Avalanche won't stop Sun Road opening

Whitefish Pilot

A large-scale slab avalanche that slid 4,000 vertical feet from the Continental Divide across the west side of Glacier National Park's Going-to-the-Sun Road in January left a debris field about a third of a mile across the upper section of the highway.

Uprooted and broken trees mixed with rock and snow extended across three gullies above the road. Vegetation on the ridge between the two northernmost gullies — alder, very small trees and bushes — appeared to be untouched.

Park engineers confirmed that a 95-foot section of stone masonry wall built last year was lost, along with about 450 feet of historic masonry built in the 1920s. About 200 feet of paved road was also damaged. The new asphalt has a 40-foot long fracture in the downhill lane of the highway, where the force of the avalanche bent the pavement down.

The section of the highway that sustained avalanche damage is in the vicinity of Alder Creek, about 2 1/2 miles above The Loop. Park officials say there is less damage than expected, considering the size of the event.

"At this point, we see no reason why the entire Sun Road won't open to vehicle traffic when plowing is completed," Park superintendent Chas Cartwright said, "and when road and weather conditions permit, the entire 50-mile long historic landmark roadway to open across Logan Pass."

Park spokeswoman Amy Vanderbilt said Monday that a "rough" estimate of the damage was about $500,000.

The Class 5 avalanche was part of a series of avalanches that roared down the mountainside around Jan. 8. Avalanche material that already covered lower-elevation portions of the Sun Road very likely protected that portion of the highway from damage. Park avalanche specialists believe it's unlikely that an avalanche nearing this scale and magnitude has occurred for many decades.

The avalanche specialists surmise that heavy rain fell on top of a large accumulation of new snow and percolated through the snowpack, filtering down to the ground/snow interface. This caused an avalanche that started just below the Continental Divide along the Garden Wall. This section of the highway was not previously identified as a known avalanche zone along the Sun Road.

Additional small avalanches continued to slide down onto the highway last week. Bikers who ventured to where plow crews had stopped on Saturday, about a mile from Big Bend, had to cross four new slides that ranged from 50 to 150 feet wide.