Replacing I-90 snowshed with bridges will cost slightly less than building expanded snowsheds, and reduce necessary avalanche control work (seen here).
The snowshed is coming down on Interstate 90 near Snoqualmie Pass , and bridges are going up as part of a 15-mile corridor improvement project by the Washington State Department of Transportation.
On Tuesday, March 12, the Federal Highway Administration and the Washington DOT approved environmental documentation for the I-90 Snoqualmie Pass East project, giving the contractor the green light to build two new elevated bridges in place of the proposed wider snowshed.
The design change came after several months of collaboration between WSDOT and contractor, Guy F. Atkinson Construction. When complete, the new bridges will take traffic up and over a series of engineered avalanche paths designed to direct future sliding snow, rock and debris between the piers and towards Keechelus Lake.
This design will reduce the number of closures of I-90 due to avalanche control work as well as reduce maintenance and operations costs.
“This change will add no additional cost to this contract, it will actually save WSDOT approximately $650,000 per year that would have been used to maintain fire and life safety systems in the snowshed,” said Don Whitehouse, WSDOT regional administrator. “The innovative design of the new bridges will keep I-90 open during the winter.
Replacing the snowshed with bridges represents a change from the original plan in the 2008 Final Environmental Impact Statement, which resulted in the selection of a new, expanded snowshed.
The supplemental EIS and Record of Decision, which will be published in the Federal Register on March 22, conclude both options result in similar impacts to natural resources and would cost about the same to construct – approximately $71 million.
Construction of the bridges will begin later this year as part of Phase 1 of the 15-mile I-90 Snoqualmie Pass East project.