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

The Environmental Protection Agency (EPA) is proposing to revise the current federal Clean Water Act selenium water quality criteria applicable to the 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. The San Francisco Bay and Delta ecosystem is at risk due to environmental degradation, including impacts from elevated levels of selenium, and state and federal actions are underway to restore the waterway. Scientific evidence indicates that elevated selenium levels can contribute to the decline of fish and aquatic- dependent birds. EPA promulgated the San Francisco Bay and Delta's existing selenium criteria in 1992 as part of the National Toxics Rule, using EPA's recommended aquatic life criteria values 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 San Francisco Bay and Delta. Therefore, EPA is proposing to revise the existing selenium criteria, taking into account available science, legal requirements, and EPA policies and guidance. EPA's proposal will address the Administrator's determination--described in this preamble--that EPA's previously promulgated water quality criteria are not adequate to protect the designated uses for these waters.