Water and Power Associates Informing the Public about Critical Water and Energy Issues facing Los Angeles and California

Background

Hoover Dam was constructed between 1931 and 1936 during the Great Depression. Its main purpose was to harness the Colorado River to prevent periodic catastrophic flooding, to allocate and distribute water, and to generate hydroelectricity for the Southwest. Even by today's standards Hoover Dam was a gigantic project. At the time it was the world's largest project made with concrete, not to mention the largest public works project in US history.

The dam's completion had a significant impact on Southern California and in particular Los Angeles, since the power generated by the dam contributed to more than 70% of the City's power needs at the time.

Historical Notes

Members of a water resources consulting committee (F. E. Bonner, A. J. Cleary, G. A. Elliot, B. A. Etcheverry, F. C. Herrmann, Louis C. Hill, W. L. Huber, A. Kempkey, J. B. Lippincott, William Mulholland, and C.S. Ridley) prepare to embark on a trip down the Colorado river, through Boulder Canyon, with representatives of the City of Los Angeles (William Mullholland, H. A. Van Norman, E. A. Bayley, H. C. Gardett, and S. Parratt) and the State of California (Paul Bailey and Gerald Jones).

More than 200 engineers worked to design the dam that would be constructed in Black Canyon. It would be the highest concrete arch dam in the United States, and the largest building project that the federal government had ever undertaken.*#

Historical Notes

Before a dam could be built, political work was necessary to resolve the competing claims on the river by different western states. As U.S. secretary of commerce, Herbert Hoover negotiated the Colorado River Compact, which divided the river basin into two regions, lower (Arizona, Nevada and California) and upper (Wyoming, Utah, New Mexico and Colorado) that would make the building of the dam possible.

In 1928, after years of lobbying to get a dam-building bill through Congress, the legislation was finally approved as the Boulder Canyon Project Act. Hoover, who that same year was elected as the 31st president of the United States, signed the bill into law in 1929.*#

Historical Notes

Construction efforts consisted of re-routing the river through canyon walls, blasting immense amounts of rock and dredging efforts to build on a bedrock foundation, construction of two diversion coffer dams, and pouring 6.6 million tons of concrete.

Historical Notes

Black Canyon has a width of from 290 to 370 feet at low-water level, and from 850 to 970 feet at elevation 1,232.  The top of the canyon walls is approximately 1,500 elevation. The foundation is a volcanic breccia or tuff, originally an accumulation of fragments of many kinds derived from volcanic eruptions, and now transformed into well-cemented, tough, durable mass of rock standing with remarkably steep walls.*

Historical Notes

“High Scalers” climbed down canyon walls on ropes to remove loose and weakened rocks along the canyon walls where the dam walls would join. Descending down the cliffs with the weight of tools, water and food, others would lower jackhammers to drill powder holes. The High Scalers would fill the holes with dynamite and after hand maneuvering out of the way of explosives, they went to work with crowbars to remove loosened rock.*^*

Historical Notes

Before construction could begin, the river was diverted around the dam site through four 50-foot-diameter tunnels, two drilled through the canyon walls on each side of the river. The tunnels, with a total combined length of 15,946 feet, or about three miles, were excavated to 56 feet and lined with three feet (300,000 cubic yards) of concrete. They could carry over 200,000 cubic feet - more than 1.5 million gallons - of water per second. The river was first diverted through the two Arizona tunnels on November 14, 1932.*#^

(ca. 1932)**# - Blasting away the sides of the canyon. More than 8.5 million pounds of dynamite was used to blast the foundation for the dam and 8 miles of tunnels through the canyon walls.

Historical Notes

The canyon walls were attacked first by batteries of compressed-air drills. An especially designed drilling jumbo equipped with 30 drills lumbered into action. When the drills had bitten 10 and 20 feet into solid rock a ton of dynamite was loaded into the holes. The electrically fired blast shook the walls. Power shovels moved to the tunnel face, and the broken rock was loaded into trucks. The trucks then roared up the grade to dump their loads in side canyons. Soon all was in readiness to repeat the performance.**#

(1932)^^# – Cableway lowered men and equipment into Black Canyon to work on the dam.

