Anchorage, AK – Pebble Partnership (PLP) CEO Tom Collier issued the following statement about the U.S. Army Corps of Engineers (USACE) review of PLP’s approach to managing tailings at the proposed mine site and explains that the USACE decision about not needing a catastrophic failure analysis is sound because of the way PLP plans to design, operate and close its tailings facilities:
“There has been a lot of rhetoric pushed out to the public that the USACE’s review of tailings management for Pebble ignores critical comments raised during the comment window for the Draft Environmental Impact Statement. This is simply incorrect and frankly it is irresponsible. The USACE took the public input seriously and dedicated significant time and resources to this issue. The USACE held technical workshops with the cooperating agencies and sought additional technical information to conclude their work on the issue.
“The USACE reached their conclusion based upon the technical foundation for how the project intends to design, operate and close the tailings storage facilities at the mine site. We plan to manage the bulk tailings storage facility as a flow through system specifically designed to keep water from accumulating in the facility. Further, the primary water storage will be in facilities remote from the tailings storage facilities. These steps were taken in direct response to tailings storage facility failures at other locations which were found to be caused or exacerbated by the co-storage of water and tailings. These two major concept revisions represent a significant step change for our industry in the safe storage of tailings at a mine site. This is good news. The reason the document says it does not model the type of failure that occurred at Mt. Polley is that we designed the tailings facility at Pebble to prevent that type of dam failure from happening.
“From this, the USACE responded to concerns raised about the decision to not require a catastrophic failure analysis because they could not find a mechanism for this type of analysis based upon how we plan to run the facility. They did review plausible yet highly unlikely failure scenarios in their analysis.
“Here is a direct quote from the Executive Summary of the Preliminary Final Impact Statement produced by the USACE:
Tailings Dam Failure Scenarios
Modeling of an extremely unlikely tailings release was requested by commenters, but deemed inappropriate based on the Applicant’s permeable, flow-through design for the bulk tailings storage facility (TSF) main embankment compared with historical water-inundated TSFs that have been subject to large-scale failures. The comments and concern have been addressed in the FEIS by providing supplemental information in a new Appendix K4.27 to provide a detailed rationale on the probability of catastrophic tailings release from the bulk TSF. The discussion addresses several recent significant tailings dam failures (e.g., Brazil, Mount Polley), noting the higher probability of failure of water- inundated tailings slurries behind upstream dams compared to drained, thickened tailings behind downstream/centerline dams. Appendix K4.27 also provides a technical review of full dam breach models put forth by the US Environmental Protection Agency (EPA) and Lynker, which assume water- inundated TSFs, and describes the relevance of these models in the context of the proposed facility design.
“Just because some of the groups opposed to Pebble do not like the conclusions reached by the USACE does not mean that the USACE’s work is not valid. Rather, the USACE’s work on this issue is sound. It is defensible and it should be commended for its completeness.”