National Park Service officials say a coal-fired power plant proposed in southwestern North Dakota would send too much of a haze over Theodore Roosevelt National Park.

David Verhey, a deputy assistant secretary for Interior Department, told state health officials in a letter late last month that air quality specialists for the Park Service believe the proposed 500-megawatt plant to be built by Westmoreland Power Inc., near Gascoyne would hurt visibility at the park.

Terry O'Clair, director of the air quality division of the state Health Department, said state officials believe the permit being considered for the Gascoyne plant would meet federal environmental standards.

The power plant is proposed in Bowman County, about 60 miles southeast of the south unit of Theodore Roosevelt National Park.

Officials of the Park Service are disputing the method North Dakota uses to predict smokestack emissions from the plant. State officials say the Environmental Protection Agency has not objected.

"It is our position that we do have that (EPA) approval," O'Clair said. "We're using the same method that the EPA uses. We've got very sound data."

The method, using "turbulence flow" calculations, is under review by the EPA, said John Bunyak, who oversees the National Park Service's air resources division for the Denver region.

O'Clair and Bunyak say they will keep talking to try to resolve the dispute. Both say Westmoreland Power has proposed emissions that would reduce sulfur dioxide by 25 percent and nitrogen oxide by 10 percent.

Verhey told O'Clair last summer that Theodore Roosevelt National Park has "extraordinary scenic qualities and panoramic views" that are sensitive to even small amounts of pollution.

"Although this area enjoys some of the cleanest and clearest air in the country at times, visibility impairment has been well-documented," he wrote then.

Bunyak said the Park Service wants to ensure that air quality at the park meets the most stringent clean air regulations under federal law. Reducing haze helps reduce pollutants, including acid rain contaminants such as sulfur dioxide, he said.