Claims by Yellowstone National Park officials that a preferred winter-use plan will result in a cleaner, quieter park open to more visitors seem to be contradicted by data contained in documents upon which the plan is built.

While Superintendent Dan Wenk said Thursday that the preferred alternative "makes the park quieter and cleaner, and allows some increases in visitation," data show that that desired alternative will result in substantially higher carbon monoxide levels. Benzene emissions also will increase in the near-term, as will levels of formaldehyde and acetaldehyde, according to numbers contained in the Draft Winter Use Plan Supplemental Environmental Impact Statement.

As for noise levels, the draft clearly states on page 262 in Chapter 4 that, "(A)ssuming the maximum allowed use levels, OSVs (over-snow vehicles) would be audible over 50 percent of the time in approximately 14.1 percent to 17.4 percent of the travel corridor area, compared to 9.7 percent of the travel corridor area under recent average conditions."

But Wade Vagias, the superintendent's management assistant who has been deeply involved in developing the winter-use plan, said those numbers are at the very high end of the spectrum, and not what likely would be realized on a daily basis.

"I think the first point to understand is that the courts require us to look at, basically, the worst day, not necessarily current conditions," he said following an hour-long telephone conference call during which he and Superintendent Wenk explained the Draft SEIS. "And so when we talk about cleaner and quieter, what we see is that we can achieve that when we look against the 318/78 rule (snowmobiles and snowcoaches allowed per day under the temporary winter-use plan.)

"Now, in the case of carbon monoxide, where you see those elevated levels, and it goes from minor to moderate (impacts), is simply at the West Entrance. And we believe it's a function from queuing. Basically the vehicles are in two lines coming in the entrance there."

Putting that aside, Mr. Vagias said that even at the highest levels of carbon monoxide predicted in the modeling, the overall impact to Yellowstone's air quality would be minimal and inconsequential.

"I would tell you that if we were starting winter-use planning today, set aside the past 12 years, air quality would be an issue that is basically considered, but dismissed because these levels are so low. Even the carbon monoxide," he said. "The national ambient air quality standards -- we're a Class I clean air area -- we are way, way down. And in fact, when we look at it now ... I've got to tell you, the best available technology, which is all 4-strokes, it may some day include 2-stroke motors, the emissions that they are putting out are so low, the sum number of vehicles that there are, it wouldn't even be a concern if we were starting this process today."

The Draft SEIS is the fifth environmental impact statement -- and seventh environmental study overall -- the National Park Service has produced in more than a decade of trying to devise an acceptable plan for welcoming visitors to Yellowstone in winter. Three of those EISes were rejected by the courts. The most recent EIS was tossed out in 2008 by U.S. District Judge Emmet Sullivan, who said it ran counter to the Park Service's conservation mission.

The latest plan calls for the park to "manage oversnow vehicles by their overall impacts to air quality, soundscapes, wildlife, and visitors, rather than focusing solely on the number of snowmobiles and snowcoaches allowed in the park each day. The park would allow up to 110 'transportation events' a day, initially defined as either one snowcoach or, on average, a group of seven snowmobiles (maximum group size would be capped at 10). No more than 50 transportation events a day would be allocated for groups of snowmobiles."

Using that formula, if 50 "transportation events a day" were allocated for snowmobile groups, and those groups averaged seven machines, then approximately 350 snowmobiles would be allowed into the park on one day. With another 60 "transportation events" allocated for snowcoaches, that would mean daily over-snow entries could reach 410.

Under the temporary winter-use plan regulations in use the past two winters, a maximum 318 snowmobiles and 78 snowcoaches a day were allowed into the park.

While the voluminous draft SEIS is still being digested by many groups, some who have read through question whether it is in the best interests of Yellowstone's natural resources and wildlife.

"It boggles the mind why NPS would increase the daily allowance of snowmobiles when the vehicles are more noisy and polluting than models from seven years ago," Kristen Brengel, director of legislative and government affairs for the National Parks Conservation Association, said in an email. "If the technology is not improving, why are the manufacturers being rewarded? This is not good stewardship."

At the Greater Yellowstone Coalition, Executive Director Mike Clark also was disappointed with the Park Service's approach towards winter-use in Yellowstone.

"I think it's going to sow a lot of confusion in the public. I think it's too complex. And does not resolve the issues of management and control with any clarity," he said from his Bozeman, Montana, office. "It's perplexing. Snowmobiles are getting dirtier and noisier, and Dan acknowledged that today. Snowcoaches are getting cleaner, and yet the plan seems to give weight to the fact that the park is hoping that the snowmobile industry will clean up its act. It's never done that, and clearly has had plenty of time to do it but has chosen not to do that in Yellowstone.

"So I don't quite see why the park seems to be insistent on giving snowmobiles advantages that no one else enjoys," added Mr. Clark. "I don't understand what Dan is responding to. It seems to me the science is very clear. Every time they've run the numbers, snowmobiles are not good for the park. This is the seventh time they've made a run at this and every time the results, in terms of science, are the same. So I don't know what kind of political pressure is being applied that would make them do something different from what the science says."

Superintendent Wenk did acknowledge that the snowmobile industry has not lived up to promises to make cleaner, quieter machines. Yet he said the technology exists to manufacture cleaner, quieter snowmobiles, and he was optimistic the industry would bring them to the park.

"We're not asking them to do something that can't be done," the superintendent said during the telephone conference call.

Under the park's proposed plan, the new daily snowmobile and snowcoach limits would take effect for the 2014-15 winter season, while the new emissions and noise limits would take effect beginning with the 2017-18 winter season.

“Visiting Yellowstone in the winter is an incredible experience that’s been enjoyed by millions of people over its history," the superintendent replied when asked his philosophy towards winter-use in Yellowstone. "We have seen that during the period of unlimited use there were high impacts to wildlife, to air quality, visitor experience. And since 2000 we have struggled and we have been planning for what is that appropriate level of use to ensure that the park is protected, first and foremost, and that we allow for an appropriate level of visitor use and enjoyment.

"The different planning efforts have struggled to find that balance," he added. "We believe that by looking at this in terms of 'transportation events' and limiting the kind of impact that can occur in the park, we have developed a management paradigm that ensures the long-term protection of the park and does allow for some increase in the visitor opportunities and growth while ensuring that protection of the park.”