It’s 8:30 p.m. on a peaceful Seattle summer evening—cars drive along the Alaskan Way Viaduct underneath a sky that is colored pink and orange from the setting sun. Just minutes later the viaduct lies in pieces, smoke from burning fires fills the air and half of the city is without power or communications.
That’s the grim picture painted by a video—released by the Washington State Department of Transportation (WSDOT) in response to a public disclosure request—that simulates what would happen to the Alaskan Way Viaduct and seawall if a seismic event stronger than the 2001 Nisqually earthquake shook the region. (You can view the video here.)
Called “Alaskan Way Viaduct and Seawall Replacement Project: Simulated Collapse of Seawall and Viaduct,” the six-minute video depicts a seismic event similar to the 2001 6.8-magnitude earthquake if the simulated event lasted longer, its epicenter were closer to Seattle or its magnitude were greater.
The simulation was based on the 2007 Seismic Vulnerability Analysis Report that analyzed geotechnical data and information on local and regional seismic behavior. The report concluded that there is a higher chance than previously thought—a one in 10 chance in the next 10 years—of an earthquake occurring that could cause portions of the viaduct and seawall to collapse.
The video, which is set on Spring Street looking north, shows the viaduct and seawall swaying and then collapsing during the seismic event. The breaking of columns is the primary cause of the structure’s failure in the video, while the foundation and weak connections between the beams and columns also attribute to its collapse. As a result of the seismic event, the video suggests that Alaskan Way will sink, waterfront buildings and Colman dock will sustain damage, broken utilities lines will cause fires and half of the city will be without power or communications.
The video's release has created some controversy. Publicola reported today: "[The video] was prepared by engineering firm Parsons Brinkerhoff. PB is the main consultant on the viaduct; as such, it stands to make millions if the project moves forward." The post also tied the video to a backer of Joe Mallahan's mayoral campaign, noting that "one of Mallahan’s advisory board members (and maxed out donors) is Jared Smith, an engineer at Parsons."
Five members of the 30-member Viaduct Stakeholders Group also responded to the video's release today. A press release for the members, which was published on Publicola, said, "We are disturbed that WSDOT did not share this video with us during the stakeholder process, even though it appears that they had paid Parsons Brinkerhoff to prepare it in 2007."
Controversy aside, WSDOT is working to maintain the structure's safety. Last weekend, inspectors performed the biannual viaduct inspection. Visual inspections of the structure are done quarterly to measure substantial cracks and settlement.
In a post about the video on the WSDOT Blog, Ron Paananen writes:
"We are also installing an automated closure system next year that will keep drivers from using the viaduct after an earthquake, fire or other event compromises the structure. The new system will use the latest in monitoring technology, including GPS antennas and wireless equipment, to detect structure and ground movement. New signs and gates at the viaduct’s ramps and entrances will detour traffic away from the structure during an emergency, and advance warning signs will notify drivers in SODO, West Seattle, downtown and north of Seattle about any closures.”
To watch the video or learn more, check out WSDOT's post here.
