Atkinson Construction Demolishes I-90 Snowshed to Make Way for Avalanche Bridges

May 05, 2014

HYAK, Wash. – Guy F. Atkinson reached a major construction milestone in April on the I-90 Snoqualmie Pass project: the demolition of the existing 500 foot-long snowshed. The structure's demolition, which took two days to complete, will make way for a new lane in each direction, and two new avalanche bridges. The newly built elevated structures will permit snow and rock to slide between the piers and under the bridge towards Keechelus Lake, allowing travelers to drive over the debris and reducing potential road closures due to control work.

The snowshed has kept Snoqualmie Pass open to drivers during the winter months for the past 64 years, however, the structure no longer meets the needs for a modern transportation facility. After several months of collaboration with the Washington State Department of Transportation (WSDOT), Atkinson proposed a design modification to change the type of structure that would replace the existing snowshed. Under Atkinson's proposal, eastbound and westbound avalanche bridges will be constructed instead of the expanded snowshed. The bridges will not only improve the safety of the traveling public, but save WSDOT tens of millions of dollars in comparison to the cost for the original snowshed design and maintenance.

This spring marks Aktinson's third construction season working on the I-90 Snoqualmie Pass. As the summer begins, the Atkinson crew will focus on blasting the hillside down to roadway elevation, replacing deteriorating concrete pavement, and construction of the eastbound Resort Creek Bridge to open the roadway to traffic. Atkinson also will begin building Wall 7, which includes a temporary shoring wall and a mechanically stabilized earthwall.

On an average day, 28,000 vehicles travel over Snoqualmie Pass and it doubles on weekends and holidays. Traffic volumes are expected to increase by more than two percent every year, reaching an average of over 41,000 vehicles per day by 2030. Phase 1 of the I-90 project is focused on improving safety and reliability, reducing congestion from Hyak to the Easton vicinity, and reconnecting habitats across I-90 to minimize wildlife-vehicle collisions.

For a time-lapse video of the snowshed demolition click on the image below.