| Water Body Name: | East Walker River, above Bridgeport Reservoir |
| Water Body ID: | CAR6303005020011214105850 |
| Water Body Type: | River & Stream |
DECISION ID |
172161 |
Region 6 |
East Walker River, above Bridgeport Reservoir |
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| Pollutant: | Indicator Bacteria | ||||
| Final Listing Decision: | Do Not Delist from 303(d) list (being addressed with action other than TMDL) | ||||
| Last Listing Cycle's Final Listing Decision: | Do Not Delist from 303(d) list (being addressed with action other than TMDL)(2018) | ||||
| Revision Status | Revised | ||||
| Sources: | Agricultural Water Diversion | Agriculture-grazing | Grazing-Related Sources | Natural Sources | Pasture Grazing-Riparian and/or Upland | Streambank Modification/Destabilization | Unknown Nonpoint Source | ||||
| Expected Attainment Date: | 2028 | ||||
| Implementation Action Other than TMDL: | This listing is being addressed through the implementation of management practices for livestock grazing under the General Conditional Waiver of Waste Discharge Requirements for Grazing Operations in the East Walker River Watershed (Bridgeport Valley and Tributaries) of the Lahontan Region. | ||||
| Impairment from Pollutant or Pollution: | Pollutant | ||||
| Regional Board Conclusion: | This pollutant is being considered for removal on the CWA section 303(d) List under section 4.3 of the Listing Policy. Under 4.3 of the Policy, a minimum of one line of evidence is needed to assess listing status. Five lines of evidence are available in the administrative record to assess this pollutant. Fourteen of 40 E. coli samples exceeded the Single Threshold Value (STV) water quality objective and 9 of 11 samples exceeded the geometric mean water quality objective. (Fecal coliform lines of evidence used in previous indicator bacteria decisions in the Lahontan Region have been removed from decisions, starting in the 2026 Integrated Report, because the Lahontan Region's fecal coliform objective was removed from the Basin Plan in 2024). In 2017 the Lahontan Water Board approved Resolution R6T-2017-0033, General Conditional Waiver of Waste Discharge Requirements for Grazing Operations in the East Walker River Watershed (Bridgeport Valley and Tributaries) of the Lahontan Region. The Waiver was renewed in 2023 under Resolution R6T-2023-0006. This waiver is designed to improve water quality in the Bridgeport Valley, of which the East Walker River, above Bridgeport Reservoir is a waterbody. The waiver expects water quality to attain WQOs by 2028. Based on the readily available data and information, the weight of evidence indicates that there is sufficient justification against removing this water segment-pollutant combination from the CWA section 303(d) List. There is sufficient justification to place it in the Being Addressed portion of the CWA section 303(d) List because an existing regulatory program is reasonably expected to result in attainment of the standard within a reasonable, specified time frame. This conclusion is based on the staff findings that: 1. The data used satisfies the data quality requirements of section 6.1.4 of the Policy. 2. The data used satisfies the data quantity requirements of section 6.1.5 of the Policy. 3. Fourteen of 40 E. coli samples exceeded the Single Threshold Value (STV) water quality objective and 9 of 11 samples exceeded the geometric mean water quality objective and these exceed the allowable frequency listed in Table 4.2 of the Listing Policy. 4. Pursuant to section 3.11 of the Listing Policy, no additional data and information are available indicating that standards are met. 5. The General Conditional Waiver of Waste Discharge Requirements for Grazing Operations in the East Walker River Watershed (Bridgeport Valley and Tributaries) of the Lahontan Region expects water quality to attain WQOs by 2028. |
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| Regional Board Decision Recommendation: | After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be removed from the section 303(d) list because applicable water quality standards for the pollutant are being exceeded. | ||||
| State Board Review of Regional Board Conclusion and Recommendation: | |||||
| State Board Decision Recommendation: | After review of this Regional Board decision, SWRCB staff recommend the decision be approved by the State Board. | ||||
DECISION ID |
172161 |
Region 6 |
East Walker River, above Bridgeport Reservoir |
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| Pollutant: | Indicator Bacteria |
