Eight months before runaway cracks drove the West Seattle Bridge to near collapse, city structures Director Matt Donahue raised a question to consulting engineers.
Do you think the bridge should be closed?
Not yet, the experts said.
“The information gathered to date, while very concerning, is insufficient to make such a recommendation at this time; particularly given the many years of service provided by the structure,” the experts said, according to minutes of the July 31, 2019 meeting between city transportation officials and the engineering firm WSP. Further analysis “could result in a recommendation to close the bridge.”
It was the latest indication of the bridge’s troubles dating back seven years, when city workers first discovered small cracks in the structure.
Yet, from 2013 until early 2020, the Seattle Department of Transportation (SDOT) appeared to take no steps to reveal the bridge’s slow-motion decline to City Council members, mayors or the public, as the city churned through five transportation directors, a review by The Seattle Times has found.
Interviews, reports published by the city and documents obtained through the state Public Records Act show no proposals during that time to reinforce the bridge, even as 100,000 vehicles, including heavy buses and trucks, crossed each day.
Instead, SDOT scaled up its surveillance of the bridge and eventually discussed lane reductions to reduce the load, until accelerating cracks thwarted those plans — leading to its stunning closure earlier this year.
The agency should have made the problem public at least by fall of 2019, City Councilmember Lisa Herbold said. “There’s really a universal response of shock and anger from constituents in West Seattle about this,” Herbold told SDOT Director Sam Zimbabwe.
By March 23, the cracks were growing so rapidly that Donahue, walking inside the hollow concrete girders, called for an emergency closure. Barricades arrived by 7 p.m. that day.
City officials defend the decision to rely on monitoring, and say they acted quickly when the danger became clear.
“The steps that we took early, and the upgraded inspection and observation that we took over time with this bridge as the problem started to emerge, is what positioned us to take decisive action and save lives,” Zimbabwe said in an interview.
“I don’t think we would do any of that any differently.”
Mayor Jenny Durkan last month announced the city would begin a $47 million repair to restore traffic much sooner than replacing the cracked spans. Still, SDOT says the bridge isn’t expected to reopen until 2022.
Bridge design posed a challenge
The corridor’s trouble dates to June 11, 1978, when a freighter struck one of the Duwamish Waterway’s twin drawbridges, leaving four lanes pointed toward the sky.
Making the most of a crisis, leaders demanded a fixed span to cure drivers’ aggravation over frequent maritime openings. The bridge had to be 140 feet high, because the Port of Seattle aspired to build a container terminal upriver. U.S. Sen. Warren Magnuson, D-Wash., working with City Council President Jeanette Williams, secured federal money for most of the $180 million project.
The bridge’s gently-arced shape posed a challenge. To keep the structure aloft, tons of steel cables would need to be threaded through the girder walls and pulled tight, a method known as post-tensioning that strengthens the concrete structure.
Tom Mahoney, coordinator of the design team, recalls he preferred lighter steel beams under the deck, but didn’t advocate for those.
“I knew the steel bridge was $10 million more. I couldn’t justify that,” the 86-year-old Mahoney recalled earlier this year from his home in Bellevue. “A steel bridge, you’ve got to paint all the time, and concrete you don’t.”
The team’s calculations said the primary strains from the bridge’s weight would concentrate toward the middle. So they positioned the primary tensioning cables and anchors to tighten just the central third of the 590-foot-long mainspan.
But the designers added extra ducts where SDOT could strengthen the whole bridge later with more steel cables. Mahoney said he and John Clark, the lead design engineer, believed the original cables would eventually lose tension, so the bridge would need re-tightening. That wasn’t done.
“We were trying to think of everything, when John and I were putting this thing together,” Mahoney said.
An early, optimistic assessment
SDOT inspectors discovered small cracks during a routine inspection in 2013. They were no more than 1/100th of an inch wide.
John Buswell, then-city structures director, followed up by viewing the girders from a bucket lift. His report featured hand-drawn maps of the cracks, lengthwise and across the bottom of a girder, and photos of small diagonal cracks in the walls.
He sought perspective from Clark, who wrote a brief analysis in March 2014. Clark named 10 possible factors for the cracking, including the 2001 Nisqually earthquake. Clark also pinpointed the weak zones where the cracking occurred: four symmetrical locations where the central post-tensioning cables ended.
