International Bridge Technologies

SR 520 Evergreen Point Floating Bridge – Seattle, Washington

Technical details
Washington State Department of Transportation

Construction Completed: 2017

Seattle, Washington
Design/Build Contractor: Kiewit-General-Manson JV, Prime Consultant: KPFF Consulting Engineers
SYSTRA IBT’s Role: Bridge Design Consultant, conceptual design, detailed design, and construction engineering.


Total Bridge Length: 5,135 ft (1,565 m)
113 ft (34.5 m) (six traffic lanes, shoulders, pedestrian walkway).

SYSTRA IBT developed the unique design for the 5,135 ft (1,566 m) long low-rise structure consisting of precast segments supported at a typical 30 ft spacing on top of the floating bridge. This innovative two-way post-tensioned structure is designed to be low profile, with a maximum thickness of 2.5 ft (0.76 m) while carrying 6 lanes of traffic plus a pedestrian walkway for a total deck width of 113 ft-4 in (34.6 m).

SYSTRA IBT also provided technical oversight and construction engineering services for the cast-in-place segmental twin box-girder long span at the east side of the project, which has a total length of 629 ft and a main span of 320 ft. Both structures are pre-designed to be expandable for two additional mass transit lanes in the future.

Additional Awards:

  • 2017 ASBI – Bridge Award of Excellence
  • 2016 DBIA – Award of Merit, Transportation Category

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