| Final Listing Decision: | Do Not Delist from 303(d) list (being addressed with action other than TMDL) |
| Last Listing Cycle's Final Listing Decision: | Do Not Delist from 303(d) list (being addressed with action other than TMDL)(2018) |
| Revision Status | Revised |
| Sources: | Agricultural Water Diversion | Agriculture-grazing | Grazing-Related Sources | Natural Sources | Pasture Grazing-Riparian and/or Upland | Streambank Modification/Destabilization | Unknown Nonpoint Source |
| Expected Attainment Date: | 2028 |
| Implementation Action Other than TMDL: | This listing is being addressed through the implementation of management practices for livestock grazing under the General Conditional Waiver of Waste Discharge Requirements for Grazing Operations in the East Walker River Watershed (Bridgeport Valley and Tributaries) of the Lahontan Region. |
| Impairment from Pollutant or Pollution: | Pollutant |
| Regional Board Conclusion: | This pollutant is being considered for removal on the CWA section 303(d) List under section 4.3 of the Listing Policy. Under 4.3 of the Policy, a minimum of one line of evidence is needed to assess listing status. Five lines of evidence are available in the administrative record to assess this pollutant. Fourteen of 40 E. coli samples exceeded the Single Threshold Value (STV) water quality objective and 9 of 11 samples exceeded the geometric mean water quality objective. (Fecal coliform lines of evidence used in previous indicator bacteria decisions in the Lahontan Region have been removed from decisions, starting in the 2026 Integrated Report, because the Lahontan Region's fecal coliform objective was removed from the Basin Plan in 2024). In 2017 the Lahontan Water Board approved Resolution R6T-2017-0033, General Conditional Waiver of Waste Discharge Requirements for Grazing Operations in the East Walker River Watershed (Bridgeport Valley and Tributaries) of the Lahontan Region. The Waiver was renewed in 2023 under Resolution R6T-2023-0006. This waiver is designed to improve water quality in the Bridgeport Valley, of which the East Walker River, above Bridgeport Reservoir is a waterbody. The waiver expects water quality to attain WQOs by 2028. Based on the readily available data and information, the weight of evidence indicates that there is sufficient justification against removing this water segment-pollutant combination from the CWA section 303(d) List. There is sufficient justification to place it in the Being Addressed portion of the CWA section 303(d) List because an existing regulatory program is reasonably expected to result in attainment of the standard within a reasonable, specified time frame. This conclusion is based on the staff findings that: 1. The data used satisfies the data quality requirements of section 6.1.4 of the Policy. 2. The data used satisfies the data quantity requirements of section 6.1.5 of the Policy. 3. Fourteen of 40 E. coli samples exceeded the Single Threshold Value (STV) water quality objective and 9 of 11 samples exceeded the geometric mean water quality objective and these exceed the allowable frequency listed in Table 4.2 of the Listing Policy. 4. Pursuant to section 3.11 of the Listing Policy, no additional data and information are available indicating that standards are met. 5. The General Conditional Waiver of Waste Discharge Requirements for Grazing Operations in the East Walker River Watershed (Bridgeport Valley and Tributaries) of the Lahontan Region expects water quality to attain WQOs by 2028. |
| Regional Board Decision Recommendation: | After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be removed from the section 303(d) list because applicable water quality standards for the pollutant are being exceeded. |
| State Board Review of Regional Board Conclusion and Recommendation: | |
| State Board Decision Recommendation: | After review of this Regional Board decision, SWRCB staff recommend the decision be approved by the State Board. |
| Listing Extent: | |
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| LOE ID: | 99920 | ||||
| Listing Extent: | |||||
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| LOE ID: | 99920 | ||||
| Pollutant: | Escherichia coli (E. coli) | ||||
| LOE Subgroup: | Pollutant-Water | ||||
| Matrix: | Water | ||||
| Fraction: | None | ||||
| Beneficial Use: | Water Contact Recreation | ||||
| Number of Samples: | 13 | ||||
| Number of Exceedances: | 4 | ||||
| Data and Information Type: | PATHOGEN MONITORING | ||||
