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America’s dam-building movement

  After Robert Fulton’s successful trial on the Hudson River in New York State in 1807, steam-engine ships sailed up the Mississippi River, opening up traffic and trade in the central United States.
  The river also powered textile manufacturing in New England.
  After 1865, railroads became the mainstay of American transportation, but grain and other bulk cargoes continued to be transported by barges and ships.
  In the 1890s, George Westinghouse pioneered the use of hydroelectric power. At the time, he was installing generators near Niagara Falls that sent power to Buffalo, New York, 20 miles away. As a result, hydropower has been promoted.
  After the onset of the Great Depression, the federal government embarked on ambitious infrastructure projects, on the one hand to alleviate unemployment and on the other to improve America’s future public infrastructure.
  Two federal agencies have influenced water projects across the country.
  The U.S. Bureau of Reclamation and the U.S. Army Corps of Engineers built dams to control flooding, improve inland navigation and increase the supply of electricity.
  The Hoover Dam on the Colorado River in the southwest, the most prominent of these public infrastructure projects, is twice as high as the tallest dam before it.
  Subsequently, dams were built in three regions west of the Mississippi: California’s Central Valley, the Columbia River in the Pacific Northwest, and the Missouri River in the Northern Plains.
“Water-sharing” agreement

  One of the great leaps in dam building in the 20th century began in the American Southwest, an arid region dominated by deserts and canyons and only crossed by one large river—the Colorado River.
  The Colorado River runs through a series of deep canyons, one of which is the spectacular Arizona Grand Canyon. Before dams were built along the river, the river’s flow at its mouth was 22,000 cubic feet per second.
  This flow also speaks to the region’s arid conditions, compared to the Mississippi River’s flow of nearly 600,000 cubic feet per second.
  Growing cities in Southern California need water.
  California’s need for water has alarmed other states in the Colorado Valley, where towns and farmers don’t want their neighbors to divert all the river’s water away.
  On November 24, 1922, in Santa Fe, New Mexico, U.S. Secretary of Commerce Herbert Hoover made a compromise among the seven Colorado River basin states and signed the Colorado Compact. ).
  The states agreed to allocate rights to the river, with upstream Wyoming, Colorado, Utah and New Mexico getting as much water as downstream Nevada, Arizona and California.
  As part of the 1922 Accord, the federal government owns land in the lower Colorado River and has also committed to building a dam on the lower Colorado River. The dam will control flooding and supply water for irrigation and other purposes, and Southern California (as the main beneficiary) will cover the cost of the dam’s construction.
  In 1928, a new public agency, The Metropolitan Water District, was created in Los Angeles and surrounding areas, and was authorized to collect taxes to build a canal to the Colorado River.
  The Metropolitan Water Authority persuaded Congress to pass the Boulder Canyon Act, which authorized the federal government to build a dam and build a canal on the U.S. side of the Mexican border to supply water to the Valley of the Kings.
  In December 1928, then-President John Calvin Coolidge Jr. signed the act into law.
  The dam did choose a good location, called the Black Canyon. In 1930, the Secretary of the Interior named this future project the Hoover Dam.
Design a giant dam

