Bruce Ramsey/Times editorial columnist
All things considered, the viaduct's still viable
Two retired engineers with long histories here make an argument for saving it. Victor Gray, 75, ran a Seattle engineering consultancy and was responsible for the seismic additions that kept the state Capitol from falling down last February. Neil Twelker, 80, is a geotechnical engineer who devised the method for boring the new I-90 tunnel in Seattle.
Of the viaduct, Twelker says, "Of course we can save it. It isn't that big of a problem." To stop the soil under it from turning to Jell-O in an earthquake, Twelker says it could be solidified with chemicals or compacted with pilings.
Also, shock absorbers could be inserted under the viaduct's columns. A Richmond, Calif., company, Earthquake Protection Systems, offers a system in which the column rests in a saucer; if the ground shakes, the saucer moves but the column doesn't. CEO Victor Zayas says his system is used to protect the roof of the Seahawk Stadium, to protect the Washington Emergency Operations Center at Camp Murray and to retrofit an elevated highway in Turkey. And there are other products.
Twelker and Gray say their solution could be tried on a small section of the viaduct to see if it worked. If it did, the cost would be "peanuts," Gray says, compared with the amount the city and state intend to spend.
The state had its own panel of eminent bridge designers and geotechs, including John Clark, the structural engineer for the West Seattle Bridge. In a report published by T.Y. Lin International, they described the viaduct as unacceptably weak.
To save the viaduct, they say, would require temporarily propping up the entire structure with steel, knocking out the columns and horizontal supports, and recasting them new.
"Everything needs to be replaced except the deck," says Jugesh Kapur, 40, the state's bridge design engineer.
Further, it is not only the bridge that needs to be replaced, says Seattle's project manager for the viaduct, Bob Chandler. It is also the sea wall, most of which dates to 1934. If the sea wall failed, and liquefied soil surged into Elliott Bay, the viaduct could fail with it.
The city dismisses the Twelker and Gray idea of putting shock absorbers under the viaduct's pilings. The soil is too soft, says the city's director of roadway structures, Richard Miller. (Twelker says the soil won't make much difference.)
The city is clearly aiming to replace the viaduct with either a new viaduct or a tunnel — and I'd put my money on a cut-and-cover tunnel — to begin construction in 2005.
A new tunnel would be nice. A new viaduct, with wider lanes and columns firmly anchored, would be nice. But under current thinking, it would not add any new lanes, except under the Regrade. It would likely have three lanes in each direction. It would cost at least a billion state and local dollars. It would probably require the payment of tolls.
Deciding whether to build it is partly a question of science and engineering, partly of money and partly of how people judge risk. According to what we believe about earthquakes, the one that would make today's viaduct inoperable comes once in 210 years. The one that would collapse it and kill people comes once in 350 years. Those odds would be lengthened somewhat by the Twelker and Gray proposal and lengthened somewhat more by what the city and state would do.
How much risk will people accept? People in 105,000 vehicles a day — a quarter of the north-south traffic into Seattle's downtown — enter the viaduct of their own will. Most of them know that if the Big One hits, they might not get out. Yet their exposure — a bit more than two minutes per trip — is tiny when compared with 350 years.
It would be difficult for government to say, assuming it wanted to, that citizens are wiser to take their chances. Government has standards, and the viaduct does not meet them.
Safely retired, Twelker and Gray have a more easygoing attitude toward officialdom. "Construction codes change all the time," Twelker says. Thousands of Seattle structures meet the standards of the 1920s, 1930s and 1940s.
"When the Big One comes," their letter says, "the viaduct, whether old or new, will probably be flattened, and so will most of the structures in the downtown Seattle area."
Meanwhile, Interstate 405 is plugged, and the state says it will take $7 billion to unplug it. The Highway 520 bridge needs to be doubled in width. Interstate 5 is a mess.
Perhaps it is better to concentrate our road building billions on new capacity, patch up the old stuff and live with it a while longer.
Bruce Ramsey's e-mail address is email@example.com.