520 bridge inspection finds small cracks
August 1, 2008 · Updated 12:46 AM
Overall, bridge in good shape
The 520 bridge is in good shape according to Washington State Department of Transportation crews that finished analysis of the 520 bridge annual inspection this week.
“In general the inspection results are positive,” said Archie Allen, WSDOT’s Northwest Region Bridge Maintenance Superintendent. “While we found some minor mechanical issues, we now have a clear sense of what we need to repair before the next storm season.”
Engineers found small cracks in guide roller tracks. The tracks help align gears between the drawspan and pontoons and help ensure a smooth opening of the drawspan.
“If winds are hitting the bridge at 50 mph, we need to be able to open the bridge safely and quickly,” said Allen.
WSDOT crews already have started repairs on these cracks, and will continue to monitor and repair the minor cracks during the routine monthly openings.
The electrical systems were found to be in satisfactory condition, though the inspection team noted that an infrared inspection of the 15 kilo-volt electrical system should be done in the near future. They did not conduct a structural inspection of the pontoons at this time, but will complete this visual inspection before winter. Results of ultrasonic testing of the drawspan trunnion beams showed no cracking.
Built in the 1960s without the benefit of today’s design standards, the Evergreen Point floating bridge is vulnerable to earthquakes and windstorms and needs to be replaced, officials say. The new 520 with a “4 + 2” lane corridor configuration will keep drivers safer, improve travel-time reliability and provide a new lane for transit and high occupancy vehicles, they add.
The new SR 520 floating bridge will support bus rapid transit and the pontoons will be expandable to support future high capacity transit for the region. The new six-lane corridor is scheduled to open in 2016.