How Did the August 2015 Release from the Gold King Mine Happen?

On August 5, 2015, EPA was conducting an investigation of the Gold King Mine near Silverton, Colorado, to:

  • assess the on-going water releases from the mine,
  • treat mine water, and
  • assess the feasibility of further mine remediation.

While excavating above the old adit, pressurized water began leaking above the mine tunnel, spilling about three million gallons of water stored behind the collapsed material into Cement Creek, a tributary of the Animas River. 

None of the workers at the site at the time of the breach was harmed.

Based on the size of the adit, we initially estimated that the release contained approximately one million gallons of water that had been held behind unconsolidated debris near an abandoned mine portal.  On August 8, the U.S. Geological Survey measured increased flows for several hours using a stream gauge, an instrument that measures volume by measuring flow, which is much more precise.  This measurement resulted in a provisional calculated flow volume of 3,043,067 gallons discharged from the Gold King Mine.

The large pulse of water dissipated in about an hour.  The water in Cement Creek and the Animas River in Silverton continues to clear.