Hoover Dam: 75th Anniversary History Symposium

In March 1928, the U.S. Congress was poised to approve the Boulder Canyon Project Act (BCPA) and authorize federal support for building what would become Hoover Dam. California Congressman Phil Swing and Senator Hiram Johnson had championed the BCPA since the early 1920s and now — despite continued opposition from private power interests and Arizona politicians — their politicking appeared ready to bear fruit. But minutes before midnight on March 12th the St. Francis Dam gave way, releasing a deadly torrent down the Santa Clara Valley in Southern California and killing more than 400 people. This paper examines the relationship of Los Angeles (and St. Francis Dam designer William Mulholland) to the BCPA, and considers how a key investigation of the disaster was tied to the proposed Hoover/Boulder Dam. While assessing the technology of concrete curved gravity dam design in the 1920s, it also considers how the disaster prompted authorization of a special Colorado River Board and delayed congressional passage of the BCPA until December 1928. It concludes with consideration of how the disaster spurred revision of California's dam safety regulations and professional concerns this initiative engendered among members of the ASCE.

In 1902, when Congress passed the Reclamation Act, damming the Colorado River was a dream of a young engineer in the U. S. Geological Survey, Arthur Powell Davis, and water visionaries in California. Reclamation staff overcame unprecedented technological, political, and economic challenges to pave the way for Hoover Dam. This paper reviews some of the key issues, the accomplishments of Reclamation prior to and during construction of Hoover Dam, and the political and economic innovations associated with the dam.

In 1930, the Bureau of Reclamation selected Saco Reink DeBoer as the city planner for the company town of Boulder City for the residences of workers on Hoover (Boulder) Dam. Over 1,500 buildings were constructed to house the 5,000 plus dam workers, making Boulder City the third largest city in Nevada. DeBoer gained experience with the Denver Parks and Parkway System and other towns throughout Colorado, New Mexico, and Wyoming. The Radburn, New Jersey superblocks around central park spaces were utilized in the Boulder City plan. In American city planning history, Boulder City was the first fully developed new town during the Community Planning Movement. Named after the dam general superintendent in 1981, the Frank T. Crowe Memorial Park was a large neighborhood park. The civic center of public buildings was the center of a triangular-shaped city plan with the Bureau of Reclamation administration building at the apex. The engineering basic support infrastructure of water, sewer, electricity and roadways was constructed. In 1931, the water for Boulder City came six miles from the Colorado River in a twelve-inch water main pumped up 2,000 feet in elevation. A pre-sedimentation basin, filtration system, water softening, and chlorination were needed. Four pumping stations and five water storage tanks were required. The town was administered by city manager, Sims Ely, who reported only to the Construction Engineer for the dam: Walker R. Young. The winning construction was by Six Companies Inc. Six Companies Inc. set up a separate subsidiary: the Boulder City Company to complete workers' lodging, boarding, recreation, transportation to and from the dam and other services. Six Companies Inc. agreed to finance the operation of the grade school and pay the twelve teachers' salaries with Congress paying $70,000 for the school building.

Based largely on research into the federal archival record, this paper, an abridged version of the original study, examines the efforts by Reclamation and the Army—who did not always agree—in protecting Hoover Dam, with major events of World War II woven into the narrative to provide global context. This interpretive structure will illustrate how defense priorities shifted as the war evolved, how the Army assigned higher priorities to the U.S. Army Corps of Engineers' hydropower dams than Reclamation's, and how the Army sent its worst soldiers to the desert to protect Hoover Dam. Also mentioned is the sole material remnant of this protection effort, a fortified machine gun bunker that sits above the dam. It not only serves as a symbol of the war effort, it is soon slated to become a historic interpretive site.

The Boulder Canyon Project Final Reports documented the greatest leap forward in concrete technology ever. This included the pioneering work in cement chemistry, mixture proportioning, compressive strength and elastic properties, permeability, and thermal properties of mass concrete. The scientific methodology followed by numerous civil engineers and researchers provided the foundation for future mass concrete investigations for the next half century.

