Anaconda Copper Mine, a pictorial primer

by Brian Bahouth

If you visit Yerington Nevada you cannot miss the mountains of brown toxic mine tailings from the defunct Anaconda Copper Mine. Nothing grows on the moon-like landscape with a footprint larger than downtown Yerington. Copper miners blasted and dug into the earth and delivered 13,000 tons of ore to the crushers six days a week from June 1952 to June 1978. Today, a desert of toxic tailings, heap leach pads, abandoned buildings, machinery and unlined settling pools surround a massive pit lake. The quarry is one mile long, a half mile wide and 810 feet deep. Four hundred and fifty feet of the terraced pit is underwater. In all, 1,744,237,000 pounds of copper was pulled from the permanent hole.

The Anaconda Mine pit lake – image – Brian Bahouth

The surface and visual impact of the mine is only part of the story. The process used to mine and extract copper from ore has left a large and yet to be fully characterized plume of toxins in the regional water table. People have been advised not to consume the well water or give it to pets or livestock for many years. Scores of households continue to receive free bottled, though recently the City of Yerington completed extensions of their domestic water system, so fewer are now eligible for the bottled water program.

Map – Nevada Division of Environmental Protection


The economic facts from the sign in a tire at the pit lake overlook are noteworthy for the amount of net proceeds tax paid on the lode.

Market value for the entire duration of the $765,504,000.00
Net proceeds tax $7,523,000
Profit from net proceeds $212,979,000.00

A sign in a tire at the Anaconda Mine pit lake overlook – image Brian Bahouth
A sign in a tire at the Anaconda Mine pit lake overlook – image Brian Bahouth

Why the Anaconda mine is not a Superfund site

The Environmental Protection Agency (EPA) had done a lot of site characterization work and in December of 2015 EPA sent a letter to then Governor Sandoval to advise the executive that the agency planned to list the site on the National Priorities List as part the Comprehensive Environmental Response and Liability Act or CERCLA. The letter requested the state’s position on listing the mine as a Superfund site.

From an EPA document describing the transfer of remedial authority.

After initial discussions in December 2016 and January 2017 between EPA, the Nevada Division of Environmental Protection (NDEP),the Bureau of Land Management (BLM), and Atlantic Richfield Company (ARC), and after meeting with governmental representatives, which included but was not limited to, the Yerington Paiute Tribe, the Walker River Paiute Tribe, Lyon County and City of Yerington, EPA made a decision in February 2017 to postpone listing of the Site on the NPL while all parties evaluated deferral options for a private funding solution. On April 19, 2017, EPA sent a letter to NDEP (Criteria Letter) specifying the criteria that would be considered by EPA in determining whether a deferral of Site cleanup to private funding under NDEP oversight is appropriate. Between February and June 2017, NDEP and ARC developed a proposal for deferral of the Site from NPL listing. NDEP conducted outreach with community stakeholders, including Lyon County, the City of Yerington, the Yerington Paiute Tribe, the Walker River Paiute Tribe, and interested community members. NDEP and ARC are entering into an Interim Administrative Settlement Agreement and Order on Consent (IAOC) for performance of certain response actions at the Site. Once fully executed, the IAOC will be attached to this Deferral Agreement as Attachment D. On July 31, 2017, NDEP formally requested EPA deferral of the Site under CERCLA § 105(h).

On February 5 of 2018, EPA Administrator Scott Pruitt toured the Anaconda Copper Mine and signed a Deferral Agreement with the State of Nevada. The Nevada Division of Environmental Protection is now the lead agency regarding site remediation.

The Mining Process

Only a small percentage of the rock removed contains copper, so the rock must be crushed and treated. There are two primary types of copper ore, copper oxide and copper sulfide. According to Anaconda, the company mined 103,834,000 tons of copper oxide ore and 58,589,000 tons of sulfide ore. According to the Copper Development Association, copper mines are only developed when at least 10 pounds of copper can be removed from one ton of rock.

