Hoover Dam Construction: Boulder Dam (Part I) (1931) - CharlieDeanArchives / Archival Footage

or untold centuries the turbid waters of

the Colorado River battered their way

through the forbidding canyons of its

1,700 mile course traversing the arid

Southwest for the most part little known

except to the native Indians and a few

parties of intrepid explorers draining

the vast region of mountain and desert

entering seven of the largest western

states it poured its what her southward

into the Gulf of California carrying

into its Delta tremendous volume of silt

and periodically overflowing the

prosperous towns and rich agricultural

districts near its mouth with

devastating floods from the time of its

discovery it remained a challenge to

engineers who sought to control it until

the enactment in 1928 of the Boulder

Canyon project Act authorizing the

construction of Boulder Dam in Black

Canyon where the Colorado River forms

the boundary between Nevada and Arizona

in the very heart of the great desert of

the southwest

the United States Department of the

Interior through its Bureau of

Reclamation was directed to proceed with

the construction of this mightiest of

dams highways were pushed across the

desert railroad lines thrust their

ribbons of Steel to the sagebrush and

cactus and transmission lines for

construction power were brought hundreds

of miles across the heat stricken

wastelands of the Southern Nevada desert

every section of the country was called

upon to contribute to the staggering

quantity and wide diversity of material

required thousands of tons of Steel

millions of barrels of cement machinery

gasoline and oil but the thousands of

gallons tools building materials all

these and much more were concentrated at

the site of operations in an endless

stream the engineering forces completed

their surveys working under the most

hazardous conditions and every single

furnished its quota of laborers and

artisans in what had once been an

uninhabited one of us desert supporting

only a sparse inhospitable growth of

chaparral and cactus the beautiful

little town of Boulder City was built

within the short space of 15 months to

house the army of 5000 men to be

employed here was no construction camp

such as was known in the early days of

the West

instead Boulder City was developed as a

model town furnishing every facility and

convenience to its inhabitants for

churches a modern fully equipped school

and various civic organizations met the

cultural requirements of the community

while a theater and several clubs

furnished recreation a thriving business

section developed along the principal

streets while present homes surrounded

by Gardens faced the broad tree-lined

residential avenues of this modern

spotless town the building's housing the

offices of the Bureau of Reclamation and

the civic administration which operated

directly under the federal government

were set in the midst of Pleasant parks

which were welcome havens of rest after

the day's labors in a country where the

summer temperature often reaches a

hundred and twenty-five degrees above

zero in the business section of the town

arcades formed a protection against the

Tropic Sun lovely flower gardens bloomed

in marked contrast with the surrounding

desert lining Street after Street the

white cottages of the married workmen

recalled to mind the military camps of

1918 while single men were housed in

air-cooled dormitories each

accommodating a hundred and seventy-six

occupants under conditions which would

have gained the wholehearted approval of

any modern housewife tons of food were

prepared and served daily in the

sanitary electrically equipped kitchens

a corps of cooks and waiters was able to

feed as many as 1300 men at one setting

of the tables menus were buried and the

food was of excellent quality as Boulder

City was about seven miles distant from

the dam site it was necessary to provide

transportation for the workmen to and

from the job this was accomplished by a

fleet of passenger motor trucks some of

them carrying as many as 160 men a

24-hour day was divided into three

shifts of eight hours each for all

classes of labor the fourth of July

Labor Day and Christmas were the only

holidays observed once the rapid tempo

of the ambitious construction schedule

was established and underway toward the

marking of a record-breaking achievement

in American engineering history it was

in March 1931 that six companies

incorporated of San Francisco California

was awarded the General

contract for the construction of the

project including Boulder Dam and it's a

pertinent works and by early summer of

the same year preliminary construction

work was in full swing in Black Canyon

during this early period of construction

before roads had been built into the

depths of the gorge men and materials

were forced to take two boats or travel

the catwalks often swung between the

sheer walls of the canyon at dizzy

heights above the muddy waters of the

world's most dangerous river it was not

long before roads and rail lines had

penetrated into the very lowest reaches

of the canyon to provide these arteries

of transportation thousands of tons of

virgin rock were blasted from the

age-old walls of the gorge thus the

first thunders a man's determination to

conquer the Colorado River reverberate

it between the sheer cliffs of the

canyon which heretofore had known only

the hot silence of the desert and the

roar of the rivers angry floods the

