Hoover Dam Research Articles

Temporal Patterns of Fish Occurrence in the Colorado River, Grand Canyon in Response to Temperature, Largescale Drought, and Newly Exposed Habitat

ABSTRACTTwo large dams on the Colorado River, Glen Canyon and Hoover Dam, have profoundly altered the river within Grand Canyon. Owing to widespread drought and increased water usage throughout the Southwest, water levels in Lake Mead declined by over 40 m since 2000, exposing over 80 km of newly emerged riverine habitat in the western Grand Canyon that experiences higher water temperatures and increased turbidity relative to upstream portions of the Colorado River within the Grand Canyon. Our objective was to investigate how the probability of fish occurrence has changed within the Colorado River in Grand Canyon as abiotic conditions have shifted in relation to these altered environmental conditions. We used 22 years of long‐term fish monitoring data, from 2000 to 2022, on the mainstem of the Colorado River in the Grand Canyon to map the probability of occurrence based upon modeled water temperature for native and common nonnative salmonid species through space (river kilometer) and time in relation to declining water levels in Lake Mead. Our results suggest that native fish occurrence is strongly correlated with longitudinally increasing water temperature, while nonnative trout species were negatively correlated with increased water temperature downstream from the dam. Further, we found that nonnative trout species have experienced decreases in their probability of occurrence through time, while natives have experienced an increase in probability of occurrence. Information on distribution of fish prior to reservoir declines, and how the fish assemblage has shifted coincident with environmental changes, can help inform future management of native and nonnative fish in highly regulated river systems.

Hydropower capacity factors trending down in the United States

The United States hydropower fleet has faced increasing environmental and regulatory pressures over the last half century, potentially constraining total generation. Here we show that annual capacity factor has declined at four fifths of United States hydropower plants since 1980, with two thirds of decreasing trends significant at p < 0.05. Results are based on an analysis of annual energy generation totals and nameplate capacities for 610 plants (>5 megawatt), representing 87% of total conventional hydropower capacity in the United States. On aggregate, changes in capacity factor imply a fleetwide, cumulative generation decrease of 23% since 1980 before factoring in capacity upgrades—akin to retiring a Hoover Dam once every two to three years. Changes in water availability explain energy decline in only 21% of plants, highlighting the importance of non-climatic drivers of generation, including deterioration of plant equipment as well as changes to dam operations in support of nonpower objectives.

Dynamic Flow Alteration Index for Complex River Networks With Cascading Reservoir Systems

AbstractLarge dams degrade the river’s health by heavily regulating the natural flows. Despite a long history of research on flow regulation due to dams, most studies focused only on the impact of a single dam and ignored the combined impact of flow regulation on a river network. We propose a new Dynamic Flow Alteration Index (DFAI) to quantify the local and cumulative degree of regulation by comparing the observed controlled flows with the naturalized flows based on a moving time horizon for the highly regulated Colorado River Basin. The proposed DFAI matches closely to dam’s localized regulation for headwater gages and starts to diverge as we move downstream due to increase in cumulative impact of the dams. DFAI considers the impact of dam operations on flow characteristics such as shifting of peak flow occurrence and dampening of peak flows. DFAI estimates the degree of regulation to be small for upstream dams and finds the maximum network regulation to be 2.52 years at Glen Canyon reservoir. DFAI also successfully captures the reduction in cumulative regulation when dam operations (e.g., Hoover Dam) bring the altered flow in synchronization with natural regime due to downstream flow requirements. The impact of San Juan River Basin Recovery Implementation Program is also captured by DFAI as the reduction in network regulation drops by 1.5 years for Navajo Dam. Our findings using DFAI suggest the need to develop naturalized flows for major river basins to quantify the flow alteration under continually changing climate and human influences.

