As the Great Depression unfolded, hopeful laborers descended on Las Vegas and set up camp in the surrounding desert for the chance to work on the project. Those who were hired eventually moved to Boulder City, a community specifically built six miles from the work site to house its employees. Meanwhile, the U. The first difficult step of construction involved blasting the canyon walls to create four diversion tunnels for the water.
Facing strict time deadlines, workers toiled in degree tunnels choked with carbon monoxide and dust, conditions that prompted a six-day strike in August The second step of involved the clearing of the walls that would contain the dam.
Suspended from heights of up to feet above the canyon floor, high scalers wielded pound jackhammers and metal poles to knock loose material, a treacherous task that resulted in casualties from falling workers, equipment and rocks. Meanwhile, the dried riverbed allowed for construction to begin on the powerplant, four intake towers and the dam itself.
Cement was mixed onsite and hoisted across the canyon on one of five ton cableways, a fresh bucket capable of reaching the crews below every 78 seconds. Offsetting the heat generated by cooling concrete, nearly miles of pipe loops were embedded to circulate water through the poured blocks, with workers continually spraying the concrete to keep it moist.
As the dam rose, block by block, from the canyon floor, the visual renderings of architect Gordon Kaufmann took form. Electing to emphasize the imposing mass of the structure, Kaufmann kept the smooth, curved face free of adornment. The powerplant was given a futuristic touch with horizontal aluminum fins for windows, while its interior was designed to pay homage to Native American cultures.
With the body of water that would become Lake Mead already beginning to swell behind the dam, the final block of concrete was poured and topped off at feet above the canyon floor in They heard how in the early spring in the meadow by the mill-dam Tim and I had stopped our ploughs to draw lots and he had lost.
For that matter, he said, he didn't care a tinker's dam if we were; he had grub and bedding and we were welcome to both.
On the opposite side of the stream, set back about thirty paces from the brink, stood a granite boulder.
The great Dam at Assouan was just completed and we traversed its entire length on a trolley propelled by natives.
In fact, some early warnings came before the legal framework that divided the Colorado among the seven states and Mexico. Under the Colorado River Compact and subsequent agreements, the river has long been severely overallocated. Only a smattering of natural wetlands remain.
Its electricity helped produce the ships and planes that won the Second World War, and its water helped grow the food. They found that in , U.
Negotiating the post rules will be challenging for everyone involved, Kuhn and Fleck wrote, and some of the fundamental issues facing negotiators now are similar to those a century ago, including questions of how much water the river will provide in the years ahead, and how the system should be governed amid uncertainty. Innovation, cooperation, and an expanded reliance on science are now the foundation for basin-wide solutions.
One effort to restore some of the wetlands and ecosystems in Mexico began this month, as water began flowing into the delta under an agreement between the U. The water releases in the delta, which will total 35, acre-feet between May and October, are intended to nourish vegetation and wildlife at habitat restoration sites where conservation groups have planted cottonwoods and willows.
The influx of water is supposed to mimic a small portion of the floods that once swept across the delta toward the Sea of Cortez. The releases in the delta this year, using water previously stored in Lake Mead, amount to just 5 inches of water in the reservoir.
Much more of the water that passes through Hoover Dam is pumped to Phoenix, Tucson and Los Angeles, and flows through canals to irrigate farmlands along the river from Parker to Yuma, and across the Coachella, Imperial and Mexicali valleys. As we continue through the innards of Hoover Dam, the polished terrazzo floors and hallways give way to a dim tunnel, which cuts into the canyon wall.
Its ceiling and sides are rough-hewn jagged rock resembling a mineshaft. We never call it a leak because it's not a leak. The water seeps from the lake through cracks in the rock and is routed to drains and a sump, then pumped to the river below the dam. When the reservoir is higher, Bernardo says, the amount of water seeping through increases because the lake exerts more pressure.
At the end of the passage, we step into a room with windows that look out over the diversion tunnel and the penstock, a steel pipe 30 feet in diameter. Referring to a diagram on the wall, Bernardo explains how water enters the dam, spins the turbines and discharges into the river.
If the water were to decline about feet from where it stands, below the elevation of feet, he says, Hoover Dam would lose the ability to generate power. If Mead continues to fall further, the dam could still release water down to a level of feet.
So you would essentially have to pump it out of Lake Mead. If the lake declines that much, only the Southern Nevada Water Authority, which supplies Las Vegas, has an intake deep enough to continue pumping water. Before the building of Hoover Dam, the Colorado River was dangerous and unreliable.
Melting snow in the mountains caused damaging floods during the late spring and early summer. Unpredictable flash floods could occur in any season. In , the Colorado River flooded rich, irrigated farmland in the Imperial Valley in southern California. It caused enormous damage and permanently flooded thousands of acres. Reclamation engineers began to study the Colorado River soon after passage of the Reclamation Act in They were looking for places to build dams to store the water from the annual spring runoff, releasing it gradually during the summer for irrigation.
By the early s, most people thought that building a big dam on the lower Colorado was the best way to store water to irrigate the low-lying valleys of Arizona and southern California and to protect them from floods. By this time, too, developers in Los Angeles and other rapidly growing cities in Southern California had added their powerful support for the project. They saw the dam as a potential source of water and hydroelectric power for homes, businesses, and factories.
In , the seven states of the Colorado River Basin met to decide how to divide the waters of the river. Herbert Hoover, at that time the secretary of commerce for Republican President Calvin Coolidge, led the discussions.
Most of the states were afraid California was going to get more than its fair share of the water. Ultimately, they managed to agree on a document, called the Colorado River Compact. The compact also committed the U. Some states were not happy about the compact; Arizona did not ratify it until It did permit planning for the dam to proceed, however. Also in , congressional representatives from California introduced a bill to authorize Reclamation to build the big dam on the lower Colorado.
