Public Release: 

Contaminated water from abandoned mines threatens Colorado ski areas

American Geophysical Union

WASHINGTON - The ability of several of Colorado's prime ski areas to respond to winter drought is threatened by acidic runoff from abandoned mines, according to researchers at the University of Colorado (CU) and the Northwest Colorado Council of Governments (NWCCOG). Contamination known as acid-rock drainage enters waterways, such as Summit County's Snake River, that are used for making artificial snow. When the snow melts, this melt-water can run into streams not previously polluted, further spreading the contamination.

Writing in the 23 September issue of Eos, published by the American Geophysical Union, Andrew Todd and Diane McKnight of CU and Lane Wyatt of NWCCOG describe the process by which the legacy of mining, once the mainstay of Colorado's economy, is adversely affecting tourism, now a nine billion dollar industry.

They note that the problem is not limited to Colorado or to the United States. Nationwide, mine contamination affects more than 12,000 miles [19,000 kilometers] of rivers and streams and 180,000 acres [73,000 hectares] of lakes, according to the U.S. Bureau of Mines.

In Colorado alone, some 7,000 abandoned mines continue to leach waste minerals into more than 1,600 miles [2,600 kilometers] of streams. The state's mining history is clearly visible to motorists on highway I-70, heading west from Denver to the ski areas of Summit County, in the form of orange tailings, weathered structures, and even in the names of some communities and ski trails.

Colorado's ongoing drought has made artificial snowmaking essential in many areas, including Keystone and Arapahoe Basin, focus of the authors' study. The mainstem of the Snake River, which is contaminated with heavy metals, has been the source of Keystone's artificial snow since 1971. These metals have been detected in headwater drainages within the ski areas, according to a recent study conducted by Hydrosphere, a regional consulting firm.

Resort management is seeking to more than double the amount of Snake water it utilizes for snowmaking. Currently, at the point where river water is diverted for this purpose, concentrations of zinc, cadmium, and copper occasionally exceed criteria for aquatic life, including three of the four species of trout typical of local streams.

Although periodic droughts are normal in Colorado, affecting at least five percent of the state almost all of the time for longer or shorter periods, ski resorts are also concerned about the potential additional impact of climate change, which could add to the problem of inadequate snow. Recent studies cited by the authors suggest that warming, under even the most conservative scenarios, could shorten the ski season, shift ski areas to higher elevations, and eliminate some marginal areas altogether.

One method of mitigating these effects would be additional snowmaking on a large scale. Another is moving to a four season strategy, with summer activities focused on such activities as fishing, golf, and rafting. Many of these activities depend on clean water supplies, however, and winter snowmaking, using dwindling and contaminated water, can adversely affect these other sports. The authors observe that at present, there are no reliable methods of mitigating acid-rock drainage at its source, the abandoned mines that dot today's recreational areas.


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