By Tracy Record
West Seattle Blog editor
Repaired bridge in 2022 or mostly new bridge in 2023?
That’s what the repair-or-replace decision could boil down to, now that a “rapid span replacement” has been vaulted into the mix.
The first hour of today’s Community Task Force meeting was devoted to an exploration of that concept. We’ll report separately tonight on the second part of the meeting, a discussion of the newly released Cost-Benefit Analysis, which does not include the “rapid span replacement,” though SDOT‘s project team points out that would fall in the CBA’s Alternative 4 “superstructure replacement” option.
If you missed the meeting (the viewing link was changed at the last minute), here’s the hour-long presentation and discussion of the new concept, which was described more than once during the meeting as “intriguing”:
Shown during the presentation was this animation of how the span replacement would be installed:
“Online replacement is the only option if speed is (a major) priority,” Zoli said, also noting that some of the existing structure would be reused, “mazimizing the seismic performance of the existing substructures.” He noted that the Duwamish River is “as busy a navigation channel as there is” – citing the low bridge’s need to open 1800 times a year. Earthquake performance is crucial because our area is ‘about due” for a big quake. At Lake Champlain – where HNTB built a bridge like this a decade ago – he said they replaced 2,000 feet of bridge “online” – compared to 1,300 feet that would be required in West Seattle – and replaced some of the substructures, all in 18 months.
He showed the animation of how the construction would work, maybe even opening half the new section before the other half is ready. “While we’re demolishing the existing West Seattle Bridge, we’re designing and building the new West Seattle Bridge … simultaneous parallel activities is the strategy for speed.” The “heavy lift” method of demolition would be utilized; that does not involve explosives.
As for the seismic concerns – liquefaction, settling – this type of bridge would include “seismic isolation.” “The beauty of a bridge like this …is that we could reduce displacement.” Also, the structure would be much lighter, 40 percent lighter than the existing bridge. And it’s more easily assessable after a quake. One challenge: The constraints of the West Seattle Bridge site, with another bridge right beneath it, so using barges would maximize how they work with that.
The arches would be 450 feet or less because of a “delta” structure at each end:
Zoli said they also have developed a ‘coating” methodology that would increase the life beyond traditional paint. They also feel permitting time could be reduced.
All this, he says, would get the timeline for building this bridge close to the timeline for repairs: “Our goal is to have the new bridge open in the first quarter of 2023 … we feel that’s feasible given the fast track.” And they think it could last 100 years.
Q&A: Community Task Force co-chair Greg Nickels asked about the scale compared to Lake Champlain That one was $80 million, delivered in 2011. Narrower bridge but comparable square footage. What about the clearance over the channel? Zoli said they could “gain 10 feet of additional clearance” with this type of construction, to 150 feet, and even widen the channel, because the arch span is ‘shallower.’ Nickels also wondered how this could be done fast and yet safely and cost-effectively. Zoli insisted it could, and said speed ranks first, while acknowledging “this is an enormously difficult site. … We owe you a very durable, very safe bridge … this is not a place for compromising.”
Co-chair Paulina Lopez wondered about the environmental impact to the Duwamish River. The fact that this would minimize in-water work was reiterated by Zoli. “Our goal is to stay out of the water … staying out of the water reduces the impacts.” Some construction activities affecting the water are unavoidable but could happen “in the existing alignment.”
West Seattle Bridge NOW‘s Jen Temple asked about funding – how can the process to procure it not extend this “rapid” timeline? Zoli said the two parts of the job that would “take the first year or so are demolition and fabrication … those are relatively small costs,” and the city already has some funding that could go toward that. “There’s not big outlays associated with the first year, year and a half of construction.” Installation is where the “big dollars come in.” Permitting streamlining would facilitate that.
