Mine no longer leaks into bay

11/03/2011

A 50-year-old now-defunct mercury mine remediated with natural vegetation in the late 1990s is no longer leaking toxic metal into Tomales Bay, officials say. The flow of mercury into the bay from the 14-acre mining site during rainy months became a major environmental concern after state researchers measured unusually high quantities of it in area tributaries in the spring of 1998. Dyan Whyte, an assistant executive officer with the state Regional Water Quality Control Board and principal coordinator for the remediation project, decided that, rather than capping the mine with man-made material, she and her crews would cultivate native plants to stabilize the hillside where the mine once existed. Plants would provide both a natural look to the site and, with time, an organic detection device for any future mercury leaks. “We knew it would take a significant amount of time for the revegetation to take hold,” Whyte said. “But our hope was to see incremental annual improvements.” Two other former mine sites exist in West Marin, but those relied on the now-remediated site for processing and therefore pose significantly less risk of run-off, she added.