Viaduct Inspections

Viaduct Inspections

We're looking forward to opening the tunnel to traffic and demolishing the Alaskan Way Viaduct. It’s the reason we come to work each day. But until we take down the viaduct, it’s our job to protect the structure and keep it safely open to drivers. 
 
One important way we do that is by thoroughly inspecting the viaduct four times each year. Two of these inspections are done visually by crews in bucket trucks, and don’t require a closure of the viaduct. The other two inspections require a weekend closure of the structure that allows crews to:
 
  • Measure existing cracks and look for new ones
  • Check for structural movement 
  • Evaluate the integrity of the viaduct’s foundations
 
Interpreting settlement data
Results from previous inspections are shown in the table below (visual inspection results are not included). It's important to note that not all settlement is significant. In the case of the viaduct, no single number represents an acceptable level of settlement. Those limits vary along the length of the viaduct based on ground conditions and the condition of the structure. How the ground settles is also important. A structure that settles uniformly is less likely to be damaged than a structure that settles unevenly. 
 
Bottom line: We continually monitor the structure to ensure it's safe for everyday use, and these inspections are an important part of that process. Learn more about WSDOT's bridge safety efforts.
 
Inspection date Results/actions
March 2016
Survey crews measured approximately 5/16 of an inch of settlement near Seneca Street and between 1/8 and 1/4 inch of settlement at the Columbia Street on-ramp. Crews also observed upward movement of up to 1 inch at some locations at the south end of the structure. This upward movement is uniform in nature. No new cracking or structural damage was found. 
October 2015 Survey crews detect between 1/4 and 1/2 inch of additional settlement between University Street and south of Seneca Street since the last inspection. The settlement is uniform in nature. Inspectors also note some additional cracking on columns and girders in the same general area, along with up to 1/2 millimeter widening of a few existing cracks. No additional repair work is necessary. 
March 2015 Survey crews measure 1/8 to 1/4 inch of additional settlement near Seneca Street. Some widening of existing cracks noted. Additionally, crews note two new cracks on columns near Yesler Way. New crack gauges and focused monitoring in these areas. Other crack measurements are stable.
October 2014 Survey crews detect new settlement at two locations: near Seneca Street, and between South Washington Street and Yesler Way. Measurements indicate the structure has settled 1/16 inch at these locations since the previous inspection. Additionally, crews detect lengthening in an existing crack near Seneca Street. The crack does not require repair. No new structural damage is detected.
March 2014 Survey crews detect new settlement between South Washington and Seneca streets. Measurements indicate the structure has settled up to 1/8 inch at this location since the previous inspection. Additionally, crews detect new cracks and expansion of existing cracks near Seneca Street; additional monitoring equipment is installed in the area.  
October 2013 Survey crews detect new settlement at two locations: Seneca Street and the area between Columbia Street and Yesler Way. Measurements indicate the structure has settled 1/8 inch near Seneca and up to 1/8 inch near Columbia/Yesler since the previous inspection. Crews also note the widening of existing cracks near Seneca. No new structural damage is detected.
March 2013 Survey crews detect new settlement near Railroad Way South and South Washington Street. Measurements indicate the structure has settled up to 1/4 inch at this location. 
October 2012 Survey crews detect new settlement near Yesler Way. Measurements indicate the structure has settled 3/16 inch at this location since the previous inspection. New cracking is detected near the Seneca Street off-ramp. Crews detect no new structural damage.
March 2012 Survey crews detect settlement at two locations: Seneca Street and Yesler Way. Measurements indicate the structure has settled 7/16 inch near Seneca and 3/16 inch near Yesler Way. New cracking is detected near the Seneca Street off-ramp. Crews find no new structural damage.
October 2011 Survey crews detect new settlement near Columbia Street. Measurements indicate the structure has settled 3/16 inch at this location since the previous inspection. No new structural damage is detected.
March 2011 Survey crews detect no new settlement or structural damage.
October 2010 Survey crews detect new settlement near Columbia Street. Measurements indicate the structure has settled a half-inch at this location since the previous inspection. No new structural damage is detected.
March 2010 Survey crews detect no new settlement or structural damage.
October 2009 Survey crews detect no new settlement or structural damage.
March 2009 Survey crews detect new settlement near Seneca Street. Measurements indicate the structure has settled 1/4 inch at this location since the previous inspection. No new structural damage is detected.
October 2008 Survey crews detect no new settlement or structural damage.
March 2008 Survey crews detect new settlement between Columbia Street and Yesler Way. Measurements indicate the structure has settled 3/8 inch at this location since the previous inspection. Strengthening work is ongoing at the time of this inspection. No new structural damage is detected.
October 2007 Survey crews detect no new settlement or structural damage. Work begins this month to strengthen four column foundations between Columbia Street and Yesler Way.
March 2007 Survey crews detect no new settlement. However, due to continuing settlement measured during previous inspections, a decision is made to repair the structure between Columbia Street and Yesler Way. No new structural damage is detected.
October 2006 Survey crews detect new settlement between Columbia Street and Yesler Way. Measurements indicate the structure has settled 1/4 inch at this location since the previous inspection. This brings total settlement in this area to 4 3/4 inches since crews began measuring in 2001. No new structural damage is detected.
March 2006 Survey crews detect new settlement between Columbia Street and Yesler Way. Measurements indicate the structure has settled 3/8 inch at this location since the previous inspection. This brings total settlement in this area to 4 1/2 inches since crews began measuring in 2001. No new structural damage is detected.
October 2005 Survey crews detect no new settlement. They note a crack near Columbia Street and Yesler Way has grown by 1/10 inch. In November 2005, WSDOT crews make repairs to prevent the crack from spreading further.
March 2005 Survey crews detect new settlement between Columbia Street and Yesler Way. Measurements indicate the structure has settled 1/4 inch at this location since the previous inspection. No new structural damage is detected.
September 2004 Survey crews detect no new settlement or structural damage.
March 2004 Survey crews detect no new settlement between Columbia Street and Yesler Way. Very minimal settlement is detected near South Washington Street. No new structural damage is detected.
October 2003 Survey crews detect new settlement between Columbia Street and Yesler Way. Measurements indicate the structure has settled up to an additional 1 1/4 inches since the previous inspection. Crews also detect continued minimal settlement near South Washington Street. No new structural damage is detected.
March 2003 Survey crews detect new settlement between Columbia Street and Yesler Way. Measurements indicate the structure has settled up to an additional 2 inches since the previous inspection. Crews also detect continued minimal settlement near South Washington Street. No new structural damage is detected.
November 2002 Survey crews detect new settlement between Columbia Street and Yesler Way. Measurements indicate the structure has settled by as much as 1 1/4 inches at this location. Crews also detect minimal settlement near South Washington Street. No new structural damage is detected.
February-April 2001 WSDOT makes $3.5 million in post-Nisqually Earthquake repairs to the viaduct.