EPA testing extent of contamination at Anaconda Mine

Workers for the federal Environmental Protection Agency are using a state-of-the-art radiation detector to test for contamination at the old Anaconda Mine in Yerington.

A sophisticated gamma radiation detector on a modified tractor is equal to about six detectors in one, said Nadia Hollan Burke, environmental engineer and Superfund project manager.

That, along with hand-held radiologic survey equipment, should give the EPA the information it needs to begin a large-scale cleanup of the long-closed mine.

Hollan Burke said the rock in the area has naturally occurring uranium, with copper and arsenic present. She added that mining appears to have enhanced the levels of radiation, making radiological contamination more pervasive on the mine site.

She said the wells of nearby residents had elevated levels of uranium, but the source of the contamination has not yet been determined.

"That's to help determine whether groundwater contamination is related to the site," she said.

In addition, workers were using a drill rig to sample soil under existing heap leach ponds to determine how to permanently close the ponds and prevent acid contamination of groundwater.

"The ponds contain acidic water and high concentrations of metals," she said. "We don't want them to leak through the ponds and start impacting the groundwater."

The liners on the leach ponds are deteriorating, with many of them in tatters. EPA workers have built a new evaporation pond on the mine site's processing area so water will flow into the pond instead of into the ground.

Last spring, the EPA capped 100 acres of mine tailings to prevent erosion and dust blowing from the site. In late summer the agency constructed and lined two new heap leach evaporation ponds before the fall and winter rain season to prevent overflow of mine drainage. Work to date, including current sampling work, has run just over $2 million.

The EPA is also supervising Atlantic Richfield employees who are drilling monitoring wells and collecting soil samples around the former mine. Atlantic Richfield is a prior owner of the site.

Earlier this week workers used a geoprobe to drill into ponds to collect water and soil samples. They should get results in about a month.

"This will give us a better idea of what we need to do to close the ponds," she said. "We have to do a long term cleanup at the site that will take many years."

Hollan Burke said that though the Anaconda Mine is not on the Superfund national priorities list, the EPA was using Superfund laws, funding and procedures to clean up the site.

• Contact reporter Karen Woodmansee at kwoodmansee@nevadaappeal.com or 882-2111 ext. 351.

Timeline

• 1918-1920: Empire Mine operates at Yerington site.

• 1920-1953: No operations at Yerington site.

• 1953-1978: Anaconda Copper Company operates the mine, disposes of mining wastes, including acid brines and tailings into evaporation ponds located on site.

• 1973: NV Bureau of Mines - Bulletin 81 reports on radioactivity at site.

• 1976: MJ Bright Report describes uranium in evaporation ponds.

• 1977: Atlantic Richfield purchased Anaconda as the Yerington Mine was shutting down.

• June 30, 1978: Anaconda closes Yerington Mine.

• 1978: Mine sold to private entrepreneur who leased portions of the site to other companies for salvaging activities.

• 1979: Yerington Mine entered into Comprehensive Environmental Response Compensation Liability Information System (CERCLIS) database.

• 1979: Anaconda Internal Memo describes radioactive contents of evaporation ponds.

• 1979: National Uranium Resource Evaluation Report describes uranium content of northwest Nevada copper ore.

• 1982: EPA completes hazard ranking package.

• 1982-1988: Copper Tek conducts operations to remove copper from tailings, using solvent extraction electro-winning process.

• 1985: Atlantic Richfield ordered by the Nevada Division of Environmental Protection to address impacts to groundwater. As a result, a series of extraction wells are installed along the northern, down gradient boundary. Continued migration of groundwater plume prompts new concerns regarding leakage of the evaporation ponds and efficiency of the pump-back extraction system.

• 1988: Arimetco purchases the property, including the unpatented mining claims. Arimetco had conducted a closed system copper extraction process of tailings from Anaconda's operation on leased land prior to the purchase.

• 1989-2000: Arimetco conducts operations to remove copper from tailings, as well as from ore mined at the MacArthur site, using solvent extraction electro-winning process.

• 1990: EPA conducts CERCLA evaluation of site.

• 1993: Arimetco expands operations and posts a reclamation bond.

• 1994: EPA conducts CERCLA prioritization, determines that the Yerington Mine is eligible for listing on National Priority List (NPL) as a Superfund site.

• 1997: Arimetco files for bankruptcy, but continues to operate the mine until January 2000.

• 1999: Additional pumpback wells installed by Atlantic Richfield in an effort to contain the groundwater plume which had migrated off-site.

• 2000: Arimetco abandons the site, leaving four operational heap leach pads with approximately 92 million gallons of pregnant leach solution still in the system.

• 2000: Environmental Protection Agency requests State of Nevada's position.

• 2001: Governor Guinn states NPL is not best interest for Yerington Mine at this time.

• 2002: Nevada Division of Environmental Protection, EPA and BLM sign Memorandum of Understanding (MOU) to coordinate both investigative and response actions to remediate mine site. Time lines for various site investigations or work plans were proposed and approved for developing 13 industry standard work plans at CERCLA level of acceptance.

• Summer 2003: BLM discovered Anaconda documents at University of Wyoming archives.

• October 2004: BLM management oversight moves from Carson City Field Office to Nevada State Office in Reno.

• December 2004: Nevada Gov. Kenny Guinn formally requests that EPA take over regulatory control of the former Anaconda site at Yerington mine. EPA agrees to assume primary responsibility for cleanup of the site.

- Source: Environmental Protection Agency