Today we explored Hoover Dam. We were here 15 years ago and walked across the dam, a quick stop en route to our next destination. Those were the days when we hurried through many places of interest because of time constraints. I call them the "drive-by" touring days.
This time we spent several hours here, went to the visitor center, watched the film about the dam's history, and also took the tour of the plant with its massive turbine generators.
It turned out that the dam is a mere 3 miles away from the RV Park where we stayed. We could have walked the trail to the dam, and since we want to return to stay longer and explore more of the Lake Mead Recreation Area, we will definitely do that Hoover Dam Trail hike through the 5 tunnels to the dam in the future.
More than 80 years since it was built, Hoover Dam continues to be a marvel and attracts tourists from all over the world.
The dam project was planned to provide and assure a stable year-round water supply. In the 1800's and early 1900's, the Colorado River often flooded low-lying farmlands and communities in the spring and early summer. In the late fall and winter the river often dried to a trickle. Herbert Hoover was in Congress at the time and became instrumental in proposing a bill whereby the waters would be equitably divided among the seven states that relied on the Colorado's waters. Signed in 1922, the agreement divided the Colorado Basin into an upper and lower half and gave half the river's annual estimated flow to each basin. Division of each basin's apportioned allotment was left to the states in that basin. Mexico only received its guaranteed apportionment after the signing of the Mexican Water Treaty in 1944.In 1928 after the construction of several storage dams and delivery facilities on the Colorado River, Congress passed the Boulder Canyon Project Act authorizing the construction of Hoover Dam (which until 1947 was called the Boulder Dam).
Hoover Dam is named for 31st President Herbert Hoover.
Construction began in 1931 and ended in 1935, two years ahead of schedule and well under budget. The original $165 million cost has been repaid, with interest, to the Federal Treasury through the sale of Hoover Dam power.
More than 5,000 workers labored day and night, in extreme heat and constant danger to raise this concrete marvel. The project required housing for the workers and their families, and in one year the barren desert was transformed into a company town, Boulder City, with schools, churches, and recreational facilities.
Ninety six workers lost their lives in accident-related deaths and contrary to popular belief, none are buried in the concrete.
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| scale model in visitor center of construction |
Technical innovations developed during the dam's construction transformed several traditional engineering methods, setting a precedent for future large construction projects. Of noteworthy mention are the following: a three-story jumbo drill allowing 30 miners to drill simultaneously was invented and built; the dam was poured in individual, interlocking blocks rather than as a solid mass; cold water carried in pipes was used to cool the curing concrete; the aerial cableway system was the largest, most complete ever built; hardhats were provided to workers; and the dam's concrete plants were the world's most sophisticated.
Building this dam required more concrete than was used in all the dams built by the Bureau of Reclamation prior to 1931. To assure that the concrete would harden properly, the dam was built in a series of blocks. Each concrete block added 5 feet to the wall, and no more than 7 blocks (35 feet of height) were added in a 30-day period to assure the integrity of the drying concrete.As concrete hardens (cures) it gives off heat. Cold water from the Colorado River and a refrigeration plant was used to cool the concrete, allowing it to cure quickly and evenly. The information board explained that had the concrete been poured as a single mass, it would have taken 125 years to cure.
The arch gravity dam stands 726 feet tall (221.3 m); is 1,244 feet long (379.2m); 45 feet (13.7m) thick at the top and 660 feet (201.2m) at the base; weighs 6.6 million tons, and used 3.25 million cubic yards (2.6 million cubic m) of concrete.
It certainly is an impressive wall of concrete!
President Franklin D. Roosevelt dedicated the dam in 1935. The powerplant wings were completed in 1936 and the first generator began operation in October that same year. The 17th and final generator went into operation in 1961.
Lake Mead, Hoover Dam's reservoir, with its 9.2 trillion gallon-capacity (nearly two years of the river's average annual flow) is the largest man-made reservoir in the US.
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| intake towers control the flow of water into the penstocks |
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| going underground to take the tour of the powerplant |
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| the massive penstocks that carry water to the turbines |
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| Turbine generators in the powerplant wing on the Nevada side that produce electricity |
On our way back home, we stopped and walked across the O'Callaghan-Tillman Memorial Bridge, completed in 2010. The bridge spans the Colorado River between Arizona and Nevada. From the bridge we could look directly across at the entire expanse of Hoover Dam.
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| O'Callaghan-Tillman Memorial Bridge |
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| 900 feet above the Colorado River overlooking the historic Hoover Dam |