- Los Angeles County -

St. Francis Dam Collapse
March 12, 1928

Construction began on the St. Francis Dam, designed and constructed by Chief Engineer William Mulholland, on March 9, 1925, and was completed nearly one year later at a cost of $1,250,000. The huge concrete arched wall, which had been erected between the towering sides of the San Francisquito canyon at its narrows, stood 205 feet high above bedrock. The dam was 1225 feet wide at its crest, 150 feet wide at stream level and 160 feet thick at its base. From 170 feet at its base the solid concrete structure diminished in thickness until, at its crest, it was 16 feet through. Its purpose was to supply water to the growing population of Los Angeles. The reservoir created by the erection of the new dam would be three miles long and capable of holding in storage 38,000 acre feet or 12,000,000,000 (12 billion) gallons of water. That, however, was to be a short lived dream as the dam suffered a catastrophic failure two and 1/2 minutes before midnight on Monday, March 12, 1928, two years to the date when water first began to fill the reservoir.

Cracks began to appear in the dam as water began to fill the reservoir. William Mulholland and Harvey Van Norman, his general manager and assistant chief engineer, inpected the cracks and deemed them to be within expectations for a dam of this size. Towards the end of February, 1928, a notable leak was discovered which was inpsected by Mulholland who again deemed it to be another temperature or contraction crack. On the morning of March 12th a new leak was discovered in the west abutment by the dam keeper, Tony Harnischfeger, which caused him concern because of the muddy color of the runoff, which could mean that water was possibly eroding the dam's foundation. Mulholland and Van Norman were summoned and, after inspecting the leak, determined that some corrective measures did need to be taken, but could be done at a later date. Neither men considered the situation to be of a dangerous nature.

No one survived to tell exactly what happened at 11:58 p.m. on March 12, 1928, when the St. Francis Dam failed, emptying the reservoir behind within 70 minutes. Newspaper reports at the time stated that the wall of water was initially 140 feet in height leaving a path of devastating destruction from the dam, down the San Francisquito Canyon and Santa Clara River Valley through Ventura County before washing victims and debris into the Pacific ocean. An exact death toll can never be had as many victims were buried under mud and debris or washed out to sea, but it was claimed that more than 450 people died that night. The collapse of the St. Francis dam remains one of the worst civil engineering failures in American history and marked the end of William Mulholland's career.