Pacific Southwest, Region 9: Superfund
Serving Arizona, California, Hawaii, Nevada, the Pacific Islands, and Tribal Nations
EPA #: NVD083917252
Congressional District: 2
Other Names: YERINGTON MINE, ANACONDA COPPER COMPANY MINE
Technical Documents currently under review are available at:
SharePoint Site -
On this page
Description and History
NPL Listing History
Is the Anaconda Mine a "Superfund" site?
The quick answer is "yes"; however, it is not on the National Priority List (NPL) of sites.
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.
Contaminants and Risks
- Surface Water
- Soil and Sludges
The threats EPA is investigating at the site include contaminated groundwater and contaminated fugitive dust that could impact human health and surface water. Additional concerns include on-site contaminated surface water (which could impact wildlife), and physical hazards associated with abandoned buildings, debris, and unstable materials such as the waste rock, heap leach and tailings piles, and pit lake slopes.
Primary Contaminants of Potential Concern*:
Metals-Aluminum, Arsenic, Beryllium, Boron, Cadmium, Chromium, Copper, Iron, Lead, Manganese, Mercury, Molybdenum, Nickel, Selenium, Uranium, Zinc
Radioisotopes -Uranium-234, Uranium-235, Uranium-238, Thorium-230, Thorium-232, Radium-226, Radium-228
Others-Chloride, Sulfate, low pH (acidic) conditions, particulate matter
* This list may not be complete or comprehensive. EPA will establish an official list of contaminants of concern for each Operable Unit after remedial investigation activities, including a risk assessment, have been completed.
Groundwater: In the late 1970’s, the U.S. Geological Survey (USGS) described a groundwater plume of arsenic, cadmium, cobalt, copper, iron, lead, manganese, mercury, molybdenum, selenium, and zinc below the site and migrating northward. The shallow aquifer is contaminated with acidic process waters and metals potentially from the process areas, evaporation ponds, and leaking heap leach pads and tailings piles. Intermediate and deep aquifers may be degraded, and the aquifers may be interconnected.
Also, research conducted by the BLM in 2003 showed knowledge of technologically enhanced naturally occurring uranium (TENORM) on the site. Testing in 2004 by ARC confirmed the presence of uranium in off-site domestic wells located north and west of the mine and in soil samples from the process area. The uranium in the off-site domestic wells may be due to either contaminant migration from the site or due to naturally occurring uranium in the area. A series of groundwater monitoring wells have been installed to better determine the source of the uranium.
During EPA's September 2009 public meeting in Yerington, Nevada, and in subsequent public meetings, EPA provided information on groundwater conditions near the former mine site. Our current information shows that there is shallow groundwater contamination from the mine near the northern boundary of the property. This contamination does not impact the City of Yerington Water System, which is tested regularly and is in compliance with federal drinking water standards. Domestic wells north and west of the mine site that exceed the federal drinking water standard for uranium are offered bottled water by ARC. EPA is planning investigations to further differentiate mine-related contamination from naturally occurring contamination. We will continue to share findings from our ongoing groundwater studies.
Fugitive Dust: High wind events combined with a semi-arid environment contribute to occasional erosion of the mine tailings piles, creating potentially contaminated fugitive dust blowing off of the site. In 2004, ARC installed ambient air monitoring equipment to evaluate fugitive dust concerns. ARC sampled particulate matter with an aerodynamic diameter less than 10 microns (PM10), total suspended particulates (TSP), metals, and radionuclides at the site perimeter from 2005 to 2008. The air monitoring program evaluated air quality impacts from fugitive dust using EPA-approved sampling methods. In an effort to reduce fugitive dust from blowing off of the site, EPA capped and sealed approximately 125 acres of potentially contaminated soil in 2006. During the capping, additional air monitoring was conducted to ensure that capping procedures did not produce additional fugitive dust. In early 2007, ARC upgraded the ambient air monitoring equipment to better characterize the high wind events and associated air pollutant concentrations. The air monitoring program was temporarily discontinued on April 1, 2008 and ARC has submitted the results to EPA for review. ARC conducted a baseline human health risk assessment in 2010 to determine, under current conditions, how potential for adverse health effects from the inhalation of dust at the boundary of the mine site compares to regulatory guidelines and to evaluate risk associated with natural background. (The report can be found in the "Document and Reports" section below.)
