WSP10089

• File Number: 8220.200.05.A
• Description: Hoover Dam/Lake Mead/Boulder Canyon Project
• Basin: Colorado Mainstem
• Date: 1/1/1950
• Title: The Story of Hoover Dam: Conservation Bulletin No. 9
• Water Supply Pro - Doc Type: Publication

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Boulder Canyon. Eight cubic. yard capacity bucket discharging load
into dam forms at upstream lace of dam.

two 60.horsepower caterpillar tractors, transported the heavier pipe sections
from the plant to the canyon rim. From the rim of the canyon the pipe was
transferred to the lS0*ton cableway and lowered to the portal of one of the
construction adits. Here, a specially constructed car received the pipe and
conveyed each section through the adit to the penstock header tunnel. Finally,
each section was pulled into position by winches and hoists.
All pipe sections were joined with steel pins, the largest of which were 3
inches in diameter, except the 8Vz-foot outlet conduits, which were hot.
riveted, and a few miscellaneous sections that were welded. In welding,
the weld and pipe near it were stress-relieved by heating with gas rings.
Meanwhile, while the engineers were surmounting the difficulty of making
and installing the great penstock pipes, the main job of concrete placement
for the huge structure of the dam was being carried out swiftly. On June 6,
1933, the first bucket of concrete was placed. Six months later a million
yards were in place. Another million was poured in the following half year,
and the third million by December 6, 1934, only 18 months after starting
placement.
As soon as construction of the dam, intake towers, and outlet works was
sufficiently advanced, and the upstream portions of the two inner diversion
tunnels plugged with concrete, a steel bulkhead gate was lowered at the inlet
of the outer diversion tunnel on the Arizona side of the river.

22

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Th~ ni('~r lIarnl?fUH!d at '~aHt

This was February 1, 1935. Back of the unfinished dam, water started
to rise. By midsummer the new reservoir held more than 3,000;000 acre-feet
of water with a maximum depth of 271 feet. And the formerly muddy
Colorado dropped its silt in the reservoir, resulting in a lake of clear blue
water sparkling in the brilliant 5un.
When the waters of Lake Mead had risen to the base of the intake towers,
260 feet above the river bed, the one remaining opening-the gates in the
outer diversion tunnel on the Nevada side-was closed. From that time, the
Colorado had to respond to rein. For the first time in history the river had
been harnessed.
Concrete pouring continued and the crest height of the dam \vas reached
March 23. 1935. By the following summer all the concrete-3,2.50,335 cubic
yards, 6,900,000 tons of it-was in place.
In 21 months 5,000 men with modern equipment had built a struCture
whose volume was greater than the largest pyramid in Egypt, which, according
to Herodotus, required 100,000 men working 20 year.5' to build.

Arizona side of downstream face of the dam. View shows power plant
footings and foundation.