by Cara Giaimo, originally posted on Atlas Obscura
This past weekend, Seattle replaced one superlative piece of infrastructure with another. Sitting atop Lake Washington, the new State Route 520 is now the longest floating bridge in the world -- beating its predecessor, the old State Route 520, by 130 feet, the Associated Press reports.
As the Washington State Department of Transportation explains on their website, floating thoroughfares serve different needs than conventional suspension bridges. There's no need to build them in a straight line, or to construct support towers that stretch to the bottom of the lake.
If one were to build a suspension bridge over Lake Washington, WSDOT explains, each support tower would have to be as tall as the Space Needle.
This new bridge has stronger pontoons than the last one, and can withstand more buffeting from wind and waves. It also has a stormwater collection system, bus lanes in both directions, a path for bikes and pedestrians, and the capacity to someday accommodate a light rail system. After a behind-the-scenes tour, GeekWire highlighted the bridge's underwater maintenance gallery, leak detection system, and pontoon-side emergency boxes for distressed swimmers and boaters.
The structure is already quite popular, Digital Journal reports -- Saturday's festivities drew 12,000 people, many of which took part in a 10K fun run, a ribbon-cutting ceremony, and a presentation of the Guinness World Record for Longest Floating Bridge. So many people wanted to greet it that the Washington DOT had to limit shuttles in and out, stranding some early fans.
Inauguration activities continued apace yesterday with a bike ride across the span. Then it's a rest until the real test--a two-phase opening for cars. If all goes well, they'll peel the old bridge out of the water and leave the new one on its own for as long as they can. As WSDOT director of construction Dave Becher told GeekWire, "You want 75 years. But the intent is that it can last indefinitely if you can maintain it."
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