U.S. officials knew of the potential for a catastrophic "blowout" of poisonous wastewater from an inactive gold mine, yet appeared to have only a cursory plan to deal with such an event when a government cleanup team triggered a 3-million-gallon spill, according to internal documents released by the Environmental Protection Agency.
The EPA released the documents late Friday following weeks of prodding from The Associated Press and other media organizations. While shedding some light on the circumstances surrounding the accident, the newly disclosed information also raises more questions about whether enough was done to prevent it.
The Aug. 5 spill came as workers excavated the entrance to the idled Gold King Mine near Silverton, Colorado, unleashing a torrent of toxic water that fouled rivers in three states.
A June 2014 work order for a planned cleanup noted the mine had not been accessible since 1995, when the entrance partially collapsed.
"This condition has likely caused impounding of water behind the collapse," the report said. "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."
A May 2015 action plan produced by an EPA contractor, Environmental Restoration LLC, also noted the potential for a blowout.
The May plan also called for a pond that would be used to manage the mine water and prevent contaminants from entering waterways. That pond was not completed.
EPA spokesman David Gray said the document outlined steps that should have been followed but it would be up to pending investigations to decide if the pond should have been in place before the work started.
Much of the documents were redacted. Among the items blacked out was a line specifying whether workers were required to have phones that could work at the remote site, at an elevation of 11,000 feet.
A 71-page safety plan for the site included only a few lines describing what to do if there was a spill: Locate the source and stop the flow, begin containment and recovery of the spilled materials, and alert downstream drinking water systems as needed.
Colorado Attorney General Cynthia Coffman said after reviewing the documents that she remained frustrated with the EPA's lack of answers.
"The plan indicates there was an understanding of what might happen and what the potential consequences were. We don't know whether they followed the plan," Coffman told The Associated Press. "I want to give the EPA the benefit of the doubt here. I really want to do that. It's getting harder."
The wastewater flowed into a tributary of the Animas and San Juan rivers, turning them a sickly yellow-orange color and tainting them with lead, arsenic, thallium and other heavy metals that can cause health problems and harm aquatic life. The toxic plume traveled roughly 300 miles through Colorado, New Mexico and Utah, to Lake Powell on the Arizona-Utah border.
EPA water testing has shown contamination levels returning to pre-spill levels, though experts warn some of the contaminants likely sunk and mixed with bottom sediments and could someday be stirred back up.
The documents released at about 10:30 p.m. EDT Friday did not account for what happened immediately before or after the spill.
Elected officials have been critical of the EPA's response. Among the unanswered questions is why it took the agency nearly a day to inform downstream communities that rely on the rivers for drinking water.
Coffman criticized the "late Friday night document dump" and said the redaction of key facts would heighten public suspicions. She also indicated that it undercut EPA Administrator Gina McCarthy's statements accepting responsibility.
EPA spokeswoman Melissa Harrison said the agency has been inundated with media inquiries and worked diligently to respond to them. All information must go through a legal review, she added.
"I do not want people to think we put something out late at night to hide something," she said.
U.S. Rep. Lamar Smith, a Texas Republican who chairs the House Science Committee, said the EPA "has an obligation to be more forthcoming." He called for McCarthy to appear before his committee next month.
U.S. Sen. Cory Gardner, R-Colo., said it was unacceptable that the EPA did not prevent the accident when it knew of the massive quantities of contaminated water inside the mine.
Environmental Restoration has confirmed its employees were present at the mine when the spill occurred but declined to provide more detail, saying that would violate "confidentiality obligations."
The St. Louis, Missouri, company bills itself as the EPA's prime contractor for emergency services across most of the U.S.
The EPA has not yet provided a copy of its contract with the company. On a March 2015 cost estimate for Gold King, the agency blacked out all the dollar figures.
The emergency response to the spill has cost the EPA at least $3.7 million so far, according to the agency.
Toxic water continues to flow out of the mine. Since the accident, the EPA has built a series of ponds so contaminated sediments can settle out before the water enters a nearby creek.
The agency said more needs to be done and the potential remains for another blowout.