July 16, 2008

State Board Orders Water Plan to Clean Mercury in W. Marin

By Mark Prado, The Marin Independent Journal, Novato, Calif.

Jul. 15--Areas of West Marin laden with toxic mercury including Soulajule Reservoir and Walker Creek need to be cleaned up under a plan approved by a state agency on Tuesday.

The poisonous legacy of West Marin's mercury mines is contaminating fisheries and impairing water quality, according to state water regulators.

On Tuesday the state's Water Resources Control Board adopted a plan to curb mercury contamination by having the Marin Municipal Water District assess the problem in Soulajule and have landowners make sure areas along the banks of the lower end of Walker Creek that contain mercury are not disturbed.

"We are asking by 2009 that the water district evaluate Soulajule Reservoir and determine if there are any control measures that can be put into place to reduce the mercury," said Dyan Whyte, senior engineering geologist with the state Regional Water Quality Control Board. "We also want to work in grazing areas where mercury could be disturbed."

Marin Municipal Water District's top official said he is ready to do the assessment.

"We are ready to monitor and mitigate the mercury in the fishery," said Paul Helliker, Marin Municipal's Water District's general manager.

The initial study will cost the district between $80,000 and $150,000, and the district will have to come up with ways to ease the problem.

Whyte stressed residents have no reason to be concerned about drinking water, noting that tests show water is well within strict quality guidelines.

Furthermore, Soulajule is a reserve reservoir and typically does not contribute to Marin's daily water supply.

But both the reservoir and Walker Creek are listed under the Clean Water Act as violating water quality standards because of elevated levels of mercury.

"We are seeing mercury accumulation in the food chain," she said.

Test results showing mercury in fish prompted guidelines in 2004 detailing safe consumption levels for largemouth bass, channel catfish, black crappie and other fish found in the reservoir.

When mercury is absorbed by invertebrates that live in sediment, such as worms, bacteria in those organisms transform the mercury into a more toxic form called methylmercury,a toxin which remains in the organism's system.

Small fish eat the invertebrates and those fish are eaten by bigger fish, increasing the level of methylmercury in each species up the food chain.

Mercury occurs naturally throughout the area. The area near Walker Creek was a hotbed for the mining of mercury in the 1960s and early 1970s. The Gambonini, Chileno Valley, Franciscan and Cycle mines all operated in the area. Soulajule, built in 1979, was built on top of remnants of the Franciscan and Cycle mines and a tailings pile, among other remains of mining operations, officials said.

The area is rich in cinnabar ore, which was pulverized, milled, then heated in a distillery to produce mercury in a liquid form. The mercury was used in thermometers, dental fillings, fluorescent lights and high-temperature military gauges. At the time, mercury was listed by the military as a controlled substance, which increased its value.

In 1970, the military removed mercury from its list of controlled materials, the market for mercury dropped and the mining operations went out of business. They left behind abandoned mines and "tailings," residues produced by the crushing and milling of cinnabar ore.

When the Buttes Gas and Oil Co. closed its Gambonini mercury mine, which operated from 1964 to 1970 on Marshall-Petaluma Road, it built an earthen wall to hold back mercury residue, but the barrier broke under the pressure of rain during the "Great Storm" of 1982.

About 170 pounds of mercury eroded from the mine site, flowed into Walker Creek and slipped into Tomales Bay over two decades. The state has since worked to contain the site.

"The good news is mercury counts are coming down quite a lot at the Gambonini mine," Whyte said.

Contact Mark Prado via e-mail at [email protected]


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Copyright (c) 2008, The Marin Independent Journal, Novato, Calif.

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