|
<br />(.C'
<br />~
<br />00
<br />
<br />--
<br />
<br />.--
<br />-
<br />
<br />WhaT is the eSlimmed al/nllal evaporation
<br />all the reservoir?
<br />800,000 acre-feet.
<br />
<br />Tunnels, Towers, Penstocks, and
<br />Spillways
<br />
<br />HOIV was the rivl'r divened during dam
<br />constrtfctiOll?
<br />By an earth and rockfill cofferdam,
<br />through fOllr 50-foot diameter tunnels,
<br />excavated to 56 feet and lined with 3
<br />feet (300,000 cubic yards) of concrete.
<br />Driven through the canyon walls, two on
<br />each side of the river, the four tunnels
<br />had a total length of 15,946 feet, nr
<br />about 3 miles. These tunnels could cany
<br />over 200.000 cubic fcet or almost )1/2
<br />million gallons of water per second! The
<br />river was diverted through the two
<br />Arizona tunnels on November 14, 1932.
<br />
<br />After their use for river diversion, how
<br />were rhe fUJll/els used?
<br />The inner tunnels were plugged with
<br />concrete approximately one-third their
<br />length below the inlets, and the outer
<br />tunnels were plugged approximately half-
<br />way. The two inner tunnels contain
<br />30-foot diameter steel pipes which con-
<br />nect the intake towers in the reservoir
<br />with the penstocks to the powerplant and
<br />the canyon wall outlet works. The down-
<br />stream halves of the two outer tunnels arc
<br />used for spillway outlets.
<br />
<br />What gates arc installed on the tunnels?
<br />The inlcts of the two outer tunnels are
<br />pemlancntly closed with 50- by 50-foot
<br />bulkhead gates. Each gate, with steel
<br />frame, weighs about 3,000,000 pounds,
<br />and required 42 railroad cars for ship-
<br />ment. At the outlets of the two inner
<br />tunnels, 50- by 35-foot Stoney gates are
<br />installed. These gates can be closed
<br />when the tunnels need to be emptied
<br />for inspections or repairs.
<br />
<br />Jt'hat are the intake towers?
<br />They are four reinforced-concrete stmc-
<br />tures located above thc dam, two on
<br />each side of the canyon. Diameter of
<br />these towers is 82 teet at the base, 63
<br />
<br />feet 3 inches at the top, and 29 teet 8
<br />inches inside. Each tower is 395 feet
<br />high and each controls one-fourth the
<br />supply of water for the powerplant tur-
<br />bines. The four towers contain 93,674
<br />cubic yards of concrete and 15,299,604
<br />pounds of steel.
<br />
<br />How are these towers connected to the
<br />power plant and outlet valves?
<br />By 30-foot-diameter penstocks installed
<br />in 37- and 50-foot diameter concrete-
<br />lined tunnels. The upstream intake
<br />towers are connected to the inner diver-
<br />sion tunnels by 37-foot-diameter inclined
<br />tunnels. Thirty-seven-foot diameter tun-
<br />nels also connect the downstream towers
<br />to the penstocks and outlet works.
<br />
<br />How do the intake towers control water
<br />flow?
<br />Through two cylindrical gates, each 32
<br />feet in diameter and 11 feet high. One
<br />gate is near the bottom and the other
<br />near the middle of each tower. The gates
<br />arc protected by trash racks. Total weight
<br />of the gates is 5,892,000 pounds; the
<br />trashracks weigh 7,024,000 pounds.
<br />
<br />What pipes are installed in the tunnels for
<br />resen'oir outlets?
<br />There are 4,700 feet of 30-foot-diameter
<br />pipe and 2,000 feet of 81!2-foot-diameter
<br />pipe. Maximum thickness of the largest
<br />pipe is about 3 inches.
<br />
<br />How are the 30-joot-diameter pipes con-
<br />nected to the pmvefplant turbines?
<br />By sixteen 13-foot-diameter platesteel
<br />penstocks installed in 18-foot-diameter
<br />concrete~lined tunnels. Total length of
<br />these penstocks is 5,800 feet.
<br />
<br />What are the main characteristics of the
<br />penstock and outlet pipes?
<br />Forty-four thousand tons of steel were
<br />formed and welded into 14,800 feet of
<br />pipe varying from 8 'h to 30 feet in
<br />diameter. Each length of the largest pipe
<br />-12 feet long, 30 fect in diameter, and
<br />2 M inches thick - was made from 3
<br />steel plates, of such weight that only two
<br />plates could be shipped from the steel
<br />mill to the fabricating plant on one
<br />railroad car. Two such lengths of pipe
<br />
<br />welded together make one section
<br />weighing approximately 135 tons and, at
<br />intersections with the penstocks. as much
<br />as 186 tons.
<br />
<br />What outlets are used?
<br />Four 72-inch needle valves in each inner
<br />diversion tunnel plug outlet; two 84-inch
<br />needle valves in the Arizona canyon wall
<br />valve house; and two S4-inch needle
<br />valves in the Nevada canyon wall valve
<br />house. The needle valves in the canyon
<br />walls are about 180 feet alxwe the river
<br />level. Canyon wall valves arc designed
<br />to bypass water around the dam under
<br />emergency or flood conditions, or to
<br />empty the penstocks for maintenance
<br />work.
<br />
<br />U'hat is the maximum capacity of these
<br />works ?
<br />About 118,000 cubic feet per second
<br />(ft'/s): 32,000 1'(3/s for power generation
<br />and 86,000 ft'ls of valve discharge. One
<br />cubic foot per second of water equals
<br />nearly 71/2 gallons passing a given point
<br />in one second.
<br />
<br />What are the A/izona and Nevada
<br />spillways?
<br />Concrete-lined open channels about 650
<br />feet long, 150 feet wide, and 170 feet
<br />deep on Gach canyon wall. More than
<br />600,000 cubic yards of rock were ex-
<br />cavated for the spillways. The spillway
<br />walls are lined with 18 inches of con-
<br />crete and the floors with 24 inches;
<br />127,000 cubic yards of concrete were
<br />placed for the spillways.
<br />
<br />How is water discharged from the
<br />spillways?
<br />Into the outer diversion tunnels through
<br />inclined shafts 50 feet in'dianleter and
<br />600 feet long. The discharge is con-
<br />trolled by four automatically or manually
<br />operated 100- by 16-foot, 5oo,000-pound
<br />drum gates on each spillway crest. Max-
<br />imum water velocity in the spillway tun-
<br />nels is about 175 feet per second, or 120
<br />miles per hour.
<br />
<br />45
<br />
|