boring of for diversion tunnels to carry

the stream around the dam site during

construction two on each side of the

river 56 feet in diameter and averaging

4,000 feet in length constituted the

first major construction operation the

drilling Jumbo's used on this job were

mounted on motor trucks to facilitate

handling and were capable of driving

from 24 to 30 powder holes into the

heading simultaneously by means of

drifter drills the tunnels were

excavated through the rocks

simultaneously from four headings one at

either end and too boring in opposite

directions from a river level auxilary

tunnel located about midway on the main

bore a pioneer drift was reeled at

top-line and closely followed by the

excavation for the complete 56 foot bore

thousands of tons of drill steel were

used in this work and the sharpening

shops were kept working at top speed

night and day to maintain the steady

supply after the powder holes had been

drilled and the Rock blasted power

shovels and trucks moved into the

tunnels for the purpose of removing the

shattered material an unbroken parade of

heavy duty trucks each handling from

eight to ten tons of rock labored up

over the steep roads cut into the canyon

walls to dispose of the material in the

gulches adjacent to the dam site

there's phase of the task which entailed

the excavation and the handing of over

one and a half million cubic yards of

material was completed within a period

of 13 months and was considered the most

grueling portion of the work for both

men and machinery after the tunnels had

been excavated they were lined with

concrete three feet and thickness due to

the unprecedented size of the bores

special equipment was designed to

facilitate this test the tunnels were

aligned in segmental sections the invert

or base being the first in which the

concrete was placed a gantry crane

operating through the tunnel itself

handled the concrete throughout this

operation the side walls were next line

behind movable steel forms which

traveled through the excavated section

on Rails laid from portal-to-portal the

top arch was placed with the use of a

concrete gun operated by compressed air

to prepare the canyon walls to receive

the abutments of the dam and to remove

loose and dangerous rock from the face

of the cliffs overhanging the site many

tons of rock were torn away and hurled

into the depths of the canyon in a

series of spectacular blasts which

occurred almost daily during the period

from commencement of operations at the

dam site to the time when actual

building of the dam began about two

years later deletes their positions on

the canyon walls the men engaged in the

work of drilling and handling explosives

for these huge blasts traveled in cages

or skips swung on cables at heights of

hundreds of feet over the river to the

casual observer this dizzy Sky Ride must

have seen thrilling indeed but to the

workmen themselves it became a matter of

course and all a part of the day's job

the first step in preparing for the

blast was the drilling of powder holes

into the rock to the canyon wall for

this purpose the jackhammer drill

operated by a single man was generally

used the holes were then loaded with

dynamite and the blast set off

shattering the air with its detonation

and shaking the very earth with its

force

after the blast these acrobatic workmen

known in construction camp parlance as

high scalars swarmed over the face of

the cliff to remove the fragments of

rock shattered and loosened by the

upheaval of the explosion only in this

manner could the walls be successfully

cleared of debris swinging in bosons

chairs from the canyons rim these

Daredevils were protected in their

hazardous work by art helmets safety

ropes and other safety appliances

November 1932 preparations were made to

divert the river through the tunnels a

small blast opened a breach in a

temporary dike which had held the river

in check at the entrance to one of the

tubes opening the way for the free

passage of the water into the 50-foot

concrete line for a temporary dam of

Earth and rock was quickly thrown across

the stream deflecting the entire flow

within 24 hours the Colorado River under

control for the first time in its

history was flowing around and past the

dam site through the huge diversion

views an all-time record was set in

placing the more than 1 million cubic

yards of material required for the

construction of the two copper dams in

themselves barriers of no mean

proportions the earth fields were

compacted to an elevation well above the

high-water mark to prevent the flow of

the river from entering the scene of

operations during the construction of

the dam and powerplant after the

completion of the copper dams the site

was unwatered and the fleet of power

shovels and trucks put to work on the

excavation of the riverbed material to

provide foundations for the structures

this excavation was carried to a point a

hundred and thirty-five feet below the

old river level necessitating the

handling of more than two million yards

of rock earth and sand here again the

stamina of both men and machinery was

put to a severe test in transporting the

waste from the very lowest depths of the

gore as the cleanup of the dam site

progressed the ancient band of the

Colorado River was laid bare here

geologists were able to read the story

of what had happened ages ago when the

chasm now called blackened

had been carved out of the primal rock

