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VAIL, CO - JUNE 21: Visitors ride the zip lines at Epic Discovery part of Vail's summer development project, June 21, 2016. Vail Mountain is the first ski resort in the country to develop summer amenities under federal legislation designed to expand year-round activity at ski resorts on federal land. (Photo by RJ Sangosti/The Denver Post via Getty Images)

VAIL, CO - JUNE 21: Visitors ride the zip lines at Epic Discovery part of Vail's summer development project, June 21, 2016. Vail Mountain is the first ski resort in the country to develop summer amenities under federal legislation designed to expand year-round activity at ski resorts on federal land. (Photo by RJ Sangosti/The Denver Post via Getty Images)