HOOVER DAM FAST FACTS AND FIGURES
Where is Hoover Dam?
In Black Canyon on the Colorado River, about 30 miles southeast ofLas Vegas, Nevada.
What were the excavation depths from the river's low-water surface to foundation rock?
In the upstream cut off trench, it was 139 feet. The remaining excavation depths average 110 to 130 feet.
What are the geologic conditions at the dam site?
The foundation and abutments are rock of volcanic origin geologically called "andesite breccia." The rock is hard and
very durable.
What construction work was necessary before operations started at the dam site?
(I) Construction of Boulder City to house both Government and contractor employees}
.
.
(2) construction of7 miles of 22-foot wide, asphalt-surfaced highway from Boulder CIty to the dam SIte;
(3) construction of22.7 miles of standard-gauge railroad from the Union Pacific main line in Las Vegas to Boulder CIty
and an additional 10 miles from Boulder City to the dam site;
(4) construction of a 222-mile-Iong power transmission line from San Bernardino, California, to the dam site to supply
energy for construction.
What were the principal divisions of work?
.
More than 5,500,000 cubic yards of material were excavated, and another 1,000,000 CUbIC yards of earth and rock fill
placed. By feature, this included:
Excavation for the diversion tunnels, 1,500,000 cubic yards
For the foundation ofthe dam, power plant, and cofferdams 1,760,000 cubic yards;
For the spillways and inclined tunnels, 750,000 cubic yards
For the valve houses and intake towers, 410,000 cubic yards
Earth and rock fill for the cofferdams, 1,000,000 cubic yards.
In addition, 410,000 linear feet of grout and drainage holes were drilled, and 422,000 cubic feet of grout were placed
under pressure.
When did construction begin?
Construction on Hoover Dam began September 30, 1930.
What were the quantities of principal materials used in the dam?
The principal materials, all of which were purchased by the government, were:
Reinforcement steel, 45,000,000 pounds
Gates and valves, 21,670,000 pounds
Plate steel and outlet pipes, 88,000,000 pounds
Pipe and fittings, 6,700,000 pounds or 840 miles
Structural steel, 18,000,000 pounds
Miscellaneous metal work, 5,300,000 pounds.
How much steel and metal work was used to build the dam?
There are 96,000,000 Ibs of steel and metalwork used by the dam - but none of it in the dam.
What type of dam is Hoover?
Hoover Dam is a concrete arch-gravity type, in which the water load is carried by both gravity action and horizontal arch
action.
Why is the dam curved?
The Hoover Dam is a curved gravity dam. Lake Mead pushes against the dam, creating compressive forces that travel
along the great curved wall. The canyon walls push back, counteracting these forces. This action squeezes the concrete in
the arch together, making the dam very rigid. This way, Lake Mead can't push it over. The Hoover Dam is so thick and
heavy, it doesn't even need to be curved! It's heavy enough to resist the weight and thrust of the water pushing behind it,
but designers thought people would feel safer with a curved design.
When was the first concrete laid?
The first concrete for the dam was placed on June 6, 1933 and approximately 160,000 cubic yards of concrete were placed
in the dam per month until the dam was finished. Peak placements were 10,462 cubic yards in one day (including some
concrete placed in the intake towers and powerplant), and slightly over 275,000 cubic yards in one month. The daily
demand during construction of the dam was from 7,500 to 10,800 barrels. Reclamation had used only 5,862,000 barrels
in its 27 years of construction activity preceding June 30, 1932.
How much concrete is in the dam?
Hoover Dam was the first single structure to contain more masonry than the Great Pyramid at Giza. There are more than
5,000,000 barrels, or 4,360,000 cubic yards of concrete in the dam, power plant and extra work places. Approximately
160,000 cubic yards of concrete were placed in the dam per month. Peak placements were 10,462 cubic yards in one day
(including some concrete placed in the intake towers and power plant), and slightly over 275,000 cubic yards in one
1
month. This much concrete would build a monument 100 feet square and 2-1/2 miles high; This would rise higher than the
Empire State Building (which is 1,250 feet); or would pave a standard highway 16 feet wide, from San Francisco to New
York City or from Seattle, Washington, to Miami, Florida, or if you prefer - a four-foot-wide pavement around the Earth
at the Equator.
How much cement was required?
More than 5 million barrels. The daily demand during construction of the dam was from 7,500 to 10,800 barrels.
Reclamation had used only 5,862,000 barrels in its 27 years of construction activity preceding June 30, 1932.
How was the chemical heat caused by setting cement in the dam dissipated?
By embedding more than 582 miles of I-inch steel pipe in the concrete and circulating ice water through it from a
refrigeration plant that could produce 1,000 tons of ice in 24 hours. Cooling was completed in March 1935.
What was an unusual feature of Hoover Dam's construction?
The dam was built in blocks or vertical columns varying in size from about 60 feet square at the upstream face of the dam
to about 25 feet square at the downstream face. Adjacent columns were locked together by a system of vertical keys on
the radial joints and horizontal keys on the circumferential joints. Concrete placement in anyone block was limited to 5
feet in 72 hours. After the concrete was cooled, a cement and water mixture called grout was forced into the spaces
created between the columns by the contraction of the cooled concrete to form a monolithic (one piece) structure.
How long did it take to build the dam, power plant, and appurtenant works?
Five years. The contractors were allowed 7 years from April 20, 1931, but concrete placement in the dam was completed
May 29, 1935, and all features were completed by March 1, 1936.
When was the last of the concrete poured in the dam?
The last concrete was placed in the dam on May 29, 1935.
How many men were employed during the dam's construction?
A total of21,000 men worked on the Dam with an average of3,500 and a maximum of 5,218 daily, which occurred in
June 1934. The average monthly payroll was $500,000.
How many generators does Hoover Dam have?
Hoover Dam has 17 generators giving it the capacity to produce over 2,000 megawatts of electricity.
How much power does Hoover Dam generate?
The generators have a power generating capacity of 2.8 million kilowatts.
How much water is needed to run the generators?
During peak periods of electrical demands, enough water runs through the generators to fill 15 average-size swimming
pools (20,000 gallons each) per second.
How many people benefit from the water from the dam?
Hoover Dam is part of a system, which provides water to over 25 million people in the southwest United States.
How tall is the dam?
It is 726.4 feet or seven stories high, from foundation rock to the roadway on the crest of the dam. The towers and
ornaments on the parapet rise 40 feet above the crest. That's almost 200 feet taller than the Washington Monument in
Washington, D.e.
How thick is the base ofthe dam?
At its base, Hoover Dam is as thick (660 feet) as two footballs fields measured end to end.
How thick is the concrete at the top?
The dam is 45 feet thick at the top.
How much does Hoover Dam weigh?
More than 6,600,000 tons.
What is the maximum water pressure at the base of the dam?
45,000 pounds per square foot.
What is the reservoir Capacity?
Total storage capacity is 9.2 trillion gallons or 1.24 trillion cubic feet or 30,500,000 acre feet of the Colorado River in its
reservoir, or to put it another way the reservoir can store up 2 years 'average' water flow from the Colorado River.
How much did it cost?
The total cost to build the dam was $165 million.
What is the name ofthe reservoir behind the dam?
Lake Mead, the largest man made 'lake' in America.
MORE FACTS ABOUT THE RESERVOIR.
The surface area of Lake Mead is 146,000 acres.
The maximum water surface elevation of Lake Mead is 1229 FT.
The maximum depth of Lake Mead is 590 FT.
The length of Lake Mead is 115 miles.
2
FLOOD!
Why a Dam Was Needed.
In the distant past, the Gulf of California extended 150 miles further inland from its present day shore.
There it formed a bay 50 miles wide. Each year the river deposited over 140,000 acre-feet of silt at the rivers
delta. This is enough to cover 214 square miles in 1 foot of soil. Eventually these accumulated deposits
grew so thick the area was sealed off the upper portion of the gulf. Cut off from the river, the water that
remained formed a huge shallow lake. When the Colorado flooded, its waters would spill into this lake.
Over time, flooding, local run-off and evaporation made this a salt-water lake.
The area evolved into a geological anomaly. It became a huge 2000 square mile desert, the Colorado Desert
and the lake was known as the Salton Sink. At its lowest point, it was 300 feet below sea level.
In the early 1850's, an idea was conceived of cutting a channel from the Colorado river to the Colorado
Desert in California now known as Imperial Valley but it took until 1901, when a surveyor and engineer,
Charles Rockwoo~ also saw the possibilities of a canal to the area and approached an investor named
George Chaffey who knew the value of irrigation because he had made a fortune in the Los Angeles area
planting Orange groves. Chaffey decided to underwrite the project and on May 14, 1901, the canal saw its
ftrst water. A lot ofland was sold and people moved into the area. By 1904, the population of Imperial
Valley grew to over 7,000. The agricultural production of the area went far beyond the most optimistic
forecast.
Unfortunately, sometimes when dreams come true, the dream might actually turn into a nightmare. In the
spring of 1904 the huge volume of silt, which the Colorado carried with it found its way into the canal. By
1904 a 4-mile long section of the canal had become clogged with this silt. Efforts to keep the canal clear
were in vain. In the fall and winter seasons the water flow of the Colorado subsided. The rivers flow into
the canal completely subsided. A huge fortune in crops died due lack of water.
