The Environmental Protection Agency typically responds to disasters caused by private interests; it doesn’t cause them. So the agency finds itself in an unusual position of accepting blame for the release of 3 million gallons of toxic mine water polluting the Animas River.

Why was the EPA conducting cleanup work in the Gold King Mine rather than having the mine owner do the work?

Craig Myers, coordinator for the EPA’s emergency response and preparedness team, said the EPA was assessing the environmental damage at the mine. The assessment was to be used to order the necessary cleanup work by the private company.

As water percolates through the mountain from rain and snowmelt, it takes the path of least resistance, which tends to be abandoned mine shafts. But that gives mineral-rich water an easy way to escape the ground and make its way into above-ground waterways.

One way to prevent seepage is to create bulkheads, a retaining wall that prevents the water from entering the shaft. But with multiple mine shafts in a mountain, several bulkheads may be needed to prevent water from infiltrating each one. Build enough bulkheads to the top of the mountain, and water no longer seeps in.

In the Gold King Mine, one tunnel collapsed, creating a cavern of water. The EPA was trying to assess the enclosure and determine how to relieve water seeping from the mine.

Trapped water put pressure on the blockage, and doing nothing – or letting it sit – could have caused a natural blowout.

Instead, the EPA drilled a hole to open the mine. But there was far more water and pressure than anticipated.

Said Myers: “There aren’t many other federal agencies that have this expertise. We do this a lot. We have the knowledge to do it. We have the knowledge of how to assess the river and the capabilities to do it.”