Final California 2018 Integrated Report (303(d) List/305(b) Report)

Supporting Information

Regional Board 5 - Central Valley Region

Water Body Name:	Davis Creek (upstream from Davis Creek Reservoir, Yolo County)
Water Body ID:	CAR5133201020080623175452
Water Body Type:	River & Stream


DECISION ID	74070	Region 5
Davis Creek (upstream from Davis Creek Reservoir, Yolo County)

Pollutant:	Mercury
Final Listing Decision:	Do Not Delist from 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	Do Not Delist from 303(d) list (TMDL required list)(2016)
Revision Status	Original
Sources:	A Source Unknown
Expected TMDL Completion Date:	2027
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. LOE 22623 was not used in the final listing decision because of a criterion change. The data in LOE 22623 were reassessed in LOE 95476 with the new criterion. LOE 95476 was used in the final listing decision. 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 2 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 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.

Line of Evidence (LOE) for Decision ID 74070, Mercury	Region 5
Davis Creek (upstream from Davis Creek Reservoir, Yolo County)

LOE ID:

95476

Pollutant:

Mercury

LOE Subgroup:

Pollutant-Tissue

Matrix:

Tissue

Fraction:

Total

Beneficial Use:

Commercial or recreational collection of fish, shellfish, or organisms

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Two California Roach composite samples were collected for tissue analysis at one location from this reach. Both of the samples exceeded the USEPA fish tissue criterion for human health. These samples were analyzed as whole fish samples, which were translated to a filet concentration by multiplying the whole body concentration by 1.62 (Peterson et al, 2007). The wet weight mercury concentrations of these fish tissue samples were 1.03 ppm and 1.24 ppm. Both composite samples were collected from fish with average total lengths less than 150 mm.

Data Reference:

Mercury Bioaccumulation and Trophic Transfer in the Cache Creek Watershed, California, in Relation to Diverse Aqueous Mercury Exposure Conditions. CALFED Mercury Program Final Project Report. January 25, 2004

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 U.S. EPA 304(a)-recommended water quality criterion for concentrations of methylmercury in fish tissue of trophic level 4 fish (150 - 500 mm; fillet wet weight) is 0.20 mg/Kg.

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 this reach of Davis Creek near the crossing of County Road 40, above Davis Creek Reservoir.

Temporal Representation:

Fish samples were collected during one sampling event on 8/4/2000.

Environmental Conditions:

Significant mercury mining activity occurred within the Davis Creek watershed (USGS, 2005).

QAPP Information:

Data quality: Excellent.. Quality Control for all of the elements described in section 6.1.4 of the Policy was conducted in accordance with the CALFED Mercury Project QAPP (Puckett and van Buuren, 2000).

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 74070, Mercury	Region 5
Davis Creek (upstream from Davis Creek Reservoir, Yolo County)