St Francis Dam Failure, 12 March 1928.  Failed catastrophically upon its first full filling, near midnight, killing at least 450 people.  Seepage (dirty water)  was observed the day of the failure. A massive landslide occurred in the dams left abutment, comprised of schist.

“Greatest American civil engineering failure in the 20th century.”

Historical Society of Southern California:  St. Francis Dam Disaster.

Excellent Photo Display at:  St. Francis Dam collapse – Framework – Photos and Video – Visual Storytelling from the Los Angeles Times.

Type: Concrete Gravity Thick Arch Dam, Maximum Height = 195 feet, Storage (at time of failure) = 38,000 acre-feet