BOULDER CANYON PROJECT — NELSON 441 



whose two wings nestle close to the cliffs, and the central sec- 

 tion connecting them lies on the downstream face of the dam. The 

 length around the U next to the cliffs and dam is nearly that of 

 six ordinary residence blocks and the average width of each wing 

 or central section approximately a half block. The height from 

 lowest concrete to top of highest parapet is that of a 20-story 

 building, and the parapet rises the height of 12 stories above low 

 water surface in the tail race. The roof covers an area of 4 acres, 

 is 41/^ feet thick (to resist rock falling from the cliff above) and is 

 composed of seven laminations, two of these being reinforced con- 

 crete, another asphalt paving, and others of sand and gravel. Sup- 

 port for the roof is provided primarily by 11,600,000 pounds of 

 structural steel trusses and beams, and beneath the roof are 10 acres 

 of floors. 



When finally completed the power plant will contain fifteen 115,000- 

 horsepower units, and two of 55,000, a total installed capacity of 

 1,835,000 horsepower. Included in the machinery that will be placed 

 in the plant are 14-foot diameter butterfly valves, 40-foot diameter 

 turbine scroll cases, 82,500 kilovolt-ampere generators, 55,000 kilo- 

 volt-ampere power transformers for raising the generator voltage 

 from 16,500 to transmission voltage of 287,500, and 300-ton cranes. 

 All units in the plant may be controlled from a single station or each 

 unit may be run from a control board near it. Operating at rated 

 capacity, the power plant would be capable of producing sufficient 

 electric energy to supply complete domestic light and power for all 

 the 8,500,000 inhabitants of the Colorado River Basin, or, calculated 

 in a different manner, it would be enough to furnish each and every 

 family in the United States with light from a 40-watt bulb. 



Approach to the powerhouse is first by way of two elevators, which 

 descend from the dam crest the height of a 44-story building, and 

 then by passageways through the dam a block in length to the central 

 section. Another route is by a mile and a half of road and a 1,900- 

 foot tunnel which connect the Boulder City highway with the down- 

 stream end of the Nevada powerhouse wing. 



A high-tension switchyard, at the ends of the transmission lines, 

 is located a thousand feet from the Nevada canyon rim opposite the 

 central section of the power house. Remote control from the power 

 plant, of the oil circuit breakers located at the switchyard, is pro- 

 vided by electric circuits running from the central section upward 

 through the cliff in an inclined shaft and thence continuing to the 

 switchyard in a 6- by 8-foot concrete conduit. 



Diversion of the Colorado River while the dam and power plant 

 were being constructed presented a difficult problem owing to the 

 narrowness of the canyon, the extent in and up-and-down-stream 



