SR 520 Floating Bridge and Landings Design/Build

The SR 520 Floating Bridge and Landings Project designed and built the world’s longest floating bridge, creating a safer, more reliable link between Seattle and the growing high-tech cities east of Lake Washington. With HOV lanes, full shoulders for disabled vehicles, a cross-lake bicycle and pedestrian path, and the largest, heaviest, and strongest bridge pontoons ever built, the new, 1.5-mile-long floating highway dramatically improves the movement of people and freight in the Central Puget Sound region. The Washington State Department of Transportation (WSDOT) considered traditional delivery options but decided that the design-build model was a perfect fit for this project because design-build did several things: it allowed fast-track delivery of the new bridge replacing a vulnerable structure, it allowed greater innovation and potential cost savings to WSDOT, and it shifted appropriate project risk components to the design-builder. KPFF provided prime design, civil, structural, and mechanical engineering services, as well as construction quality assurance management.