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Water Quality Standards: Establishment of Revised Numeric Criteria for Selenium for the San Francisco Bay and Delta, State of California


EPA is proposing to revise the current federal Clean Water Act (CWA) selenium water quality criteria applicable to the salt and estuarine waters of San Francisco Bay and Delta to ensure that the criteria are set at levels that protect aquatic life and aquatic-dependent wildlife, including federally listed threatened and endangered species.

EPA promulgated the San Francisco Bay and Delta's existing selenium criteria in 1992 as part of the National Toxics Rule (NTR), using EPA's CWA section 304(a) recommended aquatic life criteria for selenium at the time. However, the latest science on selenium fate and bioaccumulation indicates that the existing criteria are not protective of aquatic life and aquatic-dependent wildlife in the salt and estuarine waters of the San Francisco Bay and Delta. EPA determined that new or revised selenium criteria in the salt and estuarine waters of the San Francisco Bay and Delta are necessary to protect the designated uses for these waters. Therefore, to protect aquatic life and aquatic-dependent wildlife in the San Francisco Bay and Delta from the adverse effects of selenium, EPA is proposing the criteria in this rule using the best available science.

Public Hearings

EPA offered one virtual public hearing and two in-person public hearings so interested parties could provide oral comments on EPA's proposed rule. The hearings occurred on August 22 and 23, 2016.  EPA will consider all of the oral comments provided along with the written public comments submitted via the docket for this rulemaking.

Comments on the Proposal

The original 60-day comment period for this proposal opened on July 15, 2016.  Comments on the proposed rule were accepted at (Docket ID No. EPA-HQ-OW-2015-0392). EPA extended the public comment period on the proposal for 45 days in response to requests from stakeholders. The new comment period ended October 28, 2016.

Some commenters expressed concern over whether the proposed criteria were appropriate for the South Bay, because data specific to the North Bay and Delta had been used to develop the water column criteria using the U.S. Geological Survey (USGS) Ecosystem-Scale Selenium Model.  In response, the EPA asked the USGS to investigate whether sufficient site-specific data existed for the South Bay to reliably run the model for the South Bay area (see report below).

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