Everything about the Hoover Dam is unfathomably enormous—and it went up in less than three years during America’s worst depression
Hoover Dam straddles the Colorado river at the Nevada-Arizona border. Its sides grip the edges of Black Canyon; its back strains to contain the deep reservoir behind it. At 726.4 feet high, the dam rises more than 70 stories above the powerhouses at its base and contains enough concrete to build a sidewalk four feet wide and three inches thick around the entire planet. The artificial lake it created can contain enough water to cover the entire state of Pennsylvania a foot deep.
An army of workers raised this prodigy in rugged and desolate country, where summer temperatures often reached 130. Officially, about 100 people died building it. They were killed by falling rocks or in dynamite explosions; they were run over by trucks and crushed by heavy equipment; they died in falls from canyon walls, or from heat exhaustion. Contrary to persistent rumor, none of them are entombed in the dam.
A plaque at the dam commemorates the men who lost their lives here. “They died to make the desert bloom,” it reads. It could just as appropriately have read, “They died to tame a river.”
Before they could start raising the dam, workers had to shift the river from its eons-old bed so they would have a dry place to work.
Before Hoover Dam the Colorado was notoriously bipolar, wild and dangerous when swollen with snowmelt, a mere trickle of its former self during the summer months. The dam smooths out the mood swings. When the river rampages, the dam contains its excesses in its huge reservoir. During dry periods, when the crops in California’s Imperial Valley would otherwise be withered by the sun, the reservoir provides a steady supply of life-giving water that is distributed through a network of canals. The reservoir also filters out the river silt that had clogged earlier canal systems, and the water’s passage through the dam’s turbines generates electricity—enough electricity, in fact, to make Hoover Dam a profit center for the U.S. government.
Bringing all this about required a complex web of inter-related systems, many of which would have been grand construction projects by themselves. The project needed railway lines, highways, bridges, and cableways to bring supplies and workers to the construction site. It needed specialized facilities to make pipe and concrete, and an entire town, built from scratch, to house the laborers.
Before they could start raising the dam, workers had to shift the river from its eons-old bed so they would have a dry place to work. They did that by blasting four huge diversion tunnels— each high enough to contain a five-story building and wide enough for a four-lane highway—through the walls of Black Canyon. They dug more tunnels through which water would flow from the reservoir to the turbines in the power plants. They erected cofferdams—small dam projects in their own right—to ensure that the unpredictable Colorado wouldn’t flood the tunnels as they were being dug.
Once the river began flowing through the tunnels and around the work site, laborers scraped the riverbed down to bedrock so the dam would have a firm and steady base. Only after more than two years of backbreaking work did teams begin pouring concrete for what was then the world’s biggest dam. In the meantime, other teams were building and installing systems of huge pipes called penstocks to guide the river water to turbines installed in a pair of 20-story powerhouses nestled at the dam’s foot.
|An electric shovel at the mouth of one of the mammoth diversion tunnels.|
|(Courtesy of the U.S. Bureau of Reclamation.)|
“All its features are superlatives,” wrote Elwood Mead, the head of the federal bureau in charge of building the dam, and the man whose name was given to the giant artificial lake behind it. The project, wrote The New York Times in a spate of superlatives in 1932, required “the biggest trucks,” “a world’s record X-ray job” and the “largest cement-mixing plant in the world.” The equipment was “too big and too complicated for the layman to grasp without extensive comparative pictures and diagrams,” said Forbes magazine. The dam itself, The Literary Digest declared, was “the greatest engineering structure of the twentieth century.”
“What stirs the imagination is not so much the size as the nature of the undertaking”—this is the Times again. “The fellow who stole fire from heaven was hardly more presumptuous.”
That would make Arthur Powell Davis, the engineer whose studies began the dam, a twentieth-century Prometheus. Davis had a family connection with the Colorado River. His uncle was John Wesley Powell, the one-armed adventurer who had made expeditions down the river in the later 1800s. Davis graduated from Columbian University in Washington, D.C. (later renamed George Washington University), and worked for a time as a hydrographer for the Isthmian Canal Commission before joining the U.S. Reclamation Service as its chief engineer in 1902. The department, later renamed the Bureau of Reclamation, was responsible for managing water resources.
