authorizing the construction of boulder dam in black canyon where the colorado river forms a 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 reclamation was directed to proceed with the construction of this mightiest of the highways were pushed across the desert railroad lines just there ribbons of steel through the sage brush and cactus and transmission lines for construction power were brought hundreds of miles across the heath stricken wasteland of the southern nevada desert every section of the country was called upon to contribute to the staggering quantity and wide diversity of materials required thousands of tons of steel millions of barrels of cement machinery gasoline and oil by the thousands of gallons tools building materials all these and much more were concentrated at the side of operations in an endless stream the engineering forces completed their surveys working with in the short space of fifteen months to house the army of five thousand men to be employed here was no construction camp such as was no one in the early days of the west instead boulder city was developed as a model town burnishing every facility and convenience to its inhabitants or churches a modern fully equipped school and various civic organizations met the cultural requirements of the community while a theatre and several clubs furnished recreation a thriving business section developed along the principal street while pleasant home surrounded by gardens face the broad daylight and residential avenues of this modern spotless south the buildings housing the offices of the order of reclamation  ministration which operated directly under the federal government where said in the midst of pleasant parts which were welcome havens of rest after the day's labors in a country where the summer temperatures are often reaches one hundred twenty five degrees above zero in the business section of the town arcades formed a protection against the tropics the 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 hundred eighteen while single man were housed in air cooled dormitories each accommodating a hundred and seventy six occupants under conditions which would have given the whole hearted approval of any modern housewife tons of food well prepared and served daily a sanitary elektra be equipped kitchen a court of cooks and waiters was able to feed as many as thirteen hundred men at one setting of the table menus were buried in the food was of excellent quality as motor city was about seven miles distant from the dam site it was necessary to provide transportation for the workmen to win from the job this was accomplished by a fleet of passenger motor drops some of them carrying as many as one hundred sixty men a twenty four hour day was divided into three shifts of eight hours each for all classes of labor the fourth of july labor day and christmas where the only holidays observed once the rapid temple 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 one nine hundred thirty one that six companies incorporated epstein's and cisco california was awarded the general contract for the construction of the project including boulder dam and as a part network and by early summer of this same year preliminary construction work was in full swing in black during this early period of construction before roads had been built into the depths of the gorge main and materials were forced to take two boats or travel the catwalk often swung between the sheer walls of the canyon at dizzying 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  to provide these arteries the plant's potations thousands of tons of virgin rock where blasted on the age old walls of the gold dust the first thunders of man's determination to conquer the colorado river reverberated between the sheer cliffs of the canyon which here length constituted the first major construction operation the drilling jumbos used on this job were mounted on motor drops to facilitate handling and we're capable of driving from twenty four to thirty power holes into the headings simultaneously by means of drift or drill the tunnels were activated through the rocks simultaneously from four headings one at either end then two boring in opposite directions from a river level auxiliary tunnel located about midway on the main bore a pioneer drift was real the top line and closely followed by the excavation for the complete fifty six football thousands of tons of real steel were using this work and the sharpening shops were kept working at top speed night and day to maintain a steady supply after the powder holes had been drilled and the rock lasted our shovels and trucks moved into the tunnels for the purpose of removing the shattered material and unbroken parade of heavy duty trucks each handling from eight to ten tons of rock labored up over th steep roads cut into the canyon walls to dispose of the material in the gulches adjacent to the dam site this phase of the task which entailed the excavation and the handling of over one and a half million cubic yards of material was completed within a period of thirteen 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 in thickness due to the unprecedented si of the boers special equipment was designed to facilitate this that the tunnels were lined in segmental sections the inverter or base being the first in which the concrete was placed again for a crane operating through the tunnel itself handled the concrete throughout this operation the side walls were next line behind movable steel forms which travelled through the excavated section on rails laden 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 remove loose and dangerous rock from the face of the cliff 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 sites to the time when actual building of the dam began about two years later to reach their positions on the canyon walls the man and gage in the work of drilling and handling explosives were these huge blast traveled in cages or skip swung on cable at heights of hundreds of feet over the river to the casual observer this disease skyride must have seemed 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 of a canyon wall for this purpose the jackhammer drill operated by a single man was generally you the holes where they unloaded with dynamite and the blast that all shattering the air with its detonation and shaking the explosion only in this manner could the walls be successfully cleared of debris swinging in both of those chairs from the canyon's ram these daredevils were protected in their hazardous work by a hard helmets safety ropes and other safety appliance nov nineteenth thirty two preparations were made to divert the river through the tunnels a small blast opened a breach in a temporary diet which it held delivered in check at the entrance to one of the tube opening the way for the free passage of the water into the fifty foot concrete line bore a temporary dam of earth and rock was quickly thrown across the stream deflecting the entire flow within twenty four hours the colorado river under control for the first time in its history was blowing around and past the dam site through the huge diversion to an all time record was set in placing the more than one million cubic yards of materials required for the construction of the two coffer dam in themselves barriers of no mean proportions the earth feels 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 