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HISTORY OF THE YERINGTON ANACONDA MINE

The discovery of gold in California in 1847 encouraged countless hundreds of prospective miners to head West. Many of them settled in western Nevada, sought out their fortunes in the Virginia City area, and then fanned out across the state. Copper was discovered in the Singatse Mountain Range on the western portion of the Mason Valley in 1865. Dozens of small mines, mainly operated with pick, shovel, wheel-barrow, and mule-driven carts, existed South and West of Yerington and to the northwestern portion of the Mason Valley into the first part of the 20th century. Total copper production of the mines to 1940 approximated $17,000,000.

From 1918 to 1920, the area now known as the Anaconda Mine operated under the names of "The Empire Mine," "The Empire Nevada Mine," and "The Nevada Empire Mine."  In 1941, International Smelting and Refining Company, a subsidiary of Anaconda Copper Company acquired the property. During the ensuing four years, a major exploration was conducted that confirmed the presence of approximately 60,000,000 tons of ore with copper content ranging from 0.9% to 0.95%, mostly oxidized as chrysocolla. No significant mining occurred during this period. [Back to Top]

In 1951, Anaconda took direct control of the site and began construction and installation of equipment for its mining operations. Anaconda actively mined the site from 1953 to 1978. During the period of 1953-65, Anaconda extracted copper oxide. Those ores were leached into sulfuric acid and precipitated onto old tin cans; the resulting copper slabs were shipped and smelted off site. From 1965 to closure in 1978, both copper oxide and copper sulfide ores were processed on site and shipped off site for smelting. Sulfur was mined at the Leviathan Mine in the mountains between Topaz and Gardnerville and transported to the Yerington Anaconda Mine for conversion into sulfuric acid. Copper oxide was leached from the ore with the sulfuric acid, which was then sent to extraction tanks and mixed with kerosene to extract the copper from the leach solution. A higher concentration of sulfuric acid removed the copper from the kerosene solution, and was then pumped into an electro-winning plant and plated out onto stainless steel sheets. That acid solution was recycled. Anaconda disposed of other mining wastes, including acid brines and tailings into unlined evaporation ponds at the site, (some ponds were lined with asphalt in the later years of this period). Unlined ditches were used to move these solutions from the processing areas to the evaporation ponds.

For U.S.E.P.A. evaluation, remediation and current status of the Leviathan Mine, click here.  (Note: You may not be able to directly return to this page.  Try using the back button on your browser).

Between 1953 and 1965, Anaconda removed some 803,224,674 pounds of copper ore with a value of $255,154,480. In June of 1972, contamination of domestic ground wells East of the mine site prompted investigation by Anaconda engineers, who determined that the unpalatable water was mixed with gasoline. Subsequent investigation revealed that corroded underground tanks from a private parcel and from a then nearby retail gas outlet were to blame. Local gossip attributes the corrosion to the presence of sulfuric acid migrating from the mine site.

In 1973, Nevada Bureau of Mines Bulletin 81 reported on radioactivity at the site. Also in 1976, M. J. Bright discussed the presence of uranium in evaporation ponds at the site. [Back to Top]

In 1976 or prior, Anaconda became aware of elevated levels of radionuclides, including uranium, in unlined ponds and solutions at the site. It was determined that the groundwater was contaminated with concentrations exceeding MCL and PRG by as much as a factor of 1,000. The concern came to light when Anaconda scientists noted that anticipated levels in the evaporation ponds were lower than predicted or expected, prompting the theory that the contaminants were leaching into the groundwater.

In 1977, Atlantic Richfield purchased a number of holdings from Anaconda, including the Yerington site as it was planning to close down. ARCO closed the site down on June 30, 1978, with no plans for reclamation of the site to pre-mining status. [Back to Top]

At the request of the Bureau of Land Management, the USGS and consultants conducted a hydro geological study from 1978 to 1979 to evaluate the possible impact to groundwater from mine site operations. The study concluded that groundwater below the site had been impacted by the acidic process solutions and metals that were disposed of at the site. Thorium and uranium were included among the list of contaminants found in the evaporation ponds. The study also determined that a groundwater plume of such materials had migrated at least 4,000 feet north of the site. USGS monitored waste fluids, monitoring wells, domestic and agricultural wells, and concluded that the plume included arsenic, cadmium, cobalt, copper, iron, lead, manganese, mercury, molybdenum, selenium, and zinc. The report said that deeper groundwater, 50 to 450 feet, suffered deteriorating quality during mine operations and that all hydrologic units in the area appeared to be connected. This report was released to the public in 1982.

