Hoover Dam - a wonder of surveying
The dizzying pace of technological change is overwhelming at times. But no matter what changes, surveyors keep us grounded, because they know precisely where we stand, X, Y and Z. Surveyors have been setting the markers for progress since ancient times – the early Egyptian and Roman architectural wonders were based on the work of early surveyors. Colonial surveyors were key to the founding of the United States, not only by parsing out boundary lines for European settlers, but by nation-building – helping to author the Declaration of Independence, then helping to create a new kind of government for the new nation.
The art of surveying creates new technology and adapts existing technology to produce more precise information about the physical world. Surveying is an integral part of any type of work that is rooted in the earth. It’s interesting to explore surveying projects of the past that we now take for granted but literally made life as we know it possible. One such project involved seven states, more than 20 years of planning and cost more than 112 lives.
Highsmith, Carol M, photographer. Above Hoover Dam near Boulder City, Nevada. United States Hoover Dam Nevada. [Between 1980 and 2006]
Hoover Dam
The Hoover Dam has been an engineering wonder and tourist draw since it was completed in 1936. It wasn’t built for beauty and an awe-factor – it was built for its reservoir, Lake Mead, which supplies water to more than 20 million people in California, Arizona and Nevada, and for the hydro-electric power that lights the Las Vegas strip and provides electricity to 1.3 million people.
Since the 1850s, the idea to use the waters of the Colorado River to irrigate the Imperial Valley in California was proposed to resolve the continual water crisis in that area. It would take a lot of trial and error before a dam was built that resolved the cyclical flooding of the Colorado River while providing the water the valley needed.
Early Exploration
Back then, the Colorado River hadn’t even been fully explored. However, in 1857, the War Department sent Lt. J.C. Ives up the Colorado River from the Gulf of California to survey the river and determine its navigability because of war. The Federal government needed a route for the transportation of troops and supplies to Utah, where the Utah War was intensifying. The 27-man Ives expedition lasted for more than a year and included famous cartographer Baron von Egloffstein.
Lake Mead area marked out on a map by Baron von Englestein, 1858.
Ives succeeded in taking his steamboat almost 400 miles upstream to the lower end of Black Canyon by 1858. At that point, the boat struck a submerged rock and was destroyed. Ives continued upstream in a skiff until he reached Las Vegas Wash, about five miles upstream from the future site of Hoover Dam.
After completing this assignment, Ives’ military career switched focus from exploration to using his surveying and engineering skills to help build the Washington Monument with the Army Corps of Engineers.
The land around the Colorado River was so rugged that it wasn’t until twelve years later that another surveyor, Major John Wesley Powell, led an expedition down the Colorado River from the Green River in Wyoming to the Virgin River in Nevada.
It was an arduous and brutal journey of more than 1,000 miles that included crossing the Grand Canyon. It was especially difficult for Powell, who had lost one of his arms in combat during the Civil War. This expedition convinced Powell that only the federal government had the resources necessary to build the infrastructure needed for a western agricultural economy. Powell proposed that the federal government plan and control the water supply in the West.
The Colorado River Basin
The Colorado River basin showing the upper and lower basins. United States Colorado River Watershed Colorado Mexico, 2006. Denver, Colo.: Bureau of Reclamation, U.S. Dept of the Interior. Photograph
The Colorado River Basin is an area of more than 242,000 square miles that includes parts of California, Nevada, Arizona, Utah, Colorado, New Mexico, and Wyoming. By the early 1900s the seven states that were part of the Colorado River Basin were beginning to build the administrative groundwork that would lead to a dam to control flooding and provide a reliable source of water for all. Herbert Hoover was instrumental in creating the water-sharing agreements between the states, which were mostly agreed upon by 1922.
Simultaneously, starting in 1902, many surveys and studies were conducted on the upper and lower Colorado River basins. By 1918, surveys concluded that the Boulder and Black Canyons of the Lower Colorado basin were the best sites for the dam.
Exploratory drilling at potential dam sites began in late 1920 and continued for three years. The role of surveying in the selection of the site was critical. Detailed topographic surveys were conducted in 1920 and 1921 with geologic surveys being conducted from 1921 to 1923. Additionally, the dam had to be built where aggregates were available and where railroads and highways could be built to transport supplies to the site.
