Traffic patterns on I-5 to change at least 5 times

The northbound traffic patterns on Interstate 5 are going to shift at least five times as the state blocks freeway lanes for construction this month.

The state Department of Transportation (DOT) released new details Monday about the project, which starts at 10 p.m. Friday and lasts until early Aug. 30.

Workers will resurface a mile of freeway and replace worn-out expansion joints between sections of the road deck, from South Spokane Street to Interstate 90.

The state warns that two or three lanes will be closed at a time, and that backups are likely to extend far beyond Seattle. Some nights between midnight and 4:30 a.m., the freeway could be reduced to just one northbound lane, project engineer Paul Johnson said.

"This is the biggest impact we've ever had on any freeway in the state," Johnson said.

Although the construction zone will start at Spokane Street, lane closures will begin farther south, to allow a gradual transition to a narrower highway. The squeeze could begin as far back as the Michigan Street interchange, said Martin Dedinsky, a DOT traffic engineer.

The Columbian Way onramp, from Beacon Hill to northbound I-5, will be closed during the entire construction period.

The five construction stages are:

Friday night until early Monday: Two left lanes of I-5 will stay open. There will be no entry to northbound I-5 from South Spokane Street, and no exit to eastbound Interstate 90. The exit lane to Dearborn, Madison and James streets will be closed, but the Fourth Avenue South exit will be open.

Monday morning through Aug. 17: Two left lanes will be open, as will the exit lane to Dearborn, Madison and James streets, and to I-90. The Spokane Street onramp will be open.

Aug. 18-19: One right lane will be open, as will the exit lane, which will also bring traffic past downtown back onto I-5. The I-90 and Fourth Avenue South exits will stay open, but the Spokane Street onramp will be closed.

Aug. 20-21: same as Aug. 18-19, except the Spokane Street ramp will reopen.

Aug. 22-30: Only two lanes of through-traffic open, but at the Fourth Avenue exit, the whole freeway reopens. Spokane Street onramp and I-90 offramp and downtown exits open.

Johnson defended the decision to close lanes for 19 consecutive days, rather than spread the project over many more nights and weekends. "We've tried to adhere to the motto, 'Get in, get done, and get out,' " he said.

A hotline for motorists to ask questions or report problems has been started at 206-440-4704. To see maps of the lane closures, go to www.wsdot.wa.gov/Projects/I5/SpokaneStreetBridgeRepair/TrafficEffects.htm

Mike Lindblom: 206-515-5631 or mlindblom@seattletimes.com