Potential Sulfide Mines

Minnesota’s three primary watersheds – the Lake Superior, Rainy River (Boundary Waters) and Mississippi River Basins all face threats from sulfide mining. The PolyMet (Glencore) NorthMet copper-nickel mine in the Lake Superior watershed is Minnesota’s first proposed sulfide mine. Other sulfide mines are planned for the near future in the Boundary Waters and Mississippi River watersheds.

Other than PolyMet, the Twin Metals project is the only mine that has submitted a mine plan to Minnesota regulators. Although the Twin Metals mine is currently proposed as an underground mine, its economic feasibility as a small underground mine is uncertain. Former state regulators caution that mines often begin underground, but expand to open pit mines when economic conditions threaten closure if expansions are not permitted. An open pit mine is shown below.

The Flambeau open pit copper sulfide mine in Ladysmith, Wisconsin. Photo by Rick Wood/Milwaukee Journal Sentinel.

Twin Metals (Antofagasta) Mine

On December 18, 2019, Twin Metals Minnesota, a wholly-owned subsidiary of Chilean mining giant Antofagasta, submitted its mine plan for a copper-nickel mine on Superior National Forest lands in the Rainy River watershed on the edge of the Boundary Waters. The proposed Twin Metals mine would be located on the Kawishiwi River and Birch Lake, within three miles of the Boundary Waters Canoe Area Wilderness (BWCAW). All water from the proposed mine site would flow into the BWCAW.

Twin Metals property interest map (by Twin Metals)

Twin Metals’ current mine plan proposes mine facilities on 1156 acres of wetlands and forests (almost two square miles). Tailings would be stored on-site on 653 acres. The plan proposes that mining operations would be underground – from 400 to 4,500 feet below the surface, blasting with explosives adjacent to Birch Lake.

The mine would process 20,000 tons of ore per day, and approximately 40 to 60 percent of the mineral resource within the underground mine would be left in place to prevent mine collapse. Mine slopes are generally designed around a proposed cutoff grade of 0.4 percent copper. There is no feasibility analysis demonstrating that an underground copper mine with the low grade of copper at this location would be economically feasible.

Twin Metals location detail (Twin Metals Mine Plan Fig. 2-2)

Every unique resource of the Boundary Waters watershed and the BWCAW would be threatened by the Twin Metals mine, including rivers and lakes, groundwater quality, air emissions, wildlife, quietude, endangered species, and tribal cultural and historical resources. Watch a video showing what the Twin Metals mine plan could look like.

On June 15, 2020, the Minnesota Department of Natural Resources (DNR) concluded that Twin Metals’ initial submittal for environmental review was incomplete.

Tamarack (Kennecott/Rio Tinto/Talon) Mine

The Kennecott/Talon mine project is in advanced stages of exploration in Aitkin and Carlton Counties centered around Tamarack, Minnesota. Kennecott is a division of global mining company Rio Tinto and Talon is a joint venturer with Rio Tinto. This potential mine poses a unique threat because the area being explored is a massive sulfide mineralized zone bearing concentrated copper, nickel, and cobalt ore (with recoverable platinum, palladium, and gold as well). Rich ore zones have been discovered 1300-1600 feet underground over an 11-mile north-south strike.
Nearly 90,000 acres of state-owned mineral rights have been leased for this potential mine in the water-rich Tamarack area. The Kennecott/Talon mineral leases are located on a major watershed divide at the headwaters of the Kettle River, which flows to the St. Croix River, and the Tamarack River, which flows to the Mississippi River via Big Sandy Lake.

The Kennecott/Talon potential sulfide mine would place many critical resources at risk, including Wildlife Management Areas and state parks, state and federally-designated Wild and Scenic Rivers, a federal national wildlife refuge, and high quality wild rice waters. A Tamarack sulfide mine could affect tribal resources retained under the Treaty of 1837 and the Treaty of 1854 and communities of the Mille Lacs Band of Ojibwe and the Sandy Lake Band of Ojibwe.