Historical Notes

The Jumbo Rig was designed to speed up the Hoover Dam's tunnel drilling process. Built on the back of a 10-ton truck, 24 to 30 drills could be operated at once.^

(1932)^^# – Penstock pipe sections were lowered into the canyon by a 150-ton capacity cableway, then carried in the tunnels on railroad cars.

Historical Notes

Forty-four thousand tons of steel were formed and welded into 14,800 feet of pipe varying from 8 1/2 to 30 feet in diameter. Each length of the largest pipe - 12 feet long, 30 feet in diameter, and 2 3/4 inches thick - was made from 3 steel plates, of such weight that only two plates could be shipped from the steel mill to the fabricating plant on one railroad car. Two such lengths of pipe welded together make one section weighing approximately 135 tons or, at intersections with the penstocks, as much as 186 tons.^*^

Historical Notes

Each of the 4 diversion tunnels was holed out to 56-foot diameter—as high as a 4-story building—and lined with a 3-foot thickness of concrete. The total length of the tunnels was approximately 3 miles.**#

Historical Notes

The four tunnels would have another important use besides diversion of the river. After completion of the dam, they would serve to house the outlet works used in the regulation of the reservoir. The two outer tunnels would become outlets for the huge spillways. The two inner tunnels would guide the stored water from the intake towers in the reservoir to the power plant or past it to the outlet valves below the dam.**#

Historical Notes

The first concrete was poured into the dam on June 6, 1933, 18 months ahead of schedule.^

Historical Notes

Since concrete heats and contracts as it cures, the potential for uneven cooling and contraction of the concrete posed a serious problem. Bureau of Reclamation engineers calculated that if the dam was built in a single continuous pour, the concrete would take 125 years to cool and the resulting stresses would cause the dam to crack and crumble. Instead, the ground where the dam was to rise was marked with rectangles, and concrete blocks in columns were poured, some as large as 50 feet square and 5 feet high.^

Historical Notes

Each five-foot form contained a series of 1 inch steel pipes through which first cool river water, then ice-cold water from a refrigeration plant was run. Once an individual block had cured and had stopped contracting, the pipes were filled with grout. Grout was also used to fill the hairline spaces between columns, which were grooved to increase the strength of the joins.^

Historical Notes

A total of 3,250,000 cubic yards of concrete was used in the dam before concrete pouring ceased on May 29, 1935. In addition, 1,110,000 cubic yards were used in the power plant and other works. More than 582 miles of cooling pipes were placed within the concrete. Overall, there is enough concrete in the dam to pave a two-lane highway from San Francisco to New York.  Concrete cores were removed from the dam for testing in 1995; they showed that "Hoover Dam's concrete has continued to slowly gain strength" and the dam is composed of a "durable concrete having a compressive strength exceeding the range typically found in normal mass concrete".[65] Hoover Dam concrete is not subject to alkali–silica reaction (ASR), as the Hoover Dam builders happened to use nonreactive aggregate, unlike that at downstream Parker Dam, where ASR has caused measurable deterioration.^

Historical Notes

The concrete was delivered in huge steel buckets 7 feet high and almost 7 feet in diameter. These buckets, which weighed 18 tons when full, were filled at two massive concrete plants on the Nevada side, and were delivered to the site in special railcars. The buckets were then suspended from aerial cableways which were used to deliver the bucket to a specific column. As the required grade of aggregate in the concrete differed depending on placement in the dam (from pea-sized gravel to 9-inch stones), it was vital that the bucket be maneuvered to the proper column. When the bottom of the bucket opened up, disgorging 8 cu yd of concrete, a team of men worked it throughout the form. Although there are myths that men were caught in the pour and are entombed in the dam to this day, each bucket deepened the concrete in a form by only an inch, and Six Companies engineers would not have permitted a flaw caused by the presence of a human body.^

Historical Notes

Excavation for the powerhouse was carried out simultaneously with the excavation for the dam foundation and abutments.  The powerhouse was one of the projects uncompleted at the time of the formal dedication on September 30, 1935; a crew of 500 men remained to finish it and other structures. To make the powerhouse roof bombproof, it was constructed of layers of concrete, rock, and steel with a total thickness of about 3.5 feet, topped with layers of sand and tar.^

Historical Notes

Every state in the USA furnished supplies and materials for the construction of the dam.