High up on the canyon walls, these workers wielded jackhammers and air hoses from precarious perches as they cleared away loose rock and made cuts.
Davis understood the Colorado’s potential and its problems. The river, which originated in the Colorado Rockies and traveled for 1,700 miles to the Gulf of California, was a dangerous, untrustworthy neighbor. Starting in 1905, farmers in California’s Imperial Valley experienced its vicious side when the river burst the confines of the canals they used for irrigation and flooded their land, ultimately creating California’s largest lake, the Salton Sea, in the middle of the Sonoran Desert. (See Invention & Technology, Winter 2006). Davis knew that a tamed Colorado would ensure that this once-arid desert remained productive farmland. Better yet, by generating electricity, a dam on the Colorado could pay for itself even as it helped light up the American West. So in 1920 the bureau began surveying the Colorado for possible dam sites, and two years later it released the Fall-Davis Report (Albert Fall being the Secretary of the Interior), which recommended building a dam “at or near Boulder Canyon.”
The stage had been set, but except for one brief encore, Davis’s role in the project was over. Politics prompted his resignation from the Bureau in 1923. Ten years later the Roosevelt administration named him a consulting engineer on the project, but he died a month later.
On November 24, 1922, representatives of the federal government and the seven states that would be altered by the dam signed the Colorado River Compact, an agreement about the allocation of the river’s waters. Arizona refused to ratify the agreement, but the United States changed the rules so it required approval from only six of the seven states involved. In 1928 Congress finally passed the Boulder Canyon Project Act. President Calvin Coolidge signed the act into law on December 21, 1928.
The dam would not rise in Boulder Canyon, however. Geologists, using diamond drills on barges stabilized by cables attached to the canyon walls, determined that the rock in Black Canyon, about 20 miles downstream, was more stable, although the site was equally inhospitable. “There is no hotter or more desolate scene on the Colorado,” wrote a reporter for Fortune magazine in 1931.
The dam would be a huge arch, thick at the base and tapering in width until it was 45 feet wide at the top—still spacious enough to carry traffic along the quarter-mile crest. It would be exceptionally strong, able to withstand stresses of up to 40 tons per square foot. There had never been such a dam.
|Drillers prepare the steep canyon wall for blasting, 1933.|
|(Courtesy of the U.S. Bureau of Reclamation.)|
No single company could tackle so vast a project—and few could afford the $5 million bond required from the winning bidder. Instead, six West Coast companies formed a consortium exclusively to build the dam: the Henry J. Kaiser and W. A. Bechtel Company; Utah Construction; the MacDonald and Kahn Company; the J. F. Shea Company; the Pacific Bridge Company; and the Morrison-Knudsen Company. The new entity called itself Six Companies and made its headquarters in San Francisco. Six Companies submitted a winning bid of $48,890,995, the biggest federal contract in history at the time.
Six Companies picked Francis Trenholm “Frank” Crowe to oversee the work. Dams had defined the Quebec native ever since he graduated from the University of Maine with a civil engineering degree in 1905. A summer job with the reclamation service had also sparked a lifelong love of the Western outdoors. Crowe served as a government engineer for the Tieton Dam in Washington and as superintendent for the Jackson Dam in Wyoming. He had worked on dams in North Dakota, California, and Idaho for the Morrison-Knudsen Company. Always eager to further the technology, he had designed a pneumatic tube system for transporting concrete, and he was an enthusiastic proponent of cableway systems for dam work.
A dedicated cadre of workers followed Crowe from job to job, for he inspired those who worked for him. He was big and tough, wore a Stetson on the job, and insisted that correspondence should never be longer than a page. He took no vacations. “He is tall, talks loudly, and laughs hard,” said Fortune. “He conveys an irresistible impression of drive, and translates it into almost magical results. The men dislike to work that hard, but they like Crowe. They work that hard.”