power plant thirty five feet below the old river level as does the dating the handling of more than two million yards of rock earth and say here again the stamina of both man and machinery was put to a severe test in transporting the waste from the 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 day do ensure the greatest possible stability for the foundation of the dam meticulous care was exercise in preparing the rock located on the arizona side of the river some twelve miles upstream from the dam site here the raw material was excavated by greg life and hauled by train to the gravel screening and washing plant which was the largest of its kind ever built being capable of producing twenty thousand tons of crushed screamed great unwashed materials every twenty four hours arriving at the plant the raw material was dumped into the hopper from which it was conveyed into the plant over endless belt 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 acquired screening operators and each separating out gravel of a different given size from the mass of raw material reaching the units over the conveyor belt an endless stream of raul pits running gravel passed over the screen and the selected raw material for concrete manufacture which fell into the size classified as sand was graded a second time in two or three sizes after the very fine and undesirable stand had been discussed the three selected cyan where the recombined into a uniform mixture to meet specifications for the concrete to be used in the dam and the apartment structures of the project the sambos them stored awaiting the requirements of the construction program as the grade of materials were called for conveyor belts loaded the sand and gravel into railroad cars for transportation to the concrete mixing plans located at the dam site several miles distant concrete was mixed into place one located in the bottom of the canyon upstream from the separate them a railroad system of sizable 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 plant  by means of a pneumatic pump and conveyed into the bins of the binding plant where's demands from several production sources and of 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 another property following the progress of concrete manufacture through its successive stages we see the several ingredients entering the concrete mixing plant where they were installations of its cause here automatic equipment not only controlled the apportionment of the concrete ingredients but in addition maintain the graphic record of every planned operation from his post on the control deck of the mixing plan and operator was able to direct the entire mixing cycle from the initial weighing of the ingredients all 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 set 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 there from which the materials were dumped into the four cubic yard capacity rotary mixer water was added in controlled amounts and the entire mass thoroughly agitated as a 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 plants concrete was dispatched to all sections of the works and because of the widely a bearing 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 eight cubic yard capacity bottom like yard capacity transit mixer the latter were used on long haul where it was necessary to agitate the concrete in transportation to prevent segregation of the mix however the major portion of the concrete utilized to carry the concrete and other materials from the points of grain or truck delivery to the dam and other structures on the project it was on june sixth one nine hundred thirty three that the first bucket of concrete was placed in the very lowest of the dam for one hundred and thirty five feet below the level where the few months previously had flowed the unchallenged colorado river what was to become the highest them in the world began to rise from the ends by nable rock of its bound age as bucket after bucket of concrete was dumped into the forms the plan of the structure became apparent and soon extended along its full six hundred and sixty feet dimension of thickness at the base throughout the lower levels of the state ger concrete was placed from a  of the bed of which they could be removed and handled on the overhead cable way these where you lose in the placement of concrete and they can bind forms along the about where the eight cubic yard buckets could not be handled selecting at random one bucket from among the hundreds of thousands that travel down 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 mid air over the gorge hundreds of feet above the forms it's tremendous weight of twenty two tons riding easily and gracefully over the cable as it is lowered into the forms with unease uncertainty seemingly out of proportion as the bucket the sands suspended at the end of hundreds of feet of cable strands it is received at the for the safety locks on latched the signal given and eight more cubic yards of concrete added to the damage about 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 formed by way of the imply and get away or monkeys slide as it was called which operated through the nevada about what excavation motor 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 last four days two million of the three and one quarter million cubic yards of the dams total volume had been placed in the fall 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 has been made in the  structures apartment to the dam itself the construction of the power plant are you shaped structure at the downstream toll of the dam had been in progress for some months and that is substructures a human form it gave some hints of the beauty it was the structures were later to serve as giant inlet valves for the ultimate conduits and power penstock system 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 over of all controls in the open bypass this them were located one on each side of the river upstream from the dam and within the reservoir  work on their construction progress simultaneously with that of the damage so one of the most interesting and spectacular phases of the work was a fabrication and installation of the huge steel penstock pipes forming the co for the power and pressure outlet system this work was performed by the babcock and wilcox company of new york city who erected a modern steel fabrication mill near the dam site to be militate the undertaking as the five  ts to be fabricated one of unprecedented size and weight it was necessary to design build and install special machinery slowly for those that provisions were made to manufacture a pipe ranging in diameter from eight and one half to thirty feet from a steel plate varying in thickness from five eighths of an inch to two and three quarters inches as it was impossible to ship units of this size across country by rail steel plate was brought from the eastern rolling mill and the entire process  manufacture including rolling and assembling was initiated and completed at the boulder dam play first step in the fabrication process after the plates had been laid out the dimension was the shaping of the edges to ensure the precision and a steps and their manufacture this work was done on a planing machine capable of handling a strip of steel fifty feet in length a place where they were given an initial band on