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

Supporting Information

Regional Board 6 - Lahontan Region

Water Body Name:	Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)
Water Body ID:	CAR6031005120080816102743
Water Body Type:	River & Stream


DECISION ID	162325	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

Pollutant:	Manganese
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 4.1 of the Listing Policy. Under this section a single line of evidence is necessary to assess listing status. Six lines of evidence, five which evaluate water data for the MUN beneficial use and one which evaluates water data for the COLD beneficial use. 12 of 21 samples exceed the objective for the MUN beneficial use assessment. 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. 12 of 21 samples exceed the objective for the MUN beneficial use assessment 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 162325, Manganese	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

LOE ID:

338674

Pollutant:

Manganese

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 Upper Owens River Water Quality Project data for Mammoth Creek (Twin Lakes outlet to Old Mammoth Road) to determine beneficial use support and results are as follows: 0 of 3 samples exceeded the water quality threshold for Manganese.

Data Reference:

WQ from the Upper Owens River Water Quality Program 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). The secondary maximum contaminant level listed in Table 64449-A for Manganese 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: 160TWL010 (Downstream Twin Lakes Outlet).

Temporal Representation:

The samples were collected between the dates of 2012-06-12 and 2012-10-31

Environmental Conditions:

QAPP Information:

Quality Assurance Project Plan (QAPP) for Upper Owens River Water Quality Project Data

QAPP Information Reference(s):

Quality Assurance Project Plan (QAPP) for Upper Owens River Water Quality Project Data

Line of Evidence (LOE) for Decision ID 162325, Manganese	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

LOE ID:

341420

Pollutant:

Manganese

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: USGS-10265125 (MAMMOTH C A TWIN LAKES NR MAMMOTH LAKES CA).

Temporal Representation:

The samples were collected between the dates of 2018-07-25 and 2021-08-02

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 162325, Manganese	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

LOE ID:

338676

Pollutant:

Manganese

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 Upper Owens River Water Quality Project data for Mammoth Creek (Twin Lakes outlet to Old Mammoth Road) to determine beneficial use support and results are as follows: 3 of 3 samples exceeded the water quality threshold for Manganese.

Data Reference:

WQ from the Upper Owens River Water Quality Program 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: 160MAM040 (Upstream from Sherwin St. bridge (South)).

Temporal Representation:

The samples were collected between the dates of 2012-06-12 and 2012-10-31

Environmental Conditions:

QAPP Information:

Quality Assurance Project Plan (QAPP) for Upper Owens River Water Quality Project Data

QAPP Information Reference(s):

Quality Assurance Project Plan (QAPP) for Upper Owens River Water Quality Project Data

Line of Evidence (LOE) for Decision ID 162325, Manganese	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

LOE ID:

338675

Pollutant:

Manganese

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 Upper Owens River Water Quality Project data for Mammoth Creek (Twin Lakes outlet to Old Mammoth Road) to determine beneficial use support and results are as follows: 1 of 1 samples exceeded the water quality threshold for Manganese.

Data Reference:

WQ from the Upper Owens River Water Quality Program 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: 160VAL020 (Central Valentine Spring Complex).

Temporal Representation:

The samples were collected between the dates of 2012-10-31 and 2012-10-31

Environmental Conditions:

QAPP Information:

Quality Assurance Project Plan (QAPP) for Upper Owens River Water Quality Project Data

QAPP Information Reference(s):

Quality Assurance Project Plan (QAPP) for Upper Owens River Water Quality Project Data

Line of Evidence (LOE) for Decision ID 162325, Manganese	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

LOE ID:

7220

Pollutant:

Manganese

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 this station under the Region 6 SWAMP program between 2001 and 2005. Concentrations of total manganese ranged from 34 to 157 ug/L. Eight samples exceeded the MCL.

Data Reference:

2007. SWAMP Data for the Owens Hydrologic Unit

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 manganese 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, "Mammoth Creek at Old Mammoth Road" was sampled.

Temporal Representation:

Ten samples were collected approximately quarterly between 2001 and 2005.

Environmental Conditions:

Mammoth Creek is a tributary of the Owens River with headwaters near the Sierra Nevada crest. The lower reach of Mammoth Creek is influenced by geothermal springs and is called Hot Creek.

QAPP Information:

The data meet the quality assurance requirements of the SWAMP QAPP.

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 162325, Manganese	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

LOE ID:

7219

Pollutant:

Manganese

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 this station under the Region 6 SWAMP program approximately quarterly between 2001 and 2005. Concentrations of dissolved manganese in 10 samples ranged from 13.7 to 157 ug/L.

Data Reference:

2007. SWAMP Data for the Owens Hydrologic Unit

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

There are no state or federal standards or criteria for manganese 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, "Mammoth Creek at Old Mammoth Road" was sampled.

Temporal Representation:

Ten samples were collected approximately quarterly between 2001 and 2005.

Environmental Conditions:

Mammoth Creek is a tributary of the Owens River with headwaters near the Sierra Nevada crest. The lower reach of Mammoth Creek is influenced by geothermal springs and is called Hot Creek. In addition to the Cold Freshwater Habitat beneficial use, Mammoth Creek is designated for the Spawning, Reproduction and Development and Migration of Aquatic Organisms beneficial uses.

QAPP Information:

The data meet the quality assurance requirements of the SWAMP QAPP.

QAPP Information Reference(s):


DECISION ID	170638	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

Pollutant:	Mercury
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 \| Unknown Nonpoint Source \| Unknown Point Source
TMDL Priority:	High
Impairment from Pollutant or Pollution:	Pollutant

Regional Board Conclusion:	This pollutant is being considered for removal from the section 303(d) list under section 4.1 and 4.5 of the Listing Policy. Under section 4.1 a single line of evidence is necessary to assess listing status. Twenty-one lines of evidence are available in the administrative record to assess this pollutant. Two out of 3 fish tissue samples exceed the objectives for the COMM beneficial use. 4 of 34 water samples exceed the objective for the MUN beneficial use. 0 of 34 samples exceed the objective for the COLD beneficial use. 1 of 14 samples exceed the criteria for the COMM beneficial use. 5 of 6 sediment samples exceed the evaluation guideline for the COLD beneficial use. 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 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. 2 of 3 fish tissue samples and 5 of 34 water samples exceed the objective for the MUN beneficial use, and these data are sufficient to recommend leaving this waterbody/pollutant combination on the 303(d) list as they exceed the allowable exceedance frequency in table 4.1 of the Listing Policy. 4. Pursuant to section 4.11 of the Listing Policy, no additional data and information are available indicating that standards are not met.

Regional Board Decision Recommendation:	After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should 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 170638, Mercury	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

LOE ID:

9114

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:

Fixed station physical/chemical (conventional plus toxic pollutants)

Data Used to Assess Water Quality:

The U.S. Geological Survey sampled this station between 2001 and 2005 under the Region 6 SWAMP program. Concentrations of dissolved mercury in 8 of 10 samples were below the detection level, and a ninth sample was an estimated value. One sample had a dissolved mercury concentraiton of 0.01 ug/L.

Data Reference:

2007. SWAMP Data for the Owens Hydrologic Unit

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

There are no state or federal criteria for dissolved mercury for the protection of aquatic life. The U.S. Environmental Protection Agency's freshwater aquatic life criteria are expressed as total mercury.

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

One station, "Mammoth Creek at Old Mammoth Road" was sampled.

Temporal Representation:

Ten samples (1 to 4 per year) were collected between 2001 and 2005. No samples were collected in 2002.

Environmental Conditions:

Mammoth Creek is a tributary of the Owens River with headwaters near the Sierra Nevada crest. The lower reach of Mammoth Creek is influenced by geothermal springs and is called Hot Creek.

QAPP Information:

The data meet the quality assurance requirements of the SWAMP QAPP.

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 170638, Mercury	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

LOE ID:

338688

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 Upper Owens River Water Quality Project data for Mammoth Creek (Twin Lakes outlet to Old Mammoth Road) to determine beneficial use support and results are as follows: 0 of 2 samples exceeded the water quality threshold for Mercury.

Data Reference:

WQ from the Upper Owens River Water Quality Program 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:

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: 160MAM046 (Snowcreek Meadow Preserve at Fascination Rd.).

Temporal Representation:

The samples were collected between the dates of 2013-04-17 and 2013-06-05

Environmental Conditions:

QAPP Information:

Quality Assurance Project Plan (QAPP) for Upper Owens River Water Quality Project Data

QAPP Information Reference(s):

Quality Assurance Project Plan (QAPP) for Upper Owens River Water Quality Project Data

Line of Evidence (LOE) for Decision ID 170638, Mercury	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

LOE ID:

338727

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:

Water Board staff assessed Upper Owens River Water Quality Project data for Mammoth Creek (Twin Lakes outlet to Old Mammoth Road) to determine beneficial use support and results are as follows: 0 of 2 samples exceeded the water quality threshold for Mercury.

Data Reference:

WQ from the Upper Owens River Water Quality Program 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:

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: 160MAM046 (Snowcreek Meadow Preserve at Fascination Rd.).

Temporal Representation:

The samples were collected between the dates of 2013-04-17 and 2013-06-05

Environmental Conditions:

QAPP Information:

Quality Assurance Project Plan (QAPP) for Upper Owens River Water Quality Project Data

QAPP Information Reference(s):

Quality Assurance Project Plan (QAPP) for Upper Owens River Water Quality Project Data

Line of Evidence (LOE) for Decision ID 170638, Mercury	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

LOE ID:

338716

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:

WQ from the Upper Owens River Water Quality Program 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: 160MAM048 (Snowcreek Meadow Preserve at Gold Hill Rd.).

Temporal Representation:

The samples were collected between the dates of 2013-04-17 and 2013-07-23

Environmental Conditions:

QAPP Information:

Quality Assurance Project Plan (QAPP) for Upper Owens River Water Quality Project Data

QAPP Information Reference(s):

Quality Assurance Project Plan (QAPP) for Upper Owens River Water Quality Project Data

Line of Evidence (LOE) for Decision ID 170638, Mercury	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

LOE ID:

338728

Pollutant:

Mercury

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Commercial or recreational collection of fish, shellfish, or organisms

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

WQ from the Upper Owens River Water Quality Program 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: 160TWL010 (Downstream Twin Lakes Outlet).

Temporal Representation:

The samples were collected between the dates of 2012-06-12 and 2012-10-31

Environmental Conditions:

QAPP Information:

Quality Assurance Project Plan (QAPP) for Upper Owens River Water Quality Project Data

QAPP Information Reference(s):

Quality Assurance Project Plan (QAPP) for Upper Owens River Water Quality Project Data

Line of Evidence (LOE) for Decision ID 170638, Mercury	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

LOE ID:

338733

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:

Water Board staff assessed Upper Owens River Water Quality Project data for Mammoth Creek (Twin Lakes outlet to Old Mammoth Road) to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Mercury.

Data Reference:

WQ from the Upper Owens River Water Quality Program 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: 160VAL020 (Central Valentine Spring Complex).

Temporal Representation:

The samples were collected between the dates of 2012-10-31 and 2012-10-31

Environmental Conditions:

QAPP Information:

Quality Assurance Project Plan (QAPP) for Upper Owens River Water Quality Project Data

QAPP Information Reference(s):

Quality Assurance Project Plan (QAPP) for Upper Owens River Water Quality Project Data

Line of Evidence (LOE) for Decision ID 170638, Mercury	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

LOE ID:

338731

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 Upper Owens River Water Quality Project data for Mammoth Creek (Twin Lakes outlet to Old Mammoth Road) to determine beneficial use support and results are as follows: 1 of 3 samples exceeded the water quality threshold for Mercury.

Data Reference:

WQ from the Upper Owens River Water Quality Program 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: 160MAM048 (Snowcreek Meadow Preserve at Gold Hill Rd.).

Temporal Representation:

The samples were collected between the dates of 2013-04-17 and 2013-07-23

Environmental Conditions:

QAPP Information:

Quality Assurance Project Plan (QAPP) for Upper Owens River Water Quality Project Data

QAPP Information Reference(s):

Quality Assurance Project Plan (QAPP) for Upper Owens River Water Quality Project Data

Line of Evidence (LOE) for Decision ID 170638, Mercury	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

LOE ID:

338757

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 Upper Owens River Water Quality Project data for Mammoth Creek (Twin Lakes outlet to Old Mammoth Road) to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Mercury.

Data Reference:

WQ from the Upper Owens River Water Quality Program 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: 160VAL020 (Central Valentine Spring Complex).

Temporal Representation:

The samples were collected between the dates of 2012-10-31 and 2012-10-31

Environmental Conditions:

QAPP Information:

Quality Assurance Project Plan (QAPP) for Upper Owens River Water Quality Project Data

QAPP Information Reference(s):

Quality Assurance Project Plan (QAPP) for Upper Owens River Water Quality Project Data

Line of Evidence (LOE) for Decision ID 170638, Mercury	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

LOE ID:

9115

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:

Fixed station physical/chemical (conventional plus toxic pollutants)

Data Used to Assess Water Quality:

Data Reference:

2007. SWAMP Data for the Owens Hydrologic Unit

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

There are no state or federal criteria for dissolved mercury for the protection of human health.

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

One station, "Mammoth Creek at Old Mammoth Road" was sampled.

Temporal Representation:

Ten samples (1 to 4 per year) were collected between 2001 and 2005. No samples were collected in 2002.

Environmental Conditions:

Mammoth Creek is a tributary of the Owens River with headwaters near the Sierra Nevada crest. The lower reach of Mammoth Creek is influenced by geothermal springs and is called Hot Creek.

QAPP Information:

The data meet the quality assurance requirements of the SWAMP QAPP.

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 170638, Mercury	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

LOE ID:

6961

Pollutant:

Mercury

LOE Subgroup:

Pollutant-Tissue

Matrix:

Tissue

Fraction:

Total

Beneficial Use:

Commercial or recreational collection of fish, shellfish, or organisms

Number of Samples:

Number of Exceedances:

Data and Information Type:

Not Specified

Data Used to Assess Water Quality:

Two out of 3 samples exceeded. Three filet composite samples of brown trout were collected in 1992, 1995, and 2002. The 1992 and 2002 samples exceeded the guideline (TSMP, 2002).

Data Reference:

Toxic Substances Monitoring Program data for years 1992-2002 and Coastal Fish Contamination Program for years 1 and 2. State Water Resources Control Board

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

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

Objective/Criterion Reference:

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

Evaluation Guideline:

0.3 ug/g (OEHHA Screening Value) (Brodberg & Pollock, 1999).

Guideline Reference:

Prevalence of Selected Target Chemical Contaminants in Sport Fish From Two California Lakes: Public health designed screening study. Sacramento, CA: Office of Environmental Health Hazard Assessment

Spatial Representation:

Two stations were sampled: 1.3 miles downstream from Old Mammoth Road on Old State Road and between Hwy 395 and frontage road east of Hwy 395.

Temporal Representation:

Samples were collected annually in 1992, 1995, and 2002.

Environmental Conditions:

QAPP Information:

Toxic Substances Monitoring Program 1992-93 and 1994-95 Data Reports.
Environmental Chemistry Quality Assurance and Data Report for the Toxic Substances Monitoring Program, 2001-2002. Department of Fish and Game.

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 170638, Mercury	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

LOE ID:

9113

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 this station between 2001 and 2005 under the Region 6 SWAMP program. One of 10 samples for total mercury was an estimated value. Mercury concentrations in the remaining samples ranged from 0.02 to 0.08 mg/L. The aquatic life criteria were not exceeded.

Data Reference:

2007. SWAMP Data for the Owens Hydrologic Unit

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

The U.S. Environmental Protection Agency's national freshwater aquatic life criteria (for total mercury) include a 4-day average of 0.77 ug/L and a 1-hour average of 1.4 ug/L.

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

One station, "Mammoth Creek at Old Mammoth Road" was sampled.

