For more than 50 years, a pontoon-supported bridge crossing Lake Washington was recognized as the longest floating bridge in the world. In 2016, that claim passed to a newly constructed floating bridge measuring 130 feet longer than the old bridge, but located just a few feet away from the former record holder.
On April 2, 2016, a public grand opening celebration marked the opening of the $1.5 billion Evergreen Point Floating Bridge along State Route 520, which crosses Lake Washington in Medina, Washington, located to the east of downtown Seattle. At the grand opening, the bridge was certified as the longest floating bridge in the world by representatives from Guinness Book of World Records.
The previous floating bridge had exceeded its design life and was showing its age. The bridge pontoons had become vulnerable to windstorms, and its support columns were vulnerable to earthquakes. Constructed adjacent to the original floating bridge, the wider, sturdier bridge features 7,710 feet of floating span.
The bridge is owned and maintained by the Washington State Department of Transportation (WSDOT).
Serving as a member of the general engineering consultant team led by HDR, Inc., WSP USA provided program and project management, tolling and financial analysis, environmental documentation, preliminary engineering, design-build procurement, design and construction oversight and quality management. One of WSP’s key roles included providing revenue forecasting and financial planning for the $4.6 billion program and managing the preparation of revenue forecasts and toll scenario development and evaluation. The firm also assisted the owner in obtaining a $300 million Transportation Infrastructure Finance and Innovation Act (TIFIA) loan.
The State Route 520 program had multiple construction packages, the main one being the Floating Bridge and Landings Project, which had an overall approximate value of $1.5 billion. WSP was integral to the team that prepared preliminary engineering and procurement documents in a very aggressive schedule for this design-build project. The firm’s structure engineers also advised the owner to address constructability issues with the early pontoons and provided successful solutions.
Used by an average of 74,000 motorists every day, the new bridge provides two general-purpose lanes and one transit/high-occupancy vehicle (HOV) lane in each direction. It also features wider, safer shoulders that will allow vehicles to pull over in the case of a breakdown. It supports non-motorized traffic with a 14-foot-wide bicycle and pedestrian path on the north side of the bridge, and has the ability to accommodate future light rail if the region chooses to fund it in the future.