The Hoover Dam in the United States is a man-made miracle of Arizona. Hoover Arch Gravity Dam on the Colorado River in the United States Impact on nature

January 5th, 2015 10:58 am

I'm starting to write a report about the trip to Supai. The report itself will begin in the next post, and now I will talk about the Hoover Dam.

The Hoover Dam is one of the most famous and one of the largest dams in the United States. It is located on the Colorado River on the border of the states of Nevada and Arizona.

The Colorado River has always had a turbulent character. As a result of floods, people died and great economic damage was caused. Often the river changed its course. At the beginning of the 20th century, the idea arose to build waterworks on the Colorado River to reduce the risk of flooding and use the river's waters for agriculture. With the development of the electric power industry, the idea of ​​building a hydroelectric power station also arose. Surveys have shown that the most suitable place for the construction of the dam is the Black Canyon.

However, the construction required the consent of the seven states through which the Colorado River and its tributaries flow. Some states feared that the redistribution of water resources would not be in their favor. In 1922, a commission was created, which included representatives from seven states. Herbert Hoover, then Secretary of Commerce, took part in the work of the commission. As a result of the work of the commission, an agreement was adopted on the use of the water resources of the Colorado River, which opened the way for the construction of a dam.

Another problem was the financing of construction. The Boulder Canyon Dam Act, providing funding, was passed in 1928. The development of the project was led by John Savage, who later designed several more well-known dams. It was decided to build an arch-gravity concrete dam, which has the shape of an arc in plan, convex upstream of the river. The thickness of the dam at the base was supposed to be about two hundred meters, and at the top - fourteen meters. The dam was intended for motor traffic.

Funds for the construction of the dam were allocated in the summer of 1930 by President Hoover, and work began in the spring of 1931. The construction was led by Frank Crowe, who had extensive experience in the construction of dams. The project was supposed to initially build a city for builders - Boulder City. However, during the Great Depression, it was important to provide jobs for as many people as possible, so the construction of the dam began six months earlier than planned, placing workers in temporary camps. Only at the end of 1931, the houses built in Boulder City began to be populated. It should be noted that all this takes place in the very hot climate of Nevada.

Sculpture of a climber, built in 1995. The prototype was Joe Kine, a construction veteran.
During the construction of the Hoover Dam, protective helmets were first used in construction.

In order to divert the water from the river and free the construction site, two temporary dams were built, and four tunnels were cut into the rocks of the canyon, two from the Nevada side and two from the Arizona side. In June 1933 concrete work began. In Nevada, not far from the construction site, two concrete factories were built. Various innovative solutions were used during the construction. The construction of the dam was not monolithic, but consisted of many columns, between which pipes were laid. Water was supplied through the pipes to cool the concrete. After the columns solidified, the gaps between them were filled with a solution. This solution made it possible to avoid cracking of concrete during solidification.

At the time of its construction, the Hoover Dam was the largest man-made structure in the world. Its height is 221 meters, and its mass is more than 6.6 million tons. The rated power of the power plant is 2080 megawatts, on average, the power plant generates 4.2 billion kWh of electricity per year.

The architectural design of the buildings of the dam was made by Gordon Kaufman in the Art Deco style. There are clocks on two towers, one of them shows the time in Nevada, the other in Arizona.

Arizona and Nevada are in different time zones. But in most parts of Arizona, clocks do not change to daylight saving time, so the time is the same in the summer. In winter there is a difference of one hour.

The construction of the dam was completed earlier than planned. The grand opening ceremony took place on September 30, 1935, by which time Franklin Roosevelt had become President of the United States.

According to official figures, 96 people died during the construction of the dam in 1931-1935. Some sources indicate the figure of 112 people, including those who died during the survey and preparatory work. It is believed that another 42 people died from carbon monoxide poisoning during the tunneling (officially - died of pneumonia).
Chilling legends circulate among the people about workers who fell into liquid concrete, whose corpses were never found. However, this could not happen. The dam was built from interconnected blocks one and a half meters high, seven meters wide and seven to eighteen meters long. Concrete was delivered to the block in buckets with a volume of six cubic meters. Five or six workers leveled and compacted the concrete, making sure there were no air pockets left in it. Each time after unloading the bucket, the level of concrete in the block increased by five to fifteen centimeters, depending on the horizontal dimensions of the block. It is impossible to drown in such a thin layer of concrete, and besides, the accident would not go unnoticed if there were several people at the facility. So there is no need to invent all sorts of horrors, especially since there were already plenty of difficulties during construction. The work was carried out in very difficult and dangerous conditions, in a very hot climate.

The dam was built during the reign of President Herbert Hoover, but these were the years of the Great Depression, and the president was extremely unpopular. Therefore, only in 1947 the dam was named after him, and before that it was called "Boulder Dam".

The construction of the giant dam, along with other waterworks, provided irrigation to the fields of Southern California and eliminated the threat of devastating floods. Electricity gave a powerful impetus to the development of the Southwest of the United States, including Las Vegas, which in the early 30s was a very small town. In the 80-90s, the power plant was reconstructed, and it continues to be one of the largest in the United States. About a quarter of the electricity produced is consumed by Nevada, a fifth by Arizona, and the rest by California.

Tourist groups have visited the dam since 1937. Nowadays, the dam is visited by more than a million people a year.

Highway 93 passed through the Hoover Dam, connecting Nevada and Arizona. In 2003, construction began on a bypass bridge over the Colorado River, and in 2010 it opened to traffic.

Now visitors can enter the dam from the Nevada side, after passing through the entrance control, you can cross the dam to the other side and climb, but then the road is closed, that is, you cannot enter the main highway in Arizona. Visitors can also enter the bridge on foot, but you cannot go to the other side. This is an excellent observation deck overlooking the power plant, the dam and the reservoir.

photo yevgeniy_lysyy

Water intake towers

Water intake towers and Lake Med - a reservoir created by a dam.

Lake Med is the largest reservoir in the United States.

Spillway

Clock on the water tower.

"Republic" - a monument to Oscar Hansen.

An image is made on the floor showing the position of the stars on the day of the grand opening on September 30, 1935.

Power line pole and visitor center.

There is an entrance fee to the visitor center. They show a film about the history of the construction of the dam. You can take a tour of the dam or the power plant. I took the second one and went down the elevator.

Turbine conduit.

Generators in the engine room.

The power plant has 17 turbine generators - nine on the Arizona side and eight on the Nevada side. (for some reason, only seven are visible here). In 1986-1993, the power plant was modernized and the turbogenerators were replaced.

generator rotor.

Control panels.

Then the elevator takes visitors back up, you can go to the observation deck, from where the view of the dam is somewhat different.

Bypass bridge over the Colorado River. Rising 260 meters above the Colorado River, the bridge is the second tallest bridge in the United States and the tallest concrete arch bridge in the world. The length of the bridge is 579m, and the central span is 320m.

Colorado River, bypass bridge and power plant building.

Power plant building.

Inclined poles of power lines.

Power plant diagram.

photo

An hour's drive from Las Vegas, there is a unique object recognized as a historical landmark and a national architectural monument of the United States of America - this is the Hoover Dam. A concrete dam, as high as a seventy-story building (221 m), is amazing. The huge structure is squeezed between the ledges of the Black Canyon and has been holding back the rebellious temper of the Colorado River for more than 80 years.

In addition to the dam and the operating power plant, tourists can visit the museum complex, admire panoramic landscapes, cross the border between Nevada and Arizona on an arched bridge located at a height of 280 meters. Above the level of the dam is a huge man-made Lake Mead, where it is customary to fish, boat and relax.

History of the Hoover Dam

The local Indian tribes call the Colorado the Great River Serpent. The river originates in the Rocky Mountains, which are the main range in the Cordillera system of North America. Every spring, the river, whose basin is more than 390 square meters. km, overflowed with melt water, as a result of which it overflowed its banks. It is not difficult to imagine the enormous damage caused by floods to farms.

By the 1920s, the issue was so acute that curbing the destructive power of Colorado became a political decision. Many want to know why the dam was built, and the answer is quite simple - to control the water level of the river. Also, the reservoir was supposed to solve the problem of water supply to the regions of Southern California and, first of all, to the intensively growing Los Angeles.

The project required serious capital investments, and as a result of debates and discussions, an agreement was signed in 1922. The government representative was Herbert Hoover, who was Secretary of Commerce at the time. Hence the title of the document, The Hoover Compromise.

But it took a long eight years until the moment when the government allocated the first subsidies for an ambitious project. Just at that time, Hoover was in power. Despite the fact that after the changes in the project it was known where the new construction site was, until 1947 it was called the Boulder Canyon Project. It wasn't until 2 years after Hoover's death in 1949 that the Senate made a final decision on the issue. From that moment on, the dam began to officially bear the name of 31 US presidents.

