By Tracy Record
West Seattle Blog editor
With ~3 months to go until SDOT makes the “repair or replace?” decision about the West Seattle Bridge, there’s still time to suggest alternatives. This week, a Seattle architect is pitching one: a “mass timber” replacement bridge.
Matthias Olt is with B+H Architects. While his firm didn’t apply to be part of the official process to pick a consultant to work on a potential replacement, he says, “We think the bridge is such an iconic thing in Seattle, someone should be a voice at the table for design.”
It’s not just a design vision he’s pitching – it’s the material. Including Northwest-grown timber in the mix could make it an icon of sustainability, top, he says. And it would be lighter – as you might recall, part of the challenge posed by the construction of the current bridge is that most of its “load” is its own weight.
What Olt proposes is a hybrid bridge – part steel or carbon fiber, wrapped in wood, with concrete piers. The arches in the arch design would be made of steel. The hybrid material could be half the weight of concrete.
In our conversation, he explained that this also could be slightly less expensive than the traditional concrete construction, and would take up to 25 percent less time – the “mass timber” features, potentially comprising up to 25 percent of the bridge material, would be pre-fabricated at factories in the region (he says there’s at least two in our state) and shipped to the construction site. The use of regional material an builders would mean the project wouldn’t be dependent on, for example, steel from China.
“Mass timber” isn’t a new building material, Olt says – it’s been used in buildings as well as bridges. For examples of the latter, he mentions a few in Quebec, Canada – the Mistissini Bridge and Montmorency Forest Bridge. Also of note: B+H’s sister firm SMEC has major bridge-building expertise.
So what’s next for this idea? Olt says B+H has submitted a “comprehensive design-concept packet” (you can see it here) to the city, and they’re publicizing the idea – talking with us and others – in hopes of sparking some support early in the process. They’ve also started an online petition you can “sign” here if you’re interested in their concept.