Walker Young, the engineer in charge for the Bureau of Reclamation, looked over Crowe’s shoulder. Young, 48, had graduated from the University of Idaho, where he studied mining and played basketball. He and Crowe had worked together on Idaho’s Arrowrock Dam, and they maintained a good working relationship on the Hoover Dam project, despite the different demands on them. Crowe was under pressure to meet deadlines, while Young had to make sure the work was done to specifications. “Sometimes we fight with each other for the fun of it,” said Young, who nicknamed Crowe “Hurry Up.” Crowe, in turn, referred to Young as “the Great Delayer.”
Crowe visited the dam site for the first time on March 12, 1931, and surveyed Black Canyon from a small boat. If the stark canyon walls and desolate location gave him pause, he didn’t show it. Later that month, Six Companies began bringing in equipment, including eight Westinghouse electric shovels that had to be floated down the river on barges. Unemployed men, which Depression-era America had in abundance, began coming. “Hundreds of families are already ‘squatting’ along the highway leading from Las Vegas to the dam site and are threatening to become a major problem,” The New York Times reported in May 1931. “A tenderfoot on the desert in the Summer time is a pitiable object. Stay away.”
|Boulder City sprang up in the desert to house the dam workers.|
|(Courtesy of the U.S. Bureau of Reclamation.)|
It was good advice, and it was ignored, to the point where President Herbert Hoover requested that work begin as soon as possible to provide jobs. While more permanent homes were still in the works at Boulder City, about seven miles from the dam site, workers lived at Williamsville, a squatters’ settlement on the floodplain near the river named after the local U.S. marshal. Workers also called it Ragtown; someone painted hell hole on a rock nearby.
The harsh conditions took their toll. Workers sweltered in the desert heat, and many succumbed to heat prostration. Others fell prey to their own inexperience and Six Companies’ demands for speed. In 1931 Victor Castle wrote a Los Angeles attorney about working conditions, a letter that the Nation magazine published under the title “Well, I Quit My Job at the Dam.” “I heard all sorts of stories about men being blown up by premature explosions at the tunnel,” wrote Castle, who worked as a waiter at the construction camp. “The responsibility for this is variously laid to the faulty powder and improper mining methods. I am told that down at the dam site there is no medical or surgical help available, no hospital facilities, no first-aid equipment, no stretchers, no ambulances, nothing to protect the lives of the workers.
“So I quit. I would rather mooch on the main stem than work in a temperature around 140 for $2 a day, and my meals, and then have to pay $1.50 a month for insurance—particularly when the insurance companies specifically exempt the greatest element of danger, heat prostration.”
Workers, prodded by organizers from the Industrial Workers of the World, went on strike in August 1931. Six Companies refused to yield an inch. Crowe was loyal to his workers, but his ultimate loyalty lay with the project. “I was wild to build this dam,” he said many years later. Six Companies fired almost all its workers and announced it would hire new crews. “We are six months ahead of schedule on the work now and we can afford to refuse concessions which would cost $2,000 daily,” Crowe told a reporter from the San Francisco Examiner.
The strike collapsed, and work resumed. Conditions improved as the terrible summer mellowed into fall, and they improved even more following the construction of Boulder City. It was a company town, with a heavy-handed police force and strict regulations against bootleg liquor, but it provided workers with a decent place to live. When they wanted to blow off steam they could travel to Las Vegas, 30 miles away.
The payroll peaked at about 5,200 people, almost all white men. “Mongolians” (i.e., Chinese) were specifically banned from working on the dam, and later, even under pressure from the Roosevelt administration, Six Companies refused to hire more than a handful of black workers. All Secretary of the Interior Harold Ickes could do was pressure the company to allow these few workers to live in Boulder City instead of in West Las Vegas.
