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Viaduct Inspection Reveals Sinking And Cracks

Elaine Thompson
Northbound Alaskan Way Viaduct traffic backs up at a downtown exit in view of Elliott Bay Monday, Dec. 8, 2014, in Seattle.

The Alaskan Way Viaduct in downtown Seattle has continued to sink, according to the most recent inspection. Washington transportation officials say the structure is still safe to drive on and no additional repairs are needed. 

Inspectors found that a section of the viaduct had sunk a quarter-to-a-half inch over the last six months. That’s the most identified in a routine inspection since 2010. But Wash-DOT spokesman Travis Phelps says the Viaduct has been settling evenly, which makes it less of a concern.

“The viaduct is basically made up of a bunch of little bridges,” he said. “If we have an area of the viaduct that is not settling uniformly, it can lean on other portions of the structure and cause some damage there. So that’s something we’re watching.”

Phelps says this sinking has been happening gradually ever since the Nisqually earthquake in 2001, and has nothing to do with the stalled tunnel project. Crews also found a few additional cracks in the concrete supports and slight widening of some old cracks. Still the agency reaffirmed the viaduct remains vulnerable to earthquakes, but safe for everyday use.

Gabriel Spitzer is a former KNKX reporter, producer and host who covered science and health and worked on the show Sound Effect.