the

Building the Hoover Dam

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on its completion in 1936 this was the

largest concrete structure ever built

the incredible feat of engineering

played a critical role in the

development of the American Southwest

during the early 20th century providing

flood management's hydroelectric power

and securing a reliable source of water

for millions this is how the Hoover Dam

was built with plans around since 1900

to harness the power of the mighty

Colorado River

it wasn't until 1928 that the United

States Congress authorized the project

and initial surveying began with the

onset of the Great Depression just a

year later the project was seen as a way

for the government to provide

much-needed jobs in the American

Southwest which had been experiencing a

population boom prior to the stock

market crash located 26 miles southwest

of Las Vegas on the Nevada Arizona

border the project required a vast

number of workers and their families to

relocate and an entire new town was

established

owned and run by the government Boulder

City was to be a model for the rest of

the country to follow in the dark times

of the depression to drive the project's

progress president Hoover ordered

construction of the dam to start in May

1931 before the necessary infrastructure

at Boulder City was in place and many

workers lived in temporary tents in what

became dubbed rag town

to escape the harsh living conditions

many workers began to frequent the then

small outpost of Las Vegas driving

significant growth and earning its

reputation for gambling and adult

entertainment

though living conditions were poor work

began on diverting the Colorado River

so the dam could be constructed on the

dry riverbed to divert the water flow

for 56 foot 17 meter wide diversion

tunnels to on each side of the river

were bought through the canyon using

nothing more than dynamite followed by

workers using pneumatic jackhammers

excavated rock was then dumped into the

Colorado River creating a cofferdam the

forced water to flow through the newly

constructed tunnels a second coffer dam

downstream prevented water flowing back

into the construction site and formed an

area that could be pumped dry exposing

the riverbed

the Hoover Dam employs a gravity art

design and is held in place by the

weight of its concrete together with the

pressure of the water it holds forcing

it into the canyon floor and walls such

a principle required the canyon surfaces

to be smooth as one of the first

activities to prevent leaks it was

during this phase of the project that

the first hard hats began to be used

workers dipped their hats in tar and let

it harden protecting them at least to

some extent from falling debris seeing

their success the project's leaders

quickly ordered thousands of these hats

and mandated their use by the workers

in 1933 some 18 months ahead of schedule

the first concrete pours began on the

dam

as concrete gives off heat and contracts

as it cures a project on the scale of

the Hoover Dam would have taken more

than 125 years to harden if poured in a

single continuous pour and structural

weaknesses would have caused the dam to

crack under its own weight

instead the site was divided into a

series of rectangular molds some as

large as 50 square feet or 15 square

meters in size

these molds were fitted with a series of

steel pipes that carried river water

through them allowing the concrete to

cool and hardened much faster than if it

was left to do so alone in the heat of

the desert once the concrete had

hardened and stopped contracting the

pipes and hairline cracks between

neighboring blocks were filled in with

grout and a new layer of molds was

placed on top this process was repeated

time and again to build the dam walls as

the dama steadily rose getting the

concrete to where it had to go before it

began to harden started to pose a

significant challenge to overcome this

an ingenious system of overhead cables

that carried buckets of concrete from

specially built concrete plants on the

Nevada side of the dam to the required

location on the construction sites was

used in total eighty-seven point five

million cubic feet of concrete and some

582 miles of cooling pipes were used in

the construction of the dam by 1935 two

years ahead of schedule

the 726 foot high dam was complete and

the river dye version tiles were sealed

shut allowing the Colorado to begin

flooding the canyon behind the structure

and creating the reservoir we know today

as Lake Mead

fit out of the adjacent power plant and

its associated infrastructure took place

in parallel with construction of the

main structure and the dam began

generating electricity at the end of

1936 today this remarkable

infrastructure project has an average

output of 4.2 billion kilowatt hours and

provides water and electricity to

millions across the southwestern United

States an economic catalyst to an entire

region of North America and a powerful

example of the impacts that our industry

can have

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