  The Bureau of Reclamation was tasked with building the Hoover Dam, and design work began in the early 1920s. The bureau decided to use concrete to build the dam, and two very different designs emerged.
  One is what engineers call a gravity dam, which relies on mass or weight to block the flow of water. Gravity dams require a lot of concrete.
  The other is the arched dam scheme, which uses its shape or form to slow the water potential. Arched walls can block water flow by transferring its horizontal force to the rock walls on either side, just as an arch bridge transfers its vertical weight and traffic weight to its piers.
  Compared to gravity dams, arch dams require much less material, but can do the same thing as blocking water flow.
  The arched design of the Hoover Dam was a radical idea for the Bureau of Reclamation at the time.
  The bureau has designed some smaller gravity dams with a certain curvature to increase their strength. Frank Weymouth, chief engineer of the bureau, in 1924. The gravity design of the Hoover Dam with a certain arch curvature is completed. Curvature is not necessary, as the enormous weight will keep the dam safe.
  What makes the dam design radical is its unprecedented scale and speed of construction. A young engineer, John L. Savage, took over at Weymouth and spent the next 5 years refining the design.
  By the 1920s, civil engineers had mastered how to design gravity dams—where the upstream side was nearly vertical and the downstream side had a flatter slope. This shape can be understood as a right-angled triangle formed by the upstream dam wall and the dam foundation.
  Engineers also understand the main force that the dam needs to resist, mainly the overturning force created by the water pressure on the dam, and a smaller upward pressure, called the buoyancy force, which may be caused by seepage under the dam. of. Using a few formulas, engineers can determine how much concrete a gravity dam needs to hold back the water behind the dam and keep it safe.
  On the night of March 28, 1928, a newly completed small-curvature gravity dam, the St. Francis Dam (40 miles northwest of Los Angeles), collapsed.
  It became the largest accident in the history of American engineering in the 20th century.
  The wall of water roared down a 50-mile valley and eventually into the Pacific Ocean, killing more than 400 people. Doubts have been raised about the design of the Hoover Dam.
  An investigation into the St. Francis Dam accident concluded that the accident was the result of faulty foundations and other defects in the design, not the design of the arch.
  A group of engineers examined the final design of the Hoover Dam and requested some additional concrete to make the dam’s foundation wider.

  Bureau of Reclamation engineer Jack Savage could have refused to add more concrete because the original design already used four times the amount of concrete needed for safety.
hard to build

  Plans for the construction of the Hoover Dam called for four tunnels to be dug into the canyon walls, two on each side of the Colorado River, each about 3/4 mile long and 50 feet in diameter. .
  These tunnels were dug to reroute the river so that structures could be erected on the dried up river bottom.
  The dam will rise 726 feet above the bedrock, twice the size of previous normal dams. The base will be 660 feet from back to front, and the foundation will taper at the top to 45 feet from back to front, wide enough to lay a road. The dam’s crest length, the arc of the crest from one wall of the canyon to the other, will be 1,282 feet.
  After the river is diverted, workers will build the dam out of concrete, which, when complete, will impound it to create a lake 115 miles long and 585 feet deep.
  After surveying the site and formulating a detailed construction plan, the Bureau of Reclamation tendered to private contractors in March 1931, and the winning bid was $48.8 million (equivalent to $700 million in 2010). companies” of the Western Enterprise Alliance.
  In the summer of 1931, construction of the dam began. To secure the winning bid, the Six Companies turned to Frank Crowe, a well-known construction engineer, and later hired him as the engineer for the construction of the Hoover Dam. He has a reputation for on-time completion and below-planned costs.
  Another University of Maine graduate, Gower’s colleague at the Bureau of Reclamation, Walker Young, remained with the Bureau of Reclamation after 1924 and worked as a supervising engineer on the Hoover Dam to ensure dam construction. meet the requirements.
  Gower needed to recruit new workers to replenish the construction team, and construction of the dam began in the spring of 1931, before the construction of site housing for the workers.
  The living conditions on the construction site are very rudimentary, with workers living in tents or shacks, with temperatures reaching 48°C during the day, and lack of water and food.
  After a group of workers went on strike to protest, Gower had to rehire other workers willing to take the job amid a deepening recession. In the fall of 1931, the dam workers were finally moved into air-conditioned rooms, with fresh water, adequate meals, and medical care.
  In the first year, the main work was to excavate four diversion tunnels.
  Gower had the workers work in three shifts, 8 hours a day and night, in the tunnel. Tunneling involves blasting the rock with explosives, clearing the rubble and then blasting it, moving only a few feet at a time.
  “If Goyle wasn’t in the office, he was under the dam. I wouldn’t be surprised to see him looking around below at 2am,” recalls one worker.
  Exhaust from motor vehicle engines damaged the health of some of the workers inside as the tunnel was dug deeper, but work continued to move forward.
  By early 1933, the tunnel had been fully dug through and concreted. While the workers were digging their tunnels deep into the rock, others, known as “height scalers,” were doing a more dangerous job:
  they drilled and chipped away the rocks to trim the canyon walls and make their surfaces more sturdy. Hard and smooth to connect with future dams.
renamed twice