Copper oxide ore is crushed and treated with sulfuric acid in big vats. Mel Diehl’s dad was a blasting and surveying supervisor at the mine, and Mel worked as a crane operator and maintenance man for roughly three years.

The brown cement blocks that form a horizontal line through the center of this image are what used to be ore processing vats where crushed copper oxide ore and sulfuric acid would be mixed to separate the copper from the rock – image – Brian Bahouth

“Once we ran the sulfuric acid over the oxide ore, it would come down to me in a liquid form and had the copper with the sulfuric acid and they’d put it over tin cans,” Mel Diehl said when describing the process and his role in it. “The sulfuric acid would eat the tin cans and leave the copper there. They had a bunch of different cement troughs. You put plugs in and raise up the level of the acid and then switch to another one once one was full. You dig it out with clam-shell bucket and wash it through a trommel. Then you pick it up out of the sump and take it to the hot plates. That’s where they’d heat it up and dry it out and they’d ship it with trucks out to Wabuska to be shipped to Montana.”

The rubber-lined pit in this image was installed after a nearby restaurant well was severely contaminated with runoff from the mine. This collection trough intercepts the bad water and enables it to evaporate. If you look closely at the tailings pile, you can see the black plastic pipes through which sulfuric acid solution was dripped over the “heap” of crushed ore. The copper was then extracted from the pregnant acid solution using chemical means. Note the purple, inflatable dancing caricature in the lower left hand corner of the image intended to scare off birds that might land in the water – image – Brian Bahouth
The Anaconda Mine looms over Yerington and the the Mason Valley. To the east of the mine, huge plantings of onions and other crops mark big green squares in the landscape. Farmers pump water from deep wells to irrigate their fields. Officials have yet to determine the mine’s full impact on adjacent agricultural activity and if agricultural pumping helps spread contamination. High levels of elements like uranium can be found naturally in the local groundwater, but determining if elevated uranium levels, for instance, are a result of the mine is the challenge. Nevada Capital News has well testing results from a well nearly 8 miles east of the mine that indicate severely elevated uranium levels  – image – Brian Bahouth

On the western side of the mine site is where some of the more troubling pollution has occurred. Mel Diehl described the area in the image below, as “the dump.”

Mel Diehl referred to this part of the site as the dump. Diehl said the dump warrants special remedial attention – image – Brian Bahouth

“I didn’t know about the uranium and everything in it,” Diehl said. “I was never told about it when I worked up there. I was told by my father afterwards. He was a boss up there. He told me he used to run around with a Geiger counter and stuff and check in the pit. He was a blasting foreman and a surveying foreman. When they’d come across some hot uranium, they send it to the waste dump and just cover it up.”

On the northern edge of the site these unlined settling pools have had a direct impact on groundwater quality that is still being characterized – image – Brian Bahouth
The company town of Weed Heights was named after Clyde E. Weed, chairman of the Anaconda board of directors. Today the neighborhood overlooking the mine is partly occupied and includes an RV park and art space in what was once a commissary and bowling alley – image – Brian Bahouth

Weed Heights is roughly half occupied. Every one of the neatly arrayed houses has a good view of the mine. Some houses are tidy while others are abandoned. Behind the car is a house on the western edge of the neighborhood – image – Brian Bahouth
Large sections of the tailings pile on the western edge of the site show large amounts of the tailings material has been removed. Mel Diehl said he has hauled a lot of the material himself. Diehl said the crushed rock once bathed in sulfuric acid makes excellent road bed and is especially desirable because it prevents weeds from growing on shoulders of roads. Diehl said the material is spread far and wide across dirt roads, parking areas and even areas around schools. Nevada Capital News is working to fact-check Diel’s claim, but a significant portion of the tailings pile in this image appears to have been taken away – image – Brian Bahouth
Image – Brian Bahouth
Image – Brian Bahouth
Entering Yerington from the north on route 95, the massive tailings pile is adjacent to active agriculture – image Brian Bahouth
The tanks on top of this mountain of mine waste likely contained sulfuric acid – image – Brian Bahouth



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