The Black Canyon of the Colorado River is now home to two massive construction feats – Hoover Dam and the recently-constructed (and much needed) Mike O’Callaghan-Pat Tillman Memorial Bridge, also known as the Hoover Dam Bypass, which took five years to complete. This month, I will be writing about the construction of the dam, and next month I will be doing my article on the bridge. Originally, I thought I could do them both in one story, but there was so much amazing information out there about each of these projects, I decided to break them up into two separate articles.
The Reclamation Service presented a report in 1922 calling for the development of a dam on the Colorado River for flood control and electric power generation. Originally, Boulder Canyon was looked at for the project, but since the site was bisected by a geologic fault, that idea was scrapped. Two other sites were considered, but both of them proved to be too narrow for a spillway and construction camp at the bottom. Black Canyon was found to be an ideal location, so the plan moved forward (it continued to be called the “Boulder Canyon Project” despite the site change.
California Representative Phil Swing and Senator Hiram Johnson repeatedly introduced legislation to authorize the dam, but the project was considered hugely expensive and one that would mostly benefit California. Southern congressmen and senators became more sympathetic after a 1927 Mississippi flood caused the St. Francis Dam to fail on March 13, 1928 and caused a disastrous flood that killed hundreds of people. That dam was an arch-gravity dam, the same as was proposed for the one in Black Canyon. While the project was found feasible, the Colorado River Board warned that should the dam fail, every downstream community would be destroyed. Because of that fact, the proposed dam should be constructed on ultra-conservative lines to avoid such a possibility.
President Coolidge signed the bill authorizing the dam on December 21, 1928. Once six of the seven affected states approved the compact, it would go into effect – this happened on March 6, 1929. The Bureau of Reclamation was considering what kind of dam should be used even before Congress approved the Boulder Canyon Project. John L. Savage was the Bureau’s chief engineer who oversaw the design. The monolithic dam would present a convex face towards the water above the dam and it would be 660 feet wide at the base, narrowing to 45 feet wide on the top, leaving room for a road between Nevada and Arizona. Stretching 1,244 feet across the canyon, the total height of the massive structure would be 726 feet.
A company called “Six Companies” bid $48,890,955 and was within $24,000 of the confidential government estimate and $5 million less than the next lowest bid – needless to say, they got the job. Las Vegas lobbied hard to be the headquarters for the dam construction, but instead it was announced early in 1930 that a city would be built in the desert near the dam site to support the workers. This town became known as Boulder City, Nevada. In September 1930, a rail line joining Las Vegas and the dam site began. Once the railway was complete, the work on the dam finally started. Back then, Las Vegas was a small city of only about 5,000 people. As work began, thousands of unemployed people converged on southern Nevada to find work on the project. Six Companies hired large numbers of workers, and employment peaked at 5,251 workers in July of 1934.
The Colorado River needed to be diverted before the dam could be built. Four diversion tunnels were driven through the canyon walls – two on the Arizona side and two on the Nevada side. Their combined length was 16,000 feet (more than 3 miles). This was completed in early 1933. After that, approximately 1,500,000 cubic yards of accumulated erosion soils and other loose materials in the now-dry riverbed had to be removed until sound bedrock was reached. The side walls of the canyon had to be excavated to virgin rock, as weathered rock might provide pathways for water seepage. While suspended from ropes at the top of the canyon, the “high scalers” removed the loose rock with jackhammers and dynamite. The most common cause of death was falling objects. Some high scalers took cloth hats and dipped them in tar, allowing them to harden. These hats helped protect the workers and were called “hard boiled hats” (later, hard hats).
On June 6, 1933, the first concrete was poured eighteen months ahead of schedule. The Bureau of Reclamation engineers calculated that it would take 125 years for the concrete to cure if poured in a continuous pour. The dam was marked with rectangles and then concrete blocks, or columns, were poured – some as large as 50 feet square and 5 feet high. A series of one inch steel pipes were placed inside the columns through which first cool river water, then ice-cold water from a refrigeration plant, were pumped through the pipes, helping to cure the concrete quickly and in small sections. Each section was cured before the next section was poured. After the concrete was cured, all of the water pipes were filled with grout.
Huge steel buckets that were seven feet high and almost seven feet in diameter delivered the concrete. General Superintendent Frank Crowe received two patents for the design of these steel buckets. The buckets were filled at two massive concrete plants on the Nevada side, and then the concrete was delivered to the job site via special rail cars. Suspended from aerial cable-ways, these buckets were maneuvered to the proper column and then poured. There is a myth that men were caught in the pour and left in the concrete, but Six Companies would not have permitted a flaw caused by the presence of a human body. Each bucket only deepened the concrete in a form by about an inch, anyway.