Hoover Dam, at its original construction in 1931–1936, was constructed with over 3.25 million cubic yards of concrete in the dam alone. Most of the concrete for the dam was mass concrete made with up to 9-inch maximum size aggregate (MSA). The original 28-day compressive strength tests performed for quality assurance during construction were found to be in the 3,500 lb/in² range. In 1995, the Bureau of Reclamation's Materials Engineering and Research Laboratory completed a testing program to evaluate the long term properties of the Hoover Dam concrete. Compressive strengths at this time were found to average 7,230 lb/in². Discussions will include the core sample locations and compressive, tensile and shear strength test results from this study, along with a discussion of determining the need for the core testing program.

Hoover Dam was a monumental accomplishment for its era which set new standards for feasibility studies, structural analysis and behavior, quality control during construction, and post-construction performance evaluations. One of the most important departures was the congressional mandate placed upon the U.S. Bureau of Reclamation (Reclamation) to employ an independent Colorado River Board to perform a detailed review of the agency's design and issue recommendations that significantly affected the project's eventual form and placement. Of its own accord Reclamation also employed an independent board of consultants which convened twice yearly several years prior to and during construction of the project, between 1928 and 1935. Reclamation also appointed a special board of consultants on mass concrete issues, which had never been previously convened. Many additional landmark studies were undertaken which shaped the future of dam building. Some of these included: the employment of terrestrial photogrammetry to map the dam site and validate material quantities; insitu instrumentation of the dam's concrete; and consensus surveys of all previous high dams to compare their physical, geologic, and hydrologic features with those proposed at Hoover Dam. The project was also unique because the federal government provided of all materials, except the concrete aggregate, to minimize risk of construction claims and delays.

The size of the Boulder Canyon Project necessitated a broad array of innovations in construction engineering and management which had enormous impacts on all of the large scale projects that followed it. Foremost among these was the employment of a joint venture involving eight different firms, organized into six partners (Six Companies, Incorporated). Many of the techniques employed to construct of Hoover Dam were of a pioneering nature, designed to hasten the construction schedule and maximize profits. These were emulated and perfected by Six Companies and most of their competitors for several decades thereafter. Some of these included: multiple-level rail spurs; temporary trestles and suspension bridges of many sizes, employment of construction access adits to allow multiple headings of underground workings; fully automated concrete batch plants; staging of construction materials on the opposite river bank; government provision of all materials except the concrete aggregate (to minimize risk of construction claims and delays). Major achievements were also made in quality assurance and materials testing, despite the fact that the job proceeded round-the-clock.

The size of the Boulder Canyon Project necessitated a broad array of innovations in construction engineering and management which had enormous impacts on all of the large scale projects that followed it. Major milestones were achieved in mass concrete handling and placement across a large and sometimes treacherous job site; equally challenging problems with forming and pouring structural concrete elements for the project, such as the intake towers, penstocks, spillways, and outlet works; steel penstock fabrication and placement; and establishment of basic job site safety precautions that became increasingly common thereafter, including on-site medical care the provision of hard hats to all workers.

Hoover Dam was a monumental accomplishment for its era which set new standards for post-construction performance evaluations. Reclamation based many of their decisions on surveys of previous high dams to compare their physical, geologic, and hydrologic features with those proposed at Hoover Dam. Perhaps the greatest triumph was the hydroelectric power generation, which repaid the cost of the project with interest over a term of 50 years, which quickly became the economic model for similar high dam projects, world-wide. In the aftermath of the behemoth project, the project did suffer a number of unexpected failings, principally, the failure of the grout curtain to function as intended (requiring retrofitting between 1936 and 1948) and severe cavitation of the spillway elbows in 1941 and 1983 (requiring installation of air ducts in 1983–84). Along the way Hoover Dam was the first dam to be singled out as a terrorist target (by German agents) and provided electricity for the world's largest magnesium production facility from 1942 onward.

