Rare look underneath the West Seattle Bridge as crews prepare for final phase of repair

The Seattle Department of Transportation provided a rare look inside the West Seattle Bridge on Thursday.

There are big arches in the middle of the West Seattle Bridge and FOX13 got an inside look at one of the arches on the south side, specifically, inside one of the big arches seen in the middle of the bridge

The city’s lead bridge engineer Matt Donahue said it was in that area that crews first began noticing the cracking.

On the walls, the bridge city workers marked the cracks with a black sharpie indicating each growth by date.

The West Seattle Bridge was shut down in March 2020, and has been closed ever since to avoid becoming a danger to the public and to prevent further damage.

"That post-tensioning strand stretched out over time and changed the way the load moves through the bridge to an area of the bridge, specifically the floor, the girders that we’re about to go into, in a way that those box cutters weren’t designed to take the load and that’s what caused the cracking," said Donahue.

Donahue is also the Director of Roadway Structures Division at SDOT, and said an instrumentation system was installed to monitor the bridge for safety before it was stabilized last year.

That system provided data that was analyzed and helped the team design the stabilization and now the long-term repair.

Construction crews will return to the bridge later this year to begin the final phase of repairs. The remaining project has a price tag of nearly $55 million, with 70 percent of it being funded with federal dollars.

"Design and testing are extremely important," said Heather Marx, Director of the West Seattle Bridge Safety Program. "So we only have to do this once, so we wanted to get it right the first time and that’s why we’re making sure we’re hitting all the steps."

Donahue said the public should feel confident in the innovative design, with less than a year before traffic returns to the bridge.

"Cracking has virtually come to a halt," said Donahue. "As soon as the bridge stabilization measures went to place, as soon as we tensioned up the post-tensioning strand, cracking slowed down to almost nothing."

Crews said the project is on budget and on schedule for mid-2022.

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