Facts about Pebble’s proposed mine

My brother once told me, “You have your facts, I have my facts.” Not so. Facts are facts. Since deciding to file for one of its major federal permits, currently being reviewed by the U.S. Army Corps of Engineers, the Pebble Limited Partnership has made some undocumented claims about the impacts potential failures could have at its proposed mine site in important headwaters of Bristol Bay.

I would like to share some discrepancies I have noted in the “facts” about Pebble.

At a Resource Development Council meeting in 2017, the Pebble partnership asserted that their new, “smaller” mine plan is “within the ballpark” of a size the Environmental Protection Agency would approve. In reality, the new, “small” mine plan proposed by Pebble is approximately 25 percent larger than the small mine the EPA analyzed. Regardless, the EPA said in its 2014 Proposed Determination that the habitat losses of even its small mine were unacceptable, making Pebble’s point moot.

At the same RDC meeting, Pebble representatives said, “Our engineers are convinced there will never be a failure at the Pebble tailings facility.” Similar statements were made by Pebble’s consultants, Knight Piesold, in 2014, suggesting there was no reasonable possibility a first-world tailings dam could fail, yet the Mount Polley tailings dam in British Columbia failed catastrophically later that same year due to a well-understood failure mechanism.

In a CNN interview earlier this year a PLP spokesman said, “If there is an accident, it will kill fish for about 20 miles down the North Fork of the Koktuli, and that’s it - and for 10 years. It’ll come back naturally.” However, with considerable scientific input, the EPA Watershed Assessment described the effects of a dam failure, even in a “small” mine scenario as, “The … tailings dam failures described in the preceding section could have devastating effects on aquatic life and habitat. (p. 9-20) … Deposited tailings and their leachate would persist at toxic levels for decades. The acute effects of a tailings spill would extend far beyond the modeled 30-km (18.6 mi) distance downstream. (p. 9-45)”

This is not the description of an impact lasting only 10 years.

The Mount Polley tailings dam failure is a preview for what could happen at Pebble, though the impacts at Mount Polley were considerably more limited than what we’d expect to see with a similar failure at Pebble. The dam that failed at Mount Polley is the same design, by the same company, as is planned at Pebble. However, dams at Pebble would be about four times as high and the tailings would not be stopped by a lake as they were at Mount Polley. They would continue to damage streams for tens of miles. Unlike Mount Polley, the escaped tailings at Pebble could be acid-generating - in other words, toxic. To imply that a catastrophic tailings dam failure would have minimal impact on the Bristol Bay salmon ecosystem is not only being highly presumptuous, it is contravening common sense.


I have been doing this type of work for almost three decades, and can remember a time when industry members seeking to build a project said, ‘Why don’t you tell us early in the permitting process that our mine will not pass the NEPA test? Then we can avoid spending a lot of time and money on a fatally flawed project.’ In the case of Pebble, that’s exactly what EPA did.

Contrary to what Pebble backers would like people to think, the EPA Watershed Assessment is a scientifically sound document, and by far the best assessment I have seen the EPA do to support 404(c) protections. Unlike the Watershed Assessment, the Environmental Baseline Document created by Pebble has not received formal peer review, so it’s easy for Pebble to make the claim that it’s great science.

Science is not adversarial, like arguments in a court of law. Science is not hyperbole, like media soundbites. Science is searching for factual evidence and evaluating those facts in a rational manner. I propose we look at the science on Pebble in that light.

David M. Chambers, Ph.D., P.Geop., works for the non-profit Center for Science in Public Participation, which is providing technical support for groups in opposition to the proposed Pebble Mine.

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