Contractor selection marks milestone for I-90/SR 18 interchange improvement project near North Bend

$190 million project includes widening SR 18, new bridges, and fish passages

NORTH BEND – The long-awaited improvement project at the interchange of Interstate 90 and State Route 18 is another step closer to reality following the selection of a contractor.

Aecon Pacific Northwest, Inc. submitted the best value proposal to complete the design and build the project following a competitive evaluation process.

“Aecon has built large highway, civil and private projects across the U.S. and Canada,” said Washington State Department of Transportation Project Engineer Mark Allison. “This is a significant project and one the community has anticipated for a long time. We look forward to working with Aecon to build an interchange that will serve people for many years to come.”

The I-90/SR 18 improvement project is design-build, which means WSDOT executes a single contract with one firm for design and construction. Design-build projects offer efficiencies in cost and scheduling. Construction is expected to begin later this year with completion in 2025.

Diverging diamond interchange

The I-90/SR 18 project will feature a diverging diamond interchange, which improves the flow of traffic by reducing the number of traffic signals and offering more free turns for drivers entering and exiting the interstate.

Diverging diamond interchanges are used around the world, with more than 100 operating in the United States. Washington’s first diverging diamond interchange opened in August 2020 at Interstate 5 and State Route 510 in Lacey.

SR 18 and Snoqualmie Parkway improvements

The I-90/SR 18 project also includes:

  • Widening approximately 2 miles of SR 18 from the interchange to Deep Creek, creating two lanes in each direction.
  • Construction of a new four-lane bridge over Deep Creek and a new two-lane southbound bridge over Raging River.
  • Adding a dedicated right turn lane from southbound Snoqualmie Parkway to westbound I-90.

Aecon Pacific Northwest, Inc. will begin work by completing design work for the interchange, a wider SR 18, new bridges and improved fish passages.

The $190 million project is funded through pre-existing gas tax funds and the 2015 Connecting Washington transportation fund, which is a $16 billion investment that enhances the statewide transportation system and maintains critical infrastructure.  

8,683 animals crossed the Snoqualmie Pass East Project area

as recorded by WSDOT and partners in 2020 and 2021.

46% increase in Amtrak Cascades ridership to 251,000 passengers

in 2021 compared to 172,000 in 2020.

Nine wetland and stream mitigation sites across 32.7 acres added

to our monitoring program in 2021 to help offset climate change impacts.