The high concentration of ore at the Tamarack site is also correlated with high sulfur concentrations. Adverse impacts of sulfide mine discharge on mercury contamination of fish could affect downstream land owners and communities on the Kettle, St. Croix, Tamarack, and Mississippi Rivers.

The Kennecott/Talon mine would be economically attractive because of its rich ore body. Talon’s 2020 Preliminary Economic Assessment (NI 43-101) projects a pre-tax profit of 41%. Community members must become informed about this potential sulfide mine.

READ Local View: Proposed Tamarack mine poses familiar environmental risks

“Talon is proposing to mine a ‘massive sulphide mineralization’ at the headwaters of the Big Sandy Lake watershed, an hour southwest of Duluth. This watershed enjoys clean water and fresh air, abundant wild rice protected by treaty-reserved rights, treasured lake retreats, forests, and wildlife. It is a hunter’s and angler’s paradise.”

Download and share WaterLegacy’s printable Fact Sheet on the Tamarack Sulfide Mine Threat.

Learn about communities that are organizing as the Tamarack Water Alliance to protect lakes and wild rice from potential Tamarack mine pollution.

St. Croix River kayakers. National Park Service photo.

Non-Ferrous (Not Iron or Taconite) Mineral Leasing

The State of Minnesota owns mineral leases on 13.5 million acres, representing approximately 24 percent of the entire acreage of Minnesota. Some state-owned mineral rights are beneath public lands, and some are beneath private property. Non-ferrous minerals include copper, nickel, gold, and platinum group metals. In 2016, the Minnesota Department of Natural Resources (DNR) mapped exploration for non-ferrous minerals across many areas of the Duluth Complex in northeastern Minnesota. In 2020, the area under active exploration had focused on several distinct potential mining areas. Non-ferrous mineral exploration acreage may fluctuate, but applicable laws place both natural resources and private property at risk.

Drilling for copper, nickel, and other metals can contaminate groundwater, pollute surface waters, damage wetlands, and disrupt resort businesses and communities with excessive noise. In addition, mineral leasing could open sensitive areas of the Cloquet and St. Louis Rivers and the Lake Superior, Boundary Waters, and Mississippi River watersheds to potential sulfide mining. Once leases have been granted, vested interests of the mining company holding the lease prevent regulators from screening out sensitive locations or asserting that land surfaces cannot be impacted.

Under Minnesota law, no environmental review of leasing decisions is required. Although the Executive Council (the Governor, Lieutenant Governor, Attorney General, Secretary of State, and State Auditor) “approves” leases after they are bid at auction, in fact at that point the Council has little discretion to disapprove them and has never done so. In addition, under Minnesota law, if the state grants leases beneath private property, mining companies have the power to condemn private surface land.

Advocacy to Protect Lands and Natural Resources

Since 2012, WaterLegacy has worked in collaboration with community groups and private landowners to protect natural resources and private property from non-ferrous mineral leasing and prospecting.

From 2011 through 2012, WaterLegacy participated in a U.S. Forest Service environmental impact statement process related to non-ferrous mining leases in the Boundary Waters watershed. Initially, the Forest Service planned to bootstrap future leasing, without additional environmental review and to allow exploration with few protections of wetlands.

The result? The Forest Service adopted many of WaterLegacy’s recommendations, requiring future leases to have an independent environmental review and setting several conditions to protect wetlands, water quality, and wild rice.

In 2012, WaterLegacy supported a citizen petition for environmental review of non-ferrous mineral leases. The citizen petition was denied and the citizens filed an appeal to the Minnesota Court of Appeals.

The result? The Court of Appeals found that leasing was not a “project,” so did not require environmental review. However, after the decision, DNR increased the quality of information available to the public regarding location of proposed leases and created a portal allowing members of the public to sign up and obtain notices of proposed leasing.

In 2015, when the DNR put 103,000 acres of land across northeastern Minnesota on the auction block for non-ferrous mineral leasing, WaterLegacy engaged 875 citizen comments and testified to request that the Executive Council protect Minnesota from a large sulfide mining district.

