Final California 2026 Integrated Report (303(d) List/305(b) Report)
Supporting Information
Regional Board 2 - San Francisco Bay Region
Water Body Name:
Almaden Reservoir
Water Body ID:
CAL2054003020000304125701
Water Body Type:
Lake & Reservoir
DECISION ID
145408
Region 2
Almaden Reservoir
Pollutant:
Mercury
Final Listing Decision:
Do Not Delist from 303(d) list (being addressed with USEPA approved TMDL)
Last Listing Cycle's Final Listing Decision:
List on 303(d) list (being addressed by USEPA approved TMDL)(2018)
Revision Status
Revised
Sources:
Inactive Mining | Mine Tailings
TMDL Name:
Guadalupe River Watershed Mercury
TMDL Project Code:
11
Date TMDL Approved by USEPA:
06/01/2010
Impairment from Pollutant or Pollution:
Pollutant
Regional Board Conclusion:
This pollutant is being considered for removal on the CWA section 303(d) List under sections 2.2 and SECTION 4.1 of the Listing Policy. Under SECTION 4.1 of the Policy, a minimum of one line of evidence is needed to assess listing status.
Three lines of evidence are available in the administrative record to assess this pollutant.
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 303(d) List because a TMDL has been completed and approved by RWQCB and USEPA, and is expected to result in attainment of the standard.
This conclusion is based on the staff findings that: 1. The data used satisfies the data quality requirements of section 6.1.4 of the Policy. 2. The data used satisfies the data quantity requirements of section 6.1.5 of the Policy. 3. Twenty of the twenty samples exceeded the mercury in fish tissue objective and these exceed the allowable frequency listed in Table 4.1 of the Listing Policy. 4. The Guadalupe River Watershed mercury TMDL was approved by USEPA on 6/1/2010. 5. Pursuant to section 4.11 of the Listing Policy, no additional data and information are available indicating that standards are not met.
Regional Board Decision Recommendation:
After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be removed from the section 303(d) list because applicable water quality standards for the pollutant are being exceeded.
State Board Review of Regional Board Conclusion and Recommendation:
State Board Decision Recommendation:
After review of this Regional Board decision, SWRCB staff recommend the decision be approved by the State Board.
Listing Extent:
Line of Evidence (LOE) for Decision ID 145408, Mercury
Region 2
Almaden Reservoir
LOE ID:
307410
Pollutant:
Mercury
LOE Subgroup:
Pollutant-Tissue
Final California 2026 Integrated Report (303(d) List/305(b) Report)
Supporting Information
Regional Board 2 - San Francisco Bay Region
Water Body Name:
Almaden Reservoir
Water Body ID:
CAL2054003020000304125701
Water Body Type:
Lake & Reservoir
DECISION ID
145408
Region 2
Almaden Reservoir
Pollutant:
Mercury
Final Listing Decision:
Do Not Delist from 303(d) list (being addressed with USEPA approved TMDL)
Last Listing Cycle's Final Listing Decision:
List on 303(d) list (being addressed by USEPA approved TMDL)(2018)
Revision Status
Revised
Sources:
Inactive Mining | Mine Tailings
TMDL Name:
Guadalupe River Watershed Mercury
TMDL Project Code:
11
Date TMDL Approved by USEPA:
06/01/2010
Impairment from Pollutant or Pollution:
Pollutant
Regional Board Conclusion:
This pollutant is being considered for removal on the CWA section 303(d) List under sections 2.2 and SECTION 4.1 of the Listing Policy. Under SECTION 4.1 of the Policy, a minimum of one line of evidence is needed to assess listing status.
Three lines of evidence are available in the administrative record to assess this pollutant.
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 303(d) List because a TMDL has been completed and approved by RWQCB and USEPA, and is expected to result in attainment of the standard.
