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EPA proposes cleanup plan for part of Nevada County Superfund site; public meeting slated to discuss proposal and alternatives

Release Date: 2/26/2004
Contact Information: Mark Merchant, (415) 947-4297

SAN FRANCISCO -- The U.S. Environmental Protection Agency today announced it is proposing a cleanup plan for one part of the Lava Cap Mine Superfund site, which is east of Grass Valley, Calif.

Public comment on the EPA's plan, as well as a number of alternatives, are open from Feb. 25 to March 26. In addition, the EPA will be holding a public meeting on the plan and alternatives in Grass Valley today.

This plan addresses contamination from what is known as the Mine Area Operable Unit. This area includes a pile of tailings a byproduct of ore processing as well as the mine shaft and buildings, mine residences, and the creek just below the tailings pile.

The EPA will propose cleanup plans for other areas of the Superfund site specifically the Lost Lake area, as well as for groundwater contamination in the Little Clipper Creek watershed at a later date.

The Lava Cap Mine site was placed on the National Priorities List, the national list of Superfund sites, in February 1999. The mine itself was in operation from 1861 to 1943 and a flotation plant and later a cyanide process were used to extract gold from the ore, which also contained naturally occurring arsenic. The process left the arsenic in the finely ground tailings that were deposited in a drainage area of Little Clipper Creek area behind a log dam.

During a major winter storm in January 1997, the upper half of the log dam collapsed sending more than 10,000 cubic yards of tailings into the creek. Studies later that year by the state and the EPA showed very high arsenic concentrations and the potential for more. By 1998, thousands of cubic yards of tailing had been moved and stabilized and drainage in the area improved.

EPA's proposed solution for the contamination at the mine area, which is the preferred alternative, includes:

• Mine tailings and waste rock, tailings dam, mine buildings, surface water: Consolidate,

regrade and cap tailings on-site with impermeable membrane; cover tailings and waste rock
with soil and revegetate; replace the log dam with a rock buttress; divert clean surface water
flow around the mine tailings; collect and treat contaminated water draining from the mine
shaft and from the tailings; and remove tanks, vats, sumps, and contaminated soil from mine
buildings, disposing of this material with the mine tailings or as hazardous waste where
necessary

• Former mine residences: Demolish residence closest to the tailings pile; remove soil around

two other residences and replace it with clean soil; move excavated material to the mine
tailings pile for long-term management

• Little Clipper Creek to Greenhorn Road: Excavate tailings and contaminated sediment

accumulations and haul excavated material to the mine tailings pile for long-term
management

The public is encouraged to provide comments on this plan either in person during the Feb. 26 public hearing or in writing via letter, fax, or e-mail. The EPA will consider your comments and respond in writing as we develop the final decision on the selected alternative.

For more information, visit the EPA's Lava Cap Mine Web site at:
https://yosemite.epa.gov/r9/sfund/overview.nsf