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The Hoover Dam
Historical and geographical information
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Dates are in red.
Hyperlinks to other pages are in dark blue.
Headlines are in brown.
References and citations are in turquoise.
Context and local history are in purple.
In
1932, still a finish carpenter, Jim Farndale (FAR00607) had
become Business Agent for the Carpenter's Union. It was in this year that he
first became involved in the Boulder Dam project. By 1935 Jim had proved
himself to be an efficient
administrator through his work with the Carpenter's Union and the Boulder Dam
Project. He developed a reputation for reliability and honesty.
Accordingly, in 1936, he was elected to
the Nevada State Assembly.
The Hoover Dam (Originally the Boulder Dam Project)
Hoover Dam is a concrete arch gravity dam in
the Black Canyon of the Colorado River, on the border between Nevada and Arizona.
It was constructed between 1931 and 1936 during the Great Depression and
was dedicated on 30 September 1935 by President Franklin D. Roosevelt. Its construction was the
result of a massive effort involving thousands of workers,
and cost over one hundred lives. Originally
known as Boulder Dam from 1933, it was officially renamed Hoover
Dam, for President Herbert Hoover,
by a joint resolution of Congress in 1947.
Flying over the Hoover dam in 2016
Since about 1900, the Black
Canyon and nearby Boulder Canyon had been investigated
for their potential to support a dam that would control floods, provide
irrigation water and produce hydroelectric power. In 1928, Congress
authorized the project. The winning bid to build the dam was submitted by a
consortium called Six Companies Inc. Construction on the dam began
in early 1931. Such a large concrete structure had never been built before, and
some of the techniques were unproven. The torrid summer weather and lack of
facilities near the site also presented difficulties. Nevertheless, Six
Companies turned the dam over to the federal government on 1 March 1936, more
than two years ahead of schedule.
Hoover Dam impounds Lake Mead,
the largest reservoir in the United States by volume. The dam is located
near Boulder City, Nevada, a municipality originally
constructed for workers on the construction project, about 30 mi
(48 km) southeast of Las Vegas, Nevada. The dam's generators provide power for
public and private utilities in Nevada, Arizona, and California.
River view of the future dam
site, c. 1904 Hoover
Dam architectural plans Workers
on a "Jumbo Rig"; used for drilling Hoover Dam's tunnels
Soon after the dam was
authorized, increasing numbers of unemployed people converged on southern
Nevada. Las Vegas, then a small city of some 5,000, saw between 10,000 and
20,000 unemployed descend on it.
A government camp was
established for surveyors and other personnel near the dam site; this soon
became surrounded by a squatters' camp. Known as McKeeversville,
the camp was home to men hoping for work on the project, together with their
families. Another camp, on the flats along the Colorado River, was
officially called Williamsville, but was known to its inhabitants as "Ragtown".
When construction began, Six
Companies hired large numbers of workers, with more than 3,000 on the payroll
by 1932 and with employment peaking at 5,251 in July
1934. "Mongolian" (Chinese) labor was
prevented by the construction contract, while the number of African descent employed by Six Companies never exceeded thirty,
mostly lowest-pay-scale laborers in a segregated crew, who were issued separate
water buckets.
As part of the contract, Six
Companies, Inc. was to build Boulder City to house the workers. The original
timetable called for Boulder City to be built before the dam project began, but
President Hoover ordered work on the dam to begin in March 1931 rather than in
October. The company built bunkhouses, attached to the canyon wall, to
house 480 single men at what became known as River Camp. Workers with
families were left to provide their own accommodations until Boulder City could
be completed, and many lived in Ragtown. The
site of Hoover Dam endures extremely hot weather, and the summer of 1931 was
especially torrid, with the daytime high averaging 49 °C). Sixteen
workers and other riverbank residents died of heat prostration between
25 June and 26 July 1931.
The Industrial Workers of the World (“IWW”
or "Wobblies"), though much-reduced from their heyday as militant labour
organizers in the early years of the century, hoped to unionize the Six
Companies workers by capitalizing on their discontent. They sent eleven
organizers, several of whom were arrested by Las Vegas police. On 7 August
1931, the company cut wages for all tunnel workers. Although the workers
sent away the organizers, not wanting to be associated with the
"Wobblies", they formed a committee to represent them with the
company. The committee drew up a list of demands that evening and presented
them to Crowe the following morning. He was noncommittal. The workers hoped
that Crowe, the general superintendent of the job, would be sympathetic; instead he gave a scathing interview to a newspaper,
describing the workers as "malcontents".
On the morning of 9 August
1931, Crowe met with the committee and told them that management refused their
demands, was stopping all work, and was laying off the entire work force,
except for a few office workers and carpenters. The workers were given until
5 p.m. to vacate the premises. Concerned that a violent confrontation was
imminent, most workers took their paychecks and left
for Las Vegas to await developments. Two days later, the remainder were
talked into leaving by law enforcement. On 13 August 1931, the company began
hiring workers again, and two days later, the strike was called off. While
the workers received none of their demands, the company guaranteed there
would be no further reductions in wages. Living conditions began to improve
as the first residents moved into Boulder City in late 1931.
A second labour action took
place in July 1935, as construction on the dam wound down. When a Six Companies
manager altered working times to force workers to take lunch on their own time,
workers responded with a strike. Emboldened by Crowe's reversal of the lunch
decree, workers raised their demands to include a $1-per-day raise. The company
agreed to ask the Federal government to supplement the pay, but no money was
forthcoming from Washington. The strike ended.
Before the dam could be
built, the Colorado River needed to be diverted away
from the construction site. To accomplish this, four diversion tunnels were
driven through the canyon walls, two on the Nevada side
and two on the Arizona side. These tunnels were 56 ft (17 m)
in diameter. Their combined length was nearly 16,000 ft, or more than
3 miles (5 km). The contract required these tunnels to be completed
by 1 October 1933, with a $3,000-per-day fine to be assessed for any delay. To
meet the deadline, Six Companies had to complete work by early 1933, since only
in late fall and winter was the water level in the river low enough to safely
divert.
Tunneling began at the lower portals
of the Nevada tunnels in May 1931. Shortly afterward, work began on two similar
tunnels in the Arizona canyon wall. In March 1932, work began on lining the
tunnels with concrete. First the base, or
invert, was poured. Gantry cranes, running on rails through the entire
length of each tunnel were used to place the concrete. The sidewalls were
poured next. Movable sections of steel forms were used for the sidewalls.
Finally, using pneumatic guns, the overheads were filled in. The concrete
lining is 3 feet (1 m) thick, reducing the finished tunnel diameter to
50 ft (15 m). The river was diverted into the two Arizona
tunnels on 13 November 1932; the Nevada tunnels were kept in reserve for high
water. This was done by exploding a temporary cofferdam protecting
the Arizona tunnels while at the same time dumping rubble into the river until
its natural course was blocked.
Following the completion of the dam, the entrances to the two
outer diversion tunnels were sealed at the opening and halfway through the
tunnels with large concrete plugs. The downstream halves of the tunnels
following the inner plugs are now the main bodies of the spillway
tunnels. The inner diversion tunnels were plugged at approximately
one-third of their length, beyond which they now carry steel pipes connecting
the intake towers to the power plant and outlet works. The inner tunnels'
outlets are equipped with gates that can be closed to drain the tunnels for
maintenance.
To protect the construction site from the Colorado River and to
facilitate the river's diversion, two cofferdams were constructed. Work on the
upper cofferdam began in September 1932, even though the river had not yet been
diverted. The cofferdams were designed to protect against the possibility
of the river's flooding a site at which two thousand men might be at work, and
their specifications were covered in the bid documents in nearly as much detail
as the dam itself. The upper cofferdam was 96 ft (29 m) high, and 750
feet (230 m) thick at its base, thicker than the dam itself. It contained
650,000 cubic yards (500,000 m3) of material.
When the cofferdams were in place and the construction site was
drained of water, excavation for the dam foundation began. For the dam to rest
on solid rock, it was necessary to remove accumulated
erosion soils and other loose materials in the riverbed until
sound bedrock was reached. Work on the foundation excavations was completed in
June 1933. During this excavation, approximately 1.1M m3 of material was
removed. Since the dam was an arch-gravity type, the side-walls
of the canyon would bear the force of the impounded lake. Therefore, the side-walls were excavated too, to reach virgin rock, as
weathered rock might provide pathways for water seepage. Shovels for the
excavation came from the Marion Power Shovel Company.
The men who removed this rock were called "high
scalers". While suspended from the top of the canyon with ropes, the
high-scalers climbed down the canyon walls and removed the loose rock
with jackhammers and dynamite.
Falling objects were the most common cause of death on the dam site; the high
scalers' work thus helped ensure worker safety. To protect themselves
against falling objects, some high scalers took cloth hats and dipped them in
tar, allowing them to harden. When workers wearing such headgear were struck
hard enough to inflict broken jaws, they sustained no skull damage. Six Companies
ordered thousands of what initially were called "hard boiled hats"
(later "hard hats")
and strongly encouraged their use.
The cleared, underlying rock foundation of the dam site was
reinforced with grout, called a grout curtain.
