From the Washington State Department of Transportation:
WSDOT has closed the Alaskan Way Viaduct for approximately two weeks beginning April 29 while Bertha, the SR 99 tunneling machine, tunnels beneath the structure. SR 99 will be closed from the south end of the Battery Street Tunnel to Spokane Street.
A website dedicated to the closure – 99closure.org – lists resources and ideas on ways to adjust commutes and work schedules. See map of available truck routes.
Read the news release.