I-405 and Highway 522 toll-lane roadwork will clog Eastside this weekend

Traffic Lab is a Seattle Times project that digs into the region’s transportation issues to explore the policies and politics that determine how we get around and how billions of dollars in public money are spent.

Two lanes of southbound I-405 in Bellevue, along with its entry and exit ramps at Southeast Eighth Street, will close all weekend for paving.

At about the same time, one lane of westbound Highway 522 in Bothell, and all the eastbound lanes, will close, too, for work at the massive Sammamish River/I-405 interchange.

The I-405 job is scheduled from 11 p.m. Friday, April 19, until 5 a.m. Monday, April 22. It’s part of the Washington State Department of Transportation’s broader $750 million widening project to build express toll lanes for the south half of I-405 between Bellevue and Renton, opening in 2025.

This weekend’s construction area roughly extends from downtown Bellevue to the I-90 junction.

The lanes will “taper back open” with enough room for southbound I-405 drivers to use the right-side ramps for both west- and eastbound directions of I-90, according to Craig Smiley, a project spokesperson.

The high-occupancy lane of southbound I-405 will be open to all drivers. Detour routes will be marked for roads around the Southeast Eighth interchange.

Up north in Bothell, the Highway 522 lane closures go from 10 p.m. Friday, April 19, until 4 a.m. Monday, April 22.

If drivers do insist on going east into Woodinville, they’ll be detoured south into I-405, then exit at Northeast 160th Street, with the opportunity to backtrack on northbound I-405 until they rejoin 522 east of the interchange.

A second express toll lane each way is being added in that area, to loosen traffic bottlenecks where the freeway has only three total lanes in Bothell.

Crews will shift westbound Highway 522 lanes into the eastbound side, creating space for contractors to renovate I-405 and connecting ramps, through 2028. The 522 mainline below I-405 will be permanently reduced to 35 mph, and eventually, three traffic lights will be installed, Smiley said.

Lane closures on the Eastside coincide with roadwork west of Lake Washington, where northbound I-5 in Seattle will undergo a three-lane closure this weekend next to Boeing Field.

Slowdowns in Bellevue and Seattle could affect how people get to the Sounders FC soccer match at 7:30 p.m. Saturday or a Reign FC match at 3 p.m. Sunday. Allow extra time for trips through the paving zones.