Site Selected
In 1924, the Bureau of Reclamation finally recommended construction of a high concrete dam at a site in the Black Canyon based on the surveys by Homer Hamlin a former Los Angeles City Engineer who worked for the Reclamation. The Black Canyon site was chosen for several reasons including accessibility, better foundation material, depth to bedrock, and a greater reservoir capacity. Although the Black Canyon site was chosen, the name Boulder Canyon Project was retained because of prior legislation under that title.
Two men waiting to work on the Hoover Dam in 1931. Bureau of Reclamation.
Then it was on to Congress to get funding for the dam. After years wrangling, the Boulder Canyon Project Act was signed by Calvin Coolidge in December, 1928 – right before the start of Herbert Hoover’s presidency and the Great Depression.
Ironically, it was the depression that accelerated the project. Because of massive unemployment, the planning and assignment of contracts was accelerated, and printed specification for the concrete dam and appurtenant works was completed in December 1930, six months ahead of schedule. By 1931, the contracts were awarded and construction began. Eventually, a fully-equipped city (Boulder City) was built on the arid plateau near the dam site to house the 5,000 workers needed to construct the dam.
Hard Work
Native American high-scalers working on the Hoover Dam project, Bureau of Reclamation
In the meantime, life was rough for the workers preparing the site for the construction of the dam. Workers and their families were forced to live in temporary encampments and tent cities. One such camp was located at Cape Horn, about a mile upstream from the dam site. The encampment was officially known as Williamsville, but among the workers it was known as Ragtown; a more appropriate name. Conditions at Ragtown were horrible; no fresh water or sanitary facilities, and little or no shade in which to escape the stifling heat (up to 115 degrees F). The heat was so bad that groups of people would huddle in the shadow of tents or small bushes or stand up to their necks in the river in an effort to keep cool.
In the diversion tunnels the problem was even worse. Temperatures underground often reached as high as 140 degrees. Heat prostration became a deadly problem, killing one worker every two days during the summer of 1933.
The first bucket of concrete was placed in the dam the morning of June 6, 1933, nearly 18 months ahead of schedule.
Dedicated
Boulder Dam was dedicated by President Franklin Roosevelt on September 30, 1935. Almost everything about Hoover Dam can be described as BIG.
First Aid station with ambulance at Hoover Dam. Bureau of Reclamation.
5,500,000 cubic yards of material excavated;
4,400,000 cubic yards of concrete placed;
45,000,000 pounds of reinforcement steel used;
21,670,000 pounds of gates and valves.
44,000,000+ tons of steel were formed and welded into 14,800 feet of penstock and outlet pipes. 5,000,000+ barrels of cement were used in construction of the dam, which weighs more than 6,600,000 tons.
The average number of people employed on the project was 3,500 with over 5,200 employed during the peak of construction. One-hundred and twelve men died due to accidents or illness related to construction activities.
Glaha, Ben D, photographer. Construction of Boulder Dam, Boulder City, Nevada--A surveyor on a Boulder Dam triangulation point. Hoover Dam Nevada Boulder City Arizona, 1934.
Expected and unexpected consequences
During the design of Boulder Dam, it was recognized that the tremendous weight of the dam and lake, more than 41,000,000,000 tons, might have a localized effect on the Earth's crust. Estimates made prior to construction indicated that up to three feet of deformation could occur due to the weight. Precise measurements by surveyors taken in the area surrounding the site before and after the filling of Lake Mead showed seven inches of settlement in the Earth's crust in the first fifteen years following completion of the dam.
Unexpectedly, the weight of the water caused the first reservoir induced earthquakes. During the first ten years of operation, more than 6,000 minor tremors, the strongest in 1939, were recorded in the vicinity of Lake Mead. No tremors had been recorded for the fifteen years prior to construction of the dam.
Today, we still rely on the Hoover Dam to harness the power of the Colorado River, both in times of drought and in times of deluge.
Now we have technology that would make such a project easier, but all construction still relies on the precise work of surveyors. Tools such as total stations, drones and prisms make surveying and monitoring easier, and Berntsen is here to help.
Thank you, surveyors, for a job well done!