The U.S. Environmental Protection Agency (EPA) is pressuring the state to take a tougher stance on a massive taconite waste pit that for decades has been leaking pollutants into the nearly pristine watershed that holds Lake Vermilion and the Boundary Waters Canoe Area Wilderness.

In a sharply worded letter last month, the EPA suggested that the state's proposed plan for the Minntac tailings basin is not in line with the Clean Water Act and other federal laws because it has no clear deadlines to fix the problems.

State pollution officials say that the plan is still a work in progress. But their decision on how the 13-square-mile basin will be managed is under intense scrutiny by industry, Indian tribes and environmental groups because it is emerging in the midst of heated conflicts over the links between taconite mining, the destruction of wild rice and toxic mercury pollution in game fish. And the state's stance on all mining issues is under the spotlight now because of its pending review of PolyMet Mining Corp.'s proposed copper-nickel mine — a much riskier type of mining that has polarized the state along a jobs vs. environment fault line.

Minntac, owned by Pittsburgh-based U.S. Steel Corp., is the largest taconite operation in the country, employing 1,400 people. It covers nearly 60 square miles near Mountain Iron, including a 10-mile-long open pit mine and several processing facilities. Last year it won state approval to expand its open pit by another 480 acres, extending the life of the mine by 16 years.

Its tailings basin, which holds waste rock and polluted water from decades of mining, is the first and most critical of nearly two dozen mine sites in Minnesota that need new environmental permits from the state. The one for the Minntac tailings basin is the oldest — it expired in 1992.

"We made this one a higher priority because of the level of concern the public has," said Ann Foss, who heads the mine permit division for the Minnesota Pollution Control Agency (MPCA). "There are impacts in the area that need to be dealt with."

It was built in the 1960s on top of the Laurentian Divide that separates the St. Louis River Watershed, where water flows to Lake Superior, and the Rainy Lake Watershed where water flows north to the BWCA and Canada. On three sides it is surrounded by forests and wetlands and butts up against the Dark River on the west side and the Sandy River and the twin Sandy Lakes on the east.

But unlike most of the state's taconite operations that drain into the St. Louis River Watershed, which has long been affected by taconite mining and other industries, this is one of the few sites that drains north into the last remaining areas of the state that is largely untouched.

"It's a large concern," said Dan Engstrom, director of the St. Croix Watershed Research Station, an expert on water quality who has studied northeast Minnesota extensively. "You are dealing with a more pristine system."

Like many tailings basins of that era, it was designed to allow water to filter through the walls and out the bottom. But since its first permit was issued in 1987, environmental science and regulations have advanced considerably. Now the water that seeps through carries contaminants that exceed limits established in a number of pollution laws, including the one that protects wild rice.

Sulfates, wild rice and more

The problem is sulfate, a mineral salt that pours from the Iron Range and its vast mining pits after rock is exposed to air and water. It's also produced by waste water treatment plants and other industrial processes. Wild rice doesn't fare well in waters that are high in sulfate.

Much of the water leaving the pit is polluted with a variety of contaminants, but the sulfate concentrations are among some of the highest measured on the range, said Kathryn Hoffman, an attorney with the Minnesota Center for Environmental Advocacy, a nonprofit law firm. Measurements in the nearby streams and lakes show concentrations that are hundreds of times higher than they should be. The wild rice that once grew in the nearby lakes on the east side is long gone.

"It's a good example of what happens when you leak a lot of sulfate into wild rice waters," said Engstrom.

There may be more at stake than wild rice. Increasingly, research is tying sulfate to mercury. Many of the lakes and rivers in northeastern Minnesota, including those downstream from the Minntac tailings basin, are contaminated with mercury, a neurotoxin that accumulates in the fish that people like to eat.

Fighting over quality rule

Minnesota is the only state in the country with a water quality rule to limit sulfate, adopted years ago to protect wild rice. But since 2010, it's been the subject of court cases, three years of rancorous public debate, $1.5 million in taxpayer-paid research, and a lengthy scientific review that is expected to be completed early this year.

It's all because the state has been under increasing pressure from the EPA, Indian tribes and environmental groups to enforce it. Industry, on the other hand, has resisted, arguing that the underlying science for the rule is unsound, and has pushed for higher sulfate limits.

Now, that fight has come to roost at the Minntac tailings basin.

"They know the real impact of that sulfate seepage," said Paula Maccabee, an attorney for WaterLegacy, an environmental advocacy group. "Minntac is a poster child for failure to regulate pollution."

Over the years, the company has made changes to reduce the concentrations of pollution in the pit and to collect contaminated water. It's in the process of doing more. But the proposed permit would "have a significant impact on Minntac's operations," and would "cause significant hardship for the company," U.S. Steel said in letter to the MPCA.

The MPCA proposed a plan that would require U.S. Steel to do extensive testing to measure the pollutants in the surrounding creeks and wetlands, and to build more systems that would pump escaping water back into the pit. It gave the company two years to come with a plan to meet water quality standards.

In its written response, the company said much of the demands for testing were "arbitrary and capricious," and that its achieving water quality standards should be designated as goals, not enforceable standards. Moreover, it said, the state has no legal justification for designating the nearby lakes as wild rice waters.

Courtnay Boone, spokeswoman for U.S. Steel, said officials would not comment on the proposed permit beyond their written response to the state.

"We are continuing to review it, and are endeavoring to work with stakeholders," she said.

But the EPA and environmental groups are equally critical of the plan. In its one-page response, the EPA said that, as proposed, the permit does not do enough to address the long-standing pollution problems at the site. It urged the state to develop a plan that "includes extensive and specific actions, and definitive time frames for these actions."

Hoffman said that what is most disheartening about the proposed permit is that it clearly shows that neither the company nor the state has figured out a solution.

"That's why there is no end date," she said.

There's another looming conflict — which law applies. The state proposes to regulate the groundwater contamination with state law, which Foss said is far more flexible and still has the same outcome — protection of the water. But the EPA insists that the Clean Water Act applies.

"We understand that is their perspective," she said. "That has been their perspective for a while."

Foss said that the MPCA will now consider all the comments that have been submitted, and go back to work on the permit. She expects it to be publicly released for comment at the end of January, and that the MPCA's Citizen's Advisory Board will consider it later this year.

The permit for the tailings basin will most likely change, she said, but she could not predict how.

"Reasonable people disagree on how to regulate this type of facility," she said.

Josephine Marcotty • 612-673-7394