St. Francis Dam - Analysis

Analysis

Modern geologists know that the types of rock formations similar to that found in San Francisquito Canyon may be unsuitable for supporting a dam and reservoir without special consideration given to their design, but in the 1920s, two of the world's leading geologists at the time, John C. Branner of Stanford University and Carl E. Grunsky, found no fault with the San Francisquito rock. The dam was also built squarely over the San Francisquito fault, although this fault is inactive.

J. David Rogers, a professor of geological engineering at Missouri University of Science and Technology, published a comprehensive account of geologic actions which likely led to the dam's failure. He attributed the failure to three major factors: the instability of the ancient landslide material on which the dam was built, the failure to compensate for the additional height added to the dam's design, and the design and construction being overseen by only one person.

A critique of Rogers' historical analysis of the dam's collapse was published in the journal California History in 2004 by historians Norris Hundley Jr. (Professor Emeritus, UCLA) and Donald C. Jackson (Professor, Lafayette College). While accepting most of Rogers' geological analysis of the failure, the article makes clear how the structure built under Mulholland's direction in San Francisquito Canyon fell somewhat short of the standards for large-scale concrete gravity dams as practiced by other prominent dam engineers in the 1920s.