The McDermitt and Cordero Mercury Mine sites consist of several non-contiguous locations: the McDermitt Mine, the Cordero Mine, areas within the town of McDermitt where apparent mine waste has been used as fill, and areas of the Fort McDermitt Pauite Shoshone Reservation (the Reservation) where apparent mine waste has also been used as fill. The town of McDrmitt is located roughly 70 miles north of Winnemucca, NV, along Highway 95. The Fort McDermitt Pauite Shoshone Indian Reservation is located 3.5 southeast of the town of McDermitt and the McDermitt and Cordero Mines are located 7.2 miles southwest of the town of McDermitt.
The Cordero Mine operated from the 1930s until 1970, and is located on land owned by the BLM and on private land. The adjacent McDermitt Mine was operated from 1973 until the late 1980s. The McDermitt Mine is located on private land. The McDermitt Mine was closed under a permit from the Nevada Division of Environmental Protection (NDEP), and a final closure report was submitted in December, 1994.
The EPA Site Assessment program conducted a Site Inspection in 1988 which recommended no further action. Upon request from the Fort McDermitt Pauite Shoshone Tribe, EPA Emergency Response conducted an additional site visit in November 2009. At that time, EPA was notified of the possibility that mine waste had been used as fill at locations within the town of McDermitt and on the Fort McDermitt Paiute Shoshone Reservation.
In September and October of 2010, EPA conducted sampling of areas of red-colored fill located in the town of McDermitt and on the Reservation. The town of McDermitt straddles the Nevada/Oregon border and numerous areas were identified which contained mercury and arsenic in soil at concentrations which exceeded the EPA Region 9 residential Soil Remediation Goals (SRGs). Two areas were identified on the Reservation which contained mercury and arsenic in soil at concentrations which exceeded the residential SRGs.
In June 2011, EPA conducted additional sampling of the mine waste present at the mine site and present in the town and on the Reservation. The goal of this sampling effort was to evaluate the bioavailability and mineral speciation of the mercury and arsenic. The USGS provided technical and analytical support to EPA in this effort.
On October 16, 2012, EPA signed an Action Memorandum describing removal activities to be performed. EPA also issued Unilateral Order to both Sunoco and Barrick Gold requiring these companies to participate in the cleanup process. To date, both companies have declined to participate in work under these Orders.
From April 15-May 23, 2013, EPA conducted a removal action at this site. The following work was performed.
Residential Properties: In total 56 residential properties (54 in town and 2 at the Reservation) were addressed. This work consisted of removing calcine material, placing clean backfill material and compacting. At a few larger properties, calcine material was not removed, but rather a cover of clean material was placed over top. . To the best of EPA's knowledge, all residential properties (within the town of McDermitt and at the Reservation) with calcine material were addressed.
McDermitt Combined School. Cover material was placed over the east side of the football field, the large parking area adjacent to the football field, and the areas surrounding the playground.
Roadways. A total of 40,410 sq ft of mine waste was capped in place at two unpaved roads located just east of Buckskin and Reeves Roads in the town of McDermitt. This work was performed in conjunction with the McDermitt GID. Additionally, EPA provided backfill material to Malheur County, Oregon in order to cap 25,270 sq ft of mine waste at one unpaved road, identified as Margarita Road and located west of US 95. At the Fort McDermitt Indian Reservation, 25,586 sq ft of mine waste was capped in place at one unpaved access road leading to the Tribal transfer station.
Repository at Cordero Mine Calcines Pile. A total of approximately 10,000 tons of calcine material excavated from the town of McDermtt and the Fort McDermitt Paiute Shoshone Indian Reservation were placed at the repository.