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Alaskan Way Viaduct Semiannual Inspection Results

Immediately after the 2001 Nisqually earthquake, WSDOT made repairs to keep the viaduct safe and functional. We also began semiannual inspections to closely monitor cracks, structural movement and foundation integrity.

Below is a summary of all inspections and their findings since 2001.

Visit bridges and structures to learn more about WSDOT's efforts to ensure the safety of bridge structures.
Crews inspect the viaduct
Crews check for structural damage during a semiannual inspection.

Next inspection dates: To be determined.

Inspection date Inspection results / actions
June 2009 Crews detect no additional settlement on the viaduct and find no change in the inspected crack monitors.
March 2009 New settlement near Seneca Street was approximately 1/4 of an inch, bringing total settlement in this area to 1-5/8 inches since the Nisqually earthquake. No structural damage or new cracks were found. Inspection photos are available on Flickr.

In April 2008, four column foundations between Columbia Street and Yesler Way were strengthened after the columns had settled approximately 5-1/2 inches since the 2001 Nisqually earthquake. One year later, the columns are more stable, and no new settlement was detected in this area.

All sprinklers in the Battery Street Tunnel are functioning properly, and only a few heat detection devices need repairs.
January 2009 Crews observe no additional settlement or changes in condition.
October 2008 Crews find no new settlement or structural damage.
June 2008 Inspection results show no new structural damage or additional settlement of the columns between Columbia Street and Yesler Way. An additional 1/8 inch of settlement occurred during the repair work to strengthen the column foundations in that area, but measurements show that this section of the viaduct has now stabilized.
March 2008 The section of the viaduct between Columbia Street and Yesler Way settled another 3/8 of an inch, bringing the total amount of settlement to approximately 5-1/2 inches. Columns continue to settle incrementally in this area, where repairs are nearly complete to strengthen several column foundations. No new structural damage was caused by the additional settlement. View photos of this inspection and the public tour held during inspection weekend.
January 2008 The quarterly inspection reveals that the viaduct settled approximately 1/8 of an inch where foundation strengthening work is taking place between Columbia Street and Yesler Way. No new structural damage was caused by the additional settlement.
October 2007 No additional settlement and no new structural damage are detected for the section of the viaduct between Columbia Street and Yelser Way. Work begins this month to strengthen four column foundations in this area.
June 2007 The viaduct settled an additional ΒΌ of an inch, for a total of approximately five inches, in the area between Columbia Street and Yesler Way.
March 2007 Inspection results indicate no additional settlement. Due to half an inch of settlement at two piers found during the two previous inspections, we move forward with repairs between Columbia Street and Yesler Way.
October 2006 An additional 1/4 of an inch of settlement occurred on the viaduct between Columbia Street and Yesler Way. This area has settled a total of 4-3/4 inches since we began measuring in 2001.
March 2006 The viaduct section between Columbia Street and Yesler Way settled an additional 3/8 of an inch. This area has settled a total of 4-1/2 inches since we began measuring in 2001.
October 2005 No new settlement occurred on the viaduct. A crack that we have been monitoring grew from 4 mm to 7 mm. The crack was on a structure near Columbia and Yesler streets, on a joint in the southbound driving lane. In November 2005 WSDOT crews install a steel column to support the damaged beam and distribute the weight through the column, footing and joint.
March 2005 Two columns across from Colman Dock between Columbia Street and Yesler Way settled 1/4 inches.
September 2004 No measurable settlement.
March 2004 No measurable settlement across from Colman Dock. Very minimal settlement in south sections near Washington Street.
October 2003 The viaduct section across from Colman Dock settled an additional 1-1.2 inches (east and west sides) since March 2003 inspection. Continued minimal settlement in south viaduct sections near Washington Street.
March 2003 Crews discover that the viaduct section across from Colman Dock settled 1/2 inches on the east side and 2 inches on the west side since the last inspection. Measurements show continued minimal settlement in south viaduct sections near Washington Street.
November 2002 Crews discover that the viaduct section across from Colman Dock settled 1/2 inches on the east side and 1.2 inches on the west side. Minimal settlement - fractions of an inch - found in south viaduct sections near Washington Street.
February-April 2001 WSDOT makes $3.5 million in post-Nisqually earthquake repairs.

Additional resources

The U.S. Geological Survey is an excellent source for Washington state earthquake information. It includes maps outlining seismicity, seismic hazard areas and faultlines, as well as detailed earthquake and tsunami histories.

The Pacific Northwest Seismic Network, based out of the University of Washington's Earth and Space Science department, catalogs all the latest local seismic and volcano activity. It also includes helpful information on earthquake hazards as well as preparedness and safety tips. 

Earthquakes Canada is another good source of information for earthquakes in British Columbia and western Washington state.