AECON is making progress on the I-90-SR 18 Interchange Improvements project in Washington, installing 50-ton girders for a new bridge over Raging River. The upgrades aim to alleviate congestion and improve traffic flow in response to growing demand in Snoqualmie Valley. Wildlife enhancements and fish barrier removal are also incorporated.
Photo courtesy of WSDOT
Construction crews from AECON utilized two hydraulic cranes to install four girders, each weighing more than 51 tons, more than 50 ft. above the Raging River for the new SR 18 bridge.
Construction crews from design-builder AECON are progressing on the Washington Department of Transportation's (WSDOT) nearly $200 million I-90 — SR 18 Interchange Improvements project.
Photo courtesy of WSDOT
As part of the overall project, the construction of a new bridge along SR 18 near Snoqualmie is a major part of the upgrades. Recently, crews installed four girders more than 50 ft. above the Raging River. The new bridge will span the entirety of the Raging River valley. Each girder section weighs more than 51 tons, which were lifted into place with two large hydraulic cranes.
When complete, this second Raging River bridge will carry two lanes of westbound SR 18, while the existing bridge will carry two eastbound lanes. The project already has seen the construction of a new four-lane bridge over Lake Creek and crews are building another four-lane bridge over Deep Creek just east of the existing roadway.
Growth in Snoqualmie Valley has made the I-90/SR 18 interchange one of the busiest in the state, causing backups during peak times and busy travel weekends. To improve traffic flow, WSDOT has handed out contracts for numerous upgrades that include:
- Design and construction of a four-lane diverging diamond interchange;
- Widening of SR 18 to four lanes from the interchange to Deep Creek;
- Design and construction of a four-lane bridge over Deep Creek and a two-lane bridge over Raging River.
"The diverging diamond interchange will improve the flow of traffic by reducing the number of traffic signals and offering more free turns for drivers entering and exiting the interstate," AECON said in a statement. "Growth in Snoqualmie Valley has resulted in the current I-90/SR 18 interchange being one of the busiest in Washington State."
Photo courtesy of WSDOT
The first stage of construction began in April 2023. Contractor crews cleared trees in the project area to begin work on the new interchange and highway widening.
To create enough space on SR 18 for a safe work zone, WSDOT and its contractor reduced lanes to one lane in each direction and shifted traffic to the east side of the roadway. In August 2023, crews shifted traffic to west side of the newly constructed Lake Creek bridge.
A variety of construction activities are taking place throughout the project area. Some of this work includes:
- Building the new two-lane bridge over Raging River on SR 18, which will carry westbound traffic next to the current bridge;
- Building the new four-lane bridge over Deep Creek on the east side of the roadway;
- Finishing touches on new four-lane bridge over Lake Creek;
- Grading area for two new SR 18 between Deep Creek and I-90;
- Grading and preparing areas for new on- and off-ramps between I-90 and SR 18 at the new interchange;
- Building a new drainage system at the interchange;
- Ongoing maintenance and roadway repairs as needed;
- Removal of the old weigh station near the westbound I-90 on-ramp (completed).
Removing Fish Barriers, Enhancing Wildlife
As part of this project, WSDOT will remove six fish passage barriers in the area. Crews also will install two new fish-passable crossings at Deep Creek and Lake Creek. These new stream crossings will restore access to 13 mi. of stream habitat that is essential for populations of salmon, steelhead and other aquatic species. The new bridges built for highway widening also will allow wildlife to pass safely beneath roadway instead of over it.
In the Deep Creek watershed, this project will open access to 11.2 mi. of stream habitat, including approximately .75 acres of spawning area and 2.34 acres of rearing habitat. These fish are important resource for Tribes through their treaty rights with Washington and also as forage for endangered Orca in Puget Sound.
About Project
Growth in Snoqualmie Valley has made the I-90/SR 18 interchange one of the busiest in the state, causing backups during peak times and busy travel weekends. To improve traffic flow, WSDOT is building a diverging diamond interchange and adding two lanes on SR 18 between the interchange and Deep Creek.
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