ABERDEEN – Progress spread smoothly and evenly earlier today as crews completed the first concrete pour in a casting basin that will later churn out 33 massive pontoons for a new State Route 520 floating bridge.
The milestone signals momentum on the SR 520 Pontoon Construction Project for the Washington State Department of Transportation (WSDOT) and Kiewit-General (K-G), which began work in February to construct the pontoon casting basin.
Today, Bayview Redi-Mix, Inc. of Aberdeen placed approximately 660 cubic yards of concrete during the pour, constructing an 18-inch thick slab segment. Additional segments will be poured in coming weeks and will total approximately 10,300 cubic yards of concrete for the basin floor alone. The concrete is strengthened by a network of steel rebar mats and reinforced by foundation pilings that plunge 120 feet into the ground.
All this support will be needed later this summer as work begins inside the basin. Crews will build 33 of 77 new pontoons needed to build a new SR 520 floating bridge in Seattle. The pontoons – some as tall as three-story buildings, as wide as two motor homes parked end-to-end and as long as a football field – will weigh as much as 11,000 tons.
“Pouring concrete at the casting basin and building this foundation really sets the table for pontoon construction,” said Dave Ziegler, WSDOT principal engineer. “As these pours continue and our base slab grows in size, we’ll have the work area to start showing real progress on the SR 520 pontoons.”
Pontoon construction is on schedule to start later this summer as crews build smaller interior walls alongside the casting basin. The first cycle is scheduled to be completed in 2012. A pontoon cycle will be completed approximately once every five months, and all pontoons are scheduled to be completed by mid-2014.
“Keeping this project on time and on budget are a few of the ways we’ll measure its success when all is said and done,” Ziegler said. “Constructing the casting basin as efficiently as possible is certainly one of the keys that will help us do this.”
Work on the casting basin facility, which includes a concrete batch plant and on-site water treatment, is scheduled to conclude in October. Construction in Aberdeen is part of a $367 million project that will deliver the casting basin facility and the new SR 520 pontoons.
For more information about the SR 520 Pontoon Construction Project and to view project photos and the project webcam, visit www.wsdot.wa.gov/Projects/SR520/Pontoons.