On January 15, 1919, in the North End neighborhood of Boston, Massachusetts, a large storage tank owned by the Purity Brewing Company filed with 2.3 million gallons of molasses weighing approximately 12,000 tons burst. As a result, a wave of molasses rushed through the streets at an estimated 35 miles per hour, killing 21 people and injuring another 150.
Like many other tragic disasters, this one was entirely preventable. As is often the case, no single decision of factor alone was responsible for the catastrophe that left Boston smelling like molasses on hot summer days for decades.
A look at the circumstances leading up to the flood reveals that leaders at Purity Brewing Company made the same kinds of mistakes common in organizations today.
The Purity Distilling Company had two good reasons for building an enormous storage tank for molasses. Molasses can be fermented to produce ethanol, a key ingredient in both alcoholic beverages and munitions. Demand for both was enormous. World War I increased the need for commercial alcohol, and prohibition was coming. (The 18th amendment was passed the very next day after the accident.)
Built hastily in 1915, the tank was 50 feet tall and 90 feet in diameter. There were problems from the beginning. The container started to groan when operators added new molasses, and the paint began to peel, and it often leaked molasses onto the street. The problem was so well known that families came to the site to fill bottles with molasses to take home for personal use, and children captured the sweet liquid to make their own candy.
Although Purity had poured molasses into the container 29 times, only four of those refills reached near-capacity. The fourth happened two days before the disaster when a ship arrived from Puerto Rico carrying 2.3 million gallons of molasses. At that point, the tank held enough molasses to fill three and a half Olympic-sized swimming pools.
On January 15, 1919, the temperature rose above 40 °F, unusual for a Boston winter and much warmer than the previous days' frigid temperatures. The fresh shipment of molasses was warmed to lower its viscosity for transfer. Likely due to the older cold molasses' thermal expansion, the tank burst at approximately 12:30 pm.
The collapse resulted in a 25-foot high wave of molasses moving at 35 miles per hour. The force was sufficient that the Boston Globe reported that the molasses wave caused buildings to "cringe up as though they were made of pasteboard."
While there was some initial speculation that a bomb had caused the explosion, modern analysis supports the conclusion that the incident resulted from thermodynamics and a series of bad decisions. There is benefit for today's leaders in thinking about how your organization may be making similar mistakes.
When Purity first put the tank into use, engineers recommended filling it first with saltwater to ensure there were no leaks and that the tank would hold up under pressure. This advice was ignored due to the extra cost and time it would take.
The tank leaked almost from the beginning; rather than looking for the root cause of this problem or trying to eliminate the resulting waste, management at Purity calculated that the wasted molasses did not outweigh the expense of solving the problem. Instead of fixing the leaks, they painted the tower brown to make the problem less apparent. Visualization is a powerful tool, but it works both ways. It can either highlight issues or cover them up.
In 2014, an investigation applied modern engineering analysis and found that the steel was half as thick as it should have been for a tank of its size, even with the lax standards of the day. The tank also lacked manganese and was made more brittle as a result. On top of that, the tank's rivets were also apparently flawed—the first cracks formed at the rivet holes.
Mark Rossow is a civil engineer and professor emeritus at Southern Illinois University in Edwardsville, who has written about the molasses flood. He writes that "When a laborer brought actual shards of steel from the tank's walls into the treasurer's office as evidence of the potential danger, he replied, 'I don't know what you want me to do. The tank still stands."
Speaking of the treasurer, the tank project was overseen by Arthur Jell, USIA's treasurer. He had no architectural or engineering experience. Financial concerns were prioritized over technical and safety ones. The results speak for themselves.
Following the disaster, the victims filed 119 lawsuits against Purity's parent company, United States Industrial Alcohol. The cases against USIA were eventually combined into a massive legal proceeding that went on for five years. in April 1925, state auditor Hugh W. Ogden finally ruled that United States Industrial Alcohol was responsible for the disaster. He concluded that the company's poor planning and lack of oversight had led to the tank's failure. USIA was ordered to pay the flood victims and their family members $628,000 in damages—the equivalent of around $8 million today.
I'd be surprised if any readers of this blog have 2.3 million gallons worth of molasses to store, but there are lessons to be gleaned from this disaster nonetheless. Listening to employees and experts, addressing small problems at the root cause, and insisting on quality materials can help you avoid a situation that spirals out of control.