St. Francis Dam (1928): Inspected 12 Hours Before It Broke

About twelve hours before the St. Francis Dam collapsed on the night of 12 March 1928, the chief engineer of the Los Angeles water bureau inspected a new leak and judged it harmless. Investigators traced the failure to the rock beneath the dam, a coroner's jury looked at how the dam was approved, and engineers still argue about where it broke first. The dam: a curved concrete gravity dam, 205 feet high, built 1924-1926 by the Los Angeles water bureau under chief engineer William Mulholland. Its own engineers designed it (inquest testimony), and a 1917 state law exempted cities with engineering departments from state oversight. The failure: about 11:58 p.m. on 12 March 1928. Roughly four hundred people were dead or missing (estimates run from about 385 to 450; the often-quoted 432 is a minimum and omits migrant farm workers). The engineering: water seeping under a gravity dam (uplift) cancels part of its weight. Drains lay under the middle only, none under the sloping sides; the rock was schist on the east and a conglomerate on the west that turned to loose sand in water. Rogers and ASDSO report two ten-foot raisings without widening the base. The findings: the Governor's commission (24 March 1928) found "defective foundations". The coroner's jury (12 April 1928) found an error of engineering judgment (the water bureau and its chief engineer) and an error of public policy (city, state and public), and no criminal act. Mulholland told the inquest: "If there is an error of human judgment, I was the human." Where it broke first is still argued: the commission said the west end, Rogers the east abutment. What changed: the Dam Safety Act of 14 August 1929 gave the State Engineer authority over non-federal dams above 25 feet or 50 acre-feet and ended the exemption for cities. Chapters: 00:00 The chief engineer inspected a new leak 00:22 Three answers: rock, approval, where it broke 01:11 No outside body had to approve it 01:51 Raised twice, ten feet at a time 03:32 The rock: schist and conglomerate 04:45 The leak, the muddy water, the inspection 05:33 That night: 11:58 p.m. 06:05 125 feet of water at the powerhouse 07:23 How many died? A count not settled 08:02 The Governor's commission: defective foundations 09:29 Where did it break first? 10:43 The coroner's inquest: "I was the human" 11:08 The verdict: two errors, no criminal act 12:04 August 1929: the city's exemption ends 13:39 Why someone else has to check Sources: Report of the Commission Appointed by Governor C. C. Young to Investigate the Causes Leading to the Failure of the St. Francis Dam (State of California, 24 March 1928) Verdict of the Coroner's Jury in the St. Francis Dam Inquisition, 12 April 1928 Coroner's inquest transcript, 21 March-10 April 1928 (Mulholland, Van Norman; parts read, the rest as quoted by Pollack, Rippens and Rogers) J. David Rogers, "The 1928 St. Francis Dam Failure and Its Impact on American Civil Engineering" Marilyn A. Dyrud, "The Limits of Professional Autonomy: William Mulholland and the St. Francis Dam" (2013) ASDSO, Dam Failures and Lessons Learned: "St. Francis Dam (California, 1928)" Alan Pollack, "St. Francis Dam: Too Big Not to Fail" (2010); Paul H. Rippens, "The Night of the Flood" (1998) Lafayette College News (2017) on Jackson and Hundley, Heavy Ground (2015); Geo-Institute of ASCE, "Jazz Age Geotechnical Engineering, Part 6" California DWR, "History of California Dam Safety" (1929 Dam Safety Act), with Rogers Photo credits: Via Wikimedia Commons, Creative Commons: "St. Francis dam" by Imveracity, CC BY-SA 4.0, commons.wikimedia.org/wiki/File:St._Francis_dam.jpg "Largest section of dam found downstream003" by Imveracity, CC BY-SA 4.0, commons.wikimedia.org/wiki/File:Largest_section_of_dam_found_downstream003.jpg "Pp2before" by SkyG702, CC BY-SA 4.0, commons.wikimedia.org/wiki/File:Pp2before.jpg "Pp2after" by SkyG702, CC BY-SA 4.0, commons.wikimedia.org/wiki/File:Pp2after.jpg "Twisted Tracks" by U.S. Geological Survey, CC BY 2.0, commons.wikimedia.org/wiki/File:Twisted_Tracks.jpg "Santa Paula, CA, St Francis Dam Disaster Memorial, 2012 - panoramio" by Chris English, CC BY-SA 3.0, commons.wikimedia.org/wiki/File:Santa_Paula,_CA,_St_Francis_Dam_Disaster_Memorial,_2012_-_panoramio.jpg "Saint Francis Dam Ruins Looking Southwest 2006" by Doc Searls, CC BY 2.0, commons.wikimedia.org/wiki/File:Saint_Francis_Dam_Ruins_Looking_Southwest_2006.jpg "Saint Francis Dam Site 2012" by Chevy111, CC BY-SA 4.0, commons.wikimedia.org/wiki/File:Saint_Francis_Dam_Site_2012.jpg Other archival photographs: public domain (USGS, National Archives, Library of Congress, 1928 Commission report).