January 5, 2023

SDOT to remove giant cylinder from Spokane Street Swing Bridge

SDOT photo [enlarge]

A pair of hydraulic cylinders are used to lift and turn each of the two spans of the Spokane Street Swing Bridge.

Seattle Department of Transportation engineers plan to remove one of the four massive hydraulic cylinders that open and close the Spokane Street Swing Bridge, then reconfigure the bridge to temporarily operate with the remaining three cylinders.

This plan was developed following the Dec. 23 ice storm that paralyzed much of the western part of the state and led to a power outage that may have contributed to machinery damage on the bridge.

“Our goal is to remove the cylinder within the next week,” wrote SDOT spokesman Ethan Bergerson in an email on late Tuesday. “We are currently working to identify suppliers for all the parts and equipment necessary to move the massive cylinder and to reprogram the control system to operate with one cylinder. Moving the hydraulic cylinder is the most complex aspect of the repair plan, and we will be more confident in the schedule once this has been completed.”

SDOT last week stated the bridge would be closed for at least two weeks.

The damaged cylinder weighs 7.5 tons and is paired with a similar cylinder that lifts and swings the 7,000-ton eastern side of the bridge open for marine traffic.

SDOT said after crews restored power to the bridge following the ice storm, they attempted to open the bridge but the eastern span would only partially rotate before stalling. It was then that crews found fluid leaking from the cylinder had intensified.

“We staff this bridge 24/7 and were closely monitoring this cylinder. We know its current condition is not the same as the manageable issue which existed before the storm,” read an SDOT blog post.

SDOT said it has been preparing for several months to overhaul all four of the hydraulic turning cylinders as part of its overall bridge rehabilitation program. The agency said that work allowed it to develop a repair plan quicker than starting from scratch. It also resulted in crews getting a jump on building and assembling some of the needed equipment to pull the damaged cylinder.

The plan is to remove the damaged cylinder and repair it off site. After the cylinder has been removed, crews will rework the eastern span so that it can temporarily operate on the remaining cylinder. This will require reprogramming the control system. SDOT said opening and closing the bridge will take 10 minutes longer with the single cylinder in operation.

SDOT will again close the bridge over the coming months to reinstall the repaired cylinder, as well as finish other planned projects on the bridge.

SDOT said it also replaced 500 feet of underground high-voltage power cable that was damaged by recent high tides and heavy rain that flooded an underground power conduit. This work was finished in the early hours of Dec. 31.