Historical Notes

There were 112 deaths associated with the construction of the dam. Included in that total was J. G. Tierney, a surveyor who drowned on December 20, 1922, while looking for an ideal spot for the dam. He is generally counted as the first man to die in the construction of Hoover Dam. His son, Patrick W. Tierney, was the last man to die working on the dam's construction, 13 years to the day later. Ninety-six of the deaths occurred during construction at the site of the 112 fatalities.^

(1934)#* - View of three men standing by a Packard observing the near completed process of concrete pouring at the dam.

Historical Notes

A total of 3,250,000 cubic yards of concrete was used in the dam before concrete pouring ceased on May 29, 1935. In addition, 1,110,000 cubic yards were used in the power plant and other works. More than 582 miles of cooling pipes were placed within the concrete. Overall, there is enough concrete in the dam to pave a two-lane highway from San Francisco to New York.^

(ca. 1935)* - View of the giant turbine runner before its installation at Hoover Dam power plant. The fin-like pieces of metal between the two circular flanges are the vanes.

Historical Notes

The powerplant consists of 17 main Francis turbine generators and two Pelton Waterwheel station service units (one for each plant wing). The total plant capacity is 2,079 MW.*#^

Historical Notes

The powerplant consists of 17 main Francis turbine generators and two Pelton Waterwheel station service units (one for each plant wing). The total plant capacity is 2,079 MW.*#^

(1935)**# - View of the graceful intake towers whose gates control the release of the reservoir water.

Historical Notes

When the newly formed Lake Mead had risen to the base of the intake towers, 260 feet above the river bed, the one remaining opening—the slide gates in the Nevada outer diversion tunnel plug—was closed to the Colorado. From that time on the river had to respond to rein. The broncho of the West was fully harnessed.**#

Historical Notes

Some 16,000 men worked on the construction of the dam--3,500 at any one time.^

Historical Notes

If the spillways were operated at full capacity, the water flow would be about the same as the flow over Niagara Falls (for each spillway).^^#

Historical Notes

During peak electricity periods, enough water runs through the generators to fill 15 average sized swimming pools (20,000 gallons each) in 1 second. #*

Historical Notes

Hoover Dam, one of the world’s outstanding engineering achievements, was selected by the American Society of Civil Engineers in 1955 as one of America’s seven modern civil engineering wonders. Majestic in its clean graceful lines, the dam stands with one shoulder against the Nevada wall and the other against the Arizona wall of Black Canyon, harnessing the Colorado River.^^#

Historical Notes

On September 30, 1935, less than 5 years after construction started, President Franklin D. Roosevelt said in dedication ceremonies at Hoover Dam: “This is an engineering victory of the first order – another great achievement of American resourcefulness, skill and determination. This is why I congratulate you who have created Boulder Dam and on behalf of the Nation say to you, ‘well done’.” ^##

In 1920, Ezra Scattergood pushed for a bill authorizing the construction of the Boulder Canyon Project (Hoover Dam). Despite attempts to discredit the project, Scattergood helped convince Congress in 1928 to pass the legislation and allow construction of the dam and a hydroelectric power plant.^#

Historical Notes

The City of Los Angeles would have to wait another 28 days (October 9th, 1936) before it would get its allotment of power from Hoover Dam.

Historical Notes

Sixteen high-voltage transmission lines connect Hoover Dam with its power market area.  Two lines terminate at Los Angeles, a line a distance of 266 miles.  A third line extends to Los Angeles via the McCullough Switching Station, where the energy is stepped up to 500,000 volts.  One line extends to San Bernardino, California.  Three lines extend to Las Vegas, Nevada.  One of the latter connects with the Davis Dam transmission system.  Other lines extend to Kingman, Arizona; Needles, California and nearby Boulder City.^^#

In total, there are 2700 miles of transmission line cable sending electricity from Hoover Dam to Los Angeles. #*

Click HERE to see more in Early Power Transmission.

Historical Notes

"On the site of the old Courthouse at Temple and Broadway, a platform had been erected. On the Courthouse grounds sat 10,000 persons in folding chairs.

The speakers had finished their speeches, the massed chorus had ended its song, and the prayer had been said, when the young woman–Miss Elizabeth Scattergood–stepped forward.

She read for a moment in a choked voice, a simple little speech full of feeling. Then she reached out her finger and touched a key. There was a tense moment of quiet.

