Work Begins January 31st on the Third Bridge Near Tiger Mountain for the SR18 Widening Project

The Interstate 90/State Route 18 Interchange Improvements project is approaching a major milestone, as work begins Wednesday, Jan. 31, on the last of three bridges needed to widen a 2-mile section of SR 18 just south of I-90.

In addition to beginning work on the new four-lane bridge at Deep Creek, contractor crews working for the Washington State Department of Transportation are making progress installing bridge piers for the new two-lane bridge that will span Raging River and already have completed the new four-lane bridge crossing Lake Creek near the interchange.

Closure information

To protect workers and travelers, WSDOT will close the westbound lane of SR 18 overnight from 9 p.m. to 5 a.m. Monday nights to Friday mornings starting Wednesday, Jan. 31, through the end of March. People should plan for up to 20-minute delays, as a pilot vehicle will alternate, guiding both eastbound and westbound traffic through the single eastbound lane along a 2-mile stretch between Lake Creek and Deep Creek, just east of Tiger Mountain summit. The overnight reduction will not occur on Friday, Saturday, or Sunday nights.

Improving wildlife connectivity

Beneath the highway, WSDOT will help fish move more freely by removing existing pipe culverts that block migration and restoring the natural stream conditions of Deep Creek and Lake Creek. The new bridges also will allow wildlife, including deer and elk, to pass beneath the roadway instead of across it, which helps prevent vehicle-animal crashes.

To prepare for culvert removal at Deep Creek later this year, crews will clear trees over the next two months on the east side of SR 18. The trees will be reused as habitat in the streambed, and mulch for new plantings will be put in after construction finishes in 2025.

Widening SR 18 in stages

When completed in 2025, this project will improve traffic flow and safety for highway users and restore access to 13 miles of stream habitat essential for salmon, steelhead, and other aquatic species.

WSDOT plans to widen the remaining 5 miles of SR 18 between Deep Creek and Issaquah-Hobart Road Southeast when the first project is complete. The second widening project is still in design and includes improvements to wildlife connectivity with 17 bridges and 11 fish passage barriers removed.

Real-time travel information is available from the WSDOT mobile app, the WSDOT real-time Travel Center map or by signing up for WSDOT’s email updates.

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  • i had hoped that the 1+ mile section of highway 18 near i-90 would open early (maybe march?) as part of this project. i asked wa dot and they said no–the project won’t open until the entire thing is finished.

    one + year more stuck in traffic and the serious dangers of stopped vehicles on i-90.

  • Living Snoqualmie