Cracks are growing on the Alaskan Way Viaduct, which will need a few brief closures for inspections and repairs near Seneca Street.
Some cracks are new and others have increased since they were found last year. The problem is unrelated to construction of a four-lane tunnel, because that work is happening a half-mile south, says Tom Baker, chief bridge engineer for the Washington State Department of Transportation (WSDOT).
Instead, the most likely culprit is the 2001 Nisqually earthquake, which probably caused the column foundations to shift in ways that arent entirely understood, he said. Baker mentioned that technical records for the 1953-vintage structure are incomplete.
But the WSDOT has noted the viaduct has sunk more than 3 inches near Seneca Street since the quake, including continued sagging last year.