A sputtering sound as the northeast corner of the Courthouse grounds. Brilliant as an explosion, lavender light washed away the half-darkness. In a great wave it swept across to the City Hall, to the Federal Building and to the Hall of Justice and Hall of Records…" - Los Angeles Times, October 10, 1936

Historical Notes

On October 9, 1936, the switch was thrown and electricity generated at the new Hoover Dam arrived in Los Angeles.   Los Angeles threw a big party.  The “Light on Parade” proceeded down Broadway, nicknamed “the Canyon of Lights.”

Historical Notes

"Astride the power of 115,000 horses, with burning plumes outspread, the Giant of Hoover Dam–Electricity–rode into Los Angeles last night, casting a heretofore unseen and magnificent glare on more than 1,000,000 persons who crowded the downtown district from end to end.

A tumult of yelling and whistling and screaming greeted the giant with an exuberance and spontaneous feeling that has not been observed since the demonstration the day the World War ended…." - Los Angeles Times, October 10, 1936

Construction of Hoover Dam - Historical Timeline

The following timeline takes us from the late 1890’s when the first attempt to control flooding from the Colorado River began to 1936 when the Hoover Dam was completed and electric power flowed to the City of Los Angeles:

1890’s – Initial attempt at diverting the Colorado River for irrigation purposes by the construction of the Alamo Canal by land speculator William Beatty.

1900 – Preliminary investigation and studies for building a dam at Black Canyon or Boulder Canyon with the purpose of controlling floods, providing irrigation water, and producing hydroelectric power.  Repeated flooding of the Imperial Valley and other areas created the need to control the Colorado River through construction of a dam.

1902 – Edison Electric Company surveys the Colorado River with the idea of building a 40-foot rock dam which could generate 10,000 horsepower.  At this time, however, the limit for transmission of electric power is only 88 miles and there are few customers within that limit.  During that same year Edison allows its land options on the river to lapse, including an option for what became the site of Hoover Dam.

1902 - U.S. Congress passes the Reclamation Act to provide for a plan for the payment of construction costs for a reclamation project to control the Colorado River.

1905 – Heavy rainfall and snowmelt causes the Colorado River to swell and overrun a set of Alamo Canal head-gates.  This results in a flood which diverts the entire volume of the Colorado River into the Salton Sink over a period of approximately two years before it can be controlled again.  This catastrophic event also floods the entire Imperial Valley.  The flood completely submerges the town of Salton, Southern Pacific Railroad siding, and Torres-Martinez Indian land.  The Salton Sea is created as a result of the diverted uncontrolled flow of the Colorado River over 50 miles into what was once an ancient dry lakebed in the desert for over two years without drainage.

1906-1907 – Southern Pacific Railroad spends $3 million to stabilize the waterway.

1922 – Reclamation Service (later the Bureau of Reclamation) presents a report calling for building a dam on the Colorado for flood control and power generation.  The report concludes that this should become a federal project since the river’s basin covers several states and the river enters Mexico.

1922- Reclamation Service selects Black Canyon as the ideal spot for the dam not the original location of Boulder Canyon since that site is bisected by a fault-line. The name of the project remains ‘Boulder Canyon Project’ despite the site change (See above photo).

1922 – The Colorado River Compact is signed by seven states of the Colorado basin (California, Nevada, Arizona, Utah, new Mexico, Colorado and Wyoming.  More than anything this serves to balance each of the affected state’s water rights.

1926 - William Mulholland gets involved with the Boulder Canyon Project even when funding wasn't clearly available. He makes a commitment to Congress to buy even more power than needed by Los Angeles. The extra power would be used to pump water in a newly planned aqueduct that would bring Colorado River water to Southern California (Colorado Aqueduct, completed 1941). Los Angeles guarantees its power purchases against the federal government's costs for the dam.

1928 – Congress authorizes the project and President Coolidge signs the bill.  $165 million is appropriated for the Hoover Dam, the Imperial Dam and the All-American Canal, both downstream. Legislation to authorize construction of the dam has taken years since representatives from other parts of the country found it to be too costly and beneficial to mostly California.  Not until the 1927 Mississippi flood did Midwestern and Southern congressmen and senators become more sympathetic to the dam project.

