The St. Francis Dam seemed like such a good idea at the time. It was intended to serve as a reservoir for the Los Angeles Aqueduct, which provided fresh water to city residents who hadn’t quite noticed that they’re living in a desert. The liquid comes from a full 233 miles away, and engineers figured a reservoir would help safeguard against future droughts should the canals ever be damaged by earthquakes. The city was growing rapidly, so it made sound financial sense to prepare for worst-case scenarios.
Unfortunately, the dam would be a worst-case scenario. It was designed by William Mulholland, a self-taught engineer who had risen up through the ranks of the Bureau of Water Works and Supply. He seemed like a natural choice, being renowned for his economic restraint (cheapness), and ability to finish projects on time (he shouted at people a lot.) Mulholland decided to place the dam in the middle of the San Fransquito canyon, and decided to add about ten feet to the top of the structure for no particular reason.
Shortly after the massive dam was completed, numerous cracks began to appear in the side of the barrier. Some of them sprung sizeable leaks, pouring a continuous dredge of muddy water into the reservoir. Mulholland took a trip out to the dam and investigated the visible deterioration, but dismissed the breaches as normal. It is unknown if he dismissed the Grim Reaper rubbing his hands together fiendishly at the nearby flow station as well.
On March 12, 1928, the St. Francis dam broke. Twelve billion gallons of water immediately rushed through the base of the canyon, washing away homes, vehicles, and the local hydroelectric plant. The flood continued south to decimate the town of Castaic Junction, and then pushed through the cities of Fillmore and Bardsdale before rolling through Ventura County and finally plunging its soaked and battered contents into the Pacific Ocean. At that point, the deluge was nearly two miles wide; that’s the size of thirty-five football fields.
The source of the calamity was later determined to be due to three factors: the instability of the surface rock (known, quite literally, as paleomegalandslide), the mistake of not addressing the additional height that was added to the dam, and the fact that Mulholland was pretty stupid. More than 600 people lost their lives to the catastrophe, which would later become known as the worst U.S. engineering failure of the 20th century.