In 1978, ARCO sold all of its holdings in the site, including the town-site of Weed Heights, to Don W. Tibbals. Tibbals subsequently leased portions of the mine site to other companies, such as Unison, a subsidiary of Union Carbide Company. Unison dismantled electrical transformers containing PCB's and removed copper and brass as salvage. It should be mentioned here that a substantial portion of the Yerington Anaconda Mine Site was and is currently owned by the United States Government, Department of Interior, Bureau of Land Management, (BLM).

1979 was an eventful year; an environmental study in April of that year showed Finger Pond #5 at almost 120 uR/hr. An internal July 26, 1979 memo discussed radiological concerns in the evaporative ponds, and also mentioned that copper reserves were "probably not sufficient to attract a buyer." Again in1979, the Yerington mine was entered into the Comprehensive Environmental Response Liability Information System, (CERCLIS) database.

From 1982 to 1988, Tibbals leased a portion of the site to Copper Tek. An acid leach and solvent extraction electro-winning process was again used to remove copper from tailings and left over ore. USGS also conducted a study using 12 monitoring wells; the study showed high levels of solids; many levels of MCL's were sharply exceeded, including arsenic, cadmium, copper, lead, chloride, iron, manganese, sulfate, and zinc. As a result of this and other information, the Nevada Division of Environmental Protection, (NDEP learned that the site was out of compliance with environmental laws. NDEP took charge as the lead regulatory agency at the site. NDEP then ordered Anaconda to monitor on-site groundwater and nearby domestic wells and ditches, in addition to solids in tailings and evaporation ponds.

In January 1983, Anaconda agreed to resample wells and a nearby drainage ditch. Elevated levels of sulfate, iron, manganese, and copper were confirmed in the Wabuska Drain. Also in 1983, Anaconda/ARCO conducted groundwater and surface water sampling in compliance with NDEP orders. In June of 1983, a group calling itself "Concerned Residents Opposed to Waste Dumpsites" or, "CROWDS," asked the USEPA to deal with "improper disposal" of sulfuric acid and associated wastes.

A 1984 study concluded that gross alpha, gross beta, and uranium exceeded "confidence levels" or existing standards in wells on the site and in the immediate vicinity. Radium 226 was much less pernicious, exceeding standards in only one well tested. Radium 228 was not tested.

Concerns about the off site migration of contaminants in the groundwater plume prompted NDEP to issue an Administrative Order to ARCO in October of 1985 that required installation of a system of wells and the construction of a pump-back system to pull water out of the plume to the north of the mine site and to pump it back into on-site evaporation ponds. It was anticipated that many of the contaminants would thereby be removed from the plume and that surface contaminants would be prohibited from reaching the Wabuska Drain. This theory did not bear out.

A December 1986 NDEP Order required Tibbals to shut down the operation of Copper Tek. In August of 1987, Pump-back Wells #1 and 5 were shut down, leaving seven others in operation. Suspicions arose that there may be leaks from the lined evaporation ponds.

1988 and 1989 were also important years. Tibbals sold a large portion of his land and unpatented mining claims to Arimetco in 1988. Operating under the name of Arizona Metals Company, Arimetco had leased a substantial portion of the site from Tibbals prior to this time and had conducted a closed-system extraction process. In 1989, Arimetco began to haul ore from its nearby MacArthur Pit for processing on the Anaconda site and it also acquired 90% of Copper Tek. After the purchase from Tibbals, who retained the town site of Weed Heights, Arimetco owned 49% of the mine site and the BLM owned the remaining 51%.

Records reflect that, during the period 1989 to 1999, Arimetco allowed an average of 700 gallons per day, and as much as 2,000 gallons per day, of pregnant solutions including metals and sulfuric acid solutions in the system and ponds to leak into the groundwater. During this same period, Arimetco performed quarterly groundwater monitoring and exceedances of MCL's of arsenic, chromium, sulfate, copper, lead, and mercury were reported. Many other violations were noted, (some required payments of penalties), during this time period.

