Despite igniting some of the most heated politics Minnesota ever has experienced over an environmental rule, wild rice won a victory of sorts on Tuesday. But it will be a long time in coming.

The Minnesota Pollution Control Agency revealed its proposed plan for protecting the state’s official grain from pollution that comes off the Iron Range and from about 200 industrial plants statewide.

In an unusual approach, it calls for detailed scientific testing of the muck in each of the known 1,300 lakes, streams and wetlands that grow or have grown wild rice since the mid-1970s. The proposal itself will have to go through years of review. In the meantime it’s not clear whether the PCA will deploy existing environmental protections.

The long debate, which has resulted in litigation and millions in state spending on research, carries an exceptional emotional charge because it entangles two of Minnesota’s cultural touchstones — mining and wild rice.

The long-awaited announcement, which had been scheduled for Thursday, was abruptly made Tuesday instead. It came after Gov. Mark Dayton roiled the political waters by saying in an interview with Minnesota Public Radio that the existing rules were outdated. Enforcing them, he said, “could be catastrophic for northeastern Minnesota.”

It was only the latest scramble in the continuing saga of a high-profile environmental debate that has dogged the Dayton administration for several years.

Since 1973, Minnesota has had a rule on the books specifically to protect wild rice against sulfate, a mineral salt produced by runoff from taconite mines as well as from industrial plants that treat water, produce ethanol and other agricultural products. It’s the only one like it in the country.

For most of the rule’s history, it was not enforced or updated. But starting in the early 2000s, Indian tribes, the Environmental Protection Agency and environmental groups began pressuring the state to apply it in new permits for the taconite industry, launching a contentious fight over whether the limit of 10 parts per million was scientifically valid.

The state embarked on two years of research and an extensive peer review process by outside scientists to test it, and Tuesday announced their conclusions.

Turns out it’s complicated.

Instead of suggesting a simple rule that would limit discharges to a certain level, the state is proposing to establish a unique level for every body of water where wild rice grows. In short, officials said at a news conference, the existing standard of 10 parts per million isn’t wrong. It’s just imprecise.

They will calculate a safe level of sulfate for each body of water where mines and industrial discharges could affect the plant, by using a formula that includes the amount of naturally occurring iron and organic carbon that is also present in the muck. The complex chemical interplay of all three play a role in whether wild rice grows.

“This proposed approach is uniquely protective of wild rice in any location,” said Katrina Kessler, manager of water assessment for the PCA.

The state has tried it on three unpolluted wild rice lakes, and they found that the acceptable level for sulfate varies widely.

State officials said that their plan, which they agree is unusual, is the starting point of a long conversation with the public, the federal government, industry, environmental groups and the tribes.

As soon as the news was released Tuesday, the debate began.

“I am furious,” said John Pastor, a wild rice researcher at the University of Minnesota Duluth, who has conducted studies for the state and Indian tribes. “This is scientifically indefensible.”

Pastor said that conditions in wild rice waters can change from season to season and year to year. A flood can wash organic carbon out of lakes, for example.

“The system is too dynamic,” he said.

Dan Engstrom, a scientist at the St. Croix Watershed Research Station who has also participated in the state’s research project, said that in theory, the plan could work because it fits the scientific results. But he, too, said variability in the wild rice beds could be a problem.

Paula Maccabee, an attorney for Water Legacy who has fought for wild rice protections in court, questioned using a formula instead of a simple limit on a pollutant. The amount of data and sampling the plan requires would open the process to inaccuracy and “mischief,” she said.

There’s also far more at stake than wild rice, said Kathryn Hoffman, an attorney with the nonprofit Minnesota Center for Environmental Advocacy. Sulfate also has been linked to mercury in fish, which affects human health as well.

“We don’t want our waters to be the subject of an experiment,” she said.

U.S. Steel, the largest taconite operator in the state, which has been lobbying the Legislature to suspend enforcement of the current rule, said, “We look forward to reviewing the full proposal and determining how it will impact our operations. We are confident that the MPCA can effectively protect wild rice and maintain a competitive iron mining industry in northern Minnesota.”

The final arbiter, however, will be the EPA. It has delegated authority to the state to enforce the federal Clean Water Act, and it has the right to review and approve all permits issued in the state, as well as any proposed changes to water quality rules.

Rebecca Flood, assistant PCA commissioner, said the federal agency has been informed “at the highest levels” of the state’s new approach.