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Combined local, state and federal efforts significantly reduce mercury contamination in Tomales Bay

Release Date: 10/21/2005
Contact Information: Mark Merchant, U.S. EPA, (415) 947-4297

SAN FRANCISCO A cleanup and restoration project at the site of the biggest contributor of elemental mercury to Tomales Bay has been completed after six years through the combined efforts of Marin Conservation Corps, the U.S. Environmental Protection Agency and San Francisco Regional Water Quality Control Board.

Soil erosion and runoff from the abandoned Gambonini Mine, a 12-acre site on a steep hillside that drains to Salmon Creek, a tributary of Walker Creek on the north side of Tomales Bay, was sending as much as 180 pounds of mercury per year into the creek and bay as recently as 1999.

The multi-media cleanup effort initiated that year by the San Francisco Regional Water Quality Control Board and U.S. EPA has dramatically reduced the amount of mercury washing down from the mine site. A forthcoming technical report from the water board will detail the reduction of mercury in the creeks.

“We applaud the Regional Water Quality Control Board and the Marin Conservation Corps for their success in restoring this site,” said Alexis Strauss, director of the U.S. EPA’s Water Division in the Pacific Southwest Region. “The EPA was pleased to join these agencies and other citizens’ groups in demonstrating how we can work together to remove mercury from Tomales Bay and its environs."

In addition to the grading and filling of eroded areas of the site, where mining ceased in 1970, low-tech, relatively inexpensive erosion control techniques and revegetation of the area with native plants such as baccharis and ceanothus played major roles in the successful remediation of the site. Local participants in the work included the Marin Resource Conservation District, which contributed initial fieldwork and identified sediment sources on the site; and members of the Marin Conservation Corps, who provided much of the hand labor required for bioengineering, revegetation, and erosion control, all of which were critical components of this unique restoration project.

“This project provided corps members with the opportunity to learn about erosion control, mercury mining and environmental science concepts. It gave educational opportunities well beyond vocational training coming from extensive power tool use,” said Marilee Eckert, executive director of the Marin Conservation Corps.

The revegetation plan, which included soil remediation and development of a seed palette and local seed bank for the project as well as extensive planting, was developed by the state Department of Conservation and Department of Forestry. Local groups such as Circuit Rider Productions and the Marin Motorcycle Association contributed labor and expertise at various stages of the project.

“All of the agencies and organizations working on this project benefited from the collaboration,” says Dyan Whyte, senior geologist at the Water Board whose graduate research in the area quantified the mercury coming off the site and spurred the overall project. “And, the results in terms of mercury reduction seem to be exceeding all of our expectations. This has been a very rewarding project to work on, and what we’ve learned should be useful in many other watersheds where former mercury mines are causing major problems for water quality.”

Mercury has long been known to have toxic effects on humans and wildlife. Mercury is a toxic metal and a natural element, commonly seen as a shiny, silver-white, odorless liquid metal. Mercury is a toxic persistent, bioaccumulative pollutant that affects the nervous system. Methyl mercury is a chemical species that bioaccumulates in fish. Fish consumption advisories are in effect for mercury in thousands of lakes and rivers
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