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520 Bridge replacement
Wed April 25, 2012
Pontoons taking shape, creating jobs in Aberdeen
Washington State is the floating bridge capital of the world. We have four of the most famous ones, including the longest: State Route 520, which is about to be replaced.
What holds them all up? Giant floats made of concrete, called pontoons. The first and largest of them are being manufactured in Grays Harbor, near Aberdeen.
In the harbor, what was once a sprawling riverfront log yard has been transformed into a gigantic casting basin on the Chehalis River.
Tower cranes loom overhead, ready to lower in pieces that are built on the 55 acres of gravelly ground surrounding a massive and carefully constructed pit at the center of it all.
“It’s kind of set up like a Jiffy Lube pit, where you get an oil change,” says project director Phil Wallace.
He’s overseeing the pontoon construction for Kewit-General, the joint venture that won this design build contract. He says they’ve built a huge manufacturing facility to deliver precision parts on a massive scale.
“So we can flop all the materials, there’s a jig that goes in. We set up all our strong backs, drop all those, then all the ribs for the form go in.”
Translation from engineer-speak: there are all kinds of guides and braces involved.
“It’s just like a puzzle piece, where you put all the puzzles in,” says Wallace.
It’s precision work, yet the pontoons they’re building are huge. They’ll be three stories tall and more than twelve times as long.
“If you put a pontoon in the middle of Century Link Field, it would go from end-line to end-line – nearly the full width of the field. That’s one pontoon, ”says Dave Ziegler with the state Department of Transportation.
In Aberdeen, they’re building 33 pontoons in all, including the 21 largest ones that will be linked together, almost like Lego pieces, to form the foundation of the new six-lane bridge.
“Those become the spine or the basic structure that the road sets on in Lake Washington. So the pontoons that are being built here are just the foundation. Those will be taken up to Seattle and that’s where they’ll attach the roadway, driving surface, ” Ziegler says.
To get to Seattle, the pontoons will be towed up the coast, around the Olympic Peninsula and through the Ballard Locks. They have to fit through – with just 5 feet leeway.
Kewit-General’s Phil Wallace says even a slight tilt in one direction could blow the whole project. Computer aided drafting helps ensure the pontoons will be able to get where they need to go.
“You figure out how it’s going to float even, how to ballast that pontoon so it’ll float level and get through the locks at the right depth too,” Wallace says.
Along with CAD technology, new formulas for concrete mixing are part of what will make these pontoons last for at least 75 years.
All of this is creating hundreds of jobs – about 450 at the project’s peak.
Among the new hires is 25-year-old Rachell Nordberg.
“I was raised in Aberdeen, Washington. I left in 2005, I did 6 years,” she says.
She joined the army and did tours in Iraq and Afghanistan. Now she’s a carpenter in the union’s “Helmets to Hard Hats” program, helping build forms for the pontoons - and very happy to be able to live back at home with her 3-year-old daughter.
“I just really, really like being local. It’s nice, you know you don’t have to go far away and I’m at home to cook dinner. So it’s really nice being local, ” she says.
Her job is in her hometown, but the bridge she’s helping to build is more than a hundred miles away. WSDOT says this kind of regional cooperation should create good will from rural residents who sometimes look disdainfully on transportation budgets for big cities like Seattle.
And drivers on the new 520 bridge can think of the coast as they cross Lake Washington.
One more thing: like ships, the largest pontoons have names. The first four are called Tina, Ursula, Valerie and Wendy.
It’s not yet clear what will happen to the facility in Grays Harbor once the pontoons are done in 2014, but the hope is it will attract more work. Engineers say their CAD drawings show it’s big enough to handle an air craft carrier.
520 floating bridge