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

Line of Evidence (LOE) for Decision ID 102607, Sodium	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

99027

Pollutant:

Sodium

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Agricultural Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

Water quality data for federal, state, and tribal agencies submitted through the US EPA STorage and RETrival (STORET) database for the 2018 listing cycle.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Water Quality for Agriculture, published by the Food and Agriculture Organization of the United Nations in 1985, contains criteria protective of various agricultural uses of water, including irrigation of various types of crops and stock watering. At or below the sodium threshold of 69 mg/L, agricultural uses of water should not be limited.

Guideline Reference:

Water Quality for Agriculture, Food and Agriculture Organization of the United Nations - Irrigation and Drainage Paper No. 29, Rev 1, Rome (1985)

Spatial Representation:

The samples were collected at 1 monitoring site(s) (21NEV1_WQX-NV09-301-EF-001)

Temporal Representation:

The samples were collected between the dates of 2011-03-09 and 2012-08-07

Environmental Conditions:

QAPP Information:

QAPP not required for federal data

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 102607, Sodium	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

99028

Pollutant:

Sodium

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

Water quality data for federal, state, and tribal agencies submitted through the US EPA STorage and RETrival (STORET) database for the 2018 listing cycle.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Per the Drinking Water Standards and Health Advisories (USEPA 2012), the health advisory for sodium for individuals on a sodium-restricted diet is 20 mg/l.

Guideline Reference:

2012 Edition of the Drinking Water Standards and Health Advisories

Spatial Representation:

The samples were collected at 1 monitoring site(s) (21NEV1_WQX-NV09-301-EF-001)

Temporal Representation:

The samples were collected between the dates of 2011-03-09 and 2012-08-07

Environmental Conditions:

QAPP Information:

QAPP not required for federal data

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 102607, Sodium	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

98489

Pollutant:

Sodium

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Agricultural Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

Water Quality Assessment Data for the 2018 solicitation cycle submitted through CEDEN for the SWAMP RWB6 Monitoring (tissue and water).

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Water Quality for Agriculture, published by the Food and Agriculture Organization of the United Nations in 1985, contains criteria protective of various agricultural uses of water, including irrigation of various types of crops and stock watering. At or below the sodium threshold of 69 mg/L, agricultural uses of water should not be limited.

Guideline Reference:

Water Quality for Agriculture, Food and Agriculture Organization of the United Nations - Irrigation and Drainage Paper No. 29, Rev 1, Rome (1985)

Spatial Representation:

The samples were collected at 1 monitoring site(s) (630EWK001)

Temporal Representation:

The samples were collected between the dates of 2010-10-22 and 2015-10-15

Environmental Conditions:

QAPP Information:

Quality Assurance Program Plan and Standard Operating Procedures for SWAMP program

QAPP Information Reference(s):

Quality Assurance Program Plans, Quality Assurance Project Plans, and Standard Operating Procedures for the SWAMP program

Line of Evidence (LOE) for Decision ID 102607, Sodium	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

98591

Pollutant:

Sodium

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

Water Quality Assessment Data for the 2018 solicitation cycle submitted through CEDEN for the SWAMP RWB6 Monitoring (tissue and water).

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Per the Drinking Water Standards and Health Advisories (USEPA 2012), the health advisory for sodium for individuals on a sodium-restricted diet is 20 mg/l.

Guideline Reference:

2012 Edition of the Drinking Water Standards and Health Advisories

Spatial Representation:

The samples were collected at 1 monitoring site(s) (630EWK001)

Temporal Representation:

The samples were collected between the dates of 2010-10-22 and 2015-10-15

Environmental Conditions:

QAPP Information:

Quality Assurance Program Plan and Standard Operating Procedures for SWAMP program

QAPP Information Reference(s):

Quality Assurance Program Plans, Quality Assurance Project Plans, and Standard Operating Procedures for the SWAMP program


DECISION ID	169948	Region 6
East Walker River, below Bridgeport Reservoir

Pollutant:	Sodium Adsorption Ratio (SAR)
Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)(2018)
Revision Status	Revised
Impairment from Pollutant or Pollution:	Pollutant

Regional Board Conclusion:	This pollutant is being considered for placement on the CWA section 303(d) List under section 3.2 of the Listing Policy. Under section 3.2 a single line of evidence is necessary to assess listing status. Three lines of evidence is available in the administrative record to assess this pollutant. Zero of 13 samples exceed the water quality objective. The one exceeding data point calculated during the previous assessment cycle may have been calculated incorrectly. Based on the readily available data and information, the weight of evidence indicates that there is sufficient justification against placing this water segment-pollutant combination on the CWA section 303(d) List. This conclusion is based on the staff findings that: 1. The data used satisfies the data quality requirements of section 6.1.4 of the Policy. 2. The data used satisfies the data quantity requirements of section 6.1.5 of the Policy. 3. Zero of 13 samples exceeded the objective and this sample size is insufficient to determine, with the power and confidence of the Listing Policy, the applicable beneficial use support rating. A minimum of 26 samples are needed to determine if a beneficial use is fully supported using table 3.2. 4. Pursuant to SECTION 3.11 of the Listing Policy, no additional data and information are available indicating that standards are not met.

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

State Board Review of Regional Board Conclusion and Recommendation:

State Board Decision Recommendation:

Line of Evidence (LOE) for Decision ID 169948, Sodium Adsorption Ratio (SAR)	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

133527

Pollutant:

Sodium Adsorption Ratio (SAR)

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Agricultural Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data were collected by the Region 6 SWAMP program between 2010 and 2015. Annual average SAR ratios ranged from 0.51 to 0.93. No SAR annual average exceeded the objective of 2. 2 samples of each analyte were thrown out in 2011 because of hold time violations.

Data Reference:

Water Quality Assessment Data for the 2018 solicitation cycle submitted through CEDEN for the SWAMP RWB6 Monitoring (tissue and water).

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

The objective for Sodium Absorption Ratio (SAR) in the East Walker River (below Bridgeport Reservoir), as stipulated in the Lahontan Basin Plan 3-11, is a ratio not to exceed 2. SAR is calculated as Na/Sqrt((Ca+Mg)/2 in annual average fashion, and the formula uses milliequivalent (mEq) concentrations of each ion. To calculate mEq, the formula is (ion mg/L / molar mass)*valence.

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

Data were collected from one station, 631EWK001, located at the CA/NV stateline.

Temporal Representation:

Data were collected once in 2010 and 2011, and in quarterly fashion from 2012 to 2015.

Environmental Conditions:

QAPP Information:

Data were collected in accordance with the SWAMP QAPP.

QAPP Information Reference(s):

Quality Assurance Program Plans, Quality Assurance Project Plans, and Standard Operating Procedures for the SWAMP program

Line of Evidence (LOE) for Decision ID 169948, Sodium Adsorption Ratio (SAR)	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

351282

Pollutant:

Sodium Adsorption Ratio (SAR)

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Agricultural Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed SWAMP data for this site and time period and 0 of 6 samples exceeded the water quality objective for Sodium Absorption Ratio.

Data Reference:

Benthic, Field, Habitat, Tissue, Toxicity, WQ from the Surface Water Ambient Monitoring Program for the 2026 Integrated Report in Region 6

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

The Water Quality Control Plan for the Lahontan Region contains a site specific water quality objective for the Sodium Absorption Ratio for waterbodies of the East Walker River HUC applicable to this site, it is an annual average of no greater than 2.

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: East Walker River, at CA/NV state line (630EWK001)

Temporal Representation:

The samples were collected between 2016-03-17 and 2021-11-23.

Environmental Conditions:

QAPP Information:

Generic SWAMP QAPrP

QAPP Information Reference(s):

WQX from the NWQMP for the 2026 Integrated Report in Region 6

Line of Evidence (LOE) for Decision ID 169948, Sodium Adsorption Ratio (SAR)	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

351283

Pollutant:

Sodium Adsorption Ratio (SAR)

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Agricultural Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed SWAMP data for this site and time period and 0 of 1 samples exceeded the water quality objective for Sodium Absorption Ratio.

Data Reference:

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected 1 monitoring site: East Fork Walker River @ Stateline (21NEV1_WQX-NV09-301-EF-001)

Temporal Representation:

The samples were collected between 2014-05-12 and 2014-07-24.

Environmental Conditions:

QAPP Information:

NDEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633


DECISION ID	168665	Region 6
East Walker River, below Bridgeport Reservoir

Pollutant:	Specific Conductivity
Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)(2018)
Revision Status	Revised
Impairment from Pollutant or Pollution:	Pollutant

Regional Board Conclusion:	This pollutant is being considered for placement on the CWA section 303(d) List under section 3.2 of the Listing Policy. Under section 3.2 a single line of evidence is necessary to assess listing status. Six lines of evidence are available in the administrative record to assess this pollutant. Zero of 60 samples exceed the objective for specific conductance (MCL). Based on the readily available data and information, the weight of evidence indicates that there is sufficient justification against placing this water segment-pollutant combination on the CWA section 303(d) List. This conclusion is based on the staff findings that: 1. The data used satisfies the data quality requirements of section 6.1.4 of the Policy. 2. The data used satisfies the data quantity requirements of section 6.1.5 of the Policy. 3. Zero of 60 samples exceeded the objective (MCL) and this does not exceed the allowable frequency listed in Table 3.2 of the Listing Policy. 4. Pursuant to section 3.11 of the Listing Policy, no additional data and information are available indicating that standards are not met.

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

State Board Review of Regional Board Conclusion and Recommendation:

State Board Decision Recommendation:

Line of Evidence (LOE) for Decision ID 168665, Specific Conductivity	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

340675

Pollutant:

Specific Conductivity

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

None

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

Benthic, Field, Habitat, Tissue, Toxicity, WQ from the Surface Water Ambient Monitoring Program for the 2026 Integrated Report in Region 6

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

California Maximum Contaminant Levels (MCLs) apply to ambient waters under the Lahontan Basin Plan's 'Chemical Constituents' objective. The California Secondary MCL for specific conductivity is 900 uS/cm.

Guideline Reference:

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

Spatial Representation:

The samples were collected at 1 monitoring site: 630EWK001 (East Walker River, at CA/NV state line).

Temporal Representation:

The samples were collected between the dates of 2016-03-17 and 2022-06-01

Environmental Conditions:

QAPP Information:

Generic SWAMP QAPrP

QAPP Information Reference(s):

2007. SWAMP Data for the West Walker River and East Walker River Hydrologic Units

Line of Evidence (LOE) for Decision ID 168665, Specific Conductivity	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

5050

Pollutant:

Specific Conductance

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

None

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

Fixed station physical/chemical (conventional plus toxic pollutants)

Data Used to Assess Water Quality:

The U.S. Geological Survey measured specific conductance under the Region 6 SWAMP program, at quarterly intervals between 2001 and 2005. Fourteen field measurements of specific conductance ranged from 144 to 271 uS/cm. An additional 6 laboratory measurements were taken for samples collected on the same dates as field measurements. Laboratory specific conductance ranged from 151 to 202 uS/cm. The MCL was not exceeded.

Data Reference:

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

California Maximum Contaminant Levels (MCLs) apply to ambient waters under the Lahontan Basin Plan's "Chemical Constituents" objective. The MCL for specific conductance is 900 microsiemens per centimeter (uS/cm).

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

One station, East Walker River at the California-Nevada State Line, was sampled.

Temporal Representation:

Fourteen quarterly field measurements and 6 laboratory measurements of specific conductance were taken between 2001 and 2005.

Environmental Conditions:

QAPP Information:

Data meet the quality assurance requirements of the SWAMP QAPP.

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 168665, Specific Conductivity	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

44383

Pollutant:

Specific Conductivity

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

None

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed SWAMP data for East Walker River, below Bridgeport Reservoir to determine beneficial use support and results are as follows: 0 of 9 samples exceed the criterion for Conductivity(Us).