How the Hoover Dam was built

The contract for the construction of the dam as a result of competitive selection went to the group of companies Six Companies, Inc, which are commonly called the Big Six. Construction began in May 1931 and was completed in April 1936, well ahead of schedule. The project included the use of non-standard engineering solutions and good organization of the construction process:

1. The walls and ledges of the canyon were cleared and leveled at the initial stage of work. Rock climbers and demolition workers, who risked their lives every day, have a monument at the entrance to the Hoover Dam.
   
2. Water from the work site was diverted through the tunnels, which still exist, performing a partial supply of water to the turbines or its discharge. Such a system reduces the load on the dam and contributes to its stability.
   
3. The dam is constructed as a series of interconnected columns. A system was created to cool the concrete structures with running water to speed up the hardening of the concrete. Studies in 1995 showed that the concrete structure of the dam is still gaining strength.
   
4. In total, the casting of the dam alone required more than 600 thousand tons of cement and 3.44 million cubic meters. meters of filler. At the time of completion, the Hoover Dam was considered the most massive man-made object since time. To solve such a large-scale problem, two concrete plants were built.
   
   

The feat of the builders

The construction came at a difficult time, when there were many people without work and place of residence in the country. The construction literally saved many families, creating several thousand jobs. Despite the difficult conditions and the lack of basic amenities in the initial period, the flow of those in need of work did not dry up. People came with their families and settled in tents near the construction site.

Wages were hourly and started at 50 cents. The maximum bid was set at $1.25. At the time, that was decent money, coveted by thousands of unemployed Americans. An average of 3-4 thousand people worked at the sites daily, but in addition, additional work appeared in related industries. This rise was felt in the neighboring states, where there were steel mills, mines, factories.

Under the terms of the contract between the representatives of the contractor and the government, rules were agreed that limited hiring on the basis of race. The priority for the employer was specialists, military veterans, white men and women. A small quota was negotiated for Mexicans and African Americans, who were used as the cheapest labor force. It was strictly forbidden to accept people from Asia, especially the Chinese, for construction. The government had a bad experience building and rebuilding San Francisco, where the Chinese labor force has grown to become the largest in the US.

A temporary camp was planned for the builders, but the contractors adjusted the schedule to increase construction speed and jobs. The village was built only a year later. The Big Six resettled workers in capital houses, imposing a number of prohibitions on residents. When the dam was built, the city was able to receive official status.

For the builders it was not easy bread. In the summer months, the temperature could stay at the level of 40-50 degrees for a long time. Drifters and rock climbers risked their lives almost every shift. Officially, 114 deaths were recorded, but in reality there were much more.

Project value

The creation of the Hoover Dam cost America a huge amount for those times - 49 million dollars. In just five years, a construction project unique in scale was completed. Thanks to the reservoir, farms in Nevada, California and Arizona today have the necessary water supply and can fully develop irrigated agriculture. Cities throughout the region received a cheap source of electricity, which gave impetus to the development of industry and population growth. According to historians, the construction of the Hoover Dam is associated with the rapid development of Las Vegas - the gambling capital of America, which in a short period of time has turned from a small provincial town into a pompous metropolis.

Until 1949, the power plant and dam were considered the largest in the world. The Hoover Dam is a government property of the US government and plays an important role in supporting the balance of electricity consumption in the western regions of the country. The automated station control system was introduced in 1991 and works perfectly even without the participation of an operator.

The Hoover Dam is attractive not only as a unique engineering structure. Its architectural value is also noted, which is associated with the name of the famous American architect Gordon Kaufman. The external design of the dam, water intake towers, the museum and the memorial complex allowed the man-made structure to harmoniously fit into the panorama of the canyon. The dam is an extremely popular and recognizable object. It is hard to imagine a person who would refuse to take a photo against the backdrop of such breathtaking beauty.

That is why companies and public organizations like to organize advertising or protest actions in the Hoover Dam area. Hoover Dam is very popular with filmmakers. She was saved by Superman and the hero of the film "Universal Soldier", the hooligans Beavis and Butthet tried to destroy her. The touching Homer Simpson and the formidable army of Transformers encroached on the integrity of the concrete wall. And the creators of computer games looked into the future of the Hoover Dam and came up with a new form of existence for it after a nuclear war and a worldwide apocalypse.

Even after decades have passed, with the advent of even larger projects, the dam continues to amaze. How much perseverance and courage it took to create and build such a unique engineering structure.

Prior to the construction of the dam, the Colorado River often showed its turbulent temper, often flooding downstream farmlands during snowmelt in the Rocky Mountains. The designers of the dam planned that its construction would help smooth out fluctuations in the level of the river. In addition, the reservoir was expected to give impetus to the development of irrigated agriculture, as well as become a source of water supply for Los Angeles and other areas of Southern California.

At the same time, one of the obstacles to the implementation of the project was the doubts of the states lying in the Colorado River basin about the fair distribution of water resources among consumers. There were fears that California, with its influence, financial resources, and lack of water, would lay claim to much of the reservoir's water resources.

As a result, in 1922, a commission was created, which included one representative from each of the interested states and one from the federal government (Herbert Hoover, then Secretary of Commerce in the government of President Warren Harding). The result of the activities of this commission was the Colorado River Convention signed on November 24, 1922, which fixed the methods for dividing water resources. The signing of this document, called the Hoover Compromise, opened the way for the construction of the dam.

The construction of such a large-scale hydraulic structure required the attraction of significant funds from the state budget. The funding bill was not immediately approved by the US Senate and the White House. Only on December 21, 1928, President Calvin Coolidge signed a bill approving the implementation of the project. Initial appropriations for the construction of the dam were allocated only in July 1930, when Herbert Hoover was already president.

The original plan was to build a dam in Boulder Canyon. Boulder Canyon). Therefore, despite the fact that it was finally decided to build a dam in the Black Canyon, the project was called the Boulder Canyon Project.

The construction of the dam was planned in a narrow canyon on the border between Nevada and Arizona. To divert water from the Colorado River away from the construction site, four tunnels with a diameter of 17.1 m were drilled in the stone walls of the Black Canyon. The total length of the tunnels was 4.9 km. The construction of the tunnels began in May 1931. The lining of the tunnels was made of concrete 0.9 m thick, as a result, the effective diameter of the conduits was 15.2 m. and disposal of excess water. The fact that the spillway is carried out not through the body of the dam (as on the Sayano-Shushenskaya hydroelectric power station, built later on the same principle as the Hoover dam), but through tunnels located in the surrounding rocks, gives stability to the dam.

To isolate the construction site and prevent possible flooding by the waters of the river, two caisson dams were built. The construction of the upper dam was started in September 1932, despite the fact that the outlet tunnels had not been completed at that time.

In order to ensure the safety of work, before the start of the construction of the dam, measures were taken to clean the walls of the canyon from free-lying stones and rocks: they were blown up with dynamite and thrown down.

The contract to build the dam was awarded to Six Companies, Inc., a joint venture between the Morrison-Knudsen Company of Boise, Idaho; Utah Construction Company (Ogden, Utah); Pacific Bridge Company (Portland, Oregon); Henry J. Kaiser & W. A. ​​Bechtel Company (Oakland, California); MacDonald & Kahn Ltd. (Los Angeles) and J. F. Shea Company (Portland, Oregon).

Many thousands of workers participated in the construction (the maximum number - 5251 people - in July 1934). According to the terms of the construction contract, the employment of immigrants from China was not allowed, and the number of black workers during construction did not exceed thirty people employed in the lowest paid jobs. It was planned that a whole town - Boulder City - would be erected for the builders next to the dam, but the construction schedule was adjusted in favor of accelerating and increasing the number of jobs (this was done to reduce the massive unemployment that resulted from the Great Depression). In this regard, at the time of the appearance of the first workers, the city was not yet ready, and the builders of the dam spent the first summer in temporary camps. The delay in the delivery of housing and dangerous working conditions led to a strike that took place on August 8, 1931. The workers' uprising was dispersed with guns and clubs, but the pace of construction in Boulder City was increased, and by the spring of 1932 the workers had moved into permanent housing. Prostitution, gambling, and the sale of liquor were prohibited in Boulder City during construction. The ban on the sale of alcohol in the city lasted until 1969, and the ban on gambling still remains (this is the only such city in the state of Nevada).

