Viaduct retrofit 'doesn't cut it'

State transportation officials say retrofitting the Alaskan Way Viaduct might indeed make the structure stronger, but the improvements would neither be enough to make much difference in a strong earthquake nor make the viaduct safer for traffic.

"This doesn't cut it," said Washington Transportation Secretary Doug MacDonald.

MacDonald and other officials from the Washington State Department of Transportation last week released the results of an independent review of a proposal to retrofit the existing viaduct.

Rather than building a tunnel or a new viaduct, the retrofit proposal was submitted by Victor Gray, a structural and civil engineer and former engineering partner of former governor and senator Dan Evans. He was joined by an organization called the Viaduct Preservation Group.

Basically Gray's plan is to wrap the existing Alaskan Way Viaduct's columns in steel jackets and attach steel angle braces to the sides and under the elevated roadway.

Gray's plan was submitted originally in late 2004. An altered version of the idea was submitted in June of this year.

The state Department of Transportation paid to have Gray's retrofit plan analyzed by the independent Seattle engineering firm T.Y. Lin International. The independent review determined that Gray's ideas would improve the strength of the viaduct a little bit, but not enough to protect the public in a 500-year earthquake.

If there were a 2,500-year quake, the retrofitted viaduct likely would be damaged beyond repair and could even collapse, the independent analysis stated.

Each column holding up the viaduct has a square concrete base. Each base is supported by a vertical bundle of 12 to 16 pilings driven into the ground. The independent study found that the pilings under the viaduct's columns tend to rock back and forth in an earthquake. Retrofitting could accentuate that rocking motion, the analysis reported. The footings at the base of the columns could shear off too.

A retrofitted viaduct is likely to collapse if the area was hit by the strongest earthquake expected to happen within a 2,500-year period, according to the independent review. The structure's columns are brittle and could crumble if the footings broke free from the piles. Floor beams and joints in the viaduct could fail too, the review states.

MacDonald also criticized Gray's idea to inject grout around the viaduct's pilings to strengthen them. Few specifics were offered about how to control where grout would go, said MacDonald, who pointed out that Gray is a structural engineer, not a geotechnical engineer.

Additionally, much of the ground beneath the viaduct is fill material. In a strong earthquake, such places go through liquefaction, which shakes loose the made of fill grout might not sustain its holding power during an earthquake in a liquefaction zone, MacDonald said.

MacDonald also doubted Gray's estimate that it would cost about $800 million to retrofit the viaduct.

"That understates the cost, we believe," he said.

Another review of the retrofit idea is expected soon from the American Society of Civil Engineers.

MacDonald also discounted an idea to replace the Alaskan Way Viaduct with a suspension bridge that some say could be built offshore and parallel to the waterfront.

"As beautiful as a suspension bridge can be, it would block views," he warned.

MacDonald said the state would consider the bridge option but it comes with environmental concerns about fish and habitat, he said. There are shipping concerns and he described the cost as "seismic."

"It's another idea late at the gate," MacDonald said.

Also last week, Mayor Greg Nickels announced plans of his own regarding the Alaskan Way Viaduct.

He's paying attention to little spots scattered along the waterfront where the shoreline could be naturalized with rocks, plants and small sandy sections. Some of these more natural spaces could even be accessible to pedestrians.

"Moving vehicles is less important than providing spaces for people to enjoy," the mayor said at a waterfront news conference.

He praised Allied Arts, which has been dreaming up ideas for redeveloping the waterfront. Nickels thanked the organization for getting people to think about its opportunities.

"They (Allied Arts) make sure we think about more than bricks and concrete," Nickels said. "They're concerned about the soul of the city."

Nickels said he's been assured there will be enough money available from various sources to build a tunnel along the downtown waterfront.

Tim St. Clair can be reached at tstclair@robinsonnews.com or 932-0300.