Data Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

The California Secondary MCL that is incorporated by reference in the Water Quality Control Plan, Lahontan Region for specific conductance is 900 uS/cm (Water Quality Control Plan, Lahontan Region).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

Data for this line of evidence for East Walker River, below Bridgeport Reservoir was collected at 1 monitoring site [ East Walker River, at CA/NV state line]

Temporal Representation:

Data was collected over the time period 8/14/2007-12/26/2007.

Environmental Conditions:

Staff is not aware of any special conditions that might affect interpretation of the data.

QAPP Information:

2002 QAMP (Quality Assurance Management Plan) for the State of California's Surface Water Ambient Monitoring Program

QAPP Information Reference(s):

Quality Assurance Management Plan for the State of California's Surface Water Ambient Monitoring Program. Sacramento, CA. State Water Resources Control Board. SWAMP. December 2002 (1st version)

Line of Evidence (LOE) for Decision ID 168665, Specific Conductivity	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

97268

Pollutant:

Specific Conductivity

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:

Data Reference:

Water Quality Assessment Data for the 2018 solicitation cycle submitted through CEDEN for the SWAMP RWB6 Monitoring (tissue and water).

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

California Maximum Contaminant Levels (MCLs) apply to ambient waters under the Lahontan Basin Plan's \Chemical Constituents\" objective. The California Secondary MCL for specific conductivity is 900 uS/cm."

Guideline Reference:

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

Spatial Representation:

The samples were collected at 1 monitoring site(s) (630EWK001)

Temporal Representation:

The samples were collected between the dates of 2010-09-13 and 2015-10-15

Environmental Conditions:

QAPP Information:

Quality Assurance Program Plan and Standard Operating Procedures for SWAMP program

QAPP Information Reference(s):

Quality Assurance Program Plans, Quality Assurance Project Plans, and Standard Operating Procedures for the SWAMP program

Line of Evidence (LOE) for Decision ID 168665, Specific Conductivity	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

341866

Pollutant:

Specific Conductivity

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

None

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

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

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2011-03-09 and 2013-10-21

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633

Line of Evidence (LOE) for Decision ID 168665, Specific Conductivity	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

340597

Pollutant:

Specific Conductivity

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

None

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

Benthic, Field, Habitat, WQ from the Surface Water Ambient Monitoring Program for the 2026 Integrated Report in Region 6

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

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

Spatial Representation:

The samples were collected at 1 monitoring site: 630PS0163 (East Walker River ~1mi below Murphy Pond).

Temporal Representation:

The samples were collected between the dates of 2015-06-15 and 2015-06-15

Environmental Conditions:

QAPP Information:

Generic SWAMP QAPrP

QAPP Information Reference(s):

Water Quality Assessment Data for the 2018 solicitation cycle submitted through CEDEN for the SWAMP RWB6 Monitoring (tissue and water).


DECISION ID	161799	Region 6
East Walker River, below Bridgeport Reservoir

Pollutant:	Sulfates
Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)(2018)
Revision Status	Revised
Impairment from Pollutant or Pollution:	Pollutant

Regional Board Conclusion:	This pollutant is being considered for placement on the CWA section 303(d) List under section 3.2 of the Listing Policy. Under section 3.2 a single line of evidence is necessary to assess listing status. Seven lines of evidence are available in the administrative record to assess this pollutant. Zero of the 65 samples exceed the water quality objective (MCL) for sulfate. Based on the readily available data and information, the weight of evidence indicates that there is sufficient justification against placing this water segment-pollutant combination on the CWA section 303(d) List. This conclusion is based on the staff findings that: 1. The data used satisfies the data quality requirements of section 6.1.4 of the Policy. 2. The data used satisfies the data quantity requirements of section 6.1.5 of the Policy. 3. Zero of the 65 samples exceed the water quality objective (MCL) for sulfate, and this does not exceed the allowable frequency listed in Table 3.2 of the Listing Policy. 4. Pursuant to section 3.11 of the Listing Policy, no additional data and information are available indicating that standards are not met.

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

State Board Review of Regional Board Conclusion and Recommendation:

State Board Decision Recommendation:

Line of Evidence (LOE) for Decision ID 161799, Sulfates	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

98594

Pollutant:

Sulfates

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

The California Secondary MCL that is incorporated by reference in the Water Quality Control Plan, Lahontan Region for Sulfate 250 mg/L (Water Quality Control Plan, Lahontan Region).

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site(s) (630EWK001)

Temporal Representation:

The samples were collected between the dates of 2010-10-22 and 2015-10-15

Environmental Conditions:

QAPP Information:

Quality Assurance Program Plan and Standard Operating Procedures for SWAMP program

QAPP Information Reference(s):

Quality Assurance Program Plans, Quality Assurance Project Plans, and Standard Operating Procedures for the SWAMP program

Line of Evidence (LOE) for Decision ID 161799, Sulfates	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

5052

Pollutant:

Sulfates

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

Fixed station physical/chemical (conventional plus toxic pollutants)

Data Used to Assess Water Quality:

The U.S. Geological survey sampled sulfate under the Region 6 SWAMP program between 2003 and 2005. Sulfate concentrations in 7 samples ranged from 5.1 to 23 mg/L. The MCL was not violated.

Data Reference:

2007. SWAMP Data for the West Walker River and East Walker River Hydrologic Units

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

California Maximum Contaminant Levels (MCLs) apply to ambient waters under the Lahontan Basin Plan's "Chemical Constituents" objective. The MCL for sulfate is 250 mg/L.

Objective/Criterion Reference:

2007. SWAMP Data for the West Walker River and East Walker River Hydrologic Units

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

One station, East Walker River at the California-Nevada State Line, was sampled.

Temporal Representation:

Seven samples were collected approximately quarterly between November 2003 and August 2005.

Environmental Conditions:

QAPP Information:

Data meet the quality assurance requirements of the SWAMP QAPP.

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 161799, Sulfates	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

99030

Pollutant:

Sulfates

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:

Data Reference:

Water quality data for federal, state, and tribal agencies submitted through the US EPA STorage and RETrival (STORET) database for the 2018 listing cycle.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The California Secondary MCL that is incorporated by reference in the Water Quality Control Plan, Lahontan Region for Sulfate 250 mg/L (Water Quality Control Plan, Lahontan Region).

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site(s) (21NEV1_WQX-NV09-301-EF-001)

Temporal Representation:

The samples were collected between the dates of 2011-03-09 and 2012-08-07

Environmental Conditions:

QAPP Information:

QAPP not required for federal data

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 161799, Sulfates	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

32235

Pollutant:

Sulfates

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total Dissolved

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Zero of 2 samples exceeded the Secondary MCLs objective.

Data Reference:

Secondary Maximum Contaminant Levels and Compliance. CCR Title 22 section 64449.

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

California Secondary Maximum Contaminant Levels (SMCLs) apply to ambient waters under the Lahontan Basin Plan's "Chemical Constituents" objective. The SMCL for Sulfates (SO4) is 250 mg/L.

Objective/Criterion Reference:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

Data were collected at the following station: 630EWK001-East Walker River, below Bridgeport Reservoir.

Temporal Representation:

Samples were collected on the following dates: 8/14/2007, 11/8/2007

Environmental Conditions:

QAPP Information:

2002 QAMP (Quality Assurance Management Plan) for the State of California's Surface Water Ambient Monitoring Program

QAPP Information Reference(s):

Quality Assurance Management Plan for the State of California's Surface Water Ambient Monitoring Program. Sacramento, CA. State Water Resources Control Board. SWAMP. December 2002 (1st version)

Line of Evidence (LOE) for Decision ID 161799, Sulfates	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

341930

Pollutant:

Sulfates

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The California Secondary MCL that is incorporated by reference in the Water Quality Control Plan, Lahontan Region for Sulfate 250 mg/L (Water Quality Control Plan, Lahontan Region).

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2014-01-22 and 2017-03-14

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633

Line of Evidence (LOE) for Decision ID 161799, Sulfates	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

340732

Pollutant:

Sulfates

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

Benthic, Field, Habitat, WQ from the Surface Water Ambient Monitoring Program for the 2026 Integrated Report in Region 6

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

The California Secondary MCL that is incorporated by reference in the Water Quality Control Plan, Lahontan Region for Sulfate 250 mg/L (Water Quality Control Plan, Lahontan Region).

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 630PS0163 (East Walker River ~1mi below Murphy Pond).

Temporal Representation:

The samples were collected between the dates of 2015-06-15 and 2015-06-15

Environmental Conditions:

QAPP Information:

Generic SWAMP QAPrP

QAPP Information Reference(s):

Benthic, Field, Habitat, Tissue, Toxicity, WQ from the Surface Water Ambient Monitoring Program for the 2026 Integrated Report in Region 6

Line of Evidence (LOE) for Decision ID 161799, Sulfates	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

340753

Pollutant:

Sulfates

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed SWAMP RWB6 Monitoring data for East Walker River, below Bridgeport Reservoir to determine beneficial use support and results are as follows: 0 of 18 samples exceeded the water quality threshold for Sulfate.

Data Reference:

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

The California Secondary MCL that is incorporated by reference in the Water Quality Control Plan, Lahontan Region for Sulfate 250 mg/L (Water Quality Control Plan, Lahontan Region).

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 630EWK001 (East Walker River, at CA/NV state line).

Temporal Representation:

The samples were collected between the dates of 2016-03-17 and 2021-11-23

Environmental Conditions:

QAPP Information:

Generic SWAMP QAPrP

QAPP Information Reference(s):

WQX from the NWQMP for the 2026 Integrated Report in Region 6


DECISION ID	161800	Region 6
East Walker River, below Bridgeport Reservoir

Pollutant:	Thallium
Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)(2018)
Revision Status	Revised
Impairment from Pollutant or Pollution:	Pollutant

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

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

State Board Review of Regional Board Conclusion and Recommendation:

State Board Decision Recommendation:	After review of 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 161800, Thallium	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337768

Pollutant:

Thallium

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:

Data Reference:

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The California Maximum Contaminant Level for thallium incorporated by reference in the Water Quality Control Plan, Lahontan Region is 0.002 mg/L (Water Quality Control Plan, Lahontan Region).

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2018-04-04 and 2022-06-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633

Line of Evidence (LOE) for Decision ID 161800, Thallium	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337757

Pollutant:

Thallium

LOE Subgroup:

Pollutant-Water

Matrix:

Water

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:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

The Gold Book states that thallium chronic toxicity to one species of fish occurs at concentrations as low as 20 ug/L after 2,6000 hours of exposure.

Guideline Reference:

Quality Criteria for Water 1986. United States Environmental Protection Agency. Office of Water. Regulations and Standards. Washington D.C. EPA 440/5-86-001.

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2018-04-04 and 2022-06-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633

Line of Evidence (LOE) for Decision ID 161800, Thallium	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

7712

Pollutant:

Thallium

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

Fixed station physical/chemical (conventional plus toxic pollutants)

Data Used to Assess Water Quality:

The U.S. Geological Survey sampled thallium under the Region 6 SWAMP program. Dissolved thallium concentrations in four samples were all below the detection limit. Per listing policy Section 6.1.5.5, the objective is presumed to be attained.

Data Reference:

2007. SWAMP Data for the West Walker River and East Walker River Hydrologic Units

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

The U.S. Environmental Protection Agency's Lowest Observed Effect Levels (LOEL) criteria include an acute toxicity value of 1400 ug/L,and a chronic toxicity value of 40 ug/L. The criteria also include an "Other" limit of 20 ug/L based on 2600 hour exposure of one fish species.

Objective/Criterion Reference:

Quality Criteria for Water 1986. United States Environmental Protection Agency. Office of Water. Regulations and Standards. Washington D.C. EPA 440/5-86-001.

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

One station, East Walker River at the California-Nevada State Line, was sampled.

Temporal Representation:

Four quarterly samples were collected in 2001 and 2002.

Environmental Conditions:

QAPP Information:

Data meet the quality assurance requirements of the SWAMP QAPP.

