Yerington Monday: Anaconda Copper Mine, Part Two: Anaconda Mine in Mason Valley
The Anaconda Copper Mine
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.The Anaconda Mine first opened in 1918 as the Empire-Nevada Mine. In 1941 the Yerington property was acquired by the Anaconda Copper Company. Mining and milling operations began in 1952 and ran until mining operations ceased in 1978 due to low copper prices and declining grades in the open pit.
Authentic Yerington Nevada Copper Mine Gem Stone w/Turquoise Cabochon
The Anaconda arrowhead logo is still visible on the water tank near the Yerington Mine.
Old Anaconda mine.
Anaconda Haul Truck 1956 
Anaconda & Weed Heights, 1960’s
Excavator 1962
Blasting Crew 1962
Abandoned processing facilities at the Anaconda Copper Mine,
Weed Heights. Former company town, now a rental community.
Tailings Pond.
Open pit mine. Too toxic to be a water park
The Anaconda mine operated for 25 years and produced approximately 360 million tons of material from the pit. Most of the material remains in tailings or in leach heap piles. The copper was processed from the extracted ore using two processes. Copper oxide ore (from the upper portion of the pit) was processed by heap leaching, either directly with sulfuric acid in vats to produce a copper solution precipitated by passing it over scrap iron, or by leaching successively in acid and kerosene solutions, subsequently electro plating onto stainless steel sheets. Copper sulfide ore from the lower portion of the pit was processed by crushing, and flotation with calcium oxide added to the solution to maintain an alkaline pH.
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 85 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.
Anaconda Pit filled with toxic water
Pictured is a portion of the area of the Anaconda mine the EPA has proposed to be listed on the National Priorities List as a Superfund site.
Anaconda Pit
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.
Atlantic Richfield Company
Anaconda had become a subsidiary of Atlantic Richfield Company in 1977. Environmental liability for the Anaconda Mine remains with ARCO, which is now a subsidiary of British Petroleum, and known as BP West Coast Products LLC.
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.
Atlantic Richfield Company (ARC) is an oil company that was formed by the merger of East Coast-based Atlantic Refining and California-based Richfield Petroleum in 1966. Since 2000, ARC has been a subsidiary of British Petroleum (BP), and is officially known as BP West Coast Products LLC.
Don Tibbals
Donald H. Tibbals
In 1982, the property was sold to Don Tibbals, a Lyon County Commissioner, 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.
Arimetco
Arimetco, also known as Arizona Metals Company, based out of Tucson, AZ, purchased the property from Tibbals in 1988. Arimetco built additional facilities and operated at the mine until 2000 after filing for bankruptcy in 1997. In 1997 Arimetco went bankrupt and effectively abandoned the site in 2000.
Arimetco pursued leaching operations on the site, eventually building an electrowinning plant and five heap leach pads to produce copper. Arimetco, Inc. owns and operates mine deposits in Yerington, Nevada. It offers porphyry copper deposits, copper minerals, and oxide and sulfide ores.
The company was founded in 1989 and is based in Yerington, Nevada. Arimetco, Inc. is a prior subsidiary of Arimetco International, Inc. As of April 27, 2011, Arimetco, Inc. operates as a subsidiary of Quaterra Resources Inc..
Unison Transformer Services
Unison Transformers leased a portion of the property from Arimetco and operated for a few years in the 1990s to collect, crack and recycle transformers. Its operation left a discrete area contaminated with polychlorinated biphenyls (PCBs).
Quaterra Resources Inc
In 2011 Quaterra Resources Inc. purchased all the Yerington Mining District assets of the bankrupt Arimetco and could see production in 5 years.
Vancouver-based Quaterra Resources has completed its acquisition of properties around and including the old Anaconda copper mine, in Yerington, Nevada, and could get the project into production within five years, CEO Tom Patton said.
The initial focus at Yerington will be on completing an NI 43-101-compliant resource estimate, which should be accelerated by the fact that the company has access to historic data compiled by Anaconda, until the mine closed in 1978.
After that, the company will move onto the usual prefeasibility and feasibility study work before it can make a decision to go ahead with development. “But we think a five-year window is reasonable” to get to production, Patton said in an interview.
Ann Mason and the Revival of the Yerington Mining District
The company already owns the Macarthur project, about five miles north of Yerington, and has a preliminary economic assessment under way on developing oxide mineralisation there, while also drilling for primary sulphide deposits. “And the more we looked at Yerington proper, the more we liked it,” Patton commented.
Quaterra - Video Tour
Environmental Issues
The mine covers 6 square miles of land owned partly by the U.S. Bureau of Land Management. Atlantic Richfield acquired the property in 1977 from Anaconda Copper, which built the mine in 1941.
Previous owners left behind 90 million gallons of acidic solution that continues to threaten the groundwater. That's equivalent to the amount of liquid it would take to cover about 80 football fields, 10 feet deep.
Earle Dixon
In 2008 a U.S. Labor Department review panel upheld a whistleblower claim by ex-mine cleanup supervisor Earle Dixon, who said the BLM illegally fired him for speaking out about the risks in defiance of local politicians.
This 2004 photo shows the Yerington mine site, adjacent to the small farming town of Yerington, Nevada. Photograph: Cathleen Allison /AP
Farm near Anaconda Mine in Mason Valley
Anaconda, the former owner, produced 1.7 billion pounds of copper from 1952 to 1978 at the mine in the Mason Valley, an irrigated agricultural oasis in the otherwise largely barren high desert.
In this Nov. 30, 2004, file photo, an evaporation pond holds contaminated fluid and sediment at the former Anaconda copper mine near Yerington, Nev. The Environmental Protection Agency wants to add the abandoned site to its Superfund National Priority List.
(Debra Reid / AP)
The EPA determined that the uranium was produced as a byproduct of processing the copper and that the radioactive waste was initially dumped into dirt-bottomed ponds that leaked into the groundwater.
Artist rendition of toxic waste at Anaconda Mine
The mining wastes at the closed mining site have been investigated by the US Environmental Protection Agency. Since 2000, it has spent approximately $6 million addressing this issue and ARCO has spent $2.7 million to clean the site. In 2009 ARCO committed to spending $10.2 million for future and past cleanup work. Of the $10.2 million, $8 million was for future work and $2.2 million was to reimburse the EPA for past work completed. ARCO had reimbursed the EPA $2.7 million in 2008.
In 2013 Yerington residents were awarded up to a $19.5 million in settlement of a 2011 class action case that accused ARCO and BP America of leaking uranium, arsenic and other pollutants into soil and groundwater for decades and of covering up the extent of the contamination.
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