SILVER BAY — An environmental group is suing to stop construction on the expansion of a tailings basin holding back mine waste near Lake Superior.

In a June 16 lawsuit against the Minnesota Department of Natural Resources and Northshore Mining Co., WaterLegacy alleged that Northshore, which is owned by Cleveland-Cliffs, violated the Minnesota Environmental Policy Act by allowing construction before the project’s environmental impact statement process was complete.

In March 2024, the DNR said an environmental assessment worksheet, or EAW, was sufficient for the 650-acre area expansion and 60- to 75-foot dam elevation increase of Northshore’s Milepost 7 tailings basin, near Beaver Bay and 3 miles from Lake Superior. The DNR said a more stringent environmental impact statement, or EIS, wasn’t needed.

Gary Meader / Duluth Media Group

However, in February,
the Minnesota Court of Appeals ruled that the state agency erred
in its decision and said the DNR needed to reconsider that determination.

Paula Maccabee, executive director and counsel for WaterLegacy, wrote in the complaint that the basin’s dams, completed 45 years ago, do not “meet the minimum dam safety standards used in current and prudent engineering and environmental practice to prevent dam failure.”

“Defendants’ conduct may have already undermined effective EIS review and created an emergency dam instability situation,” Maccabee wrote in WaterLegacy’s memorandum in support of its motion for a temporary restraining order seeking to bar the DNR from awarding the project more approvals and prevent Northshore from more construction.

WaterLegacy pointed to a Feb. 3 statement by the DNR — issued after the Court of Appeals decision — that said the company could continue constructing the dams as long as it complied with existing permits.

WaterLegacy also included a June 10 drone photo that shows considerable construction and extensions had already been made on the basin’s north dam wall compared to a satellite image taken five years earlier.

Clint Austin / 2020 file / Duluth Media Group

Additionally, WaterLegacy said in its complaint that an inspection report by the company indicates that the height of some dam walls was raised as early as 2023.

The DNR declined to comment Monday specifically on the lawsuit, adding that it “will file a written legal response to the most recent lawsuit from WaterLegacy in the coming weeks.”

The agency said it approved “conditions for constructing and operating the proposed project” when it issued Northshore its master permit and five-year operating permit in June 2024, after it deemed an EAW was sufficient in March 2024 but before the Court of Appeals decision in February 2025.

However, the state agency said those approvals are no longer in effect now that the Minnesota Supreme Court in May denied the DNR’s petition for review challenging the appellate court’s Feb. 3 decision, letting the lower court’s decision stand.

“The EAW for the proposed project is now back with the DNR for further consideration,” the agency said Monday. “Because the EAW was remanded back to the agency, the portions of the DNR approvals related to the proposed project are no longer in effect.”

Cliffs did not respond to the News Tribune’s request for comment.

The company is planning to increase the basin’s footprint and height to the maximum allowed in its nearly 50-year-old permit: an area of 2,800 acres and dam wall heights of up to 1,315 feet above sea level, 650 acres more than its current area and about 60-75 feet above the current dam elevation.

The famed basin was completed in 1980 after then-owner Reserve Mining was forced to stop its decadeslong practice of dumping tailings — the fine pieces of waste rock left behind after taconite is crushed and stripped of its iron — directly into Lake Superior and years of court battles over the tailings’ pollution and asbestos-like fibers found in the drinking water of Duluth.

Northshore mines iron ore from its Peter Mitchell Mine near Babbitt, processes the material into pellets at its Silver Bay facility and sends the tailings to Milepost 7.