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 161800, Thallium	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337753

Pollutant:

Thallium

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Commercial or recreational collection of fish, shellfish, or organisms

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The Thallium criteria for the protection of human health from consumption of organisms only is 6.3 ug/L (California Toxics Rule, 2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2018-04-04 and 2022-06-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633

Line of Evidence (LOE) for Decision ID 161800, Thallium	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337762

Pollutant:

Thallium

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

The Gold Book states that thallium chronic toxicity to one species of fish occurs at concentrations as low as 20 ug/L after 2,6000 hours of exposure.

Guideline Reference:

Quality Criteria for Water 1986. United States Environmental Protection Agency. Office of Water. Regulations and Standards. Washington D.C. EPA 440/5-86-001.

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2022-02-08 and 2022-06-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633

Line of Evidence (LOE) for Decision ID 161800, Thallium	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337764

Pollutant:

Thallium

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Commercial or recreational collection of fish, shellfish, or organisms

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The Thallium criteria for the protection of human health from consumption of organisms only is 6.3 ug/L (California Toxics Rule, 2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2022-02-08 and 2022-06-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633

Line of Evidence (LOE) for Decision ID 161800, Thallium	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337763

Pollutant:

Thallium

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The California Maximum Contaminant Level for thallium incorporated by reference in the Water Quality Control Plan, Lahontan Region is 0.002 mg/L (Water Quality Control Plan, Lahontan Region).

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2022-02-08 and 2022-06-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633

Line of Evidence (LOE) for Decision ID 161800, Thallium	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

5124

Pollutant:

Thallium

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

Fixed station physical/chemical (conventional plus toxic pollutants)

Data Used to Assess Water Quality:

The U.S. Geological Survey sampled thallium. under the Region 6 SWAMP program. Concentrations of total thallium in four samples were all below the detection level. Per listing policy Section 6.1.5.5, the objective is presumed to be attained.

Data Reference:

2007. SWAMP Data for the West Walker River and East Walker River Hydrologic Units

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

California Maximum Contaminant Levels apply to ambient waters under the Lahontan Basin Plan's "Chemical Constituents" objective. The MCL for thallium is 2 ug/L.

The California Toxics Rule water and fish consumption standard (for waters designated MUN) is 1.7 ug/L

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

One station, East Walker River at the California-Nevada State Line, was sampled.

Temporal Representation:

Four quarterly samples were collected in 2001 and 2002.

Environmental Conditions:

QAPP Information:

Data meet the quality assurance requirements of the SWAMP QAPP.

QAPP Information Reference(s):


DECISION ID	161825	Region 6
East Walker River, below Bridgeport Reservoir

Pollutant:	Thiobencarb
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 161825, Thiobencarb	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337770

Pollutant:

Thiobencarb

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Not Recorded

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The California Maximum Contaminant Level for Thiobencarb incorporated by reference in the Water Quality Control Plan, Lahontan Region is 70 ug/L (Water Quality Control Plan, Lahontan Region).

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2019-12-16 and 2020-11-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633

Line of Evidence (LOE) for Decision ID 161825, Thiobencarb	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337769

Pollutant:

Thiobencarb

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Not Recorded

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:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

The evaluation guideline for thiobencarb is the USEPA Aquatic Life Benchmark of 1 ug/L for an invertebrate (chronic).

Guideline Reference:

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2019-12-16 and 2020-11-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):


DECISION ID	76597	Region 6
East Walker River, below Bridgeport Reservoir

Pollutant:	Total Kjeldahl Nitrogen (TKN)
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	Revised
Impairment from Pollutant or Pollution:	Pollutant

Regional Board Conclusion:	This pollutant is being considered for placement on the section 303(d) list under section 3.1 of the Listing Policy. Under section 3.1 a single line of evidence is necessary to assess listing status. Two lines of evidence, one which evaluates Dissolved Kjeldahl Nitrogen (DKN) data and one which evaluates Total Kjeldahl Nitrogen (TKN) data are available in the administrative record to assess this pollutant. 0 of 2 DKN samples and 0 of 16 TKN samples exceed the water quality objectives. 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 satisfy the data quality requirements of section 6.1.4 of the Policy. 2. The data used satisfy the data quantity requirements of section 6.1.5 of the Policy. 3. 0 of 16 TKN samples exceed the objectives and this does not exceed the allowable frequency listed in table 3.1. 4. Pursuant to section 3.11 of the Listing Policy, no additional data and information are available indicating that standards are not met.

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

State Board Review of Regional Board Conclusion and Recommendation:

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

Line of Evidence (LOE) for Decision ID 76597, Total Kjeldahl Nitrogen (TKN)	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

7748

Pollutant:

Dissolved Kjeldahl Nitrogen

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

Fixed station physical/chemical (conventional plus toxic pollutants)

Data Used to Assess Water Quality:

The U.S. Geological Survey collected two samples under the Region 6 SWAMP program in August and November 2003. Concentrations of dissolved Kjeldahl nitrogen were 0.9 and 0.38 mg/L. No associated data on algae or macrophytes were available for assessment of compliance with the objective for biostimulatory substances.

Data Reference:

2007. SWAMP Data for the West Walker River and East Walker River Hydrologic Units

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

There are no site-specific objectives for dissolved Kjeldahl nitrogen. The Lahontan Basin Plan's narrative objective for biostimulatory substances states: "Waters shall not contain biostimulatory substances in concentrations that promote aquatic growths to the extent that such growths cause nuisance or adversely affect the water for beneficial uses."

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

One station, East Walker River at the California-Nevada State Line, was sampled.

Temporal Representation:

Two samples were collected in August and November 2003.

Environmental Conditions:

QAPP Information:

Data meet the quality assurance requirements of the SWAMP QAPP.

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 76597, Total Kjeldahl Nitrogen (TKN)	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

7749

Pollutant:

Total Kjeldahl Nitrogen (TKN)

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

Fixed station physical/chemical (conventional plus toxic pollutants)

Data Used to Assess Water Quality:

The U.S. Geological Survey collected 16 quarterly samples under the Region 6 SWAMP program between 2001 and 2005. Concentrations of total Kjeldahl nitrogen ranged from 0.37 to 3.1 mg/L. No associated data on algae or macrophytes were available for assessment of compliance with the objective for biostimulatory substances.

Data Reference:

2007. SWAMP Data for the West Walker River and East Walker River Hydrologic Units

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

There is no site-specific objective for total Kjeldahl nitrogen. The Lahontan Basin Plan's narrative objective for biostimulatory substances states: "Waters shall not contain biostimulatory substances in concentrations that promote aquatic growths to the extent that such growths cause nuisance or adversely affect the water for beneficial uses."

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

One station, East Walker River at the California-Nevada State Line, was sampled.

Temporal Representation:

Sixteen quarterly samples were collected between 2001 and 2005.

Environmental Conditions:

QAPP Information:

Data meet the quality assurance requirements of the SWAMP QAPP.

QAPP Information Reference(s):


DECISION ID	161801	Region 6
East Walker River, below Bridgeport Reservoir

Pollutant:	Toxaphene
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:

Line of Evidence (LOE) for Decision ID 161801, Toxaphene	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337774

Pollutant:

Toxaphene

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed Nevada Division of Environmental Protection data for East Walker River, below Bridgeport Reservoir to determine beneficial use support, and the results are as follows: 0 of the 0 samples exceeded the evaluation guideline for Toxaphene. Although a total of 2 samples were collected, 2 of these samples were not included in the assessment because the laboratory data reporting limit(s) was above the water quality threshold 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:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The toxaphene criterion for the protection of human health from the consumption of water and organisms is 0.00073 ug/L (California Toxics Rule, 2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2019-12-16 and 2020-11-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633

Line of Evidence (LOE) for Decision ID 161801, Toxaphene	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337776

Pollutant:

Toxaphene

LOE Subgroup:

Pollutant-Water

Matrix:

Water

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 Nevada Division of Environmental Protection data for East Walker River, below Bridgeport Reservoir to determine beneficial use support, and the results are as follows: 0 of the 0 samples exceeded the evaluation guideline for Toxaphene. Although a total of 2 samples were collected, 2 of these samples were not included in the assessment because the laboratory data reporting limit(s) was above the water quality threshold 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:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The toxaphene criterion continuous concentration (expressed as a 4-day average) to protect aquatic life in freshwater is 0.0002 ug/L (California Toxics Rule, 2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2019-12-16 and 2020-11-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633

Line of Evidence (LOE) for Decision ID 161801, Toxaphene	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337775

Pollutant:

Toxaphene

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:

Water Board staff assessed Nevada Division of Environmental Protection data for East Walker River, below Bridgeport Reservoir to determine beneficial use support, and the results are as follows: 0 of the 0 samples exceeded the evaluation guideline for Toxaphene. Although a total of 2 samples were collected, 2 of these samples were not included in the assessment because the laboratory data reporting limit(s) was above the water quality threshold 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:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The toxaphene criterion for the protection of human health from consumption of organisms only is 0.00075 ug/L (California Toxics Rule, 2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2019-12-16 and 2020-11-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633


DECISION ID	161802	Region 6
East Walker River, below Bridgeport Reservoir

Pollutant:	Trichloroethylene/TCE
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:

Line of Evidence (LOE) for Decision ID 161802, Trichloroethylene/TCE	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337777

Pollutant:

Trichloroethylene/TCE

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:

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The trichloroethylene criteria for the protection of human health from the consumption of water and organisms is 2.7 ug/L (California Toxics Rule, 2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2020-11-30 and 2020-11-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633

Line of Evidence (LOE) for Decision ID 161802, Trichloroethylene/TCE	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337778

Pollutant:

Trichloroethylene/TCE

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Commercial or recreational collection of fish, shellfish, or organisms

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The Trichloroethylene criteria for the protection of human health from consumption of organisms only is 81 ug/L (California Toxics Rule, 2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2020-11-30 and 2020-11-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633


DECISION ID	161744	Region 6
East Walker River, below Bridgeport Reservoir

Pollutant:	Trichlorophenoxyacetic Acid, 2,4,5-
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 161744, Trichlorophenoxyacetic Acid, 2,4,5-	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337779

Pollutant:

Trichlorophenoxyacetic Acid, 2,4,5-

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Not Recorded

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

The USEPA Health Advisory for lifetime exposure to trichlorophenoxyacetic acid, 2,4,5- as a drinking water level is a concentration of 0.07 mg/L.

Guideline Reference:

2018 Edition of the Drinking Water Standards and Health Advisories

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2019-12-16 and 2020-11-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633


DECISION ID	161803	Region 6
East Walker River, below Bridgeport Reservoir

Pollutant:	Trifluralin
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 161803, Trifluralin	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337781

Pollutant:

Trifluralin

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:

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

The USEPA Health Advisory for Trifluralin as a drinking water level with a one in a million cancer risk is 0.004 mg/L.

Guideline Reference:

2012 Edition of the Drinking Water Standards and Health Advisories

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2019-12-16 and 2020-11-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633

Line of Evidence (LOE) for Decision ID 161803, Trifluralin	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337780

Pollutant:

Trifluralin

LOE Subgroup:

Pollutant-Water

Matrix:

Water

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:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

UC Davis Aquatic Life Criteria: Aquatic life should not be affected unacceptably if the four-day average concentration of Trifluralin does not exceed 0.33 ug/L in the water column more than once every three years on average (Bower, et al. 2017).

Guideline Reference:

Water Quality Criteria Report for Trifluralin Phase III: Application of the pesticide water quality criteria methodology. Department of Environmental Toxicology University of California, Davis.

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2019-12-16 and 2020-11-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633


DECISION ID	161812	Region 6
East Walker River, below Bridgeport Reservoir

Pollutant:	Vanadium
Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)(2018)
Revision Status	Revised
Impairment from Pollutant or Pollution:	Pollutant

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

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

State Board Review of Regional Board Conclusion and Recommendation:

State Board Decision Recommendation:	After review of 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 161812, Vanadium	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

7715

Pollutant:

Vanadium

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

Fixed station physical/chemical (conventional plus toxic pollutants)

Data Used to Assess Water Quality:

The U.S. Geological Survey sampled vanadium under the Region 6 SWAMP program. Concentrations of dissolved vanadium in four samples were all below the detection level. Per listing policy Section 6.1.5.5, the criterion is presumed to be attained.

Data Reference:

2007. SWAMP Data for the West Walker River and East Walker River Hydrologic Units

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

There are no state or federal standards or criteria for vanadium for the projection of freshwater aquatic life.

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

One station, East Walker River at the California-Nevada State Line, was sampled.

Temporal Representation:

Four quarterly samples were collected in 2001 and 2002.

Environmental Conditions:

QAPP Information:

Data meet the quality assurance requirements of the SWAMP QAPP.

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 161812, Vanadium	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

7714

Pollutant:

Vanadium

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

Fixed station physical/chemical (conventional plus toxic pollutants)

Data Used to Assess Water Quality:

The U.S. Geological Survey sampled vanadium under the Region 6 SWAMP program. Concentrations of total vanadium in four samples were all below the detection level. Per listing policy Section 6.1.5.5, the criterion is presumed to be attained.

Data Reference:

2007. SWAMP Data for the West Walker River and East Walker River Hydrologic Units

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

The California Notification Level criterion for vanadium in drinking water is 50 ug/L.

Objective/Criterion Reference:

Drinking Water Notification and Response Levels: An Overview

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

One station, East Walker River at the California-Nevada State Line, was sampled.

Temporal Representation:

Four quarterly samples were collected in 2001 and 2002.

Environmental Conditions:

QAPP Information:

Data meet the quality assurance requirements of the SWAMP QAPP.

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 161812, Vanadium	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337790

Pollutant:

Vanadium

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:

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Drinking Water Notification and Response Levels: An Overview

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2020-12-02 and 2022-06-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633

Line of Evidence (LOE) for Decision ID 161812, Vanadium	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337793

Pollutant:

Vanadium

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Agricultural Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Waters designated as AGR shall not contain concentrations of chemical constituents in amounts that adversely affect the water for beneficial uses (Water Quality Control Plan, Lahontan Region).

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Water Quality for Agriculture, published by the Food and Agriculture Organization of the United Nations in 1985, contains criteria protective of various agricultural uses of water. These criteria were used to translate narrative water quality objectives for chemical constituents that prohibit chemicals in concentrations that would impair agricultural uses of water. The 0.1 mg/L criteria is for the recommended maximum concentrations of vanadium in irrigation water

Guideline Reference:

Water Quality for Agriculture, Food and Agriculture Organization of the United Nations - Irrigation and Drainage Paper No. 29, Rev 1, Rome (1985)

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2020-12-02 and 2022-06-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633

Line of Evidence (LOE) for Decision ID 161812, Vanadium	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337788

Pollutant:

Vanadium

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Agricultural Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Waters designated as AGR shall not contain concentrations of chemical constituents in amounts that adversely affect the water for beneficial uses (Water Quality Control Plan, Lahontan Region).

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Water Quality for Agriculture, published by the Food and Agriculture Organization of the United Nations in 1985, contains criteria protective of various agricultural uses of water. These criteria were used to translate narrative water quality objectives for chemical constituents that prohibit chemicals in concentrations that would impair agricultural uses of water. The 0.1 mg/L criteria is for the recommended maximum concentrations of vanadium in irrigation water

Guideline Reference:

Water Quality for Agriculture, Food and Agriculture Organization of the United Nations - Irrigation and Drainage Paper No. 29, Rev 1, Rome (1985)

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2020-12-02 and 2022-06-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633

Line of Evidence (LOE) for Decision ID 161812, Vanadium	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337791

Pollutant:

Vanadium

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Drinking Water Notification and Response Levels: An Overview

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2020-12-02 and 2022-06-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633


DECISION ID	161805	Region 6
East Walker River, below Bridgeport Reservoir

Pollutant:	Zinc
Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)(2018)
Revision Status	Revised
Impairment from Pollutant or Pollution:	Pollutant

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

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

State Board Review of Regional Board Conclusion and Recommendation:

State Board Decision Recommendation:	After review of 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 161805, Zinc	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

99053

Pollutant:

Zinc

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

Water quality data for federal, state, and tribal agencies submitted through the US EPA STorage and RETrival (STORET) database for the 2018 listing cycle.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site(s) (21NEV1_WQX-NV09-301-EF-001)

Temporal Representation:

The samples were collected between the dates of 2012-08-07 and 2012-08-07

Environmental Conditions:

QAPP Information:

QAPP not required for federal data

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 161805, Zinc	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

5125

Pollutant:

Zinc

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

Fixed station physical/chemical (conventional plus toxic pollutants)

Data Used to Assess Water Quality:

The U.S. Geological Survey sampled zinc quarterly under the Region 6 SWAMP program in 2001 and 2002. Dissolved zinc concentrations in three of four samples were below the detection level and the fourth sample was 2 ug/L. The CTR standards were not violated. .

Data Reference:

2007. SWAMP Data for the West Walker River and East Walker River Hydrologic Units

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

The California Toxics Rule (CTR) freshwater aquatic life standards for zinc are dependent on hardness. At the hardness levels reported for this station, the acute (1-hour average) standard ranges from 73.53 to 84.23 ug/L and the chronic (4-day average) standard ranges from 74.13 to 84.92ug/L.)

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

One station, East Walker River at the California-Nevada State Line, was sampled.

Temporal Representation:

Four quarterly samples were collected in 2001 and 2002.

Environmental Conditions:

QAPP Information:

Data meet the quality assurance requirements of the SWAMP QAPP.

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 161805, Zinc	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

5126

Pollutant:

Zinc

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

Fixed station physical/chemical (conventional plus toxic pollutants)

Data Used to Assess Water Quality:

The U.S. Geological Survey sampled zinc under the Region 6 SWAMP program in 2001 and 2002. Four total zinc samples had concentrations ranging from below the detection level to 2 ug/L. The MCL was not violated. .

Data Reference:

2007. SWAMP Data for the West Walker River and East Walker River Hydrologic Units

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

California Maximum Contaminant Levels apply to ambient waters under the Lahontan Basin Plan's "Chemical Constituents" objective. The MCL for zinc is 5000 ug/L.

The California Toxics Rule water and fish consumption standard (for waters designated MUN) is 1.7 ug/L

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

One station, East Walker River at the California-Nevada State Line, was sampled.

Temporal Representation:

Four quarterly samples were collected in 2001 and 2002.

Environmental Conditions:

QAPP Information:

Data meet the quality assurance requirements of the SWAMP QAPP.

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 161805, Zinc	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337796

Pollutant:

Zinc

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The dissolved zinc criterion continuous concentration (expressed as a 4-day average) to protect aquatic life in freshwater is hardness dependent. The criterion when calculated using a default hardness of 100 mg/L is 120 ug/L (California Toxics Rule, 2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2018-04-04 and 2022-06-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633

Line of Evidence (LOE) for Decision ID 161805, Zinc	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337803

Pollutant:

Zinc

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:

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The Water Quality Control Plan for the Lahontan Region Objective for Municipal and Domestic Supply uses of inland surface waters states that waters designated as MUN shall not contain concentrations of chemical constituents in excess of the maximum contaminant level (MCL) or secondary maximum contaminant level (SMCL). This is based upon drinking water standards specified in the following provisions of Title 22 of the California Code of Regulations which are incorporated by reference into the Water Quality Control Plan: Table 64431-A of Section 64431 (Inorganic Chemicals), Table 64431-B of Section 64431 (Fluoride), Table 64444-A of Section 64444 (Organic Chemicals), Table 64449-A of Section 64449 (Secondary Maximum Contaminant Levels-Ranges). The maximum contaminant level listed in Table 64449-A for Zinc is 5 mg/L.

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2018-04-04 and 2022-06-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633

Line of Evidence (LOE) for Decision ID 161805, Zinc	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337798

Pollutant:

Zinc

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2018-04-04 and 2022-06-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633

Line of Evidence (LOE) for Decision ID 161805, Zinc	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

99054

Pollutant:

Zinc

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:

Data Reference:

Water quality data for federal, state, and tribal agencies submitted through the US EPA STorage and RETrival (STORET) database for the 2018 listing cycle.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site(s) (21NEV1_WQX-NV09-301-EF-001)

Temporal Representation:

The samples were collected between the dates of 2012-08-07 and 2012-08-07

Environmental Conditions:

QAPP Information:

QAPP not required for federal data

QAPP Information Reference(s):

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


DECISION ID	161794	Region 6
East Walker River, below Bridgeport Reservoir

Pollutant:	pH
Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)(2018)
Revision Status	Revised
Impairment from Pollutant or Pollution:	Pollutant

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

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

State Board Review of Regional Board Conclusion and Recommendation:

State Board Decision Recommendation:	After review of 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 161794, pH	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

129694

Pollutant:

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

None

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

0 of 0 samples exceeded the water quality standard for pH. Although pH data does exist for this waterbody, the objective for this pollutant requires background information that is currently unavailable, and therefore an assessment of water quality standards could not be made.

Data Reference:

Water Quality Assessment Data for the 2018 solicitation cycle submitted through CEDEN for the SWAMP RWB6 Monitoring (tissue and water).

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

The Lahontan Basin Plan's regionwide objective for pH states: \In fresh waters with designated beneficial uses of COLD or WARM, changes in normal ambient pH levels shall not exceed 0.5 pH units. For all other waters of the region, the pH shall not be depressed below 6.5 nor raised above 8.5 units. The Regional Board recognizes that some waters of the Region may have natural pH levels outside of the 6.5 to 8.5 range. Compliance with the pH objective for these waters will be determined on a case-by-case basis.\""

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site(s) (630EWK001)

Temporal Representation:

The samples were collected between the dates of 2010-09-13 and 2015-10-15

Environmental Conditions:

QAPP Information:

Quality Assurance Program Plan and Standard Operating Procedures for SWAMP program

QAPP Information Reference(s):

Quality Assurance Program Plans, Quality Assurance Project Plans, and Standard Operating Procedures for the SWAMP program

Line of Evidence (LOE) for Decision ID 161794, pH	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

129853

Pollutant:

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

None

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:

Water quality data for federal, state, and tribal agencies submitted through the US EPA STorage and RETrival (STORET) database for the 2018 listing cycle.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site(s) (21NEV1_WQX-NV09-301-EF-001)

Temporal Representation:

The samples were collected between the dates of 2011-03-09 and 2012-08-07

Environmental Conditions:

QAPP Information:

QAPP not required for federal data

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 161794, pH	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

129743

Pollutant:

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

None

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

Water Quality Assessment Data for the 2018 solicitation cycle submitted through CEDEN for the SWAMP RWB6 Monitoring (tissue and water).

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site(s) (630EWK001)

Temporal Representation:

The samples were collected between the dates of 2010-09-13 and 2015-10-15

Environmental Conditions:

QAPP Information:

Quality Assurance Program Plan and Standard Operating Procedures for SWAMP program

QAPP Information Reference(s):

Quality Assurance Program Plans, Quality Assurance Project Plans, and Standard Operating Procedures for the SWAMP program

Line of Evidence (LOE) for Decision ID 161794, pH	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

129861

Pollutant:

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

None

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

Water quality data for federal, state, and tribal agencies submitted through the US EPA STorage and RETrival (STORET) database for the 2018 listing cycle.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site(s) (21NEV1_WQX-NV09-301-EF-001)

Temporal Representation:

The samples were collected between the dates of 2011-03-09 and 2012-08-07

Environmental Conditions:

QAPP Information:

QAPP not required for federal data

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 161794, pH	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

339606

Pollutant:

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

None

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 SWAMP Perennial Stream Surveys data for East Walker River, below Bridgeport Reservoir to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for pH. The objective for this pollutant requires background information that is currently unavailable, and therefore an assessment of water quality thresholds could not be made.

Data Reference:

Benthic, Field, Habitat, WQ from the Surface Water Ambient Monitoring Program for the 2026 Integrated Report in Region 6

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

The Lahontan Basin Plan's regionwide objective for pH states: 'In fresh waters with designated beneficial uses of COLD or WARM, changes in normal ambient pH levels shall not exceed 0.5 pH units. For all other waters of the region, the pH shall not be depressed below 6.5 nor raised above 8.5 units. The Regional Board recognizes that some waters of the Region may have natural pH levels outside of the 6.5 to 8.5 range. Compliance with the pH objective for these waters will be determined on a case-by-case basis.'

