Snowmobiles would become a permanent winter fixture in Yellowstone National Park under a proposal, drafted by park administrators and released Tuesday, that would allow 720 lower-polluting machines daily.
The policy change would continue rules in place for the past three winters, although actual snowmobile use has averaged only about 250 machines per day.
The National Park Service’s proposal is a setback for conservation groups and some former park employees who had sought an outright ban on snowmobiles. The plan would also allow 78 bus-like snowcoaches per day in the park; there is no current limit.
The park service proposed such a ban in 2000, but it was never enacted because of legal challenges. In the late 1990s, as many as 1,400 snowmobiles a day visited Yellowstone, contributing noise and air pollution that critics in Congress and elsewhere said was inappropriate for the country’s first national park.
Park administrators said Tuesday that changing technology — particularly the introduction of quieter, less-polluting engines — allowed them to back off a ban and still reduce pollution.
“It’s a night-and-day change between the way it used to be and the way it is now,” said John Sacklin, who led the team that drafted Tuesday’s proposal.
But others argue that snowmobiles in any significant numbers degrade the park and that visitors should be limited to snowcoaches.
Denis Galvin, former deputy director of the National Park Service, said snowcoaches render snowmobiles as obsolete as stagecoaches. “Their time has come and gone,” he said.
On Monday, seven former National Park Service directors stated their opposition to increased snowmobile use in Yellowstone.
Carbon monoxide pollution from snowmobiles, at 4,000 pounds a day under the current proposal, would be four times higher than the snowcoach-only alternative, the park service said.
Yet that is just 6 percent of the 68,000 pounds of carbon monoxide released in 1999, when snowmobiles were unregulated. Similar decreases are projected for hydrocarbon and particulate pollution.
In neighboring, much smaller Grand Teton National Park and in a parkway connecting the two, 140 snowmobiles would be allowed daily.
The new rules still face public review but are expected to be in place for winter 2007-08.
Tuesday’s proposal came out of an environmental study of winter activity in Yellowstone that considered options ranging from eliminating all motorized travel in the park to allowing 1,025 snowmobiles a day.
The impact statement concluded that the “environmentally preferred alternative” for the park would be no snowmobiles at all. But Yellowstone Superintendent Suzanne Lewis said that does not meet other priorities of the park service, such as allowing public access.