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 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.
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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 Overview
The 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 Overview
Six 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 Overview
What 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 Way
Lead 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 City
Boulder 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 for
families. 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 Task
Infrastructure
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 from
Boulder 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 Task
High 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 Task
Tunnels
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 Task
Cofferdams
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 I
n 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
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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 Cofferdam
Construction of the lower cofferdam was delayed while the high-scaling of the canyon walls above the power plants and outlet
works was completed.
References
http://www.usbr.gov/lc/hooverdam/History/essays.html
http://www.usbr.gov/lc/hooverdam/History/articlesmain.html
http://www.usbr.gov/lc/hooverdam/faqs/damfaqs.html
http://www.usbr.gov/lc/hooverdam/faqs/powerfaq.html
http://www.eia.gov/tools/faqs/faq.cfm?id=97&t=3
http://www.nps.gov/nr/twhp/wwwlps/lessons/140hooverdam
/140facts1.htm
http://www.usbr.gov/history/hoover.html
http://www.arizona-leisure.com/hoover-dam-men.html
http://www.pbs.org/wgbh/americanexperience/features/gener
al-article/hoover-building-boulder-city/
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