One of the most fascinating places I’ve ever been was
when I visited Hoover Dam, an American icon. Although I had seen it in movies
and documentaries, nothing prepared me for the magnificence of it first hand
and in person. It’s not just a dam to provide water and electricity to
millions, it is also a work of art.
The unpredictable and powerful Colorado River overflowed
its banks every spring and flooded the land. It caused the ruin of crops and
loss of income for farmers all along its banks. If only there was a way to
control the water from the Colorado in order to irrigate the land and provide
drinking water for those who lived toward the south and to the west. Once
electricity blossomed in towns across the U.S. people began to wonder if they
could somehow use the Colorado to generate electricity. Taming the Colorado
would be a mammoth undertaking even for the best engineers of the day. So, when
the Government instructed the Bureau of Reclamation to come up with a solution,
it was decided to build the world's largest dam.
Frank Crow and Walker Young
Frank Crow, general superintendent, and Walker Young Engineer of Hoovered Dam were assigned the job to get it completed in the span from 1931 - 1935. The
construction of Hoover took 7 years at a cost of $ 125 million. Nowadays this
amount is about 788 million dollars. If the dam was not completed in the given
time it would have cost the contractors $ 3000 / day in financial penalties.
The site chosen for the megastructure Hoover Dam was
Black Canyon. It is an 800 feet high deep gorge through which the Colorado
River flowed. The spot, Black canyon is in the middle of the desert, so there
was no infrastructure, no labors, no transportation and the weather was harsh.
21,000 men took part in its construction and of them 112 laid their lives to
complete this mega structure. Situated in Mojave Desert, 30 Km south-east of Las
Vegas. Built on Colorado River at Black Canyon, the construction site was
extremely difficult. The risks involved were huge and the consequences could
have been catastrophic, if the dam failed.
The construction had to be done in stages. The first
stage was necessary to divert the Colorado. It’s kind of difficult to build a
dam while the river is pouring water over the area of construction. Just
considering the diversion of the river is exhausting and mind-boggling.
In April 1931 blasting began for construction on the
plain dry area where the dam would be placed. To divert the Colorado, 4 tunnels
were excavated on each side of the Canyon, measuring 4000 feet long and 56 feet
in diameter. These tunnels became diversion channels. Two tunnels were
constructed on the Nevada side and another two were constructed on the Arizona
side. Two small cofferdams were built to force water into the tunnels. Drilling,
digging, and blasting along with debris removal continued for 13 months, with
men working 3 shifts 24 hours a day, 7 days a week. Holidays were observed only
at Christmas, 4th July and Labor Day.
Apache Indians hired to work on high scaffolding
The workers faced harsh conditions but were paid only 40%
extra for this arduous and often dangerous work. No proper ventilation was
provides, work was extremely physically demanding. Men had to swing 100's of
feet down the canyon walls to remove dangerous loose rocks, using jacks and
dynamites. Due to lack of safety measure men required nerves of steel.
Workers swinging on the side of the canyon
The most
common cause of death was, being hit by falling rocks. But the construction of
Hoover Dam took place during the years of the Great Depression and workers were
actually happy to be hired no matter the danger of the work involved.
Because no roads led into the canyon, men and equipment
arrived at the work site by boat. Workers used 500 pneumatic drills, hoses, and
compressors to make holes in the canyon rock where explosives could be placed.
Once holes were drilled, workers used dynamite to blast into the rock and break
it into smaller pieces that could be hauled away by dump trucks. A ton of dynamite
was needed for every 14 feet of tunnel in the canyon walls. Special teams visited
the inside of the tunnels to ensure it would remain safe for the workers to
work inside. The tunnels were lined with concrete. By using this technique, the
workers were able to blast and excavate large diversion tunnels, each of which
was about the size of a 4-lane highway, lined with 3 feet of concrete. These
tunnels allowed the river water to be transported away from the construction
site at a rate of 1.5 million gallons per second. By November, 14, 1932, the 4
tunnels began to divert the water away from the site and the workers made alternate
cofferdams by using 100 trucks to dump dirt, rock, and debris into the water at
a rate of one truckload every 15 seconds. This amazing pace of dredging and
dumping went on for many months.
