Building Diversion Tunnels
Video duration: 2:47
The most dangerous phase of Hoover Dam's construction was building the diversion tunnels, two on each side of the Colorado River. Blasting holes 56 feet in diameter, three-quarters of a mile through the canyon rock, the workers faced a huge engineering challenge along with strict time constraints. Chief Engineer Frank Crowe solved the problem by building a contraption called a drilling jumbo.