100-year avalanche damages Sun Road
By ERIC NEWHOUSE • Tribune Projects Editor • May 17, 2009
A "once-in-a-century" avalanche wiped out 550 feet of guard wall along the Going-to-the-Sun Road just west of the Continental Divide, Glacier National Park officials said last week.
"It was huge," said Jack Gordon, Glacier Park's roadway project manager.
The Little Granite Creek avalanche — a Class-5 avalanche, the most catastrophic listing — damaged the alpine Sun Road just above the Loop, then crossed the road again just below the Loop, and roared over the Packers Roost Road before it came to a halt 4,300 feet below.
"The damage was discovered by a crew plowing in the area of Alder Creek on April 30," said park spokeswoman Amy Vanderbilt. "Unfortunately, we haven't been able to get our engineers back in there to assess the damages and make a report."
However, Gordon and Jim Foster, the park's facilities manager, made it to the scene last week to inspect the damage, much of which was in the section of road already scheduled for repair this year.
"It took out 460 feet of historic stone masonry that had been there since the late 1920s," Gordon said. "It's completely gone."
About 180 feet of the road's asphalt also was damaged, but the road remains intact.
Gordon estimated repair costs for the section of damaged road could be less than $500,000.
"However, this is a newly identified avalanche zone, so we may be looking at a different type of construction, perhaps barrier rock," Vanderbilt said.
Gordon said barrier rocks are 2-ton boulders buried in the roadbed to withstand catastrophic events such as avalanches.
Just down the road from that damaged stretch, the avalanche took out another 95 feet of guard wall, installed last summer at a cost of $120,000.
"It just sort of peeled the wall away from the asphalt," Gordon said.
The only major damage was to two sections of Sun Road above the Loop at Alder Creek, which feeds down from the Granite Chalet, Foster said. Alder Creek is known locally as Little Granite Creek.
"We had a large snowfall around the first of the year, followed by a major rain," he said. "Our avalanche forecasters say the rain permeated the entire snowpack, and it all cut loose.
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