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Engineers decided to build the earthfill embankment with materials readily
available at the site. This feat required huge tools like a bucketwheel
excavator with eight-1.8 cubic yard buckets. The excavator could scoop
up rocks within its 30-foot path and unload the rocks onto a conveyor
belt about three miles long. The belt moved the rocks into a system
that fed 10 hoppers at a loading station. At the station, the hoppers
loaded trains of 40 gondolas, pulled by double diesel electric locomotives. The trains, loaded in 15 minutes, travelled some 12 miles to the gondola dumper, where the loaded gondolas were disconnected from the train and the engine moved into place to pick up an empty string of cars for a return trip. The dumper could seize two fully loaded gondolas at a time and turn them upside down, dumping their 220-ton load of rocks onto a half-mile conveyor belt that crossed the Feather River to a stockpile near the dam. Running 24 hours a day with the three pairs of locomotives, 45-50 trains were dumped every 24 hours, producing nearly 500,000 cubic yards of material each week. Hyatt Powerplant is located underneath the dam and lake. Its chamber was blasted from a metavolcanic rock formation and is large enough to hold almost two football fields. Miners drilled holes, loaded them with explosives, and blasted away the rock. Rock bolts or “structural steel framing” were used to hold the newly exposed rock. The bolts were anchored in place by an expansion anchor, tensioned to a specified stress, packed and sealed at the rock face, and finally grouted. Another major challenge was the building of the California Aqueduct. Much of the aqueduct parallels the San Andres Fault Zone and crosses other major faults. More than 100 potential alignments were studied, and evaluations considered the seismic hazards the faults presented. Where the alignment crosses active faults, canal sections or pipelines are located near or at ground level to facilitate quick repair. Automatically controlled check gates were also installed upstream of these crossings to shut off flows if an earthquake ruptured the canal. Also, approximately 200 miles of the aqueduct were to cross the westside of the San Joaquin Valley, where unconsolidated soil deposits were known to be prone to shallow subsidence. Once saturated, settlement of these unconsolidated soils would damage the unreinforced concrete lining planned for use in constructing the aqueduct. Field test ponds in subsidence-prone areas produced as much as nine feet of subsidence. To solve this problem, hundreds of water-filled preconsolidation ponds were constructed along the alignment of the aqueduct to ensure that settlement occurred before canal construction. The ponds were kept filled for as long as six months. The Tehachapi Crossing presented another test of engineering ingenuity because the crossing would traverse or parallel several major faults including San Andreas, Pastoria, Garlock, and White Wolf. The simpler and more direct way would have been to drill a single tunnel at a lower elevation. But what if an earthquake struck, damaging the tunnel? It could take several months to reach the damaged areas and would leave Southern California without SWP water. So engineers had four tunnels drilled at a higher elevation, near the top of the mountain range. The tunnels are connected by siphons and pipes with access sites for inspections and repairs.
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