Photo #162 of 365 - Hoover Dam Diversion Tunnel
Before construction could begin, the river was diverted around the dam site through four 50-foot-diameter tunnels, two drilled through the canyon walls on each side of the river. The tunnels, with a total combined length of 15,946 feet, or about three miles, were excavated to 56 feet and lined with three feet (300,000 cubic yards) of concrete. They could carry over 200,000 cubic feet - more than 1.5 million gallons - of water per second. The river was first diverted through the two Arizona tunnels on November 14, 1932.
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