Citicorp Center opened in Manhattan in 1977 on four columns placed at the midpoint of each side rather than at the corners.
That was deliberate. A church stood at the corner of Lexington and Fifty-Fourth, so the fifty-nine-story tower was cantilevered over it.
William LeMessurier was the structural engineer behind it. At completion, the building was the seventh tallest in the world.
In June 1978, a student working on a thesis about the tower called his office with a question about those columns. The question was whether a building braced that way could take wind striking it on the diagonal.
LeMessurier explained why the design held. Then he went back and checked it.
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Around the same time, on a separate project, a contractor questioned what it would cost to weld the joints of a braced frame. LeMessurier asked his own office what had been done at Citicorp.
The chevron braces there had been bolted, not welded. Bethlehem Steel had proposed the change to save money, and his office had approved it without telling him.
He recalculated in late July. Wind hitting the tower at forty-five degrees raised the load on some braces by forty percent.
At the bolted joints, the increase was one hundred sixty percent.
Welded joints would have carried it. Bolted joints would not.
He worked out how strong a storm would have to be to reach that threshold, and how often New York gets one. The answer was roughly once every sixteen years.
The building was a year old and full of tenants. The weakest joints sat on the thirteenth floor, behind drywall, in a structure no code in the city required anyone to check for diagonal wind.
No inspector was going to find it. Nobody was ever going to ask.
LeMessurier called his lawyer, then his insurers, then the architect, then Citicorp. He told the bank that the tower he had designed could come down in a hurricane.
Citicorp agreed to repair it.
The work was code-named Project SERENE. Welders arrived after the offices emptied, cut through the drywall, and laid steel plates over two hundred bolted joints.
They worked nights from August into October 1978. Weather forecasts came three times a day, and the Red Cross prepared a plan to evacuate the surrounding blocks.
In early September, with the retrofit roughly half finished, Hurricane Ella tracked up the eastern seaboard toward New York. It turned out to sea.
The welding was completed in October. The rebuilt frame was rated to stand through a storm of a size expected once in seven hundred years.
A newspaper strike in the city kept the work quiet. The public learned none of it until Joe Morgenstern published the account in The New Yorker in 1995.
The bolts were chosen because they were cheaper than welds. Undoing that saving cost millions, and the one man positioned to bury the problem instead reported it to his own insurers before anyone could compel him to.
If the flaw were sealed inside a wall where no inspection would ever reach it, and you were the only man who knew, would you make the call?