Temporal Representation:

Ten samples (1 to 4 per year) were collected between 2001 and 2005. No samples were collected in 2002.

Environmental Conditions:

Mammoth Creek is a tributary of the Owens River with headwaters near the Sierra Nevada crest. The lower reach of Mammoth Creek is influenced by geothermal springs and is called Hot Creek.

QAPP Information:

The data meet the quality assurance requirements of the SWAMP QAPP.

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 170638, Mercury	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

LOE ID:

338742

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:

WQ from the Upper Owens River Water Quality Program 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: 160TWL010 (Downstream Twin Lakes Outlet).

Temporal Representation:

The samples were collected between the dates of 2012-06-12 and 2012-10-31

Environmental Conditions:

QAPP Information:

Quality Assurance Project Plan (QAPP) for Upper Owens River Water Quality Project Data

QAPP Information Reference(s):

Quality Assurance Project Plan (QAPP) for Upper Owens River Water Quality Project Data

Line of Evidence (LOE) for Decision ID 170638, Mercury	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

LOE ID:

9112

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:

Data Reference:

2007. SWAMP Data for the Owens Hydrologic Unit

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

The California Toxics Rule (CTR) human health standard for consumption of water and organisms is 0.05 ug/L total mercury as a 30-day average.

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

One station, "Mammoth Creek at Old Mammoth Road" was sampled.

Temporal Representation:

Ten samples (1 to 4 per year) were collected between 2001 and 2005. No samples were collected in 2002.

Environmental Conditions:

Mammoth Creek is a tributary of the Owens River with headwaters near the Sierra Nevada crest. The lower reach of Mammoth Creek is influenced by geothermal springs and is called Hot Creek.

QAPP Information:

The data meet the quality assurance requirements of the SWAMP QAPP.

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 170638, Mercury	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

LOE ID:

338734

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 Upper Owens River Water Quality Project data for Mammoth Creek (Twin Lakes outlet to Old Mammoth Road) to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Mercury.

Data Reference:

WQ from the Upper Owens River Water Quality Program 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: 160VAL020 (Central Valentine Spring Complex).

Temporal Representation:

The samples were collected between the dates of 2012-10-31 and 2012-10-31

Environmental Conditions:

QAPP Information:

Quality Assurance Project Plan (QAPP) for Upper Owens River Water Quality Project Data

QAPP Information Reference(s):

Quality Assurance Project Plan (QAPP) for Upper Owens River Water Quality Project Data

Line of Evidence (LOE) for Decision ID 170638, Mercury	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

LOE ID:

338730

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:

Data Reference:

WQ from the Upper Owens River Water Quality Program 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: 160TWL010 (Downstream Twin Lakes Outlet).

Temporal Representation:

The samples were collected between the dates of 2012-06-12 and 2012-10-31

Environmental Conditions:

QAPP Information:

Quality Assurance Project Plan (QAPP) for Upper Owens River Water Quality Project Data

QAPP Information Reference(s):

Quality Assurance Project Plan (QAPP) for Upper Owens River Water Quality Project Data

Line of Evidence (LOE) for Decision ID 170638, Mercury	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

LOE ID:

338702

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 Upper Owens River Water Quality Project data for Mammoth Creek (Twin Lakes outlet to Old Mammoth Road) to determine beneficial use support and results are as follows: 1 of 3 samples exceeded the water quality threshold for Mercury.

Data Reference:

WQ from the Upper Owens River Water Quality Program 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: 160MAM048 (Snowcreek Meadow Preserve at Gold Hill Rd.).

Temporal Representation:

The samples were collected between the dates of 2013-04-17 and 2013-07-23

Environmental Conditions:

QAPP Information:

Quality Assurance Project Plan (QAPP) for Upper Owens River Water Quality Project Data

QAPP Information Reference(s):

Quality Assurance Project Plan (QAPP) for Upper Owens River Water Quality Project Data

Line of Evidence (LOE) for Decision ID 170638, Mercury	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

LOE ID:

338699

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 Upper Owens River Water Quality Project data for Mammoth Creek (Twin Lakes outlet to Old Mammoth Road) to determine beneficial use support and results are as follows: 0 of 2 samples exceeded the water quality threshold for Mercury.

Data Reference:

WQ from the Upper Owens River Water Quality Program 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: 160MAM046 (Snowcreek Meadow Preserve at Fascination Rd.).

Temporal Representation:

The samples were collected between the dates of 2013-04-17 and 2013-06-05

Environmental Conditions:

QAPP Information:

Quality Assurance Project Plan (QAPP) for Upper Owens River Water Quality Project Data

QAPP Information Reference(s):

Quality Assurance Project Plan (QAPP) for Upper Owens River Water Quality Project Data

Line of Evidence (LOE) for Decision ID 170638, Mercury	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

LOE ID:

338703

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 Upper Owens River Water Quality Project data for Mammoth Creek (Twin Lakes outlet to Old Mammoth Road) to determine beneficial use support and results are as follows: 0 of 5 samples exceeded the water quality threshold for Mercury.

Data Reference:

WQ from the Upper Owens River Water Quality Program 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: 160MAM040 (Upstream from Sherwin St. bridge (South)).

Temporal Representation:

The samples were collected between the dates of 2012-08-14 and 2013-07-23

Environmental Conditions:

QAPP Information:

Quality Assurance Project Plan (QAPP) for Upper Owens River Water Quality Project Data

QAPP Information Reference(s):

Quality Assurance Project Plan (QAPP) for Upper Owens River Water Quality Project Data

Line of Evidence (LOE) for Decision ID 170638, Mercury	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

LOE ID:

338756

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:

Water Board staff assessed Upper Owens River Water Quality Project data for Mammoth Creek (Twin Lakes outlet to Old Mammoth Road) to determine beneficial use support and results are as follows: 0 of 5 samples exceeded the water quality threshold for Mercury.

Data Reference:

WQ from the Upper Owens River Water Quality Program 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: 160MAM040 (Upstream from Sherwin St. bridge (South)).

Temporal Representation:

The samples were collected between the dates of 2012-08-14 and 2013-07-23

Environmental Conditions:

QAPP Information:

Quality Assurance Project Plan (QAPP) for Upper Owens River Water Quality Project Data

QAPP Information Reference(s):

Quality Assurance Project Plan (QAPP) for Upper Owens River Water Quality Project Data

Line of Evidence (LOE) for Decision ID 170638, Mercury	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

LOE ID:

338692

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 Upper Owens River Water Quality Project data for Mammoth Creek (Twin Lakes outlet to Old Mammoth Road) to determine beneficial use support and results are as follows: 0 of 5 samples exceeded the water quality threshold for Mercury.

Data Reference:

WQ from the Upper Owens River Water Quality Program 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: 160MAM040 (Upstream from Sherwin St. bridge (South)).

Temporal Representation:

The samples were collected between the dates of 2012-08-14 and 2013-07-23

Environmental Conditions:

QAPP Information:

Quality Assurance Project Plan (QAPP) for Upper Owens River Water Quality Project Data

QAPP Information Reference(s):

Quality Assurance Project Plan (QAPP) for Upper Owens River Water Quality Project Data

Line of Evidence (LOE) for Decision ID 170638, Mercury	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

LOE ID:

337181

Pollutant:

Mercury

LOE Subgroup:

Pollutant-Sediment

Matrix:

Sediment

Fraction:

Total

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

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:

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

Objective/Criterion Reference:

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

Evaluation Guideline:

The evaluation guideline for mercury is the probable effect concentration (PEC) of 1.06 mg/kg dry weight (MacDonald et al., 2000a).

Guideline Reference:

Development and evaluation of consensus-based sediment quality guidelines for freshwater ecosystems. Environmental Contamination and Toxicology. 39: 20-31

Spatial Representation:

Data were collected from 1 station(s). Station Code(s): 603MAM014 (Mammoth Creek above Horsecamp).

Temporal Representation:

Data for this waterbody were collected over the date range 2021-05-06 to 2021-10-06

Environmental Conditions:

QAPP Information:

Generic SWAMP QAPrP

QAPP Information Reference(s):

Generic SWAMP QAPrP


DECISION ID	163746	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

Pollutant:	Total Dissolved Solids
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. Eight lines of evidence, seven which assess the available data for the COLD beneficial use and one which assesses the available data for the MUN beneficial use, are available in the administrative record to assess this pollutant. Nine of 17 samples exceed the water quality objective for the COLD beneficial use; 0 of 10 samples exceed the objective for the MUN beneficial use. 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. Nine of 17 samples exceed the water quality objective for the COLD beneficial use, 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 163746, Total Dissolved Solids	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

LOE ID:

96597

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 by Lahontan Water Board staff under the same protocol and using the same monitoring station for both projects. Data were collected between November 2014 and December 2016 with approximately once per month frequency. Concentrations in the raw data ranged from 68 to 220 mg/L. Three annual averages were computed from data, all of which exceeded the site specific objective.

Data Reference:

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

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 Dissolved Solids (TDS) in Mammoth Creek (Twin Lakes outlet to Old Mammoth Road), as referenced in the Lahontan Basin Plan Table 3-17, is an annual average not to exceed 85 mg/L.

Objective/Criterion Reference:

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

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

Data were collected at site 603MAM014, which is found in Mammoth City Park next to Old Mammoth Road.

Temporal Representation:

Data were collected starting in November 2014 and were predominately collected on a per month basis.

Environmental Conditions:

Mammoth Creek is a tributary of the Owens River with headwaters near the Sierra Nevada crest. The Twin Lakes outlet to Old Mammoth Road reach drains the headwaters segment and flows through the town of Mammoth, passing through several residential neighborhoods and Mammoth Park.

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 163746, Total Dissolved Solids	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

LOE ID:

7240

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 this station under the Region 6 SWAMP program approximately quarterly between 2001 and 2005. (No samples were collected in 2002.) Concentrations of TDS in 10 samples ranged from
44 to 136 mg/L. Annual averages (calculated from 1 to 4 samples per year) ranged from 97 to 127 mg/L. The annual average objective was exceeded in 4 out of 4 years.

Data Reference:

2007. SWAMP Data for the Owens Hydrologic Unit

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

The site-specific objective for Total Dissolved Solids (TDS) at this station (from Lahontan Basin Plan Table 3-17) includes an annual average TDS concentration of 85 mg/L; and a 90th percentile value of 115 mg/L.

Objective/Criterion Reference:

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

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

One station, "Mammoth Creek at Twin Lakes" was sampled.

Temporal Representation:

Ten samples (1 to 4 per year) were collected quarterly in 2001 and from 2003 to 2005.

Environmental Conditions:

Mammoth Creek is a tributary of the Owens River with headwaters near the Sierra Nevada crest. The lower reach of Mammoth Creek is influenced by geothermal springs and is called Hot Creek. In addition to the Cold Freshwater Habitat beneficial use, Mammoth Creek is designated for the Spawning, Reproduction and Development¿ and Migration of Aquatic Organisms beneficial uses.

QAPP Information:

The data meet the quality assurance requirements of the SWAMP QAPP.

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 163746, Total Dissolved Solids	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

LOE ID:

7245

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 this station approximately quarterly under the Region 6 SWAMP program between 2001 and 2005. (No samples were collected in 2002.) Concentrations of TDS in ten quarterly samples ranged from 44 to 136 mg/L. The MCL was not exceeded.

Data Reference:

2007. SWAMP Data for the Owens Hydrologic Unit

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 recommended 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, "Mammoth Creek at Old Mammoth Road" was sampled.

Temporal Representation:

Ten samples (1 to 4 per year) were collected approximately quarterly between 2001 and 2005. (No samples were collected in 2002.)

Environmental Conditions:

Mammoth Creek is a tributary of the Owens River with headwaters near the Sierra Nevada crest. The lower reach of Mammoth Creek is influenced by geothermal springs and is called Hot Creek.

QAPP Information:

The data meet the quality assurance requirements of the SWAMP QAPP.

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 163746, Total Dissolved Solids	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

LOE ID:

343369

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:
0 of 2 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 85 (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: Mammoth Cr, at Twin Lakes (603MAM008)

Temporal Representation:

The samples were collected between the dates of 2016-02-04 and 2017-06-28

Environmental Conditions:

QAPP Information:

Generic SWAMP QAPrP

QAPP Information Reference(s):

Generic SWAMP QAPrP

Line of Evidence (LOE) for Decision ID 163746, Total Dissolved Solids	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

LOE ID:

343367

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 85 (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: Mammoth Cr, at Twin Lakes (603MAM008)

Temporal Representation:

The samples were collected between the dates of 2017-01-31 and 2017-10-04

Environmental Conditions:

QAPP Information:

Generic SWAMP QAPrP

QAPP Information Reference(s):

Generic SWAMP QAPrP

Line of Evidence (LOE) for Decision ID 163746, Total Dissolved Solids	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

LOE ID:

343368

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:
1 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 85 (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: Mammoth Creek above Horsecamp (603MAM014)

Temporal Representation:

The samples were collected between the dates of 2017-01-31 and 2017-10-04

Environmental Conditions:

QAPP Information:

Generic SWAMP QAPrP

QAPP Information Reference(s):

Generic SWAMP QAPrP

Line of Evidence (LOE) for Decision ID 163746, Total Dissolved Solids	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

LOE ID:

343694

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 USGS California Water Science Center data to determine beneficial use support and results are as follows:
0 of 4 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 85 (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: MAMMOTH C A TWIN LAKES NR MAMMOTH LAKES CA (USGS-10265125)

Temporal Representation:

The samples were collected between the dates of 2018-07-25 and 2021-08-02

Environmental Conditions:

QAPP Information:

QAPP Information Reference(s):

QAPP for USGS Data Collected during the 2026 Integrated Report Cycle

Line of Evidence (LOE) for Decision ID 163746, Total Dissolved Solids	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

LOE ID:

343381

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 2 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 85 (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: Mammoth Creek above Horsecamp (603MAM014)

Temporal Representation:

The samples were collected between the dates of 2016-02-04 and 2017-08-30

Environmental Conditions:

QAPP Information:

Generic SWAMP QAPrP

QAPP Information Reference(s):

Generic SWAMP QAPrP


DECISION ID	169040	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

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 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. 5 lines of evidence are available in the administrative record to assess this pollutant. 0 of 20 samples exceeded the COLD evaluation guideline. 0 of 30 samples exceeded the MUN objective (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 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 exceeded the COLD evaluation guideline. Zero of 30 samples exceeded the MUN objective (MCL) and these do not exceed the allowable frequency listed in Table 3.1 of the Listing Policy. 4. Pursuant to section 3.11 of the Listing Policy, no additional data and information are available indicating that standards are not met.

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

State Board Review of Regional Board Conclusion and Recommendation:

State Board Decision Recommendation:

Line of Evidence (LOE) for Decision ID 169040, Aluminum	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

LOE ID:

7200

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 this station under the Region 6 SWAMP program between 2001 and 2005. Concentrations of total aluminum in 10 samples ranged from 6 to 88 ug/L The MCLs were not exceeded.

Data Reference:

2007. SWAMP Data for the Owens Hydrologic Unit

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, "Mammoth Creek at Old Mammoth Road" was sampled.

Temporal Representation:

Ten samples (1 to 4 per year) were collected between 2001 and 2005. No samples were collected in 2002.

Environmental Conditions:

Mammoth Creek is a tributary of the Owens River with headwaters near the Sierra Nevada crest. The lower reach of Mammoth Creek is influenced by geothermal springs and is called Hot Creek.

QAPP Information:

The data meet the quality assurance requirements of the SWAMP QAPP.

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 169040, Aluminum	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

LOE ID:

348097

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 Owens Hydrologic Unit

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: 603MAM007 (Mammoth Cr, at Old Mammoth Rd).

Temporal Representation:

The samples were collected between the dates of 2001-08-15 and 2005-07-21

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 169040, Aluminum	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

LOE ID:

348092

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:

2007. SWAMP Data for the Owens Hydrologic Unit

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: 603MAM007 (Mammoth Cr, at Old Mammoth Rd).

