“…the proposed wet cap will significantly increase the potential for a dam failure …”

This 2012 memo from Dana Dostert (DNR Dame Safety) to DNR Lands and Minerals (LAM) and the Army Corps of Engineers (COE), identifies the “wet cap” closure that PolyMet is proposing for the tailings basin as a significant concern. “Dam Safety has numerous concerns with this project because the tailings dams must function properly for an extended period of time – we’ve heard on the order of 900 years.”

“… a tendency to describe the kind of things that could be done rather than a commitment to do specific things.”

This file is a 2012 review of the Flotation Tailings Basin Management Plan by outside consultants (DS = Don Sutton, Spectrum Engineering, CO = Cecilio Olivier, EOR). Note that 5 years ago, DNR consultants were raising red flags about the way plans like this one were not requiring PolyMet to do anything and making it clear that they need to be changed if they would be used as part of a permit. Five years later, the DNR issued a draft permit to mine that continues to commit this error – incorporating plans that are permissive and descriptive, rather than prescribing requirements.


“The Hydrometallurgical Residue Facility is a concern for fisheries”

This comment from a DNR Area Fisheries Supervisor was filed on the PolyMet draft dam permits and pertains to the “hydrometallurgical residue facility,” which is where the most toxic waste from the PolyMet processing plant would be permanently stored. As it notes, this would be a lined facility that is supposed to be capped after closure. As noted “even if it takes 200 years, the waste will still be there and in its location would be very susceptible to leaching into nearby wetlands and groundwater.” TFA comments_ RFC 2016_1383 and 1380

DNR Consultant: Bentonite clay seal of waste dam “Hail Mary type of concept,” “wouldn’t be allowed in other jurisdictions.”

This memo from Spectrum Engineering, a DNR consultant, takes issue with several aspects of the mine waste stockpile and dam plans. It raises concerns about climate change impacts on the stability of the PolyMet waste dam proposal. Also, it notes that permitting a temporary earthen dam for permanent use “wouldn’t be allowed in other jurisdictions.” Screenshot below: Spectrum Memo 2012

DNR Consultant: Amount of water and cost will be lowballed, “good luck getting anything after mining ends”

Sutton Good Luck Getting Money After ClosureThis October 2012 email from Donald Sutton of Spectrum Engineering, a DNR consultant, is about the cost and feasibility of perpetual water treatment after closure. His conclusion is that the plan to perpetually treat water will require expensive repairs and he cites the experience of the Zortman and Landusky mines in Montana – one of the worst examples of taxpayers being stuck with perpetual cleanup costs. Full email chain below. Sutton - 'good luck getting anything after mining ends'

PolyMet Mine Waste Dam Requires 900 Years of Maintenance – “a major leap of faith”

Sutton Major Leap of Faith Cover

This 2012 email exchange is between Don Sutton, a Montana mine engineering consultant working with DNR and DNR employees, two employees of Knight Piesold, and the U.S. Army Corps of Engineers. In it Sutton states that PolyMet’s plan for “wet closure” of mine waste behind a highly erodible earthen dam will fail without perpetual maintenance, which he says requires “a major leap of faith.”