by the rush of water from a great Inland

Sea and the Colorado River was settling

into its present layer to ensure the

greatest possible stability for the

foundation of the dam meticulous care

was exercised in preparing the rock

surfaces for the reception of the first

concrete sand and gravel for the 4 and

1/2 million cubic yards of concrete

required for the construction of the dam

and as a pertinent works were obtained

from a detrital deposit located on the

Arizona side of the river some 12 miles

upstream from the dam site here the raw

material was excavated by dragline and

hauled by train to the gravel screening

and washing plant which was the largest

of its kind ever built being capable of

producing 20,000 tons of crushed

screened graded and washed materials

every 24 hours arriving at the plant the

raw material was dumped into hoppers

from which it was conveyed into the

plant over endless bells here it passed

through the various stages of screening

by which it became suitable aggregate

material for the manufacture of concrete

of a quality meeting the most rigidly

uniform requirements oversized cobbles

that is those measuring more than nine

inches in one dimension were first

screened out then crushed and returned

to the plant for regrading along with

raw material the screening plant itself

consisted of four towers of similar

design each equipped with screening

apparatus and each separating out gravel

of a different given size from the mass

of raw material reaching the unit over

the conveyor belts an endless stream of

raw get run gravel passed over the

screens and the selected material

carried to the stockpiles over the

conveyor belts each of the four sizes

being stocked separately ready at hand

when needed at the mixing plants a

clarifier tank provided 6 million

gallons of clear water daily for washing

gravel and sand raw material for

concrete manufacture which fell into the

size classified as sand was great at a

second time into three sizes after the

very fine and undesirable sand had been

discarded

the 3 selected sands were then

recombined into a uniform mixture to

meet specifications for the concrete to

be used in the dam and the effortless

structures of the project the sand was

then stored awaiting the requirements of

the construction program as the graded

materials were called for conveyor belts

loaded the sand and gravel into railroad

cars for transportation to the concrete

mixing plants located at the dam site

several mile distant concrete was mixed

in two plants one located in the bottom

of the canyon upstream from the dam and

the other on the canyon rim on a Nevada

side immediately over the dam site both

equipped with the most advanced

machinery for concrete manufacture upon

arrival at the concrete mixing plant

sand and gravel the various sizes were

stored in separate bins a railroad

system of sizeable proportions was

required to maintain a steady flow of

material from the gravel pit to the

screening plant and from the screening

plant to the concrete mixing plants bulk

cement was unloaded from railroad cars

by means of a pneumatic pump and

conveyed into the bins of the bending

plant where cement from several

production sources and a varying

physical and chemical characteristics

were combined into a uniform product

this was necessary because of the

requirement for Standardization in

concrete workability strength texture

color and other properties following the

progress of concrete manufacture through

its successive stages we see the several

ingredients entering the concrete mixing

plant where they were combined

scientifically and under rigid

inspection into a finished product with

a maximum capacity of 24 cubic yards of

concrete every three and 1/2 minutes the

high-level mixing plant at Boulder Dam

represented the ultimate in plant

installations of its kind here automatic

equipment not only controlled the

apportionment of the concrete

ingredients but in addition maintained a

graphic record of every plant operation

from his post on the control deck of the

mixing plant an operator was able to

direct the entire mixing cycle from the

initial weighing of the ingredients on

through the complete mixing process the

human element was almost completely

eliminated

as the mechanical equipment was capable

of automatically selecting measuring

weighing and recording the proper

materials in the precise amounts

required for the production of a given

mix to which the recording dials had

previously been adjusted and said here

also we find the production line

conveyor belt speeding up the process by

carrying the component parts from the

measuring and weighing hoppers into the

batching bins from which the materials

were dumped into the four cubic yard

capacity rotary mixers water was added

in controlled amounts and the entire

mass thoroughly agitated as the last

step in the economical and efficient

manufacture of a concrete strong enough

to withstand the enormous pressure to

which the dam would be subjected from

the mixing plant concrete was dispatched

to all sections of the works and because

of the widely varying conditions

prevailing various types of containers

and methods of transportation were

involved motor trucks and electric

trains were utilized as carriers and

containers varied from the eighth cubic

yard capacity bottom dump buckets to the

fourth cubic yard capacity transit

mixers the latter were used on long

hauls where it was necessary to agitate

