The results of a federal investigation released Thursday shows that the Environmental Protection Agency could have easily prevented the toxic spill it caused this summer in Colorado, by making the mistake of not using a common method for gauging the risk of a major spill.

"Although this was apparently considered at Gold King, it was not done," the Department of Interior's investigative report reads. "Had it been done, the plan to open the mine would have been revised, and the blowout would not have occurred."

The Aug. 5 spill released 3 million gallons of toxic sludge that sullied the waterways of three states after the EPA tried to clean up the abandoned Gold King Mine in Colorado. The Department of Interior started an independent review of the spill, the results of which were issued Thursday afternoon.

The investigation found that if the EPA would have used a method similar to one used at a nearby mine, where a spill did not occur after its use, it would have revised its clean-up plan and the spill would not have happened at Gold King.

The method involves drilling a small hole above the opening of the mine to assess whether a safe level of pressure exists or if opening the mine would cause a significant "blowout."

"The incident at Gold King Mine is somewhat emblematic of the current state of practice in abandoned mine remediation," which is focused on "environmental issues" and does not apply the engineering rigor required to tackle the complexity of the problems with abandoned mines, the report reads.

"Abandoned mine guidelines and manuals provide detailed guidance on environmental sampling, waste characterization, and water treatment, with little appreciation for the engineering complexity of some abandoned mine projects that often require, but do not receive, a significant level of expertise," the investigation concludes, echoing statements by a number of lawmakers who have criticized EPA for not having the engineering expertise required for the jobs.

"In the case of the Gold King incident, as in many others, there was an absence of the following:

  • An understanding that water impounded behind a blocked mine opening can create hydraulic forces similar to a dam.
  • Analysis of potential failure modes.
  • Analysis of downstream consequences if failure were to occur.
  • Engineering considerations that analyze the geologic and hydrologic conditions of the general area.
  • Monitoring to ensure that the structure constructed to close the mine portal continues to perform as intended."

Republican lawmakers jumped on the report, calling for someone to be held accountable. "Literally and figuratively, the EPA blew it," said Sen. John Barrasso, R-Wyo.

"The government's own report directly refutes the EPA's claim that a toxic spill that caused 3 million gallons of toxic wastewater from the Gold King Mine to poison rivers in three states was 'likely inevitable,'" Barrasso said. "Responsibility for this disaster lands directly on the EPA's doorstep. I want to know who at EPA will be held accountable for this disaster."

In the House, there were calls for EPA Administrator Gina McCarthy to "terminate" the employment of all employees involved in the blowout. Rep. Rob Gibbs, R-Ohio, who led a hearing on the spill Wednesday, said the report showed EPA was out of its depth in Colorado and that "inexcusable incompetence" was to blame.

"It is clear from the [government] assessment that a failure in the system and inconsistent practices among government agencies involved are creating a hazardous and dangerous situation that is putting the drinking water of Americans at risk," Gibbs said.

"I call on Administrator McCarthy to terminate the employment of those responsible and immediately implement the recommendations of the report to prevent a similar spill from occurring in the future."

EPA spokeswoman Nancy Grantham tried to downplay the report. She said an EPA internal review team already evaluated the decision "not to use a drill rig to bore into the Gold King Mine from above and directly determine the level of the mine pool."

The review team "found that site conditions made it difficult to undertake such drilling to determine pressure within the mine," she said.

"The review team identified technical challenges, safety, timing and cost as factors in considering this technique — and also identified the steepness and instability of slopes at the site as a key safety consideration," Grantham said.