The cracked and barricaded high-rise West Seattle Bridge is already triggering traffic jams on the two-lane bridge below, where drivers are ignoring restrictions that limit the lower crossing to transit, freight and emergency vehicles.
Data last week showed 15,000 daily vehicles on the low bridge, enough to create slowdowns and hinder first responders, said Adiam Emery, intelligent transportation system engineer for the Seattle Department of Transportation (SDOT). The bridge typically carries about half that much traffic.
Full capacity is 20,000 vehicles and would mean stop-and-go conditions, Emery said at a City Council briefing Monday.
Anxiety over the corridor is a taste of what’s to come, when the coronavirus epidemic hopefully eases and people resume driving to work, shopping and other activities. The high-rise bridge could be closed for months as repairs are made.
Councilmember Teresa Mosqueda said she was bicycling Monday morning to visit the Army field hospital being installed inside the CenturyLink Field Event Center when she saw cars clogging the lower bridge.
“I want to echo the concerns about first responders being stuck, and a lot of people using that as a shortcut,” Mosqueda said.
Since the emergency bridge closure March 23, the city has directed motorists to use the First Avenue South or South Park bridges, which require detours as long as 5 miles.
To enforce the lower bridge restrictions, SDOT Director Sam Zimbabwe said “we have support by the Police Department,” along with signs, but enforcement might need to increase. So far, there’s been little or no traffic policing.
“If we have everybody trying to use the lower bridge, nobody will be able to use the lower bridge,” he said.
SDOT finished a safety project Sunday in a busy detour route, by installing a temporary traffic signal at the corner of Highland Park Drive Southwest and Southwest Holden Street. City Councilmember Lisa Herbold and Council President M. Lorena González, who both live in West Seattle, thanked transportation officials for quick work.
Health care workers are asking for access to the low bridge in off-hours, Herbold said. Such flexibility might be possible late at night, depending on what data show, Emery said.
SDOT doesn’t have a timeline or specific plan to add temporary support to the bridge, or for permanent repairs. It will take another three to four weeks before the agency can release time and cost estimates, Zimbabwe said.
Carbon wrap is a leading option, while steel bands could be added to compress and strengthen the concrete, said Matt Donahue, SDOT’s roadway structures director.
Council members politely chastised Zimbabwe’s team for not alerting them and the public sooner to the bridge’s deterioration.
Notifications should have happened last summer, when crack growth spurred SDOT to increase to monthly inspections, Herbold said.
“There’s really a universal response of shock and in some cases anger from constituents in West Seattle about this,” she said. “So in keeping with our commitment to transparency, and no surprises, and preparation, I would really appreciate the department to think about how to adjust its reporting, so we can move toward a culture of — again — no surprises.”
González pressed Zimbabwe about the four-week period, starting Feb. 21, during which council members weren’t told that consultants had suggested a contingency plan be drawn to reduce the seven-lane bridge to four lanes.
Zimbabwe said he shares the goal of transparency, and reiterated that until very recently, the cracking didn’t appear severe enough to require traffic disruptions.
After cracks suddenly accelerated in early March, engineering consultants suggested full closure March 19, said Donahue, a certified bridge inspector. To confirm that, he entered the hollow girders March 23.
He saw that cracks had stretched 2 more feet diagonally, up a girder wall, in just two weeks. Angular cracks like those are known as shear cracks, he said.
“That type of deterioration in a bridge will go until failure, and then failure happens typically quickly and without warning, as opposed to other types of cracking.”
While still inside the hollow girder March 23 he called Lorelei Williams, deputy capital projects director, to say the bridge must be closed that day.
González said, despite her frustration, “I really just want to thank you, Matt, for making that tough call, and for doing the work that was necessary to make sure that we as a city acted quickly to preserve life and safety.”