Transcript for The Story of Hoover Dam, segment 06 of 12
As the first bucket of concrete settled into its foundation on June sixth, nineteen thirty-three, Hoover Dam began its rise from the depths of Black Canyon. As cableways dumped load after load of concrete into the forms, the dam soon reached its full six hundred sixty foot thickness at its base. Poured in five foot layers of concrete, the structure's keyed or interlocking columns climbed skyward as crews set new records daily. Bucketful after bucketful ran the continuous cycle, mixing plant to canyon rim, out into midair over the gorge, and down into the forms, dumping its load of sixteen tons.
Crews vibrated and compacted the fresh pours while buckets returned again and again to the mixing plants to be filled with more concrete for other waiting pours. Crews worked under all conditions, all seasons of the year without cessation, rain or shine, day and night. By June, nineteen thirty-four, one year after the first pour, two thirds of the dam's concrete had been placed in the forms. Hoover Dam had risen to an impressive height, already taking its place as one of the world's wonders.
As Hoover Dam climbed between its abutments, related structures also took form. At the toe of the dam, the U-shaped power plant to house generating equipment, control and maintenance facilities was built in twin wings, one along each side of the canyon walls. Intake towers, two on each side, for the power plant's penstock system climbed as a maze of reinforcing steel and concrete. Perched on shelves hewn in the canyon walls, these graceful columns rose four hundred and three feet, well above the dam's crest and the canyon rims. Two giant spillways were set against the canyon walls on each side of the reservoir just above the dam. These high level controls, each capable of bypassing two hundred thousand cubic feet of water per second, assure that no water will ever overtop the dam. Water flowing into the basins plunges downward through the spillway tunnels to enter the river below the dam. One hundred foot long drum gates on the spillway's crests rise during flood stage to give the reservoir an additional sixteen feet of storage.