Temporal Representation:

The samples were collected between the dates of 2001-08-15 and 2005-07-21

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 169040, Aluminum	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

LOE ID:

348095

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 Owens Hydrologic Unit

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: 603MAM007 (Mammoth Cr, at Old Mammoth Rd).

Temporal Representation:

The samples were collected between the dates of 2001-08-15 and 2005-07-21

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 169040, Aluminum	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

LOE ID:

348094

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 Owens Hydrologic Unit

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: 603MAM007 (Mammoth Cr, at Old Mammoth Rd).

Temporal Representation:

The samples were collected between the dates of 2001-08-15 and 2005-07-21

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	170029	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

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

Regional Board Conclusion:	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 170029, Ammonia	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

LOE ID:

338149

Pollutant:

Nitrogen, ammonia (Total Ammonia)

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:

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 total ammonia water quality objective to protect aquatic life in freshwater is temperature and pH dependent and is calculated according to the equation for the four-day criterion defined in Chapter 3 of The Water Quality Control Plan for the 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: 603MAM008 (Mammoth Cr, at Twin Lakes).

Temporal Representation:

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

Environmental Conditions:

QAPP Information:

Generic SWAMP QAPrP

QAPP Information Reference(s):

Generic SWAMP QAPrP

Line of Evidence (LOE) for Decision ID 170029, Ammonia	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

LOE ID:

338284

Pollutant:

Ammonia (Unionized)

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:

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 un-ionized ammonia water quality objective to protect aquatic life in freshwater is temperature and pH dependent and is calculated according to the equation for the four-day criterion defined in Chapter 3 of The Water Quality Control Plan for the 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: 603MAM008 (Mammoth Cr, at Twin Lakes).

Temporal Representation:

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

Environmental Conditions:

QAPP Information:

Generic SWAMP QAPrP

QAPP Information Reference(s):

Generic SWAMP QAPrP


DECISION ID	162321	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

Pollutant:	Arsenic
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. Four lines of evidence are available in the administrative record to assess this pollutant, two for MUN and two COLD. Zero of the 14 samples for MUN and zero for the 14 for COLD exceed the California Maximum Contaminant Level for arsenic incorporated by reference in the Basin Plan. 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 the 14 samples for MUN and zero of the 14 for COLD exceed the California Maximum Contaminant Level for arsenic incorporated by reference in the Basin Plan. This does not exceed the allowable frequency listed in Table 3.1 of the Listing Policy. 4. Pursuant to section 3.11 of the Listing Policy, no additional data and information are available indicating that standards are not met.

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

State Board Review of Regional Board Conclusion and Recommendation:

State Board Decision Recommendation:

Line of Evidence (LOE) for Decision ID 162321, Arsenic	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

LOE ID:

341099

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:

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:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: USGS-10265125 (MAMMOTH C A TWIN LAKES NR MAMMOTH LAKES CA).

Temporal Representation:

The samples were collected between the dates of 2018-07-25 and 2021-08-02

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 162321, Arsenic	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

LOE ID:

341083

Pollutant:

Arsenic

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 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: USGS-10265125 (MAMMOTH C A TWIN LAKES NR MAMMOTH LAKES CA).

Temporal Representation:

The samples were collected between the dates of 2018-07-25 and 2021-08-02

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 162321, Arsenic	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

LOE ID:

7202

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:

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. In 10 samples collected approximately quarterly, concentrations of total arsenic ranged from 2 to 5 ug/L. The MCL was not exceeded.

Data Reference:

2007. SWAMP Data for the Owens Hydrologic Unit

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 arsenic is 10 ug/L.

Objective/Criterion Reference:

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

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

One station, "Mammoth Creek at Twin Lakes" was sampled.

Temporal Representation:

Ten samples were collected approximately quarterly between 2001 and 2005.

Environmental Conditions:

QAPP Information:

The data meet the quality assurance requirements of the SWAMP QAPP.

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 162321, Arsenic	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

LOE ID:

7201

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:

Fixed station physical/chemical (conventional plus toxic pollutants)

Data Used to Assess Water Quality:

The U.S. Geological Survey sampled this station approximately quarterly under the Region 6 SWAMP program between 2001 and 2005. One of 10 quarterly samples was an estimated value. Concentrations of dissolved arsenic in the remaining 9 samples ranged from 2 to 4 ug/L. The California Toxics Rule standards were not exceeded.

Data Reference:

2007. SWAMP Data for the Owens Hydrologic Unit

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

The California Toxics Rule arsenic standards for the protection of freshwater aquatic life are as follows:
4-day average = 150 ug/L
1-hour average = 340 ug/L.

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

One station, "Mammoth Creek at Old Mammoth Road" was sampled.

Temporal Representation:

Ten samples were collected approximately quarterly between 2001 and 2005.

Environmental Conditions:

Mammoth Creek is a tributary of the Owens River with headwaters near the Sierra Nevada crest. The lower reach of Mammoth Creek is influenced by geothermal springs and is called Hot Creek. In addition to the Cold Freshwater Habitat beneficial use, Mammoth Creek is designated for the ¿Spawning, Reproduction and Development¿ and Migration of Aquatic Organisms beneficial uses. Arsenic in this watershed comes from natural volcanic and geothermal sources.

QAPP Information:

The data meet the quality assurance requirements of the SWAMP QAPP.

QAPP Information Reference(s):


DECISION ID	170925	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

Pollutant:	Benthic Community Effects
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:	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. One line of evidence evaluating benthic-macroinvertebrate bioassessment data is available in the administrative record to assess this indicator. Zero of one benthic-macroinvertebrate samples exceed the California Stream Condition Index (CSCI) impairment threshold. These data indicate 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. Based on the readily available data and information, the weight of evidence indicates that there is sufficient justification against placing 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 one 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. The available information indicates that the waterbody/pollutant combination should not be placed on the 303(d) List of impaired waters at this time. 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 170925, Benthic Community Effects	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

LOE ID:

352707

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 603MAM008 to determine beneficial use support and the results are as follows: 0 of 1 samples exceeded the water quality standard. CSCI scores were from 0.82 to 0.82 .

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:

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:

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:

The samples were collected at 1 monitoring site: 603MAM008 (Mammoth Cr, at Twin Lakes).

Temporal Representation:

Samples were collected from 2017-08-22 to 2017-08-22.

Environmental Conditions:

QAPP Information:

Generic SWAMP QAPrP

QAPP Information Reference(s):

Generic SWAMP QAPrP


DECISION ID	162322	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

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 162322, Boron	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

LOE ID:

8837

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:

Fixed station physical/chemical (conventional plus toxic pollutants)

Data Used to Assess Water Quality:

The U.S. Geological Survey sampled this station approximately quarterly under the Region 6 SWAMP program between July 28, 2004 and July 21, 2005. The concentration of dissolved boron in one of four samples was below the detection level. Another sample was an estimated value. The dissolved boron concentrations in the two remaining samples were 8.3 and 11 ug/L. The site specific objective was not exceeded.

Data Reference:

2007. SWAMP Data for the Owens Hydrologic Unit

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

The site-specific objective for Mammoth Creek at Highway 395 (in Lahontan Basin Plan Table 3-17) applies to this station through the Tributary Rule. It includes an annual average boron concentration of 0.03 mg/L and a 90th percentile value of 0.05 mg/L.

Objective/Criterion Reference:

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

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

One station, "Mammoth Creek at Old Mammoth Road" was sampled.

Temporal Representation:

Four samples were collected approximately quarterly between July 2004 and July 2005.

Environmental Conditions:

Mammoth Creek is a tributary of the Owens River with headwaters near the Sierra Nevada crest. The lower reach of Mammoth Creek is influenced by geothermal springs and is called Hot Creek.

QAPP Information:

The data meet the quality assurance requirements of the SWAMP QAPP.

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 162322, Boron	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

LOE ID:

341166

Pollutant:

Boron

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. Waters shall not contain concentrations of chemical consitituents 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, including irrigation of various types of crops and stock watering. 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 guideline for boron is 700 ug/L (0.7 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: USGS-10265125 (MAMMOTH C A TWIN LAKES NR MAMMOTH LAKES CA).

Temporal Representation:

The samples were collected between the dates of 2018-07-25 and 2021-08-02

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 162322, Boron	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

LOE ID:

341175

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:

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 MUN 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:

Drinking water notification levels are published by the Division of Drinking Water. Notification levels 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 Boron is 1 mg/L.

Guideline Reference:

Drinking Water Notification and Response Levels: An Overview

Spatial Representation:

The samples were collected at 1 monitoring site: USGS-10265125 (MAMMOTH C A TWIN LAKES NR MAMMOTH LAKES CA).

Temporal Representation:

The samples were collected between the dates of 2018-07-25 and 2021-08-02

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 162322, Boron	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

LOE ID:

7206

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 this station approximately quarterly under the Region 6 SWAMP program between July 28, 2004 and July 21, 2004. The concentration of dissolved boron in one of four samples was below the detection level. Another sample was an estimated value. The dissolved boron concentrations in the two remaining samples were 8.3 and 11 ug/L. The criterion was not exceeded.

Data Reference:

2007. SWAMP Data for the Owens Hydrologic Unit

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, "Mammoth Creek at Old Mammoth Road" was sampled.

Temporal Representation:

Four samples were collected approximately quarterly between July 2004 and July 2005.

Environmental Conditions:

Mammoth Creek is a tributary of the Owens River with headwaters near the Sierra Nevada crest. The lower reach of Mammoth Creek is influenced by geothermal springs and is called Hot Creek.

QAPP Information:

The data meet the quality assurance requirements of the SWAMP QAPP.

QAPP Information Reference(s):


DECISION ID	162332	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

Pollutant:	Bromide
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 162332, Bromide	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

LOE ID:

341177

Pollutant:

Bromide

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:

National Academy of Science Health Advisory water quality objective for Bromide is 2300 ug/L.

Guideline Reference:

National Academy of Sciences, Drinking Water and Health, Volume 3 (1980)

Spatial Representation:

The samples were collected at 1 monitoring site: USGS-10265125 (MAMMOTH C A TWIN LAKES NR MAMMOTH LAKES CA).

Temporal Representation:

The samples were collected between the dates of 2019-07-23 and 2019-07-23

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


DECISION ID	163745	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

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:	Pollution

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 163745, Chloride	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

LOE ID:

342793

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 1 samples exceeded the water quality threshold for Chloride

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 Chloride in this water body is 0.8 (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: Mammoth Cr, at Twin Lakes (603MAM008)

Temporal Representation:

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

Environmental Conditions:

QAPP Information:

Generic SWAMP QAPrP

QAPP Information Reference(s):

Generic SWAMP QAPrP

Line of Evidence (LOE) for Decision ID 163745, Chloride	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

LOE ID:

343615

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 USGS California Water Science Center data to determine beneficial use support and results are as follows:
0 of 4 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 0.8 (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: MAMMOTH C A TWIN LAKES NR MAMMOTH LAKES CA (USGS-10265125)

Temporal Representation:

The samples were collected between the dates of 2018-07-25 and 2021-08-02

Environmental Conditions:

QAPP Information:

QAPP Information Reference(s):

QAPP for USGS Data Collected during the 2026 Integrated Report Cycle

Line of Evidence (LOE) for Decision ID 163745, Chloride	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

LOE ID:

8860

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:

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. (No samples were collected in 2002.) Ten chloride samples included one estimated and one below detection level value. Concentrations in the remaining samples ranged from 0.24 to 1.06 mg/L. One of four calculated annual averages was an estimated value; the others were 0.51, 0.60 and 0.69 mg/L. The objective was not exceeded.

Data Reference:

2007. SWAMP Data for the Owens Hydrologic Unit

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

The applicable site-specific objective (from Basin Plan Table 3-17) includes an annual average chloride concentration of 0.8 mg/L and a 90th percentile value of 1.4 mg/L.

Objective/Criterion Reference:

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

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

One station, "Mammoth Creek at Old Mammoth Road" was sampled.

Temporal Representation:

Ten samples each (1 to 4 per year) were collected between 2001 and 2005. No samples were collected in 2002.

Environmental Conditions:

Mammoth Creek is a tributary of the Owens River with headwaters near the Sierra Nevada crest. The lower reach of Mammoth Creek is influenced by geothermal springs and is called Hot Creek.

QAPP Information:

The data meet the quality assurance requirements of the SWAMP QAPP.

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 163745, Chloride	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

LOE ID:

8861

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:

Data Reference:

2007. SWAMP Data for the Owens Hydrologic Unit

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 MCLfor 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, "Mammoth Creek at Old Mammoth Road" was sampled.

Temporal Representation:

Ten samples each (1 to 4 per year) were collected between 2001 and 2005. No samples were collected in 2002.

Environmental Conditions:

Mammoth Creek is a tributary of the Owens River with headwaters near the Sierra Nevada crest. The lower reach of Mammoth Creek is influenced by geothermal springs and is called Hot Creek.

QAPP Information:

The data meet the quality assurance requirements of the SWAMP QAPP.

QAPP Information Reference(s):


DECISION ID	162323	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

Pollutant:	Fluoride
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 162323, Fluoride	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

LOE ID:

341319

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:

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: USGS-10265125 (MAMMOTH C A TWIN LAKES NR MAMMOTH LAKES CA).

Temporal Representation:

The samples were collected between the dates of 2018-07-25 and 2021-08-02

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 162323, Fluoride	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

LOE ID:

341314

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:

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 (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: USGS-10265125 (MAMMOTH C A TWIN LAKES NR MAMMOTH LAKES CA).

Temporal Representation:

The samples were collected between the dates of 2018-07-25 and 2021-08-02

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


DECISION ID	170030	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

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. Six lines of evidence are available in the administrative record to assess this pollutant. Zero of the 60 samples exceed the objective. (Fecal coliform lines of evidence used in previous indicator bacteria decisions in the Lahontan Region have been removed from decisions, starting in the 2026 Integrated Report, because the Lahontan Region's fecal coliform 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. Zero of 60 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 170030, Indicator Bacteria	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

LOE ID:

336844

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 Mammoth Creek (Twin Lakes outlet to Old Mammoth Road) to determine beneficial use support and the results are as follows: 0 of the 5 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:

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): 603MAM014 (Mammoth Creek above Horsecamp).

Temporal Representation:

The samples were collected between the days of 2016-02-04 and 2017-06-28 .

Environmental Conditions:

QAPP Information:

Generic SWAMP QAPrP

QAPP Information Reference(s):

Generic SWAMP QAPrP

Line of Evidence (LOE) for Decision ID 170030, Indicator Bacteria	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

LOE ID:

96929

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 33 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:

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 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, station: 630MAM014

Temporal Representation:

The samples were collected between the days of 2011-15-16 and 2016-07-12 .

Environmental Conditions:

Mammoth Creek is a tributary of the Owens River with headwaters near the Sierra Nevada crest.

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 170030, Indicator Bacteria	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

LOE ID:

99728

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 Mammoth Creek (Twin Lakes outlet to Old Mammoth Road) 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:

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 2 monitoring site(s), station(s): MAM.10, MAM.20

Temporal Representation:

The samples were collected between the days of 2014-05-12 and 2014-05-12 .

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

Line of Evidence (LOE) for Decision ID 170030, Indicator Bacteria	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

LOE ID:

100109

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 Eastern Sierra Ambient Monitoring data for Mammoth Creek (Twin Lakes outlet to Old Mammoth Road) to determine beneficial use support and the results are as follows: 0 of the 13 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 Eastern Sierra Ambient Monitoring.

SWAMP Data:

Non-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 2 monitoring site(s), station(s): MAM.10, MAM.20

Temporal Representation:

The samples were collected between the days of 2012-07-25 and 2013-10-15 .

