CHOKEPOINTS

West Seattle Bridge shoring work nears completion

Dec 15, 2020, 6:03 AM

West Seattle Bridge, shoring...

(Photo courtesy of SDOT/Flickr)

(Photo courtesy of SDOT/Flickr)

The work to shore-up the cracking West Seattle Bridge is nearly complete, and then it’s time to wait and see if the repairs will stand up to the cold, winter weather ahead.

Camera enforcement going up on Lower Spokane Street Bridge

All of the work on the West Seattle Bridge should be finished by the beginning of next week. This work is only designed to keep the bridge from failing under its own weight, and to accommodate the upcoming repairs that should begin next fall.

Workers have been using giant platforms that they lifted into place under the bridge. Those should be coming down in a week as well.

It has taken a lot to get to this point. Workers have drilled into the bridge deck to access the inside of the concrete spans. They have added steel cables and tightened them inside the concrete to make the structure stronger. They have wrapped the cracking concrete with carbon fiber and added it along the inside of the span as well.

“We’ve installed all the stabilization post-tensioning and installed another layer of carbon fiber wrap after bringing the post-tensioning up to 100%,” the City of Seattle’s Heather Marx told the West Seattle Community Task Force earlier this month.

Contractors will be coating the ends of those steel cables next week as the final piece of the post-tensioning process.

Workers have also fixed the damaged bearings on Pier 18. The bearings had become compressed and did not allow the concrete to expand or contract with weather or weight, which contributed to the cracking. The concrete for the new neoprene bearings has been poured.

So far, so good, Marx said.

“The repairs that we have installed thus far are completed and performing well,” she said. “We need to continue to monitor those repairs through the colder temperatures.”

And that’s the key to all of this. If these repairs and the concrete itself continue to handle the cold weather, the planned permanent repairs should be able to move forward. If the concrete can handle the normal expansion during winter weather, it should be enough to get the green light.

Marx said they are watching the bridge carefully, especially to see if any of the carbon fiber cracks away.

“The very last thing we want to have happen with that carbon fiber reinforced polymer is for a piece of it to fall into the river,” Marx said. “It’s not heavy. It won’t hurt anyone, but it’s not good for the ecosystem.”

The city should know in a few months whether the bridge and these shoring-up efforts passed the test. If they did, repairs will begin in the fall, and should be done in 2022.

There had been hopes that some limited traffic would be able to use the West Seattle Bridge as the repairs were being finished, but the city now says the plan is to open the bridge only after full capacity has been restored.

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