In 1990, USEPA conducted a CERCLA evaluation of the site. A 1994 EPA Prioritization concluded that the site was eligible for inclusion on the NPL, (National Priorities Listing). The NPL is the source list from which Superfund Sites are selected. However, the site was not included on the NPL. Also in 1994, Arimetco was directed to begin a health study. (Records of such a health study, if ever conducted, are not available to this website as of December 23, 2004).

In November of 1991, Holcorp, a subsidiary of Arimetco, acquired MacArthur Mining and Processing. In August of 1993, the name on the mining operations permit was changed from Arimetco Inc/Copper Tek Corp. to Arimetco International Inc.

Arimetco was required, in June of 1995, to increase Mega Pond monitoring and to prepare a hydro geological study of the area. In December of 1996, mining operations ceased at the MacArthur Pit. In January of 1997, Arimetco filed for protection under Chapter XI of the U.S. Bankruptcy Code; the company continued operations at the Yerington Anaconda site. A series of violation notices were issued between 1997 and 2000 involving groundwater, air, and soil issues at the site.

Also in January of 1997, an unexpected warm mountain rain in the Sierras to the East of Mason Valley caused heavy snow-melt and resulting extreme flooding of the East Walker River, which runs immediately adjacent to and east of the Yerington Anaconda Mine Site. In an effort to alleviate the flooding of the West Yerington area, some water was diverted to the Yerington Pit. It is not known whether or not any contaminants from the pit, the mine's evaporation ponds, or other operating areas of the mine mixed with waters from the East Walker River. The EWR continues through the Mason Valley and, eventually, into Weber Reservoir and downstream Walker Lake.

In May of 1999, the National Applied Resource Sciences Center concluded a preliminary geophysical survey of the groundwater plume for the BLM. The resulting report confirmed that the plume extended at least to the southern portion of the Sunset Hills residential area in the shallow aquifers. It further suggested that the pump-back system remaining in place at the time might not be doing what it was engineered for. The plume "is the result of disposal of sludge and brine by-products of copper mining and milling operations which occurred from 1953 to 1978." According to the study, brines contained elevated concentrations of arsenic, beryllium, boron, cadmium, chloride, chromium, cobalt, copper, iron, lead, magnesium, manganese, mercury, molybdenum, nickel, specific conductance, sodium, sulfates, uranium and zinc. The study further suggested an impact to intermediate aquifers at down-gradient locations. Additional pump-back wells were installed by ARCO in an effort to contain the plume.

A different 1999 hydropunch study of shallow down-gradient aquifers was conducted by ARCO and confirmed the presence of elevated levels of arsenic, cadmium, and lead. In November of that year and under direction from the USEPA, NDEP sampled 15 public and private drinking water wells in the vicinity plus previously installed monitoring wells. Near the intersections of Luzier Lane and Locust Street, (immediately northwest of the mine site), arsenic between 30 and 60 ug/l was discovered.

In October of 1999, a joint public meeting conducted by USEPA, BLM and NDEP was held at the gymnasium of the Yerington Paiute Tribe to discuss groundwater plume concerns and the proposed November well samplings. A meeting announcement noted that the "Yerington Paiute Tribe, the Walker River Paiute Tribe, and the residents of the Sunset Hills subdivision," had "concerns" that prompted the investigation. [Back to Top]

In January of 2000, faced with a multitude of infractions, fines, depreciating copper values and a rapidly depleting source of economical ore content, environmental problems and low copper prices, Arimetco abruptly closed the Yerington Anaconda Mine Site and left the premises. Behind, they also left mining equipment, trucks, and over 90,000,000 gallons of pregnant solutions, including heavy metals and sulfuric acids, in the pipes, system and ponds. Mining companies are required to post bonds to assure that the operations they leave behind can be closed in an environmentally safe manner. As NDEP took charge of the site, the bonds remaining on the Yerington site consisted of $75,000 in cash plus corporate guarantees…guarantees on a corporation that had filed bankruptcy three years earlier. Estimates for site remediation range as high as $275,000,000.

