Anaconda Mine
EPA #: NVD083917252
State: Nevada(NV)
County: LYON
City: YERINGTON
Congressional District: 2
Other Names: YERINGTON MINE, ANACONDA COPPER COMPANY MINE
Bulletin Board
Technical Documents currently under review are immediately available at a new website!
http://38.223.231.33/sites/epanevada/
User name: clients\public
Password: public
Public meeting: Thursday, Sept. 24, 2009 7:00 pm, Yerington Elementary School
Description and History
NPL Listing History
NPL Status:
Proposed Date:
Final Date:
Deleted Date:
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, and from approximately 1952 to 1978 conducted mining and milling operations at the open-pit, low-grade copper mine. Anaconda processed both copper oxide and copper sulfide ores. They removed the overburden, and dug the ore out of the pit which required pumping water 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, 3,000 acres of contaminated tailings, and 1,377 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, and all activities were shut down in 1982. When Anaconda operations ceased, groundwater pumping stopped, resulting in the Pit Lake. It is now 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. They used piles left by Anaconda, and added some new ore, built 250 acres of heap leach piles and produced copper. 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 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.
Top of page
The threats we are 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 and debris and the 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, 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 confirmed the presence of uranium in off-site domestic wells 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. Additional investigations are being planned to further define sources from the mine from naturally occurring sources. While the source is being investigated, ARC is providing bottled water to households with domestic wells that exceed 25ug/L Uranium (Federal Drinking Water limit is 30ug/L). Approximately 180 households are currently on this program.
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 (Particulate matter less than 10 microns (PM10) and total suspended particulate (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 procedure 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 will also conduct a baseline human health risk assessment to determine whether the contaminants pose a chronic threat to human health. In the meantime, ARC will conduct an interim action involving capping the inactive evaporation ponds and a portion of the sulfide tailings to further reduce dust migration under an agreement with EPA signed in April 2009.
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 during rain events. 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. These areas are primarily contaminated with heavy metals and low pH levels. ARC has also been monitoring wildlife since March 2007 and operating bird deterrent systems at site's evaporation ponds and the Arimetco ponds since September 2008. The remaining areas are planned to be investigated by ARC as well under an EPA Order.
Top of page
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 in 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” system designed to contain the groundwater contamination plume. ARC initially installed five wells on the northern end of the site. These and additional wells pump contaminated water from the plume into three lined evaporation ponds on-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 also stops contamination from reaching the Walker River via the Wabuska Drain.
In the late 1990s, the 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, 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.
2000-2005
The Nevada Division of Environmental Protection (NDEP) performed emergency removals from the site starting in 2001 until 2003 and assumed maintenance of the site in 2000.
EPA considered proposing the site for placement on the NPL in 2001, however the State of Nevada objected since they were working on the site under a voluntary agreement with Atlantic Richfield Company. 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 if that approach did not prove effective. EPA negotiated a Scope of Work and Memorandum of Understanding with the State of Nevada Division of Environmental Protection (NDEP) and the 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.
2005-Present
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 system and Arimetco heap leach fluids management system and prepare Operations and Maintenance (O&M) Plans, continue ongoing investigations of the Process Areas, sample domestic wells for uranium, supply bottled water to residents, and implement a groundwater study.
ARC completed an initial radiation survey focusing on on-site worker exposure limited to work areas in 2004 and 2005. EPA conducted additional radiation survey of the process areas in the summer of 2007. (See also Initial Actions paragraph below). ARC also conducted air quality monitoring from January 2005 to April 2008, and has submitted an Air Quality Monitoring Program Data Summary Report (May 2008) and a Baseline Human Health Assessment Work Plan for the Inhalation Pathway (June 2008). The results of the monitoring are currently under review by EPA. (See also Fugitive Dust under the Threats and Contaminants section above.)
In 2005 ARC also completed initial soil and groundwater sampling in the process area, and installed new monitoring wells at 15 locations. 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 2007 ARC also initiated installation at an additional 14 groundwater monitoring well locations, and completed the installations in early 2008. In addition to this work, ARC has continued to conduct quarterly and annual groundwater monitoring of monitoring wells, quarterly domestic well sampling for radionuclides and annual domestic well sampling for metals, and provides bottled water to residents with wells exceeding the uranium Maximum Contaminant Level (MCL). (See also Groundwater under the Threats and Contaminants section above.) 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 (March 2009).
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 up the site into manageable operable units (OUs) that will each require their own investigation and cleanup strategy: Site-Wide Groundwater (OU1), Pit Lake (OU2), Process Areas (OU3), Evaporation Ponds/Sulfide Tailings (OU4), Waste Rock Areas (OU5), Oxide Tailings (OU6), and Wabuska Drain (OU7). EPA will concurrently conduct a “fund-lead” remedial investigation and feasibility study for the Arimetco operated portions of the site, designated as OU8.
Under the 2007 EPA Order, ARC has submitted a 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 Planaddressing 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 (OU1), a Draft Process Areas Work Plan (OU3) and a Draft Pit Lake(OU2) Work Plan. The Health and Safety and Data Management Plans have been finalized, and the other Plans are currently undergoing review by EPA, and are being revised as needed until final versions are approved.
ARC will submit these additional Work Plans over the next couple years for the remaining operable Units according to the schedule agreed to by EPA and ARC: Evaporation Ponds/Sulfide Tailings (OU4), Waste Rock Areas (OU5), Oxide Tailings (OU6), and Wabuska Drain (OU7). The original schedule was tied to the completion of the initial Process Areas characterization, however as EPA is still reviewing ARC's Work Plan, EPA and ARC have initiated characterization activities to support interim removal action at OU3 to address radiological materials and on OU4 to address the wildlife and fugitive dust threats (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 will be available in June 2009.
In 2006, EPA performed emergency removals to mitigate dust from blowing off the site, remove PCB containing transformers, and repair and upgrade a couple of the leaking Arimetco fluid collection ponds. In late 2006, ARC proposed to conduct removal of radiological contamination to remove access restrictions for site workers in a 30 ft square area of the 230 acre Process Areas. To avoid repeated mobilizations, and ensure a more thorough investigation of the radiological conditions at the site was conducted prior to removal actions, EPA requested the scope of the removal be based on a complete assessment of the area. ARC declined, therefore EPA conducted a radiological removal assessment in the Process Areas 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 areas that pose a threat to on-site workers.
Also 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, 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 completed the Public Review Draft of the Arimetco Remedial Investigation Report in July 2008 and is currently evaluating public input. For 2009, EPA plans to conduct supplemental investigations to evaluate groundwater, soils and processing facilities at Arimetco, and initiate evaluation of alternatives for cleanup.
EPA and ARC signed an agreement in April 2009 requiring an update to the Pumpback System and Evaporation Ponds O&M Manual, and 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. Work Plans will be submitted in June for EPA review, and pending approval timeframes, work is expected to be on-going through the end of 2011.
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 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 Don and Joy Tibbals, local citizens, 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”).
Top of page
Community Involvement
Public 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.
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.
Next Public meeting is to be determined.
Top of page