Final California 2010 Integrated Report (303(d) List/305(b) Report)

Supporting Information

Regional Board 6 - Lahontan Region

Water Body Name:	Twin Lakes (Owens HU)
Water Body ID:	CAL6031005119990128112146
Water Body Type:	Lake & Reservoir


DECISION ID	6552	Region 6
Twin Lakes (Owens HU)

Pollutant:	Nitrogen
Final Listing Decision:	Delist from 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	List on 303(d) list (TMDL required list)(2006)
Revision Status	Revised
Reason for Delisting:	Flaws in original listing
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 of the Listing Policy. Under this section a single line of evidence is necessary to assess listing status. Three lines of evidence are available in the administrative record to assess this pollutant. The original listing was based on qualitative information rather than numeric data and no monitoring data are available to assess whether the lakes exceed the site-specific water quality objectives. Monitoring data for a creek station at the outlet of the lowest lake show attainment of nitrogen objectives at that station. Based on the readily available data and information, the weight of evidence indicates that there is sufficient justification for removing this water segment-pollutant combination from the section 303(d) list. This conclusion is based on the staff findings that: 1.The original listing was based on quantitative information rather than data and would meet current requirements for being listed under the Listing Policy.. 2. No current monitoring data for the Twin Lakes themselves are available. 3. SWAMP samples from a creek station at the outlet of the lowest lake show no evidence of impairment for nitrogen. 4. Pursuant to section 4.11 of the Listing Policy, no additional data and information are available indicating that standards are not met.

Regional Board Decision Recommendation:	After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should be removed from the section 303(d) list because the original listing was flawed and there is no evidence that applicable water quality standards for the pollutant are being exceeded.

State Board Review of Regional Board Conclusion and Recommendation:

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

USEPA Action (if applicable):

Line of Evidence (LOE) for Decision ID 6552, Nitrogen	Region 6
Twin Lakes (Owens HU)

LOE ID:

26926

Pollutant:

Nitrogen

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

None

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

QUALITATIVE (EVALUATED) ASSESSMENT - UNSPECIFIED

Data Used to Assess Water Quality:

The Twin Lakes were listed in the early 1990s based on inforation that funds had been budgeted for the control of macrophytes. No quantitative water quality data were available at the time and Water Board staff are unaware of any quantitative data on nutrients, macrophytes, or algae collected in the lakes since the original listing. The USGS sampled Mammoth Creek at the outlet of the lowest Twin Lake under the Region 6 SWAMP program between 2001 and 2005, and the water quality objectives for nitrogen were not violated.

Data Reference:

2007. SWAMP Data for the Owens Hydrologic Unit

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

The Lahontan Basin Plan's site-specific water quality objectives for the Twin Lakes are those for the "Mammoth Creek at Twin Lakes Outlet" station in Basin Plan Table 3-17. These objectives apply upstream through the "Tributary Rule." The objective for nitrate "as nitrate" includes an annual average of 0.4 mg/L and a 90th percentile value of 0.08 mg/L. The objective for total nitrogen includes an annual average of 0.5 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)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

No current monitoring data are available..

Temporal Representation:

No current monitoring data are available.

Environmental Conditions:

There are three "Twin Lakes" located on Mammoth Creek in the Owens River watershed.

QAPP Information:

No current monitoring data are available.

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 6552, Nitrogen	Region 6
Twin Lakes (Owens HU)

LOE ID:

29793

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. Sixteen quarterly samples were collected for nitrite and sixteen for nitrate plus nitrite. Nitrite values ranged from below detection level (8 of 16 samples) to 0.002 mg/L. Nitrate plus nitrite values ranged from below detection level (8 of 16 samples) to 0.023 mg/L. Nitrate was calculated by subtraction; the highest concentration was 0.021 mg/L as N.
Expressed "as nitrate" the highest concentration was 0.0945 mg/L. The annual average objective was not exceeded.

Data Reference:

2007. SWAMP Data for the Owens Hydrologic Unit

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

The objective (from Lahontan Basin Plan Table 3-17, for Station 4, Mammoth Creek at Twin Lakes Bridge) includes an annual average nitrate N (as nitrate) 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 Twin Lakes" was sampled.

Temporal Representation:

Sixteen samples each for nitrite and nitrate plus nitrite were collected quarterly between August 2001 and July 2005.

