Park avalanche was Class 5 monster

An avalanche that crossed the Sun Road twice and ran beyond the Packer's Roost Road was the largest of its kind, Glacier Park avalanche experts said last week.

The slide, which started on the Garden Wall above the Sun Road at Alder Creek, ran nearly 4,000 feet and had a wind blast that busted off Douglas Fir trees that looked to be more than 100 years old. It was considered a Class 5 avalanche — the largest and most destructive.

The slide had incredible momentum, said Mark Dundas, as it crossed two football field-sized flat areas above the Sun Road before it hit the highway, running about two linear miles.

"Normally they lose their momentum" across flat areas, Dundas said.

Park plow foreman Stan Stahr said in his nearly 15 years as a crew member this was the largest slide he'd seen. It's suspected that the avalanche happened on or about Jan. 8, when heavy rains fell on a large snowpack.

The Sun Road at Alder Creek looks as if it were hit with a large hammer. The road has big fractures in the asphalt and more than 500 feet of stone wall are gone. About 85 feet of wall was rebuilt in 2008. The remainder dated back to the 1920s.

John Schnaderbeck, construction project manager for the Federal Highway Administration, said he estimates the damage at about $200,000 to $300,000 and said the plan right now is to not replace the wall, but to put in barrier rocks and shore up the shoulder of the road.

Schnaderbeck said to rebuild the wall costs about $1,300 a foot, and with future threats of avalanches, it doesn't make sense to replace the wall at this point.

He said the damage shouldn't delay the opening of the road and it should be in two-lane condition by early July.

Funds for the repair will come from a modification to the existing contract to repair the highway, he said.