Copper listing is based on the possible impairment of estuarine beneficial uses, including fish spawning and estuarine habitat. Regional Monitoring Program data show that copper concentrations exceed threshold toxicities for sensitive aquatic indicator species, including organisms used to derive USEPA's National Toxics Rule (NTR) criteria and USEPA's proposed California Toxics Rule (CTR) criteria. Dissolved copper concentrations exceed the CTR saltwater criterion more than half of the times sampled in South San Francisco and western San Pablo Bay, and more than a third of the time in other shallow embayments of the northern reach.
When CTR is promulgated, the dissolved criteria will become the default water quality objectives for all Bay segments, unless USEPA approves site specific objectives.
The Regional Board is using the Santa Clara Basin Watershed Management Initiative as a stakeholder forum for development of a TMDL for copper in South San Francisco Bay including consideration of a site specific objective for copper. Studies conducted by the City of San Jose in accordance with USEPA guidance to support a site specific objective are currently being reviewed. Regional Board staff have developed a plan to test the applicability of the potential South San Francisco Bay site specific objective to other Bay segments.