Dam Failure Case Study: St. Francis Dam (California, 1928)

DamFailures.Org is an ASDSO project that provides individual dam failure case studies and lessons learned as a resource for dam safety engineers, dam operators, owners, regulators, managers, academia and students to help prevent future incidents.

Located approximately forty miles northwest of Los Angeles, California, St. Francis Dam was a curved concrete gravity dam constructed between 1924 and 1926 in order to provide a storage reservoir for the Los Angeles Aqueduct system. It was only the second concrete dam of nine dams built by the Los Angeles Bureau of Waterworks & Supply starting in 1921. While the dam’s upstream face exhibited a nearly vertical profile, the downstream side was equipped with a stair step design that resulted in base and crest thicknesses of 175 and 16 feet, respectively. The main structure reached a height of 205 feet and spanned 700 feet along its curvilinear crest. The design and construction of the St. Francis Dam was executed solely by the Los Angeles Bureau of Waterworks & Supply under the supervision of the organization’s chief engineer William Mulholland. The 1928 failure of the dam which resulted in the deaths of over 400 civilians was attributed to a series of human errors and poor engineering judgment. Due to the tremendous loss of life and property damage estimated to be $7 million, some consider the failure of the St. Francis Dam to be the “worst American civil engineering disaster of the 20th century.”