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Transcript for Hoover Dam Construction, segment 06 of 17
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.
To reach 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 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 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 scalers, 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 bosun's chairs from the canyon's rim, these daredevils were protected in their hazardous work by hard helmets, safety ropes, and other safety appliances.