The mine wastewater spill that turned two Colorado rivers into a mustard-yellow broth of heavy metals was "likely inevitable," but inspectors had no sign it was imminent, the US Environmental Protection Agency (EPA) reported Wednesday.
The team working to clear debris from the opening saw only small amounts of water escaping from the Gold King Mine before the August 5 accident, an internal EPA report concluded.
"But there was in fact high enough water pressure to cause a blowout," EPA Deputy Administrator Stan Meiburg told reporters in releasing the report. "Expensive and technically difficult" drilling could have detected that high pressure, Meiburg said.
"However, professionals on the ground from the EPA and the state of Colorado did not have evidence to suggest this technique would be necessary," he added.
The blowout sent 3 million gallons of acidic water laced with lead, cadmium, arsenic, and other heavy metals into nearby streams that feed the Animas and San Juan rivers, which ran a vivid orange-yellow for several days as the tailings washed downstream.
The EPA has come under heavy criticism from conservationists, elected officials, and the Navajo Nation since the spill, not only for the accident itself, but for being slow to notify state, local, and tribal governments downriver about the blowout. Meiburg said EPA admits "that broader notification should have been done," and the agency will work to improve communications in the future.
Wednesday's report was the result of a weeklong investigation by a team of scientists and engineers who reviewed documents, interviewed witnesses, and visited the site, Meiburg said. Other investigations are under way by the agency's independent inspector-general and the Interior Department, he said.
Gold King is one of thousands of long-closed mines that dot the Colorado mountains. It's been closed for decades — but in the past few years, the groundwater level near the mine had started to rise, causing the water to back up and drain through interconnected groundwater channels. The EPA team was working to contain the seepage between Gold King and another mine when the accident occurred.
The report praised the crew at the mine site for responding quickly in the 3-4 minutes before the initial spurt of water from behind the rock face became a torrent — possibly saving lives in the process. But the crew lacked an emergency plan for that possibility, it found. And because the water pressure in the mine entrance was higher than expected, "the precautions that were part of the work plan turned out to be insufficient."
"The inability to obtain an actual measurement of the mine water pressure behind the entrance blockage seems to be a primary issue at this particular site," the report states. "If the pressure information was obtained, other steps could have been considered. However, the Team cannot determine whether any such steps would have been effective, or could have been implemented prior to a blowout."
Water is still pouring out of the mine, but it's being diverted into a series of ponds, Meiburg said. It's being treated there to reduce its acidity and allow heavy metals to settle.
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