In February of 2000, the Department of Interior, (DOI), and the United States Environmental Protection Agency, (USEPA or EPA), met without NDEP to determine Nevada State policy at the site and the latest sampling results. In May, EPA commented that the results of the 1999 water investigation by NDEP had not been posted. Fugitive red dust was also cited as a problem. A subsurface geophysical survey was conducted, utilizing technologies that detect variations in conductivity and resistivity. The result concluded that a significant portion of land immediately to the North of the evaporation ponds, included a shallow aquifer plume at least 1 mile to the north of that location and that the intermediate aquifers had been adversely impacted. Downward migration of the plume was also hinted at, along with the opinion that clay barriers between aquifers either did not exist, or that they had been penetrated. The study mentioned that the plume might also be in the deeper aquifers, which were not investigated at that time. Elevated levels of uranium and beryllium in the brine were detected.

Late in 2000, an Expanded Site Investigation, (ESI), was conducted by EPA, Region IX. To this date, the scoring of that investigation has not been publicly released. However, it became public knowledge that, whatever the score was, it exceeded 28.5, which is the minimum standard for listing on the NPL. The ESI also determined connection of aquifers and the release to groundwater of heavy metal contaminants from the mine site. The study, conducted by Ecology and Environmental, Inc, stated that "A release to groundwater of arsenic, beryllium, cadmium, chromium, lead, mercury and selenium can be established from the Anaconda site. A release to the groundwater is established when a hazardous substance is detected in a down gradient groundwater sample and not detected in a background sample."

Although the Yerington Paiute Tribe had, through USEPA, requested listing of the site on the NPL, Nevada State Governor Guinn declined to go along in January of 2001. Political protocols give the state governor the right of objection and refusal. The USEPA could proceed to list the site on the NPL and to declare it to be a Superfund Site but, even so, the state would have at least 18 months of built-in time to avoid such a listing. It should be mentioned at this point that mining was, at that time, the number-two industry in Nevada, second only to gaming. Nevada is rich in many valuable minerals, and many factions in the industry and in political circles felt the need to protect Nevada from a "black eye" that a Superfund listing might bring. Guinn said that the request for NPL listing was a result of issues voiced by the Yerington Paiute Tribe and the downstream Walker River Paiute Tribe and "may result in unnecessary adverse social and economic impacts to surrounding residents of Lyon County without any concurrent human health or environmental benefits."

In February 2002, temporary covering of two iron bleed tailings areas was accomplished to prevent off-site migration of fugitive dust.

On March 28, 2002, a Memorandum of Understanding, (MOU), was signed between NDEP, BLM and EPA. It was the first such agreement of its type in mining cleanup history. This MOU continued with NDEP at the lead, but also defined how the agencies would work together in the oversight of the YAM. It defined the Review Process and the Dispute Resolution Process. Negotiations were then entered into with ARCO to determine the language of an Administrative Order of Consent, (AOC). The AOC would basically determine the relationship between ARCO and agencies of the MOU. ARCO, by virtue of the fact that other potential Principal Responsible Parties, (PRP's) were not financially viable, became the lead PRP responsible for mine-site remediation; its legal remedies would be against the other PRP's.

The Yerington Technical Work Group, (YTWG), was established in May of 2002. This group was designed to collect data and other information and to define the work to be performed by ARCO at the mine site. The work to be performed included various work plans, which were to be designed by the YTWG and considered by ARCO, with a negotiation process involved. With the three agencies also involved, this process proved to be lengthy and cumbersome.

October of 2002, under sampling directed by EPA, brought news of elevated levels of sulfuric acid, beryllium, cadmium, chromium, lead, mercury, and selenium in on-site ponds, as well as high levels of arsenic, beryllium, cadmium, chromium, lead and mercury in tailings. Immediately north of Luzier Lane on the north side of the site, leachite salts included elevated levels of arsenic, beryllium, chromium, and mercury.

In February of 2003, NDEP conducted its first public meeting regarding the site since 1999. From the day of closure in 2000 to March of 2003, millions of gallons of pregnant solutions remained in the operating system. Other chemicals were stored in drums and other containers on the site. SRK Consulting, under contract with NDEP, had been pumping and spraying solutions into the air and onto tailings in an ongoing and somewhat successful effort to reduce the amount of fluids that were flowing through the site. In March, electro-winning fluids and the drums were finally removed.

