On Monday, December 21 and Tuesday, December 22, we’ll lower all work platforms on the West Seattle High-Rise Bridge to a barge on the waterway. Photo Credit: Tim Durkan. The emergency measures we’ve been working on since the spring were necessary regardless of whether we chose to repair or replace the bridge.
Stabilization sets the stage for upcoming repairs of the West Seattle High-Rise Bridge. The primary components and purpose of the stabilization measures are:
- Installing and stressing the post-tensioning system: Along with carbon fiber wrapping, the external post-tensioning is important because it helps strengthen the bridge and thus mitigate some of the risk of further cracking. Stressing the post-tensioning system reinforces the strength of the bridge’s concrete superstructure.
- Carbon-fiber wrapping: Wrapping sections of the bridge with carbon fiber-reinforced polymer supports the stable and now-strengthened bridge. We installed multiple rounds of carbon-fiber wrap over the course of this first phase of stabilization work.
- Pier 18 bearing release and replacement (check out our video!): Pier 18’s neoprene lateral bearings were compressed and bulging, locking together two critical parts of the bridge that typically are independent of each other. The bearings were creating additional pressure and preventing the bridge from moving as it should. Over the last few weeks, we finished pouring and curing the concrete that will hold the new lateral bearings in place.
This week, we completed the carbon fiber wrapping and prepared to lower the work platforms and platform rigging on both sides of the bridge.
Carbon fiber wrapping helps support the now-stable and strengthened bridge. If you happen to be walking, rolling, scooting, or biking across the Low Bridge and look up, you might be able to see the freshly applied wrap.
We also began preparing to lower the work platforms and platform rigging on both sides of the bridge. These platforms helped us access hard -to-reach parts of the bridge while we did the stabilization work.
On Monday, December 21 and Tuesday, December 22, we’ll lower all work platforms to a barge on the waterway.
This will take place between 7 a.m. to 11 a.m. on both days. During this time, there will be a waterway channel closure, which means that maritime traffic/boats will not be able to pass under the West Seattle Bridge. We have issued a notice to mariners and the Port of Seattle, and we do not expect any disruptions to Low Bridge operations for people walking, biking, or for those who have access to drive across.
When this is complete, height restrictions for passing under the bridge – which have been in place since the work began – will be lifted.
After the work platforms are lowered, work will be substantially complete. In early January, we will be offsite disassembling the platforms.
We’ll also be finishing one last round of painting/coating the post-tensioning brackets. Coating the post-tensioning ends will protect the new system.
The repairs that will ultimately allow us to reopen the bridge in 2022 include additional post-tensioning and carbon-fiber wrapping on the center bridge span, as well as the two “tail spans” on either side of the center span. We’ll install additional instrumentation to effectively monitor the overall health of the bridge and the new strengthening system. We are currently working on the design and permitting processes, as well as the contractor procurement process, for the repair.