No small task
Before construction of the Hoover Dam could begin, infrastructure had to be built, and Colorado river needed to be diverted away from the construction site.
Infrastructure
Infrastructure
- Seven miles of 22-foot-wide highway from Boulder City to the dam site.
- 22.7 miles of railroad tracks from the Union Pacific main line in Las Vegas to Boulder City and another 10 miles from Boulder City to the dam site.
- A 222 mile long power line from San Bernardino, California, to the dam site to supply electricity for construction.
High Scalers
Millions of years of erosion caused cracks in the canyon walls. All of the loose rock had to be removed before construction could begin. Men known as "high scalers" climbed down the canyon walls on ropes to drill bore holes and place explosives. It was quite possibly the most physically demanding job. They were lowered down loaded with equipment and water jugs, and a 45 pound jackhammer was lowered down for them to use. The work was extremely dangerous due to the high possibility of being struck by falling objects. |
Tunnels
Four 56-foot in diameter tunnels were bored through Black canyon to divert the Colorado River, two on the Nevada side and two on the Arizona side. Jackhammers were used to bore holes into the rock for explosives, 500 drills were purchased for the project. A structure called a "drilling jumbo" was built on the back of a 10 ton truck to speed up the process. The truck backed up to the rock and 24 to 30 drills bored the holes. The drilling jumbo allowed half of the rock face to be prepared for demolition. Afterward, the drilling jumbo moved to the other side and repeated the process. One ton of dynamite was used for every 14 feet of tunnel dug.
In March 1932, work started on lining the tunnels with concrete. Lining the tunnels started with the base, followed by the sides, and then the ceiling. The tunnels were completed that November, and are three feet thick. Earth and rock were then dumped into the river, forcing it into the tunnels. Water flowed freely through the tunnels for the next two years.
Four 56-foot in diameter tunnels were bored through Black canyon to divert the Colorado River, two on the Nevada side and two on the Arizona side. Jackhammers were used to bore holes into the rock for explosives, 500 drills were purchased for the project. A structure called a "drilling jumbo" was built on the back of a 10 ton truck to speed up the process. The truck backed up to the rock and 24 to 30 drills bored the holes. The drilling jumbo allowed half of the rock face to be prepared for demolition. Afterward, the drilling jumbo moved to the other side and repeated the process. One ton of dynamite was used for every 14 feet of tunnel dug.
In March 1932, work started on lining the tunnels with concrete. Lining the tunnels started with the base, followed by the sides, and then the ceiling. The tunnels were completed that November, and are three feet thick. Earth and rock were then dumped into the river, forcing it into the tunnels. Water flowed freely through the tunnels for the next two years.
Cofferdams
Once the tunnels were competed, two cofferdams were built in Black Canyon to isolate the construction site and protect it from flooding. The upper cofferdam was 98 feet tall, 450 feet long, and 750 feet thick at its base. The lower cofferdam was 66 feet tall, 350 feet long, and 550 feet thick at its base. After the cofferdams were completed, two of the tunnels were plugged with concrete 400 feet thick. Another was plugged, but had four six-foot diameter holes left in and fitted with gate valves. The last tunnel was fitted with a 1,000 ton steel gate.
Once the tunnels were competed, two cofferdams were built in Black Canyon to isolate the construction site and protect it from flooding. The upper cofferdam was 98 feet tall, 450 feet long, and 750 feet thick at its base. The lower cofferdam was 66 feet tall, 350 feet long, and 550 feet thick at its base. After the cofferdams were completed, two of the tunnels were plugged with concrete 400 feet thick. Another was plugged, but had four six-foot diameter holes left in and fitted with gate valves. The last tunnel was fitted with a 1,000 ton steel gate.