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

Supporting Information

Regional Board 6 - Lahontan Region

Water Body Name:	Oak Creek (Inyo County)
Water Body ID:	CAR6033012020230511031860
Water Body Type:	River & Stream


DECISION ID	162790	Region 6
Oak Creek (Inyo County)

Pollutant:	Arsenic
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 162790, Arsenic	Region 6
Oak Creek (Inyo County)

LOE ID:

341130

Pollutant:

Arsenic

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

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 arsenic criterion continuous concentration (expressed as a 4-day average) to protect aquatic life in freshwater is 150 ug/L. The conversion factor used to convert the total fraction criterion for arsenic to dissolved fraction criterion is 1. Therefore all data was considered to be representative of the dissolved fraction. (California Toxics Rule, 2000)

Objective/Criterion Reference:

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

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: FIIR-Site 1 (OC 1).

Temporal Representation:

The samples were collected between the dates of 2019-07-01 and 2019-07-01

Environmental Conditions:

QAPP Information:

Cedarville Rancheria QAPP

QAPP Information Reference(s):

Data collected by a California Tribe QAPP Approved by U.S. EPA QAPP Reference

Line of Evidence (LOE) for Decision ID 162790, Arsenic	Region 6
Oak Creek (Inyo County)

LOE ID:

341136

Pollutant:

Arsenic

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 arsenic incorporated by reference in the Basin Plan is 0.010 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: FIIR-Site 1 (OC 1).

Temporal Representation:

The samples were collected between the dates of 2019-07-01 and 2019-07-01

Environmental Conditions:

QAPP Information:

Cedarville Rancheria QAPP

QAPP Information Reference(s):

Data collected by a California Tribe QAPP Approved by U.S. EPA QAPP Reference

Line of Evidence (LOE) for Decision ID 162790, Arsenic	Region 6
Oak Creek (Inyo County)

LOE ID:

341137

Pollutant:

Arsenic

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: FIIR-Site 1 (OC 1).

Temporal Representation:

The samples were collected between the dates of 2019-07-01 and 2019-07-01

Environmental Conditions:

QAPP Information:

Cedarville Rancheria QAPP

QAPP Information Reference(s):

Data collected by a California Tribe QAPP Approved by U.S. EPA QAPP Reference


DECISION ID	162800	Region 6
Oak Creek (Inyo County)

Pollutant:	Gasoline
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 162800, Gasoline	Region 6
Oak Creek (Inyo County)

LOE ID:

341327

Pollutant:

Gasoline

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:

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. Waters shall not contain taste or odor-producing substances in concentrations that impart unsdeirable tastes or odors.

Objective/Criterion Reference:

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

Evaluation Guideline:

The threshold odor concentration for refined petroleum products is 5 ug/L. (McKee and Wolf, 1963)

Guideline Reference:

Compilation of Water Quality Goals

Spatial Representation:

The samples were collected at 1 monitoring site: FIIR-Site 1 (OC 1).

Temporal Representation:

The samples were collected between the dates of 2019-07-01 and 2019-07-01

Environmental Conditions:

QAPP Information:

Cedarville Rancheria QAPP

QAPP Information Reference(s):

Data collected by a California Tribe QAPP Approved by U.S. EPA QAPP Reference


DECISION ID	162792	Region 6
Oak Creek (Inyo County)

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:

Line of Evidence (LOE) for Decision ID 162792, Methoxychlor	Region 6
Oak Creek (Inyo County)

LOE ID:

341472

Pollutant:

Methoxychlor

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 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: FIIR-Site 1 (OC 1).

Temporal Representation:

The samples were collected between the dates of 2019-07-01 and 2019-07-01

Environmental Conditions:

QAPP Information:

Cedarville Rancheria QAPP

QAPP Information Reference(s):

Data collected by a California Tribe QAPP Approved by U.S. EPA QAPP Reference

Line of Evidence (LOE) for Decision ID 162792, Methoxychlor	Region 6
Oak Creek (Inyo County)

LOE ID:

341471

Pollutant:

Methoxychlor

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 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: FIIR-Site 1 (OC 1).

