Tomales Bay Mercury TMDL

The Water Board does not foresee a need for any more actions to address mercury in Tomales Bay. Mercury concentrations at the Walker Creek delta in Tomales Bay have already decreased as a result of cleanup of the Gambonini mercury mine on Walker Creek in 2000. It appears that additional actions already required by the Walker Creek watershed mercury TMDL, particularly the grazing waiver (also required by the Tomales Bay pathogens TMDL, will be sufficient. We plan to monitor mercury in the Bay to ensure that mercury concentrations continue to decrease.

Tentative Project Schedule

Summer 2011: public meeting and presentation—in the Tomales area. Stay tuned for meeting details by subscribing to the e-mail notification list.
January 2012: Water Board hearing to consider adoption of this TMDL
June 2012: we anticipate U.S. EPA will approve this TMDL in June 2012

Documents

We plan to release a Staff Report for public review prior to January 2012. Subscribe to our e-mail list to be notified when the Staff Report and other mercury TMDL documents are released
In July 2010, Aquatic Science Center completed the following report: Impairment Assessment for Mercury in Tomales Bay, CA
In October 2010, Aquatic Science Center completed the following addendum: Tomales Bay Hg IA Addendum

Background

The Bay is located in the Gulf of the Farallones National Marine Sanctuary, and is renowned for its wildlife, fishery and shellfish. In their stewardship plan, the Tomales Bay Watershed Council describes:

Hundreds of species of mammals, birds, invertebrates and plants, and many threatened and endangered species inhabit the watershed… which is also an important foraging and haul out site for marine mammals and over-wintering area and migratory stop along the Pacific Flyway for many species of birds, including approximately 20,000 shorebirds and 22,000-25,000 waterfowl.

The Gambonini mercury mine is by far the largest source of mercury to Tomales Bay. Mercury concentrations in several fish species and crab warrant a consumption advisory to protect human health. Commercial shellfish (oysters, mussels, and clams), and wild clams are safe for human consumption. In 2010, we found high mercury concentrations in some wildlife prey, which is also of concern. We anticipate that mercury concentrations will continue to decrease, so that fish and shellfish will become safe for consumption by humans and wildlife.

For More Information Contact:

Carrie Austin
Water Resources Control Engineer
1515 Clay Street, Suite 1400
Oakland, CA 94612
Phone: 510-622-1015
Fax: 510-622-2460