Both directions of the State Route 99 tunnel in Seattle will close for scheduled maintenance beginning at 10 p.m. Friday, Sept. 8, until 6 a.m. Saturday, Sept. 9.
The tunnel closure will allow the Washington State Department of Transportation to conduct a number of important tasks, including:
The Bridge Preservation Office will perform structural inspections of the extraction duct and roadway.
Signals and electrician crews will conduct lighting circuit repair.
Crews also will calibrate the haze detector and conduct maintenance air fan filter rack modifications.
People traveling through the area Friday night should use alternate routes.