Hoover Dam was a monumental accomplishment for its era which set new standards for post-construction performance evaluations. Many landmark studies were undertaken as part of the Boulder Canyon project which shaped the future of dam building. Some of these included: comprehensive surveys of reservoir sedimentation, which continue to the present; the discovery of turbidity currents operating in Lake Mead; the nature of nutrient-rich sediment contained in these density currents; cooperative studies of crustal deflection beneath the weight of Lake Mead; and reservoir-triggered seismicity. These studies were of great import in evaluating the impacts of large dams and reservoirs, world-wide, and have led to a much better understanding of reservoir siltation than previously existed. Hoover Dam was also the first dam to be fitted with strong motion accelerometers and Lake Mead the first reservoir to have an array of seismographs to evaluate the impacts of reservoir triggered seismicity. Along the way, there has been considerable confusion about the name of the dam, which was changed in 1931, 1933, and 1947. Most of the project documents are filed or referred to by the several names employed by Reclamation between 1928–1947. The article concludes with a brief description of the Boulder Canyon Project Reports, which have been translated into many different languages and distributed world-wide. This is followed by a summary of the unprecedented influence Hoover Dam has exerted on dam and reservoir construction, not only in the United States, but also abroad.

Hydraulic investigations for the unprecedented size and scope of the proposed Hoover Dam (also called Boulder Dam) started in 1930 with a small core of Bureau of Reclamation engineers and technicians assigned to the hydraulic laboratory of the Colorado Agricultural Experiment Station in Fort Collins, Colorado. This paper will summarize the hydraulic investigations and their impact on the Hoover Dam design as well as some of the field challenges associated with the construction and operation of Hoover Dam. The salient results of the initial spillway and outlet works model studies conducted at various venues, model scales, and with several design options will be reviewed. More recent hydraulic studies will be presented of the penstock tie rods, intake tower cylinder gate performance, replacement of the internal differential needle valves, and repair and solution for cavitation damage in the elbow of the spillway tunnels. The initial and subsequent studies related to hydraulic design and performance at Hoover Dam have produced standards and criteria that have greatly added to the world-wide knowledge base for today's hydraulic structure design. The design, experimental investigations and construction of the Hoover Dam pushed the science of hydraulics to new frontiers.

The designs of the Hoover Dam Spillways were innovative and helped shape the design of future spillways. The hydraulic models studies for the Hoover Dam Spillways and the resulting design details will be discussed and related to present day designs. With the Hoover Dam Spillway designs as a starting point, present day concerns and vulnerabilities of spillway structures will be discussed. Case histories of spillway incidents and failures will be presented. Current approaches for evaluating spillways and identifying potential failure modes related to spillway structures will be discussed, with a focus on: spillway capacity/dam overtopping issues; spillway conveyance capacity; gate performance in non-flood situations; and, performance of spillway linings under high velocity flow.

The Hoover Dam Powerplant was designed and built in the 1930s, a time without computers, without modern earthquake engineering, and without established building codes. For the first time since the original design, the Bureau of Reclamation's Building Seismic Safety Program (Program) has conducted a structural seismic evaluation of the both the Nevada and Arizona Powerplant superstructures and the Central Portion superstructure. These structures consist of multi-story reinforced concrete and structural steel systems built integrally with the downstream face of the dam and canyon walls. This paper illustrates the Program's usage of ASCE 31 and the finite element modeling techniques employed during the Powerplant evaluation. The Bureau of Reclamation owns 67 powerplants and over 200 pumping plants that are located throughout the western United States. The Program is tasked with assessing the structural and nonstructural seismic risks in these plants and providing recommendations and/or considerations for mitigating identified risks to the decision-makers for the facilities.

Part of the success of the Hoover Dam project is directly attributable to the work of Francis Albert Trenholm (Frank) Crowe, the general superintendent of Six Companies, Incorporated. Frank Crowe led the effort to pioneer construction techniques to make the project succeed in the isolated area of the confluence of the mighty Colorado River. To make these construction decisions with the associated risk, Crowe maintained an even and skilled hand based on the 20 years of experience he had had with the Bureau of Reclamation. This paper will provide a biographical sketch of Frank Crowe through articles and information gathered about one of the famous alumni of the University of Maine. A 1905 graduate of the University of Maine, Francis Crowe began his career just before his formal graduation; Crowe's career led him to the development and construction of 19 dams. He maintained a tireless work ethic to build the best structure possible within the established budget and schedule. His style gave him the respect of all who worked with him and the reputation of a Master Builder. The paper will conclude with a discussion about the UMaine Francis Crowe Society that is established to recognize the unique heritage of engineers who graduate from the University of Maine and who are engaged in engineering in Maine. The legacy of Frank Crowe lives beyond his short time here on Earth.