In March 1905, the spring flooding season began and the Colorado River broke through and a small lake
began to form in the Salton Sink. As more water
accumulated, the Salton Sink became the Salton Sea covering about 150 square miles in 60 feet of water.
By November 1905, matters got worse. By this time over150,000 cubic feet per second flowed through the
canal.
The Colorado River was now flowing into the Imperial Valley instead ofthe Gulf of California. Instead of
huge tracts of bountiful, irrigated croplands, this disaster promised to turn the area into a huge inland sea.
Could things have gotten worse? Yes. It began as a small waterfall not far from where the river poured into
the Salton Sea near Anza Borrego outside of San Diego. An erosion process know as a 'cutback' was
beginning to make its effects known. The consequences of the cutback was likely to destroy huge sections
of southwest Arizona and southeast California. the sandy soil could not withstand the force of the water
running over it. Trying to 'equalize' its descent into lower elevations, the river started to erode its way back
to its highest point.
The accumulated silt deposits weren't solid and there was no way to stop the process of erosion. In fact it
was speeding up. The once tiny waterfall reached a height of 100 feet and was cutting through the desert at
the rate of 1 mile a day. If the cutback reached the intake, the falls would be 300 feet high and the river
channel would be so deep that the Colorado River would never be able to return to the Gulf of California.
Some geologists, seeing that the same conditions existed throughout the whole area, predicted that the
cutback could eventually carve a canyon 1 MILE deep and several hundred miles long! Sort of another
Grand Canyon to go with the new inland sea.
Under pressure from Theodore Roosevelt, E. Harriman, Robber Baron owner of the Southern Paciftc, made
his money, engineers and facilities available to stop this
disaster. It took 2 years and 3 million dollars to put the Colorado back in its original channel.
On February10, 1907, the breach was ftnally closed. The nightmare had ftnally ended, for now. Then less
than two years later the Colorado began flooding the valley again. It looked like it was going to be a repeat
of the 1905-1907 episode. Finally, in 1910, the U.S. Congress, appropriated $1,000,000 to build a chain
of levees to give this problem some temporary relief from the flooding.
This chain of events proved two things. It was obvious that something much more permanent was needed
and that it was possible to harness this incredible river.
1
THE WATERS OF THE COLORADO.
A river has to start somewhere and the Colorado rises high up in the Colorado Rocky
Mountains National Park at the Continental Divide, the point in American where the rivers
decide whether to go east or west.
The Colorado goes west, travelling 1,450 miles and dropping 10,000 feet in its descent
from the mountains to the sea, ending in the Gulf of California. It grows in size and
strength as it's joined along the way by many tributaries.
The river does its greatest work during flood with the transportation of rocks, suspended
solids and dissolved materials. The amount carried by the river varies greatly. In Hood this
mighty river has been gauged to have carried 27,600,000 tons of debris in one day although
on an average day the amount is only 391,780 tons.
High water marks left by a flood that took place in July of 1884 computed to a maximum
flow of 300,000 cubic feet per second. In 1927 the river flood averaged a massive 127,000
cubic feet per second and this was when California was flooded causing the loose of crops
and money and fearing a worse flood like the one in 1884 would happen again, it was
decided a dam was needed.
To put that into perspective, fthe approximate 400,000 average burden were loaded into
dump trucks with a 5-ton capacity each, it would take 80,000 trucks going by at little more
than a second apart for twenty-four hours to do the same amount of work the river does
naturally each day.
Since the construction of Glen Canyon Dam, which has slowed the river, the gouging effect
has lessened and today the average is about 80,000 tons of material per day, or about 1/5 th
as much as when the river ran wild.
Studies show that the overall rate of 'carving' for the entire Colorado River Drainage area
has been averaging about 6 Y2 inches for each 1,000 years.
THE COLORADO RIVER AND
THE COLORADO RIVER COMPACT
The Colorado River rises in the snow capped mountains of north central Colorado and zigzags southwest for
more than 1,400 miles before reaching the Gulf of California.
The river and its tributaries - the Green, the Gunnison, the San Juan, the Virgin, the Little Colorado, and the
Gila Rivers - are called the "Colorado River Basin." These rivers drain 242,000 square miles in the United
States, or one-twelfth of the country's continental land area, and 2,000 square miles in Mexico. Seven
western states and Mexico have beneficial interests in the Colorado River Basin and they are: Arizona,
California, Colorado, Nevada, New Mexico, Utah, and Wyoming.
Each state is party to the Colorado River Compact entered into in Santa Fe, New Mexico, on November 24,
1922. This agreement divided the Colorado River Basin into the Upper Basin and the Lower Basin. The
division point is Lees Ferry, a point in the main stem of the Colorado River about 30 river miles south of the
Utah-Arizona boundary. The "Upper Basin" includes those parts of the States of Arizona, Colorado, New
Mexico, Utah, and Wyoming within and from which waters naturally drain into the Colorado River system
above Lees Ferry, and all parts of these States that are not part of the river's drainage system but may benefit
from water diverted from the system above Lees Ferry.
The "Lower Basin" includes those parts of the States of Arizona, California, Nevada, New Mexico, and Utah
within and from which waters naturally drain into the Colorado River system below Lees Ferry, and all parts
of these States that are not part of the river's drainage system but may benefit from water diverted from the
system below Lees Ferry.
The Colorado River Compact apportions to each basin the exclusive, beneficial conswnptive use of
7,500,000 acre-feet of water per year from the Colorado River system in perpetuity. In addition, the
Compact gives to the Lower Basin the right to increase its annual beneficial conswnptive use of such water
by 1,000,000 acre-feet.
The original Colorado River Compact did not apportion water to any State until October 11, 1948, when the
Upper Basin States entered into the Upper Colorado River Basin Compact, which apportioned use of the
Upper Basin waters among them. The compact now permits Arizona to use 50,000 acre-feet of water
annually from the upper Colorado River system, and apportioned the remaining water to the Upper Basin
States in the following percentages:
Colorado, 51.75 percent
New Mexico, 11.25 percent
Utah, 23 percent; and
Wyoming, 14 percent.
The Lower Basin States of Arizona, California, and Nevada were not able to reach agreement. In 1952,
Arizona filed suit in the United States Supreme Court to October 1962, the Court ruled that of the first
7,500,000 acre-feet of main stem water in the Lower Basin, California is entitled to 4,400,000 acre-feet,
Arizona 2,800,000 acre-feet, and Nevada, 300,000 acre-feet.
The United States has contracted with the States of Arizona and Nevada and with various agencies in
Arizona and California for the delivery of Colorado River water. These contracts make delivery of the water
contingent upon its availability for use in the respective States under the Colorado River Compact and the
Boulder Canyon Project Act.
The United States and Mexico entered into a treaty on February 3, 1944, which guarantees Mexico
1,500,000 acre-feet of Colorado River water annually. This entitlement is subject to increase or decrease
under certain circumstances provided for in the treaty.
1
THE COMPANIES WHO BUILT THE DAM
The dam was under the direct supervision of the Washington and Denver offices of the
U.S. Government's Bureau of Reclamation; actual designs of all its features were made in
the Denver office. It was built by a group of western contractors, calling themselves the
Six Companies.
When Washington announced it had the job for somebody, a sudden low scribbling was
heard in the land. This was the sound of estimating. Most of it died very quickly, as
contractors realized the job was too huge even to bid on. But in San Francisco, Salt Lake
City, Boise, and Portland, telephones jangled and very quickly the hard heads of Bechtel
& Kaiser and MacDonald & Kahn (San Francisco), Morrison-Knudson Co. (Boise), Utah
Construction Co. (Salt Lake City), and Portland's J.F. Shea and the Pacific Bridge Co.
were put together. They set up a joint corporation capitalized for $8,000,000, called it the
Six Companies, scribbled, estimated, and bid $48,890,995, bonded the contract for
$5,000,000 in cash. They got the job.
For their $48,890,995 the Six Companies had to foot all construction bills - for dynamite,
for trucks, for digging mud and dumping mud, for bosses' salaries, and for labor's wage.
The Six companies did not pay for construction raw material- for the 5,500,000 barrels
of cement consumed, or the 55,000 tons of steel plates and castings, or the turbines and
generators in the power plant, or any of the
pennanent operating machinery of the dam.
It is not feasible to detail a month's or even a year's statement of the Six Companies, since
their expenses varied enonnously. They were out of pocket $3,500,000 for preliminary
work before they received a government penny. Until half the work was done they
received only ninety cents on the dollar. The holdback is around $2,000,000, which they
received at the end - like an ice-cream cone for being good. It suffices perhaps to say that
during the first five months of 1933 the government paid an average monthly bill from
the Six Companies of $1 ,513,000. out of this the corporation paid items such as a half­
million a month payroll, $48,000 for gas and oil, $40,000 for electricity.
At one time when the roads were roughest, they were spending $500 a day for truck and
automobile tires. When the last bills were paid and the turbines began to turn, the Six
companies turned a profit estimated at $7,000,000 and upward for all their work.
This profit, which must be understood, is the insurance premium the U. S. pays for
efficiency. If the contractors spent all their money, botched the job, and went broke, the
government might have to finish the dam to the tune of a great many millions. The U.S.
was willing to pay a good profit for a good dam built rapidly.