The rest of the force were white “working stiffs.” “His average age is thirty-three,” wrote Fortune. “His average wage is sixty-eight cents an hour. He is taller and heavier than the average U.S. soldier, runs a greater risk of losing his life, and has passed a more drastic physical examination… . He likes hunting better than baseball, horse racing better than either. He’ll pick a grudge, or smell bad luck, mosey out and hit the road or the rails, but while he works he is inspired with a devil of loyalty, shrewdness, and skill.”
The task of digging the four diversion tunnels officially began on July 4, 1931, when Secretary Wilbur, accompanied by Elwood Mead and some members of Congress, pushed a button that set off the first dynamite charge. There would be four tunnels, two on each side of the river, 56 feet in diameter, with an average length of 4,000 feet. The workhorse of the tunneling operation was called a jumbo, a series of platforms knocked together on the frame of a 10-ton truck. Workers would back the jumbo into position against the rock and stabilize it, then climb on its platforms to drill holes for the dynamite charges.
Then they packed dynamite into the holes, removed everything from the tunnel, and set off the charges. Huge blowers forced out the smoke and fumes, and the workers rushed back to clean out the “muck,” as they called the broken rock. A bulldozer pushed the muck to electric shovels, which loaded it into trucks. There was little space for dump trucks to turn around, so the operators learned to drive backward down the steep accessways into the canyon, usually balanced precariously as they craned to look behind them.
|An improvised set of platforms called a jumbo allowed 30 men to drill at once.|
|(Courtesy of the U.S. Bureau of Reclamation.)|
As the tunnels lengthened, Six Companies ran up against another problem. Carbon monoxide from gasoline-powered dump trucks began sickening workers in the tunnels. Company doctors routinely listed the respiratory problems as pneumonia, but Nevada’s inspector of mines ordered a switch to electric vehicles. Six Companies kept on using the gasoline trucks even as it fought, and eventually defeated, the order in court. Civil suits that were later filed alleging carbon-monoxide poisoning ended with out-of-court settlements after some of the trials were tainted by rumors of jury tampering by Six Companies.
Nevada’s mine inspector could do little to impede the dam’s progress, and neither could the Colorado River. In February 1932 a flash flood destroyed a temporary bridge and flooded three of the tunnels. All work stopped, and a worker named George Carr suffered a shock when the rising waters inundated his electric shovel. Co-workers got a rope around Carr and dragged him to safety, and his injuries proved minor. Work resumed once the water levels receded.
Workers lined the tunnels with a three-foot concrete casing, and after trucks dumped thousands of loads of broken rock into the river to create a barrier below the upstream tunnel entrances, the Colorado began flowing through its man-made detour on November 14, 1932. To make sure the river stayed there, workers built two cofferdams, one just below the tunnels’ upstream entrances, and the other just upstream from the downstream exits. The upstream cofferdam was 450 feet long and 98 feet high, with a 750-foot-thick base. The downstream cofferdam, an insurance policy in case the river backed up beyond the tunnel mouths, was somewhat smaller. To protect the downstream cofferdam from destructive backwater, workers also constructed a 54-foot-tall rock barrier below it.
The once-desolate valley in the middle of the desert had been transformed into a hive of human activity. “Men are hanging by ropes against the sheer faces of the black cliffs, chiseling away at gigantic projections with jack-hammers,” wrote a reporter in 1933. “Men are backing and turning trucks in a criss-cross of rough paths at the bottom and on roads carved out of cliffs at incredible levels and angles. At the canyon wall’s foundations men are swarming around derricks which slash away at monumental piles of débris with excavator shovels. Men are driving lorries in and out of tiers of tunnels.”
Like an industrial-age ballet, bucket after bucket swung down from the canyon’s rim with clockwork precision, day after day, week after week.
