New Mercury Regulations for California Rivers, Lakes, and Reservoirs
November 2, 2017
In May 2017, California’s State Water Resources Control Board (State Board) adopted new regulations for mercury, which took effect July 2017 following approval by the U.S. Environmental Protection Agency (EPA). These new stringent regulations include low mercury water quality objectives that may be unachievable for many industrial, municipal wastewater, and urban runoff dischargers, while doing little to address mercury from historical mining operations and domestic and regional atmospheric deposition—the dominant sources of mercury in California waters. Currently, the State Board is developing additional mercury requirements specific to lakes and reservoirs that could be adopted as early as 2018.

About the New Mercury Regulations

The new regulations establish numeric fish tissue objectives (ranging from 0.03 to 0.2 mg/kg), water column values applicable to wastewater and industrial discharges (ranging from 1 to 12 ng/L, or parts-per-trillion), and an implementation program to regulate mercury discharges. The regulations also incorporate the latest EPA guidance to protect the health of communities that consume higher-than-average quantities of fish caught in California waterbodies, establishing three new beneficial-use designations: (1) tribal and cultural use, (2) tribal subsistence fishing, and (3) subsistence fishing use by non-tribal communities or individuals.

The new objectives and beneficial-use designations are expected to result in National Pollutant Discharge Elimination System (NPDES) permit limits for mercury both below existing permit requirements and, in many cases, below levels that can be achieved with available technology.

Additional Proposed Regulations for Mercury Contamination in California Lakes And Reservoirs

The State Board is now pursuing a separate regulatory track for mercury contamination in California lakes and reservoirs—the Statewide Mercury Control Program for Reservoirs. In June 2017, the State Board distributed a questionnaire to operators of 132 California reservoirs identified as mercury-impaired to request information about the use, conditions, and management of the reservoirs. Survey results, draft regulatory language, and a detailed scientific staff report (currently under peer review) are being discussed in stakeholder workshops. 

The proposed regulations include a statewide total maximum daily load (TMDL) for mercury-impaired reservoirs to be implemented in two phases. In the first ten years (Phase I), pilot tests will evaluate management practices to reduce production and bioaccumulation of methylmercury—the most bioavailable and harmful form of mercury. Pilot tests may include adding oxidants to reservoir bottom waters and removing in-reservoir sediments. Phase II will then require implementation of the most effective practices demonstrated in Phase I. Public comment and adoption of the Statewide Mercury Control Program for Reservoirs is scheduled for 2018.

How Exponent Can Help

Exponent is currently working with clients affected by these new regulations. Consultants in our Health Sciences and Environmental practices can assist with composing technical comments on the proposed regulations; understanding what the regulations might mean for facility operations; reviewing and evaluating water quality, sediment, and fish tissue data; planning of monitoring and implementation strategies; evaluating treatment options; and negotiating permit limits.

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