In April 2009, ARC signed an agreement with EPA to minimize the migration of dust from the lined and unlined evaporation ponds. ARC submitted a Dust Suppression Plan to EPA, proposing the application of a dust suppressant to the ponds to reduce the emission of dust. EPA approved the Dust Suppression Plan, Revision 1, in June 2011. ARC completed the application of the dust suppressant to an area within the Process Area to minimize the emission of dust from the area where a removal action was completed in late 2010. In addition, ARC began applying the dust suppressant to the unlined evaporation pond in July 2011. The dust suppression work will be completed by the end of 2011. The dust suppressant application to the lined and unlined evaporation ponds is a temporary measure being implemented until EPA and ARC agree on an interim cover design for these areas.
Surface Water: There are several areas of surface water on the site that could pose a threat to wildlife and potentially groundwater resources. These areas include the Pit Lake, four Arimetco heap leach drainage fluids collection ponds, three ARC pumpback collection ponds, water collecting in low lying areas of Anaconda lined and unlined evaporation ponds, and parts of the sulfide tailings area during rain events. These areas are primarily contaminated with heavy metals and low pH levels. ARC completed initial characterization of the lined and unlined evaporation ponds in October 2008 and will take interim measures to provide a cover for these areas as described above. ARC has also been monitoring wildlife since March 2007 and operating bird deterrent systems at the site's evaporation ponds and the Arimetco ponds since September 2008. Remaining areas are planned to be investigated by ARC under an EPA Order.
Who is Involved
The U.S. EPA has regulatory lead of the site and is working with other federal agencies as well as state agencies and potentially responsible parties. Please see Site Contacts below for contact information.
Investigation and Cleanup Activities
EPA has established eight Operable Units (OUs) to address the investigation and cleanup of the various components of the site: Site-Wide Groundwater (OU-1), Pit Lake (OU-2), Process Areas (OU-3), Evaporation Ponds/Sulfide Tailings (OU-4), Waste Rock Areas (OU-5), Oxide Tailings (OU-6), Wabuska Drain (OU-7), and Arimetco (OU-8).
Each of these OUs will have their own investigation and cleanup plans. The cleanup approaches for the various hazards at the site will be determined after these investigations have been completed and potential risks have been evaluated. In the interim, EPA will determine whether emergency removals or other interim actions are warranted to mitigate immediate hazards.
Prior to 2000
Since 1978, evidence has shown that the groundwater beneath the site has been impacted by mining activities. In the late 1970s and early 1980s, initial studies by NDEP found that tailing streams contained arsenic, mercury, lead, copper, zinc, and chromium. The studies also discovered that contamination from the mining, milling, and metal salvaging operations had migrated into the groundwater forming a contaminant plume.
NDEP issued a Finding of Violation to ARC for the groundwater pollution in 1982. A second Violation was issued in 1985 and required the installation and monitoring of an interception “pumpback” well system designed to contain the groundwater contamination plume. ARC initially installed five pumpback wells on the northern end of the site from 1985 to 1986. An additional six pumpback wells were installed in 1998. The eleven wells pump contaminated water from the plume into three lined evaporation ponds located on the northern portion of the site. The purpose of this system is to prevent shallow groundwater from contaminating private and municipal drinking water wells in Yerington and the local community. The system was meant to also stop contamination from reaching the Walker River via the Wabuska Drain.
In the late 1990s, local residents, including the Yerington Paiute Tribe, collected water samples from domestic and tribal wells located away from the site. In two of the locations sampled, they found arsenic at levels higher than the acceptable drinking water standard. The discovery of elevated arsenic levels led NDEP and EPA to conduct an Expanded Site Investigation, which was completed in October 2000. Based on the results of that investigation, EPA and NDEP determined that the extent of contamination and the potential human health risks at the site warranted a more comprehensive investigation and cleanup.
NDEP assumed maintenance of the site in 2000 and performed emergency removals at the site from 2001 until 2003.
EPA considered proposing the site for placement on the NPL in 2001; however, the State of Nevada objected since the State was working on the site under a voluntary agreement with ARC. EPA agreed to defer the process for listing the site at that time to allow the State to continue that approach, while reserving the right to reconsider proposed listing on the NPL in the future if the State's approach did not prove effective.
