New Efforts to Reduce Methylmercury in the Delta

Jun 27, 2011

The State Water Resources Control Board has approved new management measures aimed at reducing methylmercury pollution in the Sacramento-San Joaquin Delta Estuary and the Yolo Bypass, with the ultimate goal of making fish caught in the Delta safe to eat.

This Total Maximum Daily Load (or TMDL) has been debated for more than 10 years amongst state regulators, environmental advocates and those who oppose the new requirements. While no one, including Baykeeper, is completely satisfied with the TMDL, it is a necessary first step in tackling a source of pollution that California inherited as a legacy of the 19th century Gold Rush.

A TMDL is a management tool designed to reduce the overall input of a pollutant that comes from many different sources into a waterbody. The new Delta Methylmercury TMDL requires water managers, polluters and state agencies around the Delta to monitor for methylmercury and take measures to minimize methylmercury formation or transport.

Methylmercury is the biologically active form of mercury, which forms under certain anaerobic conditions, such as those found in wetlands. Methylmercury is bioaccumulative, meaning concentrations of the contaminant magnify as it travels up the food chain, resulting in neurological disorders, birth defects and toxicity at high concentrations. Mercury is found in the sediments of the Delta and Yolo Bypass due in large part to operations that date back to the Gold Rush, when mercury was mined in large volumes throughout the region and used in mining operations to separate gold from sediment and rock. Yolo Bypass in particular is a significant source and pathway of methylmercury because it serves to direct flood waters away from the Sacramento River, which in the process can create conditions suitable for transformation of elemental mercury to methylmercury.

One major weakness of the Delta Methylmercury TMDL is that it will not be fully implemented for approximately 20 years – leaving fish consumers and the ecosystem exposed to high levels of methylmercury for another generation. Additionally, fish consumption goals contained in the TMDL are limited to only eight ounces of fish per week even after the TMDL is fully implemented. This is likely far less than is consumed by some who fish in the Delta.

Environmental justice advocates, including tribal representatives and those from the Southeast Asian and African American communities, are disappointed with this target. They have, however, indicated a commitment to work with the State and Regional Water Boards to educate regular consumers of Delta fish and reduce consumption to safe levels. Alexis Strauss, Water Division Director of U.S. EPA Region 9, stated EPA's willingness to support education efforts with financial and technical assistance.

As with many of California's water problems, many realize that the issue of mercury contamination is a persistent and important problem, yet few are willing to take on the burden of paying for the remedies.

John Herrick from the South Delta Water Agency, which primarily represents farmers in the South Delta, felt his constituents were being forced to spend a disproportionate amount on long-term monitoring, since their operations possibly contribute only about 2% of the methylmercury found in the Delta.

An attorney from the Department of Water Resources (DWR), the state agency that manages water conveyance and flood control throughout the state, made the bold assertion that the open water load allocation for methylmercury should be completely removed. They believe that because DWR’s operations do not result in direct discharges of methylmercury to the Yolo Bypass and Delta, then they should not be held accountable for monitoring and mitigation of the problem.

Members of the State Water Board, however, recognized that DWR's management operations contribute to the transformation of mercury to methylmercury, and they were not swayed by the argument that DWR’s customers – many of which are located in Southern California – should not bear the burden of this problem. Board members indicated that this is a statewide problem and everyone that benefits from the Delta should contribute towards monitoring and the long-term remedies.

Baykeeper agrees with this position and will continue to advocate for mercury reductions throughout the San Francisco Bay and Delta Estuary. Controlling mercury is a key step toward the long-term restoration of the estuary and its once vibrant fisheries.

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