Hoover Dam

8. Power House

The powerhouse was one of the projects uncompleted at the time of the formal dedication on September 30, 1935 - a crew of 500 men remained after the dedication to finish it and other structures. To make the roof of the powerhouse proof against bombs, it was constructed of layers of concrete, rock, and steel with a total thickness of about 3.5 feet (1.1 m), topped with layers of sand and tar.