Emergency closure plan

Emergency closure plan

The Alaskan Way Viaduct and adjacent seawall continue to show signs of age and deterioration and are vulnerable in another earthquake. We know this and we are preparing. While not all scenarios can be anticipated, WSDOT and the Seattle Department of Transportation have developed an Emergency Closure Plan that includes basic strategies (pdf 187 kb).

In the event of a sizable earthquake and its aftershocks, drastic actions will be necessary to respond and restore services. Our immediate priorities will be the protection of lives and speedy restoration of our transportation system.

Priority will be given to moving emergency response personnel through the city. Traffic will be redirected away from downtown Seattle. Key bridges and structures will be inspected. Temporary detours will be put in place and emergency public information systems will be activated. In the days and weeks after an earthquake, the real difference will be made by Seattle travelers' decisions to change routes, limit travel and alter travel modes. This will determine how well people and goods move during a closure.

Automated viaduct closure system

We installed a system designed to close the viaduct automatically in the event of a moderate to severe earthquake in the greater Seattle area. The new automated closure system consists of traffic gates at all viaduct access points controlled by an earthquake detection system. When the earthquake monitoring system detects significant ground movement, it will simultaneously lower all nine traffic gates and safely close the viaduct in two minutes.

This system will be in operation until we build the replacement for the viaduct, and demolish the existing structure.

Semiannual inspection results

Immediately after the 2001 Nisqually earthquake, we made repairs to keep the Alaskan Way Viaduct safe and functional, and began semiannual inspections to closely monitor cracks, structural movement and foundation integrity.

The viaduct's south end was demolished in fall 2011, but the downtown waterfront section is scheduled to remain open to traffic until the SR 99 tunnel opens in late 2015.

Below is a summary of inspections since 2001. Learn more about WSDOT's bridge safety efforts.

 

Inspection date Results / actions
March 2014 Survey crews found new cracks and expansion of existing cracks on columns and girders near Seneca Street; additional monitoring equipment was installed in the area. Minor settlement along the alignment ranged from zero to 1/8 inch. Approximately 1/16 to 1/8 inch of settlement was noted in the columns from South Washington to Seneca streets.
October 2013 Survey crews note some additional minor settlement near Seneca Street (about 1/8 inch) along with widening of existing cracks. Crews also note some additional minor settlement near Yesler Way and at Columbia Street (about 1/16 – 1/8 inch each). No new structural damage was found.
March 2013 No new structural damage and no change in the inspected cracks. Survey crews note some minor settlement (between 1/8 to 1/4 of an inch) along several columns between South Railroad Way and South Washington Street. The settlement qualifies as inconsequential and does not affect the operational safety of the structure.
October 2012 Survey crews note some minor settlement near Yesler Way (about 3/16 of an inch). New cracking was also identified near the Seneca Street off-ramp.
March 2012 Survey crews note some minor settlement near Seneca Street (about 7/16 of an inch) and Yesler Way (about 3/16 of an inch). New cracking was also identified near the Seneca Street off-ramp. Crews found no new structural damage.
January 2012 No new structural damage and no change in the inspected cracks. Survey crews note some minor settlement (about 1/16 of an inch) at a column between Yesler Way and Columbia Street, bringing the total amount of settlement in this area to approximately 1 and 10/16 inches.
October 2011     No new structural damage and no change in the inspected cracks. Survey crews note some minor settlement (about 3/16 of an inch) near Columbia Street.
March 2011 Survey data reveals no new settlement or structural damage.
January 2011 No new structural damage and no change in the inspected cracks. Survey crews note some minor settlement (about 1/16 of an inch) at a column between Yesler Way and Columbia Street, bringing the total amount of settlement in this area to approximately 1 and 9/16 inches.
October 2010 No new structural damage and no change in the inspected cracks. Survey crews note some minor settlement (about 1/2 of an inch) at a column near Columbia Street, bringing the total amount of settlement in this area to approximately 1 and 7/16 inches.
July 2010 No new structural damage and no change in the inspected cracks. Survey crews note some minor settlement (about 1/8 of an inch) at a column between Yesler Way and South Washington Street, bringing the total amount of settlement in this area to approximately 5/8 inches.
March 2010 Inspection crews find no new settlement or structural damage.
January 2010 No new structural damage and no change in the inspected cracks, but survey crews note some gradual and minor settlement (less than 1/8 of an inch) at a column near South Washington Street.
October 2009 Crews find no additional settlement and no new structural damage.
June 2009 Crews detect no additional settlement 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. 
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.
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 ¼ 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 South 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 South 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 South 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 South Washington Street.
February-April 2001 WSDOT makes $3.5 million in post-Nisqually earthquake repairs.

 

As we prepare for emergencies, crews also ensure the viaduct remains safe for daily use. This work includes semiannual inspections to check for structural damage.

As we prepare for emergencies, crews also ensure the viaduct remains safe for daily use. This work includes semiannual inspections to check for structural damage.