Draft 2008 California 303(d)/305(b) Integrated Report

Supporting Information

Regional Board 6 - Lahontan Region

Water Body Name:	Mammoth Creek (Headwaters to Twin Lakes outlet)
Water Body ID:	CAR6031005120080816103626
Water Body Type:	River & Stream

DECISION ID	16240
Pollutant:	Mercury
Final Listing Decision:	Delist from 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	New Decision
Revision Status	Revised
Reason for Delisting:	State determines water quality standard is being met
Impairment from Pollutant or Pollution:	Pollutant
Weight of Evidence:	Mammoth Creek as a whole was listed for mercury in 2002 based on fish tissue sample collected downstream of the Twin Lakes outlet. Mammoth Creek was divided into segments for purposes of the 2008 Integrated Report assessment. There is no fish passage between the headwaters and downstream segments and no tissue samples are available for the headwaters segment. Water samples do not violate standards. The number of available water samples does not meet the minimum sample number requirement of Table 4.1 of the policy. However, since listing was done on the basis of the tissue data, delisting is recommended. This pollutant is being considered for removal from the 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. Three lines of evidence are available in the administrative record to assess this pollutant. None of the water samples exceeded the water quality objective. 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 data used satisfy the data quality requirements of section 6.1.4 of the Policy. 2. The water data used do not satisfy the data quantity requirements of section 6.1.5 of the Policy. Quarterly samples do not capture the full range of seasonal and annual variabiliyt expected in streamflows and constituent concentrations in waters of the Lahontan Region. 3. There are no tissue data for this segment. None of 12 samples exceeded the applicable standards and this does not exceed the allowable frequency listed in Table 4.1 of the Listing Policy. The minimum sample number requirements of Table 4.1 are not met. 4. Pursuant to section 4.11 of the Listing Policy, no additional data and information are available indicating that standards are not met.
RWQCB Board Decision / Staff Recommendation:	After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should be removed from the section 303(d) list because applicable water quality standards for the pollutant are not being exceeded.
SWRCB Board Decision / Staff Recommendation:
USEPA Decision:

Lines of Evidence (LOEs) for Decision ID 16240

LOE ID:	7062
Pollutant:	Mercury
LOE Subgroup:	Pollutant-Water
Matrix:	Water
Fraction:	Total
Beneficial Use:	Municipal & Domestic Supply
Number of Samples:	12
Number of Exceedances:	0
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 mercury in 8 of 12 samples were below the detection level. Two samples were estimated values. Mercury concentrations in both of the remaining samples were 0.01 ug/L. The CTR standard was not exceeded.
Data Reference:	2007. SWAMP Data for the Owens Hydrologic Unit
Water Quality Objective/Criterion:	The California Toxics Rule human health standard for consumption of water and organisms is 0.05 ug/L as a 30 day average.
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:	One station, "Mammoth Creek at Twin Lakes" was sampled.
Temporal Representation:	Twelve 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):
LOE ID:	7064
Pollutant:	Mercury
LOE Subgroup:	Pollutant-Water
Matrix:	Water
Fraction:	Dissolved
Beneficial Use:	Cold Freshwater Habitat
Number of Samples:	12
Number of Exceedances:	0
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 mercury in 10 of 12 samples were below the detection level. One sample was an estimated value, and the concentration in the remaining sample was 0.01 ug/L.
Data Reference:	2007. SWAMP Data for the Owens Hydrologic Unit
Water Quality Objective/Criterion:	There are no applicable California or federal aquatic life criteria for dissolved mercury. The U.S. Environmental Protection Agency's national freshwater aquatic life criteria are expressed as total mercury (including inorganic and organic mercury). Total mercury data for this station are assessed in separate Lines of Evidence.
Objective/Criterion Reference:	2007. 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:	Twelve 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):
LOE ID:	7063
Pollutant:	Mercury
LOE Subgroup:	Pollutant-Water
Matrix:	Water
Fraction:	Total
Beneficial Use:	Cold Freshwater Habitat
Number of Samples:	12
Number of Exceedances:	0
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 mercury in 8 of 12 samples were below the detection level. Two samples were estimated values. Mercury concentrations in both of the remaining samples were 0.01 ug/L. The USEPA criteria were not exceeded.
Data Reference:	2007. SWAMP Data for the Owens Hydrologic Unit
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:	National recommended water quality criteria: 2002. EPA-822-R-02-047 Washington, D.C. USEPA
Evaluation Guideline:
Guideline Reference:
Spatial Representation:	One station, "Mammoth Creek at Twin Lakes" was sampled.
Temporal Representation:	Twelve 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	16416
Pollutant:	Metals
Final Listing Decision:	Delist from 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	New Decision
Revision Status	Revised
Reason for Delisting:	Other
Impairment from Pollutant or Pollution:	Pollutant
Weight of Evidence:	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 mercury listing for the creek as a whole is not being carried forward to the headwaters segment because the fish tissue was collected downstream, below a fish passage barrier. For the same reason, a "Metals" listing based on tissue data is not appropriate for this segment.
RWQCB Board Decision / Staff Recommendation:	After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination for this segment should not be placed on the section 303(d) list for "metals" because the tissue data used in the original listing were collected downstream below a fish passage barrier.
SWRCB Board Decision / Staff Recommendation:
USEPA Decision:

Lines of Evidence (LOEs) for Decision ID 16416

LOE ID:	6962
Pollutant:	Metals
LOE Subgroup:	Pollutant-Water
Matrix:	Water
Fraction:	Not Recorded
Beneficial Use:	Cold Freshwater Habitat
Number of Samples:	0
Number of Exceedances:	0
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)
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	8212
Pollutant:	Aluminum
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
Weight of Evidence:	This pollutant is being considered for placement on the section 303(d) list under section 3.1 of the Listing Policy. Under section 3.1 a single line of evidence is necessary to assess listing status. Two lines of evidence are available in the administrative record to assess this pollutant. None of the samples exceed the applicable water quality objective and aquatic life criteria. 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 eight total recoverable aluminum samples exceeded the Maximum Contaminant Level. None of eight dissolved aluminum samples exceeded the national freshwater aquatic life criteria for aluminum 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.
RWQCB Board Decision / Staff 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.
SWRCB Board Decision / Staff Recommendation:
USEPA Decision:

Lines of Evidence (LOEs) for Decision ID 8212

LOE ID:	6993
Pollutant:	Aluminum
LOE Subgroup:	Pollutant-Water
Matrix:	Water
Fraction:	Dissolved
Beneficial Use:	Cold Freshwater Habitat
Number of Samples:	8
Number of Exceedances:	0
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. Of eight dissolved aluminum samples collected between 2001 and 2004, four had concentrations below the detection level and two were estimated values. The remaining samples both had dissolved aluminum concentrations of 4 ug/L. An additional four samples collected between 2004 and 2005 were analyzed by the same method as dissolved aluminum, but reported as "Aluminum, water, unfiltered." One of these samples was below the detection level, another was an estimate, and a third was detected but not quantified. The fourth sample had a concentration of 6 ug/L. The USEPA criteria were not violated.
Data Reference:	2007. SWAMP Data for the Owens Hydrologic Unit
Water Quality Objective/Criterion:	The U.S. Environmental Protection Agency's national water quality criteria for aluminum for the protection of freshwater aquatic life are a 4- day average of 87 ug/L and a 1-hour average of 750 ug/L.
Objective/Criterion Reference:	National recommended water quality criteria: 2002. EPA-822-R-02-047 Washington, D.C. USEPA
Evaluation Guideline:
Guideline Reference:
Spatial Representation:	One station, "Mammoth Creek at Twin Lakes" was sampled.
Temporal Representation:	Eight samples reported as dissolved aluminum were collected between 2001 and 2004. Four samples reported as "filtered" were collected in 2004 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):
LOE ID:	6996
Pollutant:	Aluminum
LOE Subgroup:	Pollutant-Water
Matrix:	Water
Fraction:	Total
Beneficial Use:	Municipal & Domestic Supply
Number of Samples:	8
Number of Exceedances:	0
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 aluminum in 8 samples collected between 2001 and 2004 ranged from 2 to 35 ug/L. An additional four samples were reported as "water, unfiltered, recoverable." One of these samples was an estimate, and aluminum concentrations in the others ranged from 2 to 12 ug/L. The MCLs were not violated.
Data Reference:	2007. SWAMP Data for the Owens Hydrologic Unit
Water Quality Objective/Criterion:	California Maximum Contaminant Levels (MCLs) apply to ambient waters under the Lahontan Basin Plan's "Chemical Constituents" objective. The California primary MCL for aluminum is 1000 ug/L and the secondary MCL is 200 ug/L.
Objective/Criterion Reference:	2007. 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:	Eight samples reported as total recoverable aluminum were collected between 2001 and 2004. Four samples reported as unfiltered recoverable aluminum were collected between 2004 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	8224
Pollutant:	Antimony
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
Weight of Evidence:	This pollutant is being considered for placement on the section 303(d) list under section 3.1 of the Listing Policy. Under section 3.1 a single line of evidence is necessary to assess listing status. Two lines of evidence are available in the administrative record to assess this pollutant. None of the samples exceed applicable aquatic life criteria or the 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 twelve dissolved antimony samples exceeded the U.S. Environmental Protection Agency's LOEL criteria. None of twelve total antimony samples exceeded the Maximum Contaminant Level and this does not exceed the allowable frequency listed in Table 3.1 of the Listing Policy. 4. Pursuant to section 3.11 of the Listing Policy, no additional data and information are available indicating that standards are not met.
RWQCB Board Decision / Staff 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.
SWRCB Board Decision / Staff Recommendation:
USEPA Decision:

Lines of Evidence (LOEs) for Decision ID 8224

LOE ID:	7057
Pollutant:	Antimony
LOE Subgroup:	Pollutant-Water
Matrix:	Water
Fraction:	Total
Beneficial Use:	Municipal & Domestic Supply
Number of Samples:	8
Number of Exceedances:	0
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 antimony in 8 samples collected between 2001 and 2004 were all below the detection level. Concentrations of unfiltered antimony in 3 of 4 samples collected between 2004 and 2005 were below the detection level. The fourth sample was an estimated value. The MCL was not exceeded.
Data Reference:	2007. SWAMP Data for the Owens Hydrologic Unit
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:	2007. 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:	Eight samples reported as total recoverable antimony were collected between 2001 and 2004. Four samples reported as "unfiltered" were collected between October 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):
LOE ID:	7056
Pollutant:	Antimony
LOE Subgroup:	Pollutant-Water
Matrix:	Water
Fraction:	Dissolved
Beneficial Use:	Cold Freshwater Habitat
Number of Samples:	8
Number of Exceedances:	0
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. Four of 8 dissolved antimony samples collected between 2001 and 2004 were below the detection level. Another sample was an estimated value, and the remaining samples ranged from 0.09 to 0.13 ug/L. Concentrations of filtered antimony in samples collected between 2004 and 2005 were below the detection level in 3 of 4 samples and an estimated value in one sample. The criteria were not violated.
Data Reference:	2007. SWAMP Data for the Owens Hydrologic Unit
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 Twin Lakes" was sampled.
Temporal Representation:	Eight samples reported as dissoved antimony were collected between 2001 and 2004. Four samples reported as filtered antimony were collected between October 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. 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	8163
Pollutant:	Arsenic
Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	New Decision
Revision Status	Revised
Impairment from Pollutant or Pollution:	Pollutant
Weight of Evidence:	This pollutant is being considered for placement on the section 303(d) list under section 3.1 of the Listing Policy. Under section 3.1 a single line of evidence is necessary to assess listing status. Two lines of evidence are available in the administrative record to assess this pollutant. None of the samples exceed the applicable water quality objective and California Toxics Rule 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 12 dissolved arsenic samples exceeded the California Toxics Rule standards. None of 12 total arsenic 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.
RWQCB Board Decision / Staff 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.
SWRCB Board Decision / Staff Recommendation:
USEPA Decision:

Lines of Evidence (LOEs) for Decision ID 8163

LOE ID:	6957
Pollutant:	Arsenic
LOE Subgroup:	Pollutant-Water
Matrix:	Water
Fraction:	Total
Beneficial Use:	Municipal & Domestic Supply
Number of Samples:	12
Number of Exceedances:	1
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 12 samples collected approximately quarterly, concentrations of total arsenic ranged from 1 to 13 ug/L. One sample exceeded the MCL
Data Reference:	2007. SWAMP Data for the Owens Hydrologic Unit
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 arsenic is 10 ug/L (effective November 28, 2008).
Objective/Criterion Reference:	2007. 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:	Twelve 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. 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):
LOE ID:	6956
Pollutant:	Arsenic
LOE Subgroup:	Pollutant-Water
Matrix:	Water
Fraction:	Dissolved
Beneficial Use:	Cold Freshwater Habitat
Number of Samples:	12
Number of Exceedances:	0
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 12 samples for dissolved arsenic, eight were below the detection level, estimated values, or detected but not quantified values. The remaining four samples ranged from 2 to 3 ug/L. The California Toxics Rule standards were not exceeded.
Data Reference:	2007. SWAMP Data for the Owens Hydrologic Unit
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:	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:	One station, "Mammoth Creek at Twin Lakes" was sampled.
Temporal Representation:	Twelve 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	8213
Pollutant:	Beryllium
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
Weight of Evidence:	This pollutant is being considered for placement on the section 303(d) list under section 3.1 of the Listing Policy. Under section 3.1 a single line of evidence is necessary to assess listing status. Two lines of evidence are available in the administrative record to assess this pollutant. None of the samples exceed the 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. There are no California or federal freshwater aquatic life criteria for beryllium. None of 12 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.
RWQCB Board Decision / Staff 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.
SWRCB Board Decision / Staff Recommendation:
USEPA Decision:

Lines of Evidence (LOEs) for Decision ID 8213

LOE ID:	6967
Pollutant:	Beryllium
LOE Subgroup:	Pollutant-Water
Matrix:	Water
Fraction:	Dissolved
Beneficial Use:	Cold Freshwater Habitat
Number of Samples:	12
Number of Exceedances:	0
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 12 quarterly samples were below the detection level.
Data Reference:	2007. SWAMP Data for the Owens Hydrologic Unit
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:	2007. 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:	Twelve 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):
LOE ID:	6966
Pollutant:	Beryllium
LOE Subgroup:	Pollutant-Water
Matrix:	Water
Fraction:	Total
Beneficial Use:	Municipal & Domestic Supply
Number of Samples:	12
Number of Exceedances:	0
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 12 samples were below the detection level. Per Listing Policy Secton 6.1.5.5 the MCL is presumed to be attained.
Data Reference:	2007. Water Quality Control Plan for the Lahontan Region (as amended).
	2007. SWAMP Data for the Owens Hydrologic Unit
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:	2007. 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:	Twelve 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	9469
Pollutant:	Boron
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
Weight of Evidence:	This pollutant is being considered for placement on the section 303(d) list under section 3.1 of the Listing Policy. Under section 3.1 a single line of evidence is necessary to assess listing status. Two lines of evidence are available in the administrative record to assess this pollutant. None of the samples exceed the site specific water quality objective or the California State Notification 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 4 samples exceeded the site-specific objective. None of 4 samples exceeded the California State Notification 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.
RWQCB Board Decision / Staff 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.
SWRCB Board Decision / Staff Recommendation:
USEPA Decision:

Lines of Evidence (LOEs) for Decision ID 9469

LOE ID:	7146
Pollutant:	Boron
LOE Subgroup:	Pollutant-Water
Matrix:	Water
Fraction:	Dissolved
Beneficial Use:	Municipal & Domestic Supply
Number of Samples:	4
Number of Exceedances:	0
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 2004 and July 2005. The concentration of dissolved boron in one of four samples was below the detection level. Two samples were estimated values. The dissolved boron concentration in the fourth sample was 7.5 ug/L. The criterion was not exceeded.
Data Reference:	2007. SWAMP Data for the Owens Hydrologic Unit
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 Twin Lakes" was sampled.
Temporal Representation:	Four samples wre 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):
LOE ID:	9119
Pollutant:	Boron
LOE Subgroup:	Pollutant-Water
Matrix:	Water
Fraction:	Dissolved
Beneficial Use:	Cold Freshwater Habitat
Number of Samples:	4
Number of Exceedances:	0
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 2004 and July 2005. The concentration of dissolved boron in one of four samples was below the detection level. Two samples were estimated values. The dissolved boron concentration in the fourth sample was 7.5 ug/L. The objective was not exceeded..
Data Reference:	2007. SWAMP Data for the Owens Hydrologic Unit
Water Quality Objective/Criterion:	The applicable water body-specific objective, from Lahontan Basin Plan Table 3-17, is an annual average boron concentration of 0.03 mg/L (equivalent to 30 ug/L) and a 90th percentile value of 0.05 mg/L (equivalent to 50 ug/L).
Objective/Criterion Reference:	Compilation of Water Quality Goals
Evaluation Guideline:
Guideline Reference:
Spatial Representation:	One station, "Mammoth Creek at Twin Lakes" was sampled.
Temporal Representation:	Four samples wre 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	8214
Pollutant:	Cadmium
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
Weight of Evidence:	This pollutant is being considered for placement on the section 303(d) list under section 3.1 of the Listing Policy. Under section 3.1 a single line of evidence is necessary to assess listing status. Two lines of evidence are available in the administrative record to assess this pollutant. None of the samples exceed the applicable water quality objective and California Toxics Rule standards. (Concentrations of total and dissolved cadmium were below detection levels, and under Listing Policy section 6.1.5.5 the applicable standards are considered to be attained.) 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 twelve dissolved cadmium samples exceeded the California Toxics Rule standards. None of twelve total cadmium samples exceeded the Maximum Contaminant Level and this does not exceed the allowable frequency listed in Table 3.1 of the Listing Policy. 4. Pursuant to section 3.11 of the Listing Policy, no additional data and information are available indicating that standards are not met.
RWQCB Board Decision / Staff 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.
SWRCB Board Decision / Staff Recommendation:
USEPA Decision:

Lines of Evidence (LOEs) for Decision ID 8214

LOE ID:	6969
Pollutant:	Cadmium
LOE Subgroup:	Pollutant-Water
Matrix:	Water
Fraction:	Dissolved
Beneficial Use:	Cold Freshwater Habitat
Number of Samples:	12
Number of Exceedances:	0
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 12 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
Water Quality Objective/Criterion:	The California Toxics Rule standards for protection of freshwater aquatic life are dependent on hardness. At the hardness levels reported for this station, the acute (1 hour average) standard for cadmium ranges from 0.53 to 3.42 ug/L, and the chronic (4 day average) standard ranges from 0.53 to 1.92 ug/L.
Objective/Criterion Reference:	2007. 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:	Twelve 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):
LOE ID:	6968
Pollutant:	Cadmium
LOE Subgroup:	Pollutant-Water
Matrix:	Water
Fraction:	Total
Beneficial Use:	Municipal & Domestic Supply
Number of Samples:	12
Number of Exceedances:	0
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 12 samples were all below the detection level or estimated values.
Data Reference:	2007. SWAMP Data for the Owens Hydrologic Unit
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:	2007. 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:	Twelve 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	9461
Pollutant:	Calcium
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
Weight of Evidence:	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 water quality 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. Because there are no applicable standards or criteria 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.
RWQCB Board Decision / Staff 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 there are no applicable water quality standards or criteria.
SWRCB Board Decision / Staff Recommendation:
USEPA Decision:

Lines of Evidence (LOEs) for Decision ID 9461

LOE ID:	7135
Pollutant:	Calcium
LOE Subgroup:	Pollutant-Water
Matrix:	Water
Fraction:	Total
Beneficial Use:	Municipal & Domestic Supply
Number of Samples:	12
Number of Exceedances:	0
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 12 samples ranged from 4.8 to 19.3 mg/L.
Data Reference:	2007. SWAMP Data for the Owens Hydrologic Unit
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:	2007. 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:	Twelve 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):
LOE ID:	7136
Pollutant:	Calcium
LOE Subgroup:	Pollutant-Water
Matrix:	Water
Fraction:	Dissolved
Beneficial Use:	Cold Freshwater Habitat
Number of Samples:	12
Number of Exceedances:	0
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 12 samples ranged from 5.15 to 21.6 mg/L.
Data Reference:	2007. SWAMP Data for the Owens Hydrologic Unit
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:	2007. 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:	Twelve 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. 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	8164
Pollutant:	Chloride
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
Weight of Evidence:	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 exceed the Maximum Contaminant Level. One of five annual average datapoints 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 seasonal and annual variability expected in streamflows and constituent concentrations in streams of the Lahontan Region. 3. None of 12 samples exceeded the Maximum Contaminant Level. One of five 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.
RWQCB Board Decision / Staff 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.
SWRCB Board Decision / Staff Recommendation:
USEPA Decision:

Lines of Evidence (LOEs) for Decision ID 8164

LOE ID:	6951
Pollutant:	Chloride
LOE Subgroup:	Pollutant-Water
Matrix:	Water
Fraction:	Dissolved
Beneficial Use:	Cold Freshwater Habitat
Number of Samples:	5
Number of Exceedances:	1
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 chloride samples included six estimated or below detection level values. The remainder ranged from 0.20 to 2.86 mg/L. The annual average objective was exceeded in one of five years.
Data Reference:	2007. SWAMP Data for the Owens Hydrologic Unit
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 chloride concentration of 0.6 mg/L and a 90th percentile value of 1.0 mg/L.
Objective/Criterion Reference:	2007. 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 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):
LOE ID:	6952
Pollutant:	Chloride
LOE Subgroup:	Pollutant-Water
Matrix:	Water
Fraction:	Dissolved
Beneficial Use:	Municipal & Domestic Supply
Number of Samples:	16
Number of Exceedances:	0
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 chloride samples included six estimated or below detection level values. The remainder ranged from 0.20 to 2.86 mg/L. The MCL was not exceeded.
Data Reference:	2007. SWAMP Data for the Owens Hydrologic Unit
Water Quality Objective/Criterion:	California Maximum Contaminant Levels (MCLs) apply to ambient waters under the Lahontan Basin Plan's "Chemical Constituents" objective. The MCL for chloride is 250 mg/L.
Objective/Criterion Reference:	2007. 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 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.
QAPP Information:	The data meet the quality assurance requirements of the SWAMP QAPP.
QAPP Information Reference(s):

DECISION ID	8215
Pollutant:	Chromium (total)
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
Weight of Evidence:	This pollutant is being considered for placement on the section 303(d) list under section 3.1 of the Listing Policy. Under section 3.1 a single line of evidence is necessary to assess listing status. Two lines of evidence are available in the administrative record to assess this pollutant. None of the samples exceed the applicable water quality objective or California Toxics Rule (CTR) standards. 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 12 dissolved chromium samples exceeded the California Toxics Rule standards. None of 12 total chromium samples exceeded the Maximum Contaminant Level, and this does not exceed the allowable frequency listed in Table 3.1 of the Listing Policy. 4. Pursuant to section 3.11 of the Listing Policy, no additional data and information are available indicating that standards are not met.
RWQCB Board Decision / Staff 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.
SWRCB Board Decision / Staff Recommendation:
USEPA Decision:

Lines of Evidence (LOEs) for Decision ID 8215

LOE ID:	6970
Pollutant:	Chromium (total)
LOE Subgroup:	Pollutant-Water
Matrix:	Water
Fraction:	Dissolved
Beneficial Use:	Cold Freshwater Habitat
Number of Samples:	12
Number of Exceedances:	0
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 appoximately quarterly under the Region 6 SWAMP program between 2001 and 2005. Concentrations of dissolved chromium in 12 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
Water Quality Objective/Criterion:	The California Toxics Rule (CTR) standards for dissolved Cr VI for protection freshwater aquatic life include a 4 day average of 11 ug/L and a 1 hour average of 16 ug/L. For Cr III, the CTR standards are dependent on hardness. At the hardness levels reported for this station, the acute (1 hour average) toxicity standard ranges from 121.52 to 467.07 ug/L. The chronic (4-day average) toxicity standard ranges from 39.2 to 151.51 ug/L.
Objective/Criterion Reference:	2007. 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:	Twelve 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):
LOE ID:	6971
Pollutant:	Chromium (total)
LOE Subgroup:	Pollutant-Water
Matrix:	Water
Fraction:	Total
Beneficial Use:	Municipal & Domestic Supply
Number of Samples:	12
Number of Exceedances:	0
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 12 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
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:	2007. 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:	Twelve 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	9462
Pollutant:	Cobalt
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
Weight of Evidence:	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 state 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. 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. Because there are no applicable standards or criteria, 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.
RWQCB Board Decision / Staff 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 there are no applicable state or federal standards or criteria.
SWRCB Board Decision / Staff Recommendation:
USEPA Decision:

Lines of Evidence (LOEs) for Decision ID 9462

LOE ID:	7163
Pollutant:	Cobalt
LOE Subgroup:	Pollutant-Water
Matrix:	Water
Fraction:	Dissolved
Beneficial Use:	Cold Freshwater Habitat
Number of Samples:	12
Number of Exceedances:	0
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 12 samples ranged from 0.032 to 0.28 ug/L.
Data Reference:	2007. SWAMP Data for the Owens Hydrologic Unit
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:	2007. 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:	Twelve 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. 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):
LOE ID:	7165
Pollutant:	Cobalt
LOE Subgroup:	Pollutant-Water
Matrix:	Water
Fraction:	Total
Beneficial Use:	Municipal & Domestic Supply
Number of Samples:	12
Number of Exceedances:	0
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 4 of 12 samples were below the detection level. Concentrations in the remaining 8 samples ranged from 0.042 to 0.192 ug/L.
Data Reference:	2007. SWAMP Data for the Owens Hydrologic Unit
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:	2007. 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:	Twelve 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	8216
Pollutant:	Copper
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
Weight of Evidence:	This pollutant is being considered for placement on the section 303(d) list under section 3.1 of the Listing Policy. Under section 3.1 a single line of evidence is necessary to assess listing status. Two lines of evidence are available in the administrative record to assess this pollutant. None of the samples exceed the applicable water quality objective and California Toxics Rule standards. 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 12 dissolved copper samples exceeded the California Toxics Rule standards. None of 12 total copper samples exceeded the Maximum Contaminant Level and this does not exceed the allowable frequency listed in Table 3.1 of the Listing Policy. 4. Pursuant to section 3.11 of the Listing Policy, no additional data and information are available indicating that standards are not met.
RWQCB Board Decision / Staff 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.
SWRCB Board Decision / Staff Recommendation:
USEPA Decision:

Lines of Evidence (LOEs) for Decision ID 8216

LOE ID:	6972
Pollutant:	Copper
LOE Subgroup:	Pollutant-Water
Matrix:	Water
Fraction:	Dissolved
Beneficial Use:	Cold Freshwater Habitat
Number of Samples:	12
Number of Exceedances:	0
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 12 samples for dissolved copper, two were below the detection level, seven were estimated values, and the remaining samples were 0.2, 0.4 and 0.8 ug/L. The CTR standards were not violated
Data Reference:	2007. SWAMP Data for the Owens Hydrologic Unit
Water Quality Objective/Criterion:	The California Toxics Rule's (CTR's) freshwater aquatic life standards for copper are dependent on hardness. At the hardness levels reported for SWAMP samples at this station, the acute toxicity standard ranges from 2.62 to 9.91 ug/L, and the chronic toxicity standard ranges from 42.98 to 136.62 ug/L
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:	One station, "Mammoth Creek at Twin Lakes" was sampled.
Temporal Representation:	Twelve 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):
LOE ID:	6973
Pollutant:	Copper
LOE Subgroup:	Pollutant-Water
Matrix:	Water
Fraction:	Total
Beneficial Use:	Municipal & Domestic Supply
Number of Samples:	12
Number of Exceedances:	0
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 5 of 12 samples were below the detection level. The remaining 7 samples were estimated values. The MCLs were not exceeded.
Data Reference:	2007. SWAMP Data for the Owens Hydrologic Unit
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:	2007. 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:	Twelve 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	9463
Pollutant:	Dissolved oxygen saturation
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
Weight of Evidence:	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. Two of the samples exceed the water quality objective. Based on the readily available data and information, the weight of evidence indicates that there is sufficient justification against placing this water segment-pollutant combination on the section 303(d) list in the Water Quality Limited Segments category. This conclusion is based on the staff findings that: 1. The data used satisfy the data quality requirements of section 6.1.4 of the Policy. 2. The data used 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. Two of eight 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.
RWQCB Board Decision / Staff 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.
SWRCB Board Decision / Staff Recommendation:
USEPA Decision:

Lines of Evidence (LOEs) for Decision ID 9463

LOE ID:	7273
Pollutant:	Dissolved oxygen saturation
LOE Subgroup:	Pollutant-Water
Matrix:	Water
Fraction:	Dissolved
Beneficial Use:	Cold Freshwater Habitat
Number of Samples:	8
Number of Exceedances:	2
Data and Information Type:	Fixed station physical/chemical (conventional plus toxic pollutants)
Data Used to Assess Water Quality:	The U.S. Geological Survey sampled percent saturation of dissolved oxygen at this station under the Region 6 SWAMP program between 2003 and 2005. Percent saturation in 8 quarterly samples ranged from 58 to 119 percent. Two samples were below 80 percent.
Data Reference:	2007. SWAMP Data for the Owens Hydrologic Unit
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:	2007. 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:	Eight quarterly samples were collected between November 2003 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	8225
Pollutant:	Fecal Coliform
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
Weight of Evidence:	This pollutant is being considered for placement on the section 303(d) list under section 3.3 of the Listing Policy. Under section 3.3 a single line of evidence is necessary to assess listing status. Two lines of evidence are available in the administrative record to assess this pollutant. None of the samples exceed the water quality objective. Based on the readily available data and information, the weight of evidence indicates that there is sufficient justification against placing this water segment-pollutant combination on the section 303(d) list in the Water Quality Limited Segments category. This conclusion is based on the staff findings that: 1. The data used satisfy the data quality requirements of section 6.1.4 of the Policy. 2. The data used do not satisfy the data quantity requirements of section 6.1.5 of the Policy. Quarterly samples do not capture the seasonal and annual variability expected in streamflows and fecal coliform counts in streams of the Lahontan Region. The water quality objective calls for five samples to be collected within a30 day period. 3. None of five 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.
RWQCB Board Decision / Staff 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.
SWRCB Board Decision / Staff Recommendation:
USEPA Decision:

Lines of Evidence (LOEs) for Decision ID 8225

LOE ID:	7058
Pollutant:	Fecal Coliform
LOE Subgroup:	Pollutant-Water
Matrix:	Water
Fraction:	None
Beneficial Use:	Municipal & Domestic Supply
Number of Samples:	5
Number of Exceedances:	0
Data and Information Type:	Water column surveys (e.g. fecal coliform)
Data Used to Assess Water Quality:	The U.S. Geological Survey sampled this station under the Region 6 SWAMP program between 2004 and 2005. Three of five quarterly samples were below the detection level, and the remaining two samples were estimated valules. The objective was not exceeded.
Data Reference:	2007. Water Quality Control Plan for the Lahontan Region (as amended).
	2007. SWAMP Data for the Owens Hydrologic Unit
Water Quality Objective/Criterion:	The Lahontan Basin Plan's objective for coliform bacteria states: “Waters shall not contain concentrations of coliform organisms attributable to anthropogenic sources, including human and livestock wastes. The fecal coliform concentration during any 30-day period shall not exceed a log mean of 20/100 ml, nor shall more than 10 percent of all samples collected during any 30-day period exceed 40/100 ml. The log mean shall ideally be based on a minimum of not less than five samples collected as evenly spaced as practicable during any 30-day period. However, a log mean concentration exceeding 20/100 ml for any 30-day period shall indicate violation of this objective even if fewer than five samples were collected.”
Objective/Criterion Reference:	2007. 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:	Five quarterly samples were collected 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):
LOE ID:	7059
Pollutant:	Fecal Coliform
LOE Subgroup:	Pollutant-Water
Matrix:	Water
Fraction:	None
Beneficial Use:	Water Contact Recreation
Number of Samples:	5
Number of Exceedances:	0
Data and Information Type:	Water column surveys (e.g. fecal coliform)
Data Used to Assess Water Quality:	The U.S. Geological Survey sampled this station under the Region 6 SWAMP program between 2004 and 2005. Three of five quarterly samples were below the detection level, and the remaining two samples were estimated valules. The objective was not exceeded.
Data Reference:	2007. SWAMP Data for the Owens Hydrologic Unit
Water Quality Objective/Criterion:	The Lahontan Basin Plan's objective for coliform bacteria states: "Waters shall not contain concentrations of coliform organisms attributable to anthropogenic sources, including human and livestock wastes. The fecal coliform concentration during any 30-day period shall not exceed a log mean of 20/100 ml, nor shall more than 10 percent of all samples collected during any 30-day period exceed 40/100 ml. The log mean shall ideally be based on a minimum of not less than five samples collected as evenly spaced as practicable during any 30-day period. However, a log mean concentration exceeding 20/100 ml for any 30-day period shall indicate violation of this objective even if fewer than five samples were collected."
Objective/Criterion Reference:	2007. 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:	Five quarterly samples were collected 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	9814
Pollutant:	Hardness
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
Weight of Evidence:	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. 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.
RWQCB Board Decision / Staff 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 there are no applicable water quality standards or criteria.
SWRCB Board Decision / Staff Recommendation:
USEPA Decision:

Lines of Evidence (LOEs) for Decision ID 9814

LOE ID:	7132
Pollutant:	Hardness
LOE Subgroup:	Pollutant-Water
Matrix:	Water
Fraction:	None
Beneficial Use:	Cold Freshwater Habitat
Number of Samples:	12
Number of Exceedances:	0
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.
Data Reference:	2007. SWAMP Data for the Owens Hydrologic Unit
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:	2007. Water Quality Control Plan for the Lahontan Region (as amended).
	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 Twin Lakes" was sampled. Hardness was calculated for 12 samples. It ranged from 15.87 to 82.14 mg equivalent CaCO3.
Temporal Representation:	Hardness was calculated for 12 samples taken approximately quartely 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	9468
Pollutant:	Iron
Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	New Decision
Revision Status	Revised
Impairment from Pollutant or Pollution:	Pollutant
Weight of Evidence:	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 USEPA aquatic life criterion. Four of the samples exceed the California Maximum Contaminant Level (MCL). However, listing is not recommended because the data are not temporally representative. Based on the readily available data and information, the weight of evidence indicates that there is sufficient justification against placing this water segment-pollutant combination on the section 303(d) list in the Water Quality Limited Segments category. This conclusion is based on the staff findings that: 1. The data used satisfy the data quality requirements of section 6.1.4 of the Policy. 2. The data used do not satisfy the data quantity requirements of section 6.1.5 of the Policy. Quarterly samples do not capture the full range of seasonal and annual variability expected in streamflows and constituent concentrations in streams of the Lahontan Region. 3. Four of 12 samples exceeded the MCL and this exceeds the allowable frequency listed in Table 3.1 of the Listing Policy. 4. Pursuant to section 3.11 of the Listing Policy, no additional data and information are available indicating that standards are not met.
RWQCB Board Decision / Staff 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, although one of the applicable water quality standards is being exceeded, the data are not temporally representative.
SWRCB Board Decision / Staff Recommendation:
USEPA Decision:

Lines of Evidence (LOEs) for Decision ID 9468

LOE ID:	6974
Pollutant:	Iron
LOE Subgroup:	Pollutant-Water
Matrix:	Water
Fraction:	Dissolved
Beneficial Use:	Cold Freshwater Habitat
Number of Samples:	12
Number of Exceedances:	0
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 12 samples ranged from 46 to 195 ug/L. The criterion was not exceeded.
Data Reference:	2007. SWAMP Data for the Owens Hydrologic Unit
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:	National recommended water quality criteria: 2002. EPA-822-R-02-047 Washington, D.C. USEPA
Evaluation Guideline:
Guideline Reference:
Spatial Representation:	One station, "Mammoth Creek at Twin Lakes" was sampled.
Temporal Representation:	Twelve 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):
LOE ID:	6975
Pollutant:	Iron
LOE Subgroup:	Pollutant-Water
Matrix:	Water
Fraction:	Total
Beneficial Use:	Municipal & Domestic Supply
Number of Samples:	12
Number of Exceedances:	4
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 12 samples ranged from 110 to 470 ug/L. Four of these 12 samples exceeded the State MCL.
Data Reference:	2007. SWAMP Data for the Owens Hydrologic Unit
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:	2007. 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:	Twelve 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	8217
Pollutant:	Lead
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
Weight of Evidence:	This pollutant is being considered for placement on the section 303(d) list under section 3.1 of the Listing Policy. Under section 3.1 a single line of evidence is necessary to assess listing status. Two lines of evidence are available in the administrative record to assess this pollutant. None of the samples exceed the applicable water quality objective or California Toxics Rule standards. 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 twelve dissolved lead samples exceeded California Toxics Rule standards. None of twelve total lead samples exceeded the Maximum Contaminant Level and this does not exceed the allowable frequency listed in Table 3.1 of the Listing Policy. 4. Pursuant to section 3.11 of the Listing Policy, no additional data and information are available indicating that standards are not met.
RWQCB Board Decision / Staff 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.
SWRCB Board Decision / Staff Recommendation:
USEPA Decision:

Lines of Evidence (LOEs) for Decision ID 8217

LOE ID:	6977
Pollutant:	Lead
LOE Subgroup:	Pollutant-Water
Matrix:	Water
Fraction:	Total
Beneficial Use:	Municipal & Domestic Supply
Number of Samples:	12
Number of Exceedances:	0
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 twelve samples, five had concentrations of total lead below the detection level. Concentrations in 6 samples were estimated values. One sample had a total lead concentation of 0.16 ug/L. The MCL was not violated.
Data Reference:	2007. SWAMP Data for the Owens Hydrologic Unit
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:	2007. 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:	Twelve 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):
LOE ID:	6976
Pollutant:	Lead
LOE Subgroup:	Pollutant-Water
Matrix:	Water
Fraction:	Dissolved
Beneficial Use:	Cold Freshwater Habitat
Number of Samples:	12
Number of Exceedances:	0
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 twelve samples were all 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
Water Quality Objective/Criterion:	The California Toxics Rule (CTR) freshwater aquatic life standards for lead are dependent on hardness. At the hardness levels reported for this station, the acute (1 hour) toxicity standard ranges from 6.20 to 50.27 g/L. The chronic (4 day average) toxicity standard ranges from 0.24 to 1.9 ug/L.
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:	One station, "Mammoth Creek at Twin Lakes" was sampled.
Temporal Representation:	Twelve 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	9464
Pollutant:	Magnesium
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
Weight of Evidence:	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 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.
RWQCB Board Decision / Staff 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 there are no applicable water quality standards or criteria..
SWRCB Board Decision / Staff Recommendation:
USEPA Decision:

Lines of Evidence (LOEs) for Decision ID 9464

LOE ID:	7138
Pollutant:	Magnesium
LOE Subgroup:	Pollutant-Water
Matrix:	Water
Fraction:	Total
Beneficial Use:	Municipal & Domestic Supply
Number of Samples:	12
Number of Exceedances:	0
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 12 samples ranged from 0.71 to 6.22 mg/L.
Data Reference:	2007. SWAMP Data for the Owens Hydrologic Unit
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:	2007. 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:	Twelve 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):
LOE ID:	7137
Pollutant:	Magnesium
LOE Subgroup:	Pollutant-Water
Matrix:	Water
Fraction:	Dissolved
Beneficial Use:	Cold Freshwater Habitat
Number of Samples:	12
Number of Exceedances:	0
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 12 samples ranged from 0.731 to 6.85 mg/L.
Data Reference:	2007. SWAMP Data for the Owens Hydrologic Unit
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:	2007. 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:	Twelve 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. 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	8218
Pollutant:	Manganese
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
Weight of Evidence:	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 California or federal standards or criteria for manganese fo the protection of aquatic life. None of the samples exceed 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. There are no applicable California or federal standards or criteria for assessment of the 12 dissolved manganese samples. None of 12 samples for total manganese 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.
RWQCB Board Decision / Staff 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.
SWRCB Board Decision / Staff Recommendation:
USEPA Decision:

Lines of Evidence (LOEs) for Decision ID 8218

LOE ID:	6978
Pollutant:	Manganese
LOE Subgroup:	Pollutant-Water
Matrix:	Water
Fraction:	Dissolved
Beneficial Use:	Cold Freshwater Habitat
Number of Samples:	12
Number of Exceedances:	0
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 ranged from 5 to 46 ug/L.
Data Reference:	2007. SWAMP Data for the Owens Hydrologic Unit
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:	2007. 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:	Twelve 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):
LOE ID:	6980
Pollutant:	Manganese
LOE Subgroup:	Pollutant-Water
Matrix:	Water
Fraction:	Total
Beneficial Use:	Municipal & Domestic Supply
Number of Samples:	12
Number of Exceedances:	0
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 were below the detection level in twelve samples. The MCL was not exceeded.
Data Reference:	2007. SWAMP Data for the Owens Hydrologic Unit
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:	2007. 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:	Twelve 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	9465
Pollutant:	Molybdenum
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
Weight of Evidence:	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.
RWQCB Board Decision / Staff 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 there are no applicable water quality standards or criteria..
SWRCB Board Decision / Staff Recommendation:
USEPA Decision:

Lines of Evidence (LOEs) for Decision ID 9465

LOE ID:	7157
Pollutant:	Molybdenum
LOE Subgroup:	Pollutant-Water
Matrix:	Water
Fraction:	Dissolved
Beneficial Use:	Cold Freshwater Habitat
Number of Samples:	12
Number of Exceedances:	0
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 12 samples ranged from 1.7 to 3 ug/L.
Data Reference:	2007. SWAMP Data for the Owens Hydrologic Unit
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:	2007. 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:	Twelve 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. 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):
LOE ID:	7149
Pollutant:	Molybdenum
LOE Subgroup:	Pollutant-Water
Matrix:	Water
Fraction:	Total
Beneficial Use:	Municipal & Domestic Supply
Number of Samples:	12
Number of Exceedances:	0
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 12 samples ranged from 1.7 to 2.9 ug/L. The criterion was not violated.
Data Reference:	2007. SWAMP Data for the Owens Hydrologic Unit
Water Quality Objective/Criterion:	There are no applicable water quality standards or criteria for molybdenum for protection of the Municipal and Domestic Supply use..
Objective/Criterion Reference:	2007. 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:	Twelve 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	8219
Pollutant:	Nickel
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
Weight of Evidence:	This pollutant is being considered for placement on the section 303(d) list under section 3.1 of the Listing Policy. Under section 3.1 a single line of evidence is necessary to assess listing status. Two lines of evidence are available in the administrative record to assess this pollutant. None of the samples exceed the water quality objective. Based on the readily available data and information, the weight of evidence indicates that there is sufficient justification against placing this water segment-pollutant combination on the section 303(d) list in the Water Quality Limited Segments category. This conclusion is based on the staff findings that: 1. The data used satisfy the data quality requirements of section 6.1.4 of the Policy. 2. The data used do not satisfy the data quantity requirements of section 6.1.5 of the Policy. Quarterly samples do not capture the seasonal and annual variability expected in streamflows and constituent concentrations in streams of the Lahontan Region. 3. None of 12 dissolved nickel samples exceeded California Toxics Rule standards. None of 12 total nickel samples exceeded the Maximum Contaminant Level and this does not exceed the allowable frequency listed in Table 3.1 of the Listing Policy. 4. Pursuant to section 3.11 of the Listing Policy, no additional data and information are available indicating that standards are not met.
RWQCB Board Decision / Staff 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.
SWRCB Board Decision / Staff Recommendation:
USEPA Decision:

Lines of Evidence (LOEs) for Decision ID 8219

LOE ID:	6984
Pollutant:	Nickel
LOE Subgroup:	Pollutant-Water
Matrix:	Water
Fraction:	Dissolved
Beneficial Use:	Cold Freshwater Habitat
Number of Samples:	7
Number of Exceedances:	0
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 quarterly between 2003 and 2005. Concentrations of dissolved nickel in 7 samples ranged from 0.2 to 0.88 ug/L. The CTR standards were not exceeded.
Data Reference:	2007. SWAMP Data for the Owens Hydrologic Unit
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 216.18 to 290.12 ug/L, and the chronic toxicity standard ranges from 24.04 to 32.26 ug/L
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:	One station at the Twin Lakes outlet was sampled.
Temporal Representation:	Seven quarterly samples were collected between 2001 and 2005.
Environmental Conditions:	The unnamed tributary enters Mammoth Creek from the south. 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):
LOE ID:	6983
Pollutant:	Nickel
LOE Subgroup:	Pollutant-Water
Matrix:	Water
Fraction:	Total
Beneficial Use:	Municipal & Domestic Supply
Number of Samples:	12
Number of Exceedances:	0
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 four of twelve samples were below the detection level. Concentrations in the remaining 8 samples ranged from 0.21 to 0.42 ug/L. The MCL was not violated.
Data Reference:	2007. SWAMP Data for the Owens Hydrologic Unit
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:	2007. 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:	Twelve 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	8269
Pollutant:	Nitrate
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
Weight of Evidence:	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 calculated nitrate concentrations exceed the site-specific water quality objective or the 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 nitrate concentrations calculated from 16 samples for nittrite plus nitrate and 16 samples for nitrite exceeded the applicable water quality objectives 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.
RWQCB Board Decision / Staff 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.
SWRCB Board Decision / Staff Recommendation:
USEPA Decision:

Lines of Evidence (LOEs) for Decision ID 8269

LOE ID:	7092
Pollutant:	Nitrate
LOE Subgroup:	Pollutant-Water
Matrix:	Water
Fraction:	Dissolved
Beneficial Use:	Municipal & Domestic Supply
Number of Samples:	16
Number of Exceedances:	0
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. The MCL was not exceeded.
Data Reference:	2007. SWAMP Data for the Owens Hydrologic Unit
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 expressed "as nitrate," equivalent to 10 mg/L expressed "as N." .
Objective/Criterion Reference:	2007. 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:	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):
LOE ID:	7091
Pollutant:	Nitrate
LOE Subgroup:	Pollutant-Water
Matrix:	Water
Fraction:	Dissolved
Beneficial Use:	Cold Freshwater Habitat
Number of Samples:	5
Number of Exceedances:	0
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
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:	2007. 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:	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	9815
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:	New Decision
Revision Status	Revised
Impairment from Pollutant or Pollution:	Pollutant
Weight of Evidence:	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 Califorrnia Maximum Contaminant Level (MCL). No biological data are available for assessment of compliance with 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. None of 16 samples exceeded the MCL and this does not exceed the allowable frequency listed in Table 3.1 of the Listing Policy. There were no biolgical data available for assessment of compliance with the objective for biostimulatory substances. 4. Pursuant to section 3.11 of the Listing Policy, no additional data and information are available indicating that standards are not met.
RWQCB Board Decision / Staff 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 one of the applicable water quality standards is not being exceeded and no biological data are available to determine compliance with the other.
SWRCB Board Decision / Staff Recommendation:
USEPA Decision:

Lines of Evidence (LOEs) for Decision ID 9815

LOE ID:	7099
Pollutant:	Nitrate/Nitrite (Nitrite + Nitrate as N)
LOE Subgroup:	Pollutant-Water
Matrix:	Water
Fraction:	Dissolved
Beneficial Use:	Cold Freshwater Habitat
Number of Samples:	16
Number of Exceedances:	0
Data and Information Type:	Fixed station physical/chemical (conventional plus toxic pollutants)
Data Used to Assess Water Quality:	The U.S. Geological Survey sampled this station under the Region 6 SWAMP program between 2001 and 2005. Concentrations of nitrite plus nitrate in 16 quarterly samples ranged from below the detection level (8 samples) to 0.023 mg/L..No data on algae or macrophytes are available for assessment of compliance with the objective for biostimulatory substances.
Data Reference:	2007. SWAMP Data for the Owens Hydrologic Unit
Water Quality Objective/Criterion:	There are no site- specific numeric objectives in the Lahontan Basin Plan for nitrite plus nitrate for Mammoth Creek. (The numeric objectives for nitrate and Total Nitrogen are assessed separately.) The regionwide narrative objective for biostimulatory substances states: “Waters shall not contain biostimulatory substances in concentrations that promote aquatic growths to the extent that such growths cause nuisance or adversely affect the water for beneficial uses.”
Objective/Criterion Reference:	2007. 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 for nitrite plus nitrate 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):
LOE ID:	21204
Pollutant:	Nitrate/Nitrite (Nitrite + Nitrate as N)
LOE Subgroup:	Pollutant-Water
Matrix:	Water
Fraction:	Dissolved
Beneficial Use:	Municipal & Domestic Supply
Number of Samples:	16
Number of Exceedances:	0
Data and Information Type:	Fixed station physical/chemical (conventional plus toxic pollutants)
Data Used to Assess Water Quality:	The U.S. Geological Survey sampled this station under the Region 6 SWAMP program between 2001 and 2005. Concentrations of nitrite plus nitrate in 16 quarterly samples ranged from below the detection level (8 samples) to 0.023 mg/L..The MCL was not exceeded.
Data Reference:	2007. SWAMP Data for the Owens Hydrologic Unit
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.
Objective/Criterion Reference:	2007. 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 for nitrite plus nitrate 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	9816
Pollutant:	Nitrite
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
Weight of Evidence:	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 exceed 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 16 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.
RWQCB Board Decision / Staff 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.
SWRCB Board Decision / Staff Recommendation:
USEPA Decision:

Lines of Evidence (LOEs) for Decision ID 9816

LOE ID:	7065
Pollutant:	Nitrite
LOE Subgroup:	Pollutant-Water
Matrix:	Water
Fraction:	Dissolved
Beneficial Use:	Municipal & Domestic Supply
Number of Samples:	16
Number of Exceedances:	0
Data and Information Type:	Fixed station physical/chemical (conventional plus toxic pollutants)
Data Used to Assess Water Quality:	The U.S. Geological Survey sampled this station under the Region 6 SWAMP program between 2001 and 2005. Concentrations of nitrite in 8 of 16 samples were below the detection level. The remaining samples ranged from 0.001 to 0.002 mg/L. The MCL was not exceeded..
Data Reference:	2007. SWAMP Data for the Owens Hydrologic Unit
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:	2007. 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 were collected 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	8165
Pollutant:	Oxygen, Dissolved
Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	New Decision
Revision Status	Revised
Impairment from Pollutant or Pollution:	Pollutant
Weight of Evidence:	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. Four of the samples exceed the water quality objective. Based on the readily available data and information, the weight of evidence indicates that there is sufficient justification against placing this water segment-pollutant combination on the section 303(d) list in the Water Quality Limited Segments category. This conclusion is based on the staff findings that: 1. The data used satisfy the data quality requirements of section 6.1.4 of the Policy. 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. Four of twelve 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.
RWQCB Board Decision / Staff 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.
SWRCB Board Decision / Staff Recommendation:
USEPA Decision:

Lines of Evidence (LOEs) for Decision ID 8165

LOE ID:	6955
Pollutant:	Oxygen, Dissolved
LOE Subgroup:	Pollutant-Water
Matrix:	Water
Fraction:	Dissolved
Beneficial Use:	Cold Freshwater Habitat
Number of Samples:	15
Number of Exceedances:	4
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. The dissolved oxygen concentrations in 15 quarterly samples ranged from 6 to 10.2 mg/L. Four samples were below the 8 mg/L minimum concentration.
Data Reference:	2007. SWAMP Data for the Owens Hydrologic Unit
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:	2007. 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:	Fifteen samples 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	9817
Pollutant:	Phosphate
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
Weight of Evidence:	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.
RWQCB Board Decision / Staff 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.
SWRCB Board Decision / Staff Recommendation:
USEPA Decision:

Lines of Evidence (LOEs) for Decision ID 9817

LOE ID:	7105
Pollutant:	Phosphate
LOE Subgroup:	Pollutant-Water
Matrix:	Water
Fraction:	Dissolved
Beneficial Use:	Cold Freshwater Habitat
Number of Samples:	4
Number of Exceedances:	0
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
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:	2007. 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:	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	9818
Pollutant:	Phosphorus
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
Weight of Evidence:	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 assessement whether any 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. No biological data are available for assessment whether any of the samples exceeds the objective for biostimulatory substances, 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.
RWQCB Board Decision / Staff 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 no biological data are available for determination of compliance with the applicable water quality objective.
SWRCB Board Decision / Staff Recommendation:
USEPA Decision:

Lines of Evidence (LOEs) for Decision ID 9818

LOE ID:	7100
Pollutant:	Phosphorus
LOE Subgroup:	Pollutant-Water
Matrix:	Water
Fraction:	Total
Beneficial Use:	Cold Freshwater Habitat
Number of Samples:	12
Number of Exceedances:	0
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 total phosphorus in 12 quarterly samples ranged from 0.012 to 0.039 mg/L..No data on algae or macrophytes are available for assessment of compliance with the objective for biostimulatory substances.
Data Reference:	2007. SWAMP Data for the Owens Hydrologic Unit
Water Quality Objective/Criterion:	There are no site- specific numeric objectives in the Lahontan Basin Plan for total phosphorus for Mammoth Creek. (The numeric objective for phosphate is assessed separately.) The regionwide narrative objective for biostimulatory substances states: “Waters shall not contain biostimulatory substances in concentrations that promote aquatic growths to the extent that such growths cause nuisance or adversely affect the water for beneficial uses.”
Objective/Criterion Reference:	2007. 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:	Twelve samples for total phosphorus 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	9819
Pollutant:	Sediment
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
Weight of Evidence:	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, based on quarterly sampling, is available in the administrative record to assess this pollutant. It includes 16 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.
RWQCB Board Decision / Staff 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 the available data are insufficient to determine baseline and trend conditions as required under Listing Policy section 3.10.
SWRCB Board Decision / Staff Recommendation:
USEPA Decision:

Lines of Evidence (LOEs) for Decision ID 9819

LOE ID:	7144
Pollutant:	Sediment
LOE Subgroup:	Pollutant-Water
Matrix:	Water
Fraction:	None
Beneficial Use:	Cold Freshwater Habitat
Number of Samples:	16
Number of Exceedances:	0
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 suspended sediment in 16 quarterly samples ranged from 1 to 6 mg/L. The USGS did 8 sediment discharge (load) calculations using quarterly flow (discharge) measurements taken concurrently with the sediment samples between 10/29/2003 and 7/21/05. Measured flows during this period ranged from 5.6 to 50 cubic feet per second. Calculated sediment discharge ranged from 0.03 to 0.14 tons per day.
Data Reference:	2007. SWAMP Data for the Owens Hydrologic Unit
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:	2007. 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 (2 to 4 per year) 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	8166
Pollutant:	Selenium
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
Weight of Evidence:	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. [NUMBER] line(s) of evidence is available in the administrative record to assess this pollutant. [NUMBER] of the samples exceed the water quality objective. Based on the readily available data and information, the weight of evidence indicates that there is sufficient justification against placing this water segment-pollutant combination on the section 303(d) list in the Water Quality Limited Segments category. This conclusion is based on the staff findings that: 1. The data used satisfy the data quality requirements of section 6.1.4 of the Policy. 2. The data used do not satisfy the data quantity requirements of section 6.1.5 of the Policy. Quarterly samples do not capture the seasonal and annual variability expected in streamflows and constituent concentrations in streams of the Lahontan Region. 3. None of 12 dissolved selenium samples exceeded the California Toxics Rule aquatic life standards. None of twelve total selenium samples exceeded the Maximum Contaminant Level and this does not exceed the allowable frequency listed in Table 3.1 of the Listing Policy. 4. Pursuant to section 3.11 of the Listing Policy, no additional data and information are available indicating that standards are not met.
RWQCB Board Decision / Staff 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.
SWRCB Board Decision / Staff Recommendation:
USEPA Decision:

Lines of Evidence (LOEs) for Decision ID 8166

LOE ID:	6959
Pollutant:	Selenium
LOE Subgroup:	Pollutant-Water
Matrix:	Water
Fraction:	Total
Beneficial Use:	Municipal & Domestic Supply
Number of Samples:	12
Number of Exceedances:	0
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 of the samples for total selenium were below detection levels, and two were estimated values. The MCL was not violated.
Data Reference:	2007. SWAMP Data for the Owens Hydrologic Unit
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:	2007. 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:	Twelve 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):
LOE ID:	6958
Pollutant:	Selenium
LOE Subgroup:	Pollutant-Water
Matrix:	Water
Fraction:	Dissolved
Beneficial Use:	Cold Freshwater Habitat
Number of Samples:	12
Number of Exceedances:	0
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 12 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
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:	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:	One station, "Mammoth Creek at Twin Lakes" was sampled.
Temporal Representation:	Twelve 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	8220
Pollutant:	Silver
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
Weight of Evidence:	This pollutant is being considered for placement on the section 303(d) list under section 3.1 of the Listing Policy. Under section 3.1 a single line of evidence is necessary to assess listing status. Two lines of evidence are available in the administrative record to assess this pollutant. None of the samples exceed the water quality objective. Based on the readily available data and information, the weight of evidence indicates that there is sufficient justification against placing this water segment-pollutant combination on the section 303(d) list in the Water Quality Limited Segments category. This conclusion is based on the staff findings that: 1. The data used satisfy the data quality requirements of section 6.1.4 of the Policy. 2. The data used do not satisfy the data quantity requirements of section 6.1.5 of the Policy. Quarterly samples do not capture the seasonal and annual variability expected in streamflows and constituent concentrations in streams of the Lahontan Region. 3. Silver concentrations in twelve dissolved silver samples and twelve total recoverable silver samples were all below detection levels. Under section 6.1.5.5 of the policy the applicable standards are considered to be attained. 4. None of twelve dissolved silver samples exceeded the California Toxics Rule standard. None of twelve total silver samples samples exceeded the Maximum Contaminant Level and this does not exceed the allowable frequency listed in Table 3.1 of the Listing Policy. 4. Pursuant to section 3.11 of the Listing Policy, no additional data and information are available indicating that standards are not met.
RWQCB Board Decision / Staff 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.
SWRCB Board Decision / Staff Recommendation:
USEPA Decision:

Lines of Evidence (LOEs) for Decision ID 8220

LOE ID:	6989
Pollutant:	Silver
LOE Subgroup:	Pollutant-Water
Matrix:	Water
Fraction:	Total
Beneficial Use:	Municipal & Domestic Supply
Number of Samples:	12
Number of Exceedances:	0
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 12 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
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:	2007. 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:	Twelve 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):
LOE ID:	6987
Pollutant:	Silver
LOE Subgroup:	Pollutant-Water
Matrix:	Water
Fraction:	Dissolved
Beneficial Use:	Cold Freshwater Habitat
Number of Samples:	12
Number of Exceedances:	0
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 12 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
Water Quality Objective/Criterion:	The California Toxics Rule (CTR) freshwater aquatic life standard for silver is dependent on hardness. At the hardness levels reported for this station, the standard, as an instantaneous maximum, ranges from 0.15 to 2.46 ug/L.
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:	One station, "Mammoth Creek at Twin Lakes" was sampled.
Temporal Representation:	Twelve samples were collected approximately quarterly e2001 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	8167
Pollutant:	Specific Conductance
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
Weight of Evidence:	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 exceed the water quality objective. Based on the readily available data and information, the weight of evidence indicates that there is sufficient justification against placing this water segment-pollutant combination on the section 303(d) list in the Water Quality Limited Segments category. This conclusion is based on the staff findings that: 1. The data used satisfy the data quality requirements of section 6.1.4 of the Policy. 2. The data used do not satisfy the data quantity requirements of section 6.1.5 of the Policy. 3. None of 12 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.
RWQCB Board Decision / Staff 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.
SWRCB Board Decision / Staff Recommendation:
USEPA Decision:

Lines of Evidence (LOEs) for Decision ID 8167

LOE ID:	6954
Pollutant:	Specific Conductance
LOE Subgroup:	Pollutant-Water
Matrix:	Water
Fraction:	None
Beneficial Use:	Municipal & Domestic Supply
Number of Samples:	16
Number of Exceedances:	0
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. Specific conductance in 16 quarterly field measurements ranged from 47 to 185 uS/cm. Specific conductance was also measured in the laboratory for five samples collected on field sampling dates between August 2001 and August 2002; the results ranged from 59 to 199 uS/cm. The MCL was not exceeded.
Data Reference:	2007. SWAMP Data for the Owens Hydrologic Unit
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:	2007. 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 field measurements of specific conductance were taken quarterly between August 2001 and July 2005. Five quarterly laboratory measurements were taken between August 2001 and August 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	8168
Pollutant:	Temperature, water
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
Weight of Evidence:	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 3 to 6 times per year, 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.
RWQCB Board Decision / Staff 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 the requirements of Listing Policy sections 3.10 and 6.1.5.9 are not met.
SWRCB Board Decision / Staff Recommendation:
USEPA Decision:

Lines of Evidence (LOEs) for Decision ID 8168

LOE ID:	6953
Pollutant:	Temperature, water
LOE Subgroup:	Pollutant-Water
Matrix:	Water
Fraction:	None
Beneficial Use:	Cold Freshwater Habitat
Number of Samples:	16
Number of Exceedances:	0
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. Water temperatures in 16 quarterly measurements ranged from 1 to 19 degrees Celsius.
Data Reference:	2007. SWAMP Data for the Owens Hydrologic Unit
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:	2007. 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 temperature measurements were taken 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	8237
Pollutant:	Thallium
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
Weight of Evidence:	This pollutant is being considered for placement on the section 303(d) list under section 3.1 of the Listing Policy. Under section 3.1 a single line of evidence is necessary to assess listing status. Two lines of evidence are available in the administrative record to assess this pollutant. None of the samples exceed the applicable water quality objective and criteria. 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. Twelve dissolved thallium samples and twelve total thallium samples were below detection levels. Under Section 6.1.5.5 of the Listig Policy, the standards are considered to be attained. 4. Pursuant to section 3.11 of the Listing Policy, no additional data and information are available indicating that standards are not met.
RWQCB Board Decision / Staff 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.
SWRCB Board Decision / Staff Recommendation:
USEPA Decision:

Lines of Evidence (LOEs) for Decision ID 8237

LOE ID:	7060
Pollutant:	Thallium
LOE Subgroup:	Pollutant-Water
Matrix:	Water
Fraction:	Total
Beneficial Use:	Municipal & Domestic Supply
Number of Samples:	12
Number of Exceedances:	0
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 12 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
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:	2007. 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:	Twelve 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):
LOE ID:	7061
Pollutant:	Thallium
LOE Subgroup:	Pollutant-Water
Matrix:	Water
Fraction:	Dissolved
Beneficial Use:	Cold Freshwater Habitat
Number of Samples:	12
Number of Exceedances:	0
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 thallium in 12 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
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:	Compilation of Water Quality Goals
Evaluation Guideline:
Guideline Reference:
Spatial Representation:	One station, "Mammoth Creek at Twin Lakes" was sampled.
Temporal Representation:	Twelve samples were collected 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	9466
Pollutant:	Total Dissolved Solids
Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	New Decision
Revision Status	Revised
Impairment from Pollutant or Pollution:	Pollutant
Weight of Evidence:	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 exceeds the California Maximum Contaminant Level. Five of five annual average datapoints (calculated from only 2 to 4 samples per year) exceed 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 full range of seasonal and annual variability in streamflows and constituent concentrations expected in streams of the Lahontan Region. 3. None of 16 samples exceeded the MCL and this does not exceed the allowable frequency listed in Table 3.2 of the Listing Policy. Five of five annual average datapoints exceeded the site-specific objective and this exceeds the alloable frequency listed in 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.
RWQCB Board Decision / Staff 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, although one of the applicable water quality standards is being exceeded, the data are not temporally representative.
SWRCB Board Decision / Staff Recommendation:
USEPA Decision:

Lines of Evidence (LOEs) for Decision ID 9466

LOE ID:	7140
Pollutant:	Total Dissolved Solids
LOE Subgroup:	Pollutant-Water
Matrix:	Water
Fraction:	Total Dissolved
Beneficial Use:	Municipal & Domestic Supply
Number of Samples:	16
Number of Exceedances:	0
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 TDS in 16 quarterly samples ranged from 22 to 138 mg/L. The MCL was not exceeded.
Data Reference:	2007. SWAMP Data for the Owens Hydrologic Unit
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:	2007. 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 (2 to 4 per year) 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.
QAPP Information:	The data meet the quality assurance requirements of the SWAMP QAPP.
QAPP Information Reference(s):
LOE ID:	7139
Pollutant:	Total Dissolved Solids
LOE Subgroup:	Pollutant-Water
Matrix:	Water
Fraction:	Total Dissolved
Beneficial Use:	Cold Freshwater Habitat
Number of Samples:	5
Number of Exceedances:	5
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 TDS in 16 quarterly samples ranged from 22 to 138 mg/L. Annual averages (calculated from 2 to 4 samples per year) ranged from 67 to 100 mg/L. The highest average was based on two samples. The annual average objective was exceeded in 5 out of 5 years.
Data Reference:	2007. SWAMP Data for the Owens Hydrologic Unit
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 Dissolved Solids (TDS) concentration of 60 mg/L and a 90th percentile value of 90 mg/L.
Objective/Criterion Reference:	2007. 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 (2 to 4 per year) 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	8268
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:	New Decision
Revision Status	Revised
Impairment from Pollutant or Pollution:	Pollutant
Weight of Evidence:	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 applicable numeric standards or criteria for Total Kjeldahl Nitrogen for this station, and there are no data on algae or macrophytes available to assess compliance with 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 chemical data used satisfy the data quality requirements of section 6.1.4 of the Policy. 2. The chemical data used do notsatisfy 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 were no data available on algae or macrophytes for assessment of compliance with the water quality objective. 4. Pursuant to section 3.11 of the Listing Policy, no additional data and information are available indicating that standards are not met.
RWQCB Board Decision / Staff 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 there is insufficient information availaable to determine whether the applicable water quality standards are being exceeded.
SWRCB Board Decision / Staff Recommendation:
USEPA Decision:

Lines of Evidence (LOEs) for Decision ID 8268

LOE ID:	7096
Pollutant:	Total Kjeldahl Nitrogen (TKN)
LOE Subgroup:	Pollutant-Water
Matrix:	Water
Fraction:	Total
Beneficial Use:	Cold Freshwater Habitat
Number of Samples:	16
Number of Exceedances:	0
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 16 quarterly sampleds ranged from 0.09 to 0.4 mg/L. No data on algae or macrophytes are available for assessment of compliance with the objective for biostimulatory substances.
Data Reference:	2007. SWAMP Data for the Owens Hydrologic Unit
Water Quality Objective/Criterion:	There are no site- specific numeric objectives in the Lahontan Basin Plan for Total Kjeldahl Nitrogen (TKN) for Mammoth Creek. (The numeric objective for Total Nitrogen is assessed separately.) The regionwide narrative objective for biostimulatory substances states: “Waters shall not contain biostimulatory substances in concentrations that promote aquatic growths to the extent that such growths cause nuisance or adversely affect the water for beneficial uses.”
Objective/Criterion Reference:	2007. 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 for TKN 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	9821
Pollutant:	Total Nitrogen as N
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
Weight of Evidence:	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. 3. None of five 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.
RWQCB Board Decision / Staff 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.
SWRCB Board Decision / Staff Recommendation:
USEPA Decision:

Lines of Evidence (LOEs) for Decision ID 9821

LOE ID:	7093
Pollutant:	Total Nitrogen as N
LOE Subgroup:	Pollutant-Water
Matrix:	Water
Fraction:	Total
Beneficial Use:	Cold Freshwater Habitat
Number of Samples:	5
Number of Exceedances:	0
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
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:	2007. 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	9820
Pollutant:	Turbidity
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
Weight of Evidence:	This pollutant is being considered for placement on the section 303(d) list under sections 3.2 and 3.10 of the Listing Policy. Under section 3.2 a single line of evidence is necessary to assess listing status. Four lines of evidence are available in the administrative record to assess this pollutant. Separate lines of evidence were prepared to assess data expressed as NTU and NTRU, since the two types of units reflect different optical properties and are not directly comparable. None of the twelve samples expressed as NTU exceed the California Maximum Contaminant Level (MCL) applicable under the water quality objective for Chemical Constituents. The MCL is expressed as NTU, and the four samples expressed as NTRU cannot be used to determine compliance with the MCL. The Lahontan Basin Plan's narrative objective for turbidity is antidegradation- based and allows no more than a 10 percent increase over natural turbidity levels. Listing Policy Section 3.10 provides direction for assessment of trends in water quality, including a requirement to document background conditions. Turbidity varies with streamflow and can change drastically over a single day depending on storm or snowmelt events. Continuous measurements of turbidity would be necessary to establish natural background conditions and detect trends of increased turbidity in violation of the objective. Quarterly samples are inadequate to determine complince with the narrative objective under Listing Policy Section 3.10. 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 turbidity in streams of the Lahontan Region. 3. None of twelve measurements expressed as NTU exceeded the MCL and this does not exceed the allowable frequency listed in Table 3.2 of the Listing Policy. 4. Sampling frequency was insufficient to define background conditions or detect changes (if changes occurred). Therefore there is insufficient information to assess compliance with the narrative turbidity objective under Listing Policy Section 3.10. 5. Pursuant to section 3.11 of the Listing Policy, no additional data and information are available indicating that standards are not met.
RWQCB Board Decision / Staff 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 one of the applicable water quality standards is not being exceeded and the data are insufficient to determine compliance with the other standard under Listing Policy section 3.10.
SWRCB Board Decision / Staff Recommendation:
USEPA Decision:

Lines of Evidence (LOEs) for Decision ID 9820

LOE ID:	9118
Pollutant:	Turbidity
LOE Subgroup:	Pollutant-Water
Matrix:	Water
Fraction:	None
Beneficial Use:	Municipal & Domestic Supply
Number of Samples:	4
Number of Exceedances:	0
Data and Information Type:	Fixed station physical/chemical (conventional plus toxic pollutants)
Data Used to Assess Water Quality:	The USGS sampled this station under the Region 6 SWAMP program. Four turbidity measurements expressed as NTRU were taken quarterly between 2004 and 2005. All of them were below the detection level.
Data Reference:	2007. SWAMP Data for the Owens Hydrologic Unit
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:	2007. 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:	Four quarterly turbidity measurements expressed as NTRU were taken between 2004 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):
LOE ID:	9116
Pollutant:	Turbidity
LOE Subgroup:	Pollutant-Water
Matrix:	Water
Fraction:	None
Beneficial Use:	Cold Freshwater Habitat
Number of Samples:	12
Number of Exceedances:	0
Data and Information Type:	Fixed station physical/chemical (conventional plus toxic pollutants)
Data Used to Assess Water Quality:	The USGS sampled this station under the Region 6 SWAMP program. Twelve turbidity measurements expressed as NTU were taken quarterly between 2001 and 2004. Two of them were below the detection level. The remainder ranged from 1.1 to 3.5 NTU.
Data Reference:	2007. SWAMP Data for the Owens Hydrologic Unit
Water Quality Objective/Criterion:	The Lahontan Basin Plan's regionwide water quality 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:	2007. 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:	Twelve quarterly turbidity measurements expressed as NTRU were taken between 2001 and 2004.
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):
LOE ID:	9117
Pollutant:	Turbidity
LOE Subgroup:	Pollutant-Water
Matrix:	Water
Fraction:	None
Beneficial Use:	Cold Freshwater Habitat
Number of Samples:	4
Number of Exceedances:	0
Data and Information Type:	Fixed station physical/chemical (conventional plus toxic pollutants)
Data Used to Assess Water Quality:	The USGS sampled this station under the Region 6 SWAMP program. Four turbidity measurements expressed as NTRU were taken quarterly between 2004 and 2005. All of them were below the detection level.
Data Reference:	2007. SWAMP Data for the Owens Hydrologic Unit
Water Quality Objective/Criterion:	The Lahontan Basin Plan's regionwide water quality 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:	2007. 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:	Four quarterly turbidity measurements expressed as NTRU were taken between 2004 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):
LOE ID:	7305
Pollutant:	Turbidity
LOE Subgroup:	Pollutant-Water
Matrix:	Water
Fraction:	None
Beneficial Use:	Municipal & Domestic Supply
Number of Samples:	12
Number of Exceedances:	0
Data and Information Type:	Fixed station physical/chemical (conventional plus toxic pollutants)
Data Used to Assess Water Quality:	The USGS sampled this station under the Region 6 SWAMP program. Twelve turbidity measurements expressed as NTU were taken quarterly between 2001 and 2004. Two of them were below the detection level. The remainde ranged from 1.1 to 3.5 NTU. The MCL was not exceeded.
Data Reference:	2007. SWAMP Data for the Owens Hydrologic Unit
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:	2007. 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:	Twelve uarterly turbidity measurements expressed as NTRU were taken between 2001 and 2004.
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	9467
Pollutant:	Vanadium
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
Weight of Evidence:	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 Calfornia Notification 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. There are no applicable standards or criteria for dissolved vanadium. None of 12 total vanadium samples exceeded the California Notification 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.
RWQCB Board Decision / Staff 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.
SWRCB Board Decision / Staff Recommendation:
USEPA Decision:

Lines of Evidence (LOEs) for Decision ID 9467

LOE ID:	7130
Pollutant:	Vanadium
LOE Subgroup:	Pollutant-Water
Matrix:	Water
Fraction:	Dissolved
Beneficial Use:	Cold Freshwater Habitat
Number of Samples:	12
Number of Exceedances:	0
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 4 of 12 samples were below the detection level. Vanadium concentrations in the remaining 8 samples ranged from 0.3 to 0.8 ug/L.
Data Reference:	2007. SWAMP Data for the Owens Hydrologic Unit
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:	National recommended water quality criteria: 2002. EPA-822-R-02-047 Washington, D.C. USEPA
Evaluation Guideline:
Guideline Reference:
Spatial Representation:	One station, "Mammoth Creek at Twin Lakes" was sampled.
Temporal Representation:	Twelve 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):
LOE ID:	7128
Pollutant:	Vanadium
LOE Subgroup:	Pollutant-Water
Matrix:	Water
Fraction:	Total
Beneficial Use:	Municipal & Domestic Supply
Number of Samples:	12
Number of Exceedances:	0
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 8 of 12 samples were below the detection level. The presence of vanadium in the remaining 4 samples was verified but not quantified. The criterion was not violated.
Data Reference:	2007. SWAMP Data for the Owens Hydrologic Unit
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 Twin Lakes" was sampled.
Temporal Representation:	Twelve 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	8221
Pollutant:	Zinc
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
Weight of Evidence:	This pollutant is being considered for placement on the section 303(d) list under section 3.1 of the Listing Policy. Under section 3.1 a single line of evidence is necessary to assess listing status. Two lines of evidence are available in the administrative record to assess this pollutant. None of the samples exceed the water quality objective. Based on the readily available data and information, the weight of evidence indicates that there is sufficient justification against placing this water segment-pollutant combination on the section 303(d) list in the Water Quality Limited Segments category. This conclusion is based on the staff findings that: 1. The data used satisfy the data quality requirements of section 6.1.4 of the Policy. 2. The data used do not satisfy the data quantity requirements of section 6.1.5 of the Policy. Quarterly samples do not capture the seasonal and annual variability expected in streamflows and constituent concentrations in streams of the Lahontan Region. 3. None of 12 dissolved zinc samples exceeded the California Toxics Rule standards. None of 12 total zinc samples exceeded the Califonia 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.
RWQCB Board Decision / Staff 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.
SWRCB Board Decision / Staff Recommendation:
USEPA Decision:

Lines of Evidence (LOEs) for Decision ID 8221

LOE ID:	7001
Pollutant:	Zinc
LOE Subgroup:	Pollutant-Water
Matrix:	Water
Fraction:	Dissolved
Beneficial Use:	Cold Freshwater Habitat
Number of Samples:	12
Number of Exceedances:	0
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 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
Water Quality Objective/Criterion:	The California Toxics Rule’s (CTR's ) freshwater aquatic life standards for zinc are dependent on hardness. At the hardness levels reported for this station, the acute (1 hour) toxicity standard ranges from 24.63 to 117.18 ug/L, and the chronic (4-day average) standard ranges from 24.83 to 118.14 ug/L.
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:	One station, "Mammoth Creek at Twin Lakes" was sampled.
Temporal Representation:	Twelve 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):
LOE ID:	6998
Pollutant:	Zinc
LOE Subgroup:	Pollutant-Water
Matrix:	Water
Fraction:	Total
Beneficial Use:	Municipal & Domestic Supply
Number of Samples:	12
Number of Exceedances:	0
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 12 samples for total recoverable zinc, 7 were below the detection level and one was an estimated value. Concentrations of total recoverable zinc in the remaining 4 samples ranged from 1 to 3 ug/L. The MCL was not violated.
Data Reference:	2007. SWAMP Data for the Owens Hydrologic Unit
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:	2007. 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:	Twelve 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	9822
Pollutant:	pH
Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	New Decision
Revision Status	Revised
Impairment from Pollutant or Pollution:	Pollutant
Weight of Evidence:	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. One line of evidence is available to support this decision. There are not enough pH samples to establish baseline conditions (including diel, seasonal, annual and interannual variations) or to detect changes in the pH regime due to controllable factors, if such trends exist.
RWQCB Board Decision / Staff 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 the data are insufficient to establish baseline and trend conditions as required under Listing Policy seciton 3.10
SWRCB Board Decision / Staff Recommendation:
USEPA Decision:

Lines of Evidence (LOEs) for Decision ID 9822

LOE ID:	7205
Pollutant:	pH
LOE Subgroup:	Pollutant-Water
Matrix:	Water
Fraction:	None
Beneficial Use:	Cold Freshwater Habitat
Number of Samples:	15
Number of Exceedances:	0
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 field pH measurements ranged from 6.6 to 8.8 units. Four additional laboratory samples ranged from 7.1 to 7.8 units.
Data Reference:	2007. SWAMP Data for the Owens Hydrologic Unit
Water Quality Objective/Criterion:	.The Lahontan Basin Plan's 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 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
	2007. 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:	Fifteen 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):