One ofthe few complaints of the men on the job is that the bosses were "highballing" ­
labor slang for forcing work to the limit. Their contract started April 20, 1931. they
"highballed" the job to a point seventeen months ahead of schedule. This speed cost the
1
Six Companies money in many operations - money, which was more than saved by
finishing the darn an estimated year and a half before its appointed birthday, April 20
1938.
a government inspector was required, who reported the contents of every batch of
cement, the blast of every dynamite barrage, the loads on the cableways, and the depth of
every hole. He even went down the canyon wall on ropes to outline the rock to be
moved. He had to report on the tons of rock chipped off by high scalers. Over 150 men
were paid government money to stick their noses into the contractor's business. Not until
they were satisfied that the work conformed in the minutest detail to rigid V.S.
specifications did the Six Companies get Washington's check for the preceding month's
payroll and expenses. The man in charge of the inspectors was Walker Young, (General
Superintendent, Six Companies). He worked with Frank Crowe, (V.S. Construction
Engineer in charge). Such a system should build a good darn but it could also cause
some friction but the friction factor at Boulder was nearly non-existent and the reason is
in the history and makeup of the two men in charge of building the darn.
Frank Crowe and Walker Young had two reasons why they were not bitter enemies. One
was that the job was too big for petty human friction. Young's inspectors and Crowe's
foremen knew this as well as their bosses. They knew that friction, which slows work,
quietly rubs somebody out of a job. The second reason was the mutual respect of the two
men. Crowe spent years in the V.S. Reclamation Service, which Young now represented.
He knew Young's duties and responsibility as well as Young did. "I'd go to hell for him,"
Crowe was quoted as saying.
NOTE; Frank Crowe got $25,000 a year plus bonuses. Young got $6,375 in bonus and
up to this job this government work rated no bonus. Regardless of salary, Walker Rollo
Young was the undisputed boss at Boulder Darn.
2
WHERE THE MEN WHO BUILT THE DAM
CAME FROM
State
Number of Men
State
Number of Men
Alabama
243
Nebraska
157
Arizona
643
Nevada
5522
Arkansas
191
New Jersey
104
California
5055
New Mexico
109
Connecticut
467
New York
221
Colorado
467
New Hampshire
14
Delaware
1
North Carolina
120
Florida
66
Ohio
260
Georgia
115
Oklahoma
581
Idaho
599
Oregon
273
Illinois
487
Pennsylvania
238
Indiana
159
Rhode Island
8
Iowa
181
South Carolina
29
Kansas
327
South Dakota
58
Kentucky
103
Tennessee
121
Louisiana
85
Texas
604
Maine
18
Utah
1165
Maryland
66
Virginia
44
Massachusetts
114
Vermont
6
Missouri
548
Washington
642
Michigan
251
West Virginia
73
Minnesota
208
Wisconsin
171
Mississippi
50
Wyoming
161
Montana
340
Foreign workers
116
Total = over 21,000
LIVING AND WORKING CONDITIONS AT HOOVER DAM:
RAGTOWN
The real story behind Hoover Dam is the thousands who built it and the families that endured the
living hell to bring it all to realty. In particular those that died from the harsh conditions or on the job.
Construction of Hoover Dam didn't begin until April of 1931, but men and their families began
drifting into Las Vegas (30 miles from the dam site) in early 1929 after the Stock Market Crash of 1929 and
the Great Depression. Vegas was a small desert outpost and not prepared for the thousands of "new
residents", unemployed desperate people who poured in for a limited number of Hoover Dam construction
jobs. Many came with all their possessions, wives, children and little or no money and because of that they
had no choice but to live in squalid, tightly compacted tent cities. Dam construction was months away and
there was no guarantee of employment, but many had nowhere else to go and those that did had no money
to get there.
Many citizens of Las Vegas provided food, care and clothing for the migrants who managed to
survive very tough conditions.
Prompted by the Depression and mounting stress on future dam workers and the town of Las Vegas,
the government pushed the construction to begin six months early. Although the federal government had
begun planning for housing and human welfare infrastructure, they used the excuse that the quickened
construction schedule left no time for barracks or house building.
Then the hiring began and the work commenced. Some who had transportation stayed in Las Vegas
to make the daily commute through 30 miles of the dusty and bumpy Boulder road but since most people
equated being close to the dam site with the success of getting a job, most decided to live near the job site.
The infamous community of "Ragtown" on the floor of Black Canyon next to the Colorado River was born.
The makeshift shantytown consisted of tents, cardboard boxes, tin scraps and anything else that could serve
as shelter against the scalding heat of summer and freezing nights of winter. Ragtown first swelled to 1,400
people looking for employment and then, as construction reached its peak, the population ballooned to 5,000
men, women and children.
Even under the best of conditions dam building is tough, exhausting work. Those working on the
construction of Hoover Dam had to contend with other factors that made their work much more risky and
dangerous. One was the searing, relentless heat as the temperature at the work site would routinely soar to
above 120 degrees during the summer and plummet to well below freezing in the winter. An added pressure
felt by the workers was the insistence of supervisors and managers to finish the job in record time. Millions
of dollars were at stake. Six Companies, the outfit building the dam, had agreed to a rigid government
deadline--two and a half years to divert the river or face steep fines for every day they ran late. In the rush
to meet their deadline, Six Companies often sacrificed the men's safety for speed.
Working seven days a week, dam workers were exposed to all manner of dangers: carbon monoxide
poisoning, dehydration, heat prostration, and electrocution from carelessly placed electrical lines. To top it
off, workers knew they had very little leverage to lobby for changes. With a quarter of the nation's work
force idle, the workers at Hoover Dam knew they were expendable.
Frank Anderson, a professional organizer for the radicallabor union, the Industrial Workers ofthe
World (IWW), had been dispatched to Las Vegas to recruit members and stir up demands for better working
conditions and higher pay. Workers regarded Anderson and the IWW with suspicion and fear because they
knew any affiliation with any labor group, and that one in particular, would result in their having no job to
complain about. Meanwhile, Six Companies, along with officials in Las Vegas and elements within the
Reclamation Service, made concerted efforts to discredit and drive out the IWW. Frank Anderson was
jailed on trumped up vagrancy charges.
Workers reached a breakpoint during July and August of 1931 as life in Ragtown became
devastating. With average July temperatures of 116 degrees and approaching 130 degrees on the floor of
Black Canyon combined with swirling dust and no natural shade, over 25 men, women and children died in
that first June-July period of heat conditions.
PTO
1
Then on August 7, Six Companies reassigned a number of diversion tunnel workers to lower paying
jobs. Within hours, the entire work force went out on strike. Six Companies contended that only 30
muckers, unskilled laborers who loaded broken rocks into trucks, would be affected by the pay reduction.
Workers decided that it was time not just to protest the pay cut but to list their grievances and issue
demands. Among them: that clean water and flush toilets be provided, that ice water be readily available to
workers, and that Six Companies obey all mining laws issued by the States of Nevada and Arizona.
Significantly, the striking mine workers also voted to disassociate themselves from the IWW.
Upon reviewing the workers' demands, job supervisor Frank Crowe echoed the feelings of his bosses
in rejecting every one of them. The strikers made a last- ditch appeal to the U.S. Secretary of Labor,
William Doak, to intervene on their behalf. He refused. Knowing they were beaten, and worried they might
not get their jobs back, the strikers voted to return to the dam site but only once Six Companies pledged its
pay cut would be the last. Additionally they agreed efforts had to be made to improve work conditions and
additional lighting and water was made available, and construction of living quarters in Boulder City was
sped up.
Life didn't change quickly for the people of Ragtown or for the workers. The federal government
already had plans to build a dam workers town on federal land above and close by Black Canyon where
Hoover Dam would stand. Because of the publicity generated by the strike, and the reaction of the general
public, they pushed forward to achieve workers relief with barracks, housing, stores and general public
welfare with churches and schools for the children. That town which became Boulder City, Nevada was
completed in 1932.
While they waited for a decent place to live in, a man by the name ofMurl Emery and his family
provided compassionate relief when they opened a store in Ragtown for dam workers and families with food
and supplies trucked from Las Vegas. With low hourly labor rates of 50 cents an hour, Murl Emery
permitted Ragtown residents to pay what they could afford. Credit was issued on the honor system and only
one person ever failed to pay his debt - and that was because the customer died. With no help from the
government or the contracted dam building firm, it was Murl Emery and family that provided some relief in
the form of food and tangible needs.
Although clouded with sediment, the ever flowing water from the Colorado River was sufficient for
bathing. The women would drape a wet cloth over baby cradles to cool them. Fresh milk was no option and
canned food was the only way to avoid spoilage.
Times were tough and harsh on everyone, but especially on the black workers and their families. In
the 1930s racism and segregation was rampant and the attitude of the Six Companies, Inc. was no exception.
Many blacks came to Las Vegas and Black Canyon with hopes of fmding dam building jobs and most were
turned away. The federal government mandated that Six Companies, Inc. hire more black workers but they
made only a token effort by hiring less than 30 blacks and they were given only the most demeaning jobs
such as debris cleanup and other labor functions undesired by white workers. To make the difficulties
facing the black workers worse they weren't allowed to live in Ragtown and had to commute daily from Las
Vegas.
