Hoover Dam A MODERN MARVEL. Project Overview Why Build a Dam? Before the Hoover Dam was built, the Colorado River was dangerous and unpredictable. Towns.

Hoover DamA MODERN MARVEL

Project OverviewWhy Build a Dam?

• Before the Hoover Dam was built, the Colorado River was dangerous and unpredictable. • Towns and Farms were often flooded during the late spring and early Summer due to runoff from snow melting in

the mountains. • Flash floods could occur in any season. • By mid-summer, the Colorado River's flow was barely enough to provide irrigation to farms in Southern California

and Arizona.

The purpose of the Hoover Dam is to:• Prevent floods. • Make it easier to navigate the river • Store and deliver the river's water. • Generate electric power.

Project OverviewThe Colorado River Compact

• Before the Boulder Canyon Project Act could be passed, the seven states that the Colorado River flows through needed to agree on the allocation of water rights. • This agreement is called the Colorado River Compact. • The compact divided the river basin into two areas, the Upper Division and the Lower Division. • The bill was signed by President Calvin Coolidge on December 21st, 1928, authorizing the construction of the

Hoover Dam.

Project OverviewSix Companies

In order to secure the contract to build the Hoover Dam, a $2 million bid bond was required, as well as a $5 million performance bond. No one company had the resources to submit a bid, so eight companies joined together and pooled their resources to win the contract. They called themselves Six Companies, Inc.

They included:• Henry J. Kaiser Co. of Oakland, California and Bechtel Corporation of San Francisco (Bechtel-Kaiser)• MacDonald and Kahn of Los Angeles, California• Utah Construction Company of Ogden, Utah• Morrison-Knudsen of Boise, Idaho• Pacific Bridge Company of Portland, Oregon• J.F. Shea of Portland, Oregon

Six Companies won the contract in 1931, after a bid of $48,890,955. That would be $711,604,200 today. Their bid was $5 million less than the next bidder.

Members of Six Companies, Inc.

Project OverviewWhat Shall We Call It?

• The Hoover Dam was named after President Herbert Hoover on September 30th, 1930. • President Hoover was instrumental in deciding where the dam would be built, as well as securing power and

water contracts necessary to finance the project. • After President Hoover left office, the Department of Interior began referring to the Hoover Dam as the Boulder

Canyon Dam, or Boulder Dam. • Congress Passed a resolution to officially name it Hoover Dam, and it was signed by President Truman on

April 23rd, 1947.

President Hoover

Leading the WayLead Designers

John L. Savage, Chief Engineer and Raymond F. Walter, Chief Design Engineer, led the engineering team that prepared the plans and specifications for the Hoover Dam. They completed and printed the specifications for the dam in December 1930, six months ahead of schedule.

John L. Savage Raymond F. Walter

Leading the Way Project Managers

Work at the dam site was supervised by: • Walker R. Young, Construction Engineer for the Bureau of Reclamation.• Frank T. Crowe, General Superintendent for the Six Companies.

Also overseeing work at the construction site were: • Ralph Lowry, Field Engineer.• John C. Page, Office Engineer.

Walker R. Young Frank T. Crowe Ralph Lowry John C. Page

Rag Town

The economic collapse that began in 1929 drove desperate men, women, and children to Black Canyon in the hopes of getting a job building the Hoover Dam. Outside of Las Vegas, Nevada, people put up tents and shacks, and endured very harsh elements waiting for construction to begin. This location came to be known as "Rag Town".

Some compassionate Las Vegas residents took it upon themselves to help the people of Rag Town with food, but life did not improve much until work on the dam started, and Boulder City was constructed.

Boulder CityBoulder City was built on federal land near the dam location. It was completed in 1932, and continued to expand as construction went on and more workers were needed. It had large dormitories for single men, and cottages forfamilies. A huge mess hall served 6,000 meals a day to hungry workers and their families. For $1.50 a day, a worker received three all-you-can-eat meals a day.

Boulder City was not ideal though. There was no formal educational system, and a lack of health care. The federal government provided no funds to build schools, so Six Companies donated some money to build makeshift schoolhouses. Six Companies also built a hospital, but health care was only provided to workers. Their spouses and children had to fend for themselves.

No Small TaskInfrastructure

Before construction of the Hoover Dam could begin, infrastructure had to be built, and Colorado river needed to be diverted away from the construction site.

• Seven miles of 22-foot-wide highway from Boulder City to the dam site.