This conclusion is based on the staff findings that: 1. The data used satisfies the data quality requirements of section 6.1.4 of the Policy. 2. The data used satisfies the data quantity requirements of section 6.1.5 of the Policy. 3. Twenty of the twenty samples exceeded the mercury in fish tissue objective and these exceed the allowable frequency listed in Table 4.1 of the Listing Policy. 4. The Guadalupe River Watershed mercury TMDL was approved by USEPA on 6/1/2010. 5. Pursuant to section 4.11 of the Listing Policy, no additional data and information are available indicating that standards are not met.
Regional Board Decision Recommendation:
After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be removed from the section 303(d) list because applicable water quality standards for the pollutant are being exceeded.
State Board Review of Regional Board Conclusion and Recommendation:
State Board Decision Recommendation:
After review of this Regional Board decision, SWRCB staff recommend the decision be approved by the State Board.
Listing Extent:
Line of Evidence (LOE) for Decision ID 145408, Mercury
Region 2
Almaden Reservoir
LOE ID:
307410
Pollutant:
Mercury
LOE Subgroup:
Pollutant-Tissue
Matrix:
Tissue
Fraction:
Fish whole body
Beneficial Use:
Wildlife Habitat
Number of Samples:
1
Number of Exceedances:
1
Data and Information Type:
Fish tissue analysis
Data Used to Assess Water Quality:
Water Board staff assessed SWAMP RMP data for Almaden Reservoir to determine beneficial use support and results are as follows: 1 of 1 samples for trophic level 3 fish in the 15-35 cm size range exceed the Basin Plan's mercury fish tissue objective of 0.1 mg/kg to protect wildlife.
Water Quality Control Plan, San Francisco Bay Basin, Table 3-4A Water Quality Objectives for Mercury in Waters of the Guadalupe River Watershed states, for the protection of aquatic organisms and wildlife: the water quality objective for is 0.1 mg methylmercury/kg fish in the average wet weight concentration measured in whole trophic level 3 fish with lengths 15-35 cm.
Line of Evidence (LOE) for Decision ID 145408, Mercury
Region 2
Almaden Reservoir
LOE ID:
307409
Pollutant:
Mercury
LOE Subgroup:
Pollutant-Tissue
Matrix:
Tissue
Fraction:
Fish whole body
Beneficial Use:
Wildlife Habitat
Number of Samples:
1
Number of Exceedances:
1
Data and Information Type:
Fish tissue analysis
Data Used to Assess Water Quality:
Water Board staff assessed SWAMP RMP data for Almaden Reservoir to determine beneficial use support and results are as follows: 1 of 1 samples for trophic level 3 fish in the 5-15 cm size range exceed the Basin Plan's mercury fish tissue objective of 0.05 mg/kg to protect wildlife.
Water Quality Control Plan, San Francisco Bay Basin, Table 3-4A Water Quality Objectives for Mercury in Waters of the Guadalupe River Watershed states, for the protection of aquatic organisms and wildlife: the water quality objective for is 0.05 mg methylmercury/kg fish in the average wet weight concentration measured in whole trophic level 3 fish with lengths 5-15 cm.
Line of Evidence (LOE) for Decision ID 145408, Mercury
Region 2
Almaden Reservoir
LOE ID:
5739
Pollutant:
Mercury (tissue)
LOE Subgroup:
Pollutant-Tissue
Matrix:
Tissue
Fraction:
None
Beneficial Use:
Commercial or recreational collection of fish, shellfish, or organisms
Number of Samples:
20
Number of Exceedances:
20
Data and Information Type:
Fish tissue analysis
Data Used to Assess Water Quality:
The 20 fish tissue samples were collected in 2004 to support development of the Guadalupe River watershed mercury TMDL. The fish were all largemouth bass ranging in lengths from 330 to 500 mm and weighing between 520 and 2080 grams. The mercury concentrations ranged from 2.16 to 7.35 mg/kg. All 20 fish tissue samples exceeded the criterion.
The Basin Plan contains the following objective: Many pollutants can accumulate on particles, in sediment, or bioaccumulate in fish and other aquatic organisms. Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
In 2001, U.S. EPA adopted a fish tissue methylmercury criterion of 0.3 mg/kg (in whole fish) for the protection of human health.