Six Companies, Inc. also had employment practices that expressly restricted the hiring of
"chinamen" and in spite of an abundance of Native Americans in the region just a few were ever hired. All
of them were given the most dangerous ofjobs, which was "high scaling" dangling precariously on the
canyon walls while clearing obstructions for the eventual joining of dam ends to those canyon cliffs.
However, they were paid a higher hourly rate versus generallaborers and were permitted to live in
Ragtown, which eventually became Boulder City.
Boulder City thrives today as a quiet town that overlooks Lake Mead and rides high above Hoover
Dam. Many of the "Ragtown Children" and their children are now actively involved in the community that
provides some of the most rewarding quality of life in America.
2
WORKERS' STRIKE AT HOOVER DAM
Even under the best of conditions, dam building was tough, dangerous work.
Those working on the construction of Hoover Dam had to contend with other
factors that made their work more risky and trying. One was the searing, relentless
heat. The temperature at the work site would routinely soar to above 120 degrees
during the summer and plummet to well below freezing in the winter. An added
pressure felt by the workers was the insistence of supervisors and managers to
finish the job in record time. Millions of dollars were at stake. Six Companies, the
outfit building the dam, had agreed to a rigid government deadline--two and a half
years to divert the river or face steep fmes for every day they ran late. In the rush to
meet their deadline, Six Companies often sacrificed safety for speed.
Working seven days a week, dam workers were exposed to all manner of dangers:
carbon monoxide poisoning, dehydration, heat prostration, and electrocution from
carelessly placed electrical lines. To top it off, workers knew they had little
leverage to lobby for changes. With a quarter of the nation's work force idle, the
workers at Hoover Dam knew they were expendable.
Frank Anderson, a professional organizer for the radicallabor union, the Industrial
Workers of the World (IWW), had been dispatched to Las Vegas to recruit
members and stir up demands for better working conditions and higher pay.
Workers regarded Anderson and the IWW with suspicion and contempt. They
knew any affiliation with a labor group could result in their having no job to
complain about. Meanwhile, Six Companies, along with officials in Las Vegas
and elements within the Reclamation Service, made concerted efforts to discredit
and drive out the IWW. Frank Anderson was jailed on trumped up vagrancy
charges.
Workers reached a breakpoint during the summer of 1931, however. On August 7,
Six Companies reassigned a number of diversion tunnel workers to lower paying
jobs. Within hours, the entire work force went out on strike. Six Companies
contended that only 30 muckers, unskilled laborers who loaded broken rocks into
trucks, would be affected by the pay reduction. Workers decided that the time was
ripe, not just to protest the pay cut, but to list their grievances and issue demands.
Among them: that clean water and flush toilets be provided, that ice water be
readily available to workers, and that Six Companies obey all mining laws issued
by the States ofNevada and Arizona. Significantly, the striking mine workers also
voted to disassociate themselves from the IWW.
Upon reviewing the workers' demands, job supervisor Frank Crowe echoed the
feelings of his bosses in rejecting every one of them. The strikers made a last­
ditch appeal to the D.S. Secretary of Labor, William Doak, to intervene on their
behalf. He refused. Knowing they were beaten, and worried they might not get
their jobs back, the strikers voted to return to the dam site. Six Companies stood
by its pay cut, but pledged it would be the last. Additionally, efforts were made to
improve work conditions as additional lighting and water was made available, and
construction of living quarters in Boulder City was sped up.
1
FATALITIES AT HOOVER DAM
The most asked question is: How many people died building the dam?
There are several stories that I found that can be used depending on who is included as
having died on the project.
One popular number is 112. With this number you get 110 plus the story of the first and last
men to die on the project. It goes something like this. On December 20, 1922, lG. Tiemey,
a Bureau of Reclamation employee engaged in a geological survey from a barge in the
Colorado River fell in the river and drowned. Thirteen years to the day, on December 20,
1935, Patrick W. Tiemey, a Bureau or Reclamation employee and son of J.G. Tierney, fell
from one of the intake towers.
This version has a couple of problems. First, the dam was built from 1931 to 1935, so J.G.
Tiemey was not really involved in the "construction" of the dam. He was doing a geological
survey to decide where the dam would be built, but he was not the first person doing the
survey to die. On May 15, 1922, Harold Connelly, also fell off of a barge and drowned. So,
why isn't he considered the first person to die on the project. Well, for one thing it would
not make as good a story as the Tierney family. To get around this it is pointed out that
Connelly died while surveying a canyon upstream from the present site of the dam, while
both Tiemey's died in the canyon where the dam was eventually built.
Another common number is 96. There were 96 industrial fatalities during the construction
of the dam. Industrial fatalities includes deaths from drowning, blasting, falling rocks or
slides, falls from the canyon walls, struck by heavy equipment, truck accidents, etc.
Industrial fatalities do not include deaths from the heat, pneumonia, heart trouble, etc.
The second most asked question is: How many of those who died are buried in the concrete?
The answer is - none! There are no bodies buried in the concrete. The dam was built in
interlocking blocks, built on top of each other as they went. Each block was five feet high.
The smallest blocks were about 25 by 25 feet, and the largest blocks were about 25 by 60
feet. Concrete was delivered to the blocks in buckets, eight cubic yards at a time. After
each bucket was delivered five or six men would tromp around on the inside of the block,
packing down the concrete and making sure there were no air holes. These men were called
"Puddlers". Each time a bucket was emptied into the largest blocks the level of the concrete
increased by two to three inches. How can you lose a body in two to three inches of
concrete? Of course the smaller blocks did fill up faster. Each time a bucket was emptied
into the smaller blocks the level was raised about six inches. Even with six inches the nose
and the toes would have stuck out, and the puddlers would have seen them. There are no
bodies buried in Hoover Dam. In fact they call that a Dam Lie!
WAGES
NOTE: The amounts shown are per hour of work, and the men worked eight-hour days. If you see an entry
like .825 it means that person earned eighty two and a half cents per hour.
Wage
Wage
Job
Job
.875 to 1.00
Miners
.70
Shifters
.625
.625
Nippers
Chuck Tenders
Muck Machine operator
.50
1.00
Muckers
Muck Machine helper
Brakeman
.50
.50
Drill doctor
.70
Dumpmen
.50
.625
Compressor
operator
.625
Jackhammer men
.625
Greasemen
.50
Motormen
Electrician's
helper
.75
.50
Electricians
Pipefitter helper
.625 to .75
.50
Pipefitter
.625
Blacksmith
.625 to .75
Pipemen comp. line
Blacksmith helper
.50 to .625
Machinist.75
.75
Mechanic's helper
.50
Mechanic
.75
Tool sharpener
.75
Sawfilers
.625 to .75
Welder's helper
.50 to .625
Welder
Riggers
.625 to .75
Truck drivers (Ford) .50 to .625
.625
Truck drivers (Moreland)
Truck drivers (Intl.)
.75
.75
Cat operator
Shovel operator
1.25
.625
Oilers
Carpenters
.70 to .75
Carpenter's helpers
.50
Carpenters, rough
.625
Cement finisher
.625
Laborers
.50
.625
.75
Boat operators
Steel sharpeners
.70
Powder men
Pumpmen
.625 to .70
Muck Machine doctor
1.00
American Crane operator
.75
The lowest wage was 50 cents an hour, and the highest was $1.25.
The average for all of the workers at the dam was about 62.5 cents an hour.
How does that compare to the rest of the country at that time? It was pretty good. Fifty cents an hour, eight
hours per day for a year works out to $1460.00.
The average 62.5 cents an hour works out to an annual income of$1825.00, and the
highest wage, $1.25, works out to $3650.00 per year.
It still does not seem like much until you compare it to what other people were making at that time. Below is
a table showing some comparisons on an annual
basis.
Wage
Job
Steel Worker
$422.87
$216.00
Hired Farm Hand
$1,373.00
Bus Driver
Engineer
$2,520.00
Lawyer
$4,218.00
Job
Coal Miner
Waitress
Civil Service Employee
Doctor
United States Congressman
Wage
$723.00
$520.00
$1,284.00
$3,382.00
$8,663.00
1
HIGH SCALERS
Millions of years of weather eroded the canyon walls. Water froze in cracks and crevices,
splitting the rock. Before construction could begin on the dam, this loose rock had to be
removed. Special men were chosen for the job, men called "high-scalers."
Their job was to climb down the canyon walls on ropes. Here they worked with jackhammers
and dynamite to strip away the loose rock. The men who did much of this work came from
many backgrounds. Some were former sailors, some circus acrobats, most were American
Indians who were told that if they wanted to work this was all that was
available for them. All of them had to be agile men, unafraid to swing out over empty space
on slender ropes.
It was hard and dangerous work, perhaps the most physically demanding work on the entire
project. Laden with tools and water bags, the men would descend the canyon walls.
Jackhammer drills were lowered to them, and powder holes were drilled into the rock. The
jackhammers weighed 44 lbs and had to be maneuvered into position by hand. Once the holes
had been drilled into the rock, they were loaded with dynamite. After the shot, broken rocks
sometimes had to be levered free using crowbars.
Moving about on the cliffs was difficult and hazardous. Live air hoses, electrical lines,
bundles of drill steel covered the cliff walls. The scalers had to carefully pick their way
through the resulting maze. The danger from falling rocks and dropped tools was extreme.
The most common cause of death during the building of the dam was being hit by falling
objects. The men began making improvised hard hats for themselves by coating cloth hats
with coal tar. These "hard-boiled hats" were extremely effective. Several men were hit by
falling rocks so hard that their jaws were broken by the impact, yet they didn't receive skull
fractures. Because of these "hard-boiled hats," men survived accidents, which would
otherwise have killed them.
After the strike The Six Companies. Inc. contracted for commercially made hard hats and
issued them to every man on the project. The use of hard hats was encouraged, and deaths
from falling objects were reduced. The risk and high visibility of the job lent it a certain
status, which appealed to some types of men. When the foremen weren't looking, they would
swing out from the cliffs and perform stunts for the workers below. Contests were held to see
who could swing out the farthest, the highest, or who could perform the best stunts.
It wasn't all done for fun and games, though. For several weeks, scaler Louis "The Human
Pendulum" Fagan transported a crew of shifters around a projecting boulder on the Arizona
side. The man to be transferred would wrap his legs around Fagan's waist, grasp the rope, and
with a mighty leap, they would sail out into the air and swing around the boulder. Fagan then
returned for the next man in the crew. This acrobatic transportation was accomplished again
at the end of each day to bring the men back to the other side of the boulder until the job was
finished.
Perhaps the most famous feat any of the high scalers ever performed was a daring midair
rescue. Burl R. Rutledge, a Bureau of Reclamation engineer, fell from the canyon rim.
Twenty-five feet below, high scaler Oliver Cowan heard Rutledge slip. Without a moment's
hesitation, he swung himself out and seized Rutledge's leg. A few seconds later, high scaler
Amold Parks swung over and pinned Rutledge's body to the canyon wall. The scalers held
Rutledge until a line was dropped and secured around him and the shaken engineer was
pulled, unharmed, to safety.
DOG ON A CATWALK
On the canyon wall, just across from the escalator leading to the new Tour Center at Hoover Dam, is a
plaque dedicated to a dog. Puzzled visitors often ask the guides and guards why the plaque is there.
The answers to these questions help keep alive the saga of the fIrst and only Hoover Dam mascot.
Details of the mascot's birth are a bit obscure, but Morgan Sweeney and Blackie Hardy agreed that he
was born under the Six Companies No. 4 barracks, and they should know. Mr. Sweeney was with the
commissary section supplying the food to the workers during construction and Mr. Hardy drove one of
the huge transports that hauled the workers from Boulder City to the dam site. After construction of
the dam, Mr. Hardy worked as a guide at Hoover Dam.
The dog's rough black puppy fur did not smooth out entirely as he matured and he never quite grew up
to his outsized paws, but perhaps these odd characteristics helped to endear him to the workers. He
was hardly weaned when Mr. Hardy picked him up one morning and tossed him on the transport.
When the dog fIrst saw the dam, he knew that was where he belonged. It became his life. The only life
he ever knew or wanted. Every morning he boarded a transport and put in a full days work along with
the other workers.
He inspected everything daily. As the dam rose higher and higher he had to ride the skips, a type of
open-air elevator, to cover the ground. When he wanted to board a skip, he barked, and the operators
always stopped for him. The mascot would hop aboard and bark again at the level where he wished to
get off.
Trainers will tell you that one of the most difficult tricks to teach an animal is to get them to walk on
any swaying, unstable surface, but Hoover Dam's mascot raced happily back and forth across the
swinging catwalks slung across the canyon seven hundred feet above the Colorado River.
The Hoover Dam mascot was not a one-man dog. He had no master. He belonged to the dam and
everyone connected with it, and they all belonged to him! If he decided to work overtime at his
favorite job of chasing ring-tailed cats that infested the tunnels, he hitched a ride back to town in the
fIrst Bureau of Reclamation or Six Companies car, truck or transport that happened along. No one ever
remembers him accepting a ride from anyone not connected with the dam. How he could differentiate
between dam workers and casual visitors no one could fIgure out, but it is a known fact that he did.
Everyone wanted to feed the dog, and being a dog, he found it hard to refuse. He became quite sick.
The worried workers then decided that the dog needed supervised feeding. Arrangements were made
with the commissary for the dog to be fed and word was passed to all workers not to offer him any
more food.
The commissary packed a lunch for him every day and he soon learned to carry it in his mouth when
he boarded the transport. At the construction site, he placed the sack alongside the workers' lunch pails
1
and went about his business. When the whistle blew, the dog raced for his sack and sat patiently until
someone opened it for him.
Workers leaving the job frequently stopped at the commissary and left a few dollars with the manager
- "Just to see that the dog gets fed well." These contributions soon grew to a respectable sum and a
bank account was opened for the Hoover Dam mascot.
The money paid for his food, dog license, and some sleeping baskets (which he never used) and silver
collars that he detested. Sometimes these collars were stolen by souvenir hunting tourists.
The fund also paid for advertisements in the Boulder City and Las Vegas papers, such as this one.
I Love Candy But It Makes Me Sick.
It Is Also Bad For My Coat.
Please Don't Feed Me Any More.
Your Friend, The Hoover Dam Mascot
One evening, Chief Ranger Peterson was notified that a group of workers was beating a man to death.
ChiefPeterson dashed to the scene and broke it up. When he learned the cause of the riot, the Chief
told the victim he would like to see the job finished but it was his duty to stop it. The Chief escorted
the bloody and bruised man to the town limits and told him never to come back. The man had made
the near-fatal mistake of kicking the Hoover Dam mascot.
After the dam was completed, the dog took it upon himself to see that the rule "NO DOGS
ALLOWED LOOSE ON DAM" was rigidly enforced. His ironclad insistence on the letter of the law
caused some embarrassment to members of the Guide Force, but these skilled diplomats always
managed to convince indignant pooch owners that the mascot actually owned the dam. The Bureau of
Reclamation merely built and operated it for him.
On a day when the blazing desert sun, combined with a blast furnace wind, pushed the thermometer
over the 120-degree mark, the dog found a spot of shade under a truck. The driver never noticed the
sleeping dog when he started up and drove off.
News of the fatal accident was phoned to town and it was the quietest afternoon Boulder City ever
experienced. Later, rough, tough, hard rock men wept openly and unashamed as they slammed their
ear-shattering jackhammers into the hard rock cliff, carving out the grave, which was to be the Hoover
Dam mascot's tomb.
So, in death as in life, the Hoover Dam mascot looks upon the dam he loved for as long as it will stand
and when the wind howls around the towers ofthe dam, the old-timers smile knowingly. It isn't wind.
It's the dog baying at the ring-tailed cats.
2
BUILDING THE DIVERSION TUNNELS
Before actual Hoover Dam construction could begin, the Colorado River had to be temporarily
diverted around the dam construction site. It was a daunting, difficult project. At that time there
were no roads into Black Canyon, so initially, dam workers and equipment had to be brought by
boat. Over time, roads were built and catwalks were stretched across the river. Summer
temperatures often reached 140 degrees in the canyon and the winter months brought freezing.
Carving the diversion tunnels was a slow, tedious process that exposed dam workers to immense
danger from blasting, falling rocks and diesel gas fumes spewed by the trucks that carried out
blasting debris. Compressed air was circulated into the tunnels through large pipes. However,
despite the difficulties, through intramural competition of the crew shifts, the tunnels would be
completed almost a year early.
But in the beginning, it took countless men to make even an inch penetration into the canyon walls.
To quicken the process, a drilling "Jumbo Truck" was retrofitted with layers of platforms that were
backed into the face of canyon walls. This enabled 20-30 men to simultaneously drill holes for
blasting powder. Eight of these jumbo trucks were implemented and lights were installed
permitting around the clock progression.
The blasting holes were filled with dynamite with a ton of dynamite used for about every 14 feet of
tunnel. After explosion, dump trucks hauled the rock debris downriver and placed in spoil dumps
along the canyon for later use. The diversion tunnels were lined with intricate forms for concrete
lining. Initially a base of concrete was poured. The sidewalls were then poured into moveable
sections of steel form and rail directed cranes were used to place the concrete. Pneumatic concrete
guns were used to fill the overhead forms resulting in a total concrete lining that was 3 feet thick..
Previously, a barrier across the inlets to the Arizona side tunnels was installed. When the Arizona
tunnels were ready to accept water flow, the barrier was breached with explosives and the flow
began through those tunnels. Earthen and rock debris were trucked in and dumped from a trestle to
block the Colorado River channel which forced the flow of water into the diversion tunnels.
Eventually, cofferdams were built at the entrance to the other tunnels so they all worked as a team
to divert water around the Hoover Dam construction site.
The core heart of Hoover Dam construction was now ready to begin.
1
THE COFFERDAMS
To isolate the construction site, and protect it from flooding, two cofferdams were
constructed. Construction of the upper cofferdam began in September, 1932, even though the
river had not yet been diverted. A temporary horseshoe-shaped dike protected the cofferdam
on the Nevada side of the river. After the Arizona tunnels were completed, and the river
diverted, the work was completed much faster.
The upper cofferdam was located approximately 600 feet down river from the inlet portals of
the diversion tunnels. Before the cofferdam could be constructed, 250,000 cubic yards of river
silt had to be removed to provide a firm foundation.
When completed, the upper cofferdam stood 98 feet high, and reached about 30 feet above the
top of the diversion tunnels. The dam was 450 feet long, 750 feet thick at the base and
contained 516,000 cubic yards of earth and 157,000 cubic yards of rock. The upstream face
was protected by a 6" thick concrete paving laid over 3' of rock blanket. The downstream face
was covered by a thick rock fill.
This cofferdam was designed so that if the diversion tunnels were discharging water at
200,000 cubic feet per second, the water would still be 13 feet below the crest of the
cofferdam (200,000 cubic feet per second was the largest flow of water ever recorded through
Black Canyon).
Work on the lower cofferdam was delayed while the high-scaling ofthe canyon walls above
the sites of the power plant and outlet works was completed.
The lower cofferdam was built of a compressed earth fill. It was 66 feet tall, 350 feet long and
550 feet thick at the base. The cofferdam contained Approximately 230,000 cubic yards of
earth, and another 63,000 cubic yards of rock. A thick rock fill covered the downstream side
of the cofferdam.
Because the lower cofferdam was made of a soft earth fill, there was concern that during
floods, back washing from the outlet portals would damage the cofferdam.
To lessen the force ofthe water, approximately 350 feet down river from the lower cofferdam
a rock barrier was built. This barrier was 54 feet high, 375 feet long and 200 feet thick at the
base. It contained approximately 98,000 cubic feet of rock.
The cofferdams, rock barrier, and diversion tunnels were all completed before the spring
floods of 1933. The engineers watched nervously to see if the dams would hold. They did, and
the diversion tunnels easily handled the flood waters.
The work of actually building Hoover Dam could begin.
THE CONCRETE
Concrete consists of four ingredients-sand and crushed rock aggregate, water and Portland
cement. These must be mixed in the proper proportions to yield strong concrete. Aggregate is
perhaps the most important of the materials in the concrete because it makes up as much as
three quarters of the Dam's mass. The aggregate must be clean and free of clays, salts and
organic matter. A source of aggregate near the Dam was needed so that it would not have to
be transported too far.
Bureau of Reclamation prospecting parties searched the desert around Black Canyon for
months, looking for a good supply of aggregate. Eventually, an alluvial lens just over six
miles upstream on the Arizona side of the river was chosen as the source. Here, floodwaters
had been depositing stones for millions ofyears. Some of the rounded stones were as much as
12" in diameter and had been washed down from as far away as the Grand Canyon. The
deposit covered more than 100 acres thirty to thirty-five feet deep.
A dragline was used to excavate the aggregate and load it into rail cars. The cars hauled the
aggregate to a screening and washing plant on the Nevada side of the river at Hemenway
Wash.
At the screening plant, four screening towers separated the aggregate into different sizes; fine,
intermediate and coarse gravels, and cobbles 3-9" in diameter. Anything over 9" was run
through a crusher and screened again. The separated gravel and cobbles were carried to the
mixing plants by train.
The initial concrete required for the dam was mixed in a river-level mixing plant, which was
located approximately 3/4 of a mile upriver from the dam site. This plant provided the
concrete for the linings in the diversion tunnels and for the lower levels of the dam. It went
into operation on March 3, 1932. The concrete was loaded into buckets which were
transported to the site initially by truck. Eventually, the concrete buckets were transported by
electric trains. For the first year of operation, nearly all of the concrete produced at this plant,
almost 400,000 cu. Yds. went into the linings of the diversion tunnels. In the tunnels, the
concrete buckets were moved by a gantry crane, which ran on rails from one end of the tunnel
to the other.
The first concrete was placed into the dam on June 6, 1933. The concrete was placed in the
dam using 4 and 8 cu .yds. bottom dump buckets. These buckets were lifted from the cars and
lowered into place by overhead cable ways. There were a total of nine of these cable ways
used to place the concrete. Five of the cable ways were connected to moveable towers, which
allowed them to be repositioned to work on different parts of the dam when necessary.
As the dam rose in height, a new concrete mixing plant was constructed on the canyon rim.
Completely automated, the hi-mix plant measured ingredients, mixed and dispensed the
concrete. It was capable of producing 24 cu. yd. of concrete every three and a half minutes.
The hi-mix plant was used to produce all of the concrete placed in the dam above the 992 foot
level.
1
One of the problems was that in order to produce the strength concrete required, a very dry
mix had to be used. There was very little time available to move the concrete from the mixing
plant to the dam. If too much time was taken, the concrete would take its initial set still in the
dump buckets and would have to be chipped out by hand. For this reason, the men who
operated the cranes which moved the buckets into place were some of the highest paid
workmen on the project, earning $1.25 per hour. As each bucket was dumped, seven puddlers
used shovels and rubber-booted feet to distribute the concrete throughout the form and
pneumatic vibrators to ensure there were no voids.
As the dam began to rise to fill the canyon, it grew in fits and starts. Rather than being a
single block of concrete, the dam was built as a series of individual columns. Trapezoidal in
shape, the columns rose in five foot lifts.
The reason that the dam was built in this fashion was to allow the tremendous heat produced
by the curing concrete to dissipate. Bureau of Reclamation engineers calculated that if the
dam were built in a single continuous pour, the concrete would have gotten so hot that it
would have taken 125 years for the concrete to cool to ambient temperatures. The resulting
stresses would have caused the dam to crack and crumble away.
It was not enough to place small quantities of concrete in individual columns. Each form also
contained cooling coils of 1" thin-walled steel pipe. When the concrete was first poured, riVer'
water was circulated through these pipes. Once the concrete had received a first initial
cooling, chilled water from a refrigeration plant on the lower cofferdam was circulated
through the coils to finish the cooling. As each block was cooled, the pipes of the cooling
coils were cut off and pressure grouted at 300 pounds per square inch by pneumatic grout
guns.
To prevent the hairline fissures between the blocks from weakening the dam, the upstream an
downstream faces of each block were formed with vertical interlocking grooves; the faces
turned toward the canyon walls with horizontal vertical grooves. When the concrete had
cooled, grout was forced into these joints, bonding the entire structure into a monolithic
whole.
Hoover Dam was the first man-made structure to exceed the masonry mass of the Great
Pyramid of Giza. The dam contains enough concrete to pave a strip 16 feet wide and 8 inches
thick from San Francisco to New York City. More than 5 million barrels of Portland cement
and 4.5 million cubic yards of aggregate went into the dam. If all of the materials used in the
dam were loaded onto a single train, as the engine entered the switch yards in Boulder City,
the caboose would just be leaving Kansas City, MO. If the heat produced by the curing
concrete could have been concentrated in a baking oven, it would have been sufficient to bake
500,000 loaves of bread per day for three years.
NAMING HOOVER DAM
By the time it was officially dedicated on September 30, 1935, the colossal dam
project on the Southern Nevada portion of the Colorado river had been called by several
different names. In the exploratory stage, the project was referred to as the Boulder Canyon
Project. Boulder Canyon, was replaced by Black Canyon, when Black Canyon was
discovered to be a more suitable spot to place the dam. Having started its legislative life
under the moniker of Boulder Canyon, the dam project simply adopted the title Boulder
Dam.
All of that changed, temporarily at least, on September 17, 1930, when Secretary of
the Interior Ray Lyman Wilbur journeyed to the Nevada desert to drive the spike marking
the project's official start. Sweating profusely through his inappropriate wool suit, Wilbur
announced, "I have the honor and privilege of giving a name to this new structure. In Black
Canyon, under the Boulder Canyon Project Act, it shall be called the Hoover Dam. " Hoover
was Wilbur's boss and the current president of the United States, Herbert Hoover. He was
also, in Wilbur's estimation, "the great engineer whose vision and persistence, first as
chairman of the Colorado River Commission in 1922, and on so many other occasions since,
has done so much to make [the Hoover Dam] possible. "
Wilbur's unofficial dedication was greeted with much derision, seeing whereas the
country at the moment was suffering through a crippling depression for which many citizens
placed blame squarely on Hoover's shoulders. The naming of a momentous public works
project in his honor was seen by many as bald-faced public relations and little more. Even
after Wilbur's proclamation, the dam was referred to in the press by both names, but it was
called Hoover in all official documents and congressional appropriations bills.
When Hoover lost the White House to Franklin Roosevelt in 1932, Wilbur lost his position
as Interior Secretary to Harold Ickes. Shortly thereafter, Hoover also lost his dam. On May
8, 1933, Ickes decided that the dam in Black Canyon would revert to being called Boulder
Dam. Ickes defended his decision by stating, "The men who pioneered this project knew it
by this name." He failed to mention that Herbert Hoover was one of those men.
Few doubted that Ickes' action was politically motivated and personally charged; he
didn't like Hoover and rejected the notion of his name being attached to any project that
would be regarded with honor. Ickes carried his snubbing of Hoover all the way to the day
of the dam's dedication. "This great engineering achievement," Ickes said, "should not carry
the name of any living man but, on the contrary, should be baptized with a designation as
bold and characteristic and imagination stirring as the dam itself" Ickes failed to mention
that dam sites named after Presidents Woodrow Wilson, Theodore Roosevelt, and Calvin
Coolidge already existed in Alabama and Arizona. For his part, Hoover, in his memoirs,
maintained that having the dam stripped ofhis name was unimportant.
