information from WSDOT

Seattle Tunnel Partners (STP) made great progress last year. They finished tunneling, disassembled the tunneling machine and completed the southbound (upper) roadway inside the tunnel. Based on STP’s newest schedule (PDF), the tunnel could open to drivers as soon as this fall. Our goal is to safely open the tunnel to traffic as quickly as possible and begin removing the Alaskan Way Viaduct, but it’s too early to accurately predict a tunnel opening date. Safety and quality remain our top priorities, and will continue to guide all work on the program.

A significant amount of work remains between now and tunnel opening. Crews must complete construction of the roadway within the tunnel, and finish installing many interconnected systems that will be required to operate the tunnel. They also must complete a series of thorough tests and certification by the Seattle Fire Department to ensure the systems are working properly. This includes testing approximately 5,000 individual components and nearly 90 tunnel systems. 

You can monitor the progress of the work on the construction tracking page.

The road to tunnel opening

As STP continues their work, construction of final ramp and highway connections to the tunnel is set to begin. The SR 99 Connections Project will build the final connections between the existing highway and the tunnel. Scarsella Bros., Inc. is the contractor for this work, which will be performed under a $22.6 million contract awarded by WSDOT last month.

Scarsella will break ground soon and continue their work throughout this year. When the tunnel is ready to open, SR 99 through downtown Seattle will be closed to traffic for approximately three weeks. Ramps to and from SR 99 will also be affected during this work. The final connections to the tunnel can only be built after the viaduct has been closed because crews must demolish portions of the current roadway to realign SR 99. When these roadway connections are complete, drivers will begin using the new tunnel.

We recognize that this temporary closure of SR 99 will affect the entire region. We’re also aware that the tunnel is one of many projects under construction in downtown Seattle. We will continue to coordinate construction activities with the City of Seattle, Port of Seattle and King County to minimize disruptions to the public. As we always do during major highway closures, we will coordinate with our partner agencies to spread the word, and help keep people and goods moving while crews complete their work.

After the tunnel opens

After the tunnel opens to drivers, we can begin the challenging task of demolishing the Alaskan Way Viaduct. The demolition contractor will also be responsible for decommissioning the Battery Street Tunnel and reconnecting surface streets across Aurora Avenue North. These three projects were combined under a single design-build contract to shave off approximately one year of cumulative construction time. 

As WSDOT explained this summer, the contractor will determine how the viaduct will be demolished within parameters set in the contract. We plan to select a contractor in late spring, and will share the demolition plan and schedule after the contractor is chosen.