Traffic Advisory Eight-day Closure of SR 18 Under I-90 Starts Thursday Night, July 17

The I-90/SR 18 Diverging Diamond Interchange will officially open on July 25, 2025, marking the culmination of nearly a decade of planning and construction efforts. To achieve this milestone, a full closure of SR 18 beneath I-90 is set from 9 pm on July 17 to 5 am on July 25, prompting significant delays and mandatory detours for drivers. Eastbound and westbound I-90 traffic will largely proceed without interruption, though access to SR 18 will be restricted. Travelers should plan ahead to avoid congestion on detour routes via nearby interchanges. The new diverging diamond pattern aims to enhance traffic flow and safety by lowering potential collision points in the interchange from 26 to 14.

Additionally, the project includes widening over two miles of SR 18 and improving fish passage, with completion anticipated in the fall. Crews will also need dry weather for some tasks, which may result in rescheduling if rain occurs. This project represents a significant investment in local infrastructure, aiming to alleviate traffic issues for Snoqualmie drivers.