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Weekly Update: West Seattle Bridge

West Seattle Bridge at sunset. Photo Credit: Madison Linkenmeyer

Every Monday, we’re posting a blog to keep you informed about our progress to stabilize the bridge, our efforts to address traffic and mobility, and other items related to the West Seattle High-Rise Bridge closure.

In this week’s update:

West Seattle High-Rise Bridge Stabilization

Temporary work platforms under the West Seattle High Rise Bridge. Platforms are orange and span the width of the bridge, and are suspended underneath is. Photo is taken looking at the full platform, looking west. The Low Bridge with vehicles can be seen in the lower right corner of the image. It is a rainy day.
Temporary work platforms enable crews to do important stabilization work on the West Seattle High-Rise Bridge, and offer a unique view of the Low Bridge. Photo Credit: SDOT

Mayor Durkan Observes Progress

Mayor Jenny Durkan visited the West Seattle High-Rise Bridge in the wind and rain on Monday, November 9 to inspect progress crews have made to achieve two key engineering milestones necessary to stabilize the bridge for repairs or replacement: the release of bearings at Pier 18 and achieving 100% tension in the external post-tensioning system.  

Mayor Durkan got an up-close look on the deck of the bridge, on the platforms suspended underneath, and inside the giant concrete box girders. She was joined by the two Co-Chairs of her West Seattle Bridge Community Task Force, former Mayor Greg Nickels and Duwamish River Cleanup Coalition Executive Director, Paulina López. While on the bridge, the Co-Chairs shared feedback from the Task Force members about the benefits and tradeoffs of both pathways forward for communities in and around West Seattle.

Read on for updates on our recent work.

Releasing the Bearings at Pier 18

We released the damaged bearings at Pier 18 on the east side of the Duwamish. Pier 18’s neoprene lateral bearings were compressed and bulging, locking together two critical parts of the bridge which are normally independent of each other. This was creating additional pressure and preventing the bridge from moving as it should. You can read our blog post or check out the video below to learn more about the release of Pier 18.

We also continued Pier 18 work by breaking down the concrete that held the bearings in place, preparing them for removal. Once all the concrete is removed, we will install new bearings and pour new concrete surrounding the bearings.

A wire saw shown demolishing the concrete around the Pier 18 bearings.
We carefully demolished the concrete around the bearings using specialized equipment like this wire saw to avoid damaging the surrounding structure.

Completing Post-Tensioning

After releasing the Pier 18 bearings last week, we tightened the post-tensioning strands to 100%, to help strengthen the bridge and mitigate the risk of further cracking. External post-tensioning is like an exoskeleton, designed and installed to strengthen the bridge and support its existing internal post-tensioning system. While we did install what is called an “external” post-tensioning system, it’s not visible from outside the bridge. It’s external to the concrete and runs along the inside of the hollow girders.

Carbon Fiber Wrapping

Once we completed the post-tensioning and the Pier 18 bearing release, we started on a new round of carbon fiber wrapping (that began this summer). This helps support the now stable and strengthened bridge. This is the last step in stabilizing the bridge, and, once it’s done, we will lower work platforms. Again, this is necessary for either demolition or further repairs, so once it’s complete, we’ll be ready to quickly pivot to repair or replace.

Upcoming work

This week, we’ll continue applying the final layers of carbon fiber wrap to strengthen the bridge girders, which support the bridge deck, and inject epoxy into cracks wider than 0.3 mm. We’ll also remove the concrete pieces released from Pier 18.

Over the next couple of weeks, we’ll place the new bearings, and then pour concrete to hold them in place, setting the stage for future repair or replacement.

We expect to complete stabilization work by the end of this year. Once all stabilization work has been finished, we’ll lower the work platforms onto barges and remove other temporary work structures. We’ll continue monitoring and inspection activities after stabilization work is complete, whether the bridge is repaired or replaced.

Construction impacts  

Kraemer North America, our contractor for the stabilization work, is working Monday through Saturday from 6 a.m. to 4:30 p.m. every week to stabilize the bridge. People driving may see lane reductions on Klickitat Ave SW and SW Klickitat Way (on the west and south side of Harbor Island).

Past work  

Stabilizing the High-Rise Bridge is necessary to preserve public safety and the integrity of the bridge so that all options remain on the table with the approaching repair or replace decision. Stabilization puts us on the right path if repair is determined to be the best option and helps prevent further cracking. Check out our blog for information on the progress we’ve made since we closed the bridge in March.

Work This Past Weekend: Paving on 16th Ave SW and Striping on the Low Bridge

16th Ave SW Paving: Crews continued paving work on 16th Ave SW near the north entrance to South Seattle Community College. This work will continue early this week until approximately Tuesday at 10:00 a.m. 16th Ave SW will remain one lane in each direction on the east side of the road (the northbound lanes), which means the capacity is maintained, but parking will remain restricted. Paving is weather dependent and may be rescheduled if the weather is too damp.

Low Bridge Restriping: Crews restriped the left-turn only lane to Terminal 5. This restriping occurred where the markings have faded on the two lanes used to exit the Low Bridge and approach the 5-way intersection at SW Spokane St.

Join us for the Mayor’s Virtual West Seattle Bridge Town Hall

Please join us TODAY – Monday, November 16 – from 5:00 – 6:30 p.m., for a virtual Town Hall on the West Seattle Bridge. To attend, please RSVP

Before reaching a critical decision point about repair or replacement of the West Seattle Bridge, the Mayor will be hosting a West Seattle Bridge Town Hall with key department staff to share updates about recently completed work to stabilize the bridge and reduce the traffic impacts of the closure, updated information for both repair or replacement pathways, and ongoing opportunities for communities to provide feedback. There will also be some time for you to ask questions directly.

West Seattle Bridge Community Task Force Meets Thursday, November 19

The West Seattle Bridge Community Task Force meets for the 13th time this Thursday, November 19 from 3:30 – 4:30 p.m. Mayor Durkan will join the meeting to provide an update and answer any questions.

Watch this meeting live using this link.