Five (5) years It took five years to build and required three-quarter million cubic yards of concrete. That's enough concrete to build a 16-foot-wide road from New York to San Francisco, California. Since the completion of the bypass bridge in October 2010, the Hoover Dam has become even more impressive. The new span is 1,079 feet long and includes two large bascule bridges that open to let boats pass under the dam.
The new Hoover Dam Bridge was built by the same contractor as the old one: Morrison-Knudsen Co. Of Denver. But instead of using traditional construction methods, they designed and built the new bridge with the help of computer technology. The digital design process allowed them to create three-dimensional models of the project before any dirt was moved. This saved time and money while producing a quality product.
The new Hoover Dam Bridge was also constructed using "cut-and-cover" construction. This means that the original structure on either side of the riverbed is removed, then the new bridge is put in its place.
Finally, the new Hoover Dam Bridge was designed to withstand an earthquake. The old one collapsed during an earthquake in 1967.
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The long-planned Hoover Dam Bypass Project began in January 2005, and in October 2010, a concrete arch bridge with a 1,060-foot (322-metre) span—the longest in North America for that type of bridge—opened for through traffic within view of Hoover Dam. The $750 million bypass route runs along the right-of-way of the former Boulder City Railroad Bridge Road over the Colorado River about 5 miles (8 km) south of downtown Las Vegas.
The first section of the highway to open was from Interstate 15/U.S. Highway 93 north to just past Boulder City's eastern limits at Paradise Road. This 3-mile (4.8-km) stretch opened on July 17, 2008. The following year, the remaining road was completed and the entire by-pass route was opened to traffic.
The Hoover Dam Bypass Project was created by the Nevada Department of Transportation and designed by Kiewit Construction Company. Funding for the project came from several sources including a federal grant, state funds, and special assessments levied against property owners along the new roadway. The total cost of the project was $750 million.
The new bridge replaces an older structure that was damaged in 1998 when Hurricane Elijah crossed into Nevada from California with winds of 150 mph (240 kph).
For three years The San Francisco-Oakland Bay Bridge took little more than three years to build. Surprisingly, for a modern construction project, the work was finished six months ahead of time and under budget.
The new bridge is a suspension bridge with two towers that reach 315 feet high. It has nine traffic lanes and two sidewalks. The main span measures 1450 feet from tower to tower. The longest single truss in the world at that time was used for the bridge. Its length is 180 feet and it weighs about 9800 tons.
The total cost was $24 million ($145 million in today's dollars). Of this amount, $7 million came from the federal government's Public Works Administration (PWA) program. PWA funds were also used to pay for some of the equipment needed for the project: cranes, shovels, trucks, etc.
In October 1937, just over three years after work on the bridge began, it was opened to traffic. At the time, it was said to be the most expensive public works project in America. However, by today's standards it seems relatively cheap ($145 million in 1937 dollars).
The old bridge was a swing bridge that connected Oakland with Yerba Buena Island. It had five traffic lanes and one sidewalk.
The widths of the blocks ranged from 25 to 60 square feet, depending on their placement. Columns of blocks were connected in alternating and interconnected patterns. The concrete of the Hoover Dam would cure in 125 years using conventional or natural processes. Crews, on the other hand, applied some novel engineering approaches to speed up the process. They used ultra-high-strength concrete with steel reinforcements instead of traditional concrete with wooden reinforcements to create a material that could be placed at room temperature and still retain its strength for over 100 years.
The height of the dam above Lake Mead is about 710 feet (220 m). Its length along the Nevada shoreline is 998 feet (300 m). It stands as the tallest freestanding concrete structure in the world. The actual size of the Hoover Dam block is 56 by 56 inches (140 by 140 cm) and weighs approximately 22,000 pounds (10,000 kg).
There are several reasons why the dam's designers chose to use concrete blocks instead of one continuous slab. Concrete blocks are an efficient way to transmit compression forces across large areas. The individual blocks form strong bonds with each other through an adhesive agent called cement. This means that the dam could support more weight than a comparable single-slab structure. In addition, if any one block were to become damaged, it could be replaced without having to replace the entire surface. Last but not least, concrete is a popular building material because it looks good and is easy to work with.
It is the biggest concrete building ever constructed in the United States, and it will revolutionize the desert southwest. 1935: Four months before President Franklin D. Roosevelt dedicates one of the greatest hydroelectric projects in US history, the last concrete is laid at the Hoover Dam site. The $44 million project is the brainchild of U.S. Bureau of Reclamation (BR) chief William H. Hoover. When it is complete in late 1936, the dam will be the highest (at 711 feet), longest (at 2 miles), and deepest (at 286 feet) of its kind in the world.
The BR has determined that the only way to secure water for its growing population and agricultural industry is to build a large dam on the Colorado River. The first attempt by the government agency to obtain funding for such a project failed when the Federal Power Act was rejected by Congress in 1922. The second effort succeeded when Congress passed the Boulder Canyon Project Act in 1928, which authorized construction of what is now known as the Hoover Dam.
He will also mention some unsung heroes who helped make the dream a reality including former Arizona Governor Benjamin F. Miller and U. S. Senator Carl Hayden.
The cooling of the concrete was a serious issue with a construction the size of the Hoover Dam. Engineers estimated that the vast volume of concrete would take over a century to cool, and that once cold, the dam would break, leaving it worthless. The dam was built in rows and columns of blocks to avoid this. The blocks are held in place by steel cables attached to anchors at each end; these cables can be tightened or loosened as necessary.
Another challenge was the location of the dam. The desert land on which it was being built is used for farming during the summer months, so access was difficult. A railroad had to be built specifically to haul materials to the site, and later to transport finished cement from the plant across the top of the dam.
When the Hoover Dam was completed in 1935, it was the largest concrete structure in the world. It has since been replaced by larger dams, but it remains an important landmark and vital part of the infrastructure of Nevada and Arizona.
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