Overall, there is enough concrete in the dam to build a two-lane highway from San Francisco to New York. In 1995, concrete cores were removed from the dam for testing and they showed that the concrete in Hoover Dam continues to gain strength. The concrete in the dam is durable and has a compressive strength that exceeds the range typically found in normal mass concrete. The concrete in Hoover Dam is not subject to Alkali-Silica Reaction. Nonreactive aggregate was used to build Hoover Dam, unlike the Parker Dam downstream, where Alkali-Silica Reaction has caused measurable deterioration over the years.
A formal dedication was arranged to coincide with a western tour being made by President Franklin D. Roosevelt. In front of 10,000 people, the President’s speech avoided mentioning the name of former President Hoover, who was not even invited to the ceremony. A three-cent stamp was issued by the United States Post Office Department for the new “Boulder Dam” – which was the official name between 1933 and 1947, at which time a bill was passed unanimously by both Houses of Congress to formally name the structure Hoover Dam.
Generally counted as the first worker to die in the construction of Hoover Dam, a surveyor named J.G. Tierney drowned on December 20, 1922 while looking for the ideal spot for the dam. Coincidentally, the last man to die on the project, 13 years later to the day of the first death, was Patrick W. Tierney – J.G. Tierney’s son. There were 112 official deaths associated with the construction of the dam. Not included in the official number were the workers who deaths were diagnosed as pneumonia. A total of 42 workers died from “pneumonia” (workers alleged that this diagnosis was a cover for death from carbon monoxide poisoning as thick plumes of vehicle exhaust gases constantly filled the diversion tunnels).
The initial plans for the facade of the dam, the power plant, the outlet tunnels and ornaments clashed with the modern look of an arch dam. The Bureau of Reclamation, more concerned with the dam’s functionality, adorned it with a Gothic-inspired balustrade and eagle statues. This initial design was criticized by many as being too plain and unremarkable for a project of such immense scale, so Los Angeles-based architect Gordon B. Kaufmann, then the supervising architect to the Bureau of Reclamation, was brought in to redesign the exteriors. Kaufmann greatly streamlined the design, and applied an elegant Art Deco style to the entire project. Denver artist Allen Tupper True was hired at Kaufmann’s request to design and decorate the walls and floors inside the new dam. Motifs of the Navajo and Pueblo tribes of the region were incorporated into True’s design. The terrazzo floor at the base of the monument is embedded with a “star map” intended to help future astronomers, if necessary, calculate the exact day of President Roosevelt’s dedication of the dam (the map graphically depicts the exact moment of the dedication).
Uncompleted at the time of the formal dedication on September 30, 1935 was the powerhouse. A 500-man crew remained to finish this and other various structures at the site. Lake Mead water levels were high enough in the latter half of 1936 to power up the first three Francis turbine-generators, all on the Nevada side. On more Nevada generator went on-line in March 1937, and then in August of that year the first Arizona generator fired up. Four more generators were operating by September 1939, making the dam’s power plant the largest hydroelectricity facility in the world. Today, 17 total generators provide electricity to various cities, states and municipalities, with the most going to the Metropolitan Water District of Southern California (28.5%). After that, it goes to the states of Nevada (23%) and Arizona (19%), then the city of Los Angeles (15.5%), the Southern California Edison Company (5.5%) and then various cities, most in Southern California.
In 1937 Hoover Dam was open for tours after its completion. It was closed to the public on December 7, 1941 at which time only authorized traffic in convoys was permitted. The dam reopened on September 2, 1945 after WWII. By 1953, attendance was at 448,081. After opening a new visitor’s center in 1995, attendance exceeded one million for the first time. After the September 11, 2001 terrorist attacks the dam was again closed temporarily to the public and the road was closed to commercial vehicles permanently (the planning and design of an adequate bypass road/bridge began at this time). Due to increased security concerns by the government, much of the interior structure is now inaccessible to tourists. My editor was lucky enough to take his family down one of the elevators and into the powerhouse in 2004 and capture the amazing picture of the generators with the American flag draped overhead.
It is amazing to think that this construction project was completed in just five years for the paltry sum of $48 million – and, it was finished ahead of schedule. The final result is the ultimate testimony to American ingenuity, perseverance and hard work – a beautiful and functional structure that generates power, controls floods, and created the largest reservoir (and one of the prettiest) in the United States. Lake Mead has a total capacity of 28,537,000 acre-feet of water, is 590 feet at its deepest point, 112 miles long, and has a surface area of 247 square miles! If you have never been to this amazing site, I highly recommend that you visit Hoover Dam and take a tour inside – while you still can!!