The Great Molasses Spill

In early 1919 there was an industrial accident that will go down in history as the stickiest accident in history. This was the great molasses flood in Boston. The spill was the result of a tank failure in the north end of Boston. 21 people were killed and over 150 injured.  The city was covered in sticky goo that to this day has not fully disappeared, having clogged up buried electrical conduits and other underground structures.

The tank ruptured and collapsed because the plates were too thin to prevent buckling and when the failure did occur the collapse was massive and fast, with molasses flowing at some 35 miles an hour.

The tank that collapsed was a buffering tank for the Purity Distilling Company, a manufacturer of industrial alcohol which had a plant in Cambridge and transferred the molasses from the tank to the smaller tank at the plant. The day the accident happened, the tank nearly full. Here’s a bunch of links about the accident.

97 Years Ago: The Great Molasses Flood Killed 21 People in Boston’s North End

A group of students looked at how the molasses could behave the way it did. First of all it was a warm day in January and a fresh load had just been added to the almost full tank. Second. due to the weakness of the tank’s construction, once the failure started the rupture caused by the weight of the molasses caused the entire bottom of the tank to fail.  Third once the failure happened there was nothing to stop the molasses from flowing very quickly even as it cooled.


The great molasses flood was one of the most unusual industrial accidents of all time.  It also led to greater controls over tank construction and safety additions. This seems to be the pattern with industrial and structural accidents.  Much regulation is surprisingly, or maybe not so surprisingly, driven by the insurance industry. More than likely that’s because insurance is the industry that assumes the risks that others take and mitigating those risks is represents money in the insurance company’s pockets.  So professional organizations like the American Society of Mechanical Engineers and the standards surrounding things like pressure vessels and storage tanks is driven by the insurance companies being prepared to deny insurance if the standards are not met. Still there’s no stopping people from being stupid and thinking that they can cut corners without possibly getting people killed.  All too often they are proven wrong.

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