Transcript for The Story of Hoover Dam, segment 04 of 12

Reclamation engineers rushed to completion specifications and design drawings. Crews at the dam site completed their surveys and investigations.

The thunder of man's determination to conquer the Colorado reverberated between the sheer cliffs of Black Canyon as construction got underway. The first major task was to divert the river around the dam site. To do this, four tunnels, two on each side, were drilled through the canyon walls. Each fifty-six feet in diameter, they averaged four thousand feet in length. Drill holes were packed with dynamite and blasted. After each explosion shovels and trucks entered the tunnels, mucked out the shattered rock, and dumped it in nearby gulches.

Workmen excavated over one and a half million cubic yards of blasted rock material in the four tunnels in thirteen months. The tunnels then were lined with concrete three feet thick.

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Explosions rocked the canyon almost daily for two years before actual placing of concrete in the dam began.

Acrobatic workmen called high scalers prepared the canyon walls for each blast. Suspended on ropes, they drilled holes in the rock and loaded them with dynamite.

After each explosion these daredevils swarmed over the cliffs, prying loose rock and clearing the walls of debris.


In November, nineteen thirty-two, the Colorado River was diverted. Under control for the first time in its history, the river flowed around and past the site. Men and trucks dumped an earth and rock embankment across the canyon below the tunnel openings, forcing the river from its age-old bed through the huge diversion tubes.

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