Regional road work this weekend, including a full closure on I-405

Sep 12, 2025, 3:53 PM | Updated: 3:54 pm

I-405 northbound from South 3rd Street in Renton. (Photo: @SounderBruce via Flickr Creative Commons)

(Photo: @SounderBruce via Flickr Creative Commons)

KIRO Newsradio Traffic Reporter

Those traveling through western Washington this weekend will want to plan ahead, as multiple road projects are underway.

I-405 in Renton

A full closure on southbound I-405 is scheduled throughout the entire weekend between Coal Creek Parkway and State Route 900 (SR 900)/Sunset Boulevard. The 4.5-mile closure is needed for the Washington State Department of Transportation (WSDOT) to tackle a number of projects before the fall rainy season arrives.

Crews will be excavating drainage crossings, installing ramp metering and lighting, repaving, and completing a traffic switch as the next phase moves forward with the I-405/Bellevue to Renton Widening and Express Toll Lanes Project.

This closure begins Friday, September 12, at 11:30 p.m. through 4 a.m., Monday, September 15. A detour will send drivers to Coal Creek Parkway, which isn’t designed to handle freeway volumes. Drivers may want to consider crossing Lake Washington and traveling southbound on I-5.

I-90 in Issaquah

Beginning Friday, September 12, at 8 p.m., WSDOT will reduce westbound I-90 to a single lane between Sunset Way and Front Street. Bridge repairs on two separate bridges will last through 8 a.m., Sunday, September 14. During this time, drivers will see significant backups approaching this 1-mile stretch of lane reductions, especially during peak hours.

I-90 by Lake Washington

Beginning Friday, September 12, at 10 p.m., all eastbound lanes of I-90 will close between Seattle and Mercer Island. This includes the southbound I-5 on-ramp, northbound and southbound Rainier Avenue South on-ramps, and the eastbound I-90 off-ramp to West Mercer Way.

WSDOT crews will conduct regular tunnel maintenance overnight with all lanes reopened by 6 a.m., Saturday, September 13. WSDOT will switch this closure to the westbound direction of I-90 next weekend for similar tunnel maintenance.

I-5 in Lacey

WSDOT will have two nights of lane closures northbound on I-5 between Carpenter Road and Marvin Road. Friday, September 12, two right lanes will close at 10 p.m. through 5 a.m., Saturday.

The same lane closures will take place again Saturday, September 13, at 10 p.m. through 10 a.m., Sunday.

Drivers will notice a period when there is no activity while the lanes are closed while the concrete is curing. Drivers can expect heavy delays at times as only one lane will be open during work hours.

State Route 16 in Port Orchard

A major shift is ahead at the State Route 16 (SR 16) westbound/Sedgwick Road on-ramp, part of the Blackjack Creek Project. On Monday, September 15, traffic will shift to the new bridge at the on-ramp. Beforehand, WSDOT needs to close the Sedgwick Road on-ramp to complete the new roadway.

The closure begins Friday, September 12, at 6 p.m. and is scheduled to reopen by 5 a.m., Monday, with the new bridge shift. This work was originally scheduled for August and was postponed due to rain.

Nate Connors is a traffic reporter for KIRO Newsradio. Follow him on X. Read more of his stories here. Submit news tips here.

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