On September 12, 1993, the rebuilt Lacey V. Murrow Bridge was reopened over Lake Washington in Seattle. The bridge was renowned as being a floating bridge, meaning that it was constructed in such a way as to allow it to float on top of the water rather than requiring the structure be connected to the ground.
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The bridge had actually existed as early as 1940, when its two-mile long structure was composed of 100,000 tons of steel that was floated on over 20 hollow concrete pontoons. At the time, it was alternatively known as the Lake Washington Floating Bridge and the Mercer Island Bridge; it connected Seattle to the west and Bellevue, Washington to the east. Back then, it carried about 5,000 cars a day across US Route 10. By 1989, it was carrying closer to 100,000 cars across what was renamed as Interstate 90.
A floating bridge, of course, comes with its own unique set of problems. During some routine repairs in 1990, construction workers punctured holes in the concrete pontoons before leaving for the weekend. After a few days of heavy rain and high winds, the pontoons filled with water. Workers realized what was happening and tried to pump out the water, but it was too late. Because all the pontoons were tethered together, one sinking pontoon would drag down the rest of the pontoons. The bridge, as you can imagine, proceeded to sink. Thankfully, the bridge had already been closed due to the repairs, so no one was hurt or killed — but it did cost about $69 million in damages.
It took three years to make the repairs, since the whole thing had to be rebuilt from scratch. The bridge was only reopened in 1993 — but it did reveal some valuable lessons about avoiding similar incidents in the future.