Delaying decision could cost millions, viaduct panel told

If the state can't decide by the end of the next legislative session whether to replace the Alaskan Way Viaduct with a tunnel or another elevated structure, it could cost $60 million more to carry forward both replacement options, according to the state Department of Transportation (DOT).

The added cost, which would pay for engineering work needed for both options, was outlined by David Dye, urban-corridors administrator for the DOT, to a panel of experts appointed to study the viaduct and a Highway 520 replacement bridge.

Tuesday was the panel's first meeting. State officials say the panel's work could cost as much as $1 million.

The eight-member panel was briefed by Dye; viaduct project manager Ron Paananen; and Bob Chandler, with the city of Seattle's Transportation Department. It is to write a report by Sept. 1 looking at the viaduct and 520, the two largest highway projects in state history.

For the viaduct, the panel is being asked to answer such questions as:

• Is there a clear process outlined for timely selection of a preferred alternative? And are the necessary technical and financial data available to make a decision on the alternative?

• Was the process used to develop the alternatives reasonable and technically sound?

• Are the project finances sound?

The state hopes in the next year to choose its preferred alternative for replacing the viaduct. Construction would begin in 2010.

Replacing the viaduct with a tunnel is expected to cost from $3 billion to $3.6 billion. Rebuilding the viaduct as an elevated structure would cost between $2 billion and $2.4 billion. The state has enough money available to replace the viaduct but not to build a tunnel.

Some of the most contentious issues about the viaduct decision were outlined for the panel by city and state officials:

• How much time would the entire viaduct be shut down? The longer the viaduct is closed, the less time it would take to rebuild it.

• What would happen to waterfront businesses cut off during construction? What would happen to traffic? The city said it is working on 130 strategies for managing traffic during viaduct construction.

• What happens if the project is delayed? Paananen told the panel that if work can't start in 2008, the delay will cost $10 million a month.

• What would a new elevated viaduct look like? Paananen said the state is working on eight designs and hopes to choose one by the end of the summer. Some would rebuild the viaduct on the same basic footprint as the existing viaduct, but the new structure would be wider. But the state also is designing a so-called "signature bridge" that would be far higher than the existing viaduct. This new bridge would be supported by huge columns rising 200 feet.

The advantage of this option, said Paananen, is that it could be built without shutting down the existing viaduct for long periods of time. "But it may price itself out of contention," he said.

• How would the state deal with environmental mitigation? Officials say this is a serious issue. They expect that if a tunnel is built there would be 2 million yards of fill excavated and that 70 percent of it would be contaminated and need to be sent to a treatment facility.

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