The construction of the dam was carried out in difficult conditions. Part of the work was carried out in tunnels where workers suffered from excess carbon monoxide (some workers became disabled or even died as a result). The employer also announced that these diseases are the consequences of ordinary pneumonia, and he is not responsible for this. At the same time, the construction of the Hoover Dam was the first construction site to use safety helmets.

A total of 96 people died during construction. The first person to die building a dam was topographer J. Tierney, who drowned in Colorado in December 1922 in the process of choosing the best site for construction.

The first concrete was poured into the foundation of the dam on June 6, 1933. For the production of concrete, local deposits of non-metallic materials were discovered, and special concrete plants were built.

Since works of this scale had never been carried out before, a number of technical solutions used in the construction process were of a unique nature. One of the problems that engineers had to face was the cooling of concrete. Instead of a solid monolith, the dam was built as a series of interconnected trapezium-shaped columns - this allowed the excess heat released during the solidification of the concrete mixture to dissipate. Engineers have calculated that if the dam were built as a monolith, it would take 125 years for the concrete to cool completely to ambient temperature. This could lead to cracking and collapse of the dam. In addition, to speed up the cooling process of the concrete layers, each form that was poured contained a cooling system of 1-inch metal pipes into which river water entered. The hardening process of the concrete from which the dam is built has not been completed to this day.

In total, 600 thousand tons of Portland cement and 3.44 million m³ of aggregate were mixed into the concrete required for the construction of the dam body. The Hoover Dam at the time of its completion became the most massive artificial structure on earth, exceeding the mass of the masonry of the Giza Pyramids - the concrete used would be enough to build a 20-centimeter thick concrete road 5 meters wide from San Francisco to New York, that is, crossing the entire US from the Pacific to the Atlantic

The dam was originally to be built in Boulder Canyon, so despite the fact that construction actually began in Black Canyon, it was originally called "Boulder Dam" in official documents. But already at the official opening ceremony of the construction, Secretary of the US Department of the Interior Ray Wilbur announced that the dam would be named Hoover in honor of the current US president. With this statement, Wilbur continued the established tradition of naming the largest dams in the United States after the presidents in power at the time of their construction (for example, Wilson Dam or Coolidge Dam). On February 14, 1931, the US Congress approved the official name of the Hoover Dam.

In 1932, Hoover lost the election to Democratic nominee Franklin Delano Roosevelt. Immediately after the new president took office, the US administration initiated the renaming of the dam to the "Boulder Dam". No official decision was made on this matter, however, Hoover's name disappeared from all official documents and tourist guides of that time.

In 1947, two years after Roosevelt's death, California Congressman Jack Anderson submitted a draft decision to return the Hoover Dam. On April 30, the corresponding bill, approved by the Senate, was signed by the president; since then, the dam has had its modern name.

Before and After

And now she looks like this.

Address: USA, 48 km from Las Vegas, Colorado River
Start of construction: 1931
Completion of construction: 1936
Height: 221 m
Coordinates: 36°00"58.0"N 114°44"15.5"W

Short description

Virtually all tourists traveling in Las Vegas and the Grand Canyon pass through the Hoover Dam or Hoover Dam.

Hoover Dam from bird's eye view

This huge concrete dam, equal in height to a 70-story building, pacified the stormy temper of the Colorado River. The Hoover Dam controls flood levels, supplies water and provides electricity to Arizona, California, as well as the "gambling capital of the USA" - Las Vegas (Nevada).

Historians believe that it was not the gambling houses, but the construction of Hoover Dam that caused the development of Las Vegas, which turned from a village into a prosperous city.

Construction of the Hoover Dam

The construction of the Hoover Dam, begun in 1931, at the height of the Great Depression, contributed to the creation of new jobs for unemployed Americans. The construction of the dam was carried out in difficult conditions - the air temperature in summer rose to +50°C. Climbers were especially dangerous, and tunneling workers suffered from excess carbon monoxide. However, there were more than enough applicants for vacancies. According to official figures, 96 people died during the construction of Hoover Dam. In 2000, a monument to rock climbers was erected near the entrance to the dam: a worker with a flashlight and in a protective helmet hangs on a rope belay over a cliff.

It's interesting that The Hoover Dam was built in approximately the same years as the DneproGES (1932 - 1939). Moreover, the same engineer from the General Electric company, the American CJ Thomson, who was responsible for the installation of turbines and generators, took part in the construction of these hydraulic structures. In 1935, Soviet writers Ilf and Petrov visited the United States and visited a construction site.

