Constructed between 1924 and 1926, the St. Francis Dam was a concrete gravity-arch dam designed to act as a reservoir to store water for the Los Angeles Aqueduct. In 1928, the dam catastrophically failed, and the resulting flood of 12 billion US gallons (45 billion liters) of water killed more than 450 people. The dam’s collapse was the worst American civil engineering failure of the 20th century and remains the second-greatest loss of life disaster in California’s history, after what event? Discuss