Seattle’s Lake Washington is so deep that support towers for a conventional suspension bridge would need to be nearly as tall as the Space Needle. As a result, engineers opted to build the world’s longest floating bridge – and it was just completed this month.
At 7,710 feet, or nearly one and a half miles, the SR 520 tops its predecessor by about 130 feet. The old bridge, which opened in 1963, will likely be torn down later this year. Transportation officials say that most of the bridge’s materials will be either recycled or reused.
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Besides its impressive length, the new bridge boasts improvements such as a 14-foot-wide path for bikes and pedestrians that the old bridge lacked. It’s also equipped with over double the number of pontoons, and is engineered to be more resistant to waves, earthquakes, and winds up to 89 miles per hour. The SR 520 is wider, includes carpool lanes in each direction, and it could also be modified to include a light rail in the future. It’s built to last for at least 75 years, but construction director Dave Becher said it could last “indefinitely” if properly maintained.
Over 12,000 people celebrated the grand opening with a 10K race that traversed the floating marvel. After the race, food trucks, science exhibits, and the presentation of a Guinness World Records certificate entertained the 25,000 to 30,000 people that came to see the bridge.
Assistant Project Engineer Chris MacDonald said, “It’s not an iconic structure in the sense of the Empire State Building. But it is going to be something that when they compare it to the old bridge, it’s not just functional, it does have some aesthetic appeal. People 100 years from now are going to say, ‘It’s still a nice bridge.’”
It took just over four years to build the new bridge, which is slated to officially open for westbound traffic on April 11 and eastbound traffic on April 25.
Images via WSDOT Facebook