SEATTLE – It’s been five years since the magnitude-6.8 Nisqually Earthquake jolted the Alaskan Way Viaduct so hard that officials began to realize it wouldn’t last forever.
The state Department of Transportation had been fretting since 1994. But some folks aren’t very happy with what state and city officials have come up with.
“Now … we are offered viaduct solutions that would take up to 10 years to complete,” say two retired engineers writing in a Seattle newspaper.
They contend the towering concrete viaduct could be shored up for as much as another 50 years with a “brace-and-damper” system for $600 million, instead of the $3.7 billion to $4.5 billion tunnel options preferred by Mayor Greg Nickels and state Transportation Secretary Doug McDonald.
“This solution has been ignored by the DOT for the last 18 months on grounds it was presented too late to be considered,” wrote Victor Gray, a civil and structural engineer who worked on seismic strengthening of the state Capitol after a 1965 earthquake, and Neil Twelker, a geotechnical engineer who suggested the method used for construction of the I-90 tunnel under Seattle’s Mount Baker neighborhood.
The two men are sure they have a better idea.
“Well, they don’t,” said bridge engineer Jugesh Kapur with the Transportation Department in Olympia.
Official opinion notwithstanding, the two men got so many responses to their Jan. 26 opinion piece that they’re encouraging anti-tunnel advocates to join their Viaduct Preservation Group.
The 1998 proposal by Gray and Twelker has been evaluated by experts, Kapur said. “They’ve rejected it over and over again. We’ve dealt with it so many times. It’s fatally flawed. It doesn’t work.”
A subsequent proposal made in 2004 suggests an elaborate three-dimensional frame to bolster the structure, he said in an e-mail. That was rejected, too.
“Retrofit schemes have been studied extensively for the past five years, and if there was one that was structurally sound and economically feasible, WSDOT would have adopted one and used it,” Kapur wrote in a Wednesday e-mail.
Gray contends the state didn’t give the 2004 proposal a chance. It calls for bracing each of the bridge’s 64 three-span units – only a couple of which were damaged by the quake – with two transverse bracing systems and two longitudinal ones.
Most retrofits cost almost as much as rebuilding, Kapur said, and as a new structure would be more reliable, “it does not make sense to focus too much on retrofitting.”
He said Gray and Twelker’s proposals focus on seismic deficiencies and do not address the aging structure’s “serious structural deficiencies.”
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