Let’s remember the sinking of the I-90 floating bridge, on this day in 1990 (November 25)
Travelling always sucks around holidays, and it gets exponentially worse when, I don’t know, a floating bridge sinks. And it happened 29 years ago today, on Thanksgiving.
In November 1990, the Lacey V. Murrow Bridge was 50 years old, and it was being refurbished. A new matching span had been built alongside and was already carrying cars across the lake, so the old bridge was closed to traffic for the renovation project.
Then, over Thanksgiving weekend, as often happens, a big storm blew in to Western Washington. By Sunday, the news from Lake Washington was bad. The Lacey V. Murrow Bridge was no more. Like the Hood Canal Bridge 11 years earlier, it had broken apart and sunk.
Officials and the public were stunned by the sudden loss of the old bridge. Nobody was hurt that blustery November day, but a few construction vehicles that’d been parked on the bridge for the weekend sank beneath the waves. Meanwhile, passenger cars whizzed by on the adjacent new bridge.
When they work, a floating bridge is an engineering marvel. They’re made up of narrow, barge-like, hollow concrete boxes called pontoons. The pontoons are bolted together and then tethered with heavy cables to giant concrete anchors on the lake bottom. The cables help to stabilize the bridge.
But when the old bridge sank it severed anchor cables on the new bridge. Highway officials faced a dire situation. The Murrow Bridge was on the bottom of Lake Washington. The anchor cables on the new bridge were broken, and it wasn’t safe.
You may remember the floating bridge was made up of concrete pontoons. Prior to the disaster, engineers removed the pontoon’s watertight doors so they could work on the bridge. But when a storm arrived on November 25, 1990, the wind-driven water from the lake flooded the pontoons, causing the bridge to sink.
Thankfully, prior to the collapse, construction workers who were working on the bridge noticed it was starting to sink. A few workers were on the bridge when it was going down, but no one was injured or killed.
The then newly opened bridge next to the one underwater did suffer some damage to its anchor cables; because of that, traffic was stopped for a few days.
The cost of the disaster was $69 million.
Sources:
