SEATTLE — The Washington State Department of Transportation (WSDOT) has awarded a contract for the installation of a system designed to automatically close the Alaskan Way Viaduct within two minutes of an earthquake.

WSDOT awarded Signal Electric Inc. the construction contract for the SR 99 Automated Viaduct Closure Gates System project. Signal Electric, based in Kent, submitted the low bid of $1,434,794. The bid was 27.3 percent below WSDOT’s estimate of more than $1.97 million.

“We know the viaduct structure is at great risk in the event of an earthquake,” said Transportation Secretary Paula Hammond. “This automated closure system is another way to help keep drivers safe until the structure is replaced.”

The new system will consist of nine traffic gates controlled by a series of underground seismic monitoring devices. The gates will be strategically placed at on-ramps and on SR 99 leading up to the viaduct. Installation will begin next month.

WSDOT and the Seattle Department of Transportation’s current emergency process for closing the viaduct can take up to two hours and requires the help of multiple emergency response teams.

Ron Paananen, WSDOT’s Alaskan Way Viaduct and Seawall Replacement Program administrator, said earthquake sensors will monitor how fast the ground is shaking. The sensors will automatically activate the closure system when a moderate to severe earthquake of 5.0 or greater is detected near or underneath the viaduct.

“This will give emergency responders more time to address other issues instead of setting up traffic barricades at viaduct entrances,” Paananen said.

The traffic gates will look and operate similarly to railroad crossing gates. Once the traffic gates are lowered, the entire viaduct must be inspected by WSDOT bridge inspectors before crews can raise the gates and open the viaduct to drivers.

Traffic management response teams also will be able to lower the traffic gates manually, closing off the viaduct in the event of non-earthquake-related emergencies such as a major fire or a hazardous-material spill.

For more information, please visit the project web page at www.wsdot.wa.gov/projects/sr99/viaductclosuresystem/.

For more information about the Alaskan Way Viaduct and Seawall Replacement Program, please visit  www.alaskanwayviaduct.org/.