Temporal Representation:

The samples were collected between the dates of 2019-07-01 and 2019-07-01

Environmental Conditions:

QAPP Information:

Cedarville Rancheria QAPP

QAPP Information Reference(s):

Data collected by a California Tribe QAPP Approved by U.S. EPA QAPP Reference

Line of Evidence (LOE) for Decision ID 162792, Methoxychlor	Region 6
Oak Creek (Inyo County)

LOE ID:

341473

Pollutant:

Methoxychlor

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Not Recorded

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

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: FIIR-Site 1 (OC 1).

Temporal Representation:

The samples were collected between the dates of 2019-07-01 and 2019-07-01

Environmental Conditions:

QAPP Information:

Cedarville Rancheria QAPP

QAPP Information Reference(s):

Data collected by a California Tribe QAPP Approved by U.S. EPA QAPP Reference


DECISION ID	162793	Region 6
Oak Creek (Inyo County)

Pollutant:	Methyl ethyl ketone (2-Butanone)
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 162793, Methyl ethyl ketone (2-Butanone)	Region 6
Oak Creek (Inyo County)

LOE ID:

341181

Pollutant:

Methyl ethyl ketone (2-Butanone)

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:

USEPA's Drinking Water Health advisory for life-time exposure to Butanone, 2- 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: FIIR-Site 1 (OC 1).

Temporal Representation:

The samples were collected between the dates of 2019-07-01 and 2019-07-01

Environmental Conditions:

QAPP Information:

Cedarville Rancheria QAPP

QAPP Information Reference(s):

Data collected by a California Tribe QAPP Approved by U.S. EPA QAPP Reference


DECISION ID	162801	Region 6
Oak Creek (Inyo County)

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:

Line of Evidence (LOE) for Decision ID 162801, Metolachlor	Region 6
Oak Creek (Inyo County)

LOE ID:

341474

Pollutant:

Metolachlor

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 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: FIIR-Site 1 (OC 1).

Temporal Representation:

The samples were collected between the dates of 2019-07-01 and 2019-07-01

Environmental Conditions:

QAPP Information:

Cedarville Rancheria QAPP

QAPP Information Reference(s):

Data collected by a California Tribe QAPP Approved by U.S. EPA QAPP Reference

Line of Evidence (LOE) for Decision ID 162801, Metolachlor	Region 6
Oak Creek (Inyo County)

LOE ID:

341475

Pollutant:

Metolachlor

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 metolachlor is the USEPA Aquatic Life Benchmark of 8 ug/L for nonvascular plants.

Guideline Reference:

OPP Aquatic Life Benchmarks

Spatial Representation:

The samples were collected at 1 monitoring site: FIIR-Site 1 (OC 1).

Temporal Representation:

The samples were collected between the dates of 2019-07-01 and 2019-07-01

Environmental Conditions:

QAPP Information:

Cedarville Rancheria QAPP

QAPP Information Reference(s):

Data collected by a California Tribe QAPP Approved by U.S. EPA QAPP Reference

Line of Evidence (LOE) for Decision ID 162801, Metolachlor	Region 6
Oak Creek (Inyo County)

LOE ID:

341476

Pollutant:

Metolachlor

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Not Recorded

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

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:

OPP Aquatic Life Benchmarks

Spatial Representation:

The samples were collected at 1 monitoring site: FIIR-Site 1 (OC 1).

Temporal Representation:

The samples were collected between the dates of 2019-07-01 and 2019-07-01

Environmental Conditions:

QAPP Information:

Cedarville Rancheria QAPP

QAPP Information Reference(s):

Data collected by a California Tribe QAPP Approved by U.S. EPA QAPP Reference


DECISION ID	162802	Region 6
Oak Creek (Inyo County)

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:

Line of Evidence (LOE) for Decision ID 162802, Metribuzin	Region 6
Oak Creek (Inyo County)

LOE ID:

341477

Pollutant:

Metribuzin

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 metribuzin is the USEPA Aquatic Life Benchmark of 8.1 ug/L for a nonvascular plant (acute).

Guideline Reference:

OPP Aquatic Life Benchmarks

Spatial Representation:

The samples were collected at 1 monitoring site: FIIR-Site 1 (OC 1).

