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San Francisco Bay Delta

Accelerate Water Quality Improvement

EPA is committed to accelerating water quality improvement and minimizing the negative impacts to aquatic life from contaminants and other stressors in the Bay Delta Estuary by working with California Water Boards to strengthen implementation of Total Maximum Daily Load (TMDLs) water quality improvement plans.

TMDLs are an important catalyst for restoring impaired water quality and protecting aquatic life.

There are nine adopted TMDLs in the Bay Delta Estuary watershed that address contaminants (pesticides and selenium) and stressors (low dissolved oxygen) considered potential contributors to aquatic ecosystem collapse and abrupt fish population declines.  There are also five adopted TMDLs that address mercury and methylmercury which has negative impacts on aquatic life and public health.

EPA produced 14 water quality progress reports that assess TMDL implementation progress and water quality improvement. We will use these reports and work with our partners to identify actions that accelerate water quality improvements and restore protection for beneficial uses.

EPA and the California Central Valley Water Quality Control Board evaluated mercury and methylmercury on agricultural fields in the Sacramento-San Joaquin Delta (Delta) to advance implementation of the Delta Mercury and Methylmercury TMDL. This project expands the available knowledge about Delta agricultural sites as sources of mercury and methylmercury to the Delta ecosystem. Sampling results are summarized in the final report, Characterization of the Methylmercury Loads for Irrigated Agriculture in the Delta.

TMDL Resources