SR 520 Floating Bridge and Landings Design/Build

Seattle, WA



Kiewit General Manson, a Joint Venture

Services/Project Type
Roads and Bridges
Vehicle Bridges
Pedestrian Bridges
Roadway Design

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.

This project recently won the 2017 American Council of Engineering Companies (ACES) Grand Conceptor Award.



Awards & Recognition

2017 ASCE Seattle Section, Local Outstanding Civil Engineering Award 2017 for Structures

2017 ACEC Top Engineering Feat – Grand Conceptor Award

2017 APWA Top Transportation Project of Year (over $75M)

2017 WACA Excellence in Concrete – Public Works, Bridges

2017 ACEC Gold Award Structural Systems, Engineering Excellence Awards

2016 DBIA Excellence in Design (Engineering) 

2015 DBIA National Award of Merit