Viaduct retrofit would cost $2.3B

Retrofitting, rather than replacing, the Alaskan Way Viaduct will cost $2.3 billion, according to a study by the Washington State Department of Transportation.

The numbers, released Tuesday, support a memo that viaduct project manager Ron Paananen sent to the city of Seattle and others Friday. It was in response to a state-funded report by T.Y. Lin International that suggested it was possible to retrofit the aging viaduct, but it would require extensive strengthening of the underground foundations.

The state Department of Transportation has long said it wasn't interested in retrofitting the viaduct but commissioned the study in response to assertions by retired structural engineer Victor Gray that a retrofit made economic sense.

Gray has said the viaduct could be repaired for $800 million.

"Major roadways in Washington are designed to a higher standard that ensures public safety in the event of a very bad earthquake. Gray's retrofit proposal doesn't meet that standard," wrote Paananen. "While T.Y. Lin has developed a plan that will, it doesn't pencil out. It would only have a 25-year life span and would cost 80 percent of the elevated structure alternative. We also would be left with a structure that has no shoulders and narrow lanes."

The cost of a new elevated structure is estimated at $2.8 billion.

The new numbers, released Tuesday, say the cost of a retrofit would be almost as much as a new elevated structure. It said T.Y. Lin has developed a plan that could retrofit the viaduct, but the costs are prohibitive.

"For an earthquake of serious severity, likely to have a one in 10 chance of occurring in the next 50 years, the standard would require that the viaduct, though it might be damaged, would still be usable after repairs," said the new state report. "T.Y. Lin's report outlines what would be necessary to meet this standard, including new bracing and other improvements, and also strengthening the footings and piers located in the weak and earthquake vulnerable soil on which the viaduct rests."

The state estimates it would cost $4.6 billion to replace the viaduct with a tunnel, as Mayor Greg Nickels and the Seattle City Council prefer.

T.Y. Lin in August issued a retrofit report that said Gray's retrofit plan was incomplete. The state asked the company to have another look at it and see what could make a retrofit work. It found the "most egregious remaining vulnerability" of the viaduct is the foundations, and extensive work would be required, including putting a dozen additional pilings at each footing.

In other developments Tuesday, the American Society of Civil Engineers, which reviewed that T.Y. Lin report, found that the retrofit proposal by Victor Gray is not a viable option for the viaduct. "With all of the factors in mind, the committee concluded that the relatively narrow difference in cost between the choice of a retrofit or rebuild weighs heavily in favor or rebuilding," the engineering group wrote in its report.

Gov. Christine Gregoire is scheduled to decide by the end of the year whether the viaduct should be replaced with a tunnel or another elevated structure.

Paananen said the engineering plan produced by T.Y. Lin is very different from Gray's. "When Gray's suggestions were turned into a plan that could be evaluated, the results showed we could not guarantee the viaduct would withstand an earthquake with a one in 10 chance of occurring in the next 50 years," he said.

Gray criticized the latest numbers from Paananen and said an outside consultant, not the DOT, should be calculating the retrofit numbers.

"They can make those numbers say anything they want," Gray said. "We need someone with an objective point of view. We need an independent, unbiased look at this thing."

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