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 630PS0163 (East Walker River ~1mi below Murphy Pond).

Temporal Representation:

The samples were collected between the dates of 2015-06-15 and 2015-06-15

Environmental Conditions:

QAPP Information:

Generic SWAMP QAPrP

QAPP Information Reference(s):

Benthic, Field, Habitat, Tissue, Toxicity, WQ from the Surface Water Ambient Monitoring Program for the 2026 Integrated Report in Region 6

Line of Evidence (LOE) for Decision ID 161794, pH	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

339626

Pollutant:

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

None

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 SWAMP RWB6 Monitoring data for East Walker River, below Bridgeport Reservoir to determine beneficial use support and results are as follows: 0 of 20 samples exceeded the water quality threshold for pH. The objective for this pollutant requires background information that is currently unavailable, and therefore an assessment of water quality thresholds could not be made.

Data Reference:

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 630EWK001 (East Walker River, at CA/NV state line).

Temporal Representation:

The samples were collected between the dates of 2016-03-17 and 2022-06-01

Environmental Conditions:

QAPP Information:

Generic SWAMP QAPrP

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 161794, pH	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

33342

Pollutant:

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

None

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

There were 5 samples with pH ranging from 7.7 to 9.5. The normal ambient pH level for this water body is unknown and so it is unknown whether any exceedences occured.

Data Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

The applicable objective states: "In fresh waters with designated beneficial uses of COLD or WARM, changes in normal ambient pH levels shall not exceed 0.5 pH units." (Lahontan Basin Plan).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

Data were collected at the following station: 630EWK001 (East Walker River, at CA/NV state line).

Temporal Representation:

Samples were collected between August and December 2007

Environmental Conditions:

QAPP Information:

2002 QAMP (Quality Assurance Management Plan) for the State of California's Surface Water Ambient Monitoring Program

QAPP Information Reference(s):

Quality Assurance Management Plan for the State of California's Surface Water Ambient Monitoring Program. Sacramento, CA. State Water Resources Control Board. SWAMP. December 2002 (1st version)

Line of Evidence (LOE) for Decision ID 161794, pH	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

339730

Pollutant:

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

None

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

Benthic, Field, Habitat, WQ from the Surface Water Ambient Monitoring Program for the 2026 Integrated Report in Region 6

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 630PS0163 (East Walker River ~1mi below Murphy Pond).

Temporal Representation:

The samples were collected between the dates of 2015-06-15 and 2015-06-15

Environmental Conditions:

QAPP Information:

Generic SWAMP QAPrP

QAPP Information Reference(s):

Benthic, Field, Habitat, Tissue, Toxicity, WQ from the Surface Water Ambient Monitoring Program for the 2026 Integrated Report in Region 6

Line of Evidence (LOE) for Decision ID 161794, pH	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

339588

Pollutant:

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

None

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 630EWK001 (East Walker River, at CA/NV state line).

Temporal Representation:

The samples were collected between the dates of 2016-03-17 and 2022-06-01

Environmental Conditions:

QAPP Information:

Generic SWAMP QAPrP

QAPP Information Reference(s):

WQX from the NWQMP for the 2026 Integrated Report in Region 6

Line of Evidence (LOE) for Decision ID 161794, pH	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337717

Pollutant:

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

None

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 Nevada Division of Environmental Protection data for East Walker River, below Bridgeport Reservoir to determine beneficial use support and results are as follows: 0 of 9 samples exceeded the water quality threshold for pH. The objective for this pollutant requires background information that is currently unavailable, and therefore an assessment of water quality thresholds could not be made.

Data Reference:

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2018-01-10 and 2022-06-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633

Line of Evidence (LOE) for Decision ID 161794, pH	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

348131

Pollutant:

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

None

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed 2007 RWB6 SWAMP East Walker River HU data for East Walker River, below Bridgeport Reservoir to determine beneficial use support and results are as follows: 0 of 15 samples exceeded the water quality threshold for pH. The objective for this pollutant requires background information that is currently unavailable, and therefore an assessment of water quality thresholds could not be made.

Data Reference:

2007. SWAMP Data for the West Walker River and East Walker River Hydrologic Units

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 630EWK001 (East Walker River at the California-Nevada State Line).

Temporal Representation:

The samples were collected between the dates of 2001-08-16 and 2005-08-24

Environmental Conditions:

QAPP Information:

Data meet the quality assurance requirements of the SWAMP QAPP.

QAPP Information Reference(s):

Quality Assurance Program Plans, Quality Assurance Project Plans, and Standard Operating Procedures for the SWAMP program

Line of Evidence (LOE) for Decision ID 161794, pH	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

348130

Pollutant:

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

None

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:

2007. SWAMP Data for the West Walker River and East Walker River Hydrologic Units

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 630EWK001 (East Walker River at the California-Nevada State Line).

Temporal Representation:

The samples were collected between the dates of 2001-08-16 and 2005-08-24

Environmental Conditions:

QAPP Information:

Data meet the quality assurance requirements of the SWAMP QAPP.

QAPP Information Reference(s):

Quality Assurance Program Plans, Quality Assurance Project Plans, and Standard Operating Procedures for the SWAMP program

Line of Evidence (LOE) for Decision ID 161794, pH	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337715

Pollutant:

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

None

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2018-01-10 and 2022-06-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633


DECISION ID	161778	Region 6
East Walker River, below Bridgeport Reservoir

Pollutant:	Iron
Final Listing Decision:	List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)(2018)
Revision Status	Revised
Sources:	A Source Unknown
TMDL Priority:	Low
Impairment from Pollutant or Pollution:	Pollutant

Regional Board Conclusion:	This pollutant is being considered for placement on the CWA section 303(d) List under section 3.1 of the Listing Policy. Under section 3.1 a single line of evidence is necessary to assess listing status. Fourteen lines of evidence are available in the administrative record to assess this pollutant. 0 of the 28 samples exceed the evaluation guideline for COLD. 6 of 28 samples exceed the MUN water quality objective (MCL). 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. 6 of 28 samples exceed the MUN water quality objective (MCL). 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 161778, Iron	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

98557

Pollutant:

Iron

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

Water Quality Assessment Data for the 2018 solicitation cycle submitted through CEDEN for the SWAMP RWB6 Monitoring (tissue and water).

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site(s) (630EWK001)

Temporal Representation:

The samples were collected between the dates of 2010-10-22 and 2011-07-07

Environmental Conditions:

QAPP Information:

Quality Assurance Program Plan and Standard Operating Procedures for SWAMP program

QAPP Information Reference(s):

Quality Assurance Program Plans, Quality Assurance Project Plans, and Standard Operating Procedures for the SWAMP program

Line of Evidence (LOE) for Decision ID 161778, Iron	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

44286

Pollutant:

Iron

LOE Subgroup:

Pollutant-Water

Matrix:

Water

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 SWAMP data for East Walker River, below Bridgeport Reservoir to determine beneficial use support and results are as follows: 0 of 2 samples exceed the criterion for Iron.

Data Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Evaluation Guideline:

The Red Book states that based on field observations principally, a criterion of 1.0 mg/L iron for freshwater aquatic life is believed to be adequately protective (National Recommended Water Quality Criteria 2009).

Guideline Reference:

Spatial Representation:

Data for this line of evidence for East Walker River, below Bridgeport Reservoir was collected at 1 monitoring site [ East Walker River, at CA/NV state line]

Temporal Representation:

Data was collected over the time period 8/14/2007-11/8/2007.

Environmental Conditions:

Staff is not aware of any special conditions that might affect interpretation of the data.

QAPP Information:

2002 QAMP (Quality Assurance Management Plan) for the State of California's Surface Water Ambient Monitoring Program

QAPP Information Reference(s):

Quality Assurance Management Plan for the State of California's Surface Water Ambient Monitoring Program. Sacramento, CA. State Water Resources Control Board. SWAMP. December 2002 (1st version)

Line of Evidence (LOE) for Decision ID 161778, Iron	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

99004

Pollutant:

Iron

LOE Subgroup:

Pollutant-Water

Matrix:

Water

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:

Water quality data for federal, state, and tribal agencies submitted through the US EPA STorage and RETrival (STORET) database for the 2018 listing cycle.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

The Red Book states that based on field observations principally, a criterion of 1.0 mg/L iron for freshwater aquatic life is believed to be adequately protective.

Guideline Reference:

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

Spatial Representation:

The samples were collected at 1 monitoring site(s) (21NEV1_WQX-NV09-301-EF-001)

Temporal Representation:

The samples were collected between the dates of 2011-03-09 and 2012-08-07

Environmental Conditions:

QAPP Information:

QAPP not required for federal data

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 161778, Iron	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

5081

Pollutant:

Iron

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

Fixed station physical/chemical (conventional plus toxic pollutants)

Data Used to Assess Water Quality:

The U.S. Geological survey sampled iron under the Region 6 SWAMP program in 2001 and 2002. Total recoverable iron concentrations in 4 samples ranged from 210 to 260 ug/L. The MCL was not violated.

Data Reference:

2007. SWAMP Data for the West Walker River and East Walker River Hydrologic Units

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

California Maximum Contaminant Levels apply to ambient waters under the Lahontan Basin Plan's "Chemical Constituents" objective. The secondary MCL for iron is 300 ug/L.

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

One station, East Walker River at the California-Nevada State Line, was sampled.

Temporal Representation:

Four quarterly samples were collected in 2001 and 2002.

Environmental Conditions:

QAPP Information:

Data meet the quality assurance requirements of the SWAMP QAPP.

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 161778, Iron	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

44287

Pollutant:

Iron

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed SWAMP data for East Walker River, below Bridgeport Reservoir to determine beneficial use support and results are as follows: 0 of 2 samples exceed the criterion for Iron.

Data Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

The Water Quality Control Plan for the Lahontan Region's Objective for Municipal and Domestic Supply uses of inland surface waters states that waters designated as MUN shall not contain concentrations of chemical constituents in excess of the maximum contaminant level (MCL) or secondary maximum contaminant level (SMCL). This is based upon drinking water standards specified in the following provisions of Title 22 of the California Code of Regulations which are incorporated by reference into the Water Quality Control Plan: Table 64431-A of Section 64431 (Inorganic Chemicals), Table 64431-B of Section 64431 (Fluoride), Table 64444-A of Section 64444 (Organic Chemicals), Table 64449-A of Section 64449 (Secondary Maximum Contaminant Levels-Ranges). The maximum contaminant level listed in Table 64449-A for Iron is 0.3 mg/L.

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

Data for this line of evidence for East Walker River, below Bridgeport Reservoir was collected at 1 monitoring site [ East Walker River, at CA/NV state line]

Temporal Representation:

Data was collected over the time period 8/14/2007-11/8/2007.

Environmental Conditions:

Staff is not aware of any special conditions that might affect interpretation of the data.

QAPP Information:

2002 QAMP (Quality Assurance Management Plan) for the State of California's Surface Water Ambient Monitoring Program

QAPP Information Reference(s):

Quality Assurance Management Plan for the State of California's Surface Water Ambient Monitoring Program. Sacramento, CA. State Water Resources Control Board. SWAMP. December 2002 (1st version)

Line of Evidence (LOE) for Decision ID 161778, Iron	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

99006

Pollutant:

Iron

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:

Data Reference:

Water quality data for federal, state, and tribal agencies submitted through the US EPA STorage and RETrival (STORET) database for the 2018 listing cycle.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The Water Quality Control Plan for the Lahontan Region¦s Objective for Municipal and Domestic Supply uses of inland surface waters states that waters designated as MUN shall not contain concentrations of chemical constituents in excess of the maximum contaminant level (MCL) or secondary maximum contaminant level (SMCL). This is based upon drinking water standards specified in the following provisions of Title 22 of the California Code of Regulations which are incorporated by reference into the Water Quality Control Plan: Table 64431-A of Section 64431 (Inorganic Chemicals), Table 64431-B of Section 64431 (Fluoride), Table 64444-A of Section 64444 (Organic Chemicals), Table 64449-A of Section 64449 (Secondary Maximum Contaminant Levels-Ranges). The maximum contaminant level listed in Table 64449-A for Iron is 0.3 mg/L.

