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What is the problem at the Site? |
LINKS Correspondence: Site Maps: |
Groundwater Maps: Arimetco portion of Site, OU-8 |
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What is the problem at the Site? |
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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. |
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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. |
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Is the water safe? |
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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). |
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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. |