Washington State Department of Transportation (WSDOT) bridge engineers have scheduled an additional in-depth inspection of the S.R. 99 Alaskan Way Viaduct on Saturday, March 22.
During the viaduct’s most recent inspection, WSDOT bridge crews observed new cracks, as well as movement and widening of existing cracks, along girders and supports near Spring and Seneca streets. While the viaduct remains safe for travel, WSDOT bridge engineers need a second inspection to gather more information about the cracks before they can make repairs.
“These small cracks are evidence that the 60-year-old bridge continues to deteriorate and will continue to need constant attention to remain open,” said Tom Baker, WSDOT bridge engineer. “We inspect the structure multiple times per year to identify issues, like these cracks, and make repairs.”
This section of the viaduct is more than a half-mile north of the current location of the S.R. 99 tunneling machine. While the cause of these cracks is still to be determined, they are not related to tunneling activity.
No other significant settlement or cracking was found during the latest inspection.
As part of the March 22 inspection, WSDOT crews will install monitoring devices on the viaduct to track the movement and growth of the cracks over time. Engineers will use this data to help identify potential repairs. Crews will begin removing ivy on the viaduct later this week to give WSDOT bridge inspectors the space they need to install the monitoring devices and make any necessary repairs.
Details of the closure will be released prior to March 22.
WSDOT inspects the viaduct four times each year, including two inspections that require full closures. Since the 2001 Nisqually earthquake, repairs have been made to the viaduct to ensure it stays safe for traffic.