BUILDING BIG: Databank: Hoover Dam

In 1931, during the height of the Depression, thousands of American workers came to the Black Canyon on the Arizona-Nevada border to tame the Colorado River. They began construction on what would be the largest dam of its time -- the Hoover Dam.

But before the dam could be built, workers had to divert the wild Colorado River away from the construction site. How did they do this? They blasted tunnels -- as big as four-lane highways -- right through the canyon walls. For the next five years, the Colorado River gushed through these diversion tunnels while 8,000 workers toiled in the harsh, dry canyon bottom. Amazingly, they completed the dam in less than five years -- ahead of schedule and under budget.

The Hoover Dam is a curved gravity dam. Lake Mead pushes against the dam, creating compressive forces that travel along the great curved wall. The canyon walls push back, counteracting these forces. This action squeezes the concrete in the arch together, making the dam very rigid. This way, Lake Mead can't push it over.

Today, the Hoover Dam is the second highest dam in the country and the 18th highest in the world. It generates more than four billion kilowatt-hours a year -- that's enough to serve 1.3 million people!

Fast Facts:

At its base, Hoover Dam is as thick (660 feet) as two footballs fields measured end to end.
Hoover Dam is 726 feet tall. That's almost 200 feet taller than the Washington Monument in Washington, D.C.
During peak periods of electrical demands, enough water runs through the generators to fill 15 average-size swimming pools (20,000 gallons each) in one second.
There is enough concrete in Hoover Dam (4.5 million cubic yards) to build a two-lane road from Seattle, Washington, to Miami, Florida, or a four-foot-wide sidewalk around the Earth at the Equator.
The Hoover Dam is so thick and heavy, it doesn't even need to be curved! It's heavy enough to resist the weight and thrust of the water pushing behind it, but designers thought people would feel safer with a curved design.