One of the most ambitious projects realised in the United States is the Hoover Dam. This piece of public infrastructure is located in the Black Canyon of the Colorado River on the border between Arizona and Nevada. Although it was originally known as Boulder Dam, the United State Congress officially renamed it Hoover Dam in 1947.
Location of the Hoover Dam:
The need for such a concrete, arch-gravity dam was identified from about 1900 onwards and deemed crucial to further develop the Southwest of the United States by controlling floods, providing irrigation water and producing hydroelectric power. Today these resources are still indispensable for large and well-known regions of California, Nevada and Arizona like Los Angeles and Las Vegas. Some of the water is even provided to Mexico.
Despite the great depression the dam was still finished after 5 years of construction in 1936: 2 years ahead of time. The volume of water held back by the dam could cover the state of Connecticut with 3 m (10 ft) of water. All of the 3.330.000 m3 concrete used during construction is sufficient to pave a two-lane highway from San Francisco to New York. A single continuous pour of concrete would therefore have taken 125 years to cool, resulting in cracking and crumbling of the dam. Hence, the engineers of the Bureau of Reclamation divided the dam in lego-like blocks which were actively cooled.
1941 Photograph by Ansel Adams:
Construction of this 221.4 m (726.4 ft) high and 379 m (1.244 ft) long colossus set the United States Government back $639 million in 2016 dollars. Due to the immense size of this undertaking 6 companies combined forces in a consortium aptly called Six Companies, Inc. The ingenuity and scale of this project is evident from the following archive footage:
The official death toll associated with construction is 112. J.G. Tierney, a surveyor, was the first and drowned on December 20th 1922. Exactly 13 years later his son, P. Tierney, was the last to die due to a fall from an intake tower. This number does however not include fatalities due to ‘pneumonia’. Since records do not show any deaths of non-workers due to pneumonia in nearby Boulder City, the workers most likely were correct in assuming that this was a cover for carbon monoxide poisoning. The Six Companies thereby avoided paying compensation to the families.
The number of casualties would have been higher if the workers would not have been encouraged to wear provided hard boiled hats. This practice was adopted after it was noted that the injuries from falling objects were lessened when workers wore cloth hats they had dipped in tar to protect themselves.
The only grave at the dam is reserved for its mascot ‘Nig’. This dog was born in 1932 under dormitory No. 4 and grew to be beloved by everyone. He not only raised spirits but also demonstrated the potential for all workers to unite for a common cause. After becoming sick due to overfeeding, the workers took out an add in the local newspaper urging people to stop feeding him and arranged for the commissary to provide his food. The Hoover Dam mascot unfortunately met an untimely end on February 21st 1941 due to a car accident. It should lastly be noted that his name has sparked some controversy in recent years.
The power plants located inside the Hoover Dam do not only finance the substantial yearly maintenance budget of the dam, but easily repaid the 50-year construction loan as well. This income is further supplemented by nearly one million tourists which visit each year. They not only marvel at the magnitude of this structure, its architecture including designs of Allen Tupper True and Oskar J.W. Hansen, the surrounding nature and wildlife but also interesting physical phenomena. Heating of the concrete wall by the sun creates a warm updraft of air thereby blowing water which is poured over the edge upwards:
Lastly, it should be noted that Arizona and Nevada are located in different time zones. The shifts at the power plants at either side of the dam therefore end at the same local time but different moments of the day on either side. Since Nevada does not respect daylight saving time, this only holds for approximately each other half of the year.
In the 1980s the remarkable and impressive nature of the Hoover Dam was recognised since it was listed on the National Register of Historic Places, labelled a National Historic Landmark, and acknowledged as a National Civil Engineering Landmark. An overview of the Hoover Dam and its construction is given by the podcast Unprofessional Engineering:
Although this blog post covered some interesting aspects of the Hoover dam, a lot more are discussed in literature and media. A preview of topics like the environmental impact and the fierce political battles in Washington is given in the interview by NPR books with M. Hiltzik, author of ‘Colossus: Hoover Dam and the Making of the American Century‘.
For more visually inclined readers one hour specials of National Geographic or the Science Channel can provide more information:
sources and starting point for more research:
Hoover Dam on Wikipedia
Hoover Dam on Bureau of Reclamation website
Arch-gravity dam on Wikipedia
Hoover Dam mascot on Bureau of Reclamation website