By Jolie Breeden

Big Spill: In August, an especially colorful example of the hazards of hard-rock mining emerged when three million gallons of toxic wastewater from an abandoned mine gushed into the Animas River in Colorado.

The event called attention to the threat to water supplies from abandoned mines nationwide. The Colorado Bureau of Land Management has counted 2,751 abandoned hard-rock mines on the state’s public lands and there could be as many as 550,000 across the country.

These unmaintained and sometimes forgotten properties fill up with water from various sources, which then mixes with the minerals and heavy metals such as cadmium, arsenic, and lead. The result is great reservoirs of toxic, acidic fluid known as acid-rock or acid mine drainage.

Often, this contaminated concoction leaks slowly into surrounding water supplies, while larger discharges are held at bay by concrete bulkheads installed by mine owners.

The August spill was caused when the U.S. Environmental Protection Agency accidently breached a bulkhead in a cleanup attempt at the Gold King Mine near Silverton, Colorado.

Holding the Bag: Although the EPA is often responsible for the clean up operations on such properties, a recent report by engineers at the U.S. Department of the Interior found that the agency isn’t well prepared to deal with the complexity of abandoned mining operations.

“The EPA does not adequately ‘analyze the geologic and hydrologic conditions of the general area’ or comprehend how, in a region honeycombed with tunnels, changing conditions in one affect the others,” according to a New York Times article on the report.

In the instance of the Gold King Mine, for example, the EPA was unprepared for the pressure of the water behind the bulkhead. According to the report—which was an independent inquiry into the EPA’s role in the incident requested by the agency—a test hole should have been drilled from above to gauge mine conditions and release any pressure.

The EPA’s own investigation in the matter maintained that the bulkhead would have eventually failed regardless and that the release of toxic waste was inevitable. The agency hasn’t yet commented on the Interior’s findings.

Getting Clean: While the EPA may lack the engineering expertise to mitigate mine waste, the agency is still the best—and often only—hope of cleanup for communities threatened by mines that in many cases have been abandoned for decades. That could change, however.

Congressional leaders are still working on the Hardrock Mining Reform and Reclamation Act of 2015 which would establish royalties on new and existing hard-rock mines to create a fund to address abandoned mine cleanup. Communities, too, are taking the matter into their own hands. Most recently, an advocacy group from Crested Butte, Colorado, filed a federal lawsuit asking the court to require owners of a nearby mine to assure that a wastewater treatment plant will be perpetually maintained.

In addition to those efforts, Western governors are also trying to address the problem. But with the responsibility for the polluted mines reaching back to the Gold Rush era, it’s difficult to firmly hold current owners accountable. The breadth of mines needing attention is also an issue, said Colorado Gov. John Hickenlooper.

“These are all conditions that were created by previous generations,” Hickenlooper told the Denver Post. “And there's a resistance to the present generation wanting to pay for it—because it is expensive. [Western governors] are looking at that, and looking at how do we cobble together some local funding and some federal funding? What would that look like? And what timeline is reasonable? How do you prioritize what comes first?”