Comparable to a 60-story building with a base is as thick as two football fields are long, the Hoover Dam was regarded as the highest dam in the world when it was completely built in 1935. With both spillways designed to let floodwaters pass through without damaging the dam, each can handle the voluminous water that flows over Niagara Falls. Also, the amount of concrete that was used in building it was definitely enough to pave a road from San Francisco extending to New York City.
Supposedly, it would only take five years to build the dam, but its construction was nearly 30 years in the making. The engineer from the Bureau of Reclamation who originally had his concept for the dam back in 1902 was Arthur Powell Davis. His engineering documents on the topic became the guide when finally in 1922, construction of the Hoover Dam began.
Construction of the Hoover Dam was between 1931 and 1936 during the Great Depression and was dedicated on September 30, 1935, by President Franklin D. Roosevelt.
An inspection party close to the proposed site of the dam in the Black Canyon on the Colorado River. 1928.
Four tons of dynamite were used to detonate in the canyon in the early stages of construction. May 12, 1933.
Soon after the construction was authorized, a growing number of unemployed people converged on southern Nevada. Las Vegas was then a small city of some 5,000, saw between 10,000 and 20,000 unemployed descend on it. 1933.
Two cofferdams were created to protect the construction site from the Colorado River and also to facilitate the river’s diversion. Work on the upper cofferdam started in September 1932, even though the river had not yet been diverted. 1933.
The cleared, underlying rock foundation of the dam site was reinforced with a grout curtain. Holes as deep as 150 feet (46 m) were driven into the walls as well as the base of the canyon and into the rock, and any cavities sse
were to be filled with grout. This was done to stabilize the rock. 1933.
Jackhammers were used by “High scalers” to shave loose rock off the walls of Black Canyon. 1935.
“High scalers” are rappelling down the canyon wall. 1934.
The concrete foundation of the dam is drained into separate blocks which are called “lifts”. September 11, 1933.
Seeing that concrete heats and contracts as it cures, the probability for the concrete's uneven cooling and contraction poses a serious problem. Bureau of Reclamation engineers reckon that if the dam was constructed in a single continuous pour, the concrete would probably take 125 years to cool, and the effect would cause the dam to eventually crack and crumble. Alternatively, the ground where the dam would erect was marked with rectangles, and then concrete blocks in columns were poured, some of these were as large as 50 ft square (15 m) and 5 feet (1.5 m) high.
The 31st president of the United States and also a committed conservationist, Herbert Hoover, played an important role in making Davis’ vision a reality. In 1921, when Hoover was the secretary of commerce, he devoted himself to the rise of a high dam in Boulder Canyon, Colorado. The dam was envisioned to provide essential flood control, preventing damage to downstream farming communities which are suffering each year whenever the snow from the Rocky Mountains melted to join the Colorado River. Moreover, it would also allow the expansion of irrigated farming within the desert, and would give a dependable supply of water for Los Angeles as well as other southern California communities. By 1929, as the president, Hoover signed the Colorado River Compact into law. He claims it was “the most extensive action ever taken by a group of states under the provisions of the Constitution permitting compacts between states”.
The cooling pipes were later back-filled with concrete to add strength. As this is an arch-gravity dam, it is common that the massive water pressure reaching 45,000 lbs per square foot at the base of Hoover Dam is controlled by gravity. The arch-curved framework against the lake reservoir expend that pressure into the canyon walls evenly on the Arizona and Nevada side.
With the construction of the dam, 112 deaths transpired. The first casualty occurred December 20, 1922 when J. G. Tierney, a surveyor, drowned while looking for a fitting spot for the dam. The last fatality on the official list took place on December 20, 1935, when an “electrician’s helper”, Patrick Tierney, fell from an intake tower. He was the son of J. G. Tierney. Listed as well were three workers who committed suicide onsite, one in 1932 and two during 1933. Ninety-six of the deaths ensued on site while the construction was ongoing. Among the 112 fatalities, 91 of them were Six Companies employees, three of which were BOR employees, and one visitor to the site, with the remainder employees of different contractors not part of Six Companies.
The concrete was conveyed in huge steel buckets 7 feet high (2.1 m) and almost 7 feet in diameter.
Officials hitch a ride in one of the penstock pipes of the soon-to-be-completed Hoover Dam. 1935.
A total of 3,250,000 cubic yards (2,480,000 m3) of concrete was utilized in the dam before concrete pouring ceased on May 29, 1935.
In 1995, concrete cores were extracted from the dam for testing; they showed that “Hoover Dam’s concrete has slowly progressed to "gain strength” and the dam consists of a “durable concrete having a compressive strength exceeding the range typically found in normal mass concrete”.
The base of one of the intake towers which is under construction. 1934.
More than 582 miles (937 km) of cooling pipes were settled within the concrete. 1934.
Water flowing over the spillways falls effectively into 600-foot-long (180 m), 50-foot-wide (15 m) spillway tunnels before linking to the outer diversion tunnels, and then reentering the main river channel under the dam. 1934.
Progress done in 1934.
Student engineers stand on one of the 2 million-pound hydroelectric generators for the Hoover dam at the General Electric factory in Schenectady, New York. 1935.
Construction on the dam continues day and night. February 25, 1934.
Workers are applying a coat of paint to one of the dam’s spillways. 1936.
The dam nearly completed. 1935.
President Franklin D. Roosevelt in one of the tours at the site. 1935.
Kaufmann notably streamlined the design, then applied an elegant Art Deco pattern to the entire project. The layout included sculptured turrets rising smoothly from the dam face. The clock faces on the intake towers are set for the time in Nevada and Arizona — both states have different time zones, but Arizona does not observe Daylight Saving Time (DST), and so the clocks display the same time for more than half the year.