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Lava Cap Mine cleanup surges forward

While the Gold Rush left a rich vein for historians, it also left an eventual environmental disaster at the Lava Cap Mine five miles east of Grass Valley.

A public meeting Thursday seeks local input on how to clean up Nevada County’s only Superfund environmental site, which leaked arsenic into the water and soil.

In 1979, state water officials found that a rotting log dam at the site was leaking arsenic-contaminated mine tailings into Little Clipper Creek, which runs into Clipper Creek and the Lost Lake residential area.



By 1994, U.S. Environmental Protection Agency soil tests showed that there were elevated levels of arsenic and lead on the mine property. High levels of arsenic can cause cancer, and lead has been traced to developmental problems in children.

Then, during a major winter storm in 1997, the top of the dam collapsed, sending 10,000 cubic yards of the tainted tailings into Little Clipper Creek. As a result, the EPA designated the area a Superfund site that fall. The EPA draws upon its Superfund money for major cleanup sites where the polluter is unknown or cannot pay for it.




The Lava Cap Mine opened in 1861 and was operated on and off until 1943. The ore contained natural arsenic, and a cyanide process used to extract gold left even more of the poison in the tailings, according to the EPA.

A preliminary cost of $13.2 million has been estimated for the cleanup, which will deal with more than 8,000 truckloads of tailings and waste rock, according to EPA figures and project manager Dave Seter.

Seter said last week that the EPA has also been addressing groundwater concerns in the area by sampling wells.

Samplings from the past few years from wells on Tensy Lane, off of Greenhorn Road, have shown the water there is currently safe, Seter said. Some of the wells in the area have arsenic in them and some do not, Seter said, but no one has been exposed to abnormal levels.

One family had concentrations that were high enough to cause concern and have put in a cleansing system to deal with it, Seter said. “It’s wise for them to treat the water,” he said.

The EPA is still working on the separate groundwater study and will present another cleanup plan for the area’s aquifer at a later date. While the mine site puts off a lot of natural arsenic, like many in the Sierra, the wells at the Lava Cap site show higher levels of arsenic than normal, the EPA said.

In a notice for the upcoming meeting, the EPA said that arsenic in uncovered tailings at the site can become airborne as dust during the summer.

“This source material is highly toxic and highly mobile” and “presents a significant risk, should exposure occur,” the EPA said.

The EPA has offered several plans for dealing with the cleanup, including an alternative of doing nothing at all. But the agency prefers to take several steps, including:

– Excavating contaminated soil at four residences on the mine site. One has been evacuated, another is about to be, and the last two are far enough away that they can be made safe by the earth removal, Seter said.

– Covering the mine tailings and diverting surface water around them.

– Replacing the log dam with a rock structure.

– Using a process to collect and treat water with high levels of arsenic currently draining from the old mine shaft and the tailings.

But those plans could change with public input.

For more information on the subject, documents can be reviewed at the Nevada County Library or the Grass Valley Public Library. Written comments will be received by the EPA from Feb. 25 to March 26 at: U.S. Environmental Protection Agency, Region 9, Attention: Don Hodge, 75 Hawthorne Street, San Francisco, CA, 94105. Hodge’s e-mail address is hodge.don@epa.gov.


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