DULUTH -- Parties have asked the Minnesota Supreme Court to review last month’s Minnesota Court of Appeals decision that reversed a permit allowing the continued operation of U.S. Steel’s Minntac taconite iron ore mine in Mountain Iron and set long-range goals for the company to reduce pollutants leaking out of the plant's tailings basin.

Last month, the Court of Appeals found the MPCA failed in its interpretation of state water-quality rules and that the MPCA's decision on Minntac's tailings discharge was unsupported.

In separate petitions filed Wednesday, the MPCA, environmental group WaterLegacy and the Fond du Lac Band of Lake Superior Chippewa asked the Minnesota Supreme Court to review the Court of Appeals decision because they say it erred by concluding drinking-water standards do not apply to groundwater and, therefore, MPCA can not issue permits with conditions setting groundwater as that class of drinking water.

The MPCA said the court "significantly departed from accepted and usual rules of regulatory interpretation" and now 81 active permits are called into question.

"The decision is important and has statewide impact as it jeopardized groundwater throughout the state and calls into question the validity of 81 existing permits," Assistant Attorney General Stacey Person wrote in the MPCA petition.

The Supreme Court has 60 days to decide if it will take up the case.

The water pollution discharge permit was issued by the MPCA in late 2018, the first for Minntac since 1987. That 1987 permit had been up for reissuance since 1992, but was “administratively extended since then,” MPCA officials said.

The five-year permit issued in 2018 had set long-range goals for U.S. Steel to meet for reducing pollutants, like sulfates, that are leaking out of the site’s 8,000-acre tailings basin — where a wet slurry of mine waste left over after taconite pellets are processed resides — into nearby surface and groundwater.

While environmental group WaterLegacy initially celebrated the decision that reversed the permit, its petition argued the Supreme Court should review the Court of Appeals’ decision because while the court ruled the MPCA had authority to determine the federal Clean Water Act didn't apply to groundwater pollution released into wetlands, rivers and lakes, the court had also ruled the MPCA didn't have the authority to read state drinking-water rules when setting numeric limits on the pollution of groundwater.

“Taken together, the Court of Appeals’ decisions would have devastating and statewide effects on Minnesota’s authority to regulate pollution through groundwater to surface water and pollution to groundwater itself,” WaterLegacy counsel and advocacy director Paula Maccabee wrote in the petition.

The Fond du Lac Band of Lake Superior Chippewa made arguments similar to WaterLegacy in its separate petition and said: “This (Supreme) Court’s review is essential because the Court of Appeals decision is overbroad and will lead to absurd and dangerous results.”

Fond du Lac filed an appeal to the permit last year, noting that Minntac is located within the western border of the 1854 Ceded Territory, where the band retains off-reservation treaty rights to hunt, fish and gather, giving Fond du Lac a say in natural resource issues and that pollution from Minntac, namely sulfate, was affecting wild rice waters.

U.S. Steel didn't file a petition Wednesday. In December, a company spokesperson told the News Tribune that U.S. Steel was “pleased with the Court’s ruling on the Minntac tailings basin” after the permit was reversed.

Last year, U.S. Steel filed an appeal challenging the MPCA’s permit. The company said the MPCA shouldn't have denied a contested case hearing on the permit details and refused to adopt a variance it requested for some pollution limits.

“(MPCA) failed to undertake any substantive evaluation of evidence in the administrative record regarding the financial hardships that would result from requiring strict conformity with the secondary groundwater sulfate guidelines on which the Permit’s sulfate limits are based,” U.S. Steel wrote.

Minntac is the largest taconite iron ore mining and processing operation in the U.S., with production of up to 16 million tons per year and 1,700 employees. It went online in 1967.

This story was updated on Jan. 9 at 10 a.m. with information from the MPCA's petition. The article was originally posted at 7 p.m. on Jan. 8.