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 ...

High Scalers drill into the canyon wall 500 feet above the Colorado River in Black Canyon at the Hoover Dam site ... reassigned a number of diversion tunnel workers to lower paying jobs.

“Our guided tours offer an educational, informative and entertaining experience into the Hoover Dam, power plant and penstock tunnels. Please keep in mind that Hoover Dam is a secure federal ...