About the TMM project
Twin Metals Minnesota (TMM) proposes to develop an underground mine and associated processing facilities for the extraction of copper, nickel, cobalt, and platinum group metals (PGMs) in northeastern Minnesota.
The proposed TMM project includes:
- The proposed TMM project would be located in Lake County, approximately 9 miles southeast of Ely, Minnesota.
- The proposed mine would be located within the Rainy River watershed.
- Ore would be mined from Duluth Complex rock in an area known as the Maturi deposit.
- Ore from the Maturi deposit would be mined using conventional underground methods, including blasting and excavation, with mine waste rock backfilled underground.
- Throughout the life of the project, half of the tailings would be deposited in mined-out underground areas of the mine; the other half would be placed in an above-ground dry stack tailings facility at a separate, nearby location.
- The proposed aboveground dry stack tailings facility would include a liner installed under the tailings.
- A stormwater collection system would collect and manage precipitation at the project site.
- An estimated 20,000 tons of ore would be processed each day over a permitted operational life of 25 years.
Environmental Review Process
The proposed TMM project requires preparation of a mandatory state environmental impact statement or EIS. The EIS evaluates a project’s potential significant environmental effects and discloses that information to project decision-makers and the public. The DNR is the responsible governmental Unit or RGU, and will serve as the lead agency in completing the state EIS. The EIS identifies possible project alternatives, and considers ways to avoid, minimize, or mitigate significant environmental impacts. Information gathered through the EIS will help inform the project design and decisions about permits and other approvals the project would require to proceed to construction and operation.
Current Phase – EIS Scoping
The focus and content of an EIS varies from project to project, and is determined during scoping, the initial phase of an EIS process. During this phase, the RGU prepares a scoping environmental assessment worksheet (Scoping EAW) and draft scoping decision document. The public is then asked to review and comment on both of these documents. Public scoping for the TMM project will include at least one public meeting.
DNR’s Environmental Review page »