The Minnesota Department of Natural Resources (DNR) issued a dam safety permit amendment authorizing NewRange Copper Nickel (formerly PolyMet Mining) to make safety-related improvements to the existing inactive LTV Steel Mining Company taconite tailings basin.
Poly Met Mining is proposing a mine and associated processing facilities for the extraction of copper, nickel, and platinum group elements (PGE) in northeastern Minnesota. The mine would be the first of its kind in the state.
While this tailings basin is also the site of the proposed non-ferrous NorthMet mining project, the amendment request is not part of that project. The NorthMet project is currently on hold pending the result of legal challenges.
The amendment issued Tuesday permits the construction of a new spillway at the top of the existing inactive tailings basin, the addition of coarse tailings fill to keep water away from the edge of the dam, and the construction of a rock-lined channel directing any water that leaves the spillway to an existing storage pond.
Adding the spillway/diversion ditch and adding fill to keep water away from the dam will improve dam stability by preventing ponded water from encroaching upon the perimeter dam during extreme precipitation events. These new features will replace the existing water management structure at the tailings basin that is no longer functional.
This amendment does not expand the capacity or increase the footprint of the existing tailings basin. The project will increase stability of the existing embankments (tailings basin cells) by ensuring water is able to be channeled safely away during extreme precipitation events.
DNR dam safety experts met with representatives of the Fond du Lac Band of Lake Superior Chippewa and considered the Band’s comments as part of the DNR’s review of the NewRange amendment application. The DNR also considered all other comments received on the proposed amendment.
The DNR’s review of the proposed amendment determined that the planned construction meets all requirements of Minnesota’s dam safety laws and that it would increase the safety of the dam.
