Glacier National Park released an environmental assessment Tuesday for the rebuilding of the Sperry Chalet dormitory with a two-year timeline for reconstruction.

The preferred alternative would reconstruct the 104-year-old historic backcountry chalet within the existing walls, with room for about 54 guests, starting this summer.

The main dormitory of the chalet complex was gutted by the Sprague Fire on Aug. 31 of last year after an ember storm started the structure on fire under the eaves, the assessment notes. That’s contrary to initial Park Service reports of the blaze, which suggested the chalet caught fire from within the building.

With financial help from the Glacier National Park Conservancy, the stone remains of the structure were stabilized last fall using a myriad of 6-inch square wooden beams. To date, the remains are still standing, having withstood the onslaught of winter.

Crews would begin July 1 and work into the fall and there would be substantial helicopter and mule traffic to ferry supplies up the site. On busy days, it will take 40 to 50 flights per day to deliver materials and tools to the site.

The work will be done in two phases.

Phase I would include additional structural investigation of the masonry walls, building a roof, and constructing seismic lateral walls in the interior. If necessary, rock from the nearby original quarry would be used to repair the remaining historic walls. Due to the unique historic character defining feature of the original stonework associated with the chalet, there is a lack of reasonably available outside sources to provide rock which matches that used in the original construction, the EA notes.

The talus that would provide the stone is within the 25-acre historic district of the site and is not in recommended wilderness.

Phase II would begin the following summer and complete the reconstruction of the dormitory including finishing the roof, constructing interior floors, framing, finishes and any remaining exterior work. Cost considerations, unforeseen events or conditions, could affect the construction schedule, the Park notes. Phase II would complete the reconstruction of the dormitory including finishing the roof, constructing interior floors, framing, finishes and any remaining exterior work.

The EA does not provide a cost estimate of the work. But preliminary “ball park” estimates have run from $6 million to $12 million, Park officials have noted.

The design itself is a hybrid to two concepts for rebuilding the chalet. It preserves the historic character, while making the structure more fire resistant in the future and brings it to current codes. It also will add more seismic stability to the chalet in the event of an earthquake, to the extent that’s possible.

During both construction seasons, the Sperry Backcountry Campground and trails from Lake McDonald and Gunsight would remain open to visitors. The Sperry toilet facility would remain open to visitor use. The horse concession may continue to offer day rides to the chalet complex subject to restrictions from construction activity with the associated increased stock use on the trail and frequent helicopter activity. All Sperry area visitor use may be subject to temporary closures, for safety reasons, during construction. Signs would be placed at the trailheads informing hikers of conditions, restricted areas and temporary closures.

A crew of 12 to 25 would live on site for the 12-week construction season.

Approximately 400,000 pounds of materials and equipment would be flown in and carried up by stock. Depending on the size of helicopters used, that would mean about 150 to 220 helicopter trips per year. In addition, there will be an estimated 35 to 60 pack string trips as well.

Trail crews will be kept busy as well, making sure the trail to the chalet is kept in good shape.

Flights would be restricted in September to morning hours, to avoid migrating eagles and other raptors that use the corridor as a migration route.

As with any backcountry activity in the Park, garbage will be secured to keep it from bears and toilet use will be enforced to keep salt-loving creatures like mountain goats from the construction area.

The Park considered, but rejected not rebuilding the chalet at all, but preserving the remains. Another alternative would be to rebuild the chalet in a different location. That, too, was rejected, after the public overwhelmingly wanted to see the old chalet restored.

A public meeting to provide comment on the environmental assessment and ask questions about the project will be held on Monday, April 23 from 5:30 pm-7:30 p.m. at Flathead Valley Community College in the Arts and Technology Building, Room 139 in Kalispell.

Comments can be submitted online at: http://parkplanning.nps.gov/SperryChalet2018, or sent by mail to Superintendent, Glacier National Park, Attn: Sperry Chalet, P.O. Box 128, West Glacier, Montana 59936. The EA may also be requested by calling 406-888-7898.