Multi-Sensor InSAR Assessment of Ground Deformations around Lake Mead and Its Relation to Water Level Changes

Changes in subsurface water resources might alter the surrounding ground by generating subsidence or uplift, depending on geological and hydrogeological site characteristics. Improved understanding of the relationships between surface water storage and ground deformation is important for design and maintenance of hydraulic facilities and ground stability. Here, we construct one of the longest series of Interferometric Synthetic Aperture Radar (InSAR) to date, over twenty-five years, to study the relationships between water level changes and ground surface deformation in the surroundings of Lake Mead, United States, and at the site of the Hoover Dam. We use the Small Baseline Subset (SBAS) and Permanent scatterer interferometry (PSI) techniques over 177 SAR data, encompassing different SAR sensors including ERS1/2, Envisat, ALOS (PALSAR), and Sentinel-1(S1). We perform a cross-sensor examination of the relationship between water level changes and ground displacement. We found a negative relationship between water level change and ground deformation around the reservoir that was consistent across all sensors. The negative relationship was evident from the long-term changes in water level and deformation occurring from 1995 to 2014, and also from the intra-annual oscillations of the later period, 2014 to 2019, both around the reservoir and at the dam. These results suggest an elastic response of the ground surface to changes in water storage in the reservoir, both at the dam site and around the reservoir. Our study illustrates how InSAR-derived ground deformations can be consistent in time across sensors, showing the potential of detecting longer time-series of ground deformation.

Time and the Hydroelectric Dam

Abstract The hydroelectric dam is an interface in which contrasting temporalities converge and undergo transformation. Its massive wall sits at the center of operations where age-old ecosystems clash with rapid modernization, white water turns into a placid lake, and dynamos convert the lake’s gravitational pull into high-voltage electrical current. The hydroelectric dam exploits and exacerbates differences among the temporalities distinguishing these operations to generate power. In doing so, it has rendered the variance of time more perceptible. To support this claim I focus on the iconic Hoover Dam and on the works of Oskar J. W. Hansen, Joan Didion, Allen Tupper True, Francis Ponge and Fabrice Gobert. The main themes I examine in their works pertain to the notion of temporal interface and to the conceptions of deep, nested and haunted time.

Allen Tupper True and the Politics of Aesthetic Harmony

In his role as consulting artist at the Hoover Dam, Allen Tupper True aimed to harmonize the monumental structure with its desert environment. To do so, he employed colors and patterns that he claimed to have abstracted from the traditions of local Native American tribes who had been displaced by dam construction. This essay uses True’s correspondence and design concept documentation, much of which is in the collection of the Archives of American Art, to analyze the entirety of his proposed decorative scheme for the dam and explore the ecological, aesthetic, and political implications of the project.

Challenges of civil engineering megaprojects in North America

In many respects, megaprojects define the civil engineering profession, going back to the Panama Canal and the Hoover dam. They present many challenges. By definition, they are large, innovative projects that have never been done before. The Boston Central Artery/Tunnel and the San Francisco–Oakland Bay Bridge are now in service and by all accounts are performing well. However, these both had large cost overruns and concerns about quality and lengthy construction delays. The Central Artery/Tunnel also suffered a fatal ceiling collapse. Megaprojects require careful management. Owners and builders must be transparent and responsive to open record requests. Public employees should be empowered to bring forward concerns about quality and safety issues. The agencies should establish reliable open channels of communication with the public. Cost estimates should consider risk and provide for both best and worst cases. Independent inspection agencies should be established to provide oversight of large projects.

Integrating Landsat Imageries and Digital Elevation Models to Infer Water Level Change in Hoover Dam

