As a self-imposed 2009 deadline nears regarding whether to rebuild or raze the 55-year-old Alaskan Way Viaduct in Seattle, a consensus seemss far off.
In early December, a task force whittled down a list of eight design options to two: a six-lane boulevard or a reconfigured elevated highway. The former option, a six-lane waterfront boulevard resembling San Francisco’s Embarcadero, would cost $2.2 billion. With related Interstate 5 work, mass transit and other projects, that amount increases to $3.3 billion and would take 5.5 years to build. The other option, twin bridges, would cost $2.3 billion. After traffic mitigation and related projects, that figure climbs to $3.5 billion and could be completed in 6.5 years, if the viaduct is partially shut down during construction, and in 8.5 years if the viaduct is not shut down.
An idea to build a four-lane, mile-long bored tunnel was originally discarded because of its $4.5 billion price tag. But an analysis by Arup Inc., commissioned by the Cascadia Center at the Discovery Institute, a Seattle-based public-policy think tank, pegged the cost at no more than $1.7 billion. “This would be a bargain for a tunnel that would serve the region for 100 to 150 years rather than the estimated 50 years of useful life for an elevated structure,” says Bruce Agnew, director of the Cascadia Center.
In a Dec. 8 letter to planners, local engineers with HNTB Corp., Robbins Co., Sauer Corp. and others urged decision makers to reconsider the tunnel option. “There are other opportunities to reduce costs and increase benefits by considering other innovative approaches, such as using a single large-diameter tunnel rather than twin bores,” advised firm executives.
Seattle Mayor Greg Nickels has said in the past that he would oppose an elevated highway. In 2007, Nickels’ office suggested the mayor would refuse to issue construction permits in order to block such a project. He has advocated a bored tunnel.