Mining Program - Region 5 Success Stories
The Walker Mine, Plumas County
The Walker Mine, Plumas County
Photographs of Mine Site
The Walker Mine is an 800-acre inactive underground copper mine in east-central Plumas County about 15 miles northeast of Quincy. The mine is at anelevation of about 6,180 feet. The mine is estimated to contain about 13 miles of tunnels and 3,500 feet of vertical shafts. The Walker Mine was discovered in 1904, put into operation in 1915, and active mining took place until 1941. Since closure of the mine in 1941, the site has discharged acid mine drainage and heavy metals directly into Dolly Creek and Little Grizzly Creek.
Ownership of Walker Mine has changed throughout the years. From 1915 through 1941 it was owned and operated by Walker Mining Company and International Smelting and Refining Company (ISRC). ISRC was a subsidiary ofthe Anaconda Copper Mining Company which was purchased by Atlantic Richfield Company (ARCO) in 1977. In 2000 ARCO became a subsidiary of British Petroleum.
From the mid 1940s until the early 1990s, Walker Mine was controlled by Calicopia Corporation and Robert R. Barry. Cedar Point Properties Inc., bought the Walker Mine at a Plumas County tax sale in 1997 and abandoned it a few years later after the Regional Board issued a Cleanup and Abatement Order requiring Cedar Point Properties to comply with the Operations and Maintenance Procedures developed by the Regional Boardfor the Walker Mine site.
In November 1987, the Regional Board installed an engineered concrete mine seal 2,675 feet from the 700-level portal of the Walker Mine. This seal was installed to prevent direct discharge of acid mine drainage from the underground ore zone to the surface waters of Dolly Creek.
Water coming out of the mine had low pH and high concentrations of copper. The mine fills with water from infiltration of rain water and snow melt through varies sink holes and surface fractures. Copper concentrations in the mine discharge prior to installation of the mine seal were 280 ug/L. Mine water discharged into a small settling pond, which then discharged to Dolly Creek. The pH in the settling pond varied between 2.5-5.
To solve the problem of acid mine drainage water flowing out of the mine, the Regional Board installed an engineered concrete seal in the 700 level adit of the Walker Mine. The mine seal has significantly reduced acid mine drainage from the mine.
Cleanup and remediation activities have also been initiated by the US Department of Agriculture(US Forest Service) at the adjacent 70-acre Walker Mine Tailings facility located on land managed by the US Forest Service. Both Dolly Creek and Little Grizzly Creek run through the tailings facility site. Copper concentrations in Little Grizzly Creek downstream of the tailings site were around 288-691ug/L. Dolly Creek also had increased levels of zinc.
The U.S. Forest Service has addressed this problem by diverting a portion of Dolly Creek into a lined channel that prevents contact with the tailings which then discharges directly to Little Grizzly Creek. Doing this has effectively reduced the level of copper and zinc in both creeks but has not eliminated it.
Both projects have helped reduce the amount of metals entering Dolly Creek and Little Grizzly Creek. The mine seal has reduced the amount of metals being discharged from the Walker Mine. . Diverting Dolly Creek into the lined channel has helped reduce the concentration of metals in the both creeks closer to background levels but has not reached background levels.
