In a rare public dispute, federal land managers say Minnesota state officials are being too lenient with polluters causing atmospheric haze over northern parks and wilderness lands.

The U.S. Forest Service and the National Park Service have objected to how Minnesota plans to deal with a long-unenforced part of the federal Clean Air Act that aims for pristine air in places like Voyageurs National Park and the Boundary Waters Canoe Area Wilderness (BWCA).

"We work with the state agencies on a daily basis," said Tim Dabney, acting supervisor of the Superior National Forest, which includes the BWCA, a federal wilderness area. "In almost all cases we are in lockstep with them."

But not on haze. As the issue comes before the Minnesota Pollution Control Agency (MPCA) citizens board on Tuesday, federal land managers say the state isn't pushing electric utilities and taconite companies to install the best-available pollution controls as the law requires.

"The methodology used by the MPCA results in emissions limits that are too high, and we ask that you reconsider them," Susan Johnson, acting chief of the National Park Service's policy, planning and permit review branch, said in a letter to the agency.

Emissions from 11 coal-burning power plants and taconite facilities have been linked to reduced visibility over northern Minnesota's natural areas, as well as Isle Royal National Park in Lake Superior. Out-of-state pollution also plays a role.

It's not that the air in the natural areas is highly polluted. The haze, formed partly by nitrogen oxides, can be hard to spot except at sunset or by comparing high-haze and low-haze photos. But it can be measured.

The federal Clean Air Act, under amendments dating to 1977, requires air over parks and wilderness areas to be restored to pristine conditions using the best technology on smokestacks. For 35 years, that hasn't happened. In the face of a court deadline, Minnesota and other states now must approve plans to comply with the federal law.

Good enough?

Minnesota's plan calls for the iron mining industry to use "good combustion practices" at six mills where iron ore is processed into taconite pellets. At five coal-fired generating stations, Minnesota officials contend that no plant-specific additional restrictions are needed. Instead, state officials believe that pending regulations to reduce air pollution across the eastern United States will also help cut haze.

That means coal power plants won't necessarily have to add the best, most-expensive pollution control equipment. The cross-state regulations also give utilities the option of purchasing pollution allowances under a market-based system, though state officials don't believe that will happen.

"We don't think this substitution will adversely impact the goal we have set for [natural] areas," PCA planner Catherine Neuschler said.

Yet the fate of the substitute, cross-state regulations is uncertain because of a court challenge.

Only one affected coal-fired generating unit, at Minnesota Power's Boswell station, has installed technology called selective catalytic reduction (SCR). It is widely considered the best technology for coal power plants to reduce nitrogen oxides that react in the air to cause haze.

Xcel Energy, whose two oldest coal burners at the Sherco power plant are sources of haze, says it will spend $50 million to retrofit them -- a upgrade that would satisfy Minnesota regulators -- but wouldn't add the advanced SCR technology. However, the U.S. Environmental Protection Agency has separate authority to order Xcel to make that upgrade.

Janette Brimmer, an environmental attorney who represents the National Parks Conservation Association and other environmental groups, said the state's enforcement plan won't improve visibility in the natural areas. She said it's too easy for people to dismiss haze regulation as unimportant.

"People always want to say, 'Oh, it's just visibility,'" Brimmer said. "Well it's not just visibility. That's a proxy for the bigger problem. These pollutants that contribute to haze are really damaging to human health. ... If we are not protecting our air in the most pristine places, then we are really screwing up across the board."

Brimmer said the taconite industry's contribution to haze has gotten far less attention than coal power plants'. Some taconite plants don't continuously monitor key emissions, Brimmer said, raising doubts about data on which the state based its proposed limits.

There are signs that the taconite industry is divided over the issue. The state's Iron Mining Association, which lobbies and speaks for the industry, declined to comment about haze regulations. And Dabney, the Superior National Forest chief, said taconite producers should follow the lead of U.S. Steel Corp., which has updated its taconite plants' pollution monitoring equipment and seems willing to take other steps to reduce emissions.

Meanwhile, Cliffs Natural Resources, which operates three taconite mines and a power plant in northeast Minnesota, submitted lengthy technical concerns about the state's enforcement plan, asserting that new monitoring systems are "burdensome" and the emissions limits too strict.

David Shaffer • 612-673-7090