The National Parks Conservation Association, and the San Juan Citizens' Alliance, claim the relaxed rules would clear the way for construction of the proposed Desert Rock coal-fired power plant in northern New Mexico, further endangering air quality and visibility at Mesa Verde National Park.

The agencies held a news conference at Mesa Verde on Wednesday to voice their concerns, saying the EPA was preparing to complete the new rules. Similar events were held at Zion and Capitol Reef national parks in Utah.

Mike Eisenfeld, the New Mexico energy coordinator for the San Juan Citizens Alliance, said the news conference at Mesa Verde marked his first visit to the park in two years.

"I was shocked. The visibility up there has decreased significantly since I was there last," Eisenfeld said.

He blamed the existing Four Corners Power Plant and San Juan Generating Station - both of which are coal-fired plants - for deteriorating air quality at the park that he believes would be made only worse with the addition of Desert Rock about 45 miles to the south.

"We knew all along we're already overwhelmed with these facilities, and to add another would be devastating - air quality is not getting any better around here."

Among the rule changes is a provision that would change how and when air quality is measured in Class 1 regions, which include 48 national parks. Under provisions of the 1977 Clean Air Act, measurements are taken at short- and long-term intervals to measure spikes during peak usage time as well as long-term averages. The proposed change would eliminate the shorter three-hour interval measurement, which proponents of the changes claim is a better representation of emissions in Class 1 regions.

Jeff Holmstead, the head of the environmental strategies group at Bracewell & Giuliani, the law firm that represents Sithe Global and the Desert Rock project, said the environmental groups are simply focusing on worst-case scenarios. Holmstead was in charge of the EPA's air pollution control office when the proposed changes were drafted in 2005.

"This is just the worst example of the environmentalists trying to stir up public opinion over something that doesn't really matter. What the EPA is saying now is, 'Let's use the appropriate tools, but not raise the highest hurdles we can.' The environmental community wants it to be this way because it gives them leverage; it makes it easier to stop an individual project because otherwise it will foul the air in our national parks. But it's just not true," Holmstead said.

Opposition to the rule changes, however, is coming from sources other than the environmentalists. A document from the National Parks Conservation Association cites eight of the 10 regional EPA offices denouncing the changes being proposed by the federal office in Washington, D.C., including Region 9, which oversees the area where Desert Rock would be built.

"Allowing unlimited discretion to state and local agencies to define the 24-month period a source must use (to estimate maximum emissions) will result in underestimating actual increment consumption and is contrary to allowing informed public participation in the process," reads an excerpt from the Region 9 response to the federal office.

A call to the EPA's Region 9 office in San Francisco was not immediately returned Thursday.

Other regional EPA offices such as Region 10 called the proposed rules "full of errors" and that there was a "fundamental misunderstanding of the permit process."

"Rather than addressing the issues and giving clear guidance to permitting authorities and permit applicants, this draft proposal would further confuse the issues," wrote Region 10 in response to the proposed rules.

Legislators have also expressed their concerns. Sen. Ken Salazar, D-Colo., was one of eight senators who signed a June letter to EPA Administrator Stephen Johnson protesting the changes.

An excerpt from the letter reads: "The rule ... purports merely to clarify the way in which pollution levels in Class 1 areas are measured. However, analyses by the National Parks Service and EPA's regional air-quality experts demonstrate that the proposed changes would result in a significant undercounting of actual pollution sources, such as coal-fired power plants, permitting them to emit more pollution into national parks and wilderness areas. For this reason, the National Parks Service and every EPA regional office oppose the changes EPA has proposed."

While the EPA has not officially adopted the new rules, Eisenfeld said he and others are prepared to continue the fight even if this battle is lost. That includes the battlefield of the federal courthouse.

"I'm sure there'll be litigation, and real action will be taken if EPA turns us down," Eisenfeld said.

"We're of the opinion that the EPA should do a better job enforcing the Clean Air Act rather than ripping it apart."

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