EPA Releases Gold King Mine Fate and Transport Report

Wed Feb 22nd, On Environmental Law, by

The U.S. Environmental Protection Agency (EPA) completed its fate and transport model and issued a report for the Gold King Mine release. The report focuses on pre-existing river conditions, the movement of metals through the river system, and the effects of the metals on water quality.

The mine had a catastrophic release of acid mine draining, including high levels of iron and aluminum, into the Animas River system.  The release was a result of an EPA field investigation at the mine, where water had been dammed by a collapsed mine structure and rock at the mine entrance. The blockage caused the waters to back up and become pressurized. On August 5, 2015, the water overtopped and broke through the makeshift dam, causing an estimated release of 3 million gallons of acidic, mine-impacted waters into the Animas River.

In the modeling report, EPA looked at: (a) the mine’s effects on water quality after the release; (b) whether or not the water quality returned to pre-event conditions; (c) whether or not there was a second wave of contamination following storms and/or spring snow melt when high flows could remobilize deposits; and (d) whether or not any remaining Gold King Mine impacts could be detected given the legacy contamination from historic mining in the region.

The Findings Noted in the EPA’s Report

EPA’s report found that water quality in the river system has now returned to pre-event levels and any contaminants released from the Gold King Mine have moved through the river system to Lake Powell. The report also finds that metal concentrations within the river after the release decreased due to dilution by river water and as some of the metals settled to the river bed. In addition, according to EPA’s report, fish and other aquatic life did not suffered harmful short-term effects from the release. In addition, EPA found that public water systems in the area were not impacted. Approximately 90 percent of the solid metal load from the release settled in the Animas River bed as part of the sediments.

EPA downplayed the exceedances of state and tribal water quality criteria at after the release and during the spring 2016 snow melt asserting the exceedings included longstanding contributions of metals from historic mining activities in the region and natural levels of metals in soils and rocks in the area.  

EPA may implement sediment monitoring in the Animas River and Lake Powell to assess long term effects and will work with States and tribal entities toward that end.  At this time, however, EPA has not identified any further response actions at the release site or downstream.

Our California natural resource lawyers note that EPA has taken a different approach to other contaminated sediment river sites across the country.  At many sites, EPA has rejected requests by potentially responsible parties to conduct long-term sediment monitoring to show the effectiveness of natural attenuation or natural remediation of contaminants in river systems. EPA could be setting a precedent for releases of metals in river system by finding that dilution and natural attenuation is appropriate in that setting.

For More Information:

Read the final report, “Analysis of the Transport and Fate of Metals Released From the Gold King Mine in the Animas and San Juan Rivers”: https://cfpub.epa.gov/si/si_public_file_download.cfm?p_download_id=530074

Read the report’s executive summary: https://cfpub.epa.gov/si/si_public_file_download.cfm?p_download_id=530075

More information on the Fate and Transport analysis: https://www.epa.gov/goldkingmine/fate-transport-analysis

More information on the 2015 Gold King Mine incident: https://www.epa.gov/goldkingmine

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