In an hourlong conversation over Zoom, The Seattle Times asked local leaders about the options to repair or replace the cracked West Seattle Bridge as Mayor Jenny Durkan mulled a final decision.
The panelists included Seattle Times transportation reporter Mike Lindblom, and the co-leaders of the city’s West Seattle Bridge task force, former Seattle Mayor Greg Nickels; Duwamish River Cleanup Coalition Director Paulina López; and Seattle Department of Transportation Director of Downtown Mobility Heather Marx.
The discussion occurred Tuesday, two days before Durkan recommended repairing the bridge rather than replacing the large damaged section with new structures.
Below are a few excerpts from the conversation.
Q. What does a repair process look like?
Mike Lindblom: Repair essentially consists of using post-tensioning steel to tighten and compress … the three, hollow girder mainspans that are the highest in the air. By compressing those, you can get more life out of the bridge and seal the cracks. There is also extensive carbon wrap that adds some additional structural strength to the bridge and is a belt-and-suspenders approach against new tensions forming in the concrete. Repairs could last 15 to 40 years depending on some variables, including whether the city chooses to do underground seismic strengthening.
Q. What do the replacement options look like?
Heather Marx: We could replace [the center section of the bridge] with another concrete box girder, drop the tail spans in the center span and replace it in kind. Or instead of using concrete, we could replace [the center section] with steel box girders on all three sections. Those two have been contemplated in the cost-benefit analysis. The latest option, though, would be to create a tiered network arch out of steel. We would drop the tail spans in the center section and replace it with prefabricated steel members, much like the bridge across Lake Champlain.
Q. Is a tunnel option on the table?
Marx: The tunnel was thoroughly examined in the cost-benefit analysis and turned out to be really expensive to build, really expensive to operate and maintain, and would take a really long time to implement.
Q. Could a replacement incorporate Sound Transit Link light rail?
Greg Nickels: It’s awkward because Sound Transit is already in their environmental process. What we should have learned from this episode of closing the bridge is the desirability of redundancy. If we have a separate bridge that has light rail [and a] vehicle bridge that is either repaired for a fairly long-term or built again, we have redundancy. One goes out, the other is still there and we’re not cut off and we’re not impacting other communities the same way we are today.
Q. What are the climate impacts?
Paulina López: This is an urgent situation. The West Seattle community is suffering, but also thinking about the other communities like those in the Duwamish Valley. We know that we are already impacted from all the environmental burdens that historically have been in South Park and Georgetown. How do we take these into consideration? How do we embed equity, environmental justice practices on the traffic impacts that are happening? Having an additional 100,000 vehicles around our neighborhoods is not really a good thing.
Q. Could the West Seattle Bridge be tolled?
Nickels: The task force has not tackled that. Putting together a financial plan is going to be a very difficult thing. Whether it’s repair or replacement, it’s going to take a lot of work. I think all options are probably on the table. I suspect tolling will be one of the less popular, but you’re going to have to find a way to finance whichever route you take.