the concrete in transportation to

prevent segregation of the mix however

the major portion of the concrete

handled on the project was carried in

the 8 cubic yard buckets and transported

from the mixing plants by electric train

a system of nine aerial cable ways

spanning the canyon from limb to limb

and anchored at either end to movable

towers was utilized to carry the

concrete and other materials from the

points of train or truck delivery to the

dam and other structures on the project

it was on June 6 1933 that the first

bucket of concrete was placed in the

very lowest of the dam forms 135 feet

below the level where a few months

previously had flowed the unchallenged

Colorado River what was to become the

highest dam in the world began to rise

from the unfindable rock of his

foundation as bucket after bucket of

concrete was dumped into the forms the

plan of the structure became apparent

and soon extended along its full 660

feet dimension of thickness at the base

throughout the lower levels of the

structure concrete was placed from a

trestle anchored to the Nevada wall of

the canyon the concrete was poured in

keyed or interlocking columns the design

of which became more noticeable as the

five-foot layers or lifts in which the

concrete was placed rose from level to

level as the work of placing progressed

the crews became expert in the handling

of the equipment and record-breaking

daily pours were made only to be

surpassed by later achievements on this

same structure transit mixers were

transported on trucks from the bed of

which they could be removed and handled

on the overhead cable waves these were

used in the placement of concrete in the

confined forms along the abutments where

the eighth cubic yard buckets could not

be handled selecting at random one

bucketful among the hundreds of

thousands that traveled from the canyon

rim over the cable ways and down into

the dam forms we see the typical

operation from the time the bucket is

picked up by the cableway on the canyon

rim swung out into midair over the gorge

hundreds of feet above the forms its

tremendous weight of 22 tons riding

easily and gracefully over the cable as

it is lowered into the forms with an

ease and certainty seemingly out of

proportion to its great vault

contaminant as the bucket descends

suspended at the end of hundreds of feet

of cable strands it is received at the

forms the safety locks unlatched the

signal given and eight more cubic yards

of concrete added to the dams both

concrete was compacted into the forms by

mechanical vibration the application of

which ensure dense compression against

adjacent surfaces workmen were carried

from the canyon rim to the dam forms by

way of the implyin skid way or a monkey

slide as it was called which operated

through the Nevada abutment excavation

Boulder Dam laborers represented a fair

cross-section of the American working

class and many stayed on the job during

the entire period of construction with

an ambitious progress schedule to meet

and with work going forward under all

conditions at all seasons of the year

without cessation rain or shine both day

and night within a year less or

two million of the three and one-quarter

million cubic yards of the dams total

volume had been placed in the forms and

Boulder Dam had risen to an impressive

height already having taken its place as

one of the wonders of the West and a

tourist attraction of prime importance

meanwhile progress had been made in the

erection of the structures of pertinent

to the dam itself the construction of

the power plant a u-shaped structure at

the downstream toe of the dam had been

in progress for some months and as is

substructures assumed form it gave some

hint of the beauty it was later to

possess the intake towers two on each

side of the canyon wall immediately

upstream from the dam or in course of

construction and from a maze of

reinforcing steel rapidly rising toward

the uppermost rim of the canyon

these structures were later to serve as

giant Inlet valves or the outlet

conduits and power penstock systems and

the placing of the seats for the mammoth

cylinder gates was an important phase in

their construction located at the

ultimate high water storage level of the

reservoir the two spillways designed to

act as overflow controls in the open

bypass system were located one on each

side of the river upstream from the dam

and within the reservoir area work on

their construction progressed

simultaneously with that of the dam

itself one of the most interesting and

spectacular phases of the work was the

fabrication and installation of the huge

steel penstock pipes forming the

conduits for the power and pressure

outlet systems this work was performed

by the Babcock & Wilcox Company of New

York City who erected a modern steel

fabrication mill near the dam site to

facilitate the undertaking as the pipe

units to be fabricated were of

unprecedented size and weight it was

necessary to design build and install

special machinery solely for this test

provisions were made to manufacture pipe

ranging in diameter from 8 and 1/2 to 30

feet from steel plates varying in

thickness from 5/8 of an inch to 2 and

3/4 inches

as it was impossible to ship units of

this size across country by rail steel

plate was brought from eastern rolling

mills and the entire process of

manufacture including rolling and

assembling was initiated and completed

at the Boulder Dam plan first step in

