A draft winter-use plan for Yellowstone National Park redefines over-snow entries into the park under a system that stands to increase the number of over-snow vehicles into the park beyond the total that has been permitted in past winters.

The plan, expected to be formally released in the coming days, 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 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.

Additionally, the preferred alternative in the draft plan would allow some non-commercially guided trips into the park -- one per day through four of the park's entrances with a maximum five snowmobiles in each party -- and allow Sylvan Pass to continue to be groomed for over-snow travel.

But before they were removed, the Yellowstone Gate blog managed to grab the documents and posted them on its site. According to those documents, the preferred alternative potentially could allow 480 snowmobiles into the park on any one day. However, the documents continue, "this level of use would not occur every day because commercially guided group sizes must average 7 over the season, and noncommercially guided groups could not exceed a group size of 5."

Yellowstone officials had hoped to have the winter-use plan in effect for last winter, but in September Superintendent Dan Wenk said more questions needed to be resolved before he would be satisfied with a plan to protect the park's resources yet allow for over-snow visitation.

For more than a decade the debate over how winter in Yellowstone should be enjoyed has dragged on. The Park Service has gone back and forth with the political winds, calling back in 2000 for recreational snowmobile use to be phased out completely only to see the Bush administration drop that decision in favor of continued snowmobile use.

Legal battles waged by those who want continued snowmobile use and those who believe Yellowstone would be healthier without snowmobiles have prolonged the debate and led to a fistful of environmental studies -- environmental assessments as well as more complex and detailed environmental impact statements.

The latest winter-use proposal contains three other alternatives. The “no action” alternative would end all public snowmobile and snowcoach travel in the park. Alternative 2 would allow for winter oversnow access by snowmobile and snowcoach at the same levels as permitted in recent years under a series of temporary rules. Alternative 3 would phase-out snowmobiles and provide for an increased number of BAT snowcoaches. This alternative would close Sylvan Pass in the winter.

Under each of the alternatives there would be a two-year transition period before the approved approach took effect.

Park staff members will host a series of open houses during the public review and comment period:

* Monday, July 16 at The Virginian Lodge, 750 West Broadway in Jackson, WY

* Tuesday, July 17 at the Holiday Inn, 315 Yellowstone Ave. in West Yellowstone, MT

* Wednesday, July 18 at the Wingate by Wyndham, 2305 Catron St. in Bozeman, MT

* Thursday, July 19 at the Holiday Inn, 1702 Sheridan Ave. in Cody, WY

All four open houses will run from 6:30 p.m. to 8:30 p.m.