Environmental Conditions:

There are three "Twin Lakes" on Mammoth Creek. 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 6552, Nitrogen	Region 6
Twin Lakes (Owens HU)

LOE ID:

29792

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. Sixteen quarterly samples were collected for Total Kjeldahl Nitrogen and nitrate plus nitrite. Concentrations of Total Kjeldahl nitrogen ranged from 0.09 to 0.4 mg/L. Nitrate plus nitrite concentrations ranged from below detection level (8 of 16 samples) to 0.023 mg/L. The highest calculated concentration of Total Nitrogen was 0.43 mg/L as N. The annual average objective was not exceeded.

Data Reference:

2007. SWAMP Data for the Owens Hydrologic Unit

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

The objective (from Basin Plan Table 3-17, for Station 4, Mammoth Creek at Twin Lakes Bridge) includes an annual average total nitrogen concentration of 0.5 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)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

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

Temporal Representation:

Sixteen samples each for total Kjeldahl nitrogen and nitrate plus nitrite were collected 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. 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	6553	Region 6
Twin Lakes (Owens HU)

Pollutant:	Phosphorus
Final Listing Decision:	Delist from 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	List on 303(d) list (TMDL required list)(2006)
Revision Status	Revised
Reason for Delisting:	Flaws in original listing
Impairment from Pollutant or Pollution:	Pollution

Regional Board Conclusion:	This pollutant is being considered for removal from the section 303(d) list under section 4 of the Listing Policy. Under this section 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. The original listing was based on qualitative information rather than numeric data and no monitoring data are available to assess whether the lakes exceed the site-specific water quality objective. Monitoring data for a creek station at the outlet of the lowest lake show attainment of the objective for total orthophosphate at that station. Based on the readily available data and information, the weight of evidence indicates that there is sufficient justification for removing this water segment-pollutant combination from the section 303(d) list. This conclusion is based on the staff findings that: 1.The original listing was based on quantitative information rather than data and would meet current requirements for being listed under the Listing Policy.. 2. No current monitoring data for the Twin Lakes themselves are available. 3. SWAMP samples from a creek station at the outlet of the lowest lake show no evidence of impairment for phosphorus. 4. Pursuant to section 4.11 of the Listing Policy, no additional data and information are available indicating that standards are not met.

Regional Board Decision Recommendation:	After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should be removed from the section 303(d) list because the original listing was flawed and there is no evidence that applicable water quality standards for the pollutant are being exceeded.

State Board Review of Regional Board Conclusion and Recommendation:

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

USEPA Action (if applicable):

Line of Evidence (LOE) for Decision ID 6553, Phosphorus	Region 6
Twin Lakes (Owens HU)

LOE ID:

29794

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 2002 and 2005. Concentrations of PO4-P in 14 quarterly samples ranged from below detection level (4 samples) to 0.01 mg/L. Two samples were estimated values. The annual average objective was not exceeded.

One additional sample collected on 11/28/2001 was analyzed for hydrolyzable phosphorus. The concentration was below the detection level.

Data Reference:

2007. SWAMP Data for the Owens Hydrologic Unit

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

The site-specific objective (from Lahontan Basin Plan Table 3-17, for Station 4, Mammoth Creek at Twin Lakes Bridge): includes an annual average Total Orthophosphate 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 Twin Lakes" was sampled.

Temporal Representation:

Fourteen samples were collected quarterly between March 2002 and and July 2005. One sample was collected for hydrolyzable phosphorus on 11/28/2001.

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 6553, Phosphorus	Region 6
Twin Lakes (Owens HU)

LOE ID:

26927

Pollutant:

Phosphorus

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

None

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

QUALITATIVE (EVALUATED) ASSESSMENT - UNSPECIFIED

Data Used to Assess Water Quality:

The Twin Lakes were listed in the early 1990s based on information that funds had been budgeted for the control of macrophytes. No quantitative water quality data were available at the time and Water Board staff are unaware of any quantitative data on nutrients, macrophytes, or algae collected in the lakes since the original listing. The USGS sampled Mammoth Creek at the outlet of the lowest Twin Lake under the Region 6 SWAMP program between 2001 and 2005, and the water quality objective for total orthophosphate 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 site-specific water quality objectives for the Twin Lakes are those for the "Mammoth Creek at Twin Lakes Outlet" station in Basin Plan Table 3-17. These objectives apply upstream through the "Tributary Rule." The objective for total orthophosphate includes an annual average 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:

No current monitoring data are available..

Temporal Representation:

No current monitoring data are available.

Environmental Conditions:

There are three "Twin Lakes" located on Mammoth Creek in the Owens River watershed.

QAPP Information:

No current monitoring data are available.

QAPP Information Reference(s):