High up on the canyon walls, these workers wielded jackhammers and air hoses from precarious perches on bosun’s chairs. They cleared away loose rock and made abutment cuts, the V-shaped notches on each side of the canyon walls in which the dam’s edges would fit. Observers suffered from vertigo just watching, but the high-scalers liked their work just fine. Sometimes they kicked off from the canyon walls to see how far out they could swing. Louis Fagen became known as “the Human Pendulum” after he spent three weeks transporting workers around a projecting rock. Passengers wrapped their legs around Fagen and held on for dear life as he kicked off and swung out and around to the other side of the projection.
On one occasion an engineer on the canyon rim slipped and began sliding down toward certain death. A high-scaler named Oliver Cowan, reacting with the speed of thought, grabbed the engineer’s legs as he fell past him. Cowan clung to the engineer, while another high-scaler swung over and pinned the man to the cliff wall. More workers dropped a line and pulled him to safety.
Other men were not so lucky as that engineer, but even as fatalities climbed, the job moved forward. Workers created a stable base for the dam by scraping the river bottom down to solid bedrock, a task that required the removal of another half-million cubic yards of material.
Finally it was time to actually make a dam. reclamation engineers had completed a series of tests at facilities in Washington, D.C., Berkeley, and Denver to determine the best mix of gravel, Portland cement, and sand for their cement. The gravel—from crushed rock called aggregate —came from a spot in Arizona just six miles away from the dam site. The rock was transported to a facility on the Nevada side to be cleaned and prepared, then taken to the mixing plant upstream. Later, Six Companies constructed a fully automatic mixing plant on the canyon rim.
The chemical reactions in drying concrete create heat, and engineers estimated that on its own, the dam would take more than a century to cool completely. As the concrete cooled, it would contract, leading to cracks and gaps in the structure.
Engineers investigated the possibility of blowing cool air through slots left in the dam’s concrete, or of using the gigantic air compressors that blew smoke from the tunnels as refrigeration units. They studied using crushed ice to mix the concrete, or even building the dam from pre-set concrete blocks rather than pouring concrete at the site. None of these methods appeared feasible. In the end the engineers picked a system that had been successfully tested on the Owyhee Dam in Oregon: a web of pipes embedded in the dam’s structure and pumped with cool water.
|Huge penstocks were built at a factory close to the dam site.|
|(Courtesy of the U.S. Bureau of Reclamation.)|
So instead of a single monolithic mass of concrete, the dam rose as a huge series of interlocking concrete blocks laced with one-inch cooling pipe. The pipes feeding the cooling system entered the dam through an eight-foot slot left open in the center. At first the system used river water, then water cooled at a specially constructed refrigeration plant. As the dam cooled, these feeder pipes were removed and the slots were filled. The embedded piping was drained and pressure-filled with concrete grout.
Concrete pouring started on June 6, 1933, with Frank Crowe personally signaling for the first bucket. The concrete came swooping down to the dam in 32-ton buckets lowered from cableways on the canyon rim. Once the cable operators lowered a bucket into position, workers opened its bottom and the oozing but rapidly drying contents poured out. Then seven “puddlers” stomped and paddled the concrete into a smooth layer within its wood-and-metal form. To make sure the concrete settled perfectly, the puddlers also shook it into position with pneumatic vibrators. After the blocks dried and cooled, concrete grout was injected into the gaps.
The great dam rose from the canyon floor. Like an industrial-age ballet, bucket after bucket swung down from the rim with clockwork precision, day after day, week after week, month after month. After two years and half a million buckets, the dam received its last load of concrete on May 29, 1935.
The completed dam was a means to several ends. One of them was to supply water to the turbines that would generate electrical power. As with everything involved with the dam, power generation required a host of projects with their own engineering and technical hurdles.
Power generation begins with four intake towers. Although only their tops poke above the surface of Lake Mead today, each tower is 33 stories tall.