| Data Used to Assess Water Quality: | Water Board staff assessed RWB6_BACT_Monitoring data for East Walker River, above Bridgeport Reservoir to determine beneficial use support and the results are as follows: 4 of the 13 samples exceeded the Statistical Threshold Value (STV) water quality standard for E. coli. The STV is based on a 10% exceedance rate that is calculated monthly. | ||||
| Data Reference: | Water Quality Assessment Data for the 2018 solicitation cycle submitted through CEDEN for Regional Water Board 6 Bacteria Monitoring. | ||||
| SWAMP Data: | SWAMP | ||||
| Water Quality Objective/Criterion: | The bacteria water quality objective applicable to all waters, except Lake Tahoe, where the salinity is less than 10 parts per thousand (ppth) 95 percent or more of the time is a STATISTICAL THRESHOLD VALUE (STV) of 320 cfu/100 mL not to be exceeded more than 10 percent of the time (calculated monthly). | ||||
| Objective/Criterion Reference: | Inland Surface Waters, Enclosed Bays, and Estuaries Plan. Part 1: Trash Provisions; Part 2: Tribal Subsistence Beneficial Uses and Mercury Provisions; Part 3: Bacteria Provisions and Variance Policy | ||||
| Evaluation Guideline: | |||||
| Guideline Reference: | |||||
| Spatial Representation: | The samples were collected at 1 monitoring site(s), station(s): 630EWK006 | ||||
| Temporal Representation: | The samples were collected between the days of 2014-05-13 and 2015-10-15 . | ||||
| Environmental Conditions: | |||||
| QAPP Information: | Quality Assurance Program Plan and Standard Operating Procedures for SWAMP program | ||||
| QAPP Information Reference(s): | Quality Assurance Program Plans, Quality Assurance Project Plans, and Standard Operating Procedures for the SWAMP program | ||||
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| LOE ID: | 99878 | ||||
| Pollutant: | Escherichia coli (E. coli) | ||||
| LOE Subgroup: | Pollutant-Water | ||||
| Matrix: | Water | ||||
| Fraction: | None | ||||
| Beneficial Use: | Water Contact Recreation | ||||
| Number of Samples: | 7 | ||||
| Number of Exceedances: | 1 | ||||
| Data and Information Type: | PATHOGEN MONITORING | ||||
| Data Used to Assess Water Quality: | Pollutant: | Escherichia coli (E. coli) | |||
| LOE Subgroup: | Pollutant-Water | ||||
| Matrix: | Water | ||||
| Fraction: | None | ||||
| Beneficial Use: | Water Contact Recreation | ||||
| Number of Samples: | 13 | ||||
| Number of Exceedances: | 4 | ||||
| Data and Information Type: | PATHOGEN MONITORING | ||||
| Data Used to Assess Water Quality: | Water Board staff assessed RWB6_BACT_Monitoring data for East Walker River, above Bridgeport Reservoir to determine beneficial use support and the results are as follows: 4 of the 13 samples exceeded the Statistical Threshold Value (STV) water quality standard for E. coli. The STV is based on a 10% exceedance rate that is calculated monthly. | ||||
| Data Reference: | Water Quality Assessment Data for the 2018 solicitation cycle submitted through CEDEN for Regional Water Board 6 Bacteria Monitoring. | ||||
| SWAMP Data: | SWAMP | ||||
| Water Quality Objective/Criterion: | The bacteria water quality objective applicable to all waters, except Lake Tahoe, where the salinity is less than 10 parts per thousand (ppth) 95 percent or more of the time is a STATISTICAL THRESHOLD VALUE (STV) of 320 cfu/100 mL not to be exceeded more than 10 percent of the time (calculated monthly). | ||||
| Objective/Criterion Reference: | Inland Surface Waters, Enclosed Bays, and Estuaries Plan. Part 1: Trash Provisions; Part 2: Tribal Subsistence Beneficial Uses and Mercury Provisions; Part 3: Bacteria Provisions and Variance Policy | ||||
| Evaluation Guideline: | |||||
| Guideline Reference: | |||||
| Spatial Representation: | The samples were collected at 1 monitoring site(s), station(s): 630EWK006 | ||||
| Temporal Representation: | The samples were collected between the days of 2014-05-13 and 2015-10-15 . | ||||
| Environmental Conditions: | |||||
| QAPP Information: | Quality Assurance Program Plan and Standard Operating Procedures for SWAMP program | ||||
| QAPP Information Reference(s): | Quality Assurance Program Plans, Quality Assurance Project Plans, and Standard Operating Procedures for the SWAMP program | ||||
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| LOE ID: | 99878 | ||||
| Pollutant: | Escherichia coli (E. coli) | ||||
| LOE Subgroup: | Pollutant-Water | ||||
| Matrix: | Water | ||||
| Fraction: | None | ||||
| Beneficial Use: | Water Contact Recreation | ||||
| Number of Samples: | 7 | ||||
| Number of Exceedances: | 1 | ||||
| Data and Information Type: | PATHOGEN MONITORING | ||||