The Thematic Mapper onboard Landsat 4, 5, and Enhanced Thematic Mapper Plus ( $\text{TM/ETM}+$ ) onboard Landsat 7 have frequency bands (green and SWIR) to effectively measure water body extents and their changes via the Modified Normalized Difference Water Index (MNDWI). Here, we developed a technique, called the thematic imagery-altimetry system (TIAS), to infer the vertical water changes from MNDWI horizontal water extent changes by integrating long-term $\text{TM/ETM}+$ imageries with available digital elevation models (DEMs). The result is a technique to quantify water level changes of natural or artificial water bodies over two decades. Several DEMs were used to compute intersects with $\text{TM/ETM}+$ water extent time series to evaluate the robustness of the technique. These DEMs include: the Advanced Spaceborne Thermal Emission and Reflection Radiometer Global Digital Elevation Map version 2 (ASTER-GDEM2, at 1 arcsec resolution), the Shuttle Radar Topography Mission version 2 (SRTM C-band at 1 arcsec), and the Global Multiresolution Terrain Elevation Data (GMTED2010 at 7.5 arcsec). We demonstrated our technique near Hoover Dam (HD) in Lake Mead to quantify its respective decadal water level changes. The dammed water had experienced extraordinary level variation in the past 20 years due to natural decline from intake or artificial impoundments. The discrepancy of the HD water level changes from an analysis of 32-year (1984–2015) time series, including 584 Landsat scenes, using the GMTED2010 DEM, has a RMSE reached $0.85 \pm 0.63\; \text{m}$ (91% of data) as compared with in situ stage record.

Life after death: evidence of the Hoover Dam as a hero project that defends against mortality reminders

Dams have historically been constructed as a supply management strategy to control water despite increasingly recognized sociocultural, environmental and financial costs. Current water management strategies continue to depend on technology-based solutions despite these costs. We used a transdisciplinary approach to link water history and social psychology to examine the underlying influences on water decisions such as the construction of large-scale water infrastructure. Specifically, we used indicators from terror management theory—a social psychology framework to understand how humans’ efforts to repress their death awareness influences motivation and behaviour. We focus on symbolic immortality as a powerful way by which people overcome their death fears in a highly individualistic Western and secular society. In this research three interrelated questions. First, was there evidence of mortality salience indicators in discussions of the Hoover Dam? Using the Hoover Dam as a historic case, we identified mortality salience evidence in the public statements during the dam’s pre-construction, construction, and post-construction phases. We found abundant mortality salience in the public statements about the Hoover Dam during all phases. Second, could the Hoover Dam be classified as a legacy project or “hero project” as defined by Ernest Becker and subsequent research through terror management theory? The evidence suggested that the Hoover Dam—as a representative example of the large scale, water infrastructure that dominates our contemporary supply-management regime—might have served as a hero project for those involved in its installation. And third, could the Hoover Dam, and possibly other large dams, be a means to overcompensate for mortality-fears for those involved in their installations, contributing to an environmentally unsustainable but historical water management legacy? Characterising the Hoover dam as not only a water supply infrastructure project but also as a hero project intended to alleviate mortality-fears, offers complementary explanations as to why unsustainable water management decisions were made in the American West.

Visualization of Lake Mead Surface Area Changes from 1972 to 2009

For most of the last decade, the south-western portion of the United States has experienced a severe and enduring drought. This has caused serious concerns about water supply and management in the region. In this research, 30 orthorectified Landsat satellite images from the United States Geological Service (USGS) Earth Explorer archive were analyzed for the 1972 to 2009 period. The images encompassed Lake Mead (a major reservoir in this region) and were examined for changes in water surface area. Decadal lake area minimums/maximums were achieved in 1972/1979, 1981/1988, 1991/1998, and 2009/2000. The minimum lake area extent occurred in 2009 (356.4 km2), while the maximum occurred in 1998 (590.6 km2). Variable trends in water level and lake area were observed throughout the analysis period, however progressively lower values were observed since 2000. The Landsat derived lake areas show a very strong relationship with actual measured water levels at the Hoover Dam. Yearly water level variations at the dam vary minimally from the satellite derived estimates. A complete (yearly) record of satellite images may have helped to reduce the slight deviations in the time series.

