(SDOT photos)

With unplanned closures yesterday and today, the West Seattle low bridge’s status is in the spotlight again. We asked SDOT for updates – here are two we’ve just received:

Recent unplanned bridge closures

The recent unplanned closures of the Spokane St Swing Bridge have been due to a damaged sensor in the barrier gate on the western side of the bridge as well as unrelated electrical damage from the recent windstorms.

The motion sensor is one of the safeguards used to verify that the barrier gate is correctly locked into place so that the bridge can be safely opened to vehicles. The sensor appears to have worn out earlier this month leading to multiple short-term disruptions to bridge operations. It took us some time to diagnose the root cause of the problem, but this morning technicians were able to confirm the location of the damaged sensor and replace it.

Meanwhile, there have also been unplanned closures resulting from the storm this past weekend. During the storm, power surges and water seeping into some of the enclosures caused short circuits in the terminal blocks, wiring, and connectors. Maintenance staff have been troubleshooting and repairing this damage as it comes to light, but it is still possible that there could be additional damage which we have not discovered yet.

Update on lift cylinder repairs

Earlier this month, SDOT crews installed a newly repaired hydraulic lift cylinder inside the east pier of the Spokane St Swing Bridge. The work was completed over weekend of February 8-10, and did not require any bridge closures for land travel.

The bridge relies on two lift cylinders (one on each side of the Duwamish Waterway). There is also a third spare lift cylinder which has been used when one of the others is being repaired. SDOT has now finished repairing both of the active lift cylinders.

The pair of 30,000 pound hydraulic lift cylinders are the largest mechanical part in the complex system used to lift and turn the 14-million-pound bridge span so it can be opened for passing ships. Each of the large lift cylinders is connected to a pair of smaller turn cylinders which rotate the bridge (four turn cylinders total).

We are still working on the repairs to the last of these smaller hydraulic turn cylinders which was removed in October 2024. We expect to reinstall this turn cylinder and continue to repair and upgrade other cylinders and electrical components throughout this year.

SDOT also completed a bridge strengthening project in 2022, earthquake safety project in 2024, and upgrades to the bridge control and communications system in 2024. This work was made possible thanks to local funding sources including the 2015 Levy to Move Seattle.