St.-Francis-Talsperre

The St. Francis Dam was a curved concrete gravity dam, built to create a large regulating and storage reservoir for the city of Los Angeles, California. The reservoir was an integral part of the city's Los Angeles Aqueduct water supply infrastructure. It was located in San Francisquito Canyon of the Sierra Pelona Mountains, about northwest of Downtown Los Angeles, and approximately north of the present day city of Santa Clarita.The dam was designed and built between 1924 and 1926 by the Los Angeles Department of Water and Power, then named the Bureau of Water Works and Supply. The department was under the direction of its General Manager and Chief Engineer, William Mulholland.At 11:57 p.m. on March 12, 1928, the dam catastrophically failed, and the resulting flood took the lives of an estimated 431 people. The collapse of the St. Francis Dam is considered to be one of the worst American civil engineering disasters of the 20th century and remains the second-greatest loss of life in California's history, after the 1906 San Francisco earthquake and fire. The disaster marked the end of Mulholland's career.Planning and designIn the early years of Los Angeles, the city's water supply was obtained from the Los Angeles River. This was accomplished by diverting water from the river through a series of ditches called zanjas. At that time a private water company, the Los Angeles City Water Company, leased the city's waterworks and provided water to the city. Hired in 1878 as a zanjero (ditch tender), William Mulholland proved to be a brilliant employee who after doing his day's work would study textbooks on mathematics, hydraulics and geology, and taught himself engineering and geology. Mulholland quickly moved up the ranks of the Water Company and was promoted to Superintendent in 1886.