Twelve years later, Hoover was vindicated when House Resolution 140 was introduced
and passed by the 80th Congress. The resolution read, in part, "as President, Herbert Hoover
took an active part in settling the engineering problems and location of the dam in Black
Canyon..." and noted that "the construction contracts were signed under his administration,
and when he left office construction had been pushed to a point where it was more than a
year ahead of schedule. " On April 30, 1947, President Harry S Truman signed the resolution
and restored the name Hoover Dam to the structure.
1
POWER DEVELOPMENT
The power plant is located in a V-shape structure at the base of the dam. Each power
plant wing is 650 feet long, 150 feet above normal tailrace water surface, and 299
feet (nearly 20 stories) above the power plant foundation. In all of the galleries of
the plant there are 10 acres of floor space.
The capacity of the Hoover Power plant is massive to say the least. There are 17
main turbines in Hoover Power plant. The original turbines were all replaced
through an uprating program between 1986 and 1993. With a rated capacity of
2,991,000 horsepower, and two station-service units rated at 3,500 horsepower each,
for a plant total of 2,998,000 horsepower, the plant has a nameplate capacity of
2,074,000 kilowatts. This includes the two station-service units, which are rated at
2,400 kilowatts each.
One of the questions asked most often is, 'what is horsepower in terms of falling
water?' The short answer is - One cubic foot of water falling 8.81 feet per second
equals one horsepower at 100 percent efficiency.
The water reaches the turbines through four pressure penstocks, two on each side of
the river. Shutoff gates control water delivery to the units. The turbines operate
under a Maximum head (vertical distance water travels), of 590 feet; minimum, 420
feet; average, 510 to 530 feet.
Power installations in the plant was completed in 1961 with the uprating completed
in 1993. There are fifteen 187,000 horsepower, one 100,000 horsepower, and one
86,000 horsepower Francis-type vertical hydraulic turbines. There are thirteen
130,000 kilowatt, two 127,000 kilowatt, one 61,500 kilowatt, and one 68,500
kilowatt generators. All these machines are operated at 60 cycles.
There are also two 2,400 kilowatt station-service units driven by Pelton water
wheels. These provide electrical energy for lights and for operating cranes, pumps,
motors, compressors, and other electrical equipment within the dam and power plant.
The power plant machinery was transported from the canyon rim to the power plant
by an electrically operated cableway of 150 tons rated capacity, with a 1,200-foot
span across the canyon, lowered all heavy and bulky equipment. The cableway is
still used when necessary.
The average annual net of energy generation for The Hoover Power plant for
operating years 1947 through 2000 is about 4 billion kilowatt-hours. The maximum
annual net generation at Hoover Power plant was 10,348,020,500 kilowatt-hours in
1984, while the minimum annual net generation since 1940 was 2,648,224,700
kilowatt-hours in 1956. A kilowatt-hour is a unit of work or energy equal to that
done by one kilowatt of power acting for one hour. A kilowatt is 1,000 watts or 1.34
horsepower.
The power plant is operated and maintained by the Bureau ofReclamation and the
principal contractors for energy are the States ofArizona and Nevada; the City of
Los Angeles; the Southern California Edison Co.; the Metropolitan Water District of
Southern California; the California cities of Glendale, Burbank, Pasadena, Riverside,
Azusa, Anaheim, Banning, Colton, and Vernon; and the city of Boulder City,
Nevada.
PTO
1
Hoover Dam firm energy generated is allocated as follows:
Arizona - 18.9527 percent
Nevada - 23.3706
Metropolitan Water District of Southern California - 28.5393 percent
Burbank - 0.5876 percent
counties in
Glendale -1.5874 percent
Pasadena - 1.3629 percent
California
Los Angeles - 15.4229 percent
Southern California Edison Co. - 5.5377 percent
Azusa - .1104percent
Anaheim - 1.1487 percent
Banning - 0.0442 percent
counties in
Colton -0.0884 percent
California
Riverside - 0.8615 percent
Vernon - 0.6185 percent
Boulder City, Nevada - 1.7672 percent
The income from the sale of energy used is used to pay all operation and
maintenance expenses and to repay the major part of the construction cost of the dam
and power plant, at interest not exceeding 3 percent.
The cost of construction completed and in service by 1937 was finally repaid on May
31, 1987. All other costs, except those for flood control, will be repaid within 50
years ofthe date of installation or as established by Congress. Repayment ofthe $25
million construction cost allocated to flood control is currently deferred. In addition,
Arizona and Nevada each receive $300,000 annually in lieu oftaxes.
2
SPILLWAYS
Many people who take the tour here at Hoover Dam want to know when they will get to see the water go
over the top of the dam. Well, the water has never gone over the top of the dam and probably never will.
We don't want the water to go over the top of the dam for a couple of reasons. First, the power house is
located at the foot of the dam. The power house contains 17 large generators, each producing enough
electricity to service about 100,000 people. All that water would be bad for the electrical generators (water
and electricity don't play well together). Second, there are about 18,200 vehicles a day going across the top
of the dam, and we don't want those vehicles to get swept away. The road across the top ofthe dam is a
federal highway, and it is the shortest way to get from Las Vegas to points east.
Water will probably never go over the top of the dam due to the spillways. The spillways workjust like the
overflow hole in your bathtub or sink at home (if you don't remember seeing that hole, go look for it right
now). If the water ever gets up that high, it will go in the hole and down the drain, not over the top and onto
the bathroom floor (unless, you have children and they plugged up the hole). The spillways are located 27
feet below the top of the dam, one on each side of the dam. Any water getting up that high will go into the
spillways then into tunnels 50 feet in diameter, and 600 feet long which are inclined at a steep angle and
connect to two of the original diversion tunnels. Each spillway can handle 200,000 cubic feet per second
(cfs) of water. The flow at Niagara Falls is about 200,000 cfs, so there is the potential for two Niagara Falls
here.
Each spillway has four steel drum gates, each 100 feet long and 16 feet high. These gates can't stop the
water going into the spillway, but they do allow an additional 16 feet of water to be stored in the reservoir
Each gate weighs approximately 5,000,000 pounds. Automatic control with optional manual operation is
provided for raising and lowering the gates. When in raised position a gate may be held continuously in that
position by the pressure of water against its bottom, until the water surface of the reservoir rises above a
fixed point, when by action of a float the gate is automatically lowered. As the flood peak decreases, the
gate can be operated manually so as to gradually empty the flood control portion of the reservoir without
creation of flood conditions down stream. The spillways have been used twice. The first time, in 1941, was
a test of the system. The second time, in 1983, was for a flood.
The Arizona spillway was placed in operation for the first time on August 6, 1941, soon after the reservoir
level had reached a maximum elevation of 1220.44. The drum gates were raised for several hours on
August 14, 1941, and a hurried inspection revealed that the tunnel lining was intact, and the inclined portion
showed little or no signs of erosion at that time. Operations were then continued without interruption until
the reservoir level had been lowered to elevation 1205.60 on December 1, 1942. The average discharge
flow through the Arizona spillway during this period was approximately 13,500 cfs with a maximum flow
of 38,000 cfs on October 28, 1941, when one of the drum gates dropped without warning.
That much water falling 600 feet down a very steep tunnel caused erosion of the tunnel lining The eroded
area was approximately 115 feet long and 30 feet wide, with a maximum depth of approximately 45 feet.
The original volume of the cavity was 1069.6 cubic yards. Repair work was started almost immediately, but
because it was believed that ordinary concrete was not suitable it was decided to utilize the Prepack and
Intrusion process of concrete repair developed by the Dur-ite Company of Chicago, IL. After repair, the
tunnel was polished smooth to help prevent future erosion.
During 1983, record flows into Lake Mead were recorded. The record surface elevation was recorded on
July 24, with more than two feet of water spilling over the raised spillway gates of Nevada and Arizona.
The record flows through the spillway tunnels again caused erosion in the concrete base, which had to be
repaired. High water was responsible for wide spread damage throughout the project.
1
JET FLOW GATE TESTING BRINGS A CROWD
"Jet flow gate testing" doesn't sound like an event that would bring reporters, cameramen, and news
helicopters out to Hoover Dam, located a fair distance from their regular news beats in downtown
Las Vegas. But in June, 1998, as a torrent of water sent whitecaps rippling down the Colorado, the
tests fascinated observers and garnered newspaper and television coverage from several local
media outlets.
Twelve obsolete needle valves were replaced with new jet flow gates in the outlet works at Hoover
Dam to meet criteria that require the dam to release 73,000 cubic feet per second without using the
spillways. Previously, the outlet works had a release capacity of about 50,000 cubic feet per second
(one cubic foot is 7.48 gallons).
The jet flow gates are devices that are designed to operate under high pressure. They include a steel
plate that can be raised or lowered to either prevent or allow water to be discharged from a
structure, much like the fancet in your sink controls the flow of water. The eight gates in the lower
valve houses are 68 inches in diameter and each is capable of discharging approximately 3,800
cubic feet per second (28,424 gallons per second) at the present lake elevation. When a gate is
closed, the force of the water behind it is 248 pounds per square inch, or 900,736 pounds per gate!
The four gates in the upper valve houses are 90 inches in diameter and each is capable of
discharging approximately 5,400 cubic feet per second (40,000 gallons per second).
The test was performed to obtain water release data from the new jet flow gates and ensure there
was no loss of efficiency to the generators during their operation.