The result? These actions did not prevent Council approval of leasing. But, in recent years, DNR mineral leasing has shifted away from leases beneath private lands.

In 2020, the DNR proposed that mineral leasing for gold take place on territories ceded to the U.S. government by the Ojibwe in 1855. The Ojibwe retain the right to hunt, fish, and gather on these lands, and the proposed mineral leasing would have harmed wild rice. WaterLegacy testified at the Executive Council, focusing on the lack of tribal consultation, the effect on wild rice, and the need to require lease conditions for exploration.

The result? The Council approved the leases. But Lieutenant Governor Flanagan took DNR managers out in the hallway and then stated on the record – naming the Bois Forte and Leech Lake Bands of Chippewa –that this Administration would require consultation with tribes on conditions for mineral leases.

Mineral Leasing Advocacy Timeline


The U.S. Forest Service decided to prepare an environmental impact statement (EIS) in response to requests by mining companies for 29 permits to conduct exploratory drilling for minerals on Superior National Forest lands, particularly in the area near Birch Lake, adjacent to the Boundary Waters Canoe Area Wilderness. WaterLegacy argued that the prospecting EIS should not apply to any future prospecting plans and that analysis of impacts and that protections for water quality, wetlands, and wild rice were inadequate.

June 1, 2012

The Forest Service released its final EIS and its Record of Decision setting the conditions under which it would allow prospecting for non-ferrous minerals. This Record of Decision adopted many of the conditions requested by WaterLegacy, including:

Limiting the prospecting EIS to only the permit applications specifically identified for the project (ROD-4)

Requiring that any future permits and operations plans must require a separate and complete National Environmental Protection Act (NEPA) compliance process. (ROD-6). This includes mineral bulk sampling. (ROD-18)

Ensuring that the prospecting EIS does not authorize any mining or minerals development, including, and that such a proposal would require a new and separate NEPA process. (ROD-16).

Preventing impacts on water quantity resulting from cumulative withdrawals of water from the same water body by multiple companies and explorations. (ROD-16).

Increasing protection of natural stands of wild rice in lakes, rivers, and streams. (ROD-16).

June 16, 2012

WaterLegacy also filed an administrative appeal to the Forest Service asking for more protections against noise near the BWCAW, seasonal restrictions on drilling, and better sealing of any boreholes containing brackish water (water with elevated chlorides and specific conductivity). This appeal was denied.

Sept. 25, 2012

Northeastern Minnesota citizens petitioned the Minnesota Environmental Quality Board (EQB) for environmental review of non-ferrous mineral leases. The EQB determined that DNR was responsible to make the decision on the need for an environmental assessment worksheet, the first stage of environmental review.

Nov. 8, 2012

DNR denied the citizens’ petition for environmental review of non-ferrous mining leases. Paula Maccabee, WaterLegacy’s advocacy director and counsel, assisted the citizens pro bono in appealing DNR’s decision.

Sept. 9, 2014

After briefing and oral argument, the Minnesota Court of Appeals issued an opinion denying the right to environmental review of mineral leases. The court held that a mineral lease is not a “project” within the meaning of environmental statutes and rules. The court emphasized that many areas leased would not be mined nor even explored, and stated that exploration plans might require environmental review.

Sept. 9, 2015

The Executive Council met to receive an update on DNR’s August 2015 proposal to auction 103,000 acres of land across northeastern Minnesota for non-ferrous mineral leasing. WaterLegacy facilitated public testimony and requested that the Council delay leases to protect resources, landowners, and taxpayers.


DNR proposed Vermillion Gold leases in 1855 Ojibwe ceded territory affecting wild rice waters and other special features on three-fourths of the proposed acreage. WaterLegacy submitted materials to the Executive Council and testified on February 26, 2020, focusing on the issues of impacts to wild rice, the need to set leasing conditions, and the lack of tribal consultation. The Lieutenant Governor stated on the record that tribal consultation on mineral leasing conditions would be required by the Administration.