Technical details
Washington State Department of Transportation

September 2011: Construction started
April 2016: The new bridge was opened to traffic

Conceptual design, detailed design, and construction engineering
Seattle, Washington, United States
Floating Bridge, Precast Segmental

The SR 520 Evergreen Point Floating Bridge is a 2,652m long project crossing Lake Washington near Seattle, in the USA, combining both floating and fixed base bridge segments.

A unique design

The unique construction consists of a 5,135ft (1,566m) long low-rise structure of precast segments supported at a typical 9m 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 2.5ft (0.76m) with a total deck width of 113’-4” (34.6m) carrying 6 lanes of traffic and a pedestrian walkway.

SYSTRA is responsible for technical oversight and construction engineering for the cast-in-place segmental twin box-girder long span at the east side of the project, which has a total length of 192m and a main span of 98m. Both structures are pre-designed to be expandable for two additional mass transit lanes in the future.

Numerous awards

The SR 520 Evergreen Point Floating Bridge has received the following honors:

  • 2017 American Council of Engineering Companies
  • Grand Conceptor Award
  • 2016 Design-Build Institute of America
  • National Award of Merit
  • Excellence in Design

Project Key figures

  • Total length: 1,566m
  • Width: 34,6m
  • Thickness: 0,76m
  • 6 traffic lanes and a pedestrian walkway
  • 77 concrete pontoons
  • 58 anchors
  • 74,000 vehicles per day

The project in pictures