MINNEAPOLIS (AP) — Clean air advocates, the U.S. Environmental Protection Agency and a subsidiary of Xcel Energy have reached a settlement designed to reduce emissions from the coal-fired Sherco plant in Sherburne County, according to documents filed Friday in U.S. District Court.

The environmental groups say the agreement requires Northern States Power Co. to reduce sulfur dioxide emissions from two Sherco units by about 10,000 tons annually by Oct. 1. Further reductions are required by 2017.

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The six groups sued the EPA and Northern States Power in 2012, saying pollution from the Sherco plant near Becker is unhealthy and a major contributor to haze that obscures the views at Voyageurs and Isle Royale national parks and the Boundary Waters Canoe Area.

The National Park Service certified in 2009 that pollution from the plant significantly impaired visibility in the parks. The EPA was required to verify the impairment and order that the best pollution controls be installed at the plant. The lawsuit was filed after the EPA failed to act.

There will be an opportunity for public comment before the settlement takes effect.

Frank Prager, Xcel Energy’s vice president of policy and federal affairs, released a statement Friday saying the company was pleased to reach the agreement.

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“We have invested – and continue to invest – in clean air strategies that protect the environment, improve the electricity system and provide value to our customers,” he said.

The EPA referred questions to the Department of Justice. A message left there was not immediately returned.

The environmental groups released a statement saying the settlement was an important step, but more reductions are necessary to prevent ongoing degradation to the pristine parks.

Stephanie Kodish, director and counsel of National Parks Conservation Association’s Clean Air Program, said the agreement requires Sherco to make meaningful smog reductions that will improve air quality and public health, but “NSP can and must do more to clean up Sherco emissions and transition the plant to cleaner energy to help restore clean, clear skies to the region.”

The plaintiffs in the lawsuit include the National Parks Conservation Association, Minnesota Center for Environmental Advocacy, Friends of the Boundary Waters Wilderness, Voyageurs National Park Association, Fresh Energy and the Sierra Club.

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