They describe this “miracle of engineering” with admiration: “Imagine a stormy, mountainous Colorado River flowing through the bottom of a giant gorge, the walls of which are formed by high black-and-red rocks. And now, between these two walls created by nature, man created a third wall of reinforced concrete, blocking river flows.

Hoover Dam - an engineering marvel

The construction of the Hoover Dam was completed in 1936, two years earlier than planned. It was named after former US President Herbert Hoover. At one time, that is, in the mid-30s of the last century, Hoover Dam was a marvel of engineering. During its construction, many technical innovations were applied: to divert river flows from the construction site, four channels were cut down in the walls of the Black Canyon, and the dam itself was not built in the form of a solid monolith, but as a series of interconnected trapezoidal blocks - due to the smaller surface area, the concrete mixture cooled faster and solidified. Scientists have calculated that if the dam were built in one piece, then the complete solidification of concrete would be completed in 125 years.

Power plant at the Hoover Dam

The Hoover Dam is the tallest dam in the Western Hemisphere and one of the largest power plants in the United States.. Today, the plant has 17 turbines with a total capacity of 2074 MW. According to experts, the equipment control automation system is so well-established that the power plant will be able to work independently for two years without the supervision of employees, until the pipes become overgrown with algae.

Hoover Dam Bypass

At the top of the Hoover Dam was Highway 93, connecting Arizona and the Mexican border. With the onset of the 21st century, frequent traffic jams led to the need to build a bridge across the Black Canyon, bypassing the dam. In October 2010, the Mike O'Callaghan-Pat Tillman Memorial Bridge, better known as the Hoover Dam Bypass, was opened 500 meters from the dam. The bridge bears the names of Mike O'Callaghan, the former Governor of Nevada, and Pat Tillman, an American football player from Arizona who left a successful career and joined the US Army after the September 11, 2001 terrorist attacks to take revenge on the terrorists. The bridge is a grandiose arch structure 579 m long and 270 m high.

$ 240 million was spent on the construction of the Hoover Dam Bypass. The bridge receives 17 thousand cars daily, which made it possible to unload neighboring highways. Entertainment at the Hoover Dam 75 years have passed since the opening of the Hoover Dam, but this grand structure still attracts travelers. The Hoover Dam stands on the border of two states located in different time zones. Clocks are installed on the spillway towers, some of them show the time of the right bank of Nevada, others - the time of the left bank of Arizona. On one side of the dam, the defeated river flows calmly, on the other - the largest man-made lake in the United States - Mead, which has become a popular recreation area, stretches. Here you can go boating and water skiing, go fishing or sunbathe on the beach.

The dam is administered by the United States Bureau of Reclamation, a division of the United States Department of the Interior. In 1981, the dam was listed on the US National Register of Historic Places. The Hoover Dam is one of the most famous attractions in the Las Vegas area.

History of construction

Prior to the construction of the dam, the Colorado River often showed its turbulent temper, often flooding downstream farmlands during snowmelt in the Rocky Mountains. The designers of the dam expected that its construction would help smooth out fluctuations in the level of the river. In addition, the reservoir was expected to give impetus to the development of irrigated agriculture, as well as become a source of water supply for Los Angeles and other areas of Southern California.

At the same time, one of the obstacles to the implementation of the project was the doubts of the states lying in the Colorado River basin about the fair distribution of water resources among consumers. There were fears that California, with its influence, financial resources, and lack of water, would lay claim to much of the reservoir's water resources.

As a result, in 1922, a commission was created, which included one representative from each of the interested states and one from the federal government (Herbert Hoover, then Secretary of Commerce in the government of President Warren Harding). The result of the activities of this commission was the Colorado River Convention signed on November 24, 1922, which fixed the methods for dividing water resources. The signing of this document, called the "Hoover Compromise", opened the way for the implementation of the construction of the dam.

The construction of such a large-scale hydraulic structure required the attraction of significant funds from the state budget. The funding bill was not immediately approved by the US Senate and the White House. Only on December 21, 1928, President Calvin Coolidge signed a bill approving the implementation of the project. Initial appropriations for the construction of the dam were allocated only in July 1930, when Herbert Hoover was already president.

The original plan was to build a dam in Boulder Canyon. Therefore, despite the fact that it was finally decided to build a dam in the Black Canyon, the project was named Boulder Canyon Project.