the fabrication process after the plates

had been laid out to dimension was the

shaping of the edges to ensure the

precision and accuracy of later steps in

their manufacture this work was done on

a planing machine capable of handling a

strip of Steel fifty feet in length the

plates were then given an initial ban on

a giant press operating at a pressure of

three thousand tons this initial pending

was necessary to avoid damaging the

rolls when the plates in the next step

of fabrication were rolled into circular

form the plates entering into the

manufacture of the 30 foot diameter

penstock pipe were fabricated through

the initial steps of manufacture in 11

foot widths these plates were 2 and 3/4

inches in thickness and were rolled into

circular form by being passed through 40

inch vertical rolls until the desired

degree of curvature had been obtained

one such plate represented a segment

equal to one-third of the complete

circumference of a finished pipe having

been rolled to the correct degree of

curvature the three curved plates were

joined to form a single ring 30 feet in

diameter and 11 feet long

- such rings were then joined end-to-end

to form a shop unit 22 feet long all

joints were made by electric welding and

in forming the longitudinal joints an

automatic welding machine traveling on a

chassis supported inline over the joint

was used as these part units were of a

size never before assembled it became

necessary to design and build special

machinery to accomplish many phases of

the work this was especially true in the

fabrication of mitered rings to be later

assemble into pen sections the general

usage of electric cutting and welding

was applied not only to pipe sections

but to the manufacture of other

fabricated units as well a complete shop

unit weighing from 150 to 180 4 tons

depending upon its design determined by

its ultimate use

upon installation in the power pen stock

system circumferential joints were made

by rotating the rings making up a shop

unit beneath an electric welding machine

suspended above the line of the joint to

be welded every foot of welded joint was

subjected to a searching examination by

x-ray and recorded on photographic film

which exposed even the slightest

imperfections in the continuity of the

well samples of typically welded joints

were subjected to severely rigid

laboratory tests calculated to produce a

condition of strain or in excess of that

to be borne by the joint under actual

usage the discovery of even the

slightest imperfection was sufficient

cause for the rejection of a complete

unit in marked contrast to the

meticulous care and precision exercised

throughout every phase of their

manufacture was the actual size and

weight of the pipe unit themselves

heavy-duty rigging of special design was

required to handle the sections through

the shop and high-capacity frames were

required to move them step by step

through the progressive phases of their

manufacture to equalize the terrific

internal strains introduced into the

plates by bending and the additional

temperature strains incurred during

welding individual pipe sections were

subjected to a temperature of 1400

degrees Fahrenheit a gigantic annealing

furnace this temperature was induced not

by the application of flame itself but

through the circulation of superheated

gas shop processes were carried only as

far as the production of the unit

section as these sections were to be

joined to form a continuous penstock

provision was made to accurately

accomplish this junction in the tunnels

to guarantee a satisfactorily tight feel

joint the ends of the sections were

machined on a mammoth vertical lathe

operating across the 30 foot diameter of

the pipe after a final inspection the

pipe section was ready for installation

a modern streamline train passing

through one of the huge tubes affords an

interesting gauge for the comparative

size of the units

now the transporting the pipe section

from the plant to the dam site was in

itself a tremendous undertaking and to

accomplish this work a special road

trailer capable of carrying 200 tons was

designed and built caterpillar tractors

furnish the motive power as the trailer

itself was not equipped with the means

of locomotion during handling the

conformation of the pipe section was

maintained by rigid internal bracing the

movement of the heavy trucks was

controlled by air brakes and power

steering apparatus with which the

trailer itself was equipped upon arrival

at the canyon rim directly over the dam

site the unit was maneuvered into

position for lowering into the canyon to

perform this task and to handle other

heavy equipment a permanent 200 ton

capacity cableway had been swung over

the gorge it's six three and a half inch

track cables securely anchored into the

rock of the canyon wall the cable wave

was manipulated from a control tower

overhanging the canyon from which the

operator commanded a full view of all

its movements the heavy hoisting

machinery controlled by synchronized

motors was the largest and most powerful

of its kind ever built as well also the

track cables themselves which spanned

the canyon a distance of twelve hundred

and fifty-six feet at an elevation of

700 feet above the river from the head

tower located on the Nevada side over

the track cables traveled the carriage

to which the hoisting and travelling

cables were played especially designed

heavy-duty rig which became known to the

