Glen Canyon Dam, 15 miles upstream from Lees Ferry, is the key feature of the CRSP. This 710-foot-high structure provides more storage capacity than all other storage features of the project combined. The concrete arch dam has a crest length of 1,560 feet and contains 4,901,000 cubic yards of concrete. Thickness of the dam at the crest is 25 feet, and the maximum base thickness is 300 feet.
A separate spillway is constructed in each abutment. Each spillway consists of an intake structure with two 40- by 52.5-foot radial gates and a lined spillway tunnel. The downstream portions of the spillway tunnel were used during construction as diversion tunnels. Each spillway tunnel reduces in size from 48 to 41 feet in diameter. The combined spillway discharge capacity is 208,000 cubic feet per second at an elevation of 3,700.0 ft.
The outlet works near the left abutment of the dam consist of four 96-inch-diameter pipes. Each outlet is controlled by one 96-inch-ring follower gate and one 96-inch hollow-jet valve. The combined river outlet works capacity is 15,000 cubic feet per second.
Total capacity for Lake Powell is 27 million acre-feet, and the active capacity is 20,876,000 acre-feet. At normal water surface elevation, the reservoir has a length of 186 miles and a surface area of 161,390 acres.
The powerplant at the toe of the dam consists of four 118,750-kilowatt and four 136,562-kilowatt generators driven by eight turbines. Total nameplate generating capacity for the powerplant is 1,021,248 kilowatts. Eight penstocks through the dam convey water to the turbines. Each penstock reduces in size from 15 to 14 feet in diameter.
Navajo sandstone forms the canyon walls at the damsite and throughout most of the reservoir basin. The sandstone is remarkably uniform and homogeneous over wide areas and nearly identical samples can be obtained from areas separated by many miles. The Navajo sandstone is buff to reddish, medium to fine-grained, and moderately hard to soft. It is massive with pronounced crossbedding and commonly indistinct horizontal bedding. The sandstone is moderately porous and highly absorptive, owing to the high capillarity created by the small size of intergrain pore spaces.