EPA negotiated a Scope of Work and Memorandum of Understanding with NDEP and BLM to cover further site investigations and cleanup activities. In this agreement, NDEP retained lead responsibility and EPA provided oversight. In late 2004, NDEP requested that EPA take the regulatory lead at the site due to the increased complexity of contaminants at the site, such as radioactive contamination.
EPA issued a Unilateral Administrative Order (UAO) for Initial Response Actions to ARC in March 2005. The Order required ARC to: improve site security, update the health and safety plan for on-site workers, implement air monitoring, conduct a radiation survey on and off the site, continue operating the groundwater pumpback well system and Arimetco heap leach fluids management system, prepare Operations and Maintenance (O&M) Plans, continue ongoing investigations of the Process Areas, sample domestic wells for contaminants, supply bottled water to residents, and implement a groundwater study.
ARC conducted air quality monitoring from January 2005 to April 2008, and submitted an Air Quality Monitoring Program Data Summary Report and a Baseline Human Health Assessment Work Plan for the Inhalation Pathway. ARC completed the Baseline Human Health Risk Assessment for the Inhalation Pathway in 2011. (See Fugitive Dust under the Threats and Contaminants section above.)
In early 2007, ARC modified the ambient air monitoring equipment, and also completed installation of approximately 3.5 miles of new fencing, new gates, and new signage, repairs of 10.7 miles of existing fencing, to prevent unauthorized access to the site. In summer 2007, ARC collected soil samples off-site to establish background levels of contamination in the area soils and completed a Background Soils Data Summary Report in March 2009.
In 2006, EPA performed emergency response actions to: mitigate dust from blowing off the site, remove PCB containing transformers, and repair and upgrade leaking Arimetco fluid collection ponds. In late 2006, ARC proposed to conduct a removal of radiological contamination from the Process Area in order to remove access restrictions for site workers in a 30 square ft. area of the 230-acre Process Area. To avoid repeated mobilizations, and ensure a more thorough investigation of the radiological conditions at the site prior to removal actions, EPA requested the scope of the removal action be based on a complete assessment of the area. ARC declined; therefore, EPA conducted a radiological removal assessment in the Process Area during the summer of 2007, and completed a report of the survey in August 2008. EPA completed an agreement with ARC in April 2009 for ARC to conduct additional characterization and removal of the radiological materials in the Process Area that pose a threat to on-site workers; ARC removed over 6,000 tons of soil contaminated with radiological materials in late 2010.
In the summer of 2007, EPA conducted assessments of the Arimetco heap leach fluids management system ponds to determine the scope of additional removals that may be needed, and an investigation of the Arimetco Heap Leach Pads. In the fall of 2007, EPA conducted a permanent removal of another leaking Arimetco pond and recommends additional removals as funding becomes available. EPA conducted additional removals of inactive leach ponds, and repairs of active ponds in September and October 2008. This included removal of soil contaminated with kerosene at the Arimetco processing facilities and bioremediation treatment of the soil.
EPA and ARC signed an agreement in April 2009 requiring an update to the Pumpback Well System and Evaporation Ponds O&M Manual, and the completion of the following interim removal projects: evaporation ponds capping, removal of radiological materials in the process areas, removal of transite/asbestos pipe, and abatement of electrical hazards. EPA approved work plans for the removal of radiological materials in the process areas, removal of transite/asbestos containing pipe, and abatement of electrical hazards. All three removal actions were completed in 2010. In addition, EPA approved a work plan for capping of the thumb pond and a small area of the Process Area (referred to as Sub-Area A); ARC completed the capping project in 2010. ARC initiated dust suppression activities in 2011 by applying a dust suppressant to a portion of the Process Area and will complete the application of the dust suppressant to the lined and unlined evaporation ponds by late 2011. (See Fugitive Dust under the Threats and Contaminants section above.)
In 2010, EPA completed the following short-term response actions: removal of asbestos from the Anaconda Mine office and off-site disposal of the asbestos containing material; demolition of the mine office and on-site landfilling of the demolition debris; radiological screening and off-site disposal of more than 300 large truck tires; repair of the heap leach fluids management system; and removal of small containers of hazardous waste left on-site. EPA also performed an evaporation pond pilot test to assess enhanced evaporation methods.