These fish were caught throughout the reservoir, and fish of this size integrate spatially because they consume prey from a wide spatial range.
Temporal Representation:
Fish tissue data were collected for this waterbody in late summer 2004. These adult fish integrate mercury concentrations over several years.
Environmental Conditions:
QAPP Information:
There is a well-developed QA plan for these data Tetra Tech, Inc. (Tetra Tech) 2003. Technical Memorandum 7.4.2, Quality Assurance Plan, Prepared for Santa Clara Valley Water District. June 13.
Water Board staff assessed SWAMP RMP data for Almaden Reservoir to determine beneficial use support and results are as follows: 1 of 1 samples for trophic level 3 fish in the 15-35 cm size range exceed the Basin Plan's mercury fish tissue objective of 0.1 mg/kg to protect wildlife.
Water Quality Control Plan, San Francisco Bay Basin, Table 3-4A Water Quality Objectives for Mercury in Waters of the Guadalupe River Watershed states, for the protection of aquatic organisms and wildlife: the water quality objective for is 0.1 mg methylmercury/kg fish in the average wet weight concentration measured in whole trophic level 3 fish with lengths 15-35 cm.
Line of Evidence (LOE) for Decision ID 145408, Mercury
Region 2
Almaden Reservoir
LOE ID:
307409
Pollutant:
Mercury
LOE Subgroup:
Pollutant-Tissue
Matrix:
Tissue
Fraction:
Fish whole body
Beneficial Use:
Wildlife Habitat
Number of Samples:
1
Number of Exceedances:
1
Data and Information Type:
Fish tissue analysis
Data Used to Assess Water Quality:
Water Board staff assessed SWAMP RMP data for Almaden Reservoir to determine beneficial use support and results are as follows: 1 of 1 samples for trophic level 3 fish in the 5-15 cm size range exceed the Basin Plan's mercury fish tissue objective of 0.05 mg/kg to protect wildlife.
Water Quality Control Plan, San Francisco Bay Basin, Table 3-4A Water Quality Objectives for Mercury in Waters of the Guadalupe River Watershed states, for the protection of aquatic organisms and wildlife: the water quality objective for is 0.05 mg methylmercury/kg fish in the average wet weight concentration measured in whole trophic level 3 fish with lengths 5-15 cm.
Line of Evidence (LOE) for Decision ID 145408, Mercury
Region 2
Almaden Reservoir
LOE ID:
5739
Pollutant:
Mercury (tissue)
LOE Subgroup:
Pollutant-Tissue
Matrix:
Tissue
Fraction:
None
Beneficial Use:
Commercial or recreational collection of fish, shellfish, or organisms
Number of Samples:
20
Number of Exceedances:
20
Data and Information Type:
Fish tissue analysis
Data Used to Assess Water Quality:
The 20 fish tissue samples were collected in 2004 to support development of the Guadalupe River watershed mercury TMDL. The fish were all largemouth bass ranging in lengths from 330 to 500 mm and weighing between 520 and 2080 grams. The mercury concentrations ranged from 2.16 to 7.35 mg/kg. All 20 fish tissue samples exceeded the criterion.
The Basin Plan contains the following objective: Many pollutants can accumulate on particles, in sediment, or bioaccumulate in fish and other aquatic organisms. Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.
In 2001, U.S. EPA adopted a fish tissue methylmercury criterion of 0.3 mg/kg (in whole fish) for the protection of human health.
These fish were caught throughout the reservoir, and fish of this size integrate spatially because they consume prey from a wide spatial range.
Temporal Representation:
Fish tissue data were collected for this waterbody in late summer 2004. These adult fish integrate mercury concentrations over several years.
Environmental Conditions:
QAPP Information:
There is a well-developed QA plan for these data Tetra Tech, Inc. (Tetra Tech) 2003. Technical Memorandum 7.4.2, Quality Assurance Plan, Prepared for Santa Clara Valley Water District. June 13.