Construction of the Dam

Construction of the Dam. Saint Francis Dam Disaster National Memorial and National Monument. , , Problems With Design , , Too Tall , Final design was 20 ft higher than the original plan, without increasing the base width to support the additional height. , , Hydraulic Uplift , The design did not include enough design features to account for uplifting pressure beneath the structure due to buoyancy. , , No Contraction Joints , Contraction joints are grooves in concrete structures purposefully created during construction to control the location of cracks as the concrete dries. , , Processes Not In Place at the Time , , No External Review , Mulholland had his own staff perform all the engineering calculations without external review. , , Concrete Missteps , The aggregate for the concrete was neither washed nor sorted to remove unwanted substances like silt or clay, which reduce the quality. , , Poor Site Location , The dam was partially built on an ancient landslide, which shifted under the massive weight of the dam. , , June 1923 · Preliminary surveys of the dam construction site are completed. , April 1924 · Construction of the St. Francis Dam begins. , August 1924 · First concrete poured for footing of dam. , March 1926 · Reservoir began to fill with water. , March 12, 1928 · St. Francis Dam Failure. , , Gravity Dams , Gravity dams are freshwater-retaining structures designed to hold back water by using only the weight of the dam. It has a wider base than the top section with the purpose of maintaining a low center of gravity. , , Did You Know? , , During Construction , The St. Francis Dam utilized its own concrete plant, where aggregate (sand and gravel) sourced from the San Francisquito Creek bed was incorporated with Portland cement. , , Mulholland Dam , The St. Francis Dam is an adaptation of the Mulholland Dam, which was completed in 1924 in the Hollywood Hills of Los Angeles. The two were nearly identical, but the Mulholland Dam underwent major review and retrofit by the mid-1930s after the St. Francis Dam failure. , , Hoover Dam , The Hoover Dam was modeled after the same design as the St. Francis Dam. The failure of the St. Francis Dam instigated a review of the Hoover Dam's design and construction plans by a board of engineers, delaying the construction of Hoover Dam.