From Seattle Deptartment of Transportation:
The West Seattle high-rise Bridge is closing Monday, March 23 at 7 p.m. until further notice to keep the traveling public safe due to concrete cracking.
Buses, freight and emergency vehicles will be diverted from the Spokane Street Viaduct to surface streets in West Seattle and SODO to connect with the Spokane Street Bridge, also called the low bridge. Access to Terminals 5 and 18 via the low bridge will remain unchanged.
Personal cars will not be able to use the “low bridge” and motorists should use the First Avenue and South Park bridges.
Read the SDOT's full press release.