Construction

The contract to build the dam was awarded to Six Companies, Inc., a joint venture between the Morrison-Knudsen Company of Boise, Idaho; Utah Construction Company (Ogden, Utah); Pacific Bridge Company (Portland, Oregon); Henry J. Kaiser & W. A. ​​Bechtel Company (Oakland, California); MacDonald & Kahn Ltd. (Los Angeles) and J. F. Shea Company (Portland, Oregon).

Many thousands of workers participated in the construction (the maximum number - 5251 people - in July 1934). According to the terms of the construction contract, the employment of immigrants from China was not allowed, and the number of black workers during construction did not exceed thirty people employed in the lowest paid jobs. It was planned that a whole town - Boulder City - would be erected for builders next to the dam, however, the construction schedule was adjusted in favor of accelerating and increasing the number of jobs (this was done to reduce the massive unemployment that resulted from the Great Depression). In this regard, at the time of the appearance of the first workers, the city was not yet ready, and the builders of the dam spent the first summer in temporary camps. The delay in the delivery of housing and dangerous working conditions led to a strike that took place on August 8, 1931. The workers' uprising was dispersed with guns and clubs, but the pace of construction in Boulder City was increased, and by the spring of 1932 the workers had moved into permanent housing. Boulder City banned prostitution, gambling, and the sale of liquor for the duration of construction. The ban on the sale of alcohol in the city lasted until 1969, and the ban on gambling remains to this day. In other cities of the state of Nevada, gambling is allowed, complete decriminalization occurred in 1931 (Assembly Bill 98) just to increase state revenue for the construction of a dam.

The construction of the dam was carried out in difficult conditions. Part of the work was carried out in tunnels where workers suffered from excess carbon monoxide (some workers became disabled or even died as a result). The employer, however, announced that these diseases are the consequences of ordinary pneumonia, and he is not responsible for this. At the same time, the construction of the Hoover Dam became the first construction site to use hard hats by construction workers.

A total of 96 people died during construction. The first person to die building a dam was topographer J. Tierney, who drowned in Colorado waters in December 1922 while choosing the best site for a building.

Preliminary work

The dam was planned to be built in a narrow canyon on the border between Nevada and Arizona. To divert water from the Colorado River away from the construction site, four tunnels with a diameter of 17.1 m were drilled in the stone walls of the Black Canyon. The total length of the tunnels was 4.9 km. The construction of the tunnels began in May 1931. The lining of the tunnels was made of concrete 0.9 m thick, as a result, the effective diameter of the conduits was 15.2 m. turbines and discharge of excess water. The fact that the spillway is carried out not through the body of the dam (as on the Sayano-Shushenskaya hydroelectric power station, built later on the same principle as the Hoover dam), but through tunnels located in the surrounding rocks, gives stability to the dam.

To isolate the construction site and prevent possible flooding by the waters of the river, two caisson dams were built. The construction of the upper dam was started in September 1932, despite the fact that the outlet tunnels had not been completed at that time.

In order to ensure the safety of work, before the start of the construction of the dam, measures were taken to clean the walls of the canyon from free-lying stones and rocks: they were blown up with dynamite and thrown down.

Construction of a concrete dam

The first concrete was poured into the foundation of the dam on June 6, 1933. For the production of concrete, local deposits of non-metallic materials were discovered, and special concrete plants were built.

Since works of this scale had never been carried out before, a number of technical solutions used in the construction process were of a unique nature. One of the problems that engineers had to face was the cooling of concrete. Instead of a solid monolith, the dam was built as a series of mutually connected columns in the form of trapezoids - this allowed the excess heat released during the solidification of the concrete mixture to dissipate. Engineers have calculated that if the dam were built as a monolith, it would take 125 years for the concrete to cool completely to ambient temperature. This could lead to cracking and collapse of the dam. In addition, to speed up the cooling process of the concrete layers, each form that was poured contained a cooling system of 1-inch metal pipes into which river water entered. The hardening process of the concrete from which the dam is built has not been completed to this day.

In total, 600 thousand tons of Portland cement and 3.44 million m³ of aggregate were mixed into the concrete required for the construction of the dam body. The Hoover Dam at the time of its completion became the most massive artificial structure on earth, exceeding the mass of the masonry of the Pyramids of Giza - the concrete used would be enough to build a 20-centimeter thick concrete road 5 meters wide from San Francisco to New York, that is, crossing all United States from the Pacific to the Atlantic.

