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Concrete
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Concrete Projects > Hoover Dam - Colorado River Black
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Hoover Dam - Colorado River Black Canyon
The First Major Dam, 1936
 Regaled
as an architectural and engineering marvel, Hoover Dam was built
in five years-two years under schedule-at the cost of $48.9
million. It stands 726 feet tall and 1,244 feet in length. The
base is 660 feet thick, 60 feet more than the length of two
football fields, and the top is 45 feet thick. At the base of
the dam lay 230 blocks of concrete, each one standing five feet
high and ranging in width from 25 square feet to 60 square feet.
Before concrete contractors could even get to work constructing
the dam, however, the enormous task of diverting the Colorado
River had to be accomplished. In order to do that, four diversion
tunnels totaling 16,000 feet were cut into Black Canyon and
lined with concrete, a project that in itself took a full year.
While water from the river was diverted through these tunnels,
suspended high scalers worked on the walls of the canyon to
ensure that they were smooth enough to allow proper adherence
of the dam's walls, and work crews dredged the canyon's floor
down to bedrock.
On June 6, 1933, concrete contractors made history by pouring
the first bucket of concrete on the Hoover Dam. Contractors
produced the mix onsite in two batch plants, transported to
the dam by railroad cars, and poured by an overhead bucket system.
This system was able to deliver one bucket of concrete every
78 seconds. The size and nature of the project presented a unique
problem, however. Regardless how fast the concrete was poured,
contractors realized that by using traditional processes, it
would take 100 years for the dam's concrete to cool and cure.
And once it did cool, the concrete would crack, rendering the
dam useless.
 The
situation required innovations to expedite the curing process.
The contractors imbedded more than 582 miles of one-inch steel
pipe throughout the concrete, pipe that carried river water
and ice water to cool down the concrete. The refrigeration plant
built onsite to carry out this feat had the capability of producing
a 1000-pound block of ice daily. When the concrete was set into
place and the pipes were no longer needed, they were filled
in with concrete to add extra strength to the dam. In this way,
the dam was poured into separate interlocking blocks.
In August of 1933, two of the diversionary tunnels were filled
in, and in 1935 steel grates weighing 1000 tons were placed
over the remaining two tunnels to begin channeling the Colorado
River towards the dam.
All in all, concrete contractors used some 3.3 million cubic
yards of concrete in the making of Hoover Dam and another
million cubic yards for the power plant and support structures.
This was enough cement to build a two-lane highway from Seattle,
Washington to Miami, Florida.
Thanks in large part to the concrete contractors who worked
on it, Hoover Dam was completed in 1935, began power generation
in 1936, and the last turbine went on line in 1961. It was named
a National Historic Landmark, and the American Society of Civil
Engineers named it one of America's Seven Modern Civil Engineering
Wonders.
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