Alaskan Way Viaduct Replacement Program News

March 29, 2018

Crews install the tunnel’s last northbound roadway panel

Earlier this month, Seattle Tunnel Partners installed the last of the 1,152 road panels that together form the tunnel’s lower (northbound) roadway. A double-deck highway now runs nearly two miles end to end inside the tunnel. Our new video shows a special crane lifting the final panel into place.

New video shows “smart” systems in SR 99 tunnel

Seattle Tunnel Partners is now installing and testing the tunnel’s operational and safety systems. Inside the tunnel there will be more than 300 cameras to monitor traffic and security at all times, automatic ventilation systems designed to keep air quality and visibility high, and automated sprinkler systems designed to put out a fire quickly. Together, these new systems will make the SR 99 tunnel one of the “smartest” tunnels ever built. This new video explains how the critical air quality and fire safety systems work together.

Thousands of components that make up the tunnel’s safety and operational systems will be tested at least three times. After the systems are verified, STP will hand the tunnel over to the Washington State Department of Transportation so a different contractor can realign SR 99 and build the final ramp connections to and from the tunnel. Stay tuned to our website for more updates as work progresses.

Sign up for our viaduct demolition email list

If you would like to receive updates on viaduct demolition, please send an email to viaduct@wsdot.wa.gov and ask to receive updates on demolition work. We will use this email list in the months ahead to share information about the work.

Regular updates about the program are available on our website and on Twitter by following @BerthaDigsSR99.