State says defective support caused lumber to fly off Tacoma viaduct

Jul 10, 2013

The Washington State Department of Transportation has now figured out what caused construction lumber to fall off the Highway 16 Nalley Valley Viaduct project and smash onto South Tacoma Way on June 29th.

As KPLU reported, the falling lumber barely missed landing on a man on a moped.

WSDOT says the contractor has now determined that the cause was a defective four-by-six wood support beam, which collapsed spilling the construction lumber onto the roadway below.

WSDOT spokeswoman Claudia Bingham-Baker says as a result of the mishap, the contractor is now changing how it stores materials. Instead of putting stuff on wood supports, it will use the bridge’s steel girders.

"So the girders themselves will become the support piers and if the material is too short to span two girders then they are doubling up the four-by-six supports under the materials that they are using up on the bridge," Bigham-Baker told KPLU.

This was just the latest problem the Nalley Valley project has had. Last January, a huge section of the old viaduct collapsed while it was being deconstructed, crushing underground water and gas lines. In 2010, a million-dollar design mistake resulted in an off-ramp being built in the wrong place.