Temporal Representation:

The samples were collected between the dates of 2019-07-01 and 2019-07-01

Environmental Conditions:

QAPP Information:

Cedarville Rancheria QAPP

QAPP Information Reference(s):

Data collected by a California Tribe QAPP Approved by U.S. EPA QAPP Reference

Line of Evidence (LOE) for Decision ID 162802, Metribuzin	Region 6
Oak Creek (Inyo County)

LOE ID:

341479

Pollutant:

Metribuzin

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Not Recorded

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

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:

OPP Aquatic Life Benchmarks

Spatial Representation:

The samples were collected at 1 monitoring site: FIIR-Site 1 (OC 1).

Temporal Representation:

The samples were collected between the dates of 2019-07-01 and 2019-07-01

Environmental Conditions:

QAPP Information:

Cedarville Rancheria QAPP

QAPP Information Reference(s):

Data collected by a California Tribe QAPP Approved by U.S. EPA QAPP Reference

Line of Evidence (LOE) for Decision ID 162802, Metribuzin	Region 6
Oak Creek (Inyo County)

LOE ID:

341478

Pollutant:

Metribuzin

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 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: FIIR-Site 1 (OC 1).

Temporal Representation:

The samples were collected between the dates of 2019-07-01 and 2019-07-01

Environmental Conditions:

QAPP Information:

Cedarville Rancheria QAPP

QAPP Information Reference(s):

Data collected by a California Tribe QAPP Approved by U.S. EPA QAPP Reference


DECISION ID	162794	Region 6
Oak Creek (Inyo County)

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:

Line of Evidence (LOE) for Decision ID 162794, Molinate	Region 6
Oak Creek (Inyo County)

LOE ID:

341512

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:

OPP Aquatic Life Benchmarks

Spatial Representation:

The samples were collected at 1 monitoring site: FIIR-Site 1 (OC 1).

Temporal Representation:

The samples were collected between the dates of 2019-07-01 and 2019-07-01

Environmental Conditions:

QAPP Information:

Cedarville Rancheria QAPP

QAPP Information Reference(s):

Data collected by a California Tribe QAPP Approved by U.S. EPA QAPP Reference

Line of Evidence (LOE) for Decision ID 162794, Molinate	Region 6
Oak Creek (Inyo County)

LOE ID:

341510

Pollutant:

Molinate

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

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:

OPP Aquatic Life Benchmarks

Spatial Representation:

The samples were collected at 1 monitoring site: FIIR-Site 1 (OC 1).

Temporal Representation:

The samples were collected between the dates of 2019-07-01 and 2019-07-01

Environmental Conditions:

QAPP Information:

Cedarville Rancheria QAPP

QAPP Information Reference(s):

Data collected by a California Tribe QAPP Approved by U.S. EPA QAPP Reference

Line of Evidence (LOE) for Decision ID 162794, Molinate	Region 6
Oak Creek (Inyo County)

LOE ID:

341511

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: FIIR-Site 1 (OC 1).

Temporal Representation:

The samples were collected between the dates of 2019-07-01 and 2019-07-01

Environmental Conditions:

QAPP Information:

Cedarville Rancheria QAPP

QAPP Information Reference(s):

Data collected by a California Tribe QAPP Approved by U.S. EPA QAPP Reference


DECISION ID	162795	Region 6
Oak Creek (Inyo County)

Pollutant:	Oxygen, Dissolved
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. One line of evidence is available in the administrative record to assess this pollutant. One of the 262 samples is below the objective. Based on the readily available data and information, the weight of evidence indicates that there is sufficient justification against placing this water segment-pollutant combination on the CWA section 303(d) List. 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 262 samples is below 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 162795, Oxygen, Dissolved	Region 6
Oak Creek (Inyo County)

LOE ID:

341606

Pollutant:

Oxygen, Dissolved

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

None

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

262

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:

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: FIIR-Site 2 (OC 2).

Temporal Representation:

The samples were collected between the dates of 2018-01-01 and 2018-12-31

Environmental Conditions:

QAPP Information:

Cedarville Rancheria QAPP

QAPP Information Reference(s):

Data collected by a California Tribe QAPP Approved by U.S. EPA QAPP Reference


DECISION ID	162803	Region 6
Oak Creek (Inyo County)

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:

Line of Evidence (LOE) for Decision ID 162803, Propachlor	Region 6
Oak Creek (Inyo County)

LOE ID:

341728

Pollutant:

Propachlor

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 propachlor is the USEPA Aquatic Life Benchmark of 13.5 ug/L for a nonvascular plant (acute).

