Project Description

After nearly seven decades, the Alaskan Way Viaduct in Seattle, which carries State Route 99, was beyond repair and needed to be replaced. The Washington State Department of Transportation (WSDOT) was tasked with finding a solution. Completed in 2019, that solution was the State Route 99 Tunnel. This $3.3 billion project was the result of collaboration between WSDOT, the community, and its partners – leading to the demolition of the old viaduct. The new tunnel is built to withstand up to a 9.0 magnitude event off of the coast of the city and includes fire detection, suppression, and ventilation systems that help to keep all travelers safe. The tunnel now sets the scene for Seattle’s new waterfront, providing travelers with different transportation options and 20 acres of public space. The operations on this project showed how aging roadways can be replaced while causing minimal disruptions to drivers – ensuring that safety and needs of travelers were the highest priority.