Dam safety amendment requested on existing taconite tailings basin
NewRange Copper Nickel (formerly PolyMet Mining) has applied for a dam safety permit amendment to modify an existing inactive LTV Steel Mining Company taconite tailings basin to enhance safety of that dam. NewRange has responsibility for managing the tailings basin under a permit issued in November 2018.
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 applicant intends to construct a new spillway at the top of the existing inactive tailings basin, add coarse tailings fill to keep water away from the edge of the dam, and construct a rock-lined channel directing any water that leaves the spillway to an existing storage pond.
The tailings basin has an existing water management structure that is no longer functional. Adding the spillway/diversion ditch and adding fill to keep water away from the dam would improve dam stability by preventing ponded water from encroaching upon the perimeter dam during extreme precipitation events.
The proposal does not expand the capacity or increase the footprint of the existing tailings basin. If approved, 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. With the existing water management structure no longer in use, the only way for excess water to leave the cell is to flow over the embankment and down a roadside ditch to another tailings basin cell. The proposal would upgrade the tailings basin to comply with Global Industry Standard on Tailings Management (GISTM) that represents the most recent industry safety standards.
The DNR has a prescribed process for review of dam safety permit amendments that includes a 30-day government agency comment period. Comments on this application will be accepted from local governments, the Minnesota Board of Water and Soil Resources, the US Army Corps of Engineers and the Fond du Lac, Bois Forte and Grand Portage Tribal Nations until 4:30 p.m. Monday, March 3, 2025.
DNR dam safety technical experts will consider any comments provided as part of its technical review of the proposal. The DNR will need to determine that the proposal meets the regulatory requirements for dam safety in order to issue the amendment.
For additional information or to sign up for email updates on this proposal as well as the NorthMet Mining project please visit the DNR’s webpage.
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