After seven years, a public vote and countless discussions, the Washington State Dept. of Transportation, City of Seattle and King County narrowed the options for replacing the Alaskan Way Viaduct to two: a six-lane boulevard or a reconfigured elevated highway.

Photo: WSDOT

At-grade boulevard would mimic Embarcadero

Photo: WSDOT

Elevated highway would have twin spans

State and local officials are racing against the clock to meet a self-imposed 2009 deadline for selecting a plan to replace the 55-year-old highway, which was damaged in the 2001 Nisqually earthquake. Washington Gov. Christine Gregoire (D) says the current structure is “a literal threat to the safety of the people who are on there” and wants to start tearing it down in 2012. A final decision on the new viaduct design is expected by Dec. 31.

The two plans were chosen out of a group of six additional proposals that included an ambitious design featuring a four-story structure with office and retail space below a two-level elevated highway and topped by a public park. Other possibilities included a cut-and-cover tunnel, bored tunnel and two different boulevards configurations.

Proposals currently under consideration differ more in appearance than in cost or construction timelines.

The street surface option, a six-lane, tree-lined boulevard along the city’s waterfront, resembles the Embarcadero in San Francisco. It carries a price tag of $2.2 billion. But when improvements to Interstate 5, enhancements to mass transit and related projects are factored in, the final cost increases to $3.3 billion. It would take five and a half years to build regardless of whether the viaduct is closed or remains partially open.

The elevated highway option, two independent side-by-side bridges that replace the current double-decker structure, costs $2.3 billion. But after construction costs, traffic mitigation and related projects are added in that figure climbs to $3.5 billion. This alternative could be completed in six and a half years if the viaduct is shut down during construction, but that timeline increases by two years if the highway is kept partially open.

Still unknown is how the projects would be funded. The state legislature has earmarked $2.8 billion for replacing the structure but more than $1 billion has already been spent or is committed to viaduct-related projects that began last spring. State Transportation Secretary Paula Hammond said President-elect Barack Obama’s federal stimulus package is an unlikely source of funding.