EPA Narrowly Avoided Fatalities in Gold King Mine Spill Blowout, Internal Review Finds

08_10_2015_Gold King Mine EPA Animas River Spill
Yellow mine wastewater is seen at the entrance to the Gold King mine in San Juan County, Colorado, in this photo released by the U.S. Environmental Protection Agency and taken August 5. EPA/Reuters

An internal review of the U.S. Environmental Protection Agency's actions found that the agency failed to estimate the potential volume of toxic wastewater stored in the abandoned Gold King mine before beginning the work that eventually led to a 3 million gallon spill earlier this month. In a report released Wednesday, the EPA's review team (made up of EPA personnel from across the agency) writes that the agency failed to test for pressure buildup at the mine and narrowly avoided the death of crew members during the event.

In addition, the review team was unable to find any existing guidelines or procedures for assessing highly pressurized buildup of waste inside mines such as Gold King.

The EPA's original work plan for Gold King mine noted that it was possible the mine wastewater might be highly pressurized. The work plan warned, "Conditions may exist that could result in a blowout of the blockages and cause a release of large volumes of contaminated mine waters and sediment from inside the mine, which contain concentrated heavy metals."

Yet "experienced professionals" from the EPA and the Colorado Division of Reclamation, Mining and Safety determined that there would be "no or low" pressurization inside the adit section of Gold King mine—a passage that leads into the mine for "purposes of access or drainage," according to the EPA—based in part on the fact that this part of the mine was already steadily leaking liquid, reducing the possibility of buildup of pressure.

But despite evidence to the contrary, "there was, in fact, sufficiently high pressure to cause the blowout," the report reads. Underestimating buildup of pressure in the adit was a critical misstep and "the most significant factor relating to the blowout."

Had EPA workers used a technique to measure pressurization, as they did at other, abandoned hard-rock mines nearby, they would have known about the pressure buildup at Gold King, the report notes. But the testing technique, which involves drilling a hole into the area from above, "would have been quite costly and require much more planning and multiple field seasons to accomplish."

"Site specific conditions may make certain investigative tools prohibitive or extremely challenging and costly," the EPA writes, though it does not explicitly point out whether high cost was the reason the agency chose not to drill-test Gold King mine.

In addition to underestimating water pressure at Gold King, the EPA failed to evaluate the volume of water stored within the mine, the report notes. "It is not evident that the potential volume of water stored within the Adit had been estimated," the report reads. "Given the maps and information known about this mine, a worst case scenario estimate could have been calculated and used for planning purposes."

Still, given a review of the available information and interviews with crew members involved in the blowout, the report finds that the EPA spill was "likely inevitable."

"It's important to recognize that underground mines may be extremely complex, making characterization of the internal hydraulic conditions and flow paths challenging," the report says. "In the end, while additional information gathering may reduce the uncertainty, a complete understanding of the underground conditions may not be attainable."

And on the positive side, "actions taken by the EPA OSC [on-scene coordinators] to pull out the site personnel and crew from and near the Adit, just prior to the blowout, probably avoided any fatalities from the pressurized Adit blowout."

The U.S. Department of the Interior is in the process of conducting its own, separate investigation into the spill. Results of that inquiry are expected to be released to the public within two months.