Many people know the Hoover Dam is an iconic piece of history, but some do not know there is an operating hydroelectric plant that supplies power to Arizona, California and Nevada.
More than 500 feet below the dam is a 2,080-MW power plant operated by the Bureau of Reclamation that uses 17 main Francis turbines or waterwheel located under the generators. Eight of the turbines are on the Nevada side of the plant and nine are on the Arizona side. The last unit was installed in 1961, and an uprate project was completed in 1993. The water reaches the turbines through four penstocks.
The tour starts in one of the four original inner-divergent tunnels. Two man-made dams were built to push the water through and begin to fill Lake Mead. The Lower Coffer Dam helped the water to not back up back into the Colorado River. It was blasted after the lake was formed and the water was allowed to cover the upper coffer dam, which is still located under the water to date.
The power plant also has two station-service Pelton water wheel units rated at 2.4 MW each that provide power for the visitor’s center and plant operations, such as the cranes, lights, pumps and motors. The plant also features two bridge cranes from the 1930s used for maintenance projects on the generators. Each crane can lift 300 tons, according to Rebecca Weir, tour guide.
The dam is designed to move during an earthquake, estimated to withstand a magnitude of 8.5. Lake levels depend on melting snow packs from the mountains. There has, unfortunately, not been much snowfall in the past few years, so lake levels are down.