SDOT followed his advice to seal the cracks with epoxy, attach gauges to monitor any changes and keep watching in case the cracks penetrate the girder walls. If they widen or deepen, SDOT should consider more post-tensioning cables to permanently seal them, he wrote.
Clark predicted that “the cracking does not influence the ultimate load capacity of the bridge.”
That optimism, by a prolific Northwest bridge designer, helps explain why SDOT didn’t attempt a major fix sooner, believes Adam Ludwig, a member of the West Seattle Bridge Now coalition, which supports rapid repairs to restore traffic.
“If I’m reading this, and I were a city manager who doesn’t have the budget to fix stuff, I’d be thinking, ‘I’m glad we don’t have to fix this today, we can fix it tomorrow,’ ” said Ludwig, who is a building engineer.
Clark acknowledged this spring, “I should have been stronger seven years ago when I made the report.” He said it’s surprising SDOT didn’t strengthen the bridge before 2020.
The cracks did persuade SDOT to make yearly inspections, twice as frequent as federal law requires.
Inspectors in 2014 reported that several cracks, ranging between 1/64th and 1/8th of an inch, were wider than before. They wrote “CTO,” continue to observe.
The special inspection also focused on whether cracks penetrated the roughly 1-foot-thick girder walls. The answer was yes. “They were not visible last year, and are visible on the inside this year,” the report said.
And inspectors found another problem: The neoprene bearings above two of the bridge’s piers, that allow thermal expansion as temperatures change, were deformed. SDOT said this year that problem added stress to the concrete.
Beneath the political radar
For years, word of the cracks apparently did not reach City Hall.
Retired City Councilmember Tom Rasmussen, who chaired the transportation committee from 2010-15, said he wasn’t notified of the issue. SDOT should have spoken out, he said, so council members could have included repairs in the city’s capital improvement plan, or sought money in a ballot measure.
Former Councilmember Mike O’Brien, who chaired the transportation committee for four years after Rasmussen, said he also wasn’t briefed on the bridge’s cracks, “not even an offhand remark.”
Peter Hahn, SDOT director in 2013 under Mayor Mike McGinn, said he wasn’t told of the cracks, either. Goran Sparrman, interim director in 2014 and 2018, didn’t respond to interview requests.
Scott Kubly, SDOT director from mid-2014 to 2017, recalls conversations with Buswell, the city’s structures director, about the creaky Magnolia Bridge and seismic improvement needs citywide. Buswell was known for nursing Seattle’s century-old steel drawbridges including University Bridge, where he walked through mud in 2007 to protect the south foundation from a gushing water main.
But he didn’t flag problems in West Seattle, Kubly said.
Linea Laird, interim SDOT director from fall 2018 through mid-January 2019, said by email, “Any issues with the Bridge never rose to my level as something I needed to address. I do recall that SDOT had on-going inspections and monitoring of the Bridge as appropriate.”
Now retired, Buswell declined an interview request, saying he’s collaborating with SDOT and they agreed he won’t speak. Donahue said, “I’m not going to speculate on decisions that were made by my predecessor.”
More cracks, more monitoring
The city heightened its vigilance in late 2018. A review by monitoring specialists BDI from Colorado found that diagonal cracks had proliferated, and would keep spreading, beyond the eight spots where SDOT previously attached gauges. To keep up, BDI suggested 32 more sensors.
The next inspection, in May 2019, found the old cracks didn’t widen, but new ones appeared. SDOT issued work orders to inject more epoxy.
The agency says the epoxy kept out moisture and prevented corrosion of the tensioning steel and rebar, making a repair of the bridge possible.
“Someone saw those cracks and started paying attention to those cracks, which is good practice,” said Mike Sprinkel, a post-tensioned bridge expert and research director at Virginia’s Department of Transportation, which is retrofitting concrete bridges. “It’s a sign something is changing in the bridge that deserves attention.”
New York construction lawyer Barry LePatner encourages a more-aggressive posture — major bridges should be equipped with cameras, strain gauges and fiber-optics for transmitting data in real time, long before problems appear. This strategy is called structural health monitoring.
“Without X-raying an entire concrete structure, or even a steel structure, you can’t tell what’s inside in the early stages of a failure,” said LePatner, author of “Too Big to Fall” that chronicles the 2007 Minneapolis bridge collapse that killed 13 people.
Which brings us back to Donahue’s question last year, whether to close the bridge.
