Hearing will focus on whether bentonite clay is effective in tailings dam

Here's what to know about the contested case hearing on part of the proposed copper-nickel mine's permit to mine.

An artificial hill, or dam, going up like steps to the left with a water-filled area below it.
Plans for PolyMet include building dams to increase the storage capacity of tailings basins. One would be built in the distance to raise the basin on the right to the level of the area on the left.
Steve Kuchera / 2017 file / Duluth News Tribune

ST. PAUL — Nearly two years after it was ordered by the state’s high court, a long-awaited hearing will begin Monday on a key permit for the project vying to become Minnesota’s first copper-nickel mine.

The contested case hearing, expected to last through the week, will focus on one aspect of the NorthMet project’s permit to mine: whether bentonite, a clay, will effectively line and cap the project’s tailings basin and limit water seepage and oxidation.

For more than two decades, the NorthMet project near Babbitt and Hoyt Lakes has been pursued by PolyMet Mining, which, as of last month, is now NewRange Copper Nickel , a joint venture between PolyMet and Teck American.

The permit to mine is one of several permits that have been challenged since they were first issued in 2018.

Here’s what you need to know about this week’s contested case hearing:


Why is there a hearing?

In short, there wasn’t enough evidence to prove the effectiveness of bentonite, according to the Minnesota Supreme Court.

In an April 28, 2021 decision , Justice Natalie Hudson wrote that while the DNR claimed bentonite "has been tested" and "will be effective," its descriptions and "conclusory statements" did not actually include scientific analysis.

"There is no analysis of the scientific basis for the DNR’s assumptions," Hudson wrote. "Further, the single study on which nearly all the DNR’s findings of effectiveness rely is not in the record."

How would bentonite be used?

The permit to mine calls for the company to line and cap the project’s tailings basin — a dam that would store waste rock left behind after processing out copper, nickel, cobalt and other metals — with bentonite, which swells when wet, to prevent oxygen from contacting the tailings and creating acid, the type of pollution environmentalists fear most with copper-nickel mining. Bentonite would also be mixed in with the tailings.

What is a contested case hearing?

A contested case hearing puts issues, like state agency decisions, in front of an administrative law judge to examine additional evidence and testimony.

The administrative law judge will then write a non-binding recommendation on the matter.

Then, the DNR can decide whether or not it should modify the permit based on the judge’s recommendation before it reissues it.

The DNR’s decision can then be challenged at the Minnesota Court of Appeals, meaning it could again work its way up to the Minnesota Supreme Court.


The Minnesota Pollution Control Agency has until Nov. 14 to make a decision on the water permit.

A recent example of such a hearing is the 2020 contested case hearing held to sort through questions related to permits for Enbridge’s Line 3 oil pipeline.

In fact, the same administrative law judge that oversaw the Line 3 hearing, James LaFave, is overseeing this week’s contested case hearing on the NorthMet project.

Why just bentonite?

While the Supreme Court only required the DNR hold a contested case hearing on the effectiveness of bentonite, the state agency could have expanded the scope of the hearings.

Environmental groups pushed for hearings on other issues, like dam safety, but both the company and the agency opposed it and the hearing remains narrowly focused on bentonite.

Separate and outside of the contested case hearing, the DNR is going to determine a fixed end date for the permit to mine and is considering whether to include Swiss-mining company Glencore (PolyMet’s majority owner and a funder of the NewRange joint venture) on the permit.

What to expect at the hearing

The hearing will give the parties an opportunity to cross-examine witnesses in front of the administrative law judge.

Parties will be trying to prove that bentonite is or isn’t a “practical and workable” reclamation technique under Minnesota law “that will reduce infiltration of oxygen and water into the stored tailings and satisfy the reactive mine waste rule, ” according to briefs filed by both the conservation organizations and the mining company.

Additionally, the DNR identified five specific fact disputes that should be considered:


  1. How bentonite would be applied to the tailings basin sides, beaches, and pond bottom to ensure its effectiveness in reducing infiltration of oxygen and water into the stored tailings over time?
  2. How should the application methods of the bentonite be evaluated or tested before application to ensure effectiveness in reducing infiltration of oxygen and water into the stored tailings?
  3. Would the pond-bottom, bentonite-amended cover be effective in maintaining a permanent pond that acts as a water cover over the stored tailings?
  4. Would any conditions in the pond result in a cation exchange that could reduce the effectiveness of the bentonite in reducing infiltration of oxygen and water into the stored tailings?
  5. How would PolyMet (NewRange) ensure bentonite’s effectiveness in reducing infiltration of oxygen and water into the stored tailings over time? 

NewRange and the DNR are expected to maintain bentonite would be effective while parties arguing against the bentonite include the Fond du Lac Band of Lake Superior Chippewa and environmental groups, including the Minnesota Center for Environmental Advocacy, WaterLegacy, Friends of the Boundary Waters and other organizations.

How to watch the hearing

There is no remote viewing option. Those wishing to view the hearings must do so in person in St. Paul.

The hearing will begin at 9:45 a.m. Monday, March 27, at the Office of Administrative Hearings , Stassen Building, 600 N. Robert St. in St Paul.

The hearing could last through Friday, March 31.

Jimmy Lovrien covers energy, mining and the 8th Congressional District for the Duluth News Tribune. He can be reached at or 218-723-5332.
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