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Independent Science Review and Advice of the Delta Mercury Control Program



The Sacramento-San Joaquin Delta is identified in the Clean Water Act’s Section 303(d) list of impaired water bodies due to harmful levels of mercury in some fish eaten by people and wildlife. In response, the Central Valley Regional Water Quality Control Board (Regional Board) developed a Delta Mercury Control Program (Mercury Control Program) to control mercury and methylmercury in the Delta. The Mercury Control Program was adopted by the Regional Board as an amendment to the Water Quality Control Plan for the Sacramento River and San Joaquin River Basins (Basin Plan) in April 2010. The Mercury Control Program received its final approval from the U.S. Environmental Protection Agency in October 2011.


The Mercury Control Program is a two-phased process. During Phase 1, which began on October 20, 2011, the Regional Board required entities responsible for reducing methylmercury in the Delta to participate in studies to develop and evaluate ways to manage methylmercury. During Phase 2, beginning in 2022 following the review, dischargers will implement methylmercury and inorganic (total) control programs as appropriate, based on the individual and aggregate findings of the methylmercury characterization and control studies.


Prior to implementing Phase 2, the Basin Plan requires the Regional Board to conduct a Phase 1 Mercury Control Program review to inform re-evaluation of the Mercury Control Program including the fish tissue objectives, linkage analysis (between sources and objectives), and allocations.


The Regional Board has requested the Delta Science Program to convene two panels:


1. An independent scientific review panel (Review Panel) to conduct a review of the control and characterization study reports to evaluate the scientific validity of the studies’ findings, and 


2. An independent advisory panel (Advisory Panel) to provide a holistic review of documents synthesizing available information and providing recommendations on Phase 2 implementation of the Mercury Control Program.


The Delta Science Program will coordinate the review and advice in accordance with its mission to provide the best possible unbiased scientific information to inform water and environmental decision-making.


Access the request letter from the Regional Board to Delta Lead Scientist John Callaway here, and his response here.


Independent Scientific Review Process

There will be two parts to the review. The first set of letter reviews will be conducted in spring 2019, with the second set following in 2020. The final reports requiring review in 2019 consist of control studies that address methylmercury discharges from point sources (wastewater and urban stormwater runoff) and nonpoint sources (water management, flood control, wetlands, and irrigated agriculture). Final reports requiring review in 2020 focus on characterization studies for a large settling basin and tidal wetlands as well as a mercury model for open water in the Delta and Yolo Bypass.


Independent Advisory Panel Process

The Advisory Panel will not be convened until the Review Panel has completed their work. The Advisory Panel will be asked to provide recommendations for science needs to inform future potential implementation measures for the Regional Board to consider when it revises the Mercury Control Program. The advisors would utilize the results of the methylmercury control study review, other background information, and the current state of mercury science to develop the recommendations. After identifying data and information gaps that still need to be addressed for mercury and methylmercury controls, the Advisory Panel would provide recommendations for further studies and implementation plans and advise on the priority of those proposed recommendations. Deliberations by the Advisory Panel will be conducted during a public workshop. Access review materials and supplemental documents here.


Charge to the Independent Review Panel

The charge to the panel provides the orientation and focus, materials to be reviewed, and specific questions for the panel to start the review process. It provides the direction, context, and timeline for the review.


Review Panel Members

- Dr. Christopher Knights, Environmental Engineer, U.S. Environmental Protection Agency (Chair)

- Dr. Brian Branfireun, Professor, Western University (Lead Author)

- Dr. Cindy Gilmour, Senior Research Scientist, Smithsonian Environmental Research Center

- Dr. Robert Mason, Professor, University of Connecticut

- Dr. Carl Mitchell, Professor, University of Toronto


Read more about the panel members here.

Coequal goals

The Delta Stewardship Council was created in legislation to achieve the state mandated coequal goals for the Delta. "'Coequal goals' means the two goals of providing a more reliable water supply for California and protecting, restoring, and enhancing the Delta ecosystem. The coequal goals shall be achieved in a manner that protects and enhances the unique cultural, recreational, natural resource, and agricultural values of the Delta as an evolving place." (CA Water Code §85054)