The Gender of Water and the Pleasure of Alienation: A Critical Analysis of Visiting Hoover Dam

Hoover Dam, located on the Arizona-Nevada border and damming the Colorado River, is a well-known and often-visited place. The meanings people assign to such a structure articulate key environmental, economic and technological ideologies. An exploration of those meanings is important for understanding the forces that shape public perception and environmental policy. Specifically, this essay examines the official rhetoric of Hoover Dam from an ecofeminist perspective. Through a critical reading of the educational displays, films, plaques and other texts as well as the physical structure of the dam itself, three rhetorical strategies used in the dam's official presentation are identified. First, the Bureau of Reclamation presents the Colorado River as a chaotic, feminine entity in need of masculine control. Second, the river's rhetorical status as an Other encourages audiences to identify with the subject position of nature's master and thereby participate in the pleasures such an identity offers. Third, the Bureau uses the prevalent “common sense” of Native Americans as environmentally sensitive in combination with an “historical” Native American voice to establish the dam as both environmentally sound and a logical step in humanity's progress toward economic development and dominion over nature.

Review: HOOVER DAM: The Photographs of Ben Glaha, by Barbara Vilander

Review: <i>HOOVER DAM: The Photographs of Ben Glaha</i>, by Barbara Vilander

Building Hoover Dam: An Oral History of the Great Depression by Andrew J. Dunar and Dennis McBride

422 Book Reviews TECHNOLOGY AND CULTURE BuildingHooverDam: An Oral History ofthe Great Depression. By Andrew J. Dunar and Dennis McBride. New York: Twayne (Macmillan), 1993. Pp. xix + 350; illustrations, notes, appendixes, index. $26.95 (cloth); $13.95 (paper). On September 30, 1935, President Franklin D. Roosevelt looked out over the 20,000 people witnessing the dedication of Hoover Dam and remarked that they were there to pay tribute to: the genius of the dam’s designers; the energy, resourcefulness, and zeal of the builders, who finished the work two years ahead of the contract re­ quirements; “but, especially, we express our gratitude to the thou­ sands of workers who gave brain and brawn to this great work of construction” (p. 311). Building HooverDam is the story of the workers who toiled, as Roosevelt said, “in the bottom of a gloomy canyon, whose precipitous walls rose to a height of more than a thousand feet, [where below] flowed a turbulent, dangerous river . . . protected by neither trees nor grass from the blazing heat of the sun ... a cactus covered waste” (p. 311). They came for jobs in the middle of the worst economic depression ever to hit America, many of them unskilled; they left as electricians, masonry finishers, carpenters, me­ chanics, and other tradesmen. They dared to build the largest dam ever built at that time, many because they weighed the danger of the work against the three square meals and clean sheets provided by the contractor, the Six Companies. The meals and housing typically won. Andrew Dunar and Dennis McBride have given us a wonderful story of the building “of the greatest dam in the world,” as told by the workers who made it. Their memories of the heat, wind, blowing sand, and general misery at the bottom of Black Canyon, where fami­ lies lived in tents with babies and young children, pleased, despite it all, to have the $4 per day, evoke the primitive conditions where hope and community grew. They tell us the technologies of dam building and power-generation construction in simple terms, but in words powerful enough to force a visual image of men hanging from ropes hundreds of feet from the floor of a canyon, placing frames for con­ crete pours. We learn of power penstocks formed on the site from sheets of steel because it was impossible to form them elsewhere and move to where they needed to be; of cooling the concrete through water tubing placed inside the frames to keep the surface tempera­ ture constant despite the tremendous heat during the summer months; of blasting tunnels through solid rock. It is a story worth reading for the details of the dam building alone. But the greatest value ofBuilding Hoover Dam is in the social aspects of the work. The friction between the blue-collar workers and the white-collar workers underlies the descriptions of the brick homes built for the government employees and their grass lawns, and the quickly built frame rooms, with no landscaping, thrown up for the Six Companies’ workers. The stories of town building at Boulder City, a government reservation which forbade liquor or transients, TECHNOLOGY AND CULTURE Book Reviews 423 evoke the sense of family fostered in many who lived there and who had not experienced the feeling before or since the dam building. The juxtaposition of a worker’s description of running the number eleven cableway across the top of the dam site, feet hooked into a rope and hanging hundreds of feet above the canyon floor, with his memory of going home, dead tired, to a house where the wind blew so hard the sand came in through the cracks and covered his face by the time he awoke, tells us perfectly what it was like to be part of the construction of the world’s greatest dam. Those interested in the technology of dam building will find Build­ ing Hoover Dam one of the best books on the subject; those interested in the culture of constructing large, ambitious projects will find this work equally satisfying. Karen L. Smith Dr. Smith is manager of Water Resources Management of the Salt River Project, Phoenix, Arizona, and the author...

