Superfund Information Systems: Site Profile

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The Rio Tinto Mine Site (Site) is a 280-acres abandoned copper mine located approximately 2.5 miles south of Mountain City, in northern Elko County, Nevada. The Site is located upstream of the Shoshone-Paiute Tribes’ Duck Valley Reservation on the East Fork Owyhee River. Mill Creek runs through the Site and flows into the East Fork Owyhee River. Both water bodies are impacted by mine-related heavy metals. This Site is designated as a Superfund Alternative Approach (SAA) site. Under this designation, EPA acts as support agency to the Nevada Division of Environmental Protection (NDEP, the lead agency).

The levels of copper, zinc, and cadmium in Mill Creek and the East Fork Owyhee River posed chronic and acute threats to aquatic life, including the redband trout, which is a species of cultural significance to the Shoshone-Paiute Tribes. The selected remedy required the excavation of more than 800,000 cubic yards of the tailings, with disposal in an on-site repository. Reconstruction of Mill Creek to facilitate fish movement through the area was also done. The construction was completed in November 2016.

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What Has Been Done to Clean Up the Site?

The Superfund remedy selected in the Record of Decision (2012) has been implemented and the site is now in the operations and maintenance phase. See the Technical Documents section of this web page to find the Record of Decision and the Operations and Maintenance Report for 2017.

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What Is the Current Site Status?

Water quality in Mill Creek and in the East Fork Owyhee River is being monitored to evaluate the success of the Superfund remedy. Data collected to date show removal of mine tailings from Mill Creek Valley is allowing water quality in the creek and river to naturally recover. See the Technical Documents section of this web page for the Field Sampling Plan (2013) under which this monitoring is being conducted and for a current report (2018) on water quality data.

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Activity and Use Limitations

At this site, activity and use limitations that EPA calls institutional controls are in place. Institutional controls play an important role in site remedies because they reduce exposure to contamination by limiting land or resource use. They also guide human behavior. For instance, zoning restrictions prevent land uses – such as residential uses – that are not consistent with the level of cleanup.

For more background, see Institutional Controls.

In 2018 EPA declared the site as "site-wide ready for anticipated re-use" (SWRAU). This designation means that all cleanup goals in the Record of Decision (2012) have been acheived for any media that may affect current and reasonably anticipated future land uses so that there are no unacceptable risks. Land use restrictions are in place to preserve the cleanup work that has been done. 

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