Donahue said he asked that question as SDOT and consultants from WSP, the engineering firm, embarked on an analysis to determine how much load the bridge could handle. The Federal Highway Administration requires new load-rating studies because heavier trucks have surpassed design limits of aging bridges.
Inspections in May and November 2019 found continued decline, including cracks in the two side spans and extensive diagonal cracks in the mainspan that wrapped past the bottom and up the walls. Some were 4 feet or longer.
Then in February 2020, the load-rating study returned bad news. The bridge couldn’t support much more than its own weight and still keep a prudent margin of safety. WSP suggested easing the traffic load by reducing lanes from seven to four, while the city designed a repair plan.
“The investigation we have performed indicates that the structure is not in immediate danger of sustaining damage that requires closure,” WSP project manager Greg Banks wrote in an update Feb. 24. “However, we are dealing with behavior that is at the limits of engineering science to characterize and there is clear evidence that changes are occurring.”
In other words, WSP could no longer predict how fast the bridge would deteriorate, the firm said in response to questions from The Seattle Times. WSP abandoned its initial theory from July 2019 to expect a gradual decline.
“At that time, we thought that any further cracking would evolve slowly over a period of years because the likely causes (concrete creep) would cause small changes over time,” the statement said. Creep is a gradual concrete shrinkage that can weaken a structure.
Donahue began to view the bridge daily in late February and early March. City staff began preparing lane reductions they planned to take effect in April, records show.
Those plans imploded March 19 when WSP advised the city to close the bridge and start work to strengthen it to prevent collapse. “The process is accelerating in some fashion we can’t quantify,” Banks wrote.
On March 23, Donahue entered the hollow girders to see the cracks himself. Some spread 2 feet in just two weeks, climbing the girder wall to nearly meet another set of cracks. He phoned SDOT Deputy Director Lorelei Williams to launch an immediate traffic shutdown.
“That type of growth within a reinforced concrete structure is completely unacceptable. That’s typically the kind of growth you see over years, not over weeks and days,” Donahue told the City Council later.
Was a sooner fix possible?
In hindsight, could the city have avoided a lengthy closure by fixing the span sooner? SDOT says its experts don’t have enough information to say for sure.
Current director Zimbabwe, who didn’t arrive in Seattle until February 2019, said an earlier fix “would have required a prolonged closure of the bridge.”
Just to stabilize the bridge this year and make sure it didn’t collapse, crews had to saw a large opening in the deck to deliver tons of steel brackets and post-tensioning cables, Zimbabwe noted.
Zimbabwe and others also say the city’s acknowledged maintenance spending shortfall isn’t to blame for the failure. In fact, he says the city’s system worked: Crews identified the cracks, monitored them closely and then quickly shuttered the bridge when the risk of collapse suddenly emerged.
“I don’t know having more resources would have changed any way that was managed,” agreed Genesee Adkins, SDOT chief of staff from 2016-19. Adkins said she typically handled crisis management, and the structures team didn’t elevate the West Seattle Bridge to her attention.
“I think this was really the definition of an emerging crisis, that was not anticipated,” she said.
Port of Seattle Commissioner Peter Steinbrueck suggested this summer that the city order an independent investigation into why the bridge cracked. “I still don’t feel like we have a full and clear picture of the causes,” he said in October.
So far, SDOT has declined.
Zimbabwe said the city has gained a full understanding of the bridge’s behavior, and wouldn’t learn much more by such a study.
“I don’t think that it would be very productive to go back into time and try to figure out exactly where, how things went wrong,” he said. “I’ll leave that decision for others.”
City Councilmember Teresa Mosqueda wondered in a meeting last month if the city can recover money in court from companies involved with the 36-year-old bridge construction, because it lasted only a “half-life.”
The mayor said last month she’s had attorneys check the engineering records. “As you know, I’m not afraid to sue,” said Durkan, a former U.S. attorney. The statute of limitations in state law is six years after construction.
Though the city defends its handling of the bridge, SDOT is applying lessons learned.
Contractors will reinforce the mainspan and both side spans by stringing post-tensioning cables through those extra ducts created when the bridge was built. Once reopened, the agency promises structural-health monitoring, plus inspections every six months as part of a predicted $640,000 annual maintenance cost.
And the lower Spokane Street swing bridge, which also is cracking, has been outfitted with electronic gauges and was subjected to load-rating tests this year. The low bridge’s incipient cracks will be sealed by new post-tensioning cables, starting in 2021, before they jeopardize another transportation lifeline.