The Walker River Paiute Tribe and the Yerington Paiute Tribe voiced growing concerns about site remediation from 2000 through the end of 2004. One of their major concerns was the possibility that uranium may be in groundwater flowing to the north of the abandoned site. ARCO and members of the MOU were of the publicly stated opinion that uranium was not present in sufficient quantities to pose any problems at the site or threats to groundwater. In the summer of 2003, BLM researchers discovered documents stored at the University of Wyoming in Laramie that discussed the possibilities of commercial production of yellowcake uranium at the Anaconda site in 1976.

In the fall of 2003, samples were taken at evaporation ponds on the site that confirmed the presence of uranium in significant amounts. In October of 2003, a spokeswoman for the US Fish and Wildlife Service, (USFWS), disclosed that ARCO's position over the years had been that uranium was not an issue at the site and that they were not going to test for it. The tribes pushed for sampling of groundwater monitoring wells, site pump-back wells, and off-site domestic wells for the presence of uranium. NDEP conducted its 3rd open public meeting to discuss the discoveries. NDEP subsequently requested that ARCO sample for the presence of uranium, radium 226 and radium 228. In December of 2003, wells were tested for the presence of uranium for the first time.

March of 2004 brought confirmation from testing laboratories that uranium in amounts exceeding the USEPA drinking water standard of 30 ppb was present in off-site domestic wells. Another public meeting was conducted by NDEP to discuss the findings, and ARCO offered to provide bottled water to any resident whose well had tested at 25 ppb or above. Monthly follow-up tests were scheduled and the public was encouraged to cooperate with ARCO and NDEP by having their wells added to the sampling lists.

The Yerington Paiute Tribe had long been requesting that the mine site be included on the NPL and granted Superfund status.  The City of Yerington and Lyon County officials had been at odds with the YPT and were firm in their position that a Superfund declaration would cause irreparable harm to the residents and economy of the Mason Valley. In response to those fears, the Yerington Paiute Tribe held two closed meetings with the Bureau of Indian Affairs, Walker River Paiute Tribe, USEPA, BLM, NDEP, Congressional representatives from U.S. Senators Harry Reid and John Ensign offices, and the Inter-Tribal Council of Nevada in April and June of 2004. A concerted effort was made to resolve the growing political and bureaucratic issues at the mine site without a Superfund declaration; no viable alternatives were discovered.

In June of 2004, BLM took the position that a Healthy and Safety Plan, (HASP), needed to be designed and in place at the mine site to protect workers from the dangers of radiation and other unknown hazards. BLM conducted soil samplings in and immediately adjacent to the process areas and discovered that dangerous levels of gross alpha, gross beta, uranium, radium 226 and 228, as well as thorium existed in some "hot spots" of the process area. Subsequent shallow soil samplings at over 100 locations confirmed increased levels of radioactivity that "could be a hazard to workers on the site."

ARCO publicly attacked BLM in August 0f 2004, asserting that BLM had a conflict of interest at the mine site in its dual role as part land owner and as a member of the MOU, and suggesting that it should consider removing itself from oversight roles. The YPT once again asked that Nevada drop its resistance to a NPL listing, and Nevada's Governor Kenny Guinn publicly indicated that he might reconsider his opposition to the idea.

In September of 2004, 57 of 98 domestic wells tested exceeded MCL's for gross alpha and 25 or less met MCL's for uranium; this information was not released until December. The YPT sent out a press release in which it suggested that a compromise with all parties concerned should be considered, in which USEPA would be named the "Lead Agency" of the MOU instead of NDEP, and that EPA would then assure cleanup of the mine site to Superfund standards, (CERCLA 106), without formally naming the site "Superfund." In October, the City, County, and YPT agreed to the proposed compromise and sent a letter to Governor Guinn asking him to request that EPA take the "lead" but not to place the mine site on the NPL. Guinn replied that he would take the proposal, letter and agreement into consideration.

In December of 2004, NDEP began releasing data from its September 2004 quarterly sampling that showed exceedances of uranium and gross alpha standards in domestic wells north of the YAM, including wells that supply homes and offices on the Yerington Paiute Reservation. December 10 produced a letter from NDEP to Gov. Guinn asking that he request EPA to take the lead position regarding site oversight and cleanup.  On the same day, Guinn concurred. EPA responded affirmatively to the request on December 15th. On December 20th, the news became public and ARCO agreed to provide the YPT reservation with bottled water.  

