ST. PAUL, MN — The Minnesota DNR says they are denying requests by the Fond du Lac Band of Lake Superior Chippewa, as well as multiple environmental organizations and individuals, who requested the agency reconsider the tailings dam permits issued to PolyMet last year.
The DNR reviewed PolyMet’s tailings dam proposal for years, including models and independent review done by experienced DNR engineers, as well as nationally and internationally recognized dam safety experts.
According to the DNR, the requestors didn’t raise any new issues that would materially affect the agency’s decision to issue the tailings dam permits, and is confident the the permitted tailings basin dam, if properly built, operated and maintained, will be safe and protective of human health and the environment.
Sarah Strommen, the Commissioner for the Minnesota DNR, issued this statement regarding the decision:
“While we were confident in our original analysis of the PolyMet tailings dam, we have carefully examined the requests for reconsideration and related information about recent dam failures in other parts of the world. We understand people’s concerns with these dam failures and whether those events indicate a fundamental design issue with PolyMet’s dam. Our analysis demonstrates that there are significant differences in site conditions, engineering design, and operating requirements and we remain confident in the safety of the PolyMet tailings dam as permitted.”
DNR officials say dam safety experts evaluated claims including stability concerns, as well as the use of the ‘Olson Method’ to analyze strength and stability, which was used for the Brumadinho dam in Brazil that later failed.
According to the DNR, while both PolyMet and the Brumadinho dams include the use of upstream construction methods, there are differences which have to be understood and evaluated to draw technically valid comparisons and conclusions, and states the PolyMet permitted dam design is different and safer than the Brumadinho dam in the following ways:
- Safety factors for PolyMet dam were establised using assumptions to assess the basin’s stability under extreme conditions. The assumptions also include the entire basin had liquefied, had been exposed to extreme rainfall, and also gone through an earthquake. Analysis of the Brumadinho dam failed to include any of those factors.
- PolyMet’s dam will be built on flat topography, far from a community, and using a certain type of construction, unlike Brumadinho, which was built on a hillside and directly above a community.
- PolyMet’s dam will have a more gradual side slope compared to the Brumadinho dam
- The location of the PolyMet dam will be in an area of little or no seismic activity, while the Brumadinho dam is in an area of moderate seismic activity
- The Brumadinho dam was close to mine blasting sites, while PolyMet’s dam is about eight miles from the mine site.
More information regarding the DNR’s permit decision can be found by clicking here, or by scrolling below on a desktop device.