The process started at the four intake towers. Although only their tops poke above the surface of Lake Mead today, each tower is 33 stories tall. Constructed of concrete and heavily reinforced with steel to resist earthquakes, they sit on rock shelves excavated from the canyon walls. The water flows into the towers through massive steel gates and then into huge pipes called penstocks. The largest penstocks were colossal—a period photograph shows a locomotive sitting inside one, with enough room left over to squeeze a second locomotive in on top of it. The pipes posed considerable technical challenges to Babcock & Wilcox, the Ohio company that built them. They were too large to be shipped by rail, so Babcock & Wilcox built them at a factory a mile and a half away from the dam site. It required cranes, hydraulic presses and bending rolls, welding machines, furnaces, grinders, borers, and X-ray machines to examine the welds—enough equipment for a large manufacturing facility in its own right.
Once the huge sections were ready, a special trailer transported them from the fabrication facility to the canyon rim. Awaiting them was a 1,256-foot-long cableway that spanned the canyon. The cableway lowered the penstocks to the entrance of an adit, an access tunnel dug into the side of the canyon. There each penstock section was chauffeured on a custom-made car. The hardest part of the job was hoisting the biggest sections up the steeply inclined tunnels to the base of each intake tower, a job that required 12 hours of patient work. Once they arrived, a specially designed assembly rig eased them into place. Steel pins rammed into pre-drilled holes locked the penstock sections into place.
Thirteen-foot penstocks branched off from the main penstocks to feed the 17 turbines in the powerhouses at the dam’s downstream face. The turbines were gigantic too. The one-story portion that projected above the powerhouse floor was just the tip. Below it were seven more stories of turbine.
On September 30, 1935, President Franklin Roosevelt visited the dam to speak at its dedication. Six Companies had started bringing equipment to the site just three-and-a-half years earlier. Since then, the largest masonry structure built since the Great Pyramid had risen to span Black Canyon. The diversion tunnels had been closed with permanent concrete plugs. Lake Mead had started filling in February, and it would keep filling for the next six years, until the water it contained weighed 41.5 billion tons. “Never before has man placed such an enormous weight on one spot of the earth’s crust,” wrote Science magazine, speculating that the weight could compress that crust more than seven inches.
Perhaps most amazing, the Six Companies had completed the dam ahead of schedule, thanks to the thousands of working stiffs who risked their lives to build it—and to Frank Crowe, who saw his life’s ambition embodied in the dam. “His genius at organizing, designing the construction plant, and moving materials in the most efficient manner was demonstrated by the fact that Hoover Dam was completed twenty-five months ahead of schedule,” said a posthumous tribute in Transactions of the American Society of Civil Engineers for 1948.
But the structure Roosevelt dedicated was called Boulder Dam. In 1932, Secretary of the Interior Ray Lyman Wilbur had named it Hoover Dam, after President Herbert Hoover. As Secretary of Commerce, Hoover had presided over the first meeting of the seven South-western states affected by the dam. Perhaps more important, he was Wilbur’s boss. The name didn’t sit well with the new administration, and FDR’s Secretary of the Interior, Harold Ickes, ordered it changed back to Boulder Dam, even though it had actually been built in Black Canyon. (In 1947 a Republican Congress officially changed the name back to Hoover Dam.)
Standing at the podium, Roosevelt gazed out on a sight that continues to awe visitors today. Five years earlier this place had been barren wilderness at the bottom of a deep and forbidding canyon. Now it was a colossus that could irrigate more than a million acres in the United States and half that in Mexico, and provide water for 18 million people throughout the Southwest. Until 1949 Hoover Dam would remain the largest hydroelectric installation in the world. At one point it provided 5 percent of the nation’s electricity. When America entered World War II, the current generated in Black Canyon helped transform Los Angeles into an industrial powerhouse for the war effort.
The dam had another impact, too, one that couldn’t be measured. Americans had raised a new wonder of the world in the middle of the Great Depression, a time when even mere survival seemed difficult. Despite the brutalities of Six Companies, the completed dam was something for them to all take pride in. Roosevelt realized that. “This is an engineering victory of the first order—another great achievement of American resourcefulness, skill and determination,” the President told the 10,000 people who had gathered for the dedication. “That is why I have the right to congratulate you, who have created Boulder Dam, and on behalf of the Nation to say to you, Well done!”