Om Friday, the U.S. Environmental Protection Agency (EPA) posted the final fate and transport report for the Gold King Mine (GKM) release. The report focuses on understanding pre-existing river conditions, the movement of metals related to the GKM release through the river system, and the effects of the GKM release on water quality. The research supports EPA’s earlier statements that water quality in the affected river system returned to the levels that existed prior to the GKM release and contamination of metals from the release have moved through the river system to Lake Powell.
The area affected by the Gold King Mine release consists of complex river systems influenced by decades of historic acid mine drainage. The report shows the total amount of metals, dominated by iron and aluminum, entering the Animas River following the release — which lasted about nine hours on August 5, 2015 –was comparable to four to seven days of ongoing GKM acid mine drainage or the average amount of metals carried by the river in one to two days of high spring runoff. However, the concentrations of some metals in the GKM plume were higher than historical mine drainage. As the yellow plume of metal-laden water traveled downstream after the release, the metal concentrations within the plume decreased as they were diluted by river water and as some of the metals settled to the river bed.
There were no reported fish kills in the affected rivers, and post-release surveys by multiple organizations have found that other aquatic life does not appear to have suffered harmful short-term effects from the GKM plume. The concentrations of metals in well-water samples collected after the plume passed did not exceed federal drinking water standards. No public water system using Lake Powell as a source of drinking water has reported an exceedance of metals standards since the release.