Viaduct cost could rise, says DOT report

Shortages of skilled labor, a poor project-bidding climate and inflation could increase the cost of replacing the Alaskan Way Viaduct, according to a two-page memo prepared by the state Department of Transportation for Gov. Christine Gregoire.

Further, according to the memo, in replacing the Alaskan Way seawall — part of the viaduct-replacement project — "the possibility of encountering hazardous materials ... is high."

Gregoire says she'll decide by the end of the month whether she wants the viaduct replaced with another elevated structure or a tunnel. The document lays out the pros and cons of both replacement options, but it does not support one over the other.

Seattle Mayor Greg Nickels and most of the Seattle City Council want a tunnel. Key state legislators from Seattle support a new aerial structure.

Which way the governor might be leaning is a closely guarded secret.

The DOT report said skilled labor is an issue because there are a number of other major projects in Seattle and across the nation, and it might be difficult to find enough people to do the work.

Inflation has long been an issue. The expert-review panel criticized the state for using a too-low inflation number, after which the state recalculated and raised its cost estimate for the project.

With the cost estimated at $2.8 billion, the elevated structure is a cheaper choice and would cause less disruption during construction; the $4.6 billion tunnel option would open up views of Elliott Bay and reconnect downtown to the waterfront.

Included in the DOT document, released to The Seattle Times after a public-records request:

• For overall performance, both alternatives are equal, but there are concerns about freight traffic with the tunnel option because of the grade where the road would enter the Battery Street Tunnel. It would be a 7 percent grade, the maximum allowed, says the state. The elevated structure would have a 5 percent grade at the Battery Street Tunnel. Further, flammable and hazardous cargo would be banned from the new tunnel, which means 80 to 100 trips a day would be rerouted to Alaskan Way, a fraction of the 4,000 freight trips in the corridor today.

• "City opposition to building the elevated structure is a significant risk." The city has passed an ordinance declaring an elevated viaduct "inconsistent" with use and height regulations and the city's comprehensive plan. The city has said it could inflate the $2.8 billion cost of an elevated viaduct to nearly $5 billion by slowing permits, filing lawsuits and using other tactics to oppose the project.

• The city of Seattle owns major utilities within the right-of-way that must be relocated. Without full cooperation, significant delays are likely.

• Building the elevated option assumes the viaduct would be open during peak periods throughout most of construction, with a four- to six-month closure of the ramps at Elliott and Western avenues and likely a closure of the viaduct for up to three months. For the tunnel, cost estimates assume closure of the viaduct for three to 3-½ years and no through traffic on Alaskan Way for three to five years.

• A longer construction plan could cause fewer traffic disruptions, but it would extend those disruptions over a longer period of time. The shortest construction duration would have the lowest project costs. For any construction approach, "significant traffic mitigation will be required."

Susan Gilmore: 206-464-2054 or sgilmore@seattletimes.com