Acid drainage not just a mine issue anymore -- communities, recreation areas face emerging challenges

Colorado's Snake River carves a swift path from snowmelt sources in the Rocky Mountains through decaying remnants of the state's more-than-century-old mining history and the heart of its busy winter resort region before spilling into the Blue River and eventually feeding the Colorado.

The Snake's waters are pulled in all directions. Plagued by mining pollution, siphoned by local towns and ski developments, and prodded by fishermen and scientists, the river has become a poster child for how competing interests in Colorado have to make do with diminishing supplies of clean water in the face of climate change.

Now the river faces another emerging threat -- naturally occurring acid contamination.

In a report published last month, the Colorado Geological Survey identified 11 headwater regions in Colorado, including the Snake's, where rivers have elevated levels of acid and heavy metals, including arsenic, cadmium, copper and zinc, due to geological processes independent of human activity.

Such contamination is the result of a complicated series of geochemical reactions that started when hot water in the Earth's crust created pyrite, or "fool's gold," and other sulfide minerals in rocks. When these rocks are pushed to the surface and exposed to oxygen, they essentially rust, forming vivid yellow, orange and red iron oxides that coat river bottoms and lakebeds. The oxygen pushes sulfur out of the rock and into the water, where it forms a sulfuric acid capable of leaching metals from other rocks.

This naturally occurring phenomenon, called acid rock drainage, has been in action for thousands of years. A much newer, man-made process, called acid mine drainage, creates the same water quality problems when mining tailings and tunnels are exposed to oxygen.

In Colorado, natural and man-made acid drainage areas often sit side by side -- along the state's Mineral Belt. The combination of the two can cause severe water quality problems downstream, according to the Colorado Department of Natural Resources, which oversees the state Geological Survey and the Division of Water Resources.

The Colorado DNR warns that naturally occurring contamination adds an additional layer to any cleanup efforts.


"In these situations it is important to distinguish the natural, or background, water quality so that realistic cleanup goals for water quality can be set," the agency said in a press release about the Geological Survey's findings.

Die-offs of stocked trout near Keystone Resort in eastern Summit County have been blamed on acid mine drainage in the Snake.

While there are an estimated 7,300 abandoned mine sites in the Colorado, at least 450 of which have measurable levels of toxic discharge, such pollution hot spots are not unique to Colorado. There are nearly 500,000 abandoned and inactive mines across 32 states, according to the U.S. Geological Survey.

Skiing on acid

Acid rock and mining contamination have had some unexpected consequences. Significant levels of heavy metals in the Snake have threatened to lock down the use of the river and its tributaries for snow-making at Keystone Resort and Arapahoe Basin, both just an hour west of Denver.

When Keystone wanted to expand its snow-making water diversion from 550 to 1,350 acre-feet in the late 1990s and early 2000s, the Forest Service commissioned an investigation into water quality implications.

In 2001, independent consultant Hydrosphere determined that snow-making (which has been occurring at Keystone since 1971) could spread metal contamination into cleaner streams. The report concluded that the results were not severe enough to warrant a snow-making moratorium on existing operations, but they did recommend further evaluation of new snow-making projects.

In the Snake River specifically, scientists discovered levels of zinc that exceeded standards for fish and other aquatic life.

"Keystone did not expand their snow-making, so the issue -- if there was one -- went away," said Lane Wyatt of the Northwest Colorado Council of Governments, who was the co-author of a 2003 paper on the implications of abandoned mines and climate variability on mountain sports and Colorado's tourism economy.

Kelly Ladyga, vice president of corporate communications at Vail Resorts, which owns Keystone, said snow-making is an important part of the resort's early-season operations, and that officials closely follow environmental regulations, regularly test snow-making water sources for pollution, and monitor total water use, "adjusting operations when necessary."

"Fortunately, 80 percent of the water we use is returned to the local watersheds," Ladyga said.

She added that the resort's focus on water availability and water quality led it to "actively participate in community-based restoration efforts, such as the Snake River Task Force," a coalition of stakeholders in the river that has looked into various pollution management strategies and Pennsylvania Mine cleanup options.

Just up the road from Keystone, an expansion of the Arapahoe Basin ski area was threatened by acid mine and rock drainage. In 1998, Arapahoe proposed snow-making with water from the relatively pristine North Fork of the Snake River as a way to stay competitive with other resorts. But some voiced water quality concerns, saying that withdrawals would decrease water available for acid mine dilution downstream. In the end, the Forest Service gave Arapahoe permission to make snow.

"The snow-making issue is just one example of how Colorado is a loser state under changing climate," said Diane McKnight, a professor of civil, environmental and architectural engineering at the University of Colorado, Boulder, and one of Wyatt's co-authors. "It constrains the ability [of ski resorts] to adapt because of the impaired water quality. Snow-making is an example of how there is a need year-round for better-quality water -- and not just for keeping invertebrates alive."

According to a 2008 report from the National Conference of State Legislatures, Colorado has seen rising temperatures, increased rain and altered surface water flows over the last 50 years because of climate change. Less secure water supplies, less snowpack and earlier spring thaws seem to be a given for some in the state's $2 billion snow-sports industry. The conference warns that a shorter ski season could mean $375 million and more than 4,500 jobs lost by 2017.

In an effort to boost recreation economics, and in possible anticipation of shorter ski seasons, Congress passed the Ski Area Recreation Opportunity Enhancement Act of 2011 this fall. The new law amends the National Forest Ski Area Permit Act of 1986 to allow for a wide range of year-round activities to take place at resorts on public lands (E&E Daily, Oct. 19, 2011).


The solution to the issues raised at Keystone and Arapahoe is "to make incremental improvements in water quality by cleanup of upstream abandoned mines," Wyatt said.

The Pennsylvania Mine on Peru Creek, a tributary of the Snake River, is the primary source of mining pollution in the area, exacerbating levels of natural acid rock drainage.

According to Trout Unlimited, acid mine drainage has left Peru Creek "completely devoid of aquatic life." The mine actively excavated gold, silver, lead, copper and zinc from 1879 until it was abandoned in the 1940s.

In the 1980s, the Colorado Division of Minerals and Geology built a failed treatment system on the site. Nearly a decade later, U.S. EPA and Trout Unlimited pooled resources to plan for an improved treatment plan, but that was abandoned when it became clear that any remediation would make any parties liable for pollution under the Clean Water Act (E&E Daily, July 15, 2011).

The site is currently monitored for water quality and, according to EPA's website, remains under consideration for a Superfund designation.

"For years, Congress has been considering various versions of Good Samaritan legislation [that would release interested parties, including environmental and community groups, ski resorts and local and federal government agencies, from liability], and it's time that it finally passes," said Bruce Stover, director of the Colorado Inactive Mine Reclamation Program at the Colorado Division of Reclamation, Mining and Safety. "Our rivers need it. Fish need it. We need it."

Wyatt of the Northwest Colorado Council of Governments said that there has been recent progress "with agreements between Summit County and EPA to move forward on some potential projects. The ski areas are caught in the middle, but should be given credit for participating in cleanup projects where they are not forced to," he said.

Eichenseher is a freelance journalist based in Boulder, Colo.

Like what you see?

We thought you might.

Start a free trial now.

Get access to our comprehensive, daily coverage of energy and environmental politics and policy.



Latest Selected Headlines

More headlinesMore headlines

More headlinesMore headlines

More headlinesMore headlines

More headlinesMore headlines