The speed of the water coming out of each of the lower gates at maximum flow was
calculated at 120 miles per hour! At maximum opening, each gate discharged about
28,424 gallons of water per second. That's enough water to fill the average
backyard swimming pool in less than one second!
The upper gates are situated 180 feet above the river. Water from the gates
shoots across the canyon to strike the wall on the other side. The water exits
the gates at 120 feet per second, or 83 miles an hour. When all four upper gates
are in operation they could fill an Olympic size swimming pool, 500,000 gallons,
in three and a half seconds.
1
LAKE MEAD
Maximum length 120 miles
Surface area 247 square miles
Maximum depth 489 feet
Water volume Maximum: 26,134,000 acre feet
Current: 13,518,000 acre feet
Shore length 550 miles (the shore length is not a well-defined
measure due to increasing droughts.)
Surface elevation Maximum: 1,229 feet
Lake Mead is the largest reservoir in the United States in maximum water capacity. It is located on
the Colorado River about 30 mi southeast ofLas Vegas, Nevada, in the states of Nevada and Arizona.
Formed by the Hoover Dam, it extends 112 miles behind the dam, with the potential to hold approximately
26,134,000 acre feet of water when full. However, the lake has not reached this capacity in more than a
decade because of drought.
The lake was named after Elwood Mead (January 16, 1858 - January 26, 1936), who was the
commissioner of the U.S. Bureau of Reclamation from 1924 to 1936 during the planning and construction of
the 'Boulder Canyon Project' that created the dam and lake.
Lake Mead was established as the Boulder Dam Recreation Area in 1936, administrated by the
National Park Service. It was then changed to the Lake Mead National Recreation Area in 1964, this time
including Lake Mohave and the Shivwits Plateau under its jurisdiction. Both lakes and the surrounding area
offer year-round recreation options. The accumulated water from Hoover Dam forced the evacuation of
several communities, most notably St. Thomas, Nevada, whose last resident left the town in 1938. The ruins
of St. Thomas are sometimes visible when the water level in Lake Mead drops below normal.
At lower water levels, a high-water mark or "bathtub ring" is visible in photos that show the
shoreline of Lake Mead. The bathtub ring is white because of the deposition of minerals on previously
submerged surfaces.
The lake is divided into several bodies. The large body closest to the Hoover Dam is Boulder Basin.
The narrow channel, which was once known as Boulder Canyon and is now known as The Narrows and
connects Boulder Basin to Virgin Basin to the east. The Virgin River and Muddy River empty into the
Overton Arm, which is connected to the northern part of the Virgin Basin. The next basin to the east is
Temple Basin, and following that is Gregg Basin, which is connected to the Temple Basin by the Virgin
Canyon. When the lake levels are high enough, a section of the lake farther upstream from the Gregg Basin
is flooded, which includes Grand Wash Bay and the Pearce Ferry Bay and launch ramp. In addition, there
are two tiny basins, the Muddy River Inlet and the Virgin River Basin, that are flooded when the lake is high
enough where these two rivers flow into the lake. As of now, however, these basins remain dry.
Jagged mountain ranges surround the lake, offering somewhat of a startling but beautiful backdrop,
especially at sunset. There are two mountain ranges within view of the Boulder Basin, the River Mountains,
oriented north-west to south-east and the Muddy Mountains, oriented west to north-east. From the Virgin
Basin, you can view the majestic Bonelli Peak towards the east.
Las Vegas Bay is the terminus for the Las Vegas Wash which is the sole outflow from the Las Vegas
Valley.
Lake Mead's water level has fallen below the drought level (1125 feet above sea level) three times.
From 1953 to 1956, the water level fell from 1,200 to 1,085 feet. From 1963 to 1965, the water level fell
1
from 1,205 to 1,090 feet. Since 2000 through 2008, the water level has dropped from 1215 to 1095. In 2009
the water level rose slightly due to cool winter temperatures and rainfall.
In June 2010, the lake was at 39 percent of its capacity, and on Nov. 30,2010 it reached 1,081.94 ft,
setting a new record monthly low. From mid May 2011 to September 22,2011, Lake Mead's water
elevation increased from 1095.5 feet to 1115.24 feet, and the rivers feeding it were running at 128.06% of
the average flow rate for September 22.
Lake Mead draws a majority of its water from snow melt in the Colorado, Wyoming, and Utah
Rocky Mountains. Since 2000 the water level has been dropping at a fairly steady rate due to less than
average snowfall. As a result, marinas and boat launch ramps have either needed to be moved to another
part of the lake or have closed down completely.
The Las Vegas Bay Marina and the Lake Mead Marinas were relocated a few years ago to
Hemenway Harbor. Overton Marina has been closed due to low levels in the northern part of the Overton
Arm, Government Wash, Las Vegas Bay, and Pearce Ferry boat launch ramps have also been closed. The
marinas that remain open include Las Vegas Boat Harbor and Lake Mead Marina all sharing Hemenway
Harbor/Horsepower Cove, Callville Bay Marina, Echo Bay Marina, and Temple Bar Marina, along with the
Boulder Launch Area (former location of the Lake Mead Marina) and the South Cove launch ramp.
Changing rainfall patterns, climate variability, high levels of evaporation, reduced snow melt runoff,
and current water use patterns are putting pressure on water management resources at Lake Mead as the
population depending on it for water and the Hoover Dam for electricity continues to grow. A 2008 paper in
Water Resources Research states that at current usage allocation and projected climate trends, there is a 50%
chance that live storage in lakes Mead and Powell will be gone by 2021, and that the reservoir could drop
below minimum power pool elevation of 1,050 feet as early as 2017. Lake volume is now at the mercy of a
cascade of forces that include the fact that it is very likely impossible that the prevailing climate pattern of
profound drought will or can change to precipitation surcharge in a time frame shorter than that in which the
lake level will fall below the dead storage level of the downstream diversion and hydro-power intake
tunnels. However, water levels in the lake rose by more than 30 ft in 2011 due to a rainy winter and
increased snowfall in the Rocky Mountains.
Lake Mead offers many types of recreation to locals and visitors. Boating is the most popular.
Additional activities include fishing, water skiing, swimming and sunbathing. There are five marinas on the
lake: Forever Resorts at Callville Bay, Echo Bay, and Temple Bar Marina; and Las Vegas Boat Harbor
along with Lake Mead Marina in Hemenway Harbor which are family owned and operated. The area also
has many coves with rocky cliffs and sandy beaches. There are several small to medium-sized islands in the
lake area depending on the water level. In addition, the Alan Bible Visitor Center has a small cactus garden
of plants native to the Mojave Desert.
In 1948, while testing a prototype missile guidance system known as "Suntracker" a Boeing B-29
Superfortress crashed into Lake Mead and is still at the bottom of the lake as are the wreckages of at least
two smaller airplanes.
2
THE COLORADO RIVER BRIDGE
The Hoover Dam Bypass Project is a 3.5-mile corridor beginning in Clark County, Nevada and
crossing the Colorado River approximately 1,500 feet downstream of the Hoover Dam, then
terminating in Mohave County, Arizona. The increasing congestion caused by the switchbacks
leading to the Hoover Dam site and the restrictions at the dam crossing have led to the development
of the Hoover Bypass Project. The highway, which crosses over Hoover Dam, US 93, has been
designated a North American Free Trade Agreement route because of all the cargo transported
along this highway is one of the prime routes across the United states.
Now completed, this signature bridge spans Black Canyon which connects Arizona and Nevada
approach highways nearly 900-feet above the Colorado River. The Colorado River Bridge is the
central portion of the Hoover Dam Bypass Project.
Construction on the nearly 2,000 foot long
bridge began in late January 2005 and the completion of the entire Hoover Dam Bypass Project was
in June 2010.
The "Bypass" is a wonderful idea because it addresses several issues with one solution. The
increased traffic is a very practical reason for the bridge. The trucks carrying goods between the
states won't need to go over Hoover Dam highway making the trip faster and easier.
The security issues are obvious. There will no longer be a need to drive through Hoover Dam if
you are trying to go north or south on US 93 and trucks will no longer need to be checked before
crossing the Dam anymore except in extreme and unusual emergencies.
The traffic congestion due mainly to the trucks trying to cross the Dam will also be greatly reduced
making it more convenient for visitors. The current number of trucks and cars crossing Hoover
Dam is over 14,000, double from 15 years ago. The bridge will itself has become an attraction.
The two mega projects together side by side are a classic contrast in styles from two different eras.
The bridge has become the place to see Hoover Dam from and Hoover Dam will become the place
to see the bridge.
The final results of this project are interesting and unforeseen. The slow and difficult road which
crosses over Hoover Dam is a testament to the difficulty in building in this area in the first place.
By making Mojave County Arizona more accessible to those living in Las Vegas, they will travel
there and through there more often is part of Arizona is already seeing an increased and a faster
pace in development. Towns are expected to grow where none exist and around Las Vegas there
are already two new, growing towns, Laughlin and Primm. Property values have to started rising in
Northern Arizona because of the increased flow of traffic through and increasingly, to, this area.
One of the unforeseen benefits of Hoover Dam, the huge popularity of Lake Mead, was probably
never considered. The fact that there are nine to ten million visitors a year to Lake Mead would
probably seem unbelievable even to Herbert Hoover back in the 1920's. The simple elegance and
hugeness of this bridge lets it fit into, rather than clash with its surroundings.
1