2016 #99closure

Recapping the 2016 #99closure

On April 29, 2016 the Alaskan Way Viaduct temporarily closed as Bertha began her planned journey tunneling underneath the structure. WSDOT closed the viaduct to give crews greater access to monitor the structure for any movement. Had any movement of the soil or the viaduct occurred during tunneling, a closed viaduct would have allowed crews to respond more quickly. Additionally, a planned closure (as opposed to an emergency closure) allowed drivers time to plan ahead.

Any closure of a highway – the viaduct carries approximately 90,000 vehicles and 615 bus trips per day – has a major effect upon both local and regional traffic. WSDOT and its partner agencies conducted extensive outreach leading up to the closure, spreading the word about the #99closure and telling drivers to make a plan. Above all, WSDOT asked for drivers’ patience with their trips, their creativity in making a plan, and their understanding as the project reached an important milestone.
During the closure, WSDOT coordinated multiple times per day with Seattle Department of Transportation (SDOT), King County Metro, Seattle Police Department, Washington State Ferries, the Port of Seattle and other partner agencies. A 24/7 command center monitored tunneling, handled agency coordination, and provided the public and media with traffic and tunneling updates. WSDOT and SDOT changed signal patterns and deployed extra incident response teams as traffic patterns and incidents warranted, while King County Metro plugged in additional buses to maintain routes and King County provided free West Seattle parking for water taxi riders. It was an all-hands-on-deck approach (PDF).
In the end, all the extensive planning conducted by both agencies and the public paid off. Drivers changed their routines and stayed informed; Sound Transit light rail and King County Water Taxi saw record ridership, and the AWV program website’s web traffic nearly tripled. Traffic was congested, but not as congested as many predicted. Meanwhile, STP made good progress tunneling beneath the structure, with crews working 24/7. The carefully-monitored viaduct remained stable, and WSDOT was able to inspect and reopen the viaduct on the night of Sunday, May 8, five days earlier than the closure’s estimated two-week duration.

Archived resources:



View of the closed Alaskan Way Viaduct

The Alaskan Way Viaduct was closed from April 29 to May 8, 2016.


The closed Columbia Street onramp

The closed Columbia Street onramp.