| Data Used to Assess Water Quality: | Water Board staff assessed Eastern Sierra Ambient Monitoring data for East Walker River, above Bridgeport Reservoir to determine beneficial use support and the results are as follows: 1 of the 7 samples exceeded the Statistical Threshold Value (STV) water quality standard for E. coli. The STV is based on a 10% exceedance rate that is calculated monthly. | ||||
| Data Reference: | Water Quality Assessment Data for the 2018 solicitation cycle submitted through CEDEN for Eastern Sierra Ambient Monitoring. | ||||
| SWAMP Data: | Non-SWAMP | ||||
| Water Quality Objective/Criterion: | The bacteria water quality objective applicable to all waters, except Lake Tahoe, where the salinity is less than 10 parts per thousand (ppth) 95 percent or more of the time is a STATISTICAL THRESHOLD VALUE (STV) of 320 cfu/100 mL not to be exceeded more than 10 percent of the time (calculated monthly). | ||||
| Data Reference: | Water Quality Assessment Data for the 2018 solicitation cycle submitted through CEDEN for Eastern Sierra Ambient Monitoring. | ||||
| SWAMP Data: | Non-SWAMP | ||||
| Water Quality Objective/Criterion: | The bacteria water quality objective applicable to all waters, except Lake Tahoe, where the salinity is less than 10 parts per thousand (ppth) 95 percent or more of the time is a STATISTICAL THRESHOLD VALUE (STV) of 320 cfu/100 mL not to be exceeded more than 10 percent of the time (calculated monthly). | ||||
| Objective/Criterion Reference: | Inland Surface Waters, Enclosed Bays, and Estuaries Plan. Part 1: Trash Provisions; Part 2: Tribal Subsistence Beneficial Uses and Mercury Provisions; Part 3: Bacteria Provisions and Variance Policy | ||||
| Evaluation Guideline: | |||||
| Guideline Reference: | |||||
| Spatial Representation: | The samples were collected at 1 monitoring site(s), station(s): 630EWK006 | ||||
| Temporal Representation: | The samples were collected between the days of 2012-08-14 and 2013-10-16 . | ||||
| Environmental Conditions: | |||||
| QAPP Information: | Quality Assurance Project Plan Sierra Nevada Aquatic Research Laboratory Center for Eastern Sierra Aquatic Microbial Ecology | ||||
| QAPP Information Reference(s): | Quality Assurance Project Plan Sierra Nevada Aquatic Research Laboratory Center for Eastern Sierra Aquatic Microbial Ecology (SNARL - CESAME) | ||||
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| LOE ID: | 99858 | ||||
| Pollutant: | Escherichia coli (E. coli) | ||||
| LOE Subgroup: | Pollutant-Water | ||||
| Matrix: | Water | ||||
| Fraction: | None | ||||
| Beneficial Use: | Water Contact Recreation | ||||
| Number of Samples: | 11 | ||||
| Number of Exceedances: | 4 | ||||
| Data and Information Type: | PATHOGEN MONITORING | ||||
| Data Used to Assess Water Quality: | Water Board staff assessed SWAMP RWB6 Monitoring data for East Walker River, above Bridgeport Reservoir to determine beneficial use support and the results are as follows: 4 of the 11 samples exceeded the Statistical Threshold Value (STV) water quality standard for E. coli. The STV is based on a 10% exceedance rate that is calculated monthly. | ||||
| Data Reference: | Water Quality Assessment Data for the 2018 solicitation cycle submitted through CEDEN for the SWAMP RWB6 Monitoring (tissue and water). | ||||
| SWAMP Data: | SWAMP | ||||
| Water Quality Objective/Criterion: | The bacteria water quality objective applicable to all waters, except Lake Tahoe, where the salinity is less than 10 parts per thousand (ppth) 95 percent or more of the time is a STATISTICAL THRESHOLD VALUE (STV) of 320 cfu/100 mL not to be exceeded more than 10 percent of the time (calculated monthly). | ||||
| Objective/Criterion Reference: | Inland Surface Waters, Enclosed Bays, and Estuaries Plan. Part 1: Trash Provisions; Part 2: Tribal Subsistence Beneficial Uses and Mercury Provisions; Part 3: Bacteria Provisions and Variance Policy | ||||
| Evaluation Guideline: | |||||
| Guideline Reference: | |||||
| Spatial Representation: | The samples were collected at 1 monitoring site(s), station(s): 630EWK006 | ||||
| Temporal Representation: | The samples were collected between the days of 2011-06-13 and 2013-08-27 . | ||||
| Environmental Conditions: | |||||
| QAPP Information: | Quality Assurance Program Plan and Standard Operating Procedures for SWAMP program | ||||
| QAPP Information Reference(s): | Quality Assurance Program Plans, Quality Assurance Project Plans, and Standard Operating Procedures for the SWAMP program | ||||
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| LOE ID: | 99841 | ||||
| Pollutant: | Escherichia coli (E. coli) | ||||
| LOE Subgroup: | Pollutant-Water | ||||
| Matrix: | Water | ||||
| Fraction: | None | ||||