  The U.S. economy is in a trough as work on the dam progresses. From the stock market crash in 1929 to the collapse of the U.S. banking system in early 1933, industrial production halved and the nation’s unemployed reached a quarter of the population.
  Franklin Roosevelt won the U.S. presidential election in 1932 with a promise of a New Deal for the American people, with federally funded new public works to boost economic recovery.
  After taking office in March 1933, Roosevelt affirmed the importance of the Hoover Dam to the nation. In order not to give credit to President Hoover, the interior secretary in Roosevelt’s administration renamed the dam the Boulder Dam.
  In the spring of 1933, Gower erected a temporary barrier, the “cofferdam”, on the upstream side of the river, diverting the Colorado River to a diversion tunnel, while a cofferdam on the downstream side blocked the flow of the Colorado River downstream, preventing backflow. . The barrier allows construction crews to dig the bottom of the river to bedrock.
  In June, construction crews began laying concrete for the body of the dam, mixing together sand, gravel and cement and pouring it into giant wooden boxes (molds) before hardening. Concrete releases heat as it sets, and pipes direct cold water into each wooden box, accelerating cooling to prevent cracks from forming.
  After the concrete is solidified, the gaps in the molds and boards removed by the construction workers are sealed with a cement mixture called “grouting”, and the pipes are also filled with grout to seal.
  Since the dam was being built higher than a crane could reach, Gower used one of his early dam-building innovations – an aerial ropeway that could carry a massive 6-ton mass of concrete, which was poured into the plank moulds below inside.
  The builders employed by Gower worked very discreetly, increasing the monthly volume of concrete poured from 28,000 cubic yards in June 1933 to 262,000 cubic yards in March 1934.
  When it was completed in February 1935, the project was completed 18 months ahead of schedule, and the dam had a concrete volume of 3.251 million cubic yards.
  On September 30, 1935, President Roosevelt inaugurated the dam.
  In 1938, the Southern California Metropolitan Water District completed a smaller hydraulic project here, the Parker Dam, and built a 242-mile pipeline connecting the dam to the Los Angeles area; further south, A low dam in Yuma, Arizona, where engineers from the Bureau of Reclamation built a new canal to supply water on the Mexican border.
  The new canal connects the Colorado River with the Valley of the Kings and the nearby Coachella Valley. Once these dams are built, agricultural production in the desert areas of Southern California will be possible.
  In 1938, the Hoover Dam power station began sending electricity to Los Angeles through a new transmission line, and in 1941 the Colorado Aqueduct to Los Angeles began supplying water. In 1947, the Republican-majority Congress changed the Boulder Dam back to its current name, the Hoover Dam.
  The overall design of the Hoover Dam is not subversive and innovative, but it has achieved a breakthrough in construction, and the height of the Hoover Dam is also unprecedented.
go on and on

  Civil engineers have encountered different challenges on other projects in California’s Central Valley, the Pacific Northwest, and the Missouri Valley.
  The Central Valley is 450 miles long, from which two rivers flow into inland California.
  The Sacramento River originates in the mountains adjacent to the Oregon border and flows into the delta south of the state capital Sacramento, where it joins the San Joaquin River, which flows northward from the Sierra Nevada to near Fresno. The two rivers then flow into the San Francisco Bay.