Guideline Reference:

OPP Aquatic Life Benchmarks

Spatial Representation:

The samples were collected at 1 monitoring site: FIIR-Site 1 (OC 1).

Temporal Representation:

The samples were collected between the dates of 2019-07-01 and 2019-07-01

Environmental Conditions:

QAPP Information:

Cedarville Rancheria QAPP

QAPP Information Reference(s):

Data collected by a California Tribe QAPP Approved by U.S. EPA QAPP Reference

Line of Evidence (LOE) for Decision ID 162803, Propachlor	Region 6
Oak Creek (Inyo County)

LOE ID:

341726

Pollutant:

Propachlor

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Not Recorded

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

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:

OPP Aquatic Life Benchmarks

Spatial Representation:

The samples were collected at 1 monitoring site: FIIR-Site 1 (OC 1).

Temporal Representation:

The samples were collected between the dates of 2019-07-01 and 2019-07-01

Environmental Conditions:

QAPP Information:

Cedarville Rancheria QAPP

QAPP Information Reference(s):

Data collected by a California Tribe QAPP Approved by U.S. EPA QAPP Reference

Line of Evidence (LOE) for Decision ID 162803, Propachlor	Region 6
Oak Creek (Inyo County)

LOE ID:

341727

Pollutant:

Propachlor

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 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: FIIR-Site 1 (OC 1).

Temporal Representation:

The samples were collected between the dates of 2019-07-01 and 2019-07-01

Environmental Conditions:

QAPP Information:

Cedarville Rancheria QAPP

QAPP Information Reference(s):

Data collected by a California Tribe QAPP Approved by U.S. EPA QAPP Reference


DECISION ID	162797	Region 6
Oak Creek (Inyo County)

Pollutant:	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:

Line of Evidence (LOE) for Decision ID 162797, Pyrene	Region 6
Oak Creek (Inyo County)

LOE ID:

341730

Pollutant:

Pyrene

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 Pyrene criteria for the protection of human health from the consumption of water and organisms is 960 ug/L (California Toxics Rule, 2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: FIIR-Site 1 (OC 1).

Temporal Representation:

The samples were collected between the dates of 2019-07-01 and 2019-07-01

Environmental Conditions:

QAPP Information:

Cedarville Rancheria QAPP

QAPP Information Reference(s):

Data collected by a California Tribe QAPP Approved by U.S. EPA QAPP Reference

Line of Evidence (LOE) for Decision ID 162797, Pyrene	Region 6
Oak Creek (Inyo County)

LOE ID:

341729

Pollutant:

Pyrene

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 Pyrene criteria for the protection of human health from consumption of organisms only is 11,000 ug/L (California Toxics Rule, 2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: FIIR-Site 1 (OC 1).

Temporal Representation:

The samples were collected between the dates of 2019-07-01 and 2019-07-01

Environmental Conditions:

QAPP Information:

Cedarville Rancheria QAPP

QAPP Information Reference(s):

Data collected by a California Tribe QAPP Approved by U.S. EPA QAPP Reference


DECISION ID	162798	Region 6
Oak Creek (Inyo County)

Pollutant:	Sulfates
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 162798, Sulfates	Region 6
Oak Creek (Inyo County)

LOE ID:

341936

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: FIIR-Site 1 (OC 1).

