April 25, 2008

Seattle project team copes with settling of Viaduct

Seattle

Work to reinforce part of Seattle’s Alaskan Way Viaduct may have contributed to the latest settling of the structure, but officials think that once the project is done, the settling will stop, according to a recent report in the Seattle Post-Intelligencer.

A crew from contractor C.A. Carey Corp. have finished pouring concrete around the base of a support column below the west edge of the viaduct at Yesler Way, the last of four to be shored up in a US$3 million contract.

By May 3, the area will be relandscaped and blocked-off parking spaces restored, completing an initial step toward removing or replacing the viaduct.

The span has settled into the soil 5 1/2 inches in the Pioneer Square area since the 2001 Nisqually Quake; some settling has occurred since the construction work began. The next inspection of the viaduct for settlement and other damage is scheduled for June. Crews reinforced the structure by drilling six-inch pipes into the ground using water to push them in. Three-inch reinforcing piles then were driven into the casing as far as the bedrock layer and connected to the old foundations.

Viaduct project manager Ron Paananen confirmed that the latest round of settling at the location was detected after the work was done on three of the four columns. He said that occurred because the bridge and the new components compressed, pushing down on the new piling. The injection of water, he said, also may have contributed partly.

The work, once done, should stop the settling, though the inspection could show additional settling of up to one-eighth of an inch, Paananen said. Asked if the work ultimately will stop the settling, he said, “it should.”

Following the project, however, the state will continue restricting heavy truck and bus traffic.

DCN News Services

Print | Email | Comment