  Two-thirds of the Central Valley’s precipitation is concentrated in the northern part of the valley, often causing the Sacramento River to flood, while the San Joaquin and southern valleys receive little rain.
  In 1923, California water engineers issued a report urging the construction of reservoirs and channels in the north to prevent flooding and to divert excess river water to the south.
  By the early 1930s, these ideas had formed into a more comprehensive program: Build dams near the headwaters of each river to irrigate the northern and southern valleys and generate electricity. In 1937, the Roosevelt Administration designated the Bureau of Reclamation to build and operate the two dams as part of the Central Valley Project.
  The northern dam is called the Shasta Dam because of the nearby Mount Shasta, which intercepts the Sacramento River. Frankland Gower agreed to build Shasta Dam for Pacific Contractors Engineering, which won the contract.
  At the headwaters of the San Joaquin River, work on the southern dam, the Friant Dam, also began in July 1938 and was completed in 1942. The canal extends north, west, and south from the dam, delivering irrigation water to the San Joaquin Valley.
  Dams, canals and pumping stations have enabled rapid agricultural development in the Central Valley, which also includes the southern valley fed by the Colorado River, and California now supplies 50 percent of the nation’s fruits and vegetables.
  In the 1930s and 1940s, the federal government again began building dams along the Columbia River in the Pacific Northwest.
  To take advantage of the water here, the Corps of Engineers built a dam on the Columbia River in Bonneville, Oregon, 40 miles east of Portland, Oregon; Conlee), a dam was also built.
  To address unemployment in the United States in the 1930s, senators from each state agreed that if their state could build a dam, they would also support another state to build a dam.
  The timely completion of the Bonneville Dam and the Grand Coulee Gorge dam contributed unimaginably to U.S. productivity during World War II.
  These projects have also jointly reshaped the landscape west of the Mississippi River in the United States.
rich heritage

  The construction of the dam began in the 1930s, and its planning began in the 1920s.
  Planning for the Hoover Dam began with the Colorado River Accord in 1922, while the Central Valley Project arose out of a state initiative in 1923.
  The dams on the Columbia and Missouri rivers stem from the Rivers and Harbors Act of 1925, when Congress ordered the Corps of Engineers to survey major U.S. rivers to assess their hydroelectric potential. These investigations, known as “Report 308,” provided preliminary information on the Columbia River and the Missouri Dam.
  In the 1920s, the federal government had no plans to build dams and power generation facilities; Congress and the federal government believed that private utilities would make these investments if they were worthwhile. The Great Depression followed, and private investment on such a large scale was impossible.
  In 1933, the federal government began ambitious projects such as the Hoover Dam.
  The dam construction employed a fraction of the jobs lost by the Great Depression, but the projects offered hope to the country during the downturn.
  The benefits of dam construction in the Pacific Northwest have also come at the expense of river ecology.
  By 1940, hydroelectric supplies accounted for one-third of America’s electricity, and in 1941 provided much-needed electricity for World War II.
  After World War II, the growth in electricity demand exceeded the supply capacity of existing dams, but the number of large dams built in the United States reached its limit. In the late 20th century, the share of hydropower declined to about 9 percent of U.S. electricity generation.
  Dams in the American Southwest rely on ample rainfall to meet reservoir needs. By the end of the 20th century, drought had lowered water levels at the Hoover Dam and other dams. The Oroville Dam in California nearly collapsed at one point, when abnormal rainfall and the amount of water exceeded the warning line, and the emergency flood channel faced a huge test.
  The reservoir behind the Hoover Dam, Lake Mead, also silted up faster than expected.
  In 1956, the Bureau of Reclamation decided to build two new dams on the Green River, a tributary of the Colorado River in Utah, in order to reduce silt buildup and reserve more water for the upper Colorado River states in times of drought.
  Because the construction of these dams would flood Dinosaur National Monument, they were opposed by environmentalists, led by the Sierra Club.
  In a compromise, the Bureau of Reclamation agreed to cancel construction of the dam before deciding to build a new dam on the Colorado River in remote Arizona’s Glen Canyon, which was completed in 1966.
  In the 1930s, a third federal agency, the Tennessee Valley Authority, used dams and other measures to create a more modern and prosperous life in a water-rich region of the East. Through massive water and power projects, the federal government facilitated postwar development west of the Mississippi River.
  In a more direct way, the leaders of the Tennessee Valley Authority used public works to restructure society.

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