• 22.7 miles of railroad tracks from the Union Pacific main line in Las Vegas to Boulder City and another 10 miles fromBoulder City to the dam site.

• A 222 mile long power line from San Bernardino, California, to the dam site to supply electricity for construction.

No Small TaskHigh Scalers

Millions of years of erosion caused cracks in the canyon walls. All of the loose rock had to be removed before construction could begin. Men known as "high scalers" climbed down the canyon walls on ropes to drill bore holes and place explosives.

It was quite possibly the most physically demanding job. They were lowered down loaded with equipment and water jugs, and a 45 pound jackhammer was lowered down for them to use. The work was extremely dangerous due to the high possibility of being struck by falling objects.

No Small TaskTunnels

Four 56-foot in diameter tunnels were bored through Black canyon to divert the Colorado River, two on the Nevada side and two on the Arizona side. Jackhammers were used to bore holes into the rock for explosives, 500 drills were purchased for the project.

A structure called a "drilling jumbo" was built on the back of a 10 ton truck to speed up the process. The truck backed up to the rock and 24 to 30 drills bored the holes. The drilling jumbo allowed half of the rock face to be prepared for demolition. Afterward, the drilling jumbo moved to the other side and repeated the process. One ton of dynamite was used for every 14 feet of tunnel dug.

In March 1932, work started on lining the tunnels with concrete. Lining the tunnels started with the base, followed by the sides, and then the ceiling. The tunnels were completed that November, and are three feet thick. Earth and rock were then dumped into the river, forcing it into the tunnels. Water flowed freely through the tunnels for the next two years.

Picture of a Drilling Jumbo

No Small TaskCofferdams

Once the tunnels were competed, two cofferdams were built in Black Canyon to isolate the construction site and protect it from flooding. The upper cofferdam was 98 feet tall, 450 feet long, and 750 feet thick at its base. The lower cofferdam was 66 feet tall, 350 feet long, and 550 feet thick at its base. After the cofferdams were completed, two of the tunnels were plugged with concrete 400 feet thick. Another was plugged, but had four six-foot diameter holes left In and fitted with gate valves. The last tunnel was fitted with a 1,000 ton steel gate.

Dam Construction

• A concrete plant was built 3/4 of a mile upriver from the dam site. • The first concrete was poured into the dam on June 6th, 1933. • Electric trains brought cars with large buckets of concrete, and then the

buckets were lifted from the cars and lowered in place by an overhead cable system.

• Nine of the cable ways were used to place the concrete, with some attached to movable towers that allowed them to work on different parts of the dam.

• An automatic concrete plant was constructed on the canyon rim as the dam got taller.

Dam Construction Continued

• The Hoover Dam was built with interlocking concrete blocks that connected to each other like Lego pieces.

• An estimated 215 blocks were used to complete the construction. • Steel pipe was placed inside the blocks, and river water was circulated

through it to cool off the concrete as it set. • The block joints and steel pipes were then sealed with grout to prevent

cracks and leaks. • A total of 21,000 men worked on the dam with an average of 3,500 and

a maximum of 5,218 daily, which occurred in June 1934. • The average monthly payroll was $500,000. • It is estimated that 96 workers died building the dam, but non were

buried in the concrete. • Hoover Dam was completed two years ahead of schedule on May 29th,

1935.

Hoover Dam Construction Time Lapse

Building Materials

• Cement - More than 5,000,000 barrels.• Reinforcement steel - 45,000,000 lbs.• Gates and valves - 21,670,000 lbs.• Plate steel and outlet pipes - 88,000,000 lbs.• Pipe and fittings - 6,700,000 lbs.• Structural steel - 18,000,000 lbs.• Miscellaneous metal work - 5,300,000 lbs.

Setbacks

Strike!Working conditions were very difficult and dangerous for the construction workers building the dam. • Carbon monoxide poisoning.• Dehydration.• Heat stroke.• Electrocution from poorly placed electrical lines were common.

The workers reached a breaking point in the summer of 1931. On August 7th, Six Companies reassigned some of the diversion tunnel workers to lower paying jobs. All of the workers went on strike, and demanded better pay and safer work conditions. Six Companies refused, and the worker's appeal to the U.S. Secretary of Labor fell on deaf ears. Shortly after, the workers ended the strike for fear of losing their jobs. Six Companies did go on to improve working conditions, including additional lighting and water, as well as no more pay cuts.

Lower CofferdamConstruction of the lower cofferdam was delayed while the high-scaling of the canyon walls above the power plants and outlet works was completed.

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References

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