WSDOT closes portion of I-405 this weekend to repair ’15-foot-deep sinkhole’

Husky fans pay attention. You will not want to be using Interstate 405 to the Michigan State game this Saturday, because construction is going to close the freeway south of Bellevue.

The Bellevue to Renton corridor is not going to be a good option later this weekend. Contractors need to close 405 in stages to repair the drainage system that runs under the freeway.

Washington State Department of Transportation (WSDOT) project engineer Matt Gill said workers first noticed the problem this spring when a small depression in the freeway showed up near Lake Washington Boulevard, south of Factoria.

A 15-foot-deep sinkhole later appeared in the park and ride next to the freeway. The drainage pipes running under the area had failed. Engineers are concerned that sinkholes could start showing up on 405 so they have to make emergency repairs.

“Water started not making it all the way to Lake Washington and seeping out through those damaged portions,” Gill said.

Workers need to tear up the freeway from west to east to replace the pipes.

This all starts at 11 p.m. Thursday night when southbound 405 will be reduced to two lanes from Coal Creek Parkway to Lake Washington Boulevard, which will also be closed. This configuration will last until 5 p.m. Friday.

WSDOT’s Karl Westby said the entire freeway will then close for 23 hours, from 11 p.m. Friday night to 10 p.m. Saturday. This is where Husky fans could run into trouble. “Northbound and southbound will be closed for the trench,” he said.  “We will have a single lane in each direction. That traffic will be using the ramps to get off, go straight through and get right back on the freeway.”

All traffic, in both directions, will be diverted off the freeway at that Lake Washington Boulevard exit during these 23 hours.

“It is something we have to do in very short order before the weather changes on us,” Westby said. “This was the least impactful way we could get this work done.”

The final stage of this project begins late Saturday night when the northbound exit at Lake Washington Boulevard will close, as contractors finish the repairs on the east side of the freeway.

WSDOT’s Craig Smiley said drivers will need a plan to avoid big backups.

“Help us out,” he said. “If you have discretionary trips, try to reschedule those. Make sure you add extra time if you have someplace important to be. Take mass transit, or really just avoid the area.”

Expect long delays, especially on Saturday, and plan to use Interstate 5 to get around the closures, but be careful on I-5. Expansion joint repair work is back again.