When the high-rise West Seattle Bridge reopens in September, after a safety shutdown of more than two years, its gray decks and ramps won’t look much different than they did from 1984 to 2020.
The real transformation is on the inside.
Repair contractors have finished stringing 46 miles of steel cable, or 92 tons, through all three spans to tighten their middle-aged concrete and keep the seven-lane crossing on schedule to open the week of Sept. 12.
An infusion of steel this immense to fix a concrete bridge is rare, and further complicated by an extra step to stabilize it in mid-2020, averting a possible collapse until engineers had time to design a lasting solution.
As the new cables compress the bridge, its concrete volume shrinks a few millimeters. That change creates slack in the external carbon-fiber wrapping that coated the bridge walls during 2020-21, in spots subject to high stress. Therefore another wrapping is needed this month, fastened by workers on hanging outdoor platforms.
“We want to make sure it’s banjo tight across there,” Adam Dour, project manager for repair contractor Kraemer North America, said during a tour Tuesday.
The city ordered the bridge closure March 23, 2020, after diagonal shear cracks suddenly accelerated by 2 feet in two weeks. They were tiny when inspectors discovered them in 2013, so the city filled those with epoxy and continued to observe, in hopes to avoid major repairs. Since the emergency closure, drivers are detouring up to six miles through the congested First Avenue South Bridge.
Inside the hollow bridge, the new support wires are sheathed in tubes, which will be filled with grout this week. That will prevent air exposure and corrosion, while still allowing the Seattle Department of Transportation to inspect the cables using sound testing, Dour said.
Finally, SDOT will conduct load tests using 12 double-trailer dump trucks filled with heavy gravel, making single and group trips and parking on the deck. Electronic gauges detect bridge movements.
“Our expectation is this repair is going to be safe for travel and it will last the 40 years of its remaining life,” said Heather Marx, city project director.
The city decided not to allow a community party, not even a bicycle ride or fun run.
“We’re focused on opening the bridge,” Marx said. An exact date is to be announced Thursday.
The city hoped to finish repairs by June 30 but lost weeks when a concrete truck drivers’ strike in the winter delayed Kraemer North America’s schedule to build anchors for its giant internal cables.
High-bridge repairs, at $58 million, are the biggest piece of the city’s $175 million Reconnect West Seattle budget that also funds repaving, safety projects, engineering, signals and renovations to strengthen the lower Spokane Street swing bridge.
Now complete, the shadowy network of bridge steel looks less like a banjo than a pipe organ, filling the hollow girders with as many as 16 broad tubes. Many hold 19 cables, each exerting 1 million pounds of force, an extreme use of a common bridge-construction method known as post-tensioning.
There are now three generations of overlapping steel tendons: the invisible steel buried within the concrete walls 38 years ago that protected only the center of the center span, a slightly longer set anchored in 2020 to prevent a collapse, and miles of 2022 post-tensioning cables that strengthen each span end to end.
You can still see the writing on the wall, at infamous “Joint 38” where shear cracks formed, and where bridge technicians wrote the dates and lengths of crack movements in black marking pens.
Workers left that wall uncovered by carbon fiber, so experts can watch closely for changes, said Greg Banks, bridge engineer for city consultants WSP. Alarm wires and cameras provide further surveillance.
Before the shutdown, the bridge carried 100,000 vehicles and 20,000 transit riders per weekday, and peak crossings could exceed 30 minutes. Full traffic won’t necessarily return, because thousands of West Seattle’s white-collar commuters have learned to work from home during COVID-19.
Marx said congestion is hard to predict. Traffic jams might be less acute than before, but drivers find heavy volumes all day, as seen on highways throughout the state, she said.
The red bus lane toward downtown will reopen, saving time for transit riders, but it won’t be extended farther onto the northbound Highway 99 cloverleaf ramp as conceived in early 2020.
Three westbound bridge lanes will be re-striped and moved a few feet right, providing a 12-foot-wide space near the median barrier for maintenance. New exit signs will list more West Seattle roads. Some workers Tuesday were stringing wires into light poles, where copper thieves struck months ago.
Seattle DOT took advantage of the closure to make the four-lane Fauntleroy Way hillside road smoother. As longtime residents know, vapor from the Nucor Steel mill condenses onto the road and freezes in winter, causing unwary drivers to hit the curved median divider. Dour said the new surface contains silica for better traction, and will contain grooves known as tining, to reduce water buildup.
On the bridge’s east side, the city is engineering a multimillion-dollar project, after 2022, to rebuild elevated Spokane Street decks that chronically become waterlogged and crumble, leading to pavement patterns SDOT describes as “alligator skin.”