Page images
PDF
EPUB
[merged small][merged small][merged small][merged small][merged small][merged small][merged small][graphic][subsumed][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small]

Engin. Library

As the Nation's principal conservation agency, the Department of the Interior has responsibility for most of our nationally owned public lands and natural resources. This includes fostering the wisest use of our land and water resources, protecting our fish and wildlife, preserving the environmental and cultural values of our national parks and historical places, and providing for the enjoyment of life through outdoor recreation. The Department assesses our energy and mineral resources and works to assure that their development is in the best interests of all our people. The Department also has a major responsibility for American Indian reservation communities and for people who live in Island Territories under U.S. administration.

91475

YELLOWTAIL UNIT

Missouri River Basin Project-Montana-Wyoming

General Information

Yellowtail unit consists of a dam and appurtenant works, reservoir, powerplant, switchyard, visitor center, and an afterbay dam. It is part of the Missouri River Basin project, a resources development program authorized by Congress in 1944 for the conservation, control, and use of the water resources of the Missouri River Basin. Yellowtail unit is a multipurpose development from which the principal benefits include irrigation, municipal-industrial water supply, power generation, flood control, sediment retention, improvement of fish and wildlife resources, and recreational opportunities.

Yellowtail Dam

Location: On the Bighorn River about 21 miles (33.8 kilometers) due north of the Montana-Wyoming State line

Type: Concrete arch

Constructed: 1961-1966

Reservoir: Bighorn Lake

Total capacity to top of exclusive flood control level: 1,375,000 acre-feet at elevation 3657.0 feet (1,696,062,500 cubic meters at elevation 1114.65 meters)

Active capacity: 872,700 acre-feet (1,076,475,450 cubic meters)

Surface area: 17,300 acres (7001 hectares) at elevation 3657.0 feet (1114.65 meters)

Maximum reservoir elevation: 3657.0 feet (1114.65 meters)

Dam dimensions:

Structural height: 525 feet (160.02 meters)

Top width: 22 feet (6.71 meters)

Maximum base width: 145 feet (44.20 meters)

Crest length: 1,450 feet (441.96 meters)

Crest elevation: 3660 feet (1115.57 meters)

Volume: 1,545,700 cubic yards (1,181, 765 cubic meters)

Lowest point in dam foundation excavation: Elevation 3135 feet (955.55 meters)
Spillway:

Unlined approach channel, intake control structure, concrete-lined tunnel through left dam abutment, and
combination stilling basin and flip bucket

The intake control structure has a concrete crest controlled