The viaduct closes for two weekends a year – generally in the spring and fall – for inspection and maintenance. The project also includes planned temporary closures due to construction activities.
We will close the viaduct for approximately two weeks to allow Bertha, the SR 99 tunneling machine, to tunnel beneath the structure. The start date of the closure will depend on the rate of Bertha’s progress. Visit our #99closure page for information about how you can prepare.
Aside from planned closures, SR 99 will remain open during construction thanks in part to a construction bypass roadway that connects SR 99 in SODO to the viaduct along the waterfront.