The Atlantic Richfield Co. (ARCO) has been ordered to reimburse the federal government $2.77 million for work already performed to clean up abandoned wastes from the Anaconda copper mine that are contaminating air and water in central Nevada. The order issued by the U.S. Environmental Protection Agency (EPA) also requires ARCO to fund and develop a plan for a technical assistance program to facilitate additional community involvement in the continuing response activities at the site.
Because the Anaconda mine site is not on or proposed for the EPA’s Superfund List, the company’s continued participation in this process is essential to cleaning up the site.
'Recovering these funds is an important step in moving the Anaconda Mine cleanup forward,' said Keith Takata, director of the EPA’s Pacific Southwest Superfund Division. 'We can use the funds to continue the cleanup while we work with our state and local partners find a more permanent solution."
The Anaconda mine site covers more than 3,400 acres in the Mason Valley, 65 miles southeast of Reno. The Singaste Mountains and the town of Weed Heights lie to the west, open agricultural fields and homes to the north, U.S. Bureau of Land Management (BLM) public land to the south and the Walker River and the city of Yerington to the east.
The major environmental threats on the site come from metal contaminating the groundwater and fugitive dust that could impact human health and surface water. Contaminated surface water can harm wildlife as well as people. Mining operations enhanced levels of naturally occurring uranium, thorium and radium, making the radiological substances more pervasive and mobile in and around the site.
Originally known as the Empire Nevada Mine, the site began operation around 1918. Anaconda purchased the Mine in 1941 and from 1952 to 1978 conducted mining and milling operations at the open-pit, low-grade copper mine. The processing of the copper oxide ore involved large quantities of sulfuric acid, made in an onsite sulfuric acid manufacturing plant. The ore processing created liquid and solid wastes such as tailing piles, waste rock areas, liquid waste ponds, leach vats, heap leach pads and evaporation ponds.
In 1977, ARCO bought Anaconda. A decrease in copper prices, lower priced foreign imports and declining grade and amount of ore available forced the closure of Anaconda’s copper mining operations in 1978, and all activities were shut down in 1982. From 1977 to 1982, the company was owned by Atlantic Richfield Co. and then sold to Don Tibbals, a local resident, who subsequently sold his interests, with the exception of the Weed Heights community, to Arimetco Inc. Arimetco operated a copper recovery operation from existing ore heaps within the site from 1989 to November 1999. Arimetco has terminated operations at the site and is currently managed under the protection of the U.S. Bankruptcy Court in Tucson, Ariz.
Today, parts of the site are public lands managed by the BLM and parts are owned by Arimetco. Since 2000, the EPA has spent about $6 million at the Anaconda Mine site investigating and addressing wastes abandoned there. In 2006, the EPA capped 100 acres of mine tailings to prevent erosion and dust blowing from the site. The agency also constructed and lined a new pond before the fall and winter rain season to prevent overflow of mine drainage.
Under two previous orders, ARCO is performing other response actions at the site, including broad investigation of the nature and extent of groundwater contamination. Ultimately, according to the EPA, the massive leach heaps and the leach fluid ponds must be addressed to prevent further contamination of groundwater.
