Study Shows Mine Failure Would Decimate Miles of Bristol Bay’s Largest Salmon Producing Rivers

By: Tyson Fick

Last Friday, as the public comment period on Pebble’s first federal permits opened, Dr. Cameron Wobus presented eye-opening findings from a Pebble Mine tailings dam failure analysis that have commercial fishermen, and many others, concerned about potential impacts of Pebble’s plan.

Dr. Wobus is a broadly trained earth scientist with approximately 15 years of experience in geomorphology, hydrology, and environmental data analysis and modeling. The study was developed after report scoping documents indicated that tailings dam failure scenarios were inadequately considered in the Army Corps of Engineers Draft Environmental Impact Statement (EIS), which is the often considered the most important document of the federal permitting process, and potentially the last chance for the public to weigh in.

Using a broad range of potential results from 12 to 96 hours duration and a total material release range from 10 percent to 60 percent of the mine tailings held in the pond, the results were uniformly awful.

In all scenarios analyzed by Dr. Wobus and his team, a tailings dam failure at Pebble would directly impact hundreds of miles of anadromous (salmon) waters in the Bristol Bay region.

The final report is expected in the next couple of weeks and will be submitted as part of the public record in the ongoing comment period. 

A realistic assessment of the impacts of a tailings dams failure is one of several areas of concern, but one that deserves more study. The Draft EIS only considers the possibility of a small break in a pipeline in the dam, one that would be fixed in 6 hours, and only during the supposed 20-year life span of the mine, though we know Pebble intends to ultimately undergo a much larger project. 

However, Dr. Wobus showed data from dam failures over the last 50 years that show them to be much more dramatic than a small pipeline break, as releases tend to be massive and sudden. Not to mention the fact the tailings dam would remain holding back toxic sludge forever - long after mining operations have ended. The spill scenario considered by the Corps is 10,000 times smaller than what the data suggests would be more realistic, and the likelihood of dam failure goes up dramatically over time.    

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The claim of Pebble mining only for a 20-year lifespan is difficult to take seriously. It is hard to believe investors in Pebble would be OK with the company making such a huge investment only to walk away with 90% of the ore still untouched. However, a longer lifespan significantly increases the risk.

Seeing obvious flaws and general inadequacy in a rushed and hushed scramble to push permits for the proposed Pebble mine upon skeptical Alaskans, fishermen from Bristol Bay are looking to top scientists to answer the many questions left unaddressed in the permit review process. Given Dr. Wobus’ presentation, an obvious concern is the risk of a tailings dam failure destroying the Nushagak River system, the very river that produced the largest return in recorded history last summer.

Handout picture released by the Minas Gerais Fire Department showing an aerial view taken after the collapse of a dam, which belonged to Brazil’s giant mining company Vale, near the town of Brumadinho in southeastern Brazil, on January 25, 2019. (Photo by HO / Minas Gerais Fire Department / AFP) /

Handout picture released by the Minas Gerais Fire Department showing an aerial view taken after the collapse of a dam, which belonged to Brazil’s giant mining company Vale, near the town of Brumadinho in southeastern Brazil, on January 25, 2019. (Photo by HO / Minas Gerais Fire Department / AFP) /

Obviously, the idea of a disaster like we have recently seen in Canada and Brazil in is terrible. We need to ensure this risk is never posed in Bristol Bay. Or at the very least, its chances acknowledged and planned for by Pebble.

Worse, a tailings dam failure is only one of dozens of areas where the Draft EIS is inadequate. You can expect to hear more from expert scientists in the coming weeks and months that will expose the many ways the federal permitting agencies have failed and why they need to go back to the drawing board with this mess.  

Link to Dr. Wobus’ presentation: https://bit.ly/2tUmYhs

Facebook Live stream of his presentation: https://bit.ly/2IWy3cj