EPA’s Office of Research and Development (ORD) is providing stakeholders with in-depth technical briefings on the Gold King Mine Project’s updated draft Fate and Transport Analysis. The project’s objectives were to examine how much material was generated in the August 2015 release, determine where that material went within the Animas and San Juan River systems, and evaluate potential future impacts that could occur if these materials are mobilized during high flows.

The project’s key findings:

• The research showed that elevated dissolved metal concentrations in the Animas River returned to pre-event background levels soon after the plume passed.
• Researchers estimate that the additional load of metals from the GKM spill was roughly equivalent to one day’s worth of high spring runoff of AMD discharges into the Animas River from all existing AMD sources in the Animas River watershed.
• In addition, groundwater modeling suggests that the wells located in the floodplain within a 100 meters of the Animas River had the potential to draw river water, possibly including dissolved metals, during the time the GKM release plume passed.

The agency is now seeking additional review from states, tribes, local governments and stakeholders. Comments can be submitted through August 12. The agency expects to finalize a final report this fall.

States, tribes, local governments and stakeholders can submit comments or requests for individual meetings to Carol Sanders at sanders.carola@epa.gov or 919-541-2106.

Stakeholders had the opportunity to attend four webinars to better understand the analysis before submitting comments. The webinars will also help states, tribes, and others understand the potential impacts during the current snowmelt and will help to inform the EPA-funded monitoring programs that agencies are designing and implementing in the river systems.

• The first webinar took place June 21 and discussed NERL’s and ORD’s research approach, the data collected, and the volume and characteristics of the acid mine drainage from the release. View presentation. View presentation revised with input from stakeholder webinar participants.
• The second webinar took place June 22 and covered the release’s plume characteristics and travel time in the Animas and San Juan Rivers, geochemical transformations, water quality during plume travel, and exposure potential. View presentation.
• The third webinar took place June 29 and presented an accounting for metals mass in the Animas and San Juan Rivers, post-release event trends in water and sediment metal concentrations, and potential mobilization of deposited materials during storms and snowmelt. View presentation.
• The fourth webinar took place June 30 and addressed groundwater modeling of potential for contamination of wells in the San Juan and Animas river alluviums. The webinar also included a wrap-up and summary discussion and time for questions. View presentation.

To inform this project, EPA researchers analyzed publicly available water quality and hydrologic data to characterize the release, transport, and fate of approximately 3 million gallons of acid mine drainage (AMD) accidentally released from the Gold King Mine (GKM) on August 5, 2015. The agency today posted a table linking to the data and models used to develop the draft Fate & Transport Study. View the table.

• Introduction. Data and Research Approach to Analyzing the Volume and Characteristics of the Aug. 5, 2015 Gold King Mine Release (PDF)(53 pp, 5 MB)
• Gold King Mine Plume Characteristics, Geochemical transformations and Potential Exposure Modeling (PDF)(63 pp, 4 MB)
• Session 2: GKM Plume Travel and Water Quality - Revised with stakeholder input (PDF)(63 pp, 3 MB)
• Fate & Transport Study – Source Data and Models (PDF)(4 pp, 81 K)
• Session 3: Analysis of Fate and Transport in the Animas and San Juan Rivers (PDF)(53 pp, 4 MB)
• Session 4: Analysis of Fate and Transport in the Animas and San Juan Rivers (PDF)(45 pp, 10 MB)