Construction teams perched above the Skagit River are about to lend new meaning to the phrase Skid Road.
They will attempt Saturday night to jack up a new 915-ton bridge span, slide it upriver on steel rails, then set it onto the old columns of an Interstate 5 crossing — in a single overnight work shift.
If the operation goes well, drivers on Sunday morning will zip across the new span.
The original north span of the freeway bridge collapsed May 23 when a tall truckload hit several overhead crossbeams. A military-style bridge was temporarily installed June 19, with a reduced speed limit of 40 mph.
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State engineers initially thought they would need a three-day traffic closure to install a permanent span. Instead, it’s happening in a 12-hour shift.
The Department of Transportation (DOT) scheduled the big skid at night to reduce effects on traffic; the span averages 71,000 vehicles a day. One lane each direction will close at 5 p.m., with all lanes closed by 7 p.m. Drivers will detour through the business district of Burlington.
In 2008, the DOT replaced the I-405 Northeast Eighth Street overpass in Bellevue using a similar strategy. Contractors built the new crossing parallel to the old one — then rolled it into the final position.
This weekend at the Skagit River, the skidding operation will rely on a Teflon surface, affixed to a set of steel rails, to reduce friction as the concrete span is pushed 76 feet east. Hydraulic rams, cinched to the rails, will nudge the structure a few feet at a time. A set of jacks, supporting the bridge, will slide on a Teflon-coated groove within the beam.
The new $7 million span contains nine concrete girders, 160 feet long, that were joined and decked above the river. Doing so required a crane onshore to swing each girder over the river, then pass it to a second crane.
The permanent bridge is being built by Max J. Kuney of Spokane, the same company that is replacing a stretch of I-90 east of Snoqualmie Pass.
“It’s going to be a pretty cool project,” said Max J. Kuney IV, president of the company founded in1930.
“Sometimes life throws you a curveball, but hopefully we will get done within 12 hours. If we don’t, we will be done in very close to 12 hours,” said Kuney. “That is our plan.”
Kuney hired Parsons Brinckerhoff in Seattle for Skagit bridge engineering, and Omega Morgan of Portland to tackle the heavy lifting and skidding. In January, Omega Morgan moved a 1,100-foot-long, 3,400-ton steel span of the Sellwood Bridge, above the Willamette River in Portland.
Kuney said it should take two hours to skid the new span into the gap on I-5. The movement will be slow and “very linear,” he said. In other words, the pace can’t be rushed, and there is no way to recover time if there are delays.
There will be only 2 inches between the new road deck and the neighboring decks.
Speed limits Sunday will begin at 40 mph, and if traffic moves smoothly, the limit can rise to 60 mph by afternoon, said DOT spokesman Travis Phelps.
The quick bridge delivery is causing the public and politicians to ask why the state can’t be more efficient on other highway jobs, which seem to take years and hundreds of millions of dollars. The Skagit project benefited from emergency funds from the federal government, and exceptional cooperation among agencies.
Gov. Jay Inslee has lauded the project as proof of the state’s can-do attitude and professionalism of the DOT, while the state Senate has organized statewide forums to talk about cost-cutting reforms. Inslee plans to debrief DOT after the I-5 job to look at lessons learned, said spokesman David Postman.
The original Skid Road, on what is now Yesler Way in Seattle, got its name from the timber that was slid downhill on the dirt road to a lumber mill in the 1800s.
Mike Lindblom: 206-515-5631 or firstname.lastname@example.org. On Twitter @mikelindblom