The history of mining in Colorado is omnipresent. Whether you’re hiking in the backcountry or driving along I-70, you’re bound to come across something related to mining.

The industry, which began when prospectors first discovered gold in 1859 west of Denver, helped the state develop into what we know it as today. When the gold was tapped out, mines changed to a plethora of other materials such as coal, lead, molybdenum and even uranium to keep incomes constant. Of course, not every mine could withstand the test of time.

Although mining is still active in the state, according to the Colorado Geological Survey there are an estimated 23,000 abandoned mines in the state. Prior to 1977, almost no laws existed in the country that required reclamation of the mines, and no closing procedures were in place. These old mines pose a risk, especially when it comes to water quality.

Eagle County was reminded of our mining history in 1984, after pumps draining the Eagle Mine near Red Cliff were shut off, allowing the mine to flood. As water from snowmelt and rain filled the mine, it dissolved zinc, copper, cadmium, and other heavy metals from the rock. Once the mine completely filled, heavy metal-laden water overflowed into the Eagle River.

The spill turned the river orange and it became uninhabitable by many fish species. Zinc coated the gills of fish, making it impossible for them to breathe. The State of Colorado filed notice and claims against the former mine operator and had the 256-acre mine listed on the National Priorities List as a Superfund site, therefore launching the cleanup process.

During a recent Eagle River Watershed Council tour of the Eagle Mine, representatives from the Environmental Protection Agency, Colorado Department of Public Health & Environment, and Ramboll, the wastewater treatment plant operator, told participants about restoration efforts in the area and how much progress has been made.

One of the efforts highlighted was the dramatic restoration of a former tailings pond back to the wetlands we see on the west side of Tigiwon Road. The contaminated waste, along with roaster piles and other waste rock that had the potential for acid generation around the site, have been consolidated to an engineered pit and capped with vegetation.

This prevents runoff from mixing with the waste, but also captures any groundwater that may come in contact with the tailings for treatment. The treatment facility, which also receives any water that has come in contact with contamination in the mines, is located just south of this pile. Taking up a relatively small building, the industrial treatment operation has a big job to do, removing 178 pounds of metal from the water per day, and returning 100 million gallons of clean water to the river each year.

Perhaps the most interesting part of the tour was the Eagle Mine Site at Belden, where many participants were wide-eyed and intrigued as they learned about cribbing walls keeping waste rock from entering the river and modern monitoring systems juxtaposed with abandoned buildings. It is here that many of the roaster piles were located, right on the banks of the Eagle River.

Eagle River Watershed Council and other local partners continue to push for real-time monitoring of the site, to warn us of any potential problems or spills in the area. We are pleased to have trust and open dialog with the EPA, CDPHE, the mine owner and its contractors.

Though much has been done and immediate threats to human health and the environment have been mitigated, the cleanup of this mine site and treatment of its contaminated water will go on in perpetuity, as will our need to closely monitor and support the success of cleanup efforts

The Eagle Mine and its surrounding areas are private property and a Superfund Cleanup site. Please respect this and do not trespass on the property.

James Dilzell is the education and outreach coordinator for Eagle River Watershed Council. The Watershed Council has a mission to advocate for the health and conservation of the Upper Colorado and Eagle River basins through research, education, and projects. Contact the Watershed Council at (970) 827-5406 or visit

This article ran in the Vail Daily on September 11, 2019