Temple pressed, “So one of the risks is we could get a year in and still not have funding.” Zoli said that “we have a group that’s going to focus on that. … With this significant a bridge out of service,” he thinks that funding would not be a problem. “It may be complex funding …” Marx interjected that “for ANY option, even just repair, we’re going to need financing help. … it is multi-faceted and we’re not relying on any one source.” Nickels cited many past projects that didn’t have all the financing lined up before “we looked over the edge and jumped.”
Anne Higuera of Ventana Construction (WSB sponsor) wondered about the integrity of the existing piers – noting that replacement is mentioned in the CBA – and has that been taken into account for this concept? Zoli replied, “In order for us to (need) as little strengthening as possible, the strategy is to make the bridge much lighter,’ and incorporate the aforementioned “seismic isolation.” He said the piers were originally designed with good seismic capacity, as were “the foundations” – more than many designed in the 1980s. They’re “robust and enormous” and would give engineers/builders a lot to work with to deliver a “much lighter bridge.”
West Seattle Chamber of Commerce rep Dan Austin expressed skepticism about the concept of fast-tracking environmental permits. Have they spoken with local tribes? Marx said they’ll be talking to the Muckleshoot Tribe soon. The barging of components would not impact the fisheries, she suggested. And, Austin wondered, would they get analysis of this option the way that the CBA analyzes other options? Marx explained that this is just another form of Alternative 4, “superstructure replacement. … Fundamentally the Cost-Benefit Analysis is not about which version of (an alternative) we choose – it’s about an archetype.” The 12-week Size/Type/Location study to follow a decision would narrow in on that. “Ted is bringing us a compelling idea,” but this does not represent any kind of decision. Austin said this is going to sound to the public like this is a done deal. It’s not.
Peter Steinbrueck, Seattle Port Commission president, also voiced concerns about permitting and funding. “I do elieve miracles can happen if there’s a will .. but they’re rare.” Would the low bridge have to be shut down during demolition/construction? he also asked. Zoli said there wouold be a 24-hour shutdown for lifting the spans – Lake Champlain required 12 hours. “One time outages for each lift or lower” – probably two for removing the existing span, two for lifting the new archives, so four 24-hour closures. Zoli added, “I cant think of a project in the country that’s more worthy of a fast-track replacement than this bridge.” They had some challenges at Lake Champlain, too, he said – dealing with two states (VT and NY). “Everyone’s going to have to come to this with a can-do attitude,” Marx added.
If this is a version of Alternative 4, would the cost be comparable to what’s posited in the CBA for that option? asked City Councilmember Lisa Herbold. They haven’t crunched the numbers but “probably,” Marx suggested, adding that SDOT has become “increasingly intrigued” by this idea. Zoli noted that the “much faster” aspect of this (the Alternative 4 archetype was suggested as not opening until 2026) is the big differentiator.
Diane Sosne of SEIU Local 1199 said this is more about “political will” than “miracles.” Is there anything from other rapid replacements such as the much-discussed Genoa, Italy, bridge that suggests lessons to be learned? Zoli spoke again about speed and said this is probably the top U.S. project right now that mandates it.
SDOT director Sam Zimbabwe assured CTF members that the project team is pursuing answers to these questions and more. He reiterated that “even if we’re on a repair pathway, we eventually would have to replace the bridge … if we are on this pathway to a replacement, before we take steps we can’t walk back from, we would answer those questions.”
Nickels asked Zimbabwe to recap what the Size/Type/Location study would do, if replacement is the decision. It would “get to a level of preliminary engineering” that would provide some cost information and help the funding process. The study would bring them very close to having “construction documents” for a design-build process.
In thanking Zoli for his presentation, Nickels again called the idea “incredibly intriguing.”
WHAT’S NEXT: Community Task Force members will continue mulling the Cost-Benefit Analysis, and will meet again next Wednesday (October 28th). Meantime, we’ll report on that part of today’s CTF meeting in a separate story later tonight. And if you have questions for SDOT, bring them to tomorrow night’s West Seattle Transportation Coalition meeting (6:30 pm Thursday, online, viewing/participation info on WSTC’s calendar).