| Beneficial Use: | Water Contact Recreation | ||||
| Number of Samples: | 11 | ||||
| Number of Exceedances: | 9 | ||||
| Data and Information Type: | PATHOGEN MONITORING | ||||
| Data Used to Assess Water Quality: | Water Board staff assessed SWAMP RWB6 Monitoring data for East Walker River, above Bridgeport Reservoir to determine beneficial use support and the results are as follows: 9 of the 11 samples exceeded the geomean water quality standard for E. coli. This is a six week rolling geomean that is calculated weekly. | ||||
| Data Reference: | Water Quality Assessment Data for the 2018 solicitation cycle submitted through CEDEN for the SWAMP RWB6 Monitoring (tissue and water). | ||||
| SWAMP Data: | SWAMP | ||||
| Water Quality Objective/Criterion: | The bacteria water quality objective applicable to all waters, except Lake Tahoe, where the salinity is less than 10 parts per thousand (ppth) 95 percent or more of the time is a six-week rolling GEOMETRIC MEAN (GM) of Escherichia coli (E. coli) not to exceed 100 colony forming units per 100 milliliters (cfu/100 mL) (calculated weekly). | ||||
| Objective/Criterion Reference: | Inland Surface Waters, Enclosed Bays, and Estuaries Plan. Part 1: Trash Provisions; Part 2: Tribal Subsistence Beneficial Uses and Mercury Provisions; Part 3: Bacteria Provisions and Variance Policy | ||||
| Evaluation Guideline: | |||||
| Guideline Reference: | |||||
| Spatial Representation: | The samples were collected at 1 monitoring site(s), station(s): 630EWK006 | ||||
| Temporal Representation: | The samples were collected between the days of 2011-06-13 and 2013-08-27 . | ||||
| Environmental Conditions: | |||||
| QAPP Information: | Quality Assurance Program Plan and Standard Operating Procedures for SWAMP program | ||||
| QAPP Information Reference(s): | Quality Assurance Program Plans, Quality Assurance Project Plans, and Standard Operating Procedures for the SWAMP program | ||||
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| LOE ID: | 133986 | ||||
| Pollutant: | Escherichia coli (E. coli) | ||||
| LOE Subgroup: | Pollutant-Water | ||||
| Matrix: | Water | ||||
| Fraction: | None | ||||
| Beneficial Use: | Water Contact Recreation | ||||
| Number of Samples: | 9 | ||||
| Number of Exceedances: | 5 | ||||
| Data and Information Type: | PATHOGEN MONITORING | ||||
| Data Used to Assess Water Quality: | Water Board staff assessed RWB6_BACT_Monitoring data for Bridgeport Reservoir to determine beneficial use support and the results are as follows: 5 of the 9 samples exceeded the Statistical Threshold Value (STV) water quality standard for E. coli. The STV is based on a 10% exceedance rate that is calculated monthly. | ||||
| Data Reference: | Water Quality Assessment Data for the 2018 solicitation cycle submitted through CEDEN for Regional Water Board 6 Bacteria Monitoring. | ||||
| SWAMP Data: | SWAMP | ||||
| Water Quality Objective/Criterion: | The bacteria water quality objective applicable to all waters, except Lake Tahoe, where the salinity is less than 10 parts per thousand (ppth) 95 percent or more of the time is a STATISTICAL THRESHOLD VALUE (STV) of 320 cfu/100 mL not to be exceeded more than 10 percent of the time (calculated monthly). | ||||
| Objective/Criterion Reference: | Inland Surface Waters, Enclosed Bays, and Estuaries Plan. Part 1: Trash Provisions; Part 2: Tribal Subsistence Beneficial Uses and Mercury Provisions; Part 3: Bacteria Provisions and Variance Policy | ||||
| Evaluation Guideline: | |||||
| Guideline Reference: | |||||
| Spatial Representation: | The samples were collected at 1 monitoring site(s), station(s): EWK.08 | ||||
| Temporal Representation: | The samples were collected between the days of 2014-06-03 and 2015-10-14 . | ||||
| Environmental Conditions: | |||||
| QAPP Information: | Quality Assurance Program Plan and Standard Operating Procedures for SWAMP program | ||||
| QAPP Information Reference(s): | Quality Assurance Program Plans, Quality Assurance Project Plans, and Standard Operating Procedures for the SWAMP program | ||||
Line of Evidence (LOE) for Decision ID 172161, Indicator Bacteria
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Region 6 |
East Walker River, above Bridgeport Reservoir |
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Line of Evidence (LOE) for Decision ID 172161, Indicator Bacteria
|
Region 6 |
East Walker River, above Bridgeport Reservoir |
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Line of Evidence (LOE) for Decision ID 172161, Indicator Bacteria
|
Region 6 |
East Walker River, above Bridgeport Reservoir |
|