workmen as the moon beam because of his

peculiar shape and from which the pipe

sections were suspended was used in

lowering the huge tubes into the bow

Devils of the canyon while cradled in a

sling of heavy steel cable after all

lashings were secured the pipe section

was lifted from the trailer to begin its

slow and carefully controlled movement

over the cable wave riding from the rim

out into space suspended 700 feet above

its ultimate position when the cable

carried with this tremendous weight of

steam had been maneuvered into location

over the intended landing far below the

hoisting cables were slowly played out

and the pipe lowered under absolute

control into the canyon here a second

specially designed car waited at the

portal of the access tunnel to relieve

the cableway of its burden and carry the

pipe section underground

to become a part of the extensive

conduit system penetrating the cliffs on

both sides of the canyon with the

workmen laboring in the tunnels far

underground the guardian task of placing

the penstock pipes in position to form

continuous conduits between the intake

towers and the powerhouse and outlet

works was accomplished the separate

units were hoisted into location with

the aid of cables and once placed in

position were joined with pressure pins

to form a continuous pipe while work on

the appurtenant features of the Boulder

Canyon project was in progress an

uninterrupted stream of concrete had

been pouring into the forms of the dam

from both mixing plants progress was

curtailed only by the limitations of

sound engineering and construction

practice day by day week after week the

tough workings of the structure

approached its full height of 730 feet

far above the crest of any other dam yet

built by man or likely to be built for

years to come

schedules established at the outset of

the work will left far behind as the

concrete of the dam narrowed toward his

crest and the structure widen between

its abutments approaching the very top

limbs of the Ken in June 1935 the dam

structure itself stood completed two and

one-half years in advance of the time

originally designated in September of

the same year President Franklin Delano

Roosevelt voicing high praise for both

designers and builders dedicated Boulder

Dam to the progress of the nation as

final construction work was completed

the impressive beauty of the structure

became apparent the roadway traversing

its 13 hundred foot Kriss forms a

magnificent link in a transcontinental

highway the reservoir filling behind the

dam was named Lake Mead in memory of dr.

Elwood me late Commissioner of

Reclamation whose life work culminated

in the building of Boulder Dam the

largest artificial body of water in the

world it extends upstream 115 miles into

the lower reaches of the Grand Canyon

with the shoreline of 550 miles opening

upon Vista Sun glimpsed by man until

invaded by the gradually rising waters

of the reservoir

equipped with cylindrical gates which

function as giant valves the poured

intake towers serve as Emmett's to the

four steel penstocks supplying water to

the turbines and outlet valves perched

on shelves Yeun into the canyon walls

they tower 403 feet to an elevation

above the crest of the dam and the rim

of the canyon with the combined capacity

of four hundred thousand cubic feet of

water per second the two spillways

located one on each side of the canyon

upstream from the dam will serve as

high-level controls once the water of

the reservoir has risen to its maximum

storage elevation each spillway is

equipped with four 100-foot drum gates

acting through a vertical dimension of

16 feet water flowing over the lower

gates into the spillway basin plunges

600 feet down through the tunnels to

reenter the river downstream from the

dam the Boulder Dam power plant is built

in two wings one along each side of the

canyon wall at the downstream toe of the

dam the first generator was placed in

operation on September 11 1936 equipped

with 17 generating units with capacities

range 40,000 to 80 mm 500 kilovolt

amperes this the world's largest power

plant is capable of generating one

million eight hundred and thirty-five

thousand horsepower of electrical energy

when operating at its rated capacity the

transmission lines carrying Boulder Dam

power radiate in a network from the dam

with the major line serving the Los

Angeles metropolitan area from the

take-off structure located on the roof

of the powerhouse the Lions are taken up

over the rim of the canyon into the

switchyard above where the most highly

specialized and modern developments in

the Power Transmission field are to be

found from the switchyard

the lines travel out across the desert

bringing life to the homes and cities

and power to the factories at Southwest

from Parker dam 150 miles to the south

the Colorado River aqueduct supplies the

city of Los Angeles with a domestic and

industrial water supply while from the

Imperial dam 300 miles to the south the

all-american canal diverts one in the

Colorado River

into the rich agricultural districts of

the Imperial Valley and Seoul Boulder

Dam stands today a modern Colossus

shouldering the rock-ribbed walls of

Black Canyon stemming and controlling

the floods and bending the will of a

hitherto unburnable stream the Colorado

River to perform the fruitful tasks of a

civilization rapidly invading the limits

of its last frontier

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