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Jackson Hole, WY News

SECOND IN A SERIES

A world without avalanche closures

Avalanche bridges and snow nets on Snoqualmie Pass have eliminated slides hitting the road.

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Snoqualmie Pass avalanche control infrastructure

As Interstate 90 passes over Snoqualmie Pass the avalanche mitigation infrastructure installed during a recent project protects motorists. The infrastructure — snow nets, right, which hold snow in place, and an elevated bridge that allows snow from slide paths to pass beneath the roadway, visible at left in the distance — didn’t come cheap: The total cost of the project had a $550 million price tag.

In the late 1960s, Wyoming’s highway engineers had a novel idea.

As the Wyoming Department of Transportation planned Highway 22 over Teton Pass not much could be done with the road where it passed under the Twin Slides avalanche path because of the narrow constriction at the top of the pass.

Glory Bowl bridge

In the summer of 1969, the Wyoming Highway Department began construction of a bridge that was meant to span the bottom of Glory Slide, allowing avalanches from Glory Bowl to slide beneath the bridge and thus keep the roadway clear of debris. However, a massive avalanche on Jan. 22, 1970, severly damaged the partially-completed structure.

Highway Department scraps avalanche bridge

In April 1970, the Wyoming Highway Department decided to abandon the idea of a bridge spanning Glory Bowl after a bridge under construction was heavily damaged by an avalanche earlier that year.

Snoqualmie Pass avalanche control infrastructure

Washington State Department of Transportation avalanche program manager John Stimberis said the avalanche mitigation work does its job.

Snoqualmie Pass

The small hamlet of Snoqualmie Pass serves as a base area for three nearby ski operations, as well as a stop for travelers along Interstate 90, the primary corridor for commerce travel between eastern Washington and Seattle. The recent reconstruction project that updated the infrastructure to mitigate the impact of avalanches in the interstate is along Keechelus Lake, visible east of Snoqualmie Pass in the distance at upper left.

Snoqualmie Pass avalanche control infrastructure

Avalanche mitigation infrastructure put in place on Interstate 90 near Snoqualmie Pass, Washington, during a recent reconstruction project include an elevated bridge that allows snow from slide paths to pass beneath the roadway.

Snoqualmie Pass avalanche control infrastructure

The snow nets on Slide Curve, nearly a mile of them, add compressive support to the snowpack, which keeps avalanches from releasing in the first place. Washington State Department of Transportation avalanche program manager John Stimberis said the slope hasn’t slid since the nets were installed.

Snoqualmie Pass avalanche control infrastructure

Avalanche control infrastructure put in place on Interstate 90 near Snoqualmie Pass, Washington, during a recent reconstruction project include a large array of snow nets, which hold snow in place so it doesn’t slide onto the highway below.

Contact Tom Hallberg at 732-7079 or thallberg@jhnewsandguide.com.

Tom Hallberg covers a little bit of everything, from skiing to long-form feature stories. A Teton Valley, Idaho, transplant by way of Portland and Bend, Oregon, he spends his time outside work writing fiction, splitboarding and climbing.

Brad Boner has worked as a photojournalist for 25 years and has directed the News&Guide’s visuals since 2004. He lives on the west side of the Tetons with his wife, two kids, a grumpy cat and Rosie the red heeler.

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