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Constructing Fish Passable Structures Under I-90 and Local Roads

Contractor crews working for the Washington State Department of Transportation will build four new bridges, digging down nearly 100 feet under the existing roadway to remove existing culverts. Construction will require lane shifts on I-90 and road closures on Southeast Eastgate Way and Southeast 36th Street. Once complete, this project will create a natural stream bed to flow under I-90 and open access to nearly two miles of restored habitat for salmon and steelhead.

Construction along I-90 starts in 2023 and will continue through 2026. People traveling and living in the area can expect:

  • Long-term lane reductions and lane shifts for both directions of I-90
  • A single lane of alternating traffic on Southeast 36th Street for up to 1.5 years
  • A six-month full closure of Southeast Eastgate Way
  • Temporary shift of the Mountain to Sound Trail and Sunset Ravine Trail
  • Stream restoration, adding native plants, logs and boulders to support fish habitat

Shifting Traffic in Stages

Construction crews will shift traffic in stages to build four new bridges – two under I-90, one under Southeast Eastgate Way and one under Southeast 36th Street. Each traffic shift will last for several months while crews excavate and replace culverts. Up to five lanes of traffic will always be maintained, and bike and pedestrian trails will be detoured. Major traffic stages are illustrated below.

Spring 2023 – Summer 2023

I-90 West Fish Passage – Sunset Creek construction stages 1 and 2
  • As early as May 15, crews will close the eastbound I-90 HOV lane to shift traffic around the construction zone.
  • Crews will widen the Southeast 36th Street sidewalks for a Mountain to Sound Greenway Trail detour.
  • In summer, crews will shift I-90 eastbound traffic into a new configuration while the southern portion of the I-90 fish passage bridge structure is built.
  • Lanes will be reduced on Southeast 36th Street to a single one-way road with signalized, alternating traffic.

Fall 2023 – Spring 2024

I-90 West Fish Passage – Sunset Creek construction stages 3 and 4
  • Eastbound I-90 traffic will shift to the right lanes of the new eastbound bridge to allow crews to construct the remaining north portion of the bridge.
  • Once the eastbound bridge structures are complete, crews will shift traffic on westbound I-90 to build the north portion of the I-90 bridge and Mountain to Sound Greenway Trail.

Spring 2024 – Fall 2026

I-90 West Fish Passage – Sunset Creek construction stages 5, 6 and 7
  • Crews will shift traffic to the final configuration on eastbound I-90 and on Southeast 36th Street.
  • Crews will shift westbound I-90 traffic to build the build the remaining south portion of the fish passable bridge structure on I-90.
  • Crews will close South Eastgate Way Bridge for up to 6 months to complete construction on the Southeast Eastgate Way Bridge.
  • Major construction will be complete by fall 2026.