The cylindrical piles are 18 to 24 inches in diameter and measure 140 feet long. Laid end to end, the 900 piles would stretch nearly 24 miles. The facility must be capable of supporting the weight of six massive concrete pontoons per cycle – estimated to weigh a combined 50,000 tons, including four large pontoons weighing 11,000 tons each.
“It might seem like this a tremendous amount of pile we are driving here, but this foundation must be solid enough to support the concrete casting basin and pontoon production,” said Phil Wallace, K-G project director. “Getting these piles in place keeps us on track to open the facility by the end of the year and finish the pontoons in 2014.”
WSDOT and K-G will construct 33 pontoons at the site to replace the aging SR 520 bridge. Of these, 21 will be the largest pontoons ever built in the state and will be as long as a football field.
In January 2010, Kiewit-General was awarded the $367.3 million project to construct the casting basin facility, including a concrete batch plant and the new SR 520 bridge pontoons.
For more information about the SR 520 Pontoon Construction Project and to view project photos, visit www.wsdot.wa.gov/Projects/SR520/Pontoons.