Uncertain fate of West Seattle Bridge creates challenges in planning
The major point of connection for West Seattle’s residents and the rest of the city has been closed for five weeks. A lot remains unclear for the West Seattle Bridge’s future.
The Seattle Department of Transportation has outlined preliminary steps toward working on the bridge. But it remains unclear if repairing the bridge is technically or financially possible, SDOT’s director Sam Zimbabwe said in a presentation to Seattle City Council on Monday.
“We are at very early stages. We’re at zero percent of design, and each step will impact what is feasible and how long it will take,” he said.
The high-rise bridge was closed on March 23 when crews discovered rapid growth in cracks along the center of the bridge. The low bridge remains open to restricted traffic, including emergency vehicles, freight and public transit.
The high bridge is unlikely to reopen to traffic until 2022. SDOT’s director of downtown mobility Heather Marx worries about what happens after the public health orders around coronavirus are lifted.
“The current detour and alternate routes cannot support the level of traffic that we had before the stay-at-home order,” Marx said.
She said SDOT is identifying additional ways to mitigate traffic impacts, and many will be adjusting to changes in how they get in and out of West Seattle. Marx compared the closure of the bridge to the closure of the Alaskan Way Viaduct.
“It’s a similar level of traffic each and every day, but with a lot fewer reroute choices, and we have had a lot less time to plan,” Marx said.
SDOT is modeling potential scenarios for the cracks in the bridge that led to its closure to plan for the worst-case scenario — the bridge becoming more unstable.
“It’s still our assessment that the bridge is not at imminent risk of failure,” Zimbabwe said.
Those worst-case scenario plans could include removing traffic from the low bridge and surrounding areas beneath the bridge for a period of time if the high bridge became unstable, according to an SDOT blog post.
Zimbabwe said SDOT will be installing sensors in the next few weeks throughout the bridge to track the progress of the cracks in real time. The bridge is currently being inspected daily.
Repairing the bridge remains a major question mark for SDOT. Zimbabwe said the first step before any work can move forward needs to be stabilizing the bridge. That will include repairing a locked bearing and shoring the bridge. The locked bearing is preventing the bridge from moving how it is supposed to in response to traffic or temperature changes, creating extra stress for the structure.
According to SDOT’s schedule for the bridge project, early design work for the shoring process and the release of the locked bearing will begin this spring and summer. Zimbabwe said officials should get a better idea of what further work is possible for the high bridge during these early stages.
“We’ll have a better understanding of what repair is possible, what our pathway toward repair would look like, but also be considering what the long-term future of the bridge is and whether early replacement is a more prudent path,” he said.
Shoring construction won’t be complete until spring 2021, according to SDOT’s schedule.
SDOT has projected the early stages of work to stabilize the bridge to cost $33 million. That estimate includes monitoring and stabilizing the bridge, community outreach, traffic control and mitigation, and maintenance on the lower swing bridge.
“I’m really surprised at the number of constituents who’ve been contacting me and saying don’t spend the $33 million, let’s move towards rebuilding the bridge now,” said city council member Lisa Herbold, who represents West Seattle and South Park neighborhoods, during the Monday briefing.
Zimbabwe said stabilizing the bridge through the shoring process is a public safety issue. He also said the current budget doesn’t anticipate any demolition of the span.
“There are a lot of potential budgetary implications of going in a different path,” he said.
If repairing the high bridge is possible, it could add an additional 10 years of use to the bridge. Zimbabwe expects it will still need to be replaced much sooner than anticipated when it opened in 1984. The bridge was designed to last 75 years.