Causes
Local residents brought a class-action lawsuit, one of the first held in Massachusetts, against the United States Industrial Alcohol Company (USIA), which had bought Purity Distilling in 1917. In spite of the company's attempts to claim that the tank had been blown up by anarchists (because some of the alcohol produced was to be used in making munitions), a court-appointed auditor found USIA responsible after three years of hearings. United States Industrial Alcohol Company ultimately paid out $600,000 in out-of-court settlements (at least $10.7 million in 2012 dollars).
Several factors that occurred on that day and the previous days might have contributed to the disaster. The tank was constructed poorly and tested insufficiently. Due to fermentation occurring within the tank, carbon dioxide production might have raised the internal pressure. The rise in local temperatures that occurred over the previous day also would have assisted in building this pressure. Records show that the air temperature rose from 2°F to 41°F (from −17°C to 5°C) over that period. The failure occurred from a manhole cover near the base of the tank, and it is possible that a fatigue crack there grew to the point of criticality. The hoop stress is greatest near the base of a filled cylindrical tank. The tank had been filled to capacity only eight times since it was built a few years previously, putting the walls under an intermittent, cyclical load.
An inquiry after the disaster revealed that Arthur Jell, who oversaw the construction, neglected basic safety tests, such as filling the tank with water to check for leaks. When filled with molasses, the tank leaked so badly that it was painted brown to hide the leaks. Local residents collected leaked molasses for their homes.
An urban legend claims that the doomed tank might have been overfilled in late 1918 so that the owners could produce as much rum as possible before Prohibition came into effect. However, Purity Distilling did not make rum, but rather specialized in the production of industrial alcohol, which was exempt from the state prohibition laws in effect in 1919, and would later be exempted from the Volstead Act and other national Prohibition laws. While an urban legend, a 1999 television documentary, part of the Modern Marvels' Engineering Disasters sub-series, argued that—even if there was no specific plan to make alcohol to beat Prohibition—there may have been some general idea of increasing the volume at the last minute so as to prepare in case total alcohol prohibition might occur.
Read more about this topic: Boston Molasses Disaster