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site(s) (21NEV1_WQX-NV09-301-EF-001)

Temporal Representation:

The samples were collected between the dates of 2011-03-09 and 2012-08-07

Environmental Conditions:

QAPP Information:

QAPP not required for federal data

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 161778, Iron	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

341384

Pollutant:

Iron

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:

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The Water Quality Control Plan for the Lahontan Regions Objective for Municipal and Domestic Supply uses of inland surface waters states that waters designated as MUN shall not contain concentrations of chemical constituents in excess of the maximum contaminant level (MCL) or secondary maximum contaminant level (SMCL). This is based upon drinking water standards specified in the following provisions of Title 22 of the California Code of Regulations which are incorporated by reference into the Water Quality Control Plan: Table 64431-A of Section 64431 (Inorganic Chemicals), Table 64431-B of Section 64431 (Fluoride), Table 64444-A of Section 64444 (Organic Chemicals), Table 64449-A of Section 64449 (Secondary Maximum Contaminant Levels-Ranges). The maximum contaminant level listed in Table 64449-A for Iron is 0.3 mg/L.

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2014-05-12 and 2017-10-03

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633

Line of Evidence (LOE) for Decision ID 161778, Iron	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337621

Pollutant:

Iron

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:

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2018-04-04 and 2022-06-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633

Line of Evidence (LOE) for Decision ID 161778, Iron	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337620

Pollutant:

Iron

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2020-12-02 and 2022-06-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633

Line of Evidence (LOE) for Decision ID 161778, Iron	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337627

Pollutant:

Iron

LOE Subgroup:

Pollutant-Water

Matrix:

Water

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:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

The Red Book states that based on field observations principally, a criterion of 1.0 mg/L iron for freshwater aquatic life is believed to be adequately protective.

Guideline Reference:

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

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2018-04-04 and 2022-06-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633

Line of Evidence (LOE) for Decision ID 161778, Iron	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

341364

Pollutant:

Iron

LOE Subgroup:

Pollutant-Water

Matrix:

Water

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:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

The Red Book states that based on field observations principally, a criterion of 1.0 mg/L iron for freshwater aquatic life is believed to be adequately protective.

Guideline Reference:

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

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2014-05-12 and 2017-10-03

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633

Line of Evidence (LOE) for Decision ID 161778, Iron	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

337625

Pollutant:

Iron

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

The Red Book states that based on field observations principally, a criterion of 1.0 mg/L iron for freshwater aquatic life is believed to be adequately protective.

Guideline Reference:

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

Spatial Representation:

The samples were collected at 1 monitoring site: 21NEV1_WQX-NV09-301-EF-001 (East Fork Walker River @ Stateline).

Temporal Representation:

The samples were collected between the dates of 2020-12-02 and 2022-06-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633

Line of Evidence (LOE) for Decision ID 161778, Iron	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

7710

Pollutant:

Iron

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

Fixed station physical/chemical (conventional plus toxic pollutants)

Data Used to Assess Water Quality:

The U.S. Geological Survey sampled iron under the Region 6 SWAMP program in 2001 and 2002. Dissolved iron concentrations in two of four samples were estimated values. Dissolved iron concentrations in the remaining samples were samples 29 and 71 ug/L. The criterion was not violated.

Data Reference:

2007. SWAMP Data for the West Walker River and East Walker River Hydrologic Units

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

The U.S. Environmental Protection Agency's national freshwater aquatic life criterion for iron is a 4-day average of 1000 ug/L.

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

One station, East Walker River at the California-Nevada State Line, was sampled.

Temporal Representation:

Four quarterly samples were collected in 2001 and 2002.

Environmental Conditions:

QAPP Information:

Data meet the quality assurance requirements of the SWAMP QAPP.

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 161778, Iron	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

98711

Pollutant:

Iron

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

Water Quality Assessment Data for the 2018 solicitation cycle submitted through CEDEN for the SWAMP RWB6 Monitoring (tissue and water).

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

The Red Book states that based on field observations principally, a criterion of 1.0 mg/L iron for freshwater aquatic life is believed to be adequately protective.

Guideline Reference:

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

Spatial Representation:

The samples were collected at 1 monitoring site(s) (630EWK001)

Temporal Representation:

The samples were collected between the dates of 2010-10-22 and 2011-07-07

Environmental Conditions:

QAPP Information:

Quality Assurance Program Plan and Standard Operating Procedures for SWAMP program

QAPP Information Reference(s):

Quality Assurance Program Plans, Quality Assurance Project Plans, and Standard Operating Procedures for the SWAMP program


DECISION ID	163606	Region 6
East Walker River, below Bridgeport Reservoir

Pollutant:	Total Dissolved Solids
Final Listing Decision:	List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)(2018)
Revision Status	Revised
Sources:	A Source Unknown
TMDL Priority:	Low
Impairment from Pollutant or Pollution:	Pollutant

Regional Board Conclusion:	This pollutant is being considered for placement on the CWA section 303(d) List under section 3.2 of the Listing Policy. Under section 3.2 a single line of evidence is necessary to assess listing status. 10 lines of evidence are available in the administrative record to assess this pollutant. Zero of 15 samples exceed the MUN water quality objective and 11 of 31 samples exceed the site-specific objective for total dissolved solids. 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. 11 of 31 samples exceed the site-specific objective for total dissolved solids and this exceeds the allowable frequency listed in Table 3.2 of the Listing Policy. 4. Pursuant to section 3.11 of the Listing Policy, no additional data and information are available indicating that standards are 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 163606, Total Dissolved Solids	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

96961

Pollutant:

Total Dissolved Solids

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

None

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 were collected by the Nevada Department of Environmental Protection at one site on the East Fork Walker River at the state line (21NEV1_WQX-NV09-301-EF-001) between 2011 and 2013. Concentrations in the raw data ranged from 89 to 165 mg/L. Three annual averages were computed and one of them exceeded the water quality objective.

Data Reference:

Water quality data for federal, state, and tribal agencies submitted through the US EPA STorage and RETrival (STORET) database for the 2018 listing cycle.

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

The site specific objective for total nitrogen in the East Walker River, as referenced in the Lahontan Basin Plan table 3-15, is an annual average concentration not to exceed 145 mg/L. While this objective is written to apply to waters upstream of Bridgeport Reservoir, it is being used to assess the waters downstream of the reservoir in recognition of the East Walker River as an interstate water which provides critical water resources to western Nevada.

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

Data were collected by the Nevada Department of Environmental Protection from one location (21NEV1_WQX-NV09-301-EF-001) located near the CA/NV state boundary.

Temporal Representation:

Data were collected between March 2011 and October 2013 on an irregular basis.

Environmental Conditions:

QAPP Information:

These are data from the US EPA STorage and RETrival (STORET) database that do not require a QAPP.

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 163606, Total Dissolved Solids	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

5053

Pollutant:

Total Dissolved Solids

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total Dissolved

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

Fixed station physical/chemical (conventional plus toxic pollutants)

Data Used to Assess Water Quality:

The U.S. Geological Survey sampled TDS under the Region 6 SWAMP program at quarterly intervals between 2001 and 2005. Two different laboratory methods were used. TDS concentrations in 15 individual samples analyzed as "residue" ranged from 90 to 186 mg/L. Of two additional samples analyzed as "nonfilterable" , one was below detection level and the other was 11 mg/L. (The "residue" TDS concentration on the same date was 121 mg/L.) There were no violations of the annual average objective in five years of sampling.

Data Reference:

2007. SWAMP Data for the West Walker River and East Walker River Hydrologic Units

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

The site-specific objective for Total Dissolved Solids (TDS) includes an annual average of 45 mg/L and a 90th percentile value of 160 mg/L (Lahontan Basin Plan Table 3-15).

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

One station, East Walker River at the California-Nevada State Line, was sampled.

Temporal Representation:

Fifteen TDS samples analyzed as "residue" were collected between 2001 and 2005. Two additional samples collected in 2003 and 2004 were analyzed as "nonfilterable."

Environmental Conditions:

QAPP Information:

Data meet the quality assurance requirements of the SWAMP QAPP.

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 163606, Total Dissolved Solids	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

5054

Pollutant:

Total Dissolved Solids

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total Dissolved

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

Fixed station physical/chemical (conventional plus toxic pollutants)

Data Used to Assess Water Quality:

The U.S. Geological Survey sampled TDS under the Region 6 SWAMP program, at quarterly intervals between 2001 and 2005. TDS concentrations in 15 samples analyzed as "residue" ranged from 90 to 186 mg/L. One of two additional samples analyzed as "nonfilterable" had a TDS concentration below detection level; the other sample had a concentration of 11 mg/L. The MCL was not violated.

Data Reference:

2007. SWAMP Data for the West Walker River and East Walker River Hydrologic Units

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

California Maximum Contaminant Levels (MCLs) apply to ambient surface waters under the Lahontan Basin Plan's "Chemical Constituents" objective. The MCL for Total Dissolved Solids (TDS) is 500 mg/L.

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

One station, East Walker River at the California-Nevada State Line, was sampled.

Temporal Representation:

Fifteen TDS samples analyzed as "residue" were collected quarterly between 2001 and 2005. Two additional samples analyzed as "nonfilterable" were collected in 2003 and 2004..

Environmental Conditions:

QAPP Information:

Data meet the quality assurance requirements of the SWAMP QAPP.

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 163606, Total Dissolved Solids	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

96867

Pollutant:

Total Dissolved Solids

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data were collected by Lahontan staff for the Surface Water Ambient Monitoring Program (SWAMP) RWB6 Monitoring program, and for a supplemental TMDL Integrated Report Special Study. The TMDL Special Study was developed by Lahontan Planning and SWAMP staff to provide additional data to the quarterly SWAMP monitoring. The purpose was to gain a better temporal understanding of levels of specific pollutants in the waterbody. To ensure the two datasets could be viably analyzed as one, the TMDL Special Study followed the same sampling protocol as SWAMP. Accordingly, the two datasets have been combined for this assessment to reflect the intended design and to best characterize conditions in the watershed. Data for the projects were collected between September 2010 and December 2016 from one monitoring location. TDS concentrations ranged from 65 to 233 mg/L.

Data Reference:

Water Quality Assessment Data for the 2018 solicitation cycle submitted through CEDEN for the SWAMP RWB6 Monitoring (tissue and water).

Water Quality Assessment Data for the 2018 solicitation cycle submitted through CEDEN for the TMDL Intergrated Report Special Study.

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

The site specific objective for Total Dissolved Solids (TDS) in the East Walker River, as referenced by the Lahontan Basin Plan table 3-15 and incorporated because of the tributary rule to reflect the interstate nature of the waterbody, is an annual average not to exceed 145 mg/L.

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

Data were collected from one monitoring location, 630EWK001, which is located just upstream of the CA/NV stateline.

Temporal Representation:

Data were collected between September 2010 and December 2016 with predominately a twice-per-quarter frequency. More visits were made to the site in the warmer months compared with winter months.

Environmental Conditions:

The East Walker River is an interstate river, influenced by geothermal springs, agricultural and highway drainage, and releases from Bridgeport Reservoir. Headwater streams originate near the Sierra Nevada crest. The state line is in an area transitional to Great Basin environmental conditions. The segment of the river between Bridgeport Reservoir and the state line supports a trophy brown trout fishery. In addition to the Cold Freshwater Habitat beneficial use, the East Walker River is designated for the Spawning, Reproduction and Development use and the Rare, Threatened or Endangered Species use. The latter designation reflects the watershed's role as habitat for the threatened Lahontan cutthroat trout.

QAPP Information:

Data meet the quality assurance requirements of the SWAMP QAPP.

