Mining activity in the 19^th to 20^th century was one of the drivers of western expansion in the United States. However, as those mines played out and miners moved on, the mines themselves remained. In fact, the Bureau of Land Management estimates up to a half-million abandoned mine lands exist in the United States.  Of these, the Government Accountability Office estimates 131,000 are abandoned hardrock, or base metal (e.g., gold, silver, copper) mines in the western United States, with approximately 33,000 sites resulting in the degradation of environmental quality. 

Few of these sites have been evaluated to determine potential for continued environmental impacts, or exacerbated environmental impacts resulting from shifting land-use, including urbanization, road construction, or a resurgence in mining.  Evaluating environmental impacts of historical mine sites is most effective if conducted using teams of multi-disciplinary scientists, including hydrologists, geologists, geochemists, and ecologists. 

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The East Fork South Fork Salmon River watershed in central Idaho is at the headwaters of the South Fork Salmon River, a spawning area for Chinook salmon, steel head and bull trout, fish that are listed under the Endangered Species Act.  Cinnabar Creek, a tributary to this stream, flows through the Cinnabar mine site, an inactive mercury mining site.  This site is being evaluated for remediation by the U.S. EPA due to elevated metal concentrations, including mercury and arsenic, associated with mine tailings, sediment and water. 

An interdisciplinary team of U.S. Geological Survey scientists are evaluating the Cinnabar mine site and the East Fork South Fork Salmon River watershed to quantify environmental impacts of historical mining.  A watershed analysis has been conducted to determine background sites upstream from historical mining areas where geologic inputs to stream and sediment could assessed. Transportation of mercury and arsenic from mine tailings to downstream sediments is evaluated using mineralogical, geochemical and isotope analyses.  Mercury transfer from the stream to the biota is being evaluated by ecologists who study insects, spiders and fish.

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This work is being conducted in cooperation with the Nez Perce Tribal Fisheries Resources Program, the U.S.D.A. Payette National Forest, the U.S. EPA, with site access being provided by Midas Gold Corporation.  Our data and our interpretations are being used to help inform a better-informed effort towards remediating the Cinnabar Mine site, with the goal of improving the quality of this salmon fishery. 

Learn more about this project here, and learn more about other USGS minerals research in the Yellowpine area here.