Temporal Representation:

The samples were collected between the dates of 2019-07-01 and 2019-07-01

Environmental Conditions:

QAPP Information:

Cedarville Rancheria QAPP

QAPP Information Reference(s):

Data collected by a California Tribe QAPP Approved by U.S. EPA QAPP Reference


DECISION ID	163829	Region 6
Oak Creek (Inyo County)

Pollutant:	Total Dissolved Solids
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 163829, Total Dissolved Solids	Region 6
Oak Creek (Inyo County)

LOE ID:

343701

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 Fort Independence Indian Community of Paiute Indians of the Fort Independence Reservation, California 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:

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 72 (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: OC 1 (FIIR-Site 1)

Temporal Representation:

The samples were collected between the dates of 2019-07-01 and 2019-07-01

Environmental Conditions:

QAPP Information:

QAPP Information Reference(s):

Data collected by a California Tribe QAPP Approved by U.S. EPA QAPP Reference


DECISION ID	162796	Region 6
Oak Creek (Inyo County)

Pollutant:	pH
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 162796, pH	Region 6
Oak Creek (Inyo County)

LOE ID:

341686

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 Fort Independence Indian Community of Paiute Indians of the Fort Independence Reservation, California data for Oak Creek (Inyo County) to determine beneficial use support and results are as follows: 0 of 39 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:

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

SWAMP Data:

Non-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: FIIR-Site 2 (OC 2).

Temporal Representation:

The samples were collected between the dates of 2018-01-07 and 2018-12-31

Environmental Conditions:

QAPP Information:

Cedarville Rancheria QAPP

QAPP Information Reference(s):

Data collected by a California Tribe QAPP Approved by U.S. EPA QAPP Reference

Line of Evidence (LOE) for Decision ID 162796, pH	Region 6
Oak Creek (Inyo County)

LOE ID:

341699

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:

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: FIIR-Site 2 (OC 2).

Temporal Representation:

The samples were collected between the dates of 2018-01-07 and 2018-12-31

Environmental Conditions:

QAPP Information:

Cedarville Rancheria QAPP

QAPP Information Reference(s):

Data collected by a California Tribe QAPP Approved by U.S. EPA QAPP Reference

Line of Evidence (LOE) for Decision ID 162796, pH	Region 6
Oak Creek (Inyo County)

LOE ID:

341647

Pollutant:

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

None

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed Fort Independence Indian Community of Paiute Indians of the Fort Independence Reservation, California data for Oak Creek (Inyo County) 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:

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: FIIR-Site 1 (OC 1).

Temporal Representation:

The samples were collected between the dates of 2019-07-01 and 2019-07-01

Environmental Conditions:

QAPP Information:

Cedarville Rancheria QAPP

QAPP Information Reference(s):

Data collected by a California Tribe QAPP Approved by U.S. EPA QAPP Reference

Line of Evidence (LOE) for Decision ID 162796, pH	Region 6
Oak Creek (Inyo County)

LOE ID:

341667

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 Fort Independence Indian Community of Paiute Indians of the Fort Independence Reservation, California data for Oak Creek (Inyo County) 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:

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: FIIR-Site 1 (OC 1).

Temporal Representation:

The samples were collected between the dates of 2019-07-01 and 2019-07-01

Environmental Conditions:

QAPP Information:

Cedarville Rancheria QAPP

QAPP Information Reference(s):

Data collected by a California Tribe QAPP Approved by U.S. EPA QAPP Reference

Line of Evidence (LOE) for Decision ID 162796, pH	Region 6
Oak Creek (Inyo County)

LOE ID:

341676

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 Fort Independence Indian Community of Paiute Indians of the Fort Independence Reservation, California data for Oak Creek (Inyo County) 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:

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: FIIR-Site 1 (OC 1).

Temporal Representation:

The samples were collected between the dates of 2019-07-01 and 2019-07-01

Environmental Conditions:

QAPP Information:

Cedarville Rancheria QAPP

QAPP Information Reference(s):

Data collected by a California Tribe QAPP Approved by U.S. EPA QAPP Reference

Line of Evidence (LOE) for Decision ID 162796, pH	Region 6
Oak Creek (Inyo County)

LOE ID:

341674

Pollutant:

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

None

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

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: FIIR-Site 2 (OC 2).

Temporal Representation:

The samples were collected between the dates of 2018-01-07 and 2018-12-31

Environmental Conditions:

QAPP Information:

Cedarville Rancheria QAPP

QAPP Information Reference(s):

Data collected by a California Tribe QAPP Approved by U.S. EPA QAPP Reference


DECISION ID	162799	Region 6
Oak Creek (Inyo County)

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

Regional Board Conclusion:	This pollutant is being considered for placement on the CWA section 303(d) List under section 3.2 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. Twenty-three of the 40 samples exceed the water quality objective. Based on the readily available data and information, the weight of evidence indicates that there is sufficient justification in favor of placing this water segment-pollutant combination on the 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. Twenty-three of the 40 samples exceed the water quality objective, 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 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 162799, Turbidity	Region 6
Oak Creek (Inyo County)

LOE ID:

341980

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: FIIR-Site 1 (OC 1).

