Road crews will take advantage of favorable September weather conditions to complete multiple infrastructure projects across King County this weekend, creating significant closures on Interstate 5, Interstate 405, Interstate 90, and State Route 18.
The extensive closures affect Auburn, Kent, Renton, and Issaquah from Friday night, September 26, through Monday morning, September 29. All projects depend on weather conditions and may be postponed if rain threatens work zones.
Washington State Department of Transportation officials warn drivers to plan alternative routes and expect increased congestion on remaining open highways during the closure period.
Interstate 5 Southbound Through Kent
The most extensive closure affects southbound I-5 from State Route 516/Kent Des Moines Road to South 272nd Street, shutting down completely from 11:59 p.m. Friday through 4 a.m. Monday. The southbound SR 509 expressway will simultaneously close between 24th Avenue South and I-5.
Crews will replace 60 concrete panels and perform additional pavement repairs during the 52-hour closure window. Regional traffic can use southbound SR 167, while local drivers should utilize SR 99 or Military Road South as alternatives.
Interstate 405 Southbound Through Renton
Southbound I-405 closes from Northeast Sunset Boulevard to SR 167 during the same timeframe as the I-5 closure. Construction crews will install drainage crossings, complete paving work, and shift traffic lanes to accommodate ongoing corridor improvements.
A signed detour route via Northeast Sunset Boulevard will direct traffic around the closure. This project faces potential postponement if weather conditions deteriorate.
Interstate 90 Westbound Through Issaquah
Bridge repair work will reduce westbound I-90 to one lane near Front Street from 7 p.m. Friday through 8 a.m. Sunday. The Front Street on-ramp to westbound I-90 will close simultaneously, forcing drivers to use alternative access points.
The abbreviated timeline compared to other projects reflects the critical nature of maintaining some capacity on this major east-west corridor connecting Seattle to the Eastside.
State Route 18 Westbound in Auburn
SR 18 faces a two-phase closure schedule. One lane remains open from 9 p.m. Friday through 1 a.m. Sunday, with the Auburn Way South on-ramp closed. A signed detour guides drivers to the Third Street Southwest on-ramp.
Complete westbound closure follows from 2 a.m. Sunday through 5 a.m. Monday, requiring all traffic to exit at Auburn Way South and re-enter the highway. Police officers will direct traffic through the intersection during the total closure.
The coordinated closure schedule reflects WSDOT’s strategy to maximize construction productivity while minimizing long-term traffic disruption. September’s typically dry weather provides optimal conditions for concrete work and paving operations.
Drivers can monitor real-time conditions and closures through WSDOT’s travel center map at wsdot.com/travel/real-time/map. Officials recommend checking conditions before departure and allowing extra travel time throughout the weekend.