QAPP Information Reference(s):

Quality Assurance Program Plans, Quality Assurance Project Plans, and Standard Operating Procedures for the SWAMP program

Line of Evidence (LOE) for Decision ID 163606, Total Dissolved Solids	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

343373

Pollutant:

Total Dissolved Solids

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

None

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 SWAMP RWB6 Monitoring data to determine beneficial use support and results are as follows:
1 of 3 samples exceeded the water quality threshold for Total Dissolved Solids

Data Reference:

Benthic, Field, Habitat, Tissue, Toxicity, WQ from the Surface Water Ambient Monitoring Program for the 2026 Integrated Report in Region 6

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

The Basin Plan objective for Total Dissolved Solids in this water body is 145 (mg/L), (as a Mean).

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: East Walker River, at CA/NV state line (630EWK001)

Temporal Representation:

The samples were collected between the dates of 2018-09-10 and 2020-03-11

Environmental Conditions:

QAPP Information:

Generic SWAMP QAPrP

QAPP Information Reference(s):

WQX from the NWQMP for the 2026 Integrated Report in Region 6

Line of Evidence (LOE) for Decision ID 163606, Total Dissolved Solids	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

343693

Pollutant:

Total Dissolved Solids

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

None

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 Nevada Division of Environmental Protection data to determine beneficial use support and results are as follows:
2 of 4 samples exceeded the water quality threshold for Total Dissolved Solids

Data Reference:

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The Basin Plan objective for Total Dissolved Solids in this water body is 145 (mg/L), (as a Mean).

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: East Fork Walker River @ Stateline (21NEV1_WQX-NV09-301-EF-001)

Temporal Representation:

The samples were collected between the dates of 2014-01-22 and 2017-10-03

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633

Line of Evidence (LOE) for Decision ID 163606, Total Dissolved Solids	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

343385

Pollutant:

Total Dissolved Solids

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

None

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 SWAMP RWB6 Monitoring data to determine beneficial use support and results are as follows:
2 of 3 samples exceeded the water quality threshold for Total Dissolved Solids

Data Reference:

Benthic, Field, Habitat, Tissue, Toxicity, WQ from the Surface Water Ambient Monitoring Program for the 2026 Integrated Report in Region 6

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

The Basin Plan objective for Total Dissolved Solids in this water body is 145 (mg/L), (as a Mean).

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: East Walker River, at CA/NV state line (630EWK001)

Temporal Representation:

The samples were collected between the dates of 2016-03-17 and 2021-11-23

Environmental Conditions:

QAPP Information:

Generic SWAMP QAPrP

QAPP Information Reference(s):

WQX from the NWQMP for the 2026 Integrated Report in Region 6

Line of Evidence (LOE) for Decision ID 163606, Total Dissolved Solids	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

343587

Pollutant:

Total Dissolved Solids

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

None

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:

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The Basin Plan objective for Total Dissolved Solids in this water body is 145 (mg/L), (as a Mean).

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: East Fork Walker River @ Stateline (21NEV1_WQX-NV09-301-EF-001)

Temporal Representation:

The samples were collected between the dates of 2018-01-10 and 2022-06-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633

Line of Evidence (LOE) for Decision ID 163606, Total Dissolved Solids	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

343586

Pollutant:

Total Dissolved Solids

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

None

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:

WQX from the NWQMP for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The Basin Plan objective for Total Dissolved Solids in this water body is 145 (mg/L), (as a Mean).

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: East Fork Walker River @ Stateline (21NEV1_WQX-NV09-301-EF-001)

Temporal Representation:

The samples were collected between the dates of 2018-01-10 and 2022-06-30

Environmental Conditions:

QAPP Information:

Nevada DEP QAPP

QAPP Information Reference(s):

Lahontan Water Board - NevadaDEP_QAPP - Nevada Division of Environmental Protection - 402633

Line of Evidence (LOE) for Decision ID 163606, Total Dissolved Solids	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

343396

Pollutant:

Total Dissolved Solids

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

None

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 TMDL Intergrated Report Special Study data to determine beneficial use support and results are as follows:
0 of 1 samples exceeded the water quality threshold for Total Dissolved Solids

Data Reference:

WQ from the Total Maximum Daily Load for the 2026 Integrated Report in Region 6

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

The Basin Plan objective for Total Dissolved Solids in this water body is 145 (mg/L), (as a Mean).

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: East Walker River, at CA/NV state line (630EWK001)

Temporal Representation:

The samples were collected between the dates of 2017-04-20 and 2017-10-04

Environmental Conditions:

QAPP Information:

Generic SWAMP QAPrP

QAPP Information Reference(s):

2007. SWAMP Data for the West Walker River and East Walker River Hydrologic Units


DECISION ID	69434	Region 6
East Walker River, below Bridgeport Reservoir

Pollutant:	Sedimentation/Siltation
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
TMDL Priority:	Low
Impairment from Pollutant or Pollution:	Pollutant

Regional Board Conclusion:	This pollutant was considered for placement on the section 303(d) list in a previous assessment cycle. No new information was reviewed for this current assessment cycle. Therefore, the previous conclusion remains unchanged, and is as follows: Two lines of evidence are available in the administrative record to assess this pollutant. The original listing was based on best professional judgment regarding a single severe sedimentation incident. Water Board staff did not review quantitative data in connection with the listing. The applicable narrative water quality objective is antidegradation based. The 16 quarterly SWAMP samples are insufficient to establish baseline and trend conditions as required for assessment under Section 4.10 of the Listing Policy. Based on the readily available data and information, the weight of evidence indicates that there is sufficient justification against removing this water segment-pollutant combination from the section 303(d) list. This conclusion is based on the staff findings that: 1. The data used satisfy the data quality requirements of section 6.1.4 of the Policy. 2. The data used do not satisfy the data quantity requirements of section 6.1.5 of the Policy. Quarterly samples do not capture the full range of variability in streamflows and constituent concentrations expected in streams of the Lahontan Region. Flows and concentrations in this segment are also affected by the timing of releases from Bridgeport Reservoir. 3. The quarterly SWAMP data are insufficient to establish baseline and trend conditions as required under Section 4.10 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 met.

Regional Board Decision Recommendation:	This region was not assessed this cycle. All decisions have been carried over from the previous cycle and remain the same.

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 69434, Sedimentation/Siltation	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

5051

Pollutant:

Sediment

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

None

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

Fixed station physical/chemical (conventional plus toxic pollutants)

Data Used to Assess Water Quality:

The U.S. Geological survey sampled suspended sediment under the Region 6 SWAMP program, at quarterly intervals between 2001 and 2005, and did load calculations based on concurrent flows. Suspended sediment concentrations in 16 samples ranged from 5 to 28 mg/L. Calculated sediment loads in 8 samples ranged from 0.37 to 23 tons/day. Sampling frequency is insufficient to evaluate compliance with the objective.

Data Reference:

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

The Lahontan Basin Plan's narrative objective states: ¿The suspended sediment load and suspended sediment discharge rate of surface waters shall not be altered in such a manner as to cause nuisance or adversely affect the water for beneficial uses.¿

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

One station, East Walker River at the California-Nevada State Line, was sampled.

Temporal Representation:

Sixteen quarterly samples were collected between 2001 and 2005.

Environmental Conditions:

QAPP Information:

Data meet the quality assurance requirements of the SWAMP QAPP.

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 69434, Sedimentation/Siltation	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

4609

Pollutant:

Sedimentation/Siltation

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Not Recorded

Beneficial Use:

Cold 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	70138	Region 6
East Walker River, below Bridgeport Reservoir

Pollutant:	Calcium
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 was considered for placement on the section 303(d) list in a previous assessment cycle. No new information was reviewed for this current assessment cycle. Therefore, the previous conclusion remains unchanged, and is as follows: This pollutant is being considered for placement on the section 303(d) list under section 3.2 of the Listing Policy. Under section 3.2 a single line of evidence is necessary to assess listing status. Two of evidence are available in the administrative record to assess this pollutant. There are no California or federal standards or water quality criteria for calcium. 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 satisfy the data quality requirements of section 6.1.4 of the Policy. 2. The data used satisfy the data quantity requirements of section 6.1.5 of the Policy. 3. There are no applicable standards or criteria and the data cannot be assessed pursuant to Table 3.2 of the Listing Policy. 4. Pursuant to section 3.11 of the Listing Policy, no additional data and information are available indicating that standards are not met.

Regional Board Decision Recommendation:	This region was not assessed this cycle. All decisions have been carried over from the previous cycle and remain the same.

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 70138, Calcium	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

7720

Pollutant:

Calcium

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

Fixed station physical/chemical (conventional plus toxic pollutants)

Data Used to Assess Water Quality:

The U.S. Geological Survey sampled the East Walker River under the Region 6 SWAMP program in 2001 and 2002. Concentrations of total calcium in four samples ranged from 16.9 to 18.6 mg/L.

Data Reference:

2007. SWAMP Data for the West Walker River and East Walker River Hydrologic Units

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

There are no state or federal standards or criteria for calcium for the protection of human health.

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

One station, East Walker River at the California-Nevada State Line, was sampled.

Temporal Representation:

Four quarterly samples were collected in 2001 and 2002.

Environmental Conditions:

QAPP Information:

Data meet the quality assurance requirements of the SWAMP QAPP.

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 70138, Calcium	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

7719

Pollutant:

Calcium

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

Fixed station physical/chemical (conventional plus toxic pollutants)

Data Used to Assess Water Quality:

The U.S. Geological Survey sampled the East Walker River under the Region 6 SWAMP program in 2001 and 2002. Concentrations of dissolved calcium in four samples ranged from 17 to 20 mg/L.

Data Reference:

2007. SWAMP Data for the West Walker River and East Walker River Hydrologic Units

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

There are no state or federal standards or criteria for calcium for the protection of freshwater aquatic life.

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

One station, East Walker River at the California-Nevada State Line, was sampled.

Temporal Representation:

Four quarterly samples were collected in 2001 and 2002.

Environmental Conditions:

QAPP Information:

Data meet the quality assurance requirements of the SWAMP QAPP.

QAPP Information Reference(s):


DECISION ID	71428	Region 6
East Walker River, below Bridgeport Reservoir

Pollutant:	Chromium (total)
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 was considered for placement on the section 303(d) list in a previous assessment cycle. No new information was reviewed for this current assessment cycle. Therefore, the previous conclusion remains unchanged, and is as follows: 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. Two lines of evidence are available in the administrative record to assess this pollutant. None 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 satisfy the data quality requirements of section 6.1.4 of the Policy. 2. The data used do not satisfy the data quantity requirements of section 6.1.5 of the Policy. Quarterly samples do not capture the seasonal and annual variability expected in streamflows and constituent concentrations in streams of the Lahontan Region. 3. None of four samples exceeded the Califoria Toxics Rule standards or the Maximum Contaminant Level 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 region was not assessed this cycle. All decisions have been carried over from the previous cycle and remain the same.

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 71428, Chromium (total)	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

5748

Pollutant:

Chromium (total)

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

Fixed station physical/chemical (conventional plus toxic pollutants)

Data Used to Assess Water Quality:

The USGS sampled the East Walker River under the Region 6 SWAMP program. Concentrations of total chromium in four quarterly samples were all below the detection level. Under Listing Policy section 6.1.5.5 the MCL is presumed to be attained.

Data Reference:

2007. SWAMP Data for the West Walker River and East Walker River Hydrologic Units

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

California Maximum Contaminant Levels (MCLs) apply to ambient waters under the Lahontan Basin Plan's "Chemical Constituents" objective. The MCL for chromium is 50 ug/L.

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

One station, East Walker River at the California-Nevada State Line, was sampled.

Temporal Representation:

Four quarterly samples were collected in 2001 and 2002.

Environmental Conditions:

QAPP Information:

Data meet the quality assurance requirements of the SWAMP QAPP.

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 71428, Chromium (total)	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

7695

Pollutant:

Chromium (total)

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

Fixed station physical/chemical (conventional plus toxic pollutants)

Data Used to Assess Water Quality:

The USGS sampled the East Walker River under the Region 6 SWAMP program. Concentrations of dissolved chromium in four quarterly samples were all below the detection level. Under Listing Policy section 6.1.5.5 the standards are presumed to be attained.