EPA issued a second Order to ARC in January 2007 requiring remedial investigations and feasibility studies of the Anaconda portions of the site. EPA has divided the site into manageable operable units (OUs) that will each require their own investigation and cleanup strategy: Site-Wide Groundwater (OU-1), Pit Lake (OU-2), Process Areas (OU-3), Evaporation Ponds/Sulfide Tailings (OU-4), Waste Rock Areas (OU-5), Oxide Tailings (OU-6), and Wabuska Drain (OU-7). EPA is concurrently conducting a “fund-lead” remedial investigation and feasibility study for the Arimetco operated portions of the site, designated as OU-8.
Under the 2007 EPA Order, ARC has submitted the following documents to EPA: Draft Site-Wide Quality Assurance Project Plan (covering the general sampling and analytical procedures to be used during the investigations), a Draft Site-Wide Health and Safety Plan (addressing the health and safety procedures for on-site workers), a Draft Site-Wide Data Management Plan, a Draft Site-Wide Conceptual Site Model, a Draft Site-Wide Groundwater Work Plan (OU-1), a Draft Process Areas Work Plan (OU-3) and a Draft Pit Lake(OU-2) Work Plan. The Site-Wide Quality Assurance Project Plan, Health and Safety Plan, and Data Management Plan have been finalized. The other plans are currently undergoing review by EPA or have been put on hold until further information is known about the site. The plans will be revised as needed until final versions are approved.
ARC completed the installation of 14 additional groundwater monitoring wells in 2008 and completed the installation of 94 additional groundwater monitoring wells north of the site in 2011. ARC submitted a work plan to install additional monitoring wells on site; this work plan is in review. Our current information shows that exists shallow groundwater contamination from the mine near the northern boundary of the mine. Groundwater investigations are ongoing as EPA receives more information from the expanded groundwater monitoring well network. EPA and ARC have discussed a groundwater background investigation to determine what levels of contaminants can be considered naturally occurring. This background investigation will help us to further differentiate mine-related contamination from naturally occurring contamination.
EPA worked with ARC to revise the Domestic Well Monitoring Program in 2009 to increase the number of domestic wells sampled and to increase the frequency of sampling. As of August 2011, over 150 domestic wells are sampled quarterly or semiannually for radionuclides and metals. In addition, ARC continues to provide bottled water to residents if well water exceeds 25 ug/L uranium during one sampling event. (See Groundwater under the Threats and Contaminants section above.)
In 2005, ARC completed initial soil and groundwater sampling in the Process Areas, and installed new monitoring wells at 15 locations. Furthermore, ARC completed an initial radiation survey focusing on on-site worker exposure limited to work areas in 2004 and 2005. EPA conducted an additional radiation survey of the process areas in the summer of 2007. (See Initial Actions section above).
ARC provided the results of the 2004-2005 soil and groundwater sampling in the Data Summary Report for Process Areas Soils Investigation and the Data Summary Report for Process Areas Groundwater Conditions. Samples were analyzed for metals, radiochemicals, total petroleum hydrocarbons (TPH), volatile organic compounds (VOCs), semi-volatile organic compounds (SVOCs), herbicides, and pesticides. ARC summarized the results and identified additional sampling locations in the Draft Process Areas OU-3 Remedial Investigation Work Plan, which was provided to EPA in 2007.
ARC initiated geophysical investigations of the Process Area in 2010 to identify subsurface utilities (i.e., pipes, dry wells, etc.), which may be ongoing sources of contamination at the site. The geophysical investigations will continue to be performed through 2011.
Previous soil and groundwater sampling results as well as results from the geophysical investigations will be used to further the Process Area investigation.
EPA and ARC have initiated activities to address the wildlife and fugitive dust threats in OU-4 (described above in the contaminants and risks section). ARC implemented a Work Plan for Characterization of the Inactive Evaporation Ponds in September and October 2008, and initiated a Wildlife Mitigation Plan for the pumpback collection ponds at the same time. Results from the characterization of the evaporation ponds have been provided and are under review. These results will be used to plan the remedial investigation for OU-4.
EPA completed the Public Review Draft of the Arimetco Remedial Investigation Report in July 2008 and solicited public input on the report. In 2009, EPA conducted supplemental investigations to evaluate groundwater, soils and processing facilities at Arimetco. EPA initiated an evaluation of cleanup alternatives in 2010. EPA completed the Draft Feasibility Study for the Arimetco Heap Leach Pads and Drain-Down Fluids in 2011 and will accept public comments after the document is released.
ARC will submit additional work plans to EPA for the following OUs according to the schedule agreed to by EPA and ARC: Evaporation Ponds/Sulfide Tailings (OU-4), Waste Rock Areas (OU-5), Oxide Tailings (OU-6), and Wabuska Drain (OU-7). The original schedule was tied to the completion of the initial Process Area characterization; EPA and ARC have initiated characterization activities of the Process Area to support interim removal actions at OU-3 to address radiological materials. (See Initial Actions section above.)
Cleanup Results to Date
The site is currently undergoing Remedial Investigation and interim response actions to deal with immediate hazards. See section Response Action Status (above) for further details.
Potentially Responsible Parties
Potentially responsible parties (PRPs) refers to companies that are potentially responsible for generating, transporting, or disposing of the hazardous waste found at the site.
Atlantic Richfield Company – 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. ARC merged with Anaconda Copper Mining Company (ACM) of Montana in 1977. ACM/ARC owned at the Anaconda Yerington Mine from 1941 to 1982.
Don Tibbals – In 1982, local citizens Don and Joy Tibbals purchased the Mine property from ARC. Mr. Tibbals conducted some mining operations and leased portions of the property until 1988. Mr. Tibbals also developed a series of residential parcels toward the exterior of the site, known as Weed Heights.
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. Assets owned by Arimetco are currently being managed by the bankruptcy court.
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).
Documents and Reports
|03/24/11||Draft Anaconda Community Involvement Plan|
|08/13/12||Public Notice on Voluntary Settlement with Singatse Peak Services on Portion of ARIMETCO (Operable Unit 8)|
|01/31/13||Groundwater Investigation Community Meeting Presentation|
|01/31/13||Yerington Mine Site Public Meeting Groundwater Operable Unit (OU-1) Remedial Investigation (RI) Update Presentation|
Open Letter to Yerington Community, mailed 1-29-2010.
Site Contact Information.
PUBLIC AND STAKEHOLDER MEETINGS
EPA and NDEP have held general public and stakeholder meetings. These meetings are announced in the local paper and open to the public. For the public meetings, EPA also provides notices to our entire mailing list.
Public Meetings: October 20, 1999; May 11, 2000; January 29, 2001; February 27, 2003; Aug. 25, 2004; Aug. 3, 2005; Sept. 19, 2006; January 22, 2009; September 24, 2009; April 21, 2011.
Stakeholder Meetings: Aug. 17, 2004; Feb. 15, 2005; June 8, 2005; Nov. 8, 2005; Feb. 22, 2006; May 24, 2006; Jan. 16, 2007; May 9, 2007; August 22, 2007; December 4, 2007; May 15, 2008; August 19, 2008; May 28, 2009; January 7, 2010; May 4, 2010; October 28, 2010.
Next Community Meeting: To be determined.
Public Information Repositories
The public information repositories for the site are at the following locations:
Lyon County Library
20 Nevin Way
Yerington, NV 89447
Nevada Division of Environmental
Protection (NDEP) website: http://ndep.nv.gov/yerington/minesite.htm
Anaconda Mine Site video: http://www.epa.gov/region09/superfund/anaconda/index.html
US EPA On-Scene Coordinator website: http://www.epaosc.org/site/site_profile.aspx?site_id=2183
EPA Site Manager
Mail Code SFD
75 Hawthorne Street
San Francisco, CA 94105
EPA Community Involvement Coordinator
Mail Code SFD
75 Hawthorne Street
San Francisco, CA 94105
EPA Public Information Center
Atlantic Richfield Company
LaPalma, CA 90623-1066
Chairman Linda Howard
Environmental Director Lauryne Wright
603 West Bridge Street Yerington, NV 89447
1301 Financial Blvd.
P.O. Box 12000
Reno, NV 89520
After Hours (Emergency Response)