The Longest Floating Bridge: SR 520

At 7,710 feet-long (or roughly 2,350 meters) and 116 feet wide (or 35 meters), connecting Seattle to Bellevue, Wash., the Evergreen Point Floating Bridge has usurped the throne in the Guinness World Records for the Longest Floating Bridge and the World’s Widest. Also known as SR 520 or the Governor Albert D. Rosellini Bridge, takes the record from its original bridge, also named the Evergreen Point Floating Bridge, although the original was 40 meters shorter.

The Washington Department of Transportation opened Evergreen Point Floating Bridge in April 2016 to much acclaim, praising its highlights, including a safer structure resistant to windstorms up to 89 mph; two general-purpose lanes and one transit/HOV lane in each direction; wider, safer shoulders that allow vehicles to pull over in case of breakdown or emergency; a 14-foot-wide bicycle and pedestrian path on the north side of the bridge; and the bridge’s ability to accommodate light rail if the region chooses to fund it in the future.

Its predecessor, who shared the same name as the new one, served its purpose for half a century. It was declared in poor condition and of large seismic risk, so the Washington DOT began construction for its replacement in 2012.

The SR 520 is applying Washington DOT’s ‘Practical Solutions’ strategy for sustainable and efficiency investments. Governor of Washington Jay Inslee, who contributed to our Governor’s Message at our end-of-the-year issue for American Infrastructure magazine, described the ‘Practical Solution’s program. Inslee noted that Washington is striving to improve their planning and oversight systems, not just their infrastructure. “As we move into this new phase of planning and construction, the Washington State Department of Transportation (WSDOT) is implementing ‘practical solutions.’ This innovative approach brings greater strategic and data-driven planning to infrastructure projects that better help us achieve our transportation goals without overspending or shifting traffic elsewhere,” said Governor Inslee. “The cost savings help us stretch our dollars so we can invest even more in preservation work and other important projects.” The program helps engage all stakeholders of the project in the early design stages, ensuring a lucrative yet efficient product.

In addition to meticulous planning, the SR 520 prioritizes safety. The old Evergreen Bridge was susceptible to several environmental factors, including earthquakes and high winds. Because it was designed and built in the early 1960s, long before modern earthquake standards existed, its hollow supporting columns could break and collapse during a major earthquake. And, waves brought on from storms could accentuated the bridge’s vulnerability. Drawspan, anchor cables, and pontoons were in danger of either breaking or cracking due to strong winds.

The bridge’s new West Approach Bridge North, paired with the newly funded Portage Bay Bridge and West Approach Bridge South, is designed to be able to withstand a 1,000-year earthquake event. Its new pontoons, bridge deck and anchor cables can now withstand sustained winds of up to 89 mph, with its standards protecting travelers while simultaneously extending the bridge’s lifespan.

READ MORE

Leave a Reply