By this time, they were among the most knowledgeable and experienced dam builders in the world, but even they had never done anything this big.
Hoover Dam would be the highest dam in the world, far taller than anything they had built so far. The lake it created would be the largest in the world. The proposed dam would be so tall and the pressure of the water it held back so great that many people were worried. Others wondered whether the expected benefits would be enough to justify the enormous cost.
Despite these questions, planning and design went forward. Six Companies was a group of some of the largest construction companies in the country. They joined specifically for this project. The contract divided the work between Six Companies and Reclamation. Reclamation engineers designed the dam and created the hundreds of detailed plans and specifications that the contractors would follow.
If the work was consistent with the plans, they approved it for payment. They hired and housed the workers. They transported supplies to the dam site. They were responsible for keeping the project on schedule and within budget. The plan was for construction to start in the fall of , in the depths of the Great Depression, which had begun with the stock market crash of Herbert Hoover, now president, wanted to start work on the dam earlier, probably as a way to ease high unemployment.
Work actually began during the summer and continued around the clock until the dam was completed in , two years ahead of schedule. By this time, Franklin D. Roosevelt, a Democrat, had been elected president.
The huge dam on the Colorado captured the imagination of journalists, authors, and filmmakers. The New Deal was famous for using public works projects to put Americans back to work. In the early 21st century, almost a million visitors a year still come to see the great dam on the Colorado River. Hoover Dam is 1, feet long at the top. It is feet high from the lowest point of the foundation to the crest. The dam is feet thick at the base and tapers to 45 feet thick at the top. Its reservoir was the largest artificial lake in the world for decades and is still the largest in the United States.
Questions for Reading 1 1. Why did many people think something needed to be done to control the Colorado River? What sort of problems did the river create? What benefits would controlling it provide and to whom? Why were congressional representatives from the state of California the leading supporters of a big dam on the Colorado?
Why do you think President Coolidge's secretary of commerce led the discussions leading up to the Colorado River Compact?
What role might the federal government be able to play in making decisions like this? An acre-foot is the volume of water that would cover one acre one foot deep. Why do you think they used a measure like that, rather than something like gallons?
How many gallons of water are in an acre-foot? How much would that weigh? What were some of the concerns people had about its construction? How did Reclamation and Six Companies divide the work on the dam? Department of the Interior, ; and Donald C. The guide included the instructions excerpted below: 15 Minute Course in Engineering Full? In fact there are still quite a few nice canyons along the Colorado River. You can take one of them—no one will miss it—maybe.
And you will need to build some roads and erect a power line. At Boulder Dam they had to get the electricity from Los Angeles to build the dam which now sends electricity back to Los Angeles. Sand and gravel—get quite a bit of this to mix with the cement; enough to make 4,, cubic yards of concrete. Pipe for ice water— miles of it will do. Plate steel for making pipes—88 million pounds—when you get into pipe 30 feet in diameter, you have to make your own.
Structural steel, nuts, bolts—and other stuff like that—18 million pounds. Assorted steam shovels, etc. Make them each 56 feet in diameter, then line them with three feet of concrete. When you finish you will have 3 miles of tunnel 50 feet in diameter. At the other end of the tunnels build another cofferdam to keep the water from backing up, pump the puddles out from between, and there you have it—a dry spot in the river, with the stream running right around it, through the tunnels.
Lower several hundred men from the top on ropes and let them drill the cliffs full of holes. Stuff the holes with dynamite, and blast it away. Repeat as necessary. Better do that right now. Build a platform so spectators can watch, and dig down about feet from the river bed to bed rock, removing all loose material as you go. You are now ready to install the main portion of the dam.
Concrete has a nasty habit of cracking. The lime in cement causes it to get hot when it is mixed with water. Obviously you must not allow this to happen when you are building a dam. If cracks were to appear in your dam it might cause severe criticism from people living below the dam—or from their heirs. It would take years for all that concrete in the dam to cool under normal conditions.
To hurry it up, string two or three miles of water pipe around through each five-foot layer of concrete as you pour it. From your ice plant, run ice cold brine through the pipes.
This will cause the mass to cool and shrink quickly. Your dam will be sealed tighter than a drum—and wedged between the canyon walls. Drill holes connecting them with two of the tunnels constructed in Lesson 4. Plug the upper end of the tunnels to cut off water from the lake. At flood time, if the lake rises high enough to reach the spillways, it can be turned out through these original tunnels.
Erect a power house below the dam. Now drill holes through the cliffs from towers to power plant. Connect them with pipes. As you make each section of pipe, X-ray it for defects. This completes our engineering course. Questions for Reading 2 1. This guide contains many large numbers. Can you think of ways to translate those numbers into comparisons with more familiar things, so that it would be easier to get a sense of how big the project was?
The diversion tunnels were among the longest in the world when they were built. Six Companies thought that building them was the most critical part of the project. Why do you think both Reclamation and Six Companies thought the diversion tunnels were so important?
Do you agree? Explain your answer. Why was it important to speed up the cooling process? How long would it take for the concrete in the dam to cool by itself? The pipes are still there, buried in the concrete. The spillways at Hoover Dam are only used when the water in the reservoir is so high that it would otherwise overflow the top of the dam.
Why do you think the engineers thought they had to keep this from happening? In Lesson 1, the guide suggests, possibly not quite seriously, that you could take any canyon on the Colorado you wanted—"no one will miss it, maybe. What might people "miss" about these canyons if they were filled with water?
Do you think anybody today would suggest that no one might notice if you flooded one of them? Why or why not?
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