World’s Longest Floating Bridge Becomes Third HDR Project to Win American Council of Engineering Companies’ Highest Award

SEATTLE--()--The State Route 520 floating bridge earned the American Council of Engineering Companies’ Grand Conceptor Award, given annually to the nation’s best overall engineering achievement. The award marks the third Grand Conceptor Award for an HDR project in the company’s 100-year history.

The Grand Conceptor presentation highlighted ACEC’s 50th anniversary Engineering Excellence Awards Gala in Washington, D.C., Tuesday evening. Dubbed the “Academy Awards” of the engineering industry, a panel of nearly 30 judges selected the year’s most outstanding engineering accomplishments from among 162 entries, including 13 HDR projects.

In addition to the award for SR 520, HDR’s Kansas City Streetcar project received one of ACEC’s 16 Grand Awards, while the firm’s U.S. 36/Boulder Turnpike Express Lanes project in Colorado earned one of 20 Honor Awards.

HDR also shared honors on two other awards, with partner GZA GeoEnvironmental, Inc. leading the nomination for the foundation design for the New NY Bridge, which won a Grand Award, and WSP/Parsons Brinckerhoff nominating the Cincinnati Bell Connector, winner of an Honor Award.

Part modern marvel and part practical mobility solution, the new SR 520 floating bridge enables multiple modes of land-based transportation to simultaneously cross the state’s second-largest natural lake. The project included replacing the existing, 53-year-old floating bridge and reconstructing the rest of the SR 520 corridor, from Interstate 5 on the west side of the lake to Interstate 405 on the east side.

The result is a bridge that, at 7,708 feet (about 1.5 miles), has earned a place in the Guinness World Records as the longest floating bridge in the world. It is 130 feet longer, has a bridge deck 56 feet wider and uses 44 more pontoons than its predecessor. When the entire SR 520 corridor project is complete, the bridge will carry about 10 percent more vehicles and 17 percent more people during peak traffic hours, while reducing rush-hour, cross-lake commutes between Seattle and Bellevue by about half an hour.

With depths as great as 214 feet, Lake Washington can not be traversed using traditional bridge design, creating the need for innovative design. In 2006, the Washington State Department of Transportation selected HDR to serve as general engineering consultant on this multi-phase project. HDR and WSDOT staff co-located to a central project office, and from this location, led efforts related to all aspects of design and construction collaborating with 120 subconsultants.

Key team members include:

  • Kiewit/General/Manson (KGM): Construction
  • KPFF Consulting Engineers: Civil, structural and mechanical engineering
  • BergerABAM: Civil and structural engineering, roadway design
  • WSP | Parsons Brinckerhoff: Project Management, tolling and finance, and environmental engineering
  • Parametrix, Inc.: Environmental engineering
  • EnviroIssues, Inc.: Public outreach and planning
  • Shannon & Wilson, Inc.: Geotechnical engineering

Other HDR projects receiving ACEC National Recognition Awards included:

  • Bluffton Parkway Phase 5A, Bluffton, South Carolina
  • Bridge Creek Surface Water Treatment Plant, Bend, Oregon
  • Council Bluffs Interstate System Railroad Relocation, Council Bluffs, Iowa
  • Government Center Station Reconstruction, Boston, Massachusetts
  • Iowa Premium Water Treatment Plant, Tama, Iowa
  • Jackrabbit-Big Sky Transmission Line, Big Sky, Montana
  • South Platte Interceptor, Denver, Colorado
  • U.S. 190 Copperas Cove Reliever, Copperas Cove, Texas

About HDR
For more than a century, HDR has partnered with clients to shape communities and push the boundaries of what's possible. Our expertise spans 10,000 employees, in more than 225 locations around the world — and counting. Our engineering, architecture, environmental and construction services bring an impressive breadth of knowledge to every project. Our optimistic approach to finding innovative solutions defined our past and drives our future.


Jackie Fox, 402-926-7058
Mary Zgoda, 402-399-1372

Release Summary

The State Route 520 floating bridge becomes the third HDR project to win the American Council of Engineering Companies' Grand Conceptor Award, engineering's highest honor.


Jackie Fox, 402-926-7058
Mary Zgoda, 402-399-1372