Is the Anaconda Mine a "Superfund" site?
EPA is addressing the issues at the Anaconda Mine using its authority under the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA), which is commonly named “Superfund.” Therefore, the Anaconda Mine is considered a Superfund site. EPA can use CERCLA authority to conduct investigations and removal actions, and compel work by responsible parties (in this case, Atlantic Richfield Company). The State of Nevada requested that EPA use our Superfund authority in 2005.
EPA has not proposed the site for the NPL. The main difference between NPL sites and other Superfund sites is that we cannot spend Superfund money to conduct long-term cleanups. We can use Superfund money to conduct long-term cleanups on NPL sites only.
Site description and history
The Anaconda Copper Mine site covers more than 3,400 acres in the Mason Valley, near the city of Yerington, in Lyon County, central Nevada, approximately 65 miles southeast of Reno. The Singaste Range 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) managed public land to the south, and the Walker River and the city of Yerington to the east. Portions of the site are owned by Arimetco (in bankruptcy) and portions are BLM managed public lands.
Copper was discovered in the Yerington District in 1865, and operations at this mine site began in 1918 as the Empire Nevada Mine. Anaconda purchased the mine in 1941. From approximately 1952 to 1978, Anaconda conducted mining and milling operations at the open-pit, low-grade copper mine. Anaconda processed both copper oxide and copper sulfide ores. They removed overburden and ore from the pit, which required pumping groundwater out of the pit to get to the ore. The processing of the copper oxide ore involved large quantities of sulfuric acid, made in an on-site 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. Anaconda mining operations generated approximately 360 million tons of ore and debris from the open pit and 15 million tons of overburden resulting in 400 acres of waste rock placed south of the Pit, 900 acres of contaminated tailings, and 300 acres of disposal ponds.
In 1977, Atlantic Richfield Company (ARC) 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. All activities were shut down in 1982. Groundwater pumping out of the pit stopped when Anaconda operations ceased, resulting in the 180-acre Pit Lake. It is about one mile long, 800 feet deep with 500 feet of water, and contains around 40,000 acre-feet of water which increases at the rate of 10 feet/year.
In 1982, the property was sold to Don Tibbals, who refurbished Weed Heights, conducted some operations, and leased portions of the site to various companies. Following Anaconda’s sale of the site, portions of the site were used for extracting copper from the tailing and waste rock piles and as a metal salvage and transformer recycling facility. Arimetco bought the property from Tibbals in 1988 and pursued leaching operations on the site, eventually building an electrowinning plant and five heap leach pads to produce copper. They used tailings material left by Anaconda and added some new ore resulting in 250 acres of heap leach piles and 12 acres of heap leach solution collection ponds. Arimetco went bankrupt in 1997 and abandoned the site in 2000.
NDEP and EPA have taken several emergency removal actions at the site to address immediate concerns, and have required ARC to begin remedial investigations and feasibility studies to determine the extent of contamination and potential cleanup options for the site. EPA has initiated a remedial investigation of the Arimetco portions of the site. Please see the Response Action Status section for detailed information about the removal and investigation activities to date.
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