Two mining companies in northern Minnesota are pushing back against state water pollution rules that aim to protect wild rice beds, saying the mines aren't hurting the cherished food source.

But a researcher and an Ojibwe tribe say the mines are relying on a debunked method to avoid state water quality standards — and say state regulators should push the companies for better science.

It's the latest maneuver in a decades-long fight over whether a key industry in northeast Minnesota — iron mining — can coexist with the region's treasured wild rice.

The state has known for years that too much sulfate, a mineral salt that seeps out of taconite mines, sewage plants and other industry, could end up damaging rice. Sulfate occurs naturally in water in some parts of Minnesota, but monitoring has shown a clear swath of artificially high levels along the state's Iron Range.

Fifty years ago, the Minnesota Pollution Control Agency set a rule that limited how much sulfate could be released into waterways where wild rice grows, but the agency never enforced it. In recent decades, the Legislature repeatedly directed the agency to either change or drop the rule.

Nancy Schuldt, water projects coordinator for the Fond du Lac Band of Lake Superior Chippewa, said tribes had been pushing the state to apply the sulfate limits at least back to the early 2000s. Wild rice, called manoomin in the Ojibwe language, is sacred and part of the tribes' migration story.

"We have been urging [MPCA] just to do their job for a long time," Schuldt said.

Last year, the Environmental Protection Agency ordered the state to enforce the standards. As the state begins to set those limits for facilities, some mines are already pushing back.

'Smoke and mirrors'

Minnesota's sulfate rule has its origins in observations made by biologist John Moyle in the 1940s. He noted that rice didn't thrive in water where sulfate rose above 10 parts per million.

In the mucky soil of lakes and streams, sulfate is converted into sulfides, which are toxic to rice plants, said John Pastor, a retired professor from the University of Minnesota Duluth who conducted experiments with rice. If there's iron in the sediment, it can bind with the sulfides, and in some cases, the resulting compounds will smother and choke the roots of rice plants, Pastor said.

The rule set in 1973 adopted that limit of 10 ppm, but the state did not require polluters to heed it. At the behest of lawmakers, the MPCA in 2017 proposed a new method that would tailor the sulfate limit to each lake, river and stream where the plant grows.

Pastor said that the MPCA's method didn't protect wild rice because it ignored the potential for iron-sulfides to smother rice roots. An administrative law judge eventually threw out the new rule. But two companies, U.S. Steel and Cleveland-Cliffs, have brought up the discarded regulation again to argue that in two rice beds downstream of their mines, the rice is healthy and the limits on sulfate should be loosened.

The mines are "playing this smoke and mirrors game," Pastor said. "It's something that looks scientific, it's something they can go back and reference and say, 'Look, PCA developed this.'"

Cleveland-Cliffs did not respond to requests for comment.

A representative of U.S. Steel wrote in an email that it used the MPCA's old equation because "Although the rule was withdrawn, the protocol was developed and supported by MPCA."

The two companies could eventually become one — Cleveland-Cliffs made a $7.3 billion offer to buy U.S. Steel, though the company rejected the offer. Cleveland-Cliffs is still pursuing the purchase.

Setting the rules

U.S. Steel and Cleveland-Cliffs are each asking for a "site specific standard," an exception allowed by law, which would change sulfate limits in small lakes downstream of their mines.

In a rice bed south of U.S. Steel's Keetac facility in Keewatin, the company wants a limit almost eight times higher than the statewide rule. Cleveland-Cliffs wants a limit more than 40 times the standard for waters downstream of its United Taconite mine near Eveleth.

If the requests were granted as-is, the companies could potentially avoid installing costly pollution control methods to restrict the sulfate that seeps from the mines and their tailings sites.

Schuldt said that the state needs to make it clear that these mines, or any other, can't use the MPCA's debunked method of setting sulfate limits.

"Kick it to the curb," she said. "There is no scientific evidence that is protective of wild rice."

It's unclear how the situation will play out, because the MPCA hasn't finalized how it will handle requests like those from U.S. Steel and Cleveland-Cliffs. The agency is accepting public comments on the issue through Sept. 4.

"We continue to work closely with permittees, tribal nations, and other Minnesotans to research the best ways to protect wild rice and to ensure that any standard outside of the 10 [parts per million] will be fully protective of wild rice," spokeswoman Andrea Cournoyer wrote in an email.

The agency has said that at a minimum, it will require long-term data on the health of a rice bed and the amount of sulfate before it considers a deviation from the statewide rule. If an applicant doesn't have this data already, it could take as long at 10 years to collect it.

And in a webinar for industry held in June, an MPCA research scientist said that a company would have to comply with the existing standard as it waited for a new one to be approved or denied.

The EPA will also have to approve any site-specific standards, even if the state agrees to them.

Complying with the rule will likely be expensive, both for mines and other sulfate producers like municipal sewage plants. Cournoyer wrote that an MPCA grant program could help taconite mines cover the cost.

Cliffs and U.S. Steel did not respond to questions on how much it would cost to filter out sulfate at the two sites where they've asked for looser standards.

But at U.S. Steel's Minntac taconite mine, the company laid out the estimated annual cost of filtering sulfate in a plan it filed with the state last year: between $9 million and $27 million.