Our Northwest

Avalanche bridge open, will reduce I-90 closures

Wednesday, August 10, 2016by  Jon Osterberg

new Interstate 90 avalanche bridgeThe new Interstate 90 avalanche bridge near Snoqualmie Pass opened to traffic Tuesday, a major milestone in the project to widen 15 miles of mountain freeway.

All four I-90 lanes – eastbound and westbound, two lanes in each direction – now crowd the bridge temporarily. Construction begins immediately on a parallel avalanche bridge, which will open in 2018. Once done, it will carry three lanes of westbound traffic, while today’s newly opened bridge will convert to three lanes of eastbound traffic.

Both bridges will have shoulders in 2018. Until then, traffic will be pinched through a narrower space along the work zone.

By opening the bridge now, workers can begin blasting rock and excavating avalanche chutes that will funnel snow under the bridges and into Lake Keechelus.
avalanches occasionally buried I-90, That’s a big deal. In the past, avalanches occasionally buried I-90, prompting closures until snow could be removed. Initially the solution was to build a longer snowshed as part of the $1 billion freeway upgrade. Then came a better idea: Instead of a snowshed, build less-costly avalanche bridges that will carry traffic above any snowslides.

I-90 commuters have long dealt with Snoqualmie Pass snowfall that’s averaged 428 inches per year since 1949, according to Washington State Department of Transportation data. Last winter alone, I-90 was closed 76 hours for avalanche control.

Of course, last winter there was no Keechelus snowshed to deflect avalanches, the shed having been demolished in 2014 as part of the road project. But even in earlier years when the snowshed was intact, motorists endured many closures because of heavy snowfall, such as in the winter of 2011-12.
future I-90 wildlife overpass Watch for the next big milestone in the I-90 project: Phase 2 will bring new wildlife overpasses near the site of the former Price Creek rest stop.

Photos courtesy of WSDOT

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