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BY HENRY PETROSKI

Recalling a Great Achievement

Ambitious engineering projects are possible even in tough economic times.


Photo: HENRY PETROSKI This month marks the seventy-fifth anniversary of the dedication of Hoover Dam, a great engineering project carried out during a period of financial turmoil. Such an achievement might serve as a model for what could be dreamed of today.

Like many an ambitious project, the idea for a dam across the Colorado River began in the minds of visionaries who perceived not only problems but also solutions. Among these people were politicians, scientists, and, of course, engineers.

The Colorado was both blessing and curse to the states through which it ran. It could bring much-needed water for irrigation, but it could also bring floods, carrying silt that wreaked havoc on vital irrigation canals and the course of the river itself.

In 1917, Phil Swing, a freshman congressman from southern California, introduced legislation to construct a canal to serve the Colorado River basin. The engineer Arthur Powell Davis argued for a more comprehensive plan that would benefit not only California but also the six other states laying claim to the river's water.

A comprehensive hydrological and geological study of the river and its canyons led to the recommendation that a large flood control and hydroelectric dam be constructed in the vicinity of Boulder Canyon, with the revenue from selling the generated electricity eventually repaying the cost of the project.

Before plans could go forward, however, the seven states claiming water rights had to come to an agreement about how it would be apportioned. Herbert Hoover, whose distinguished career as a mining engineer and leadership in World War I humanitarian relief efforts had led to his appointment as U.S. secretary of Commerce, played a central role in the negotiations. It was his engineering sense and political savvy that led to the 1922 Colorado River Compact, which paved the way for the 1928 enabling legislation.

Where exactly to locate the dam was influenced not only by the nature of the rock in the canyon walls and floor but also by proximity to supplies of sand and gravel for making concrete and by accessibility to the construction site. About 30 different design geometries were considered for the dam proper, and the one chosen rose 725 feet above bedrock and was 660 feet thick at the base and 45 feet wide at the crest.

The detailed design was completed by the end of 1930, and the dam's construction was seen as a means of providing employment and promoting business recovery in economically difficult times. The successful $49 million construction bid came from a consortium that called itself Six Companies, and it resulted in a federal government contract unsurpassed in value until World War II. The mastermind behind the successful bid and general superintendent of construction was Frank T. Crowe, known as America's foremost dam builder.

With the Colorado River diverted through tunnels in the canyon walls, concrete began to be poured in mid-1933 and proceeded continuously for two years. The dam was finished in early 1936, a couple of years ahead of schedule, and soon became a tourist attraction.

Unfortunately, the two-lane road across the crest of the dam produced a bottleneck in the highway between Arizona and Nevada. But relief is in sight, for a bypass road and concrete-arch bridge, under construction since 2005, are scheduled to be completed this fall.

The stories of great engineering achievements like Hoover Dam remind us of what can be accomplished, even in the toughest of economic times. Let us hope that such current proposals as high-speed rail systems and smart electric grids will be the subject of future anniversaries.

Henry Petroski is the Aleksandar S. Vesic Professor of Civil Engineering and a professor of history at Duke University. His latest book is The Essential Engineer: Why Science Alone Will Not Solve Our Global Problems.

 

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