Environmental Conditions:

QAPP Information:

Quality Assurance Project Plan Sierra Nevada Aquatic Research Laboratory Center for Eastern Sierra Aquatic Microbial Ecology

QAPP Information Reference(s):

Quality Assurance Project Plan Sierra Nevada Aquatic Research Laboratory Center for Eastern Sierra Aquatic Microbial Ecology (SNARL - CESAME)

Line of Evidence (LOE) for Decision ID 170030, Indicator Bacteria	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

LOE ID:

96930

Pollutant:

Escherichia coli (E. coli)

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

GeoMean

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 1 samples exceeded exceeded the geomean water quality standard for E. coli. This is a six week rolling geomean that is calculated weekly.

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 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 six-week rolling GEOMETRIC MEAN (GM) of Escherichia coli (E. coli) not to exceed 100 colony forming units per 100 milliliters (cfu/100 mL) (calculated weekly)

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: 630MAM014

Temporal Representation:

The samples were collected between the days of 2011-15-16 and 2016-07-12 .

Environmental Conditions:

Mammoth Creek is a tributary of the Owens River with headwaters near the Sierra Nevada crest.

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 170030, Indicator Bacteria	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

LOE ID:

336872

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 Mammoth Creek (Twin Lakes outlet to Old Mammoth Road) 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:

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): 603MAM008 (Mammoth Cr, at Twin Lakes).

Temporal Representation:

The samples were collected between the days of 2016-02-04 and 2017-06-28 .

Environmental Conditions:

QAPP Information:

Generic SWAMP QAPrP

QAPP Information Reference(s):

Generic SWAMP QAPrP


DECISION ID	71315	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

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. Two lines of evidence are available in the administrative record to assess this pollutant. Zero of fifteen samples exceed the MUN 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 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 fifteen 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 71315, Nitrate/Nitrite (Nitrite + Nitrate as N)	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

LOE ID:

8845

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. One of 10 samples for nitrite plus nitrate was below the detection level and one was an estimated value. Concentrations in the remaining 8 samples ranged from 0.001 to 0.058 mg/L. the MCL was not exceeded..

Data Reference:

2007. SWAMP Data for the Owens Hydrologic Unit

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 N."

Objective/Criterion Reference:

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

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

One station, "Mammoth Creek at Old Mammoth Road" was sampled.

Temporal Representation:

Ten samples (1 to 4 per year) were collected between 2001 and 2005. No samples were collected in 2002.

Environmental Conditions:

Mammoth Creek is a tributary of the Owens River with headwaters near the Sierra Nevada crest. The lower reach of Mammoth Creek is influenced by geothermal springs and is called Hot Creek.

QAPP Information:

The data meet the quality assurance requirements of the SWAMP QAPP.

QAPP Information Reference(s):


DECISION ID	170072	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

Pollutant:	Nitrogen
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 170072, Nitrogen	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

LOE ID:

343069

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 Upper Owens River Water Quality Project data to determine beneficial use support and results are as follows:
0 of 1 samples exceeded the water quality threshold for Nitrogen, Total

Data Reference:

WQ from the Upper Owens River Water Quality Program for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The Basin Plan objective for Nitrogen, Total in this water body is 0.6 (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: Downstream Twin Lakes Outlet (160TWL010)

Temporal Representation:

The samples were collected between the dates of 2012-06-12 and 2012-09-11

Environmental Conditions:

QAPP Information:

QAPP Information Reference(s):

Quality Assurance Project Plan (QAPP) for Upper Owens River Water Quality Project Data

Line of Evidence (LOE) for Decision ID 170072, Nitrogen	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

LOE ID:

8848

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:

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. (No samples were collected in 2002.) Total nitrogen was calculated from 10 samples each for total Kjeldahl nitrogen (TKN) and nitrite plus nitrate. Two of the calculations were estimated values due to below detection level and estimated values in the basic data. The remainder ranged from 0.100 to 0.258 mg/L total nitrogen. The objective was not exceeded.

Data Reference:

2007. SWAMP Data for the Owens Hydrologic Unit

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

The applicable site-specific objective (from Basin Plan Table 3-17) includes an annual average total nitrogen concentration of 0.6 mg/L and a 90th percentile value of 1.0 mg/L.

Objective/Criterion Reference:

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

Objective/Criterion Reference:

2007. SWAMP Data for the Owens Hydrologic Unit

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

One station, "Mammoth Creek at Old Mammoth Road" was sampled.

Temporal Representation:

Ten samples each (1 to 4 per year) were collected for TKN and nitrite plus nitrate between 2001 and 2005. No samples were collected in 2002.

Environmental Conditions:

Mammoth Creek is a tributary of the Owens River with headwaters near the Sierra Nevada crest. The lower reach of Mammoth Creek is influenced by geothermal springs and is called Hot Creek.

QAPP Information:

The data meet the quality assurance requirements of the SWAMP QAPP.

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 170072, Nitrogen	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

LOE ID:

343049

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 Reference:

WQ from the Upper Owens River Water Quality Program for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The Basin Plan objective for Nitrogen, Total in this water body is 0.6 (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: Upstream from Sherwin St. bridge (South) (160MAM040)

Temporal Representation:

The samples were collected between the dates of 2012-06-12 and 2012-09-11

Environmental Conditions:

QAPP Information:

QAPP Information Reference(s):

Quality Assurance Project Plan (QAPP) for Upper Owens River Water Quality Project Data

Line of Evidence (LOE) for Decision ID 170072, Nitrogen	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

LOE ID:

343135

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:
0 of 1 samples exceeded the water quality threshold for Nitrogen, Total

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 Nitrogen, Total in this water body is 0.6 (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: Mammoth Cr, at Twin Lakes (603MAM008)

Temporal Representation:

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

Environmental Conditions:

QAPP Information:

Generic SWAMP QAPrP

QAPP Information Reference(s):

Generic SWAMP QAPrP


DECISION ID	71206	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

Pollutant:	Nitrogen, Nitrate
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:	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. None of the samples or annual average datapoints exceeds the applicable 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 10 samples samples exceeded the California Maximum Contaminant Level. None of 4 annual average datapoints exceeded the site-specific 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:	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 71206, Nitrogen, Nitrate	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

LOE ID:

8849

Pollutant:

Nitrate

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 this station under the Region 6 SWAMP program between 2001 and 2005. (No samples were collected in 2002.) Nitrate "as N" was calculated from 10 samples each for nitrite and nitrite plus nitrate. The calculations included one below detection level value and one estimated value. Concentrations of nitrate as N in the remaining calculated values ranged from 0 to 0.057 mg/L. When expressed "as nitrate" the maximum value was 0.257 mg/L. The objective was not exceeded.

Data Reference:

2007. SWAMP Data for the Owens Hydrologic Unit

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

The applicable site-specific objective (from Basin Plan Table 3-17) includes an annual average "nitrate as nitrate" concentration of 0.4 mg/L and a 90th percentile value of 0.8 mg/L.

Objective/Criterion Reference:

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

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

One station, "Mammoth Creek at Old Mammoth Road" was sampled.

Temporal Representation:

Ten samples each (1 to 4 per year) were collected for nitrite and nitrite plus nitrate between 2001 and 2005. No samples were collected in 2002.

Environmental Conditions:

Mammoth Creek is a tributary of the Owens River with headwaters near the Sierra Nevada crest. The lower reach of Mammoth Creek is influenced by geothermal springs and is called Hot Creek.

QAPP Information:

The data meet the quality assurance requirements of the SWAMP QAPP.

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 71206, Nitrogen, Nitrate	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

LOE ID:

8851

Pollutant:

Nitrate

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:

Data Reference:

2007. SWAMP Data for the Owens Hydrologic Unit

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 nitrate is 45 mg/L exprssed "as nitrate." This is equivalent to 10 mg/L expressed "as N."

Objective/Criterion Reference:

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

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

One station, "Mammoth Creek at Old Mammoth Road" was sampled.

Temporal Representation:

Ten samples each (1 to 4 per year) were collected for nitrite and nitrite plus nitrate between 2001 and 2005. No samples were collected in 2002.

Environmental Conditions:

Mammoth Creek is a tributary of the Owens River with headwaters near the Sierra Nevada crest. The lower reach of Mammoth Creek is influenced by geothermal springs and is called Hot Creek.

QAPP Information:

The data meet the quality assurance requirements of the SWAMP QAPP.

QAPP Information Reference(s):


DECISION ID	71770	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

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:	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. None of the samples exceeds the California Maximum Contaminant Level (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 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 10 samples exceeded the MCL 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 71770, Nitrogen, Nitrite	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

LOE ID:

8844

Pollutant:

Nitrite as Nitrite NO2

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 this station under the Region 6 SWAMP program between 2001 and 2005. Two of 10 nitrite samples were below the detection level; the remaining samples' nitrite concentrations ranged from 0.001 to 0.002 mg/L. The MCL was not exceeded.

Data Reference:

2007. SWAMP Data for the Owens Hydrologic Unit

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, "Mammoth Creek at Old Mammoth Road" was sampled.

Temporal Representation:

Ten samples (1 to 4 per year) were collected between 2001 and 2005. No samples were collected in 2002.

Environmental Conditions:

Mammoth Creek is a tributary of the Owens River with headwaters near the Sierra Nevada crest. The lower reach of Mammoth Creek is influenced by geothermal springs and is called Hot Creek.

QAPP Information:

The data meet the quality assurance requirements of the SWAMP QAPP.

QAPP Information Reference(s):


DECISION ID	163747	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

Pollutant:	Orthophosphate
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 163747, Orthophosphate	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

LOE ID:

343661

Pollutant:

Orthophosphate

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 USGS California Water Science Center data to determine beneficial use support and results are as follows:
0 of 1 samples exceeded the water quality threshold for OrthoPhosphate 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 OrthoPhosphate as P in this water body is 0.27 (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: MAMMOTH C A TWIN LAKES NR MAMMOTH LAKES CA (USGS-10265125)

Temporal Representation:

The samples were collected between the dates of 2018-07-25 and 2018-07-25

Environmental Conditions:

QAPP Information:

QAPP Information Reference(s):

QAPP for USGS Data Collected during the 2026 Integrated Report Cycle


DECISION ID	162328	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

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:	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 162328, Sodium	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

LOE ID:

341778

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:

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, 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: USGS-10265125 (MAMMOTH C A TWIN LAKES NR MAMMOTH LAKES CA).

Temporal Representation:

The samples were collected between the dates of 2018-07-25 and 2021-08-02

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 162328, Sodium	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

LOE ID:

341791

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:

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:

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: USGS-10265125 (MAMMOTH C A TWIN LAKES NR MAMMOTH LAKES CA).

Temporal Representation:

The samples were collected between the dates of 2018-07-25 and 2021-08-02

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


DECISION ID	170073	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

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	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 170073, Specific Conductivity	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

LOE ID:

340521

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: 603MAM008 (Mammoth Cr, at Twin Lakes).

Temporal Representation:

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

Environmental Conditions:

QAPP Information:

Generic SWAMP QAPrP

QAPP Information Reference(s):

Generic SWAMP QAPrP

Line of Evidence (LOE) for Decision ID 170073, Specific Conductivity	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

LOE ID:

8838

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 sampled this station approximately quarterly under the Region 6 SWAMP program between 2001 and 2005. (No samples were collected in 2002.) Ten field measurements of specific conductance ranged from 62 to 197 uS/cm. An additional two laboratory measurements taken in 2001 were 163 and 194 uS/cm. The MCL was not exceeded.

Data Reference:

2007. SWAMP Data for the Owens Hydrologic Unit

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, "Mammoth Creek at Old Mammoth Road" was sampled.

Temporal Representation:

Ten field measurements were taken approximately quarterly between August 2001 and July 2005. Two additional laboratory measurements were taken in August and November 2001. No measurements were taken in 2002.

Environmental Conditions:

Mammoth Creek is a tributary of the Owens River with headwaters near the Sierra Nevada crest. The lower reach of Mammoth Creek is influenced by geothermal springs and is called Hot Creek.

QAPP Information:

The data meet the quality assurance requirements of the SWAMP QAPP.

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 170073, Specific Conductivity	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

LOE ID:

341876

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: USGS-10265125 (MAMMOTH C A TWIN LAKES NR MAMMOTH LAKES CA).

Temporal Representation:

The samples were collected between the dates of 2018-07-25 and 2022-07-26

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 170073, Specific Conductivity	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

LOE ID:

340366

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:

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: 603MAM014 (Mammoth Creek above Horsecamp).

Temporal Representation:

The samples were collected between the dates of 2021-06-16 and 2021-10-06

Environmental Conditions:

QAPP Information:

Generic SWAMP QAPrP

QAPP Information Reference(s):

Generic SWAMP QAPrP


DECISION ID	162330	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

Pollutant:	Turbidity
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:	Pollution

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. Six lines of evidence are available in the administrative. None of the samples expressed as NTU exceed the Maximum Contaminant level. The Lahontan Basin Plan's narrative turbidity objective is a non-degradation objective, and sample numbers are insufficient to establish baseline conditions or detect trends as required under Listing Policy Section 3.10. Zero samples exceed the objective for the MUN beneficial use. 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. Zero samples expressed as NTU exceeded the Maximum Contaminant Level; 0 samples exceed the objective for the MUN beneficial use and this does not exceed the allowable frequency listed in Table 3.2 of the Listing Policy. These sample sizes are insufficient to determine, with the power and confidence of the Listing Policy, the applicable beneficial use support rating. A minimum of 26 samples per beneficial use assessed 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 162330, Turbidity	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

LOE ID:

8840

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 sampled this station approximately quarterly under the Region 6 SWAMP program between 2001 and 2004. (No samples were collected in 2002.) Turbidity in two of five samples was below the detection level. The remaining samples ranged from 2.1 to 3.2 NTU.

Data Reference:

2007. SWAMP Data for the Owens Hydrologic Unit

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

The Lahontan Basin Plan's regionwide turbidity objective 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, "Mammoth Creek at Old Mammoth Road" was sampled.

Temporal Representation:

Five turbidity measurements expressed as NTU were taken between 2001 and 2004. No measurements were taken in 2002.

Environmental Conditions:

QAPP Information:

The data meet the quality assurance requirements of the SWAMP QAPP.

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 162330, Turbidity	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

LOE ID:

8841

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:

Data Reference:

2007. SWAMP Data for the Owens Hydrologic Unit

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, "Mammoth Creek at Old Mammoth Road" was sampled.

Temporal Representation:

Five turbidity measurements expressed as NTU were taken between 2001 and 2004. No measurements were taken in 2002.

Environmental Conditions:

QAPP Information:

The data meet the quality assurance requirements of the SWAMP QAPP.

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 162330, Turbidity	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

LOE ID:

8843

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 as NTRU quarterly under the Region 6 SWAMP program between 2004 and 2005. All four samples were below the detection level.

Data Reference:

2007. SWAMP Data for the Owens Hydrologic Unit

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

The drinking water Maximum Contaminant Level is expressed as NTU. There are no standards or criteria for turbidity as NTRU 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, "Mammoth Creek at Old Mammoth Road" was sampled.

Temporal Representation:

Four quarterly turbidity measurements expressed as NTRU were taken in 2004 and 2005.

Environmental Conditions:

QAPP Information:

The data meet the quality assurance requirements of the SWAMP QAPP.

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 162330, Turbidity	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

LOE ID:

97307

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 TMDL Intergrated Report Special Study data for Mammoth Creek (Twin Lakes outlet to Old Mammoth Road) to determine beneficial use support and results are as follows: 0 of 2 samples exceeded the water quality standard for Turbidity.

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:

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(s) (603MAM014)

Temporal Representation:

The samples were collected between the dates of 2015-09-14 and 2015-11-12

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

Line of Evidence (LOE) for Decision ID 162330, Turbidity	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

LOE ID:

340821

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, 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 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: 603MAM008 (Mammoth Cr, at Twin Lakes).

