After nearly four years of construction cones and detours, Snoqualmie-area drivers finally got a break when the $188 million I-90/SR 18 interchange overhaul wrapped up ahead of schedule. Following a weekend of final paving, SR 18 under I-90 reopened Sunday morning, about 20 hours earlier than planned. With traffic now flowing through the finished layout, the notorious junction that long plagued Eastside commuters and freight haulers has been completely reconfigured.
WSDOT had planned a full closure of SR 18 beneath the I-90 bridges from July 9 to 13 to handle the last round of paving and tie-ins, according to a news release from WSDOT. The agency billed the weekend as the final extended shutdown needed to finish the new diverging diamond interchange and related lane work while keeping I-90 traffic moving overhead.
What changed at the interchange
The project delivers a full diverging diamond interchange and widens more than two miles of SR 18 to two lanes in each direction, plus a traffic signal controlled U-turn just west of the junction. Crews also built a new two-lane bridge over the Raging River and two four-lane bridges at Deep Creek and Lake Creek, and replaced fish-passage barriers with relocated open-channel streams, according to KIRO 7.
Why it matters for drivers
WSDOT says the wider SR 18 and the diverging diamond remove a long-standing pinch point that caused congestion at the I-90/SR 18 interchange and should reduce backups and crashes, improving daily commutes and freight reliability, according to WSDOT. A new permanent center barrier between eastbound and westbound SR 18 and the added lanes are intended to give drivers more room to merge safely after they exit the interchange.
What to expect next
Even with the main tie-ins complete and SR 18 fully open, residents can still expect occasional short lane reductions and brief work zones while crews finish details like permanent striping, guardrail and landscaping, Living Snoqualmie reports. Drivers headed through the corridor can continue to check WSDOT's travel map and mobile app for real-time conditions.
Environment and wildlife
The project also included stream relocations and open-channel restoration work intended to restore fish passage and reconnect habitat for local wildlife. Those environmental upgrades are designed to support salmon migration and improve connectivity for deer and elk moving through the Snoqualmie Valley, as reported by KIRO 7.
