SR520 Pontoon Construction?-?Aberdeen, Wash.
More than 115,000 vehicles cross the aging SR520 floating bridge between Seattle and Bellevue on a daily basis, and it was imperative that the Washington State Department of Transportation (WSDOT) provide commuters a new, safer and more modern bridge to withstand potential seismic activity and severe weather. Kiewit-General, a Joint Venture (K-G) was selected as the best value contractor to build the pontoons that will support the new roadway superstructure.
K-G and designers, KPFF and HNTB, completed the design of the casting facility in Aberdeen, WA and assisted WSDOT with the environmental permitting process. Beginning in late 2010, construction began on the casting facility to support the building of these massive concrete structures. More than 80,000 CY of material was dredged from the harbor at the opening of the casting facility, and approximately 308,000 CY of material was excavated from the ground site.
The casting facility was completed in 2012, followed by construction of 33 pontoons in six cycles through mid 2015. The majority of these pontoons measure 360 feet by 75 feet, greater than the length of a football field. As part of a separate contract, the pontoons were towed almost 400 miles around the Olympic Peninsula to the bridge site in Lake Washington.