Routine safety inspections and maintenance keep the viaduct safe for public use. In 2008, crews strengthened four column footings where the viaduct had settled approximately five-and-a-half inches into the ground since the 2001 Nisqually earthquake. The column safety project limits settlement in this area of the viaduct and prevents further damage to the structure.
We also 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. If the earthquake monitoring system detects significant ground movement, it will simultaneously lower all nine traffic gates and safely close the viaduct in two minutes.
In 2011, crews demolished nearly half of the vulnerable viaduct near Seattle’s port and stadiums. Drivers now use a construction bypass connected to new side-by-side bridges built to current safety standards.