Plan on leaving you Eastside home this week? Better think twice...

File photo/KCPQ-TV

SEATTLE -- Beginning tonight at 9:30 p.m., the Department of Transportation will begin a massive construction project on westbound Interstate 90 that will funnel traffic down to just one lane for an entire week and cause massive backups.

The section of the I-90 bridge that will be affected will be in the westbound lanes between Bellevue and the east side of Mercer Island. Construction crews must remove large, heavy expansion joints embedded in the concrete and replace them with new ones. The old expansion joints are over three decades old and beyond repair.

85,000 vehicles take WB I-90 everyday and WSDOT hopes half of those motorists will avoid the popular freeway. Alternates routes around the construction will likely also be impacted on 520 and 405.

Motorists we spoke with are not looking forward to this project.

Peter Wong takes I-90 almost every day. During the week of construction he won't.

“It’s bad enough now if I hit rush hour traffic it’s going to take 20 minutes, 30 minutes to cross that bridge," he said. "With three lanes down to one lane that’s going to take an hour and a half.”

Tolls on the 520 bridge will still be collected and traffic will likely be backed up on that popular bridge as well. WSDOT says the morning and evening commutes will be lengthy as a result.

For more on the construction project and how to avoid it, click here.