Flaming Gorge Dam is on the Green River in northeastern Utah about 32 miles downstream from the Utah-Wyoming border. The concrete thin-arch structure has a maximum height of 502 feet and a crest length of 1,285 feet, and contains 987,000 cubic yards of concrete. The top thickness is 27 feet, and the maximum base thickness is 131 feet.
Floodwaters are spilled through a 675-foot-long tunnel spillway extending through the left abutment. The concrete-lined tunnel has a maximum capacity of 28,800 cubic feet per second and reduces in size from 26.5 feet in diameter at the upstream portal to 18 feet in diameter at the downstream portal. The spillway intake structure is controlled by two 16.75- by 34-foot hydraulically operated fixed-wheel gates.
The outlet works consist of two 72-inch steel pipes through the dam, reducing to 66 inches at the toe of the dam and continuing downstream to a valve structure on the left riverbank where discharge is directed into the river channel. Each outlet is controlled by a 66-inch hydraulically operated ring-follower gate at the downstream toe of the dam and a 66-inch hydraulically operated hollow-jet valve at the valve structure. Discharge capacity at elevation 6,045.0 feet is 4,000 cubic feet per second.
The Flaming Gorge Reservoir has a total capacity of 3,788,900 acre-feet and an active capacity of 3,515,700 acre-feet. At normal water surface elevation, the reservoir has a surface area of 42,020 acres. Three 10-foot-diameter penstock pipes near the center of the dam convey water to the powerplant. The powerplant is at the downstream toe of the dam and houses three 51,000-kilowatt generators driven by three 50,000-horsepower Francis-type turbines.
Foundation: Steep-sided narrow canyon composed of siliceous sandstone and hard quartzites inter-bedded with softer shales, siltstones, and argillates.