Temporal Representation:

The samples were collected between the dates of 2019-07-01 and 2019-07-01

Environmental Conditions:

QAPP Information:

Cedarville Rancheria QAPP

QAPP Information Reference(s):

Data collected by a California Tribe QAPP Approved by U.S. EPA QAPP Reference

Line of Evidence (LOE) for Decision ID 162799, Turbidity	Region 6
Oak Creek (Inyo County)

LOE ID:

341971

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: FIIR-Site 2 (OC 2).

Temporal Representation:

The samples were collected between the dates of 2018-01-07 and 2018-12-31

Environmental Conditions:

QAPP Information:

Cedarville Rancheria QAPP

QAPP Information Reference(s):

Data collected by a California Tribe QAPP Approved by U.S. EPA QAPP Reference


DECISION ID	162791	Region 6
Oak Creek (Inyo County)

Pollutant:	Iron
Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	New Decision
Revision Status	Original
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 162791, Iron	Region 6
Oak Creek (Inyo County)

LOE ID:

341346

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: FIIR-Site 1 (OC 1).

Temporal Representation:

The samples were collected between the dates of 2019-07-01 and 2019-07-01

Environmental Conditions:

QAPP Information:

Cedarville Rancheria QAPP

QAPP Information Reference(s):

Data collected by a California Tribe QAPP Approved by U.S. EPA QAPP Reference

Line of Evidence (LOE) for Decision ID 162791, Iron	Region 6
Oak Creek (Inyo County)

LOE ID:

341367

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:

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).

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: FIIR-Site 1 (OC 1).

Temporal Representation:

The samples were collected between the dates of 2019-07-01 and 2019-07-01

Environmental Conditions:

QAPP Information:

Cedarville Rancheria QAPP

QAPP Information Reference(s):

Data collected by a California Tribe QAPP Approved by U.S. EPA QAPP Reference

Line of Evidence (LOE) for Decision ID 162791, Iron	Region 6
Oak Creek (Inyo County)

LOE ID:

341353

Pollutant:

Iron

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

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: FIIR-Site 1 (OC 1).

Temporal Representation:

The samples were collected between the dates of 2019-07-01 and 2019-07-01

Environmental Conditions:

QAPP Information:

Cedarville Rancheria QAPP

QAPP Information Reference(s):

Data collected by a California Tribe QAPP Approved by U.S. EPA QAPP Reference


DECISION ID	170059	Region 6
Oak Creek (Inyo County)

Pollutant:	Specific Conductivity
Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	New Decision
Revision Status	Original
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. Two lines of evidence are available in the administrative record to assess this pollutant. Zero of the 40 samples exceed the guideline. 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 40 samples exceed 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 170059, Specific Conductivity	Region 6
Oak Creek (Inyo County)

LOE ID:

341880

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 USGS California Water Science Center data for Oak Creek (Inyo County) to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for SpecificConductivity.

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:

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: USGS-10281500 (OAK C NR INDEPENDENCE CA).

Temporal Representation:

The samples were collected between the dates of 2015-08-28 and 2015-08-28

Environmental Conditions:

QAPP Information:

QAPP for USGS Data Collected during the 2026 Integrated Report Cycle

QAPP Information Reference(s):

QAPP for USGS Data Collected during the 2026 Integrated Report Cycle

Line of Evidence (LOE) for Decision ID 170059, Specific Conductivity	Region 6
Oak Creek (Inyo County)

LOE ID:

341875

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: FIIR-Site 2 (OC 2).

Temporal Representation:

The samples were collected between the dates of 2018-01-07 and 2018-12-31

Environmental Conditions:

QAPP Information:

Cedarville Rancheria QAPP

QAPP Information Reference(s):

Data collected by a California Tribe QAPP Approved by U.S. EPA QAPP Reference