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SOMERSET, CO - APRIL 27: Seven miles into the West Elk Mine, workers continue to mine for coal, April 27, 2016. The mine is the last coal mine still operating in the area. Two other mines near Somerset recently closed. (Photo by RJ Sangosti/The Denver Post via Getty Images)

SOMERSET, CO - APRIL 27: Seven miles into the West Elk Mine, workers continue to mine for coal, April 27, 2016. The mine is the last coal mine still operating in the area. Two other mines near Somerset recently closed. (Photo by RJ Sangosti/The Denver Post via Getty Images)