Building the Hoover Dam Reading Answers

Building the Hoover Dam

On July 7th 1930, the construction of the Hoover Dam began. Over the next five years, a total of twenty-one thousand men would work ceaselessly to produce what would be the largest dam, as well as one of the largest man-made structures of its time. Although the dam would take only five years to build, its construction was nearly thirty years in the making. Arthur Powell Davis, an engineer from the Bureau of Reclamation, originally drew up his engineering report for the Hoover Dam back in 1902, and it was this that was the basis of the construction project, when plans were finally made to begin the dam in 1922.

Herbert Hoover, the 31st president of the United States and a committed conservationist, played a crucial role in making Davis' vision a reality. As secretary of commerce in 1921, Hoover devoted himself to what would become the Hoover Dam in Boulder Canyon, Colorado. The dam would supply flood control, which would prevent damage to downstream farming communities that suffered each year when snow from the Rocky Mountains melted and joined the Colorado River.

The dam would allow better farming opportunities with the expansion of irrigation in the desert, and it would also provide a supply of water and electricity for the city of Los

Angeles and other towns of southern California. The Boulder Dam generates, on average, 4 billion kilowatt-hours of hydroelectric power each year for use in Nevada, Arizona, and California - enough to serve 1.3 million people. From 1939 to 1949, the Boulder] Powerplant was the world's largest hydroelectric installation and today it is still one of the largest in the US.

Even with Hoover's backing and a regional consensus regarding the need to build the dam, congressional approval and individual state cooperation were slow in coming. For many years, Colorado River water rights had been a source of contention among the western states bordering it. To address this issue, Hoover negotiated the Colorado River Compact, which broke the river basin into two regions.

Hoover then had to introduce and re-introduce the bill to build the dam several times over the next few years, before the House and Senate finally approved it in 1928. Once negotiations and preparations were made, the Hoover Dam's construction went forward quickly. The contractors finished their work two years ahead of schedule and millions of dollars under budget.

Just before the onset of building, the dam location was shifted from Boulder Canyon to

Black Canyon. The United States' Great Depression ensured that there were plenty of men in need of work, who would come to this desolate, wild, and hot area to earn a living. Arriving with families, a tent community was born. No electricity, an average temperature of 119 degrees Fahrenheit (48 degrees Celsius) during the day, poor sanitary conditions and poor water set the stage for communities known as "Ragtowns."

In order to improve their quality of life and to save people from disease, electricity came to the area and Boulder City was established. A school, church, post office and other supporting facilities were created for the families. Before the dam construction could begin, the Colorado river needed to be re-routed through tunnels. This would allow the water to bypass the dam foundation site and later on to be used for the electric plant generators. Building tunnels directly through the canyon rock walls required dynamite, rock removal and structure for support to be built.

Great hazards were created in the tunnels. The use of machines could cause carbon monoxide poisoning and, of course, there was the blasting and drilling in the rock, which was also dangerous work. Once the first two tunnels were in place, cofferdams were built to divert the Colorado River. These two cofferdams were constructed in order to isolate the construction site, and protect it from flooding. Before the cofferdams could be constructed, 250,000 cubic yards of river silt had to first be removed to provide a firm Foundation.

Construction of the upper cofferdam began in September, 1932, even though the river had not yet been completely surveyed. Work on the lower cofferdam was delayed because of flooding. The cofferdams were completed before the spring floods of 1933 and the engineers watched nervously the dams successfully holding back the water. This allowed the dam construction to begin.

As in any construction project, the dam's base was a major factor in building an enduring structure. This required the men to excavate the mud and muck at the river bottom. With the aid of power shovels, the men removed over half a million cubic yards to reach bedrock forty feet below. Simultaneously, the "high scalers" worked the canyon walls. Earning $5.60 a day, this was one of the highest paying jobs at the site. These men would blast the walls to create a smooth joining surface for the dam.

The hydroelectric system had to be included within the structure of the dam. For efficient use for power generation, the intake had to be as far above the turbines as possible (a high 'head'). The water intake at the Boulder Dam comes in through filters half way down the dam's wall. The water flows down through a waterway known as the penstock, until it comes into contact with the turbines.

The water then flows down pipes to the bottom of the dam, where it rejoins the river. The turbines rotate long steel poles that go up to the generator, where the turning creates the magnetic field, which in turn generates electricity. The electricity leaves the generator and goes to a substation, before being carried by power lines to its places of use.