David Moore, P.E.
Copyright (c) 1999 David Moore
Note: This article first appeared in the November/December 1999 issue of People, Land & Water, a news magazine of the US Department of the Interior, Washington DC, 202-208-7291.
Hoover Dam, America's first high dam, straddles the Colorado River-and the 20th Century-like a colossus, a national asset that has provided the West, particularly Southern California, security, power, and water for more than 60 years.
The hordes of farmers who settled the basins of Southern California
in the 19th Century-such as the Imperial and Coachella Valleys-relied on
the river to supply irrigation water to their fruit and vegetables farms.
But the Colorado could ravage as well as reward those who relied on it.
From the high reaches of the Rocky Mountains, the river travels 1,300 miles
to the Gulf of Mexico, draining one-twelfth of the nation.
Herbert Hoover, who headed the commission charged with resolving this dilemma, proposal in 1922 to give equal water shares to the upper and lower basins, allowing each area to work out a specific allocation formula for its states. His proposal was accepted and the Congress approved the dam project in 1923, stipulating a repayment period of 50 years but exempting flood control costs. To honor him for this statesmanship, the fair-minded President Truman and the 80th Congress named the structure Hoover Dam in 1947.
Classified as a gravity-arch dam, Hoover acts like a ring segment wedged between the high canyon walls. Bureau engineers incorporated the complex theory of elastic deflection into their design of the unusual dam, an effort that required long involved calculations with slide rules and log tables. The success of the massive structure in harnessing the Colorado attests to the greatness of yesterday's engineers and their careful work.
The other part of the Hoover Darn team was the contractor. The Big Six (construction companies) signed a contract to build the dam for $48,890,995.50. Work began in 1931. The cost of building Hoover Dam is about equal to that of a U.S. Army helicopter today. Construction required more than five thousand workers, 30-foot diameter penstock pipes, and five million barrels of cement, to name but a few of the major items. The dam was built in separate large columns of concrete, keyed together and grouted to make a solid mass. Intensive work went on 24 hours a day with concrete being lowered into the canyon by an overhead cable system. Frank Crow directed the Big Six construction effort, while technical direction was under Walt Young, chief engineer for the Bureau of Reclamation.
The contractor finished the dam in 1936, two years ahead of schedule, and received a bonus of $369,000. By the end of 1939, half of the generating units were on line, and four were added during World War II. War industries in the Southwest and on the West Coast received half of the power they required from Boulder Darn. The West Coast produced 46 percent of the military aircraft built during the war and 52 percent of the tonnage needed by the Navy. North American Aviation, which was on the Los Angeles power grid connected to Hoover Dam, built 40,000 of these war planes. The Calship yards, the largest in the country, also used electricity from Hoover.
These aircraft also needed magnesium to strengthen their aluminum airfrarnes, so the government built a huge magnesium plant at Las Vegas to process nearby ores using Hoover's power. The plant supplied a quarter of this essential metal in the war.
By 1961 all 17 generators at Hoover were operating, making two million kilowatts of energy. Sales of this power had recovered the cost of building the dam by 1985. Hoover continues to produce about 3.5 million kilowatt-hours (KWH) a year. Using the California household rate of 10 cents per KWH, Hoover's production generates $350 million annually for government coffers. Not a bad investment for a $50 million dam. The Davis and Parker damns, below Hoover, have added a million and a half KWH yearly to the nations power production. Clearly, cheap power was the key to opening the West to industry.
But power sales are just part of the story. Along with the dam, Congress authorized the 232-foot wide All-American Canal that winds 80 miles from the Colorado to irrigate about 518,200 acres in California's rich Imperial and Coachella Valleys. The dam enabled these farmers to produce $8 billion worth of crops in the years 1943-85. All told, three quarters of a million acres have been served in some measure by water from the dam. The Davis Dam was built to store water for our Mexican treaty obligations while the Parker serves the Metro Water District that diverts water into a 300-mile pipeline that provides southern California's people and industry with water. One-third of Hoover's power is used to pump this water over the mountains.
And all of this is due to the those old-timers-bureau engineers, Big Six managers, and Depression-era construction workers-who challenged the odds and conquered the Colorado, creating an engineering marvel for the bureau's legacy.
Copyright © 1999 David Moore, PE