Machine-Age Ideology: Social Engineering and American Liberalism, 1911–1939 by John M. Jordan

TECHNOLOGY AND CULTURE Book Reviews 423 evoke the sense of family fostered in many who lived there and who had not experienced the feeling before or since the dam building. The juxtaposition of a worker’s description of running the number eleven cableway across the top of the dam site, feet hooked into a rope and hanging hundreds of feet above the canyon floor, with his memory of going home, dead tired, to a house where the wind blew so hard the sand came in through the cracks and covered his face by the time he awoke, tells us perfectly what it was like to be part of the construction of the world’s greatest dam. Those interested in the technology of dam building will find Build­ ing Hoover Dam one of the best books on the subject; those interested in the culture of constructing large, ambitious projects will find this work equally satisfying. Karen L. Smith Dr. Smith is manager of Water Resources Management of the Salt River Project, Phoenix, Arizona, and the author of The Magnificent Experiment: Building the Salt River Reclamation Project, 1890—1917 (Tucson, Ariz., 1986). Machine-Age Ideology: Social Engineering and American Liberalism, 1911— 1939. By John M. Jordan. Chapel Hill: University of North Caro­ lina Press, 1994. Pp. xv + 332; illustrations, notes, index. $39.95. John M. Jordan has taken as his theme the ideas of the “rational reformers” of the early 20th century who, contemplating the wealth of goods produced by industrial technology and shocked at the in­ equity and social conflict that persisted amid abundance, sought rem­ edies in the methods of science and engineering: the discovery of “facts” and “laws” that could solve not only problems of machine production but of human society as well. On some aspects of this movement a good deal has been written, but, relying on the papers of a number of exponents and on a wide range of secondary litera­ ture, Jordan has tried to pull together various sources into a compre­ hensive account of an intellectual current that flourished in certain circles in the 1920s, inspired much talk and some action in the New Deal, and fizzled out in the late 1930s. Adopting a personal approach, he analyzes the statements and theories of prominent engineers, writ­ ers, and scholars. After a discussion of prewar figures, especially Thorstein Ve­ blen—a major influence—Jordan describes the enthusiasm of many reformers for the wartime state-directed effort toward victory. (In reality, remarks the author, they believed in “the myth of a coherent system that never existed . . . the American technocratic dream was an illusion” [p. 103].) In the 1920s, “a curiously apolitical reform spirit” (p. 100) permeated public discussion as theorists of “social control” and “social engineering” gained self-confidence and prestige. Among such disparate personalities as Herbert Hoover, John Dewey, 424 Book Reviews TECHNOLOGY AND CULTURE Rexford Guy Tugwell, William F. Ogburn, Wesley Clair Mitchell, Charles Merriam, and Mary Van Kleeck, Jordan traces a common thread of scientism and, with some exceptions, a tendency to elitism. Of particular interest are accounts of the role of foundations, espe­ cially the Laura Spelman Rockefeller Memorial, which funded The Encyclopaedia of Social Science and Recent Social Trends, and of differ­ ences among reformers on the social responsibilities of “science.” As Jordan observes (with Harold Laski), foundation aid tended to con­ fine investigations within the established order. After 1930, Jordan points out, the “social engineering model . . . enjoyed growing support” (p. 207). Among writers outside the New Deal, he considers carefully Charles Beard and John Dewey; the lat­ ter, though devoted to democracy, “provided logical justification to less democratic writers with whom he disagreed” (p. 231). Jordan’s treatment of the New Deal itself, however, is superficial and oddly selective. The National Recovery Administration, which, though hardly a “plan,” in its failure discredited the concept of planning, deserves more attention, and Tugwell’s Resettlement Administration receives only passing notice. While picking out absurdities in Arthur E. Morgan’s “Ethical Code,” Jordan devotes little space to the visions of Morgan, Morris L. Cooke, and others of a countryside transformed by networks of electric power and provides no appraisal of the results of their...

Review: HOOVER DAM: AN AMERICAN ADVENTURE, by Joseph E. Stevens

Review: <i>HOOVER DAM: AN AMERICAN ADVENTURE</i>, by Joseph E. Stevens

Hoover Dam: An American Adventure

In the spring of 1931, in a rugged desert canyon on the Arizona-Nevada border, an army of workmen began one of the most difficult and daring building projects ever undertaken - the construction of Hoover Dam. Through the worst years of the Great Depression as many as five thousand laborers toiled twenty-four hours a day, seven days a week, to erect the huge structure that would harness the Colorado River and transform the American West.Construction of the giant dam was a triumph of human ingenuity, yet the full story of this monumental endeavor has never been told. Now, in an engrossing, fast-paced narrative, Joseph E. Stevens recounts the gripping saga of Hoover Dam. Drawing on a wealth of material, including manuscript collections, government documents, contemporary newspaper and magazine accounts, and personal interviews and correspondence with men and women who were involved with the construction, he brings the Hoover Dam adventure to life. Described here in dramatic detail are the deadly hazards the work crews faced as they hacked and blasted the dam's foundation out of solid rock; the bitter political battles and violent labor unrest that threatened to shut the job down; the deprivation and grinding hardship endured by the workers' families; the dam builders' gambling, drinking, and whoring sprees in nearby Las Vegas; and the stirring triumphs and searing moments of terror as the massive concrete wedge rose inexorably from the canyon floor. Here, too, is an unforgettable cast of characters: Henry Kaiser, Warren Bechtel, and Harry Morrison, the ambitious, headstrong construction executives who gambled fortune and fame on the Hoover Dam contract; Frank Crowe, the brilliant, obsessed field engineer who relentlessly drove the work force to finish the dam two and a half years ahead of schedule; Sims Ely, the irascible, teetotaling eccentric who ruled Boulder City, the straightlaced company town created for the dam workers by the federal government; and many more men and women whose courage and sacrifice, greed and frailty, made the dam's construction a great human, as well as technological, adventure. Hoover Dam is a compelling, irresistible account of an extraordinary American epic.

