Construction of the Dam

Although construction actually began on the Hoover Dam in 1931, site testing for the project had begun early in the 1920's. The necessity of such a dam had been obvious for at least two decades, and the idea had been brought forth in administrations from Teddy Roosevelt on. The cycles of drought and flood in the American southwest incapacitated the growth of the agricultural industry; it was felt that a dam that could control the Colorado River would also provide hydroelectric power, eventually rendering the dam self-financing. The growth of Las Vegas and Southern California as major metropolitan centers also depended, to a large extent, on the availability of water and power.

When the Swing-Johnson bill detailing the Hoover Dam project passed in Congress in 1927, construction companies around the country began to look over the proposals. Most agreed that the plan was too ambitious, too difficult, the landscape was too unforgiving, and the technology not advanced enough to build a dam of that size. Still, in March of 1931 five bids were made on the project; Six Companies, Incorporated--a conglomeration of half a dozen smaller construction companies--won the job with a bid for $48,890,955, a figure only $24,000 over the Bureau of Reclamation estimate (Stevens, 46).

Because the dam site was so remote, the first job was to lay roads and railroad lines, and amass materials needed around the site. Men were hired on at the Six Companies office in Las Vegas, and the real work commenced. Much had to be accomplished before the concrete was poured. The Colorado River, most importantly, had to be diverted. Four diversion tunnels were cut over a period of a year through the bedrock of Black Canyon; when complete, these were lined with concrete. A temporary cofferdam was constructed which pushed the river into the diversion tunnels. Meanwhile, suspended high scalers laboriously chipped and shaved at the rock walls of the canyon, creating a smooth surface to which the dam's walls would adhere.

Following the diverion of the river, the floor of the canyon was dredged down to bedrock. Only then could the pouring of the concrete begin. A major problem with a structure as large as the Hoover Dam was the cooling of the concrete. Engineers calculated that the massive amount of concrete would take over one hundred years to cool; when cool the dam would crack, rendering it useless. To avoid this, the dam was poured in rows and columns of blocks. Refrigerated water was pumped through the blocks in pipes, and the pipes were then shot full of concrete, rendering the dam a true monolith--entirely one piece. The dam itself was completed two years ahead of schedule, in 1935. Power generation began in 1936 and turbines continued to be added until 1961, when the last one went on line (Bureau of Reclamation, 53-54).

Dedication Day crowds at the Hoover Dam,
September 30, 1935

The completion of the dam drew massive crowds for Dedication Day, September 30, 1935. Franklin D. Roosevelt delivered the address, calling the Hoover Dam "an engineering victory of the first order--another great achievement of American resourcefulness, skill, and determination."

 

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