Transcript for Hoover Dam Construction, segment 11 of 17
It was on June sixth, nineteen thirty-three, that the first bucket of concrete was placed in the very lowest of the dam forms, one hundred and thirty-five 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 impregnable rock of its 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 six hundred and sixty 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.
The transit mixers were transported on trucks from the bed of which they could be removed and handled on the overhead cableways. These were used in the placement of concrete in the confined forms along the abutments, where the eight cubic yard buckets could not be handled. Selecting at random one bucket from among the hundreds of thousands that traveled from the canyon rim over the cableways 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, its tremendous weight of twenty-two 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 bulk and tonnage. 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 dam's bulk. Concrete was compacted into the forms by mechanical vibration, the application of which insured dense compression against adjacent surfaces.
Workmen were carried from the canyon rim to the dam forms by way of the inclined skidway, or 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 four days, two million of the three and one quarter million cubic yards of the dam's 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.