Ailing viaduct inspires loads of ideas
Seattle Times staff reporter
City of Seattle: www.seattle.gov/mayor/issues/viaduct/
State Department of Transportation: www.wsdot.wa.gov/Projects/Viaduct
Seattle Mayor Greg Nickels is holding a public open house to explain the progress in replacing the Alaskan Way Viaduct, 5 to 7 p.m. Thursday, Seattle Aquarium, on Pier 59, 1483 Alaskan Way.
The state Department of Transportation may have narrowed the list of ideas for replacing the Alaskan Way Viaduct to two options: Replace the 2.2-mile bridge, or bury the roadway in a tunnel — the preferred option of the city of Seattle and the state.
But that hasn't stopped an assortment of architects, engineers and others from coming up with their own visions — some fanciful, and others practical.
Some want to build elaborate bridges; another wants to put the viaduct in a box. Still others want to move the tunnel to a different street, repair the existing viaduct or simply tear it down.
While the state has dismissed them all, for various economic and structural reasons, the idea mill keeps grinding.
Here are a few of the 76 ideas that have been floated since the 2001 Nisqually Earthquake that put the state on notice that the aging viaduct needs replacing:
• Repair the existing viaduct. While others have made this suggestion, the most attention has been paid to a proposal by engineers Victor Gray and Neil Twelker, who have designed a plan to fix the viaduct for a fraction of the $3 billion to $4 billion the state estimates the replacement will cost.
The two have proposed bracing the existing viaduct and adding dampers to protect against earthquakes at a cost of about $600 million. They said the bracing would involve steel diagonal tubes and plates connected to existing girders and columns, and would add 30 to 50 years of life to the viaduct.
The state claims a retrofit won't hold up in a major earthquake and is not cost-effective because it would require that the foundation, columns, beams, deck and bridge rail be rebuilt or replaced.Repairing the viaduct would cost at least 80 percent of the rebuild cost, according to the state.
• Replace the viaduct with a tunnel not under Alaskan Way, but under Western Avenue. This proposal came from an architect, attorney and waterfront business owner, who argued that tunneling would have devastating effects on waterfront businesses.
"Reasonable people are saying, is there another alternative that would achieve what the mayor is trying to achieve, eliminate a huge urban-design mistake, while maintaining the capacity," said attorney Elaine Spencer, one of the Western Avenue proponents.
She said the advantage of her proposal is that there are fewer utilities under Western Avenue, and this would be a way to keep Alaskan Way open for most of the construction. "The more one looks at the rebuild or tunnel option, the more very significant adverse impacts they find in the design," Spencer said.>
But the state Department of Transportation said the alignment under Western Avenue isn't consistent with the project's engineering and traffic-safety-design standards and that up to 13 buildings, four of them historic, might need to be removed.
They also said a tunnel along Western would not fix the ailing Alaskan Way seawall, so that would require another contract, increasing costs.
Further, the state contends, the right of way available under Western is narrow: 66 feet, compared with 180 feet on the waterfront.
• Signature bridge. The proposal, which emerged late last year, is for a six-lane, "cable-stay" bridge about twice the height of the viaduct, which would be supported by four towers, each about 50 feet wide and 250 feet high.
This came from DOT engineers who were working on a design proposal for the viaduct replacement but is not an official DOT proposal.
The state said the towers for the bridge would be massive, and at 100 feet off the ground and 130 feet wide, the bridge would shade the waterfront and block views. It would also not address the seawall issue.
• Elliott Bay Bridge. This early idea came from architect Roger Patten, who proposed a six-lane cable-stay bridge that would stretch two miles across Elliott Bay from South Holgate Street to the Battery Street Tunnel.
He said the bridge would cost about $1 billion and would be 200 feet high, with the two anchoring piers 800 feet tall. There he envisions restaurants and viewing towers.
Patten says his proposal would make the waterfront quieter and the piers would create an inner harbor for cruise ships.
The state said Patten's bridge has a center span more than a mile in length, longer than all but one completed suspension bridge in the world.
They said the towers would be massive and building the foundations on which the towers would stand would be like building two 60-story buildings underwater.
The bridge would replace existing housing, businesses, a marina and cruise-ship dock and encroach into port, railroad and other industrial land, said the state, and a separate project would be needed to fix the seawall.
• Box the viaduct. This came from retired engineer David Petrie, who envisions a shoebox with the ends cut out plopped over a six-lane expressway, with dirt and plants on top. On top of the park, 19 feet above the ground, Petrie sees tennis courts, a swimming pool and an amphitheater.
The state said the proposal doesn't provide surface streets for access to the waterfront, cuts off a portion of the waterfront and would require moving the ferry terminal. It also wouldn't fix the seawall and creates a barrier between the waterfront and the rest of the city.
• Bypass tunnel. Instead of rebuilding or tunneling the viaduct, this plan proposes building a tunnel under downtown Seattle, two miles long from Mercer Street to Dearborn Street.
This idea, suggested by DOT engineering consultants, was rejected because of the variable soil types and the fact that the tunnel would be 280 feet deep in some locations.
The state said more than 10 million cubic yards of dirt and material would be produced to build the tunnel, about 20 times the volume of the downtown Seattle transit tunnel.
The state also said this proposal could be extraordinarily expensive, as much as $14 billion.
• No replacement. The People's Waterfront Coalition, a group of planners and environmentalists, has long proposed that the state simply tear down the viaduct and not replace it. The group says that a package of smaller road-improvement projects, coupled with more transit, could be built to keep traffic moving through downtown.
That would restore the shoreline to a more natural condition, the group says. And some members of the Seattle City Council have expressed interest in this argument.
But the state says the 110,000 vehicles that now use the viaduct each day can't be moved to Interstate 5 and surface streets.
The state studied this idea and concluded that if the viaduct were torn down and not replaced, traffic along Alaskan Way would more than quadruple and the number of cars on downtown streets would grow as much as 50 percent.
It also wouldn't deal with replacing the seawall.
Susan Gilmore: 206-464-2054 or email@example.com
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