Minntac Tailings Basin

What is 8,700 acres in size, located in the headwaters of Boundary Waters Canoe Area watershed rivers, and has effectively resisted permit controls on sulfate and other water pollution for a quarter of a century? The U.S. Steel Minntac tailings basin is the poster child for Minnesota’s failure to control mining pollution, even when there is clear evidence that the pollution has violated Minnesota water quality standards and decimated downstream wild rice.
Minntac tailings basin

November 30, 2018, despite the opposition by WaterLegacy and our allies, MPCA issued a final permit that did not set water quality-based limits on Minntac tailings basin direct pollution of wetlands and streams and did not control Minntac discharge of pollution through groundwater. Water quality, fish, and wild rice were not protected.

The Minntac tailings basin water pollution permit expired in 1992, and it took the Minnesota Pollution Control Agency (MPCA) more than a quarter of a century to reissue a new permit in 2018. Under pressure from lawsuits, MPCA finally proposed draft water pollution permits for the Minntac tailings basin in 2014 and 2016. MPCA’s draft permits were inadequate to protect water quality or wild rice, so WaterLegacy and our allies submitted detailed and highly critical comments. The U.S. Environmental Protection Agency (EPA) also submitted a comment stating that MPCA’s proposed draft Minntac permit would violate the Clean Water Act.

WaterLegacy and the Fond du Lac Band of Lake Superior filed appeals from the MPCA’s issuance of the Minntac water pollution permit on the last day of 2018. WaterLegacy’s appeal challenged: 1) MPCA’s failure to set pollution limits on direct discharge from the Minntac tailings basin; and 2) MPCA’s failure to control discharge from tailings basin seepage through groundwater affecting downstream waters and wild rice.

Minntac tailings basin. Photo from GLIFWC.

What’s the current status of the Minntac permit appeal?

After briefing and oral argument, on December 9, 2019, the Minnesota Court of Appeals issued a decision that cut both ways. The Court ruled that the MPCA failed to require water quality-based effluent limits on direct Minntac discharge in violation of the Clean Water Act. The Court sent this portion of the permit back to MPCA due to evidence that pollution capture used by Minntac was not effective.

However, the Court affirmed MPCA’s conclusion that any pollution that traveled through groundwater before polluting wetlands, rivers, and lakes was not covered by the Clean Water Act. The MPCA could avoid control of pollution seeping from the Minntac tailings basin through groundwater.

Minnesota Supreme Court Review

WaterLegacy and the Fond du Lac Band petitioned the Minnesota Supreme Court to review the Court of Appeals’ decision that pollution through groundwater need not be controlled under the Clean Water Act. On February 26, 2020, the Minnesota Supreme Court – which accepts only about 5 percent of petitions – agreed to take the case.

Helpful U.S. Supreme Court Decision

While the Minntac appeal to the Minnesota Supreme Court was pending, the U.S. Supreme Court decided a related Clean Water Act case coming out of Maui, Hawaii. In County of Maui v. Hawai’i Wildlife Fund, the Supreme Court ruled that a position like that taken by MPCA for the Minntac permit – that no pollution through groundwater could ever be controlled by the Clean Water Act – created an unacceptable loophole. The Maui case held that discharge through groundwater was the “functional equivalent” of direct discharge, and it must be regulated.

Minntac Tailings Basin Permit History


Minntac 1987 National Pollutant Discharge Elimination System/State Disposal System (NPDES/SDS) water pollution permit expires in 1992. It is “administratively extended” by MPCA for 26 years before an updated permit is reissued. The permit contains no limit on sulfate to protect wild rice.


MPCA releases a pre-publication draft Minntac water pollution permit. This permit does not require compliance with Minnesota’s 10 mg/L sulfate standard.


MPCA circulates another draft Minntac water pollution permit. The permit does not require compliance with Minnesota’s 10 mg/L sulfate standard. WaterLegacy’s Advocacy Director states in the Timberjay that MPCA’s draft Minntac permit “stands the Clean Water Act on its head and lets the polluter set the standard.”


U.S. Steel requests a variance from even the few permit conditions proposed by MPCA for the Minntac tailings basin. This variance is denied by MPCA.


MPCA grants a final permit to U.S. Steel for the Minntac tailings basin on November 30, 2018. The final Minntac permit contains no limits on sulfate to protect wild rice and, in fact, contains no water quality-based effluent limits at all. The permit requires no controls on tailings basin seepage through groundwater to surface water to meet water quality standards in affected wetlands, streams and lakes. Ever.

Minntac Mine Expansion without Environmental Review

Many Minnesotans believe that mine expansions go through a rigorous environmental review process. Nothing could be further from the truth.

Aerial photo of huge expansion of Minntac mine, tailings basin and processing facility (documents filed by U.S. Steel in 2012)

The Minntac mine has been continually and incrementally expanded for decades without ever going through an environmental impact statement (EIS) study of harm to the environment or alternatives to minimize that harm. The most recent Minntac expansion was in 2012. The expansion proposed impacts to 483 acres, including 67 acres of wetlands and excavation of nearly 2 billion tons of ore, waste rock, and overburden (natural rock and soil above the ore body). WaterLegacy and our allies called for an EIS and an investigation of water quality issues and alternatives.

The result? No EIS was ordered by either the Minnesota Department of Natural Resources (DNR) or the U.S. Army Corps of Engineers.

MPCA approved the certification of the Minntac permit under the Clean Water Act, despite the fact U.S. Steel was in violation of even its decades-old weak permit. WaterLegacy commented:
Neither federal nor state law allows the MPCA to certify the proposed Minntac Mine Expansion. This project is a textbook case of what Section 401 was intended to prevent – the increase of discharge that already violates water quality standards by a polluter operating outside the law for a matter of decades.