Is that a power plant on the park horizon?

The Bush administration is on the verge of implementing new air quality rules that will make it easier to build power plants near national parks and wilderness areas, according to rank-and-file agency scientists and park managers who oppose the plan.

The regulations, which are likely to be completed this summer, rewrite a provision of the Clean Air Act that applies to “Class 1 areas,” federal lands that have the highest level of protection under the law. Opponents predict the changes will worsen visibility at many prized tourist destinations, including Utah’s Zion, Virginia’s Shenandoah and Colorado’s Mesa Verde national parks.

Nearly a year ago, with little fanfare, the Environmental Protection Agency proposed changing the way the government measures air pollution near Class 1 areas on the grounds that the nation needed a more uniform way of regulating emissions near protected areas.

Jeffrey Holmstead, who now heads the environmental strategies group at the law firm of Bracewell & Giuliani, helped initiate the rule change while heading the EPA’s air and radiation office. He said agency officials became concerned that the EPA’s scientific staff was taking “the most conservative approach” in predicting how much pollution new power plants would produce.

“The question from a policy perspective was: Do you need to have models based on the absolute worst-case conditions that were unlikely to ever occur in the real world?” Holmstead said in an interview Thursday.

The initiative is the latest in a series of administration efforts dating to 2003 to weaken air quality protections at national parks, including failed moves to prohibit federal land managers from commenting on permits for new pollution sources more than 31 miles away from their areas.

For 30 years, regulators have measured pollution levels in the parks, over both three-hour and 24-hour increments, to capture increases in emissions during peak energy demand. The new rule would average the levels over a year so that the increases would not violate the law.

A slew of National Park Service and EPA officials have challenged the rule change, arguing that it will worsen visibility in already-impaired areas, according to internal documents obtained by the House Committee on Oversight and Government Reform.

The EPA’s computer modeling staff wrote that the proposal “would allow for significant degradation” of the parks’ air quality. An e-mail from National Park Service staff called aspects of the plan “bad public policy” that would “make it much easier to build power plants” near Class 1 areas.

When committee Chairman Henry A. Waxman (D-Beverly Hills) asked the EPA whether the rule would facilitate construction of more power plants near protected areas, Robert Meyers, principal deputy assistant administrator for the EPA’s Office of Air and Radiation, replied in an April 24 letter that this was not the intention but he could not rule it out.

“We developed this proposal based on the need to clarify how increment consumption must be addressed, and not whether or not it would be easier to build power plants,” Meyers wrote. “In the absence of any data or evidence provided by the National Parks Service, we are unable to conclusively confirm or deny their suggestion.”

On Thursday, the National Parks Conservation Assn., an advocacy group, issued a report estimating that the rule would ease the way for the construction of 28 power plants within 186 miles of 10 national parks. In each of the next 50 years, the report concludes, the new plants would emit a total of 122 million tons of carbon dioxide, 79,000 tons of sulfur dioxide, 52,000 tons of nitrogen oxides and 4,000 pounds of toxic mercury into the air over and around the Great Smoky Mountains, Zion and eight other national parks.

“It’s like if you’re pulled over by a cop for going 75 miles per hour in a 55-miles-per-hour zone, and you say, ‘If you look at how I’ve driven all year, I’ve averaged 55 miles per hour,’ ” said Mark Wenzler, director of the National Parks Conservation Assn.’s clean air programs. “It allows you to vastly underestimate the impact of these emissions.”