A GEOTECHNICAL DISASTER
ST. FRANCIS DAM
At three minutes before midnight March 12, 1928, the St. Francis dam catastrophically failed. Approximately 500 people lost their lives in the down stream towns along the Santa Francisquito Canyon and the Santa Clara Valley. Among those that died, were many of the workers and their families that labored at the dam.
It's designer and builder, Mr. William Mulholland, stated at the inquest, "I envy the dead." 1 At this time, Mr. William Mulholland, was the chief engineer for the Los Angeles Department of Water and Power. Among the many projects he was instrumental in building, are the Colorado Aqueduct, Hoover Dam, Panama Canal, and the Los Angeles Aqueduct. 2 He proposed, and designed the Los Angeles Aqueduct, bringing water from Owens Valley to Los Angeles. Partially due to the controversy and threats that had developed from this project, the St. Francis dam was proposed as an additional water supply for the city of Los Angeles. It would have provided some 38,000 acre-feet of storage (12,000,000,000 gallons) that could be used if the Owens Valley water flow was interrupted.
The dam was a curved concrete gravity dam, approximately 600 feet long, and 180-200 feet high. It was constructed between 1926 and 1928, at a time when engineers were pushing the limits of technology both on the engineering and geotechnical aspects of dam building. Following the disaster, several investigations were conducted. The most cited, the "blue book report" was based on one site visit, with the report being published five days later. 3 (This must be a record for a governmental investigation!) The ‘blue book report’ concluded that the dam’s failure was due building the right abutment on the fault contact between the Sespe conglomerate and the Pelona Schist. Recent reevaluation suggests that the design did not take in proper account the uplift theory; the dam’s base width was not as thick as previously assumed; the left abutment was on a ancient paleo mega-landslide and that the Sespe red beds would slake when submersed.3
From this disaster, the world’s first dam safety agency was formed; normalization of uniform engineering criteria for testing compacted earthen materials was established (which is still being used today); reevaluation of all Los Angeles Department of Water and Power dams and reservoirs; and the formation of state-mandated process for the arbitration of wrongful death suits (which also is still being used today)! 3
Prepared by Kelita Stephens, Dec., 1997, posted 1998
© Copyright Mete Oner, 1995-2006