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.
Immediately after the 2001 Nisqually earthquake, we made repairs to keep the Alaskan Way Viaduct safe and functional, and began regular inspections to closely monitor cracks, structural movement and foundation integrity. Visit our viaduct inspections page for a summary of inspections since 2001.