One thing was certain after the 2001 Nisqually Earthquake that rattled Washington state’s Puget Sound region: something had to be done about downtown Seattle’s Alaskan Way Viadact. And soon.
The 1950s-era double-deck structure was already considered to be nearing the end of its useful life before the magnitude 6.8 temblor further weakened its columns and joints. With retrofitting the structure out of the question, replacement scenarios for Viaduct’s main downtown section have been debated ad infinitum over the past decade, with the 1.7-mile deep bore tunnel option finally winning out last year.
Meanwhile, the Washington State Department of Transportation (WSDOT) has kept close watch on both the Viaduct and the region’s seismographs for any sign of movement or structural deterioration.
But now, just months before WSDOT’s deadline for receiving design-build proposals on constructing the $2.8 billion tunnel, Seattle Mayor Mike McGinn appears to be saying, “not so fast.”
McGinn recently commissioned transportation consultant Thom Neff, president of OckhamKonsult, Boston, to assess the tunnel’s risks. The Mayor justified the city-funded study out of concern that downtown property owners would bear the brunt of risks and cost overruns from working in the uncertain soils along Seattle’s downtown waterfront.
Neff’s report, presented in mid-July, says that while soil conditions (e.g., abrasive material, groundwater intrusion, seismic issues) are a potential source of higher-than-expected costs, the project has not progressed far enough to pin down a reliable pricetag.
Members of Seattle’s largely pro-tunnel City Council accused McGinn of trying to sidetrack a project he has long opposed. They fired back with an assessment by the Council-hired consultant, John Newby of CDM, Seattle.
Newby asserted that most of the tunnel’s risks, admittedly formidable, can be effectively mitigated. He added that WSDOT appears to be doing all the right things up to this point, a view shared by state Transportation Secretary Paula Hammond.
That leaves only Seattle Tunnel Partners (Dragados USA and HNTB) and Seattle Tunneling Group (S.A. Healy Co.; FCC Construction, S.A. of Spain; Parsons Transportation Group; and Halcrow Inc.). A fourth contender, VTS JV (Vinci Construction Grand Projects of France; Traylor Bros. Inc. Skanska USA, and Arup) dropped out in March.
Meanwhile, the politicians trade accusations, the consultants trade opinions, and the clock on Seattle’s next earthquake keeps ticking.