Nevada/Arizona BorderRock clearance\nBefore construction began on the dam itself it was necessary to remove loose rock from the canyon walls. The men who removed this rock were called \"high-scalers.\" While suspended from the top of the canyon with ropes high-scalers climbed down the canyon walls and removed the loose rock with jackhammers and dynamite.\n\n\nConcrete pouring\nThe first concrete was placed into the dam on June 6, 1933. Since no structure of the magnitude of the Hoover Dam had been constructed, many of the procedures used in construction of the dam were untried. Since concrete heats up and contracts asit cures, uneven cooling and contraction of the concrete posed a serious problem. The Bureau of Reclamation engineers calculated that if the dam were built in a single continuous pour, the concrete would have taken 125 years to cool to ambient temperature. The resulting stresses would have caused the dam to crack and crumble.[9] To solve this problem the dam was built in a series of interlocking trapezoidal columns. Each pour was no more than six inches deep. Because of this depth it is extremely unlikely that construction workers were accidentally buried alive in the concrete, contrary to popular folklore.[10]. To further cool the concrete each form contained cooling coils of 1 inch (25.4 mm) thin-walled steel pipe. River water was circulated through these pipes to help dissipate the heat from the curing concrete. After this, chilled water from a refrigeration plant on the lower cofferdam was circulated through the coils to further cool the concrete. After each layer had sufficiently cooled the cooling coils were cut off and pressure grouted by pneumatic grout guns. The concrete is still curing and gaining in strength as time goes on.[11]\n\nThere is enough concrete in the dam to pave a two-lane highway from San Francisco to New York [12].\n\n\nConstruction deaths\nThere were 112 deaths associated with the construction of the dam.[10][13] There are different accounts as to how many people died while working on the dam and who was the first and last to die. A popular story holds that the first person to die in the construction of Hoover Dam was J. G. Tierney, a surveyor who drowned while looking for an ideal spot for the dam. Coincidentally, his son, Patrick W. Tierney, was the last man to die working on the dam, 13 years to the day later.[10][13] 96 of the deaths occurred during construction at the site. However, another surveyor died prior while surveying a potential location for the dam and these statistics do not include other incidental and coincidental (heat stroke, heart failure, etc) deaths during construction. [10]\n\n\nPower plant\n \nThe hydroelectric generators at Hoover damThe seventeen turbine-generators at this powerhouse generate a maximum of 2,074 megawatts of hydroelectric power.\n\nExcavation for the powerhouse was carried out simultaneously with the excavation for the dam foundation and abutments. Excavation for the U-shaped structure located at the downstream toe of the dam was completed in late 1933 with the first concrete placed in November 1933.\n\nGenerators at the Dam\'s Hoover Powerplant began transmission of electricity from the Colorado River to Los Angeles, California 266 miles (428 km) away on October 26, 1936. Additional generating units were added through 1961.\n\nWater flowing from Lake Mead through the gradually-narrowing penstocks to the powerhouse reaches a speed of about 85 miles per hour (137 km/h) by the time it reaches the turbines. The entire flow of the Colorado River passes through the turbines. The spillways are rarelyused.\n\nHydroelectric power plants have the ability to vary the amount of power generated, depending on the demand. Steam turbine power plants are not as easily \"throttled\" because of the amount of thermodynamic inertia contained in their systems.\n\n\nArchitectural style\n \nThe dam crosses the border between two time zones, the Pacific Time Zone and the Mountain Time ZoneThe initial plans for the finished facade of both the dam and the power plant consisted of a simple, unadorned wall of concrete topped with a Gothic-inspired balustrade and a powerhouse that looked like little more than an industrial warehouse. This initial design was criticized by many as being tooplain and unremarkable for a project of such immense scale, so Los Angeles-based architect Gordon B. Kaufmann was brought in to redesign the exteriors. Kaufmann greatly streamlined the buildings, and applied an elegant Art Deco style to the entire project, with sculptured turrets rising seamlessly from the dam face and clock faces on the intake towers set for Nevada and Arizona time, in the Pacific and Mountain time zones respectively (although because Arizona does not observe daylight saving time, the two clocks show the same time throughout much of the year). Border, Nevada/Arizona