NDEP Programs & Services
Public Information
& More
NDEP Unique
Online Sevices
Agency Contact
More About

 Anaconda Site, Lyon County Nevada Back BCA Home Page   

What is the Anaconda Site?

Who is responsible?

What is the problem at the Site?

Is the water safe?

Has the Site affected agricultural products?

What about NPL listing?


EPA Letter to Governor 12/22/15
Governor's Time Extension 1/29/16
Governor's Response to EPA 3/29/16

Site Maps:
City Water Main extension project map
Land Ownership Map
Operable Unit Map

Groundwater Maps:
Site Cross Section Location
Uranium Cross Section
Uranium Plume Map

Arimetco portion of Site, OU-8
Anaconda Proposed Plan [pdf, 1MB]
Public Notice to Solicit Comments on Proposed Anaconda Mine Site Cleanup Plan

EPA Anaconda website
NDEP Abandoned Mine Lands Page

What is the Anaconda Site?

The 3,400 acre Anaconda Site (Site) is a former copper mine located west of the City of Yerington, in Lyon County, Nevada. The Site includes both private and public lands managed by the Bureau of Land Management. Since the Site was abandoned in 2000, EPA and NDEP have been addressing environmental concerns and working toward long-term closure. Brief chronology of Site ownership and operations:


Anaconda Copper Company (Anaconda) initiates mining and milling operations at the Site.


Anaconda was acquired by Atlantic Richfield Company (ARC), now a subsidiary of BP.


Mining operations are closed.


Don Tibbals, a local resident, acquires the private property.


Arimetco acquires the private property and conducts re-mining using Anaconda tailings and new ore. Five heap leach pads and an electrowinning plant are constructed and operated.


Arimetco files for bankruptcy.


Arimetco ceases operation and abandons the Site.


Singatse Peak Services (SPS), a subsidiary of Quaterra Resources, acquires the private property and initiates exploration activity

Who is responsible?

Site environmental issues are being addressed under the oversight of EPA and NDEP. EPA is the lead agency responsible for overseeing investigation and remediation of environmental issues, using CERCLA (Superfund) authority. NDEP is in a support role. As a former owner, Atlantic Richfield Company/BP (ARC) has been determined to be a Potentially Responsible Party under CERCLA related to releases of contaminants from the former Anaconda operations. EPA has not determined that ARC is responsible for the Arimetco portion of the Site, consequently identifying a funding source to address permanent closure of the 260 acre Arimetco portion has been an issue since the Arimetco bankruptcy.

What is the problem at the Site?

The Anaconda operations occurred before modern environmental regulations were put in place, so many operational practices would not meet current standards and the Site was not required to be reclaimed upon closure. The Anaconda Site needs to be reclaimed, but the primary concern has been ground water. Use of unlined evaporation ponds has resulted in contamination of ground water with metal-bearing solutions. High concentrations of metals, including arsenic and uranium occur at the north end of the mine in the area of the former ponds. These contaminants have also migrated off-site in the area immediately north of the mine site. The extent and magnitude of this contamination has been extensively studied with over 350 monitoring wells installed. Atlantic Richfield Company (ARC) remains responsible for addressing issues related to the Anaconda operations, including groundwater contamination.

When Arimetco abandoned its operations in 2000, the immediate concern was management of the process fluids since the heap leach pads were fully charged with sulfuric acid process solution. The heap leach pads were all constructed on synthetic liners and the fluids are collected in lined ditches, pipes and lined pond systems. As the heaps have drained down naturally over time, the fluid flow rates have declined from over 3,000 gallons per minute in 2000 to about 10 gallons per minute currently, but the fluids, which are acidic and high in total dissolved solids, require continued management. With voluntary financial support from ARC and SPS, NDEP constructed two new evaporation ponds in 2013 to contain the drain down fluids as a stop-gap measure, but the ponds will continue to fill with evaporative salts over time, which will ultimately exceed capacity. A long term remedy is to cap and close the heaps to reduce infiltration of rainwater.

Is the water safe?

The City of Yerington water supply is safe and has never been impacted by the Anaconda Site. There are no City water supply wells located in the vicinity of the mine. City water is regularly tested and complies with state and federal drinking water requirements. Additional information on City of Yerington drinking water quality can be obtained at the City of Yerington Public Utilities Website or by contacting the NDEP Bureau of Safe Drinking Water.

Since 2004, domestic well owners north of the mine site have been provided with bottled water if uranium concentrations in their well water exceed 25 ug/l (the drinking water standard for uranium is 30 ug/l).

Uranium occurs naturally in area ground water and there was no attempt to distinguish naturally occurring uranium from mine impacted water for purposes of the bottled water program. As a result of settlement of a class action lawsuit in 2015, brought by area residents against Atlantic Richfield Company, the City of Yerington water system is being extended to the area of groundwater impact and residents that choose to participate are being connected to the municipal system at no charge. Long-term remedies for mine impacted ground water will be evaluated as Site evaluation proceeds.

With regard to surface water, there is currently no information that indicates any impact from the Site to the Walker River, although the Wabuska Drain is being investigated as a potential historical pathway for Site contaminants. Access to the pit lake is controlled, but the quality of the water is fairly good, largely reflecting mineralized natural groundwater conditions, with elevated levels of copper and selenium but a neutral pH.

Has the Site affected agricultural products?

Agricultural products grown in the area have been tested and there is no evidence that the Anaconda Site has had any impact on agricultural production. Most fields in the area are located far south and east of the Anaconda Site, either hydrologically upgradient or not hydrologically connected to the Site at all.

What about NPL listing?

While Atlantic Richfield Company (ARC) remains responsible for the majority of Site issues, including groundwater, there is a funding gap related to closure of the Arimetco heaps and ongoing fluid management. EPA first requested to list this Site on the Superfund programís National Priority List (NPL) in December of 2000 and Nevada rejected this request in January 2001. At that time, little was known about the extent of Site issues or the costs for closure of the Arimetco portion. Since then, extensive work has been done to investigate environmental issues and take interim actions to mitigate exposure risk. The Arimetco fluid management system has been operated and maintained by ARC under an agreement with EPA. In addition, the costs for permanent closure of the Arimetco heaps have been identified, these costs are estimated at $31 million.

As a matter of policy, NDEP views NPL listing as an option of last resort and instead strives to work with responsible parties and others to address environmental cleanups around the State. Cleanups at Superfund NPL sites tend to be very slow, expensive and process-laden. NDEP has had success with many cleanups working with private parties outside of the NPL process. In addition, the State is expected to contribute a 10% cost share to NPL site remedies financed with federal funds and then to pay any ongoing O&M costs.

In late 2015 and early 2016, NDEP attempted to negotiate a public-private funding agreement for the Arimetco work. Although discussions are ongoing, no agreement has been reached. EPA has again proposed to list the Site on the NPL to make the Site eligible for federal funding to address the Arimetco portion. EPA sent a letter to Governor Sandoval on December 22, 2015 requesting the Stateís concurrence with proposed NPL listing of the Site. In follow-up correspondence, EPA requested a response by March 29, 2016. Governor Sandoval sent a reply to EPA on March 29, 2016 indicating his concurrence with initiating the process of listing the site on the NPL, subject to a number of conditions that are outlined in his letter.


Nevada Privacy Policy