Hoover Dam's sculptural program, worked out by Oskar J. W. F. Hansen, relates in three significant ways to the dam's engineering. First, Hansen engaged not only in producing fine and decorative art but in the small-scale engineering of innovative pieces of furniture, a fact that made him especially suitable as an artistic collaborator with a team of engineers. Second, the scale of Hansen's interventions at Hoover Dam required the engineering of his works of art themselves. The art-workers on the project realized that they were dealing with engineering problems when executing Hansen's designs, and Hansen himself reflected on the engineering problems he had to tackle as an artist. Third, Hansen's work on Hoover Dam is not merely decorative or commemorative but moreover points up the representational qualities of the structure as a work of engineering. Those qualities simultaneously formed an integral part of the dam's engineering and transcended its practical goals. By externalizing and thus revealing the subjective essence of what was, after all, merely a dense and opaque mass of purely objective shape, Hansen's sculptures made Hoover Dam more than just a feat of human ingenuity. They made it magical.

Construction of the Hoover Dam was the largest public project in the United States to date and ushered in an age of infrastructure megaprojects by federal agencies. Confronting technical, organizational, and physical risks, the Hoover Dam was delivered two years ahead of schedule and within the budgeted cost for construction. The technical challenges and successful results for this megaproject are well documented but the pre-construction planning and construction management innovations have received little attention. In retrospect, the Hoover Dam remains unique as it created the mold of structuring the relationship between government requirements and private-sector expertise to successfully deliver on megaproject objectives, cost, and schedule. Modern megaproject construction, pre-project planning, and construction management often do not follow the Hoover Dam best practices that incorporated ingenuity and creativity. The best practices and lessons learned during the planning and construction of the Hoover Dam can and should be applied to current and future federal megaprojects.

Mega projects and small projects may be managed well by using the processes derived in 1910 by world class dam builder, Frank T. Crowe, while working on a small project in Wyoming and subsequently used by him on several successful projects during the following years including Hoover Dam—a mega project requiring over 1,500,000 cubic yards of rock excavation and over 3,400,000 cubic yards of concrete constructed on the Colorado River in the early 1930s.

One of the mechanisms of progress in modern societies is their investment in physical assets, which can provide the goods, services and symbols a society needs. Hoover Dam was the largest construction of its kind and came about during the Great Depression in the U.S. It served not only as a means of flood control, irrigation and hydroelectric energy, but also as a Mecca for the jobless and hope for progress. The task of organizing all resources available to realize such aspirations might have seemed insurmountable, but the builders were able to achieve them. While the historical record is filled with information about the social, cultural and design achievements of masterpieces of the built environment, much less light has fallen on the innovation required of and summoned by constructors in creating masterpieces such as Hoover Dam. A closer look at the innovative contribution of constructors to major constructed works is appropriate and long overdue. This paper attempts to reveal a few of the milestones in construction innovation that were born in the process of building Hoover Dam. Examples such as scheduling and management strategies, materials and methods in concrete, and equipment such as the `drilling jumbo' are explored.

Hoover Dam is rightly regarded as one of the greatest civil engineering achievements in history. While Hoover Dam is mired in some controversy for safety and labor practices, built during the great depression, it must be regarded as not only a triumph of engineering, but also a triumph of the human spirit. Large concrete dam construction was in its infancy in the early twentieth century. Hoover Dam's successful construction and enduring ability to harness the Colorado River are the result of the convergence of extraordinary men, machines, and methods. In the decades preceding Hoover Dam's construction, tremendous advancements were realized in every discipline of engineering. In the realm of heavy civil construction, these collective engineering advancements provided the construction technology that made Hoover Dam possible. This paper highlights how the right men, the right, machines, and the right methods all came together in the spring of 1931 to build a structure of unprecedented scope and challenges.