Snoqualmie drivers should use alternate routes and plan for extra travel time starting the night of May 15, 2025, when the Washington State Department of Transportation (WSDOT) will close both directions of SR 18 underneath I-90 for more than five days to build the southern end of the new diverging diamond interchange.
This extended closure should allow crews to complete the interchange portion of the I-90/SR 18 Interchange Improvements project by this summer.
Lane Closure Details
From 9 pm. Thursday, May 15, through 5 am Wednesday, May 21, traffic will not be allowed on either direction of SR 18 beneath the I-90 bridges. Depending on direction of travel on I-90, Snoqualmie residents can use exit 22 (Preston), 27 (SE North Bend Way/Snoqualmie Casino), and exit 31 (North Bend) as alternate options to access I-90 during the lane closures.
Eastbound and westbound I-90 traffic will not be affected during the closure, but drivers should be aware that:
- Vehicles will not be permitted on either direction of SR 18 beneath the I-90 bridges.
- Traffic on the eastbound I-90 off-ramp will only be able to turn south onto westbound SR 18. No left turns onto eastbound SR 18/Snoqualmie Parkway will be allowed.
- Traffic on the westbound I-90 off-ramp will only be able to turn north onto Snoqualmie Parkway or continue onto the westbound I-90 on-ramp. No left turns onto westbound SR 18 will be allowed.
- Eastbound SR 18 traffic must use the eastbound I-90 on-ramp and follow a detour.
- Southbound traffic on Snoqualmie Parkway must use the westbound I-90 on-ramp and follow a detour.
According to WSDOT, the extended closure will eliminate the need for 10 consecutive nights of ramp and intersection closures near the interchange and fewer traffic shifts, which improves safety for workers and people driving through the work zone. It also reduces the chances that opening the new interchange is delayed.
During the closure, contractor crews working for WSDOT will install new drainage and electrical crossings, pave the new roadway and build concrete islands that will form a portion of the new I-90/SR 18 diverging diamond interchange. The work also includes constructing a left turn pocket for traffic turning from westbound SR 18 onto Southeast 104th Street and a signalized U-turn south of I-90 that will allow eastbound SR 18 traffic to head westbound toward Auburn.
The extended closure will allow both the left turn pocket from westbound SR 18 to Southeast 104th Street and the signalized U-turn to westbound SR 18 to open while work on the rest of the interchange is completed.
Post Closure
When SR 18 reopens Wednesday, May 21, most of the construction on the southern end of the new interchange will be complete. Work remains under the I-90 bridges and on the northern end of the project before traffic can be shifted into the final diverging diamond configuration later this summer.
In addition to building the new interchange, the project is:
- Widening more than 2 miles of SR 18 south of I-90 to two lanes in each direction.
- Building new four-lane bridges over Lake and Deep creeks that will allow fish and wildlife to pass beneath SR 18.
- Constructing a new two-lane bridge over Raging River next to the existing SR 18 bridge.
SR 18 widening is expected to finish later this year.
