Yellowstone National Park's winter-use management plan, which has been criticized for being too weak in defending the park's resources from impacts, was approved today by the National Park Service's Intermountain regional director.

Under the plan, which, barring any legal challenges, won't take effect until the winter of 2014-15, a group of 10 snowmobiles would be seen as one "transportation event" instead of 10 snowmobiles entering the park.

The plan would allow up to 110 transportation events per day; these events are defined as a group of seven snowmobiles or one snowcoach. However, the seven-snowmobiles-per-event would be the seasonal average; there could be times when as many as 10 snowmobiles are packaged in one group. Up to 50 of these events could involve groups of snowmobiles.

"Commercial tour operators will be able to use their allocated transportation events for snowmobiles, snowcoaches, or a mix of both, as long as no more than 50 of the authorized 110 daily transportation events are snowmobile events," a park release explained. "By relying upon user demand to determine the best mix of oversnow vehicle (OSV) use and focusing on the impacts of OSV use on park resources, the transportation event concept protects park resources and allows appropriate access."

Back in June a coalition of groups that included the National Parks Conservation Association and the Coalition of National Park Service Retirees charged that the park's proposed alternative was weak in the time it allows to pass before fully implementing "best available technology" standards for over-snow vehicles, by not requiring non-commercially guided snowmobiles to meet those BAT standards, and by failing to explain how the park plans to keep noise from being a "major adverse impact" on Yellowstone.

"NPS’s plan contains thoughtful strategies to reduce adverse impacts to the park. However, it also maintains deficiencies identified in the judicial opinions that overturned Yellowstone’s 2003 and 2007 plans," the groups wrote at the time. "The public and the park need the Obama Administration not to repeat these errors."

The Record of Decision can be found here. The groups that had criticized the draft plan were analyzing the ROD to see if their concerns had been addressed.

Yellowstone Superintendent Dan Wenk thought the plan did provide sufficient protections for the park's air, water, lands, wildlife, visitors and employees.

“This winter use plan is the product of hundreds of hours of public involvement, is based on sound science, and is a different approach to winter use management. The Plan/SEIS and ROD provide mechanisms to make the park cleaner and quieter than ever before authorized, allow greater flexibility for commercial tour operators, reward oversnow vehicle innovations and technologies, and permit increases in visitation,” Superintendent Wenk said in the release.

Under the plan, snowmobile and snowcoach use of Sylvan Pass via the park's East Entrance would continue, despite the high cost to the Park Service of protecting the pass from avalanches and the use of artillery rounds to help with the task.

According to Yellowstone officials, the coming winter season will be a transition year during which the park will allow OSV under the same conditions in place for the past four winters. The one-season transition period will also allow time for the NPS to advertise and award concession contracts and for commercial tour operators to prepare for the shift to management by transportation events.

Because the regional director’s decision will allow OSV use in the park, a regulation must be promulgated before the decision can be implemented. A final regulation is expected to be published in the Federal Register in early fall.