| Water Body Name: | Oxbow Reservoir (Ralston Afterbay, El Dorado and Placer Counties) |
| Water Body ID: | CAL5144101020080922153913 |
| Water Body Type: | Lake & Reservoir |
DECISION ID |
12408 |
Region 5 |
Oxbow Reservoir (Ralston Afterbay, El Dorado and Placer Counties) |
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| Pollutant: | Mercury |
| Final Listing Decision: | List on 303(d) list (TMDL required list) |
| Last Listing Cycle's Final Listing Decision: | New Decision |
| Revision Status | Revised |
| Sources: | Resource Extraction |
| Expected TMDL Completion Date: | 2021 |
| Impairment from Pollutant or Pollution: | Pollutant |
| Regional Board Conclusion: | This pollutant is being considered for placement on the section 303(d) list under section 3.1 of the Listing Policy. Under section 3.1 a single line of evidence is necessary to assess listing status.
One lines of evidence are 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 in favor of placing this water segment-pollutant combination on the section 303(d) list in the Water Quality Limited Segments category. This conclusion is based on the staff findings that: 1. The data used satisfies the data quality requirements of section 6.1.4 of the Policy. 2. The data used satisfies the data quantity requirements of section 6.1.5 of the Policy. 3. Two of 10 samples exceed the USEPA fish tissue criterion for human health and this exceeds the allowable frequency listed in Table 3.1 of the Listing Policy. 4. Pursuant to section 3.11 of the Listing Policy, no additional data and information are available indicating that standards are not met. |
| Regional Board Decision Recommendation: | After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should be placed on the section 303(d) list because applicable water quality standards are exceeded and a pollutant contributes to or causes the problem. |
| State Board Review of Regional Board Conclusion and Recommendation: | |
| State Board Decision Recommendation: | After review of this Regional Board decision, SWRCB staff recommend the decision be approved by the State Board. |
| USEPA Action (if applicable): | USEPA approved the listing of this water body as a water quality limited segment requiring a TMDL for this pollutant. |
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| LOE ID: | 22578 | ||||
| Pollutant: | Methylmercury | ||||
| LOE Subgroup: | Pollutant-Tissue | ||||
| Matrix: | Tissue | ||||
| Fraction: | Total | ||||
| Beneficial Use: | Commercial or recreational collection of fish, shellfish, or organisms | ||||
| Number of Samples: | 10 | ||||
| Number of Exceedances: | 2 | ||||
| Data and Information Type: | PHYSICAL/CHEMICAL MONITORING | ||||
| Data Used to Assess Water Quality: | Fish were sampled for tissue analysis at one location from Oxbow Reservoir. A total of 2 out of 10 samples exceeded the USEPA fish tissue criterion for human health. The average wet weight methylmercury concentration in fish tissue was 0.15 ppm for all 10 samples collected. The number of fish collected per sample, the measured mercury concentrations in fish tissue, and the number of exceedances are, by species: Brown Trout- 4 samples, 0.06-0.11 ppm (average 0.09 ppm), no exceedances; Rainbow Trout- 1 sample, 0.04 ppm, no exceedances; Sacramento Pikeminnow- 5 samples, 0.11-0.35 ppm (average 0.22 ppm), 2 exceedances. All 10 samples were collected from fish with total lengths greater than 150 mm, which represent fish most commonly caught and consumed by sport fishers and their families. | ||||
| Data Reference: | Middle Fork American River Project AQ11 Water Quality Technical Study Report, 2007 (FERC No. 2079). Placer County Water Agency. June 2008 | ||||
| SWAMP Data: | Non-SWAMP | ||||
| Water Quality Objective/Criterion: | All waters shall be maintained free of toxic substances in concentrations that produce detrimental physiological responses in human, plant, animal, or aquatic life. The objective applies regardless of whether the toxicity is caused by a single substance or the interactive effect of multiple substances. | ||||
| Objective/Criterion Reference: | Water Quality Control Plan for the California Regional Water Quality Control Board Central Valley Region, Sacramento and San Joaquin River Basins. 4th ed | ||||
| Evaluation Guideline: | The USEPA Fish Tissue Residue Criterion for methylmercury in fish is 0.3 mg/kg (0.3 ppm) for the protection of human health. This is the concentration in fish tissue that should not be exceeded based on a total fish and shellfish consumption-weighted rate of 0.0175 kg fish/day. (USEPA, 2001) | ||||
| Guideline Reference: | Water Quality Criterion for the Protection of Human Health: Methylmercury. Final. United States Environmental Protection Agency Office of Science and Technology Office of Water. EPA-823-R-01-001. January 2001 | ||||
| Spatial Representation: | Samples were collected at one location from Oxbow Reservoir. Site locations were not provided in the report. | ||||
| Temporal Representation: | Fish samples were collected during one sampling event on 9/14/2007. | ||||
| Environmental Conditions: | Significant mercury mining activity occurred within the Oxbow Reservoir watershed (USGS, 2005). | ||||
| QAPP Information: | Data quality: Good. Quality Control for the fish sampling, tissue preparation and mercury analysis portions of this study was conducted in accordance with the AQ-11 Water Quality Technical Study Plan (PCWA, 2007). | ||||
| QAPP Information Reference(s): | |||||