St. Francis Dam

* The St. Francis Dam was a concrete gravity dam located in San Francisquito Canyon in Los Angeles County, California, United States, built from 1924 to 1926 to serve Los Angeles’s growing water needs. It catastrophically failed in 1928 due to a defective soil foundation and design flaws, triggering a flood that claimed the lives of at least 431 people. The collapse of the dam is considered to be one of the worst American civil engineering disasters of the 20th century in California’s history.

* The dam was designed and built by the Los Angeles Department of water and power. The department was under the direction of general manager and chief engineer, Willliam Mulholland. Mulholland was a brilliant employee who after doing his day’s work, would study textbooks on mathematics, hydraulics and geology and taught himself geology and engineering.

* Mulholland achieved great recognition among members of the engineering community when he supervised the design and construction of the Los Angeles Aqueduct, which at the time was the longest aqueduct in the world. It used gravity alone to bring the water 233 miles from the Owens Valley to Los Angeles. The project was completed in 1913, on time and under budget.

* It was during the process of building the aqueduct that Mulholland first considered sections of San Francisquito Canyon as a potential dam site. In particular, he favored an area with what he perceived as favorable topography. When the dam started to leak, Mulholland was asked to come out to the dam and evaluate the situation. When he arrived at the dam the leaks were significant to the untrained observer. Mulholland’s assessment was that “the leaks were normal for this type of dam !”.

* After the failure, an investigating committee ended their report with, …”having examined all the evidence which has been able to obtain, reports its conclusions as follows:

1. The type and dimensions of the dam were amply sufficient if based on suitable foundation.

2. The concrete of which the dam was built was of ample strength to resist the stresses to which it would normally be subjected.

3. The failure cannot be laid to movement of the earth’s crust.

4. The dam failed as a result of defective foundations.

5. The failure reflects in no way the stability of a well designed gravity dam properly founded on suitable bedrock.”.

* The disaster effectively ended Mulholland’s career. He lived in seclusion for the rest of his life.



* Which supports and barriers were in play?

* What were the dynamics?

* Who, or what, won the Tug-of-War?

* Discuss the outcome with your friends and family.

* Use Post #4 as a reference for the dynamics, and the relationships, between supports and barriers.