Data Reference:

2007. SWAMP Data for the West Walker River and East Walker River Hydrologic Units

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

The California Toxics Rule (CTR) standards for dissolved Chromium VI to protect freshwater aquatic life are11 ug/L ( 4-day average) and,16 ug/L (1 hour average). The CTR standard for Chromium III is hardness dependent. At the hardness levels reported for this station, acute (1 hour average) limits for Chromium III range from 349.71 to 398.82 ug/L. The chronic (4 day average) limits range from 113.41 to 129.37 ug/L.

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

One station, East Walker River at the California-Nevada State Line, was sampled.

Temporal Representation:

Four quarterly samples were collected in 2001 and 2002.

Environmental Conditions:

QAPP Information:

Data meet the quality assurance requirements of the SWAMP QAPP.

QAPP Information Reference(s):


DECISION ID	70688	Region 6
East Walker River, below Bridgeport Reservoir

Pollutant:	Hardness as CaCO3
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 was considered for placement on the section 303(d) list in a previous assessment cycle. No new information was reviewed for this current assessment cycle. Therefore, the previous conclusion remains unchanged, and is as follows: This pollutant is being considered for placement on the section 303(d) list under section 3.2 of the Listing Policy. Under section 3.2 a single line of evidence is necessary to assess listing status. Two lines of evidence are available in the administrative record to assess this pollutant. There are no applicable state or federal standards or criteria. The hardness data assessed fall within the category generally considered "soft". 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 do not satisfy the data quantity requirements of section 6.1.5 of the Policy in that only four quarterly samples were available. The minimum sample number requirements of Listing Policy Table 3.2 are not met. 3. There are no applicable standards or criteria. 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 region was not assessed this cycle. All decisions have been carried over from the previous cycle and remain the same.

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 70688, Hardness as CaCO3	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

7815

Pollutant:

Hardness as CaCO3

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

None

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

Fixed station physical/chemical (conventional plus toxic pollutants)

Data Used to Assess Water Quality:

The U.S. Geological Survey sampled the East Walker River under the Region 6 SWAMP program in 2001 and 2002. Hardness values in four quarterly samples were 57.69, 67.73, 62.80, and 61.84 mg equivalent CaC03/L. These values are within the range characterizing "soft" water.

Data Reference:

2007. SWAMP Data for the West Walker River and East Walker River Hydrologic Units

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

There are no state or federal standards or criteria for hardness. Hardness is monitored for purposes such as determination of the applicable criteria and standards for metals whose toxicity is hardness-dependent. The U.S. Environmental Protection Agency's 1986 "Gold Book" includes generally accepted categories of hardness. Calcium and magnesium are the major ions contributing to hardness, and hardness is generally expressed as calcium carbonate. Water with a hardness equivalent to 0-75 mg equivalent CaCO3/L is considered "soft."

Objective/Criterion Reference:

Quality Criteria for Water 1986. United States Environmental Protection Agency. Office of Water. Regulations and Standards. Washington D.C. EPA 440/5-86-001.

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

One station, East Walker River at the California-Nevada State Line, was sampled.

Temporal Representation:

Four quarterly samples were collected in 2001 and 2002.

Environmental Conditions:

QAPP Information:

Data meet the quality assurance requirements of the SWAMP QAPP.

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 70688, Hardness as CaCO3	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

7812

Pollutant:

Hardness as CaCO3

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

None

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

Fixed station physical/chemical (conventional plus toxic pollutants)

Data Used to Assess Water Quality:

Data Reference:

2007. SWAMP Data for the West Walker River and East Walker River Hydrologic Units

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Quality Criteria for Water 1986. United States Environmental Protection Agency. Office of Water. Regulations and Standards. Washington D.C. EPA 440/5-86-001.

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

One station, East Walker River at the California-Nevada State Line, was sampled.

Temporal Representation:

Four quarterly samples were collected in 2001 and 2002.

Environmental Conditions:

QAPP Information:

Data meet the quality assurance requirements of the SWAMP QAPP.

QAPP Information Reference(s):


DECISION ID	70960	Region 6
East Walker River, below Bridgeport Reservoir

Pollutant:	Magnesium
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 was considered for placement on the section 303(d) list in a previous assessment cycle. No new information was reviewed for this current assessment cycle. Therefore, the previous conclusion remains unchanged, and is as follows: This pollutant is being considered for placement on the section 303(d) list under section 3.2 of the Listing Policy. Under section 3.2 a single line of evidence is necessary to assess listing status. Two lines of evidence are available in the administrative record to assess this pollutant. There are no applicable standards, objectives or criteria for magnesium. 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 satisfy the data quality requirements of section 6.1.4 of the Policy. 2. The data used do not satisfy the data quantity requirements of section 6.1.5 of the Policy. 3. There are no applicable standards, objectives or criteria for evaluation of the four samples for dissolved magnesium or four samples for total magnesium 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 region was not assessed this cycle. All decisions have been carried over from the previous cycle and remain the same.

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 70960, Magnesium	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

7721

Pollutant:

Magnesium

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

Fixed station physical/chemical (conventional plus toxic pollutants)

Data Used to Assess Water Quality:

The U.S. Geological Survey sampled the East Walker River under the Region 6 SWAMP program in 2001 and 2002. Concentrations of dissolved magnesium in four samples ranged from 3.7 to 4.32 mg/L.

Data Reference:

2007. SWAMP Data for the West Walker River and East Walker River Hydrologic Units

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

There are no state or federal standards or criteria for magnesium for the protection of freshwater aquatic life.

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

One station, East Walker River at the California-Nevada State Line, was sampled.

Temporal Representation:

Four quarterly samples were collected in 2001 and 2002.

Environmental Conditions:

QAPP Information:

Data meet the quality assurance requirements of the SWAMP QAPP.

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 70960, Magnesium	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

7722

Pollutant:

Magnesium

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

Fixed station physical/chemical (conventional plus toxic pollutants)

Data Used to Assess Water Quality:

The U.S. Geological Survey sampled the East Walker River under the Region 6 SWAMP program in 2001 and 2002. Concentrations of total magnesium in four samples ranged from 3.64 to 4.09 mg/L.

Data Reference:

2007. SWAMP Data for the West Walker River and East Walker River Hydrologic Units

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

There are no state or federal standards or criteria for magnesium for the protection of human health.

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

One station, East Walker River at the California-Nevada State Line, was sampled.

Temporal Representation:

Four quarterly samples were collected in 2001 and 2002.

Environmental Conditions:

QAPP Information:

Data meet the quality assurance requirements of the SWAMP QAPP.

QAPP Information Reference(s):


DECISION ID	76096	Region 6
East Walker River, below Bridgeport Reservoir

Pollutant:	Phosphate
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 was considered for placement on the section 303(d) list in a previous assessment cycle. No new information was reviewed for this current assessment cycle. Therefore, the previous conclusion remains unchanged, and is as follows: 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. No biological data are available to evaluate whether any of the samples exceeds 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 satisfy the data quality requirements of section 6.1.4 of the Policy. 2. The data used do not satisfy the data quantity requirements of section 6.1.5 of the Policy. Quarterly samples do not capture the full range of seasonal and annual variability expected in streamflows and constituent concentrations in streams of the Lahontan Region. 3. No biological data are available for assessment of compliance with the water quality objective and the data cannot be assessed using 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 region was not assessed this cycle. All decisions have been carried over from the previous cycle and remain the same.

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 76096, Phosphate	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

7792

Pollutant:

Phosphate

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

Fixed station physical/chemical (conventional plus toxic pollutants)

Data Used to Assess Water Quality:

The U.S. Geological survey sampled the East Walker River under the Region 6 SWAMP program in 2002 and 2003. Concentrations of PO4-P in 3 samples ranged from 0.03 to 1.61 mg/L. No biological data are available for assessment of compliance with the objective for biostimulatory substances.

Data Reference:

2007. SWAMP Data for the West Walker River and East Walker River Hydrologic Units

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

There are no site specific numerical objectives for phosphate for this segment. The regionwide narrative objective for biostimulatory substances states:

"Waters shall not contain biostimulatory substances in concentrations that promote aquatic growths to the extent that such growths cause nuisance or adversely affect the water for beneficial uses."

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

One station, East Walker River at the California-Nevada State Line, was sampled.

Temporal Representation:

Three quarterly samples were collected in 2002 and 2003.

Environmental Conditions:

QAPP Information:

Data meet the quality assurance requirements of the SWAMP QAPP.

QAPP Information Reference(s):


DECISION ID	79007	Region 6
East Walker River, below Bridgeport Reservoir

Pollutant:	Salinity
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 3.2 of the Listing Policy. Under section 3.2 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. None of the five 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. None of the five samples exceeded the site specific objective for TDS of 145 mg/L which is used to assess the salinity data provided in this data set and this sample size is insufficient to determine with the power and confidence of the Listing Policy if standards are not met. A minimum of 26 samples is needed for application of table 3.2. 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 region was not assessed this cycle. All decisions have been carried over from the previous cycle and remain the same.

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 79007, Salinity	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

34506

Pollutant:

Salinity

LOE Subgroup:

Pollutant-Water

Matrix:

Water

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:

None of the 5 samples exceeded the site specific objective of 145 mg/L.

Data Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

The Regional Board will consider site specific adjustments to the objectives for wetlands (bacteria, pH, hardness, salinity, temperature, or other parameters) as necessary on a case-by-case basis. The site specific objective for Total Dissolved Solids at East Walker River, below Bridgeport Reservoir is 145 mg/L and will be used to assess the salinity data provided in this data set.

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

Samples collected from the 630EWK001 station.

Temporal Representation:

Samples collected on the following dates: 10/30/2007 11/8/2007 9/18/2007 8/14/2007 12/26/2007

Environmental Conditions:

QAPP Information:

2002 QAMP (Quality Assurance Management Plan) for the State of California's Surface Water Ambient Monitoring Program

QAPP Information Reference(s):

Quality Assurance Management Plan for the State of California's Surface Water Ambient Monitoring Program. Sacramento, CA. State Water Resources Control Board. SWAMP. December 2002 (1st version)


DECISION ID	79702	Region 6
East Walker River, below Bridgeport Reservoir

Pollutant:	Temperature, water
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 3.2 of the Listing Policy. Under section 3.2 a single line of evidence is necessary to assess listing status. Two lines of evidence are available in the administrative record to assess this pollutant. One of the 21 samples exceed the water quality objective., however, sampling frequency was not sufficient to determine the natural seasonal and annual temperature range or the extent to which changes occur due to human activities such as reservoir management (Bridgeport Reservoir). The Lahontan Basin Plan's narrative temperature objective is an antidegradation-based objective that requires that there be no change in temperature in waters designated for the Cold Freshwater Habitat (COLD) beneficial use. The objective does not include specific numerical limits for protection of the COLD use. Listing Policy Section 3.10 contains directions for assessment based on trends in water quality. These directions include requirements to establish specific baseline conditions and specify the influence of seasonal and interannual effects. There are not enough temperature samples to establish baseline conditions (including diel, seasonal, annual and interannual variations in temperature) or to detect declining trends in the temperature regime if such trends exist. Because temperature samples were collected only quarterly, weekly and monthly average data are not available for comparison with guidelines in the scientific literature for the temperature requirements of sensitive aquatic species such as salmonids, as directed in Listing Policy Section 6.1.5.9. 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 the 21 samples exceeded the objective and this sample size is insufficient to determine with the power and confidence of the Listing Policy if standards are not met. A minimum of 26 samples is needed for application of table 3.2. 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 region was not assessed this cycle. All decisions have been carried over from the previous cycle and remain the same.

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 79702, Temperature, water	Region 6
East Walker River, below Bridgeport Reservoir

LOE ID:

44264

Pollutant:

Temperature, water

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

None

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 SWAMP data for East Walker River, below Bridgeport Reservoir to determine beneficial use support and results are as follows: 1 of 5 samples exceed the criterion for Water Temperature.

Data Reference: