THE DAM HISTORY Q. When was Glen Canyon investigated as a potential damsite? A. First in 1921, then again in 1946 and in subsequent years. Q. When was Glen Canyon Dam authorized for construction? A. April 11, 1956, as part of the Colorado River Storage Project. Q. When did work actually begin? A. The first blast was detonated on October 15, 1956. COMPLETION SCHEDULES Q. When is the dam scheduled to be finished? A. Construction of the dam and powerplant is scheduled for completion in March 1964. Q. When is the first power scheduled to be generated? A. The first power should go on the line in the spring of 1964. EXCAVATION COFFER DAMS Q. What are the coffer dams? A. Large, temporary earth dams across the floor of the canyon and located upstream and downstream from the foundation and keyway areas which mark the axis of the dam. Q. Why are coffer dams built? A. To divert the Colorado River around the damsite through huge diversion tunnels and to keep water out of the work areas during construction of the dam and powerplant. The deepest excavation to bedrock in the dam foundation is 137 feet below the former river level. DIVERSION TUNNELS Length (West) 2,749 feet Length (East) 3,011 feet Diameter (lined) of both tunnels 41 feet Q. Why does the west diversion tunnel carry the most water? A. Because the intake of the west tunnel is 34 feet lower than the intake of the east tunnel. SPILLWAYS Q. Where are the spillway intakes located? A. They are just upstream from the keyways, one on each rim of the canyon. Q. Where will the spillways discharge? A. Steep, inclined tunnels will extend from the spillway intakes to intersect with the diversion tunnels far below. Thus, water going through the spillways will emerge from the diversion tunnels as the river water now does. Q. What is the maximum combined capacity of the two spillways? A. 276,000 cubic feet per second. POWERPLANT Q. Where will the powerplant be located? A. On the upstream side of the Glen Canyon Bridge just below the dam. The powerhouse will extend across the canyon floor parallel to the bridge. Q. How large will the powerplant be? A. The powerhouse structure will be about 665 feet long and about 160 feet, or 16 stories high, above the downstream river level. Eight generating units will be installed. The rated capacity will be 900,000 kw for the powerplant. Q. What are the square columns between the dam and the powerplant? A. These huge concrete piers will support the 15-foot diameter