Holes were driven into the walls and base of the canyon, as deep as 46 m
into the rock, and any cavities encountered were to be filled with grout. This
was done to stabilize the rock, to prevent water from seeping past the dam
through the canyon rock, and to limit "uplift"—upward pressure from
water seeping under the dam. The workers were under severe time constraints due
to the beginning of the concrete pour, and when they encountered hot springs or
cavities too large to readily fill, they moved on without resolving the
problem. A total of 58 of the 393 holes were incompletely filled. After
the dam was completed and the lake began to fill, large numbers of significant
leaks into the dam caused the Bureau of Reclamation to look
into the situation. It found that the work had been incompletely done, and was based on less than a full understanding of the
canyon's geology. New holes were drilled from inspection galleries inside the
dam into the surrounding bedrock. It took nine years (1938–47) under
relative secrecy to complete the supplemental grout curtain.
The first concrete was poured into the dam on 6 June 1933,
18 months ahead of schedule. Since concrete heats and
contracts as it cures, the potential for uneven cooling and
contraction of the concrete posed a serious problem. Bureau of Reclamation
engineers calculated that if the dam were to be built in a single continuous
pour, the concrete would take 125 years to cool, and the resulting stresses
would cause the dam to crack and crumble. Instead, the ground where the dam
would rise was marked with rectangles, and concrete blocks in columns were
poured, some as large as 50 ft square (15 m) and 5 feet (1.5 m)
high. Each five-foot form contained a series of 1-inch (25 mm) steel
pipes; cool riverwater would be poured through the
pipes, followed by ice-cold water from a refrigeration plant.
When an individual block had cured and had stopped contracting, the pipes were
filled with grout.
Grout was also used to fill the hairline spaces between columns, which were
grooved to increase the strength of the joins.
The concrete was delivered in huge steel buckets 7 feet high
(2.1 m) and almost 7 feet in diameter; Crowe was awarded two patents
for their design. These buckets, which weighed 20 short tons (18 t) when
full, were filled at two massive concrete plants on the Nevada side, and were
delivered to the site in special railcars.
The buckets were then suspended from aerial cableways which
were used to deliver the bucket to a specific column. As the required grade
of aggregate in the concrete differed
depending on placement in the dam (from pea-sized gravel to 9-inch or
23 cm stones), it was vital that the bucket be maneuvered
to the proper column. When the bottom of the bucket opened up,
disgorging 8 cu yd (6.1 m3) of concrete, a team of men worked it
throughout the form. Although there are myths that men were caught in the pour
and are entombed in the dam to this day, each bucket deepened the concrete in a
form by only an inch, and Six Companies engineers would not have permitted a
flaw caused by the presence of a human body.
A total of 3,250,000 cubic yards (2,480,000 cubic metres) of
concrete was used in the dam before concrete pouring ceased on 29 May 1935. In
addition, 1,110,000 cu yd (850,000 m3) were used in the power
plant and other works. More than 582 miles (937 km) of cooling pipes were
placed within the concrete. Overall, there is enough concrete in the dam to
pave a two-lane highway from San Francisco to New York. Concrete cores
were removed from the dam for testing in 1995; they showed that "Hoover
Dam's concrete has continued to slowly gain strength" and the dam is
composed of a "durable concrete having a compressive strength exceeding
the range typically found in normal mass concrete".[65] Hoover
Dam concrete is not subject to alkali–silica reaction (“ASR”), as
the Hoover Dam builders happened to use nonreactive aggregate, unlike that at
downstream Parker Dam, where ASR has caused measurable deterioration.
With most work finished on the dam itself (the powerhouse
remained uncompleted), a formal dedication ceremony was arranged for 30 September
1935, to coincide with a western tour being made by President Franklin D. Roosevelt. The morning of the
dedication, it was moved forward three hours from 2 p.m. Pacific time to
11 a.m.; this was done because Secretary of the Interior Harold L. Ickes had
reserved a radio slot for the President for 2 p.m. but officials did not
realize until the day of the ceremony that the slot was for 2 p.m. Eastern
Time. Despite the change in the ceremony time, and temperatures of
102 °F (39 °C), 10,000 people were present for the President's
speech, in which he avoided mentioning the name of former President Hoover, who
was not invited to the ceremony. To mark the occasion, a three-cent stamp
was issued by the United States Post Office Department bearing the name
"Boulder Dam", the official name of the dam between 1933 and 1947. After
the ceremony, Roosevelt made the first visit by any American president to Las
Vegas.
Most work had been completed by the dedication, and Six
Companies negotiated with the government through late 1935 and early 1936 to
settle all claims and arrange for the formal transfer of the dam to the Federal
Government. The parties came to an agreement and on 1 March 1936, Secretary
Ickes formally accepted the dam on behalf of the government. Six Companies was
not required to complete work on one item, a concrete plug for one of the
bypass tunnels, as the tunnel had to be used to take in irrigation water until
the powerhouse went into operation.