Great American Bridges and Dams by Donald C. Jackson

TECHNOLOGY AND CULTURE Book Reviews 1061 ness of these proposals only points out the care taken with the heart of this book, an adroit exposition of modern tunneling technology. Gregory K. Dreicer Mr. Dreicer is an architectural conservator who specializes in high-rise buildings and a doctoral student in the history of technology at Cornell University. Great American Bridges and Dams. By Donald C. Jackson. Washington, D.C.: Preservation Press, 1988. Pp. 357; illustrations, bibliography, index. $16.95+ $3.00 handling (paper). “There are the greatest lot of bridges here you ever saw,” a visitor to Cleveland scrawled on a postcard in 1905. That message, reflecting an instinctive affection and respect for technological achievement, came to mind while reading Donald C. Jackson’s Great American Bridges and Dams. With similar feeling, Jackson has assembled a catalog of the best bridges and dams American technology has to offer. Why bridges and dams? Jackson explains that they are bound by a common heritage, that both are among the most visible manifestations of civil engineer­ ing in our environment. The 330 sites included were chosen both for their accessibility and for their variety. Most are at least fifty years old. Here are the great bridges and dams—San Francisco’s Golden Gate and St. Louis’s Eads bridges, Washington State’s Grand Coulee and Nevada’s Hoover dams. Here, too, are more modest structures that survive as representative examples of once-common technologies; so many of these have been replaced that the survivors necessarily take on increased significance. The book is organized into six geographic regions. Within each region, states, cities, and sites are presented alphabetically. Each entry includes key data: site name, natural feature spanned, locations, engineer or builder, and date completed. There is a brief summary of each site’s history and cultural significance. Throughout the book, technology is addressed in even, easy doses that inform but do not intimidate. The site listings are preceded by sections treating bridge and dam types and preservation issues. Stone, arch, wooden, metal truss, cantilever, movable, metal arch, suspension, reinforced concrete, and girder bridges are all explained, as are arch, buttress, and gravity dams. These descriptions generally are adequate, although a few will leave readers baffled, especially newcomers to these subjects. Movable bridges, for example, are not explained with the same thoroughness as are truss types. A sentence like this one—“Depending on the number of hinges built into the design, arch bridges can be . . . characterized as fixed, single-hinged, two-hinged or three-hinged” 1062 Book Reviews TECHNOLOGY AND CULTURE (p. 33)—requires further elaboration to be meaningful. In the section on dams, an explanation and diagram of a turbine (since so many dams are used for power production) would have been helpful. But these are quibbles about a book that, overall, is carefully researched and written. The preservation of bridges and dams presents unique challenges, for their continued survival depends not so much on significance as on safety. While there are success stories—the state of Virginia, for example, early on completed an inventory of its historic metal truss bridges that provided a context for preserving the best examples—the book’s case studies demonstrate just how complex bridge and dam preservation can be. Fortunately, public interest in the preservation of historic bridges, at least, seems to be growing; Jackson acknowledges that dams are such prosaic structures they have yet to attract the attention of preservationists. The book’s physical dimensions—it is tall and skinny—are oddly out of sync with the expansiveness of its subjects. Apparently, the confining format was dictated by the requirements of the National Trust’s Great American Places Series, of which this guide is a part. It necessarily limits the effectiveness of the many stunning black-andwhite photographs. Nevertheless, while one might wish the book could be larger, one cannot wish for a better introduction to the astonishing range of American technology still to be seen along our roads and rivers. Carol. Poh Miller Ms. Miller is a historical consultant in Cleveland. She has documented many of that city’s bridges for the Historic American Engineering Record of the National Park Service. Hoover Dam: An American Adventure...

Finite element analysis—design aid for a proposed shaft at hoover dam

A case study is presented on the use of the finite element analysis program, ADINA, as an aid in the design of an elevator shaft to be located in the dose proximity to an existing penstock tunnel. The excavation for the shaft may create over-stressing or excessive displacements of the existing tunnel lining which would be undesirable. ADINA was used to find stress and displacement vectors. Difficulties of analyzing a large sized ‘ADINA’ model to find those vectors were resolved by using PATRAN software and mixing of the linear and nonlinear elements.

Pioneer Conservationists of Western America by Peter Wild

Pioneer Conservationists of Western America by Peter Wild

Surficial sediment in Lake Mead [Arizona-Nevada

The surficial sediment along a 70-mile reach in Lake Mead was examined as to texture and mineralogical composition in order to determine possible relations to diagenesis and deposition. Samples were taken at six locations from Grand Wash at the upstream end of the lake to the Intake Towers at Hoover Dam. Differences in texture and clay composition were noted between samples upstream and downstream from Virgin Basin. The median diameter of laboratory-deflocculated sediment samples are between 4.2 and 4.6 microns on the downstream side of Virgin Basin and less than 2 microns upstream. Mineralogically, montmorin-type clays dominate the dispersed clay fraction upstream whereas illite is predominant downstream. The quantity of water in Lake Mead represents a calcareous, flocculating environment for responsive clays and it is proposed that particle-size distribution in the native environment is different from the dispersed state, probably due to montmorin-bound flocs existing in the silt-size range in the lake water. An alternative hypothesis for the differential distribution of texture and composition is the possible drag exerted on the surface of sediment near the dam by the outflow of water through the gates, resulting in winnowing of the fines from the surficial material.