It took six years, and a lawsuit from the National Parks Conservation Association and other environmental organizations, but the U.S. Environmental Protection Agency has agreed to look into the source of air quality problems at Voyageurs National Park in Minnesota and at nearby Isle Royale National Park in Michigan.

In a notice posted in the Federal Register on Friday, the EPA said it had reached a proposed consent decree with the organizations that would establish deadlines for determining whether the visibility problems stemmed from "emissions from Xcel Energy's coal-fired Sherburne County Generating Station in Minnesota."

NPCA officials have maintained that "(T)he pollution created by the 37-year-old Sherco plant is unhealthy for people and is a major contributor to the haze that obscures views at Voyageurs and Isle Royale national parks, and the Boundary Waters Canoe Area Wilderness. As a result of this agreement, EPA will act on a 2009 certification by the National Park Service that Sherco is impairing national park visibility."

Under the consent decree, if finalized, the EPA will propose an action plan for addressing the alleged air pollution source by Feb. 27 of next year, and finalize it by the end of next August.

"If EPA determines that visibility impairment in Voyageurs National Park or Isle Royale National Park is reasonably attributable to Sherco, then EPA's final rulemaking shall also include EPA's final determination of BART (best available techology retrofit) for Sherco," the Federal Register notice said. "However, if EPA determines that visibility impairment in neither Voyageurs National Park nor Isle Royale National Park is reasonably attributable to Sherco, then BART for Sherco will not be required."

At NPCA, Stephanie Kodish, director and counsel for the Clean Air Program, called the development "a major step toward clean air in Boundary Waters, Voyageurs and Isle Royale. At last, ... we can say that EPA is going to act. Now we need to make sure that EPA’s action is as strong and meaningful as the Midwest deserves.”