Peer review comments on EPA’s fate and transport study

The U.S. Environmental Protection Agency released two peer review documents related to the agency’s draft “Gold King Mine Analysis of Fate and Transport in the Animas and San Juan Rivers.” The analysis is now undergoing stakeholder review and is slated for release later this year.

For the draft analysis, 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 Aug. 5, 2015. 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. A presentation regarding the preliminary analysis is available here.

As part of EPA’s standard practice, the agency sought an external and independent review of its analysis through a peer review.The external peer review of the draft analysis included experts in geochemistry; metal toxicity; groundwater modeling; fate and transport of metals in water and sediment; and the Water Quality Analysis Simulation Program (WASP).

The Peer Review Summary Report of EPA’s Gold King Mine Analysis of Fate and Transport in the Animas and San Juan Rivers includes a summary of the peer reviewers’ responses to charge questions.

EPA responded to every comment provided by the peer reviewers. The responses are available in EPA’s Response to Peer Review Comments.

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