Dam Safety Permit | PolyMet's NorthMet Mining Project

On November 1, 2018, the DNR issued two dam safety permits for the Poly Met Mining, Inc. (PolyMet) NorthMet mining project. DNR's Dam Safety Permit Program is required to regulate the construction, operation and maintenance of dams to protect public health, safety and welfare. The DNR regulates the construction and enlargement of dams, repair, alteration, maintenance, operation, abandonment and transfer of ownership through the dam safety permitting process. Minnesota Rules establish minimum standards and criteria for dam classification and regulation. These cover both initial permitting and ongoing regulatory oversight. These actions are administered and monitored by the DNR Dam Safety Unit.

One dam safety permit covers the proposed flotation tailings basin, which will be located on the site of the existing tailings basin of the historic LTV iron ore mine and will receive tailings (a mixture of finely ground waste rock and water). The second dam safety permit covers the proposed hydrometallurgical residue facility, which will receive residue (mostly gypsum) generated from a process that will use pressure and temperature reactions to extract additional precious metals beyond what can be achieved by the primary processing facility.

Dam Safety Permits and Findings of Fact

Permit 2016-1380: Flotation Tailings Basin (1 MB) »
Permit 2016-1383: Hydrometallurgical Residue Facility (1 MB) »
Dam Safety Findings of Fact Permits 2016-1380 and 2016-1383 (2 MB) »

Permit 1981-2100: Tailings Basin Transfer (1 MB) »
Dam Safety Findings of Fact Permit 1981-2100 (1 MB) »

Historic Permitting Information

The NorthMet project requires two dam safety permits for various construction and operation activities at the plant site.

DNR and external consultant Emmons Olivier Resources, Inc. (EOR) completed a comprehensive review of the company's two dam safety permit applications. They also considered input from state, local and tribal governments.

DNR accepted written public comments on the draft dam safety permits from September 15, 2017 until October 16, 2017.