Power station

The development of a pit for the hydroelectric facilities was carried out simultaneously with the digging of a pit for the foundation of the dam. The earthworks for the U-shaped structure at the foot of the dam were completed at the end of 1933, and the first concrete for the power plant building was poured in November of that year.

architectural solution

The initial project provided for a fairly simple architectural solution for the dam and the building of the hydroelectric power station. It was assumed that the outer side of the dam would be an ordinary wall, framed on top with a neo-Gothic balustrade. The building of the power plant should not have differed much from the usual factory workshop.

The proposed project was criticized by many contemporaries for its simplicity, which, in their opinion, did not correspond to the epochal nature of the building. As a result, Los Angeles architect Gordon Kaufman was invited to rework the project. (English) Russian(author of the design of the Los Angeles Times editorial building). Kaufman managed to rework the project by completing the exterior of the buildings in the tradition of Art Deco style. The upper part of the dam is decorated with turrets that "grow" from the dam itself. There are clocks on the spillway towers, one of them shows Mountain Time (Arizona), and the other - North American Pacific Time (Nevada).

Dam name

The dam was originally to be built in Boulder Canyon, so despite the fact that construction actually began in Black Canyon, it was originally called "Boulder Dam" in official documents. But already at the official opening ceremony of the construction, Secretary of the US Department of the Interior Ray Wilbur announced that the dam would be named Hoover in honor of the current US president. With this statement, Wilbur continued the established tradition of naming the largest dams in the United States after the presidents in power at the time of their construction (for example, the Wilson dam or the Coolidge dam). On February 14, 1931, the US Congress approved the official name of the Hoover Dam.

In 1932, Hoover lost the election to Democratic nominee Franklin Delano Roosevelt. Immediately after the new president took office, the US administration initiated the renaming of the dam to the "Boulder Dam". No official decision was made on this matter, however, Hoover's name disappeared from all official documents and tourist guides of that time.

In 1947, two years after Roosevelt's death, California Congressman Jack Anderson submitted a draft decision to return the Hoover Dam. On April 30, the corresponding bill, approved by the Senate, was signed by the president; since then, the dam has had its modern name.

transport value

Until 2010, Highway 93 (Route 93) passed along the dam, lying in the meridional direction and connecting the state of Arizona with the Mexican border. The part of the highway adjacent to the dam did not correspond to the highway and the volume of traffic passed. The road has only one lane in each direction; its serpentine, descending to the dam, includes several sharp and narrow turns, as well as places with poor visibility; the road is prone to landslides.

Power supply

According to the United States Bureau of Reclamation, the electricity generated by the station is distributed in the following ratio:

Statistics

Environmental impact

The construction of the Hoover Dam and the formation of the Mead Reservoir had a significant impact on the water regime of the Colorado River, and especially on the ecosystem of its delta. During the six years of the construction of the dam and the filling of the reservoir, the water practically did not reach the delta. The estuary of the delta, which before the construction of the dam was a mixing zone of salt and fresh water, reaching a length of 64 km, actually turned into a salty estuary.

The construction of the Hoover Dam stopped the floods that were not uncommon in the lower reaches of the Colorado, it endangered a number of animal and plant species that have adapted to regular flooding. The construction of the dam markedly reduced the fish population downstream. Currently, four species of typical Colorado fish ( Gila elegans, Ptychocheilus lucius, Gila cypha And Xyrauchen texanus) have the status of endangered .

To this day, the area around Mead Reservoir shows a trace of the high water level reached in 1983. The reason for such a significant increase in the level was the unusually high amount of precipitation that fell in the western part of the United States as a result of the El Niño effect.

Images

Notes

1. Hoover Dam - Lake Mead - Hoover Dam Bridge - Boulder Dam - DesertUSA (indefinite) . // desertusa.com. Retrieved August 23, 2011. Archived from the original on August 28, 2011.
2. Hiltzik, Michael A. Colossus: Hoover Dam and the Making of the American Century. - New York: Free Press, 2010. - P. 81-87. - ISBN 978-1-4165-3216-3.
3. Stevens, Joseph E. Hoover Dam: An American Adventure. - Norman, OK: University of Oklahoma Press, 1988. - P. 26-27. - ISBN 0-8061-2283-8.
4. Construction of Hoover Dam: a historic account prepared in cooperation with the Department of the Interior. KC Publications, 1976.

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