limited the system's flexibility. During the dry summer months when surface water was frequently unavailable, farmers pumped vast volumes of groundwater to irrigate their crops, considerably depleting the regional aquifer. The Bureau of Reclamation recognized the need for a large storage reservoir in order to provide a year-round water supply, and began studies for this project in 1955. During the 1950s the State of California also began building its own water project, whose design also required an off-stream water storage reservoir. The state approached the federal government with an offer to design a joint-use facility; however it took several years for the Bureau of Reclamation to agree to the proposal. On May 16, 1960, the state and the Bureau of Reclamation signed a "coordinated operation" agreement which laid out plans for the construction of joint-use facilities, including the San Luis Dam and Power Plant. The state government was to cover 55 percent of the cost with the federal government providing the rest. On June 3, 1960, President Dwight D. Eisenhower signed an act authorizing the San Luis Unit Project. Plans for the dam were completed by 1961 and the groundbreaking ceremony took place on August 18, 1962. In front of a crowd of 15,000 people, President John F. Kennedy and California Governor Pat Brown gave the signal to detonate the first explosive charges in the San Luis dam site. Work began the same month to reroute Pacheco Pass Highway (today's SR 152) around the future reservoir basin. The primary contract for the dam itself was awarded to Morrison-Knudsen, Utah Construction & Mining Co., and Brown & Root in 1963 for $85.9 million. Alfred M. Petrofsky held the role of chief engineer. Construction of San Luis Dam lasted from 1963 to early 1968. The dam was constructed in several zones with quarried local earth and rock averaging as much as per day. The 100-ton Caterpillar dump trucks used during construction were, at the time, the largest in the US. The construction of the four water intake towers, each high, involved the first use of tower cranes in the US. The work force peaked at 2,304 in October 1965 and declined thereafter; in January 1968, with construction almost completed, the first water was delivered through the California Aqueduct to begin filling the giant reservoir. The dam was officially dedicated on April 20, 1968, by Secretary of the Interior Stewart L. Udall. On