Work platforms removed from the West Seattle Bridge
by Ethan Bancroft SDOT
Over the weekend, West Seattle Bridge construction crews removed the final two hanging work platforms that were attached to the bridge for repair access. Removing the work platforms signals repair work is nearing completion as we prepare to reopen the bridge on Sunday, September 18.
The work platforms were lifted into place in January 2022. The platforms gave workers safe access to the underside of the bridge in order to inject epoxy filling into exterior cracks and then apply carbon-fiber wrapping. We completed this work last week, and the work platforms are no longer needed.
All concrete cracks over time, and epoxy crack injections are a common repair practice for bridges and structures throughout the world. When concrete cracks, the steel inside is at risk of corrosion from salt and water. Injecting epoxy protects the steel, getting deep inside of the concrete to fill cracks and fuse concrete back together. In 2022, crews have used more than 240 gallons of epoxy for crack injection.
Once cracks have been sealed, crews wrap carbon-fiber sheets around key sections of the bridge like a cast on a broken bone. The carbon-fiber material is as strong as steel and one-tenth of the weight, preventing the concrete underneath from cracking in the future. Over 100,000 square feet of carbon-fiber wrapping has been added to the bridge during the final phase of repairs.
This video shows crews working on epoxy filling and carbon-fiber wrapping earlier this year. More bridge construction photos and videos are available on YouTube and Flickr.
These repair methods work in combination with the recently completed post-tensioning system, made of nearly 60 miles of steel cables which act as the backbone of the bridge. Together, these three repair methods (epoxy injections, carbon-fiber wrapping, and post-tensioning) dramatically increase the strength of the bridge, preparing it to handle decades of heavy traffic, changes in temperature, and extreme summer and winter weather.
Other remaining work to be completed before the bridge opens includes:
- Restore the pavement on the bridge deck
- Perform safety tests and inspect the repairs
- Install permanent inspection platforms inside the bridge structure
- Remove construction equipment and get the bridge ready for the public