1929 – Six of the seven states approve the compact which is the minimum required to proceed with the project.  Arizona does not approve until 1944.

1931 – Start of Construction by a consortium of companies called Six Companies, Inc.

1933 - Ezra Scattergood obtains a $22,799,000 loan from the federal government to build a power transmission line from Hoover Dam to Los Angeles. Construction of the Boulder-LA transmission line begins as the dam itself is erected.

1934 - Congress authorizes a fifty-year contract that defines the how the Hoover Dam's electricity is to be allocated and sold, which would run from 1937 - 1987. The authorization also defines who is to operate the powerhouses within that time frame--both the Los Angeles Department of Water and Power and Southern California Edison. In 1984 the allocation of power would be revised (see 'Current Milestones' below). Also, in 1987 the Bureau of Reclamation assumes control of the powerhouses.

1935 (September 30) – Hoover Dam is dedicated by President Franklin Roosevelt.

1936 (March 1st) – The dam is turned over to the federal government from Six Companies, more than two years ahead of schedule.

1936 (October 9th) – Hoover Dam begins transmitting electricity to Los Angeles. The DWP built transmission line spans 266 miles of mountains and desert and delivers over 70% of Los Angeles’ power (Hoover Dam delivers less than 6% of LA's power today). The transmission lines included pioneering technology in high-voltage transmission. They transmitted electricity at a higher voltage (287 kV) than any other long-distance transmission line in the world to date.

During the years of lobbying leading up to the passage of legislation authorizing the dam in 1928, the press generally referred to the dam as "Boulder Dam" or as "Boulder Canyon Dam", even though the proposed site had shifted to Black Canyon. The Boulder Canyon Project Act of 1928 (BCPA) never mentions a proposed name or title for the dam. The BCPA merely allows the government to "construct, operate, and maintain a dam and incidental works in the main stream of the Colorado River at Black Canyon or Boulder Canyon".

When Secretary Wilbur spoke at the ceremony starting the building of the railway between Las Vegas and the dam site on September 17, 1930, he named the dam "Hoover Dam", citing a tradition of naming dams after Presidents, though none had been so honored during their terms of office. Wilbur justified his choice on the ground that Hoover was "the great engineer whose vision and persistence ... has done so much to make [the dam] possible".  One writer complained in response that "the Great Engineer had quickly drained, ditched, and dammed the country".

After Hoover's election defeat in 1932 and the accession of the Roosevelt administration, Secretary Ickes ordered on May 13, 1933 that the dam be referred to as "Boulder Dam". Ickes stated that Wilbur had been imprudent in naming the structure after a sitting president, that Congress had never ratified his choice, and that it had long been referred to as Boulder Dam.  When Ickes spoke at the dedication ceremony on September 30, 1935, he was determined, as he recorded in his diary, "to try to nail down for good and all the name Boulder Dam".  At one point in the speech, he spoke the words "Boulder Dam" five times within thirty seconds.  Further, he suggested that if the dam were to be named after any one person, it should be for California Senator Hiram Johnson, a lead sponsor of the authorizing legislation.  Roosevelt also referred to the dam as Boulder Dam, and the Republican-leaning Los Angeles Times, which at the time of Ickes' name change had run an editorial cartoon showing Ickes ineffectively chipping away at an enormous sign "HOOVER DAM", reran it showing Roosevelt reinforcing Ickes, but having no greater success.

More Recent Milestones

1984 - Congress passes a new statute which sets power allocations from the dam for the period 1987 to 2017.

1987 - The Bureau of Reclamation assumes control of running the powerhouses. Both DWP and SCE operated the powerhouses between 1936 and 1987.

2011 - President Obama signs legislation extending the power allocation contracts until 2067, after setting aside 5% of Hoover Dam's power for sale to Native American tribes, electric cooperatives, and other entities. The new arrangement is to take place in 2017.^

Please Support Our Cause

Water and Power Associates, Inc. is a non-profit, public service organization dedicated to preserving historical records and photos.  We are of the belief that this information should be made available to everyone—for free, without restriction, without limitation and without advertisements.

Your generosity allows us to continue to disseminate knowledge of the rich and diverse multicultural history of the greater Los Angeles area; to serve as a resource of historical information; and to assist in the preservation of the city's historic records.