In late-fall of 2004, on-site work by ARCO and Brown & Caldwell began to assess radiological hazards in and around the processing areas.  Soil, water and air samples have been collected to further analyze radiological concerns first discovered by BLM in the summer of 2004.  As of mid-February 2005, this portion of the lengthy evaluation and cleanup of the site was approximately 1/3 complete. 

In January and February of 2005, air monitors were installed on the mine site and EPA announced a series of steps to be taken in the short-term, including enhancement of site security and the installation of off-site scientific ground monitoring wells that will more adequately define the hydrology and contaminants north toward the Yerington Paiute Reservation.  ATSDR also confirmed that it had received a proper request from the Yerington Paiute Tribe to assess health risks in the area and that this study could begin in April.  

February and March of 2005 found workers taking additional soil samples on the site.  In the process, several areas were roped off because levels of radioactivity were too high for workers to spend any significant time in.  A decision is to be made at a later date as to how to properly assess those areas for radiological and chemical contamination. 

April 1, 2005 USEPA announces it has issued an Unilateral Administrative Order against ARCo requiring cleanup of the mine, additional securing of the site, identification of contaminated areas, and air monitoring. 

In late 2004 and early 2005, the CDC and ATSDR have backed away from original conclusions and tungsten is now again considered to be a suspect.  However, there are no studies that suggest that tungsten was, or is, present in any significant amounts on the Yerington Mine Site.  For ATSDR's assessment and statement on tungsten in the environment, go to  http://www.atsdr.cdc.gov/toxprofiles/phs186.html.  (Note: You will not be able to directly return to yamsite.info from that link.)  You can also obtain more information about tungsten and the Yerington Mine on the "Minerals, Metals & Chemicals" page of this website.

August 2005 found Dan Ferriter, Environmental Manager of the Yerington Anaconda Mine Site for BP/ARCo, being replaced by David McCarthy from BP/ARCo's Butte, Montana operations.  Ferriter moved to  another position within the company in the Chicago area.  In the BP/ARCO hierarchy of things, McCarthy was previously responsible for technical oversight and response to the former tri-lateral regulatory team led by NDEP and consisting of NDEP, BLM, and USEPA.  McCarthy promptly put "on hold" its previously promised security fencing around the southern portion of the Yerington Anaconda Mine site, leaving that area open for potential trespassers and unwary children.   

Fall 2005:  Although the sampling of domestic wells in 2004 and 2005 showed increasing levels of uranium in many wells, BP/ARCO stopped sampling wells at or above the 25mcl level in the fall of 2005.  That decision was based on the fact that BP/ARCO had agreed to supply bottled water for domestic purposes to owners of those wellls.  At the time of that decision, the company stated that it would continue testing of wells that were below the 25mcl limit in case there were any increases in uranium levels that would warrant more owners receiving bottled water. 

Roy Thun was named by BP/ARCo to replace David McCarthy as Project Manager. 

Quaterra Resources Inc of Canada announced in October 2006 that it had taken options on 66 unpatented mining claims at the MacArthur Mine Site near Yerington.  The site was operated by Arimetco between 1995 and 2000 in conjunction with the Yerington Anaconda Mine. 

EPA, through an emergency removal Action Memorandum dated December 7, 2005, asked ARCo to cooperate in addressing PCB containing electrical equipment remaining on the site, and provide interim controls on fugitive dust sources at the site.  ARCo refused to do so and EPA decided to conduct the work itself, using EPA funds. Site security through improved fencing, long-promised by BP/ARCo, continued to be "evaluated and discussed." 

In January of 2006, BP/ARCO decided it would no longer test any domestic well that had been previously tested.  The new position was that uranium levels were not changing enough to warrant any further testing.  EPA, through an emergency removal Action Memorandum dated December 7, 2005, asked ARCo to cooperate in addressing PCB containing electrical equipment remaining on the site, and to provide interim controls on fugitive dust sources at the site.  ARCo declined to comply.   EPA responded by announcing that it would conduct the work itself and bill ARCo for the costs.