Since it first opened in 1953, the AWV has been one of the main north-south highway corridors through Seattle, and until its recent closure was carrying an average of 100,000 vehicles per day.
In addition to cutting off the city from its scenic waterfront, decades of daily wear and tear had exacted a heavy toll on the aging structure. The powerful Nisqually Earthquake caused extensive damage to the viaduct’s foundation, causing its closure for several months and highlighting the structure’s seismic vulnerability.
Shortly after the earthquake, WSDOT launched efforts to identify and implement the best solution to address this critical public safety and mobility liability, recognizing that it also provided the city with an opportunity to restore access between downtown and the waterfront and revitalize the waterfront area.
The tunnel was designed to meet stringent seismic standards to withstand a 2,500-year earthquake and features smart transit technology, including more than 300 cameras that monitor traffic, safety conditions and security.
“By its nature, moving transportation corridors underground frees up a lot of valuable surface land,” Mike Colyn, WSP’s project manager for Waterfront Seattle. “The AWV Program’s completion provides nine acres of new open space adjacent to the downtown Seattle waterfront and gives the waterfront back to the public.”
Waterfront Seattle is a $688 million program anticipated to reinvigorate the waterfront as an inviting, lively and family-friendly public space, connecting residents and visitors with cultural, commercial and civic destinations, and fostering growth and development opportunities for area businesses and nearby neighborhoods.
WSP is also part of the team helping to deliver this new amenity. As a subconsultant to the City of Seattle, WSP is leading the engineering component of the project and has provided 3D design visualization, cost risk assessment, project management, civil engineering, traffic engineering, stormwater management, storm drainage, electrical duct banks, risk management, and structural design support.