Hasty excavation without adequate technical info led to disastrous Gold King mine blowout in Colorado
By Bob Berwyn
Federal and state environmental engineers, along with their contractors, misjudged conditions inside the Gold King Mine before they unleashed a toxic flood of water into Cement Creek down the Animas and into the Colorado in early August.
The technical details about the spill were released this week by the Federal Bureau of Reclamation, which did an independent review of the accident. Most importantly, the workers underestimated the water level inside the mine. That error “resulted in development of a plan to open the mine in a manner that appeared to guard against blowout, but instead led directly to the failure,” the Bureau of Reclamation wrote in the report.What the EPA wanted to do was open the mine just enough to insert a drainage pipe, but when workers started clearing away the makeshift dam at the portal, the water pressure behind the debris overwhelmed the structure.
Bureau of Reclamation experts said the Gold King spill, which contaminated hundreds of miles of river with toxic sludge, could have been avoided if the EPA had drilled a test hole from above to accurately assess the water level — as had been done during remediation work at the nearby Bonita Mine.
Although this was apparently considered at Gold King, it was not done. Had it been done, the plan to open the mine would have been revised, and the blowout would not have occurred, the report concluded.
It’s also not clear why the EPA and its contractors started working on excavations at the Gold King Mine portal without waiting for technical input from the Bureau of Reclamation, as prescribed previously by the EPA project leader.
The Bureau of Reclamation report makes it clear that mine remediation work has, at some level, been a haphazard guessing game, with details in the executive summary:
“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. 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.
- An understanding of the groundwater system affecting all the mines in the area and the potential for work on one mine affecting conditions at another.
More such spills can’t be ruled out because there are so many other abandoned mines with similar conditions, the report concluded.