At this point Stage 2 of construction began. This was the
stage in which the actual dam was built. The work was huge and there were many
problems in design which needed to be solved. Hoover is an arch gravity dam,
incorporating two principles.
Arial View of Hoover Dam
The first principle has to do with the weight of the dam
forces into the ground due to its weight, thus helping it to remain stable. The
second principle is that the arch shape of the dam deflects the force of the
water into the canyon walls through the compression of the dam's concrete
walls, using the compressive strength of concrete because concrete is very
strong in compression. The major problem now was the pouring of 3.4 million
cubic meters of concrete. Plants were installed at the construction site to
produce concrete locally. But the dam was too big to be made into a single
concrete mount. If the concrete in the dam was poured in only one go, the
concrete would not have settled even by today. When the ingredients of concrete
- cement, sand, coarse aggregate combine in the presence of water, they start a
chemical reaction, resulting in the generation of internal heat which slows
down the curing process. The larger the pour, the longer the cure. If heat is
not dispersed, cracks would form and weaken the structure.
Concrete Dam Forms
The solution to the heat generating problem was to pour
the concrete in layers of interlocking blocks, each 5 feet tall. To accelerate
the setting of concrete, cool water pipes were passed through each block. The concrete
mix was cooled and cured faster. Then the
next layer was poured. To speed up pouring of concrete in the mega structure,
an elaborate overhead network of cables and pulleys was designed, carrying vast
buckets of concrete. Labors stayed on the site to spread, place and compact the
poured in concrete. Due to this new method, a record breaking volume - 8000
cubic meters of concrete was poured in a single day.
Secretary of the Interior Ray L. Wilbur announced the
structure would be called Hoover Dam at a 1930 dedication ceremony, though the
name didn’t become official until 1947. September 30, 1935 President Franklin
D. Roosevelt dedicated the completed dam.
The Hoover Dam Angels
I couldn’t help but notice the Art Nuevo design used for
the decorative columns in Hoover Dam. They are impressive and beautiful.
The Star Map in the center of the floor
Hanson Bas Relief on the inside wall of the dam
Here are some factoids for your inquisitive minds:
726.4 feet high (221 m)
1,244 feet wide (379 m)
660 feet (203 m) thick at the base
45 feet (13 m) thick at the top
$165 million dollars to build
4.5 years to build
4.4 million yards of concrete used for construction
March 1931 building began
September 30, 1935 completed
Powerhouse
17 generators
4+ billion kilowatt hours produced each year
10 acres of floor space
Power used by:
56% California
25% Nevada
19% Arizona
Lake Mead took 6.5 years to fill (A slow filling process
was required to lessen the pressure change on the dam and to help prevent small
earthquakes due to land settlement.)
589 feet (181 m) at the deepest point
247 square miles in size
110 miles (176 km) long
Named after Dr. Elwood Mead, Commissioner of the Bureau
of Reclamation (1924 - 1936)
Largest man made reservoir in the United States
Hoover Dam Memorial by Oskar J. W. Hanson
And there you have it, the great, iconic Hoover Dam. An
engineering accomplishment and a work of art.
Sarah
J. McNeal is a multi-published author of several genres
including time travel, paranormal, western and historical fiction. She is a
retired ER and Critical Care nurse who lives in North Carolina with her
four-legged children, Lily, the Golden Retriever and Liberty, the cat. Besides
her devotion to writing, she also has a great love of music and plays several
instruments including violin, bagpipes, guitar and harmonica. Her books and
short stories may be found at Prairie Rose Publications and its imprints Painted
Pony Books, and Fire Star Press. She welcomes you to her website and social media:
