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Superfund Redevelopment Initiative

Superfund Sites in Reuse in Nevada

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Carson River Mercury Site

The Carson River Mercury Superfund site includes 236 former mill sites and 130 miles of the Carson River in Lyon, Storey, Carson, Washoe and Churchill counties in western Nevada. Contamination at the site resulted from historic gold and silver mining during the late 1800s. Workers used imported mercury to remove precious metals until the end of the century, when they switched to cyanide heap leaching. About 7,500 tons of mercury eventually contaminated the Carson River and land next to the river. EPA added the site to the National Priorities List (NPL) in 1990. The Nevada State Health Division created an advisory to prevent people from eating fish from affected water sources. EPA posted bilingual signs at access points and around Lahontan Reservoir and access points along the river. EPA is addressing contamination in two operable units (OUs). As part of the OU1 (source area) remedy, EPA removed mercury-contaminated tailings from high-exposure risk areas such as parks. EPA’s Superfund Redevelopment Initiative (SRI) supported a regional seed project at the site in 2007. The project looked at ways to clean up contaminated soil and implement protective measures to allow for residential development in a rapidly-growing area. Cleanup included the removal of contaminated soils from five residential areas in Dayton and Silver City. EPA also restored infrastructure and landscaping disturbed by cleanup activities. The Virginia City Historic District, where many of the historic mill sites are located, depends heavily on tourism. The areas surrounding the Carson River are mostly agricultural, although the area is undergoing a housing boom to support the high-tech businesses situated along the nearby USA Parkway (e.g., Tesla battery plant). EPA and the Nevada Division of Environmental Protection (NDEP) continue to work with developers and homeowners in the affected towns to identify and prevent unacceptable risk of exposure to contamination. EPA coordinates closely with the counties’ building and planning departments on the site’s cleanup plan. EPA and NDEP recently updated the Long-Term Sampling and Response Plan (LTSRP), to continue implementing remedial actions at residential properties impacted by the source releases in the floodplain. The plan relies on institutional controls to allow the site’s continued, residential use throughout the cleanup process. OU2 is comprised of surface water, bedded sediments, bank and lake sediments, the banks of Carson River and the adjacent floodplain soils. The OU2 remedial investigation was completed in 2017, the feasibility study in late 2018 and the Record of Decision is anticipated in December 2020. EPA is currently evaluating the costs and benefits of cleaning up contamination in the river, reservoir and wetlands. EPA is also determining what type of cleanup, if any, is warranted. Additional landowners include the U.S. Bureau of Reclamation, Bureau of Land Management, Fish and Wildlife Service and the Fallon Naval Air Station. An expanded LTSRP is anticipated to address industrial, commercial, agricultural and public service sectors sharing the floodplain.
Last updated September 2019

As of December 2019, EPA had data on 63 on-site businesses. These businesses employed 465 people and generated an estimated $20,004,348 in annual sales revenue. For additional information click here.

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