a giant p operating at a pressure of three thousand ton this initial bending 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 thirty foot diameter penstock pipe were fabricated through the initial steps of manufacture an eleven foot with these plates where two and three quarters inches in thickness and were rolled into a circular form by being passed through a forty inch vertical ro form a single ring thirty feet in diameter and eleven feet long to such rings were then joined and to and to form a shop unit twenty two feet long all joints were made by electric welding and in forming a longitud joint an automatic welding machine traveling on a chassis supported in line over the joint was you as these five units whatever size never before assembled it became necessary to design and build special machinery to accomplish many phases of the work machine suspended above the line of the joint to be welded every foot of weld a joint was subjected to a searching examination by x rays and recorded on photographic film which expose even the slightest imperfections in the continuity of the w samples of typically well the joints were subjected to severely rigid laboratory tests calculated to produce a condition of strain far in excess of that to be borne by the joint under actually the discovery of even the slightest imperfection heavy duty rigging a special design was required to handle the sections through the shop and high capacity claimed were required to move them step by step through the progressive phases of their manufacture to legalize the terrific internal strains introduced into the plates by bending and the additional temperatures frames incurred during welding individual pipes sections were subjected to a temperature of fourteen hundred degrees fahrenheit in a gigantic annealing for this temperature was induced not by the application of flame itself but through the circulation of super heated get shot processes were carried only as far as the production of the units action as these sections were to be joined to form a continuous penstock provision was made to actually accomplish this junction in the tunnel to guarantee a satisfactorily type field join the ends of the sections were machined on a mammoth vertical lathe operating across the thirty foot diameter of the after a final inspection of the pipe section was ready for installation a modern streamlined train passing through one of the huge tube affords an interesting gauge for the comparative size of the u album transporting the pipe section from the plant to the dam site was in itself a tremendous undertaking and to accomplish this work a special role player capable of carrying two hundred tons was designed and built caterpillar tractors furnish the motive power as the trailer itself was not equipped with a means of locomotion during handling the confirmation of the pipe section was maintained by a rigid internal brace and the movement of the heavy trucks was controlled by air brakes and power steering operator with which the trailer itself was equipped on arrival at the canyon rim directly over the dam site the unit was maneuvered into position for loading into the can to perform this task and to handle other heavy equipment a permanent two hundred ton capacity cableway had been swung over the gorge it six synchronised motors was the largest and most powerful of its kind ever built as were also the track cables themselves which spanned the canyon a distance of one hundred fifty six feet at an elevation of the one hundred feet above the river from the head tower located on the side over the track cables travelled the carried through which the hoisting and travelling cables were placed a specially designed heavy duty rig which became known to the workman as the moonbeam because of its peculiar shape and from which the pipe sections were suspended was used in lowering the huge cubes into the low levels of the canyon while cradled in a sling of heavy steel cable after all lashings were secure the pipe section was lifted from the trailer to begin its slow and carefully controlled movement over the cable way writing from the rim out into space suspended seven hundred feet above its ultimate position when the cable carried with this tremendous weight of steel had been maneuvered into location over the intended landing bar 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 while work on the apartment of features of the boulder canyon project was in progress and uninterrupted stream of concrete had been pouring into the forms of the dam from both mixing black progress was good tailed only by the limitations of sound engineering and construction practice day by day week after week the top workings of the structure of approached its full height of seven hundred and thirty feet far above the crest any other dam yet built by man june night thirty five 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 e zine or zen 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 thirty hundred foot cliff farm is a magnificent link in a transcontinental highway the reservoir filling behind the day and was named lake mead in memory of dr el would me late commissioner of reclamation whose life work culminated in the building a boat a day the largest artificial body of water in the world it expands upstream one hundred fifty miles into the lower reaches of the grand canyon with the shoreline of five hundred fifty miles opening up on vistas on glimpsed by man until invaded by the gradually rising waters of the reservoir equipped with cylindrical gates which function as giant valves the to the four steel pens stopped supplying water to the turbines and outlets that perched on shelves you into the canyon walls they tower four hundred and three feet to an elevation above the crest of the dam and the rim of the can with a 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 control once the water of the reservoir has risen to its maximum storage elevation each spillway is equipped with four one plant is built into wing one along each side of the canyon wall at the downstream toll of the day the first generator was placed in operation on september eleventh nineteen thirty six equipped with seventeen generating units with capacities range forty thousand to eighty two thousand five hundred kilo bold amperes this the world's largest power plant capable of generating one million eight hundred thirty five thousand horsepower of electrical energy when operating at its rated capacity the transmission lines carrying bolded and power radiating the network from the dam with a major line serving the los angles metropolitan area from the take off structure located on the roof of the power house our lives are taken up over the rim of the canyon into the switch yard above where the most highly specialized and modern developments in the power transmission field are to be found from the switch yard lines travel out across the desk bringing li to the homes and cities and power to the factories of south way from parker day am one hundred fifty miles to the south the colorado river aqueduct supplies the city of los angeles with the domestic and industrial water supply the imperial dam three hundred miles of the south the all american canal diverts was the colorado river into the rich agricultural district of the imperial valley and sold voted am stands today a modern limits of its last problems here