Temporal Representation:

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

Environmental Conditions:

QAPP Information:

Generic SWAMP QAPrP

QAPP Information Reference(s):

Generic SWAMP QAPrP

Line of Evidence (LOE) for Decision ID 162330, Turbidity	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

LOE ID:

8842

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 as NTRU quarterly under the Region 6 SWAMP program between 2004 and 2005. All four samples were below the detection level.

Data Reference:

2007. SWAMP Data for the Owens Hydrologic Unit

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, "Mammoth Creek at Old Mammoth Road" was sampled.

Temporal Representation:

Four quarterly turbidity measurements expressed as NTRU were taken in 2004 and 2005.

Environmental Conditions:

QAPP Information:

The data meet the quality assurance requirements of the SWAMP QAPP.

QAPP Information Reference(s):


DECISION ID	162327	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

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:	Regional Board Conclusion: This pollutant was considered for placement on the section 303(d) list in a previous listing cycle. The Lahontan Basin Plan's narrative pH objective is an antidegradation-based objective that requires that there be no change greater than 0.5 pH units in waters designated for the Cold Freshwater Habitat (COLD) or Warm Freshwater Habitat beneficial uses. 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. Nine lines of evidence are available to support this decision. Zero samples exceed the pH standard for COLD.

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:

Line of Evidence (LOE) for Decision ID 162327, pH	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

LOE ID:

339860

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 SWAMP RWB6 Monitoring data for Mammoth Creek (Twin Lakes outlet to Old Mammoth Road) 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, 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 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: 603MAM008 (Mammoth Cr, at Twin Lakes).

Temporal Representation:

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

Environmental Conditions:

QAPP Information:

Generic SWAMP QAPrP

QAPP Information Reference(s):

Generic SWAMP QAPrP

Line of Evidence (LOE) for Decision ID 162327, pH	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

LOE ID:

341661

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 USGS California Water Science Center data for Mammoth Creek (Twin Lakes outlet to Old Mammoth Road) to determine beneficial use support and results are as follows: 0 of 3 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: USGS-10265125 (MAMMOTH C A TWIN LAKES NR MAMMOTH LAKES CA).

Temporal Representation:

The samples were collected between the dates of 2020-07-28 and 2022-07-26

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 162327, pH	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

LOE ID:

348115

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 2007 RWB6 SWAMP Owens Hydrologic Unit data for Mammoth Creek (Twin Lakes outlet to Old Mammoth Road) to determine beneficial use support and results are as follows: 0 of 8 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 Owens Hydrologic Unit

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: 603MAM007 (Mammoth Cr, at Old Mammoth Rd).

Temporal Representation:

The samples were collected between the dates of 2001-08-15 and 2005-07-21

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 162327, pH	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

LOE ID:

348120

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:

2007. SWAMP Data for the Owens Hydrologic Unit

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: 603MAM007 (Mammoth Cr, at Old Mammoth Rd).

Temporal Representation:

The samples were collected between the dates of 2001-08-15 and 2005-07-21

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 162327, pH	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

LOE ID:

339542

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 Mammoth Creek (Twin Lakes outlet to Old Mammoth Road) to determine beneficial use support and results are as follows: 0 of 5 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, 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:

Spatial Representation:

The samples were collected at 1 monitoring site: 603MAM014 (Mammoth Creek above Horsecamp).

Temporal Representation:

The samples were collected between the dates of 2021-06-16 and 2021-10-06

Environmental Conditions:

QAPP Information:

Generic SWAMP QAPrP

QAPP Information Reference(s):

Generic SWAMP QAPrP

Line of Evidence (LOE) for Decision ID 162327, pH	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

LOE ID:

339858

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:

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:

Spatial Representation:

The samples were collected at 1 monitoring site: 603MAM008 (Mammoth Cr, at Twin Lakes).

Temporal Representation:

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

Environmental Conditions:

QAPP Information:

Generic SWAMP QAPrP

QAPP Information Reference(s):

Generic SWAMP QAPrP

Line of Evidence (LOE) for Decision ID 162327, pH	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

LOE ID:

341723

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: USGS-10265125 (MAMMOTH C A TWIN LAKES NR MAMMOTH LAKES CA).

Temporal Representation:

The samples were collected between the dates of 2020-07-28 and 2022-07-26

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 162327, pH	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

LOE ID:

8839

Pollutant:

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 this station approximately quarterly under the Region 6 SWAMP program between 2001 and 2005. (No samples were collected in 2002.) The range of pH in 8 field measurements was 7.5 to 8.4 units. An additional two laboratory measurements were 8 and 7.8 units. There are insufficient data to document natural background conditions or to detect trends.

Data Reference:

2007. SWAMP Data for the Owens Hydrologic Unit

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

The regionwide water quality objective for pH in the Lahontan Basin Plan 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:

One station, "Mammoth Creek at Old Mammoth Road" was sampled.

Temporal Representation:

Eight field pH measurements were taken approximately quarterly between August 2001 and July 2005. No measurements were taken in 2002. An additional two laboratory measurements were taken in August and November 2001.

Environmental Conditions:

QAPP Information:

The data meet the quality assurance requirements of the SWAMP QAPP.

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 162327, pH	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

LOE ID:

339512

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 SWAMP RWB6 Monitoring data for Mammoth Creek (Twin Lakes outlet to Old Mammoth Road) to determine beneficial use support and results are as follows: 0 of 5 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, 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:

Spatial Representation:

The samples were collected at 1 monitoring site: 603MAM014 (Mammoth Creek above Horsecamp).

Temporal Representation:

The samples were collected between the dates of 2021-06-16 and 2021-10-06

Environmental Conditions:

QAPP Information:

Generic SWAMP QAPrP

QAPP Information Reference(s):

Generic SWAMP QAPrP


DECISION ID	162324	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

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. Four lines of evidence, two for COLD and two for MUN, are available in the administrative record to assess this pollutant. Zero of the 14 samples exceed the objective for COLD beneficial use, and three of the 14 samples exceed the objective for the MUN beneficial use. Based on the readily available data and information, the weight of evidence indicates that there is sufficient justification in favor of placing this water segment-pollutant combination on the CWA section 303(d) List. This conclusion is based on the staff findings that: 1. The data used satisfies the data quality requirements of section 6.1.4 of the Policy. 2. The data used satisfies the data quantity requirements of section 6.1.5 of the Policy. 3. Three of the 14 samples exceed the objective for the MUN beneficial use, and this exceeds the allowable frequency listed in Table 3.1 of the Listing Policy. 4. Pursuant to section 3.11 of the Listing Policy, no additional data and information are available indicating that standards are not met.

Regional Board Decision Recommendation:	After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should be placed on the section 303(d) list because applicable water quality standards are exceeded and a pollutant contributes to or causes the problem.

State Board Review of Regional Board Conclusion and Recommendation:

State Board Decision Recommendation:

Line of Evidence (LOE) for Decision ID 162324, Iron	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

LOE ID:

7216

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 this station under the Region 6 SWAMP program between 2001 and 2005.
Total recoverable iron concentrations in 10 samples ranged from 80 to 400 ug/L. Three samples exceeded the California MCL.

Data Reference:

2007. SWAMP Data for the Owens Hydrologic Unit

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 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, "Mammoth Creek at Old Mammoth Road" was sampled.

Temporal Representation:

Ten samples were collected approximately quarterly between 2001 and 2005.

Environmental Conditions:

Mammoth Creek is a tributary of the Owens River with headwaters near the Sierra Nevada crest. The lower reach of Mammoth Creek is influenced by geothermal springs and is called Hot Creek.

QAPP Information:

The data meet the quality assurance requirements of the SWAMP QAPP.

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 162324, Iron	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

LOE ID:

341360

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:

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: USGS-10265125 (MAMMOTH C A TWIN LAKES NR MAMMOTH LAKES CA).

Temporal Representation:

The samples were collected between the dates of 2018-07-25 and 2021-08-02

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 162324, Iron	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

LOE ID:

341358

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: USGS-10265125 (MAMMOTH C A TWIN LAKES NR MAMMOTH LAKES CA).

Temporal Representation:

The samples were collected between the dates of 2018-07-25 and 2021-08-02

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 162324, Iron	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

LOE ID:

7215

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 this station under the Region 6 SWAMP program approximately quarterly between 2001 and 2005. Dissolved iron concentrations in 10 samples ranged from 15 to 115 ug/L. The criterion was not exceeded.

Data Reference:

2007. SWAMP Data for the Owens Hydrologic Unit

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, "Mammoth Creek at Old Mammoth Road" was sampled.

Temporal Representation:

Ten samples were collected approximately quarterly between 2001 and 2005.

Environmental Conditions:

QAPP Information:

The data meet the quality assurance requirements of the SWAMP QAPP.

QAPP Information Reference(s):


DECISION ID	162326	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

Pollutant:	Oxygen, Dissolved
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. Five lines of evidence are available in the administrative record to assess this parameter: 3 which assess dissolved oxygen concentration data and 2 which assess dissolved oxygen percent saturation data. Three of 15 samples are below the objective for minimum dissolved oxygen concentration. Five of 6 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 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. Five of 6 samples are below the objective for minimum dissolved oxygen percent saturation, 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 162326, Oxygen, Dissolved	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

LOE ID:

339376

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 Mammoth Creek (Twin Lakes outlet to Old Mammoth Road) to determine beneficial use support and results are as follows: 5 of 5 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: 603MAM014 (Mammoth Creek above Horsecamp).

Temporal Representation:

The samples were collected between the dates of 2021-06-16 and 2021-10-06

Environmental Conditions:

QAPP Information:

Generic SWAMP QAPrP

QAPP Information Reference(s):

Generic SWAMP QAPrP

Line of Evidence (LOE) for Decision ID 162326, Oxygen, Dissolved	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

LOE ID:

339192

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:

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: 603MAM008 (Mammoth Cr, at Twin Lakes).

Temporal Representation:

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

Environmental Conditions:

QAPP Information:

Generic SWAMP QAPrP

QAPP Information Reference(s):

Generic SWAMP QAPrP

Line of Evidence (LOE) for Decision ID 162326, Oxygen, Dissolved	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

LOE ID:

339410

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:

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: 603MAM008 (Mammoth Cr, at Twin Lakes).

Temporal Representation:

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

Environmental Conditions:

QAPP Information:

Generic SWAMP QAPrP

QAPP Information Reference(s):

Generic SWAMP QAPrP

Line of Evidence (LOE) for Decision ID 162326, Oxygen, Dissolved	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

LOE ID:

339199

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:

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:

Spatial Representation:

The samples were collected at 1 monitoring site: 603MAM014 (Mammoth Creek above Horsecamp).

Temporal Representation:

The samples were collected between the dates of 2021-06-16 and 2021-10-06

Environmental Conditions:

QAPP Information:

Generic SWAMP QAPrP

QAPP Information Reference(s):

Generic SWAMP QAPrP

Line of Evidence (LOE) for Decision ID 162326, Oxygen, Dissolved	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

LOE ID:

7178

Pollutant:

Oxygen, Dissolved

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 this station under the Region 6 SWAMP program approximately quarterly between 2001 and 2005. The dissolved oxygen concentrations in 9 samples ranged from 6.5 to 10.7 mg/L. Three samples were below the 8 mg/L minimum concentration.

Data Reference:

2007. SWAMP Data for the Owens Hydrologic Unit

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

The objective, from Lahontan Basin Plan Table 3-6, is a one- day minimum dissolved oxygen concentration of 8 mg/L.

Objective/Criterion Reference:

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

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

One station, "Mammoth Creek at Old Mammoth Road" was sampled.

Temporal Representation:

Nine samples were collected approximately quarterly between August 2001 and July 2005. No samples were collected in 2002.

Environmental Conditions:

QAPP Information:

The data meet the quality assurance requirements of the SWAMP QAPP.

QAPP Information Reference(s):


DECISION ID	77004	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

Pollutant:	Metals
Final Listing Decision:	Delist from 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	Delist from 303(d) list (TMDL required list)(2016)
Revision Status	Original
Reason for Delisting:	Change from general pollutant to specific pollutant listing (e.g. metals to copper)
Impairment from Pollutant or Pollution:	Pollutant

Regional Board Conclusion:	Regional Board Conclusion: This pollutant was considered for removal 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: Mammoth Creek as a whole was listed for "Metals" in the early 1990s on the basis of fish tissue data from the State Water Resources Control Board's Toxic Substances Monitoring Program (TSMP). The TSMP results included "Elevated Data Levels" (EDLs) for several metals. EDLs were statistically high compared to other data statewide, but did not exceed human fish consumption criteria, including the then-applicable OEHHA criteria. In 1998 the State Water Board provided the opportunity to remove listings for TSMP data that did not exceed human consumption criteria. Mammoth Creek was not recommended to be delisted for "Metals" at the time because Lahontan Water Board staff wanted to investigate stormwater impacts on the creek. In 2006, the State Water Board listed Mammoth Creek as a whole for mercury due to exceedance of the newer OEHHA "screening value" for tissue. State Board staff did not identify exceedances of human consumption criteria for other metals. For the 2008 assessment cycle, Mammoth Creek has been divided into three segments. No additional new listings for specific metals are being recommended on the basis of tissue or water data. The general "metals" listing for the creek as a whole is not recommended to be carried over to this segment because a specific listing for mercury is in place.

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 77004, Metals	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

LOE ID:

6964

Pollutant:

Metals

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:

Guideline Reference:

Spatial Representation:

Unspecified

Temporal Representation:

Unspecified

Environmental Conditions:

Unspecified

QAPP Information:

Unspecified

QAPP Information Reference(s):


DECISION ID	162331	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

Pollutant:	Alkalinity as CaCO3
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 162331, Alkalinity as CaCO3	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

LOE ID:

337888

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: 603MAM014 (Mammoth Creek above Horsecamp).

Temporal Representation:

The samples were collected between the dates of 2021-06-16 and 2021-10-06

Environmental Conditions:

QAPP Information:

Generic SWAMP QAPrP

QAPP Information Reference(s):

Generic SWAMP QAPrP

Line of Evidence (LOE) for Decision ID 162331, Alkalinity as CaCO3	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

LOE ID:

337959

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: 603MAM008 (Mammoth Cr, at Twin Lakes).

Temporal Representation:

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

Environmental Conditions:

QAPP Information:

Generic SWAMP QAPrP

QAPP Information Reference(s):

Generic SWAMP QAPrP

Line of Evidence (LOE) for Decision ID 162331, Alkalinity as CaCO3	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

LOE ID:

341019

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:

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 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: USGS-10265125 (MAMMOTH C A TWIN LAKES NR MAMMOTH LAKES CA).

Temporal Representation:

The samples were collected between the dates of 2018-07-25 and 2022-07-26

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


DECISION ID	71155	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

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

Regional Board Conclusion:	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 exceeds the applicable criteria and 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 10 dissolved antimony samples exceeded the federal aquatic life criteria. None of 10 total antimony samples exceeded the California 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 71155, Antimony	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

LOE ID:

7233

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 this station under the Region 6 SWAMP program approximately quarterly between 2001 and 2005. Concentrations of dissolved antimony were below detection level in 8 of 10 samples. One sample was an estimated value and the antimony concentration in the remaining sample was 0.1 ug/L.. The criteria were not violated.

Data Reference:

2007. SWAMP Data for the Owens Hydrologic Unit

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:

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, "Mammoth Creek at Old Mammoth Road" was sampled.

Temporal Representation:

Ten samples were collected approximately quarterly between 2001 and 2005.

Environmental Conditions:

QAPP Information:

The data meet the quality assurance requirements of the SWAMP QAPP.

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 71155, Antimony	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

LOE ID:

7234

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 this station under the Region 6 SWAMP program approximately quarterly between 2001 and 2005. All of 10 samples for total antimony were below the detection level. Under Section 6.1.5.5 of the Listing Policy, the MCL is considered to be attained.

Data Reference:

2007. SWAMP Data for the Owens Hydrologic Unit

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 antimony is 6 ug/L.

Objective/Criterion Reference:

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

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

One station, "Mammoth Creek at Twin Lakes" was sampled.

Temporal Representation:

Ten samples were collected approximately quarterly between 2001 and 2005.

Environmental Conditions:

Mammoth Creek is a tributary of the Owens River with headwaters near the Sierra Nevada crest. The lower reach of Mammoth Creek is influenced by geothermal springs and is called Hot Creek.

QAPP Information:

The data meet the quality assurance requirements of the SWAMP QAPP.

QAPP Information Reference(s):


DECISION ID	71205	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

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

Regional Board Conclusion:	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. There are no applicable standards or criteria for dissolved beryllium. None of the total beryllium samples exceeds the California Maximum Contaminant Level. 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 the total beryllium samples exceeded the California 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 71205, Beryllium	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

LOE ID:

7203

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 this station under the Region 6 SWAMP program approximately quarterly between 2001 and 2005. Concentrations of dissolved beryllium in 10 quarterly samples were below the detection level.

Data Reference:

2007. SWAMP Data for the Owens Hydrologic Unit

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

There are no state or federal standards or criteria for dissolved beryllium 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, "Mammoth Creek at Old Mammoty Road" was sampled.

Temporal Representation:

Ten samples (1 to 4 per year) were collected between 2001 and 2005. No samples were collected in 2002.

Environmental Conditions:

QAPP Information:

The data meet the quality assurance requirements of the SWAMP QAPP.

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 71205, Beryllium	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

LOE ID:

7204

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 this station approximately quarterly under the Region 6 SWAMP program between 2001 and 2005. Concentrations of total beryllium in 9 of 10 samples were below the detection level. The tenth sample was an estimated value.

Data Reference:

2007. SWAMP Data for the Owens Hydrologic Unit

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 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, "Mammoth Creek at Old Mammoth Road" was sampled.

Temporal Representation:

Ten samples 1 to 4 per year) were collected between 2001 and 2005. No samples were collected in 2002.

Environmental Conditions:

Mammoth Creek is a tributary of the Owens River with headwaters near the Sierra Nevada crest. The lower reach of Mammoth Creek is influenced by geothermal springs and is called Hot Creek.

QAPP Information:

The data meet the quality assurance requirements of the SWAMP QAPP.

QAPP Information Reference(s):


DECISION ID	71764	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

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

Regional Board Conclusion:	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 for total or dissolved cadmium exceeds the applicable standard. 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. 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 10 dissolved cadmium samples exceeded the California Toxics Rule standards. None of 10 total cadmium samples exceeded the California 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 71764, Cadmium	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

LOE ID:

7208

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:

The U.S. Geological Survey sampled this station approximately quarterly under the Region 6 SWAMP program between 2001 and 2005. Concentrations of total cadmium in 9 of 10 samples were below the detection level. A tenth sample was an estimated value. The MCL was not exceeded.

Data Reference:

2007. SWAMP Data for the Owens Hydrologic Unit

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 MCL for cadmium is 5 ug/L.

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

One station, "Mammoth Creek at Old Mammoth Road" was sampled.

Temporal Representation:

Ten samples (1 to 4 per year) were collected between 2001 and 2005. No samples were collected in 2002.

Environmental Conditions:

Mammoth Creek is a tributary of the Owens River with headwaters near the Sierra Nevada crest. The lower reach of Mammoth Creek is influenced by geothermal springs and is called Hot Creek.

QAPP Information:

The data meet the quality assurance requirements of the SWAMP QAPP.

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 71764, Cadmium	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

LOE ID:

7207

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:

Fixed station physical/chemical (conventional plus toxic pollutants)

Data Used to Assess Water Quality:

The U.S. Geological Survey sampled this station approximately quarterly under the Region 6 SWAMP program between 2001 and 2005. Concentrations of dissolved cadmium in 10 samples were all below the detection level. Per listing policy Section 6.1.5.5 the California Toxics Rule standards are assumed to be attained.

Data Reference:

2007. SWAMP Data for the Owens Hydrologic Unit

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

The California Toxics Rule freshwater aquatic life standards for cadmium are dependent on hardness. At the hardness levels reported for this station, the acute toxicity standard ranges from 0.74 to 2.96 ug/L. The chronic toxicity standard ranges from 0.66 to 1.74 ug/L.

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

One station, "Mammoth Creek at Old Mammoth Road" was sampled.

Temporal Representation:

Twelve samples (1 to 4 per year) were collected between 2001 and 2005. No samples were collected in 2002.

Environmental Conditions:

QAPP Information:

The data meet the quality assurance requirements of the SWAMP QAPP.

QAPP Information Reference(s):


DECISION ID	71938	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

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:	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 applicable California or federal standards or 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 do not 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 using 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 71938, Calcium	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

LOE ID:

7195

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 this station under the Region 6 SWAMP program approximately quarterly between 2001 and 2005. Concentrations of total calcium in 10 samples ranged from 5.14 to 17.4 mg/L.

Data Reference:

2007. SWAMP Data for the Owens Hydrologic Unit

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

There are no California or federal water quality standards or criteria for calcium. It is generally monitored as a component of another water quality parameter such as hardness, Total Dissolved Solids, or Sodium Adsorption Ratio.

Objective/Criterion Reference:

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

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

One station, "Mammoth Creek at Old Mammoth Road" was sampled.

Temporal Representation:

Ten quarterly samples were collected between August 2001 and July 2005.

Environmental Conditions:

Mammoth Creek is a tributary of the Owens River with headwaters near the Sierra Nevada crest. The lower reach of Mammoth Creek is influenced by geothermal springs and is called Hot Creek.

QAPP Information:

The data meet the quality assurance requirements of the SWAMP QAPP.

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 71938, Calcium	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

LOE ID:

7194

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 this station under the Region 6 SWAMP program approximately quarterly between 2001 and 2005. Concentrations of dissolved calcium in 10 samples ranged from 5.88 to 16.4 mg/L.

Data Reference:

2007. SWAMP Data for the Owens Hydrologic Unit

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, "Mammoth Creek at Old Mammoth Road" was sampled.

Temporal Representation:

Ten quarterly samples were collected between August 2000 and July 2005.

Environmental Conditions:

QAPP Information:

The data meet the quality assurance requirements of the SWAMP QAPP.

QAPP Information Reference(s):


DECISION ID	78811	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

Pollutant:	Chlorpyrifos
Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)(2016)
Revision Status	Original
Impairment from Pollutant or Pollution:	Pollutant

Regional Board Conclusion:	This pollutant is being considered for placement on the section 303(d) list under section 3.1 of the Listing Policy. Under section 3.1 a single line of evidence are is necessary to assess listing status. One line of evidence is available in the administrative record to assess this pollutant; however, the result was not used in the assessment because the laboratory method detection limit was above the guideline and the result was non-detect. Therefore the results could not be used to determine if the sample results exceeded the water quality guidelines. 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. The result was not used in the assessment because the laboratory method detection limit was above the guideline so compliance with the guideline could not be determined. This sample size is insufficient to determine with the power and confidence of the Listing Policy if standards are not met. A minimum of 16 samples is needed for application of 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:	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 78811, Chlorpyrifos	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

LOE ID:

44367

Pollutant:

Chlorpyrifos

LOE Subgroup:

Pollutant-Sediment

Matrix:

Sediment

Fraction:

Total

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

One sample result was not used in the assessment because the laboratory method detection limit was above the guideline and the result was non-detect. Therefore the results could not be quantified with the level of certainty required by the Listing Policy.

Data Reference:

Statewide Project Urban Pyrethroid Status Monitoring

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

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

Evaluation Guideline:

There is no chlorpyrifos evaluation guideline specific to "sediment, interstitial water" (pore water). The following evaluation guideline was used to evaluate an exceedance in water quality standards: the freshwater criterion continuous concentration to protect aquatic organisms is 0.015 ug/L (Siepmann and Finlayson 2000, with minor corrections to significant figures as described in Beaulaurier et al., 2005).

Guideline Reference:

Water quality criteria for diazinon and chlorpyrifos. Administrative Report 00-3. Rancho Cordova, CA: Pesticide Investigations Unit, Office of Spills and Response. CA Department of Fish and Game (with minor corrections to significant figures as described in Beaulaurier et al., 2005).

Spatial Representation:

Data for this line of evidence for Mammoth Creek (Twin Lakes outlet to Old Mammoth Road) was collected at 1 monitoring site [ Mammoth Ck @ Minaret - 603SUP028]

Temporal Representation:

Data was collected on a single day 10/30/2006.

Environmental Conditions:

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

QAPP Information:

The SWAMP QAPP (2008) was followed.

QAPP Information Reference(s):

Surface Water Ambient Monitoring Program Quality Assurance Program Plan


DECISION ID	72111	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

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:	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 exceeds the applicable water quality standard(s). 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 10 dissolved chromium samples exceeded the California Toxics Rule standards. None of 10 total chromium samples exceeded the California 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 72111, Chromium (total)	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

LOE ID:

7210

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 U.S. Geological Survey sampled this station under the Region 6 SWAMP program between 2001 and 2005. Concentrations of total chromium in 10 quarterly samples were all below the detection level. Per listing policy Section 6.1.5.5 the California Toxics Rule standards are assumed to be attained.

Data Reference:

2007. SWAMP Data for the Owens Hydrologic Unit

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, "Mammoth Creek at Twin Lakes" was sampled.

Temporal Representation:

Ten samples were collected approximately quarterly between 2001 and 2005.

Environmental Conditions:

Mammoth Creek is a tributary of the Owens River with headwaters near the Sierra Nevada crest. The lower reach of Mammoth Creek is influenced by geothermal springs and is called Hot Creek.

QAPP Information:

The data meet the quality assurance requirements of the SWAMP QAPP.

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 72111, Chromium (total)	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

LOE ID:

7209

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 U.S. Geological Survey sampled this station under the Region 6 SWAMP program between 2001 and 2005. Concentrations of dissolved chromium in 10 samples were all below the detection level. Per listing policy Section 6.1.5.5 the California Toxics Rule standards are assumed to be attained.

Data Reference:

2007. SWAMP Data for the Owens Hydrologic Unit

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

The California Toxics Rule freshwater aquatic life standards for chromium VI are: 4-day average = 11 ug/L; 1 hour average = 16 ug/L). The chromium III standards are hardness dependent. At the hardness levels reported for this station, the acute toxicity standard ranges from 153.50 to 421.35 ug/L. The chronic toxicity standard ranges from 49.80 to 136.68.

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

One station, "Mammoth Creek at Twin Lakes" was sampled.

Temporal Representation:

Ten samples (1 to 4 per year) were collected between 2001 and 2005. No samples were collected in 2008.

Environmental Conditions:

QAPP Information:

The data meet the quality assurance requirements of the SWAMP QAPP.

QAPP Information Reference(s):


DECISION ID	72446	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

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

Regional Board Conclusion:	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. There are no applicable California or federal water quality standards or criteria for cobalt. 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. Quarterly samples do not capture the seasonal and annual variability expected in streamflows and constituent concentrations in streams of the Lahontan Region. 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 or criteria 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 72446, Cobalt	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

LOE ID:

7212

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 this station under the Region 6 SWAMP program approximately quarterly between 2001 and 2005. Concentrations of dissolved cobalt in 10 samples ranged from 0.033 to 0.091 ug/L.

Data Reference:

2007. SWAMP Data for the Owens Hydrologic Unit

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

There are no California or federal water quality standards or criteria for cobalt for the protection of aquatic life.

Objective/Criterion Reference:

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

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

One station, "Mammoth Creek at Old Mammoth Road" was sampled.

Temporal Representation:

Ten samples (1 to 4 per year) were collected between August 2001 and July 2005. No samples were collected in 2002.

Environmental Conditions:

QAPP Information:

The data meet the quality assurance requirements of the SWAMP QAPP.

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 72446, Cobalt	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

LOE ID:

7211

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 this station under the Region 6 SWAMP program approximately quarterly between 2001 and 2005. Concentrations of total cobalt in 2 of 10 samples were below the detection level. Concentrations in the remaining 8 samples ranged from 0.097 to0.259 ug/L.

Data Reference:

2007. SWAMP Data for the Owens Hydrologic Unit

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

There are no California or federal water quality 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, "Mammoth Creek at Old Mammoth Road" was sampled.

Temporal Representation:

Ten samples were collected approximately quarterly between August 2001 and July 2005.

Environmental Conditions:

Mammoth Creek is a tributary of the Owens River with headwaters near the Sierra Nevada crest. The lower reach of Mammoth Creek is influenced by geothermal springs and is called Hot Creek.

QAPP Information:

The data meet the quality assurance requirements of the SWAMP QAPP.

QAPP Information Reference(s):


DECISION ID	72337	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

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

Regional Board Conclusion:	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 dissolved copper or total copper samples exceeds the applicable standard(s). 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 10 dissolved copper samples exceeded the California Toxics Rules standards. None of 10 total copper samples exceeded. the California Maximum Contaminant Level. 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 72337, Copper	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

LOE ID:

7213

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 this station under the Region 6 SWAMP program approximately quarterly between 2001 and 2005. Of 10 samples for dissolved copper, 4 were below the detection level, 4 were estimated values, and dissolved copper concentrations in the remaining samples were 0.3 and 0.9 ug/L. The CTR standards were not violated

Data Reference:

2007. SWAMP Data for the Owens Hydrologic Unit

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

The California Toxics Rule freshwater aquatic life standards for copper are dependent on hardness. At the hardness levels reported for this station, the acute toxicity standard ranges from 3.10 to 9.92 ug/L, and the chronic toxicity standard ranges from 2.27 to 6.80 ug/L

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

One station, "Mammoth Creek at Old Mammoth Road" was sampled.

Temporal Representation:

Ten samples were collected approximately quarterly between 2001 and 2005.

Environmental Conditions:

QAPP Information:

The data meet the quality assurance requirements of the SWAMP QAPP.

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 72337, Copper	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

LOE ID:

7214

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 this station approximately quarterly under the Region 6 SWAMP program between 2001 and 2005. Concentrations of total recoverable copper in 3 of 10 samples were below the detection level. Another three samples were estimated values. Concentrations of total copper in the remaining samples ranged from 0.7 to 1.0 ug/L. The MCLs were not exceeded.

Data Reference:

2007. SWAMP Data for the Owens Hydrologic Unit

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 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, "Mammoth Creek at Old Mammoth Road" was sampled.

Temporal Representation:

Ten samples were collected approximately quarterly between 2001 and 2005.

Environmental Conditions:

Mammoth Creek is a tributary of the Owens River with headwaters near the Sierra Nevada crest. The lower reach of Mammoth Creek is influenced by geothermal springs and is called Hot Creek.

QAPP Information:

The data meet the quality assurance requirements of the SWAMP QAPP.

QAPP Information Reference(s):


DECISION ID	78859	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

Pollutant:	Diazinon
Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)(2016)
Revision Status	Original
Impairment from Pollutant or Pollution:	Pollutant

Regional Board Conclusion:	This pollutant is being considered for placement on the section 303(d) list under section 3.1 of the Listing Policy. Under section 3.1 a single line of evidence is necessary to assess listing status. One line of evidence is available in the administrative record to assess this pollutant. None of the sample 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 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. 3. None of the sample exceeded the guideline 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 16 samples is needed for application of 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:	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 78859, Diazinon	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

LOE ID:

44385

Pollutant:

Diazinon

LOE Subgroup:

Pollutant-Sediment

Matrix:

Sediment

Fraction:

Total

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed SWAMP data for Mammoth Creek (Twin Lakes outlet to Old Mammoth Road) to determine beneficial use support and results are as follows: 0 of 1 samples exceed the criterion for Diazinon.

Data Reference:

Statewide Project Urban Pyrethroid Status Monitoring

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

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

Evaluation Guideline:

There is no diazinon evaluation guideline specific to "sediment, interstitial water" (pore water). The following evaluation guideline was used to evaluate an exceedance in water quality standards: 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:

Data for this line of evidence for Mammoth Creek (Twin Lakes outlet to Old Mammoth Road) was collected at 1 monitoring site [ Mammoth Ck @ Minaret - 603SUP028]

Temporal Representation:

Data was collected on a single day 10/30/2006.

Environmental Conditions:

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

QAPP Information:

The SWAMP QAPP (2008) was followed.

QAPP Information Reference(s):

Surface Water Ambient Monitoring Program Quality Assurance Program Plan


DECISION ID	71464	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

Pollutant:	Dissolved oxygen saturation
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:	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. One line of evidence is available in the administrative record to assess this pollutant. None 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 diel, seasonal and annual variability expected in streamflows and dissolved oxygen concentrations in streams of the Lahontan Region. 3. None of 8 samples exceeded the water quality 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:	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 71464, Dissolved oxygen saturation	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

LOE ID:

7180

Pollutant:

Dissolved oxygen saturation

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 this station under the Region 6 SWAMP program approximately quarterly between 2003 and 2005. Percent saturation of dissolved oxygen ranged from 96 to 107 percent. The objective was not violated.

Data Reference:

2007. SWAMP Data for the Owens Hydrologic Unit

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, "Mammoth Creek at Old Mammoth Road" was sampled.

Temporal Representation:

Eight samples were collected approximately quarterly between October 2003 and July 2005.

Environmental Conditions:

QAPP Information:

The data meet the quality assurance requirements of the SWAMP QAPP.

QAPP Information Reference(s):


DECISION ID	71525	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

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:	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 for hardness. 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 water quality 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 71525, Hardness as CaCO3	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

LOE ID:

8858

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 this station approximately quarterly under the Region 6 SWAMP program between 2001 and 2005. (No samples were collected in 2002.) Hardness in 10 samples ranged from 21.11 to 72.43 mg/L CaCO3.

Data Reference:

2007. SWAMP Data for the Owens Hydrologic Unit

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 CaC03/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, "Mammoth Creek at Old Mammoth Road" was sampled.

Temporal Representation:

Ten samples (1 to 4 per year) were collected between 2001 and 2005. No samples were collected in 2002.

Environmental Conditions:

Mammoth Creek is a tributary of the Owens River with headwaters near the Sierra Nevada crest. The lower reach of Mammoth Creek is influenced by geothermal springs and is called Hot Creek.

QAPP Information:

The data meet the quality assurance requirements of the SWAMP QAPP.

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 71525, Hardness as CaCO3	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

LOE ID:

8859

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 Owens Hydrologic Unit

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, "Mammoth Creek at Old Mammoth Road" was sampled.

Temporal Representation:

Ten samples (1 to 4 per year) were collected between 2001 and 2005. No samples were collected in 2002.

Environmental Conditions:

Mammoth Creek is a tributary of the Owens River with headwaters near the Sierra Nevada crest. The lower reach of Mammoth Creek is influenced by geothermal springs and is called Hot Creek.

QAPP Information:

The data meet the quality assurance requirements of the SWAMP QAPP.

QAPP Information Reference(s):


DECISION ID	71822	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

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

Regional Board Conclusion:	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 dissolved lead or total lead samples exceeds the applicable standard(s). 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 10 dissolved lead samples exceeded the California Toxics Rule standards. None of 10 total lead samples exceeded the California Maximum Contaminant Level. 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 71822, Lead	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

LOE ID:

7217

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 this station under the Region 6 SWAMP program approximately quarterly between 2001 and 2005. Dissolved lead concentrations in 9 of 10 samples were below the detection level. The remaining sample was an estimated value. The standards were not violated.

Data Reference:

2007. SWAMP Data for the Owens Hydrologic Unit

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

The California Toxics Rule freshwater aquatic life standards for lead are dependent on hardness. At the hardness levels reported for this station, the acute toxicity standard ranges from 8.92 to 42.83 ug/L and the chronic toxicity standard ranges from 0.35 to 1.67 ug/L.

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

One station, "Mammoth Creek at Old Mammoth Road" was sampled.

Temporal Representation:

Ten samples were collected approximately quarterly between 2001 and 2005.

Environmental Conditions:

QAPP Information:

The data meet the quality assurance requirements of the SWAMP QAPP.

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 71822, Lead	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

LOE ID:

7218

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 this station approximately quarterly under the Region 6 SWAMP program between 2001 and 2005. Of 10 samples, 3 had concentrations of total lead below the detection level and one was an estimated value. Conentrations in the remaining samples ranged from 0.06 to 0.17 ug/L. The MCL was not violated.

Data Reference:

2007. SWAMP Data for the Owens Hydrologic Unit

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, "Mammoth Creek at Old Mammoth Road" was sampled.

Temporal Representation:

Ten samples were collected approximately quarterly between 2001 and 2005.

Environmental Conditions:

Mammoth Creek is a tributary of the Owens River with headwaters near the Sierra Nevada crest. The lower reach of Mammoth Creek is influenced by geothermal springs and is called Hot Creek.

QAPP Information:

The data meet the quality assurance requirements of the SWAMP QAPP.

QAPP Information Reference(s):


DECISION ID	72500	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

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:	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 California of federal water quality standards 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 or criteria and the data cannot be assessed using 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 72500, Magnesium	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

LOE ID:

7197

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 this station under the Region 6 SWAMP program approximately quarterly between 2001 and 2005. Concentrations of dissolved magnesium in 10 samples ranged from 1.56 to 8.19 mg/L.

Data Reference:

2007. SWAMP Data for the Owens Hydrologic Unit

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

There are no California or federal water quality standards or criteria for magnesium. It is generally monitored as a component of another water quality parameter such as hardness, Total Dissolved Solids, or Sodium Adsorption Ratio.

Objective/Criterion Reference:

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

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

One station, "Mammoth Creek at Old Mammoth Road" was sampled.

Temporal Representation:

Ten quarterly samples were collected between August 2000 and July 2005.

Environmental Conditions:

QAPP Information:

The data meet the quality assurance requirements of the SWAMP QAPP.

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 72500, Magnesium	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

LOE ID:

7196

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 this station under the Region 6 SWAMP program approximately quarterly between 2001 and 2005. Concentrations of total magnesium in 10 samples ranged from 1.45 to 8.2 mg/L.

Data Reference:

2007. SWAMP Data for the Owens Hydrologic Unit

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, "Mammoth Creek at Old Mammoth Road" was sampled.

Temporal Representation:

Ten quarterly samples were collected between August 2001 and July 2005.

Environmental Conditions:

Mammoth Creek is a tributary of the Owens River with headwaters near the Sierra Nevada crest. The lower reach of Mammoth Creek is influenced by geothermal springs and is called Hot Creek.

QAPP Information:

The data meet the quality assurance requirements of the SWAMP QAPP.

QAPP Information Reference(s):


DECISION ID	71519	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

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

Regional Board Conclusion:	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. There are no applicable standards or criteria for molybdenum. 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. There are no applicable water quality standards or criteria 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 71519, Molybdenum	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

LOE ID:

7223

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 this station under the Region 6 SWAMP program approximately quarterly between 2001 and 2005. Concentrations of dissolved molybdenum in 10 samples ranged from 2 to 2.7 ug/L.

Data Reference:

2007. SWAMP Data for the Owens Hydrologic Unit

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

There are no California or federal water quality standards or criteria for molybdenum for the protection of aquatic life.

Objective/Criterion Reference:

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

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

One station, "Mammoth Creek at Old Mammoth Road" was sampled.

Temporal Representation:

Ten samples were collected approximately quarterly between August 2001 and July 2005.

Environmental Conditions:

QAPP Information:

The data meet the quality assurance requirements of the SWAMP QAPP.

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 71519, Molybdenum	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

LOE ID:

7224

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 this station under the Region 6 SWAMP program approximately quarterly between 2001 and 2005. Concentrations of total molybdenum in 10 samples ranged from 2 to 2.6 ug/L.

Data Reference:

2007. SWAMP Data for the Owens Hydrologic Unit

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

There are no applicable water quality standards or criteria for molybdenum for protection of the Municipal and Domestic Supply beneficial use.

Objective/Criterion Reference:

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

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

One station, "Mammoth Creek at Old Mammoth Road" was sampled.

Temporal Representation:

Ten samples were collected approximately quarterly between 2001 and 2005.

Environmental Conditions:

Mammoth Creek is a tributary of the Owens River with headwaters near the Sierra Nevada crest. The lower reach of Mammoth Creek is influenced by geothermal springs and is called Hot Creek.

QAPP Information:

The data meet the quality assurance requirements of the SWAMP QAPP.

QAPP Information Reference(s):


DECISION ID	71176	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

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

Regional Board Conclusion:	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 exceeds the applicable California Toxics Rule standards or California Maximum Contaminant Level (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 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 10 dissolved nickel samples exceeded the California Toxics Rule standards. None of 10 total nickel samples exceeded the MCL. 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 71176, Nickel	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

LOE ID:

7226

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:

The U.S. Geological Survey sampled this station under the Region 6 SWAMP program between 2001 and 2005.
Concentrations of total nickel in 2 of 10 samples were below the detection level. Concentrations in the remaining 8 samples ranged from 0.28 to 0.57 ug/L. The MCL was not violated.

Data Reference:

2007. SWAMP Data for the Owens Hydrologic Unit

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, "Mammoth Creek at Twin Lakes" was sampled.

Temporal Representation:

Ten samples (1 to 4 per year) were collected between 2001 and 2005. No samples were collected in 2002.

Environmental Conditions:

Mammoth Creek is a tributary of the Owens River with headwaters near the Sierra Nevada crest. The lower reach of Mammoth Creek is influenced by geothermal springs and is called Hot Creek.

QAPP Information:

The data meet the quality assurance requirements of the SWAMP QAPP.

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 71176, Nickel	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

LOE ID:

7225

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 this station under the Region 6 SWAMP program approximately quarterly between 2001 and 2005. Concentrations of dissolved nickel in 2 of 10 samples were below the detection level. The remaining samples had dissolved nickel concentrations ranging from 0.22 to 0.32 ug/L. The CTR standards were not exceeded.

Data Reference:

2007. SWAMP Data for the Owens Hydrologic Unit

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

The California Toxics Rule freshwater aquatic life standards for nickel are dependent on hardness. At the hardness levels reported for this station, the acute toxicity standard ranges from 125.60 to 356.41 ug/L. The chronic toxicity standard ranges from 13.96 to 39.63 ug/L

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

One station, "Mammoth Creek at Old Mammoth Road" was sampled.

Temporal Representation:

Ten samples (1 to 4 per year) were collected between 2001 and 2005. No samples were collected in 2002.

Environmental Conditions:

QAPP Information:

The data meet the quality assurance requirements of the SWAMP QAPP.

QAPP Information Reference(s):


DECISION ID	71472	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

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:	Regional Board Conclusion: This pollutant was considered for placement on the section 303(d) list in a previous listing 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. None of the annual average datapoints exceeds the site-specific 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 annual average datapoints exceeded the site-specific objective 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 71472, Phosphate	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

LOE ID:

8850

Pollutant:

Phosphate

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 this station under the Region 6 SWAMP program between 2001 and 2005. (No samples were collected in 2002.) Concentrations of PO4-P in 10 samples ranged from 0.019 to 0.066 mg/L. Calculated PO4 concentrations ranged from 0.058 to 0.202 mg/L. The objective was not exceeded.

Data Reference:

2007. SWAMP Data for the Owens Hydrologic Unit

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

The applicable site-specific objective (from Basin Plan Table 3-17) includes an annual average dissolved orthophosphate concentration of 0.27 mg/L and a 90th percentile value of 0.050 mg/L.

Objective/Criterion Reference:

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

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

One station, "Mammoth Creek at Old Mammoth Road" was sampled.

Temporal Representation:

Ten samples each (1 to 4 per year) were collected for PO4-P between 2001 and 2005. No samples were collected in 2002.

Environmental Conditions:

Mammoth Creek is a tributary of the Owens River with headwaters near the Sierra Nevada crest. The lower reach of Mammoth Creek is influenced by geothermal springs and is called Hot Creek.

QAPP Information:

The data meet the quality assurance requirements of the SWAMP QAPP.

QAPP Information Reference(s):


DECISION ID	71714	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

Pollutant:	Phosphorus
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:	Regional Board Conclusion: This pollutant was considered for placement on the section 303(d) list in a previous listing 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 for assessment whether any of the chemical 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 do not satisfy the data quality requirements of section 6.1.4 of the Policy due to an error in the SWAMP QAPP regarding holding times for total phosphorus samples.. 2. The data used satisfies the data quantity requirements of section 6.1.5 of the Policy. 3. No biological data are available for assessment of compliance with the objective for biostimulatory substances 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 71714, Phosphorus	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

LOE ID:

8852

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 this station under the Region 6 SWAMP program between 2001 and 2005. Concentrations of total phosphorus ranged from 0.035 to 0.101 mg/L. No biological data were available for assessment of compliance with the objective for biostimulatory substances.

Data Reference:

2007. SWAMP Data for the Owens Hydrologic Unit

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

There is no site-specific numeric objective for total phosphorus for Mammoth Creek. 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, "Mammoth Creek at Old Mammoth Road" was sampled.

Temporal Representation:

Ten samples (1 to 4 per year) were collected between 2001 and 2005. No samples were collected in 2002.

Environmental Conditions:

Mammoth Creek is a tributary of the Owens River with headwaters near the Sierra Nevada crest. The lower reach of Mammoth Creek is influenced by geothermal springs and is called Hot Creek.

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):


DECISION ID	72327	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

Pollutant:	Sediment
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:	Regional Board Conclusion: This pollutant was considered for placement on the section 303(d) list in a previous listing cycle. No new information was reviewed for this current assessment cycle. Therefore, the previous conclusion remains unchanged, and is as follows: The Lahontan Basin Plan's narrative water quality objective is an antidegradation based objective that provides that there shall be no increases in suspended sediment concentrations or loads. This pollutant is being considered for placement on the section 303(d) list under section 3.10 of the Listing Policy, which deals with trends in water quality. One line of evidence is available in the administrative record to assess this pollutant. It includes 10 suspended sediment concentration values and 8 suspended sediment load values calculated from instantaneous discharge measurements. Suspended sediment concentrations and loads are dependent on flows and can change rapidly over a short time during storm or snowmelt runoff events. Quarterly samples are insufficient to capture these short term events and therefore are insufficient to define natural background suspended sediment concentrations and loads, or to detect trends. Listing Policy Section 3.10 requires that natural background conditions be established. 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. Sampling frequency was insufficient to establish natural background conditions and therefore does not meet the requirements of Listing Policy Section 3.10. 3. 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 72327, Sediment	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

LOE ID:

8869

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 (USGS) sampled this station under the Region 6 SWAMP program approximately quarterly between 2001 and 2005. (No samples were collected in 2002.) Suspended sediment concentrations in 10 samples ranged from 2 to 16 mg/L. The USGS calculated sediment loads based on 8 instantaneous discharge flow measurements collected from 2003 to 2005. Flows ranged from 7.3 to 60 cubic feet per second. The associated loads ranged from 0.07 to 0.57 tons per day. The data were not sufficient to document baseline and trend conditions to assess compliance with the objective.

Data Reference:

2007. SWAMP Data for the Owens Hydrologic Unit

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

The Lahontan Basin Plan's 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, "Mammoth Creek at Old Mammoth Road" was sampled.

Temporal Representation:

Ten samples (1 to 4 per year) were collected quarterly in 2001 and from 2003 to 2005.

Environmental Conditions:

Mammoth Creek is a tributary of the Owens River with headwaters near the Sierra Nevada crest. The lower reach of Mammoth Creek is influenced by geothermal springs and is called Hot Creek. In addition to the Cold Freshwater Habitat beneficial use, Mammoth Creek is designated for the Spawning, Reproduction and Development¿ and Migration of Aquatic Organisms beneficial uses.

QAPP Information:

The data meet the quality assurance requirements of the SWAMP QAPP.

QAPP Information Reference(s):


DECISION ID	71833	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

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

Regional Board Conclusion:	Regional Board Conclusion: This pollutant was considered for placement on the section 303(d) list in a previous listing 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 exceeds the applicable water quality standard. 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 10 dissolved selenium samples exceeded the California Toxics Rule standards. None of 10 total selenium samples exceeded the California 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 71833, Selenium	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

LOE ID:

7235

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 this station approximately quarterly under the Region 6 SWAMP program between 2001 and 2005. Concentrations of dissolved selenium in 10 samples were all below the detection levels. The California Toxics Rule standards were not violated.

Data Reference:

2007. SWAMP Data for the Owens Hydrologic Unit

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

The California Toxics Rule selenium standards for the 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, "Mammoth Creek at Old Mammoth Road" was sampled.

Temporal Representation:

Ten samples were collected approximately quarterly between 2001 and 2005.

Environmental Conditions:

QAPP Information:

The data meet the quality assurance requirements of the SWAMP QAPP.

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 71833, Selenium	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

LOE ID:

7236

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 this station approximately quarterly under the Region 6 SWAMP program between 2001 and 2005. Ten out of ten samples were below detection levels. The MCL was not violated.

Data Reference:

2007. SWAMP Data for the Owens Hydrologic Unit

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, "Mammoth Creek at Old Mammoth Road" was sampled.

Temporal Representation:

Ten samples were collected approximately quarterly between 2001 and 2005.

Environmental Conditions:

Mammoth Creek is a tributary of the Owens River with headwaters near the Sierra Nevada crest. The lower reach of Mammoth Creek is influenced by geothermal springs and is called Hot Creek.

QAPP Information:

The data meet the quality assurance requirements of the SWAMP QAPP.

QAPP Information Reference(s):


DECISION ID	71834	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

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

Regional Board Conclusion:	Regional Board Conclusion: This pollutant was considered for placement on the section 303(d) list in a previous listing 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 exceeds the applicable water quality standard(s). 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 10 dissolved silver samples exceeded the California Toxics Rule standards. None of 10 total silver samples exceeded the California Maximum Contaminant Level. 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 71834, Silver	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

LOE ID:

7227

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 this station under the Region 6 SWAMP program approximately quarterly between 2001 and 2005. Concentrations of dissolved silver in 10 samples were below the detection level. Per Listing Policy Section 6.1.5.5, the CTR standards were not violated.

Data Reference:

2007. SWAMP Data for the Owens Hydrologic Unit

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

The California Toxics Rule freshwater aquatic life standards for silver are dependent on hardness. At the hardness levels reported for this station, the acute toxicity standard (as an instantaneous maximum) ranges from 0.24 to 1.98 mg/L.:

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

One station, "Mammoth Creek at Old Mammoth Road" was sampled.

Temporal Representation:

Ten samples were collected approximately quarterly between 2001 and 2005.

Environmental Conditions:

QAPP Information:

The data meet the quality assurance requirements of the SWAMP QAPP.

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 71834, Silver	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

LOE ID:

7228

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 this station under the Region 6 SWAMP program between 2001 and 2005.
Concentrations of total silver in 10 samples were below the detection level. Per Listing Policy section 6.1.5.5, the MCL was not violated.

Data Reference:

2007. SWAMP Data for the Owens Hydrologic Unit

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 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, "Mammoth Creek at Old Mammoth Road" was sampled.

Temporal Representation:

Ten samples were collected approximately quarterly between 2001 and 2005.

Environmental Conditions:

Mammoth Creek is a tributary of the Owens River with headwaters near the Sierra Nevada crest. The lower reach of Mammoth Creek is influenced by geothermal springs and is called Hot Creek.

QAPP Information:

The data meet the quality assurance requirements of the SWAMP QAPP.

QAPP Information Reference(s):


DECISION ID	162329	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

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	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 162329, Sulfates	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

LOE ID:

340712

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, 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 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: 603MAM008 (Mammoth Cr, at Twin Lakes).

Temporal Representation:

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

Environmental Conditions:

QAPP Information:

Generic SWAMP QAPrP

QAPP Information Reference(s):

Generic SWAMP QAPrP

Line of Evidence (LOE) for Decision ID 162329, Sulfates	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

LOE ID:

341937

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: USGS-10265125 (MAMMOTH C A TWIN LAKES NR MAMMOTH LAKES CA).

Temporal Representation:

The samples were collected between the dates of 2018-07-25 and 2021-08-02

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


DECISION ID	71780	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

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:	Regional Board Conclusion: This pollutant was considered for placement on the section 303(d) list in a previous listing cycle. No new information was reviewed for this current assessment cycle. Therefore, the previous conclusion remains unchanged, and is as follows: 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. One line of evidence is available to support this decision. 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.

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 71780, Temperature, water	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

LOE ID:

7175

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:

Fixed station physical/chemical (conventional plus toxic pollutants)

Data Used to Assess Water Quality:

The U.S. Geological Survey sampled this station approximately quarterly under the Region 6 SWAMP program between 2001 and 2005. (No samples were collected in 2002.) Water temperatures in 9 measurements ranged from 0 to18 degrees Celsius.

Data Reference:

2007. SWAMP Data for the Owens Hydrologic Unit

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

The applicable language from the Lahontan Basin Plan's temperature objective states: "The natural receiving water temperature of all waters shall not be altered unless it can be demonstrated to the satisfaction of the Regional Board that such an alteration in temperature does not adversely affect the water for beneficial uses.

For waters designated WARM, water temperature shall not be altered by more than five degrees Fahrenheit (5o F) above or below the natural temperature. For waters designated COLD, the temperature shall not be altered."

Objective/Criterion Reference:

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

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

One station, "Mammoth Creek at Old Mammoth Road" was sampled.

Temporal Representation:

Nine temperature measurements were taken approximately quarterly between August 2001 and July 2005. No measurements were taken in 2002.

Environmental Conditions:

QAPP Information:

The data meet the quality assurance requirements of the SWAMP QAPP.

QAPP Information Reference(s):


DECISION ID	70988	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

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

Regional Board Conclusion:	Regional Board Conclusion: This pollutant was considered for placement on the section 303(d) list in a previous listing 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 available in the administrative record to assess this pollutant. None of the samples for total thallium or dissolved thallium exceeds the applicable criteria or standard. 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 10 dissolved thallium samples exceeded the freshwater aquatic life criteria. None of 10 total thallium samples exceeded the California 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 70988, Thallium	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

LOE ID:

7221

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 this station under the Region 6 SWAMP program between 2001 and 2005.
Concentrations of total recoverable thallium in 10 samples were below the detection level. Per Listing Policy section 6.1.5.5, the MCL was not violated.

Data Reference:

2007. SWAMP Data for the Owens Hydrologic Unit

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, "Mammoth Creek at Old Mammoth Road" was sampled.

Temporal Representation:

Ten samples were collected approximately quarterly between 2001 and 2005.

Environmental Conditions:

Mammoth Creek is a tributary of the Owens River with headwaters near the Sierra Nevada crest. The lower reach of Mammoth Creek is influenced by geothermal springs and is called Hot Creek. In addition to the Cold Freshwater Habitat beneficial use, Mammoth Creek is designated for the Spawning, Reproduction and Development¿and Migration of Aquatic Organisms beneficial uses.

QAPP Information:

The data meet the quality assurance requirements of the SWAMP QAPP.

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 70988, Thallium	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

LOE ID:

7222

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:

Data Reference:

2007. SWAMP Data for the Owens Hydrologic Unit

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 thallium is 2 ug/L.

Objective/Criterion Reference:

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

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

One station, "Mammoth Creek at Old Mammoth Road" was sampled.

Temporal Representation:

Ten samples were collected approximately quarterly between 2001 and 2005.

Environmental Conditions:

Mammoth Creek is a tributary of the Owens River with headwaters near the Sierra Nevada crest. The lower reach of Mammoth Creek is influenced by geothermal springs and is called Hot Creek.

QAPP Information:

The data meet the quality assurance requirements of the SWAMP QAPP.

QAPP Information Reference(s):


DECISION ID	71125	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

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	Original
Impairment from Pollutant or Pollution:	Pollutant

Regional Board Conclusion:	Regional Board Conclusion: This pollutant was considered for placement on the section 303(d) list in a previous listing 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. There are no biological data available for assessment whether of the chemical samples exceeds the water quality objective for biostimulatory substances. 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. There are no biological data available for assessment of compliance with the objective for biostimulatory substances under 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 71125, Total Kjeldahl Nitrogen (TKN)	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

LOE ID:

8846

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 sampled this station under the Region 6 SWAMP program between 2001 and 2005. Concentrations of TKN in 10 samples ranged from 0.001 to 0.058 mg/L. No biological data are available for assessment of compliance with the water quality objective for biostimulatory substances.

Data Reference:

2007. SWAMP Data for the Owens Hydrologic Unit

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

There is no site-specific numeric objective for Total Kjeldahl Nitrogen (TKN) for Mammoth Creek. 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, "Mammoth Creek at Old Mammoth Road" was sampled.

Temporal Representation:

Ten samples (1 to 4 per year) were collected between 2001 and 2005. No samples were collected in 2002.

Environmental Conditions:

Mammoth Creek is a tributary of the Owens River with headwaters near the Sierra Nevada crest. The lower reach of Mammoth Creek is influenced by geothermal springs and is called Hot Creek.

QAPP Information:

The data meet the quality assurance requirements of the SWAMP QAPP.

QAPP Information Reference(s):


DECISION ID	78860	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

Pollutant:	Toxicity
Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)(2016)
Revision Status	Original
Impairment from Pollutant or Pollution:	Pollutant

Regional Board Conclusion:	This pollutant is being considered for placement on the section 303(d) list under section 3.1 of the Listing Policy. Under section 3.1 a single line of evidence is necessary to assess listing status. One line of evidence is available in the administrative record to assess this pollutant. The single sample 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 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. 3. The single sample exceeded the guideline 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 16 samples is needed for application of 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:	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 78860, Toxicity	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

LOE ID:

32066

Pollutant:

Toxicity

LOE Subgroup:

Toxicity

Matrix:

Sediment

Fraction:

None

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

TOXICITY TESTING

Data Used to Assess Water Quality:

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

Data Reference:

Statewide Project Urban Pyrethroid Status Monitoring

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

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

Evaluation Guideline:

Toxicity is defined as a statistically significant effect in the sample exposure compared to the control using EPA-recommended hypothesis testing. For SWAMP data exceedances are counted with the significant effect code SL. SL is defined as the result being significant compared to the negative control based on a statistical test, less than stated the alpha level, AND less than the evaluation threshold.

Guideline Reference:

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

Spatial Representation:

The sample was collected at station 603SUP028.

Temporal Representation:

The sample was collected in October 2006.

Environmental Conditions:

QAPP Information:

All data was collected following the Standard Operating Procedures and Data Quality Objectives outlined in the SWAMP QAMP, (Puckett, 2002). QA data are included in submission.

QAPP Information Reference(s):

Surface Water Ambient Monitoring Program Quality Assurance Program Plan


DECISION ID	72387	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

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

Regional Board Conclusion:	Regional Board Conclusion: This pollutant was considered for placement on the section 303(d) list in a previous listing 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. There are no applicable standards or criteria for dissolved vanadium. None of the total vanadium samples exceeds the applicable criterion. 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 10 samples for total vanadium exceeded the California Notification Level criterion and this does not exceed the allowable frequency listed in Table 3.1 of the Listing Policy. 4. Pursuant to section 3.11 of the Listing Policy, no additional data and information are available indicating that standards are not met.

Regional Board Decision Recommendation:	This 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 72387, Vanadium	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

LOE ID:

7230

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 this station under the Region 6 SWAMP program approximately quarterly between 2001 and 2005. Concentrations of total vanadium in 5 of 10 samples were below the detection level. The presence of vanadium in the remaining 5 samples was verified but not quantified. The criterion was not violated.

Data Reference:

2007. SWAMP Data for the Owens Hydrologic Unit

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, "Mammoth Creek at Old Mammoth Road" was sampled.

Temporal Representation:

Ten samples were collected approximately quarterly between 2001 and 2005.

Environmental Conditions:

Mammoth Creek is a tributary of the Owens River with headwaters near the Sierra Nevada crest. The lower reach of Mammoth Creek is influenced by geothermal springs and is called Hot Creek.

QAPP Information:

The data meet the quality assurance requirements of the SWAMP QAPP.

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 72387, Vanadium	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

LOE ID:

7229

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 this station under the Region 6 SWAMP program approximately quarterly between 2001 and 2005. Concentrations of dissolved vanadium in 2 of 10 samples were below the detection level. Vanadium concentrations in the remaining 8 samples ranged from 0.3 to 0.9 ug/L.

Data Reference:

2007. SWAMP Data for the Owens Hydrologic Unit

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

There are no California or federal standards or criteria for dissolved vanadium 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, "Mammoth Creek at Old Mammoth Road" was sampled.

Temporal Representation:

Ten samples were collected approximately quarterly between 2001 and 2005.

Environmental Conditions:

QAPP Information:

The data meet the quality assurance requirements of the SWAMP QAPP.

QAPP Information Reference(s):


DECISION ID	72554	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

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

Regional Board Conclusion:	Regional Board Conclusion: This pollutant was considered for placement on the section 303(d) list in a previous listing 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 exceeds the applicable water quality standard(s). 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. None of 10 dissolved zinc samples exceeded the California Toxics Rule standards. None of 10 total zinc samples exceeded the California Maximum Contaminant Level. 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 72554, Zinc	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

LOE ID:

7231

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 this station under the Region 6 SWAMP program approximately quarterly between 2001 and 2005. One of 10 samples for dissolved zinc was below the detection level, and 2 were estimated values. Concentrations of dissolved zinc in the remaining samples ranged from 0.6 to 2.8 ug/L. The CTR standards were not violated.
Concentrations of dissolved zinc in 12 samples ranged from 0.8 to 3 ug/L Three samples were estimated values and two were below detection levels The standards were not violated..

Data Reference:

2007. SWAMP Data for the Owens Hydrologic Unit

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 toxicity standard ranges from 31.37 to 89.16 ug/L, and the chronic toxicity standard ranges from 31.63 to 89.89 ug/L.

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

One station, "Mammoth Creek at Old Mammoth Road" was sampled.

Temporal Representation:

Ten samples were collected approximately quarterly between 2001 and 2005.

Environmental Conditions:

QAPP Information:

The data meet the quality assurance requirements of the SWAMP QAPP.

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 72554, Zinc	Region 6
Mammoth Creek (Twin Lakes outlet to Old Mammoth Road)

LOE ID:

7232

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 this station approximately quarterly under the Region 6 SWAMP program between 2001 and 2005. Of ten samples for total recoverable zinc, one was below the detection level and four were estimated values. Concentrations of total recoverable zinc in the remaining 4 samples ranged from 3 to 4 ug/L. The MCL was not violated.

Data Reference:

2007. SWAMP Data for the Owens Hydrologic Unit

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 zinc is 5 mg/L, equivalent to 5000 ug/L.

Objective/Criterion Reference:

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

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

One station, "Mammoth Creek at Old Mammoth Road" was sampled.

Temporal Representation:

Ten samples were collected approximately quarterly between 2001 and 2005.

Environmental Conditions:

Mammoth Creek is a tributary of the Owens River with headwaters near the Sierra Nevada crest. The lower reach of Mammoth Creek is influenced by geothermal springs and is called Hot Creek.

QAPP Information:

The data meet the quality assurance requirements of the SWAMP QAPP.

QAPP Information Reference(s):