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.”
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.
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.”
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:
This 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.
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.”
This email chain between Minnesota DNR engineers, Army Corps of Engineers, and PolyMet contractors ERM and Barr Engineering show that years ago, DNR employees were raising concerns about large rain events, earthquakes and dam construction techniques could results in a dam failure costing “tens of millions of dollars.” Screenshots here.