U.S. EPA Proposes Greater Protection from Selenium in San Francisco Bay and Delta
Threatened and endangered species at risk from selenium
The U.S. Environmental Protection Agency proposed a federal Clean Water Act rule to tighten the current selenium water quality criteria for the waters of San Francisco Bay and Delta. The proposed change would better protect aquatic species, including salmon, smelt, and diving ducks, that are dependent on the Bay and Delta ecosystem, from harmful exposure to elevated levels of selenium.
“Reducing selenium in the San Francisco Bay and Delta will benefit the wildlife that are part of this critical ecosystem,” said Alexis Strauss, EPA’s Acting Regional Administrator for the Pacific Southwest. “This proposal is based on years of scientific study, and will accelerate the restoration of the Bay and Delta.”
The Bay and Delta support a significant diversity of fish and wildlife species including federally listed threatened and endangered green sturgeon, Chinook salmon, steelhead trout, delta smelt and the California Ridgway’s rail, as well as many migratory bird species that use the estuary as a wintering ground.
Selenium levels from agricultural runoff and oil refinery discharges have been reduced due to previous state and federal regulatory requirements. EPA set selenium limits for the Bay and Delta in 1992, yet the latest research on bioaccumulation of selenium indicates that the existing federal criteria of 5 parts per billion are insufficient to protect aquatic and aquatic dependent species in these water bodies. Today’s proposal calls for more stringent selenium water quality criteria of 0.2 parts per billion, which would be the basis to limit selenium sources through the implementation of state regulations.
Ambient selenium conditions in the Bay and Delta must remain low to sustain healthy populations of fish and wildlife. The population explosion of an invasive clam species, commonly known as Corbula, has resulted in a rapid rate of acceleration of selenium accumulation in the food chain of fish and bird species in the Bay and Delta. EPA scientists considered this fact and the latest science on selenium toxicity and accumulation to determine the new and revised criteria for whole body and muscle fish tissue, clam tissue, and water column concentrations.
The proposed rule will be available to the public for a 60-day comment period following publication in the Federal Register. EPA will also host a virtual public hearing on August 22, and in-person public hearings in its San Francisco office on August 23. For more information, including a prepublication of the rule, please visit EPA’s website at: https://epa.gov/wqs-tech/water-quality-standards-establishment-revised-numeric-criteria-selenium-san-francisco-bay.
Image Credit: The Vallejo Delta in the San Francisco bay area. Copyright: obelix / 123RF Stock Photo