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Environmental geology
Skiing and mining intersect in Colorado

Ski resorts use snowmakers to enhance their snow-pack early and late in the season when natural snowfall may be less predictable. In Colorado and across the West, drought over the past few years has necessitated increased snowmaking at many resorts. But when the water for the snow is drained out of contaminated rivers, pollutants can spread. Resorts are left with a difficult choice: drain streams and risk the spread of contamination in order to keep the slopes open, or potentially take a financial loss by not producing snow and having to close ski runs. A paper published in the Sept. 23 Eos by researchers at the University of Colorado, Boulder, and the Northwest Colorado Council of Governments explores the relationship between river contamination from abandoned mines and snowmaking activities at ski resorts in a state where tourism provides $9 billion annually.

Arapahoe Basin Ski Area, located in the Snake River watershed, is taking water-quality issues into consideration in its development and artificial snowmaking plans. Image courtesy of Arapahoe Basin Ski Area.

The paper is a synthesis of past studies on the Snake River watershed, which drains into the reservoir that provides the primary drinking water source for the Denver metropolitan area. The watershed hosts not only abandoned or inactive mines, but also extensive U.S. Forest Service lands used primarily for recreation, a small town, numerous unincorporated residential developments and two renowned ski resorts. The Colorado Unified Watershed Assessment has identified the watershed as impaired and in need of restoration due to elevated concentrations of zinc, cadmium, copper, lead and manganese.

Mining began in the Snake River watershed in 1864, with the discovery of silver, and continued into the early 20th century. Across Colorado, roughly 7,000 of those now-abandoned mines leach waste minerals into more than 1,600 miles of streams. The sulfides exposed by mines and mine wastes, or from constructed excavations such as road cuts or tunnels, lead to acid-rock drainage — acidic, metal-enriched water formed from a chemical reaction between water and sulfur-bearing rocks.

The Snake River drains a watershed where pyrite, an iron sulfide, is interspersed throughout the rock that encloses the metal deposits. Acid-rock drainage occurs naturally as water drains through the pyrite and reacts with air and water to form sulfuric acid and dissolved iron. The acid runoff further dissolves heavy metals such as copper, lead and mercury into ground or surface water. Acid-rock drainage — both natural and anthropogenic — represents the most significant water degradation issue in the region, says Geoff Plumlee, a geologist with the U.S. Geological Survey in Denver.

And the acid-rock drainage could be making its way into artificial snow at the Keystone Resort, which draws its snowmaking water from a contaminated stretch of the Snake River. In a 2001 study commissioned by Keystone and conducted by the U.S. Forest Service and Hydrosphere Resource Consultants, researchers tested the snow prior to melt and compared the chemistry of natural versus artificial snows, and also studied virgin and affected soils and vegetation. Concentrations of aluminum, cadmium, copper, lead, zinc and manganese were slightly higher in the areas affected by Snake River waters compared to areas without contact to the river water; but concentrations were still well below critical levels for life to survive.

The Arapahoe Basin Ski Area is also within the Snake River watershed, but it draws its water from an uncontaminated branch of the river, according to the Eos paper authors, led by Andrew Todd of the University of Colorado, Boulder. Nonetheless, the resort is taking water quality issues into consideration. The 2003-2004 season marks only the second year of snowmaking for the resort, which, along with the Forest Service, conducted an extensive environmental assessment before proceeding with snowmaking and other development plans. The largest issue Arapahoe faces is that the freshwater stream from which the resort makes snow currently dilutes polluted branches of the Snake downstream. Any reduction in freshwater may thus increase the pollution downstream, Plumlee says.

Arapahoe and Keystone have, in many ways, been partners to the scientists in the environmental efforts, Todd says. The ski areas are active members of the Snake River Watershed Task Force, a group of stakeholders including citizens, government agencies, environmental groups, scientists and the ski areas, which formed in 1999 to address the problem of acid-rock drainage in the basin.

Local groups, however, are crippled in their ability to help, says Lane Wyatt with the Northwest Colorado Council of Governments.

As current laws stand, groups like the Snake River Watershed Task Force would assume liability for acid-rock drainage pollution if they tried to clean up the mines or the water. “But if the liability limitations to doing voluntary cleanup were removed, I think that we would see collaborative efforts between the various stakeholders, including the ski areas, to clean up some of these problem mines,” Todd says. And Wyatt thinks it would be fairly easy to raise the money locally to start cleanup efforts in the rivers if the liability issue were off the table.

Currently, several bills are pending in the U.S. House and Senate aimed at limiting liability for so-called Good Samaritans who want to help the abandoned or inactive mine cleanup effort. “Right now we have the technologies we think will work to clean up the water, but we can’t even test them because of the liability issues,” Wyatt says.

Some of these technologies include treating the contaminated water with lime, which raises the pH to precipitate out target metals and the removal and relocation of mine waste piles, Todd says; however, these approaches may not be practical. Another cleanup method is to develop an artificial bog, which has a large capacity to absorb contaminants, says Samuel Adams, former president of the Loon Mountain Recreation Corporation, New Hampshire’s largest ski resort (and editor-in-chief of Geotimes). Water treatment plants also help remediate the water, but they are costly and determining the ideal end-state is difficult, Plumlee says. Additionally, each watershed and each possible technological solution has its own set of engineering challenges.

Water-quality problems related to acid-rock drainage are not unique to Colorado. A 1995 study by the former U.S. Bureau of Mines reports that mine contamination affects more than 12,000 miles of rivers and streams nationwide. The Environmental Protection Agency, the Office of Surface Mining, the U.S. Geological Survey and other government agencies are developing plans to remediate abandoned mine lands. As scientists work to develop viable remediation technologies, ski resorts are looking into ways to adjust to water quality and quantity issues for the future.

In the meantime, there needs to be discussion about limiting growth in the Snake River watershed, Adams says, because the climatic future is unknown. “Last time around we were looking for metal deposits and nobody had any thought whatsoever about the impacts of leaving mine wastes exposed. And now, no one has the least thought about the infrastructure that’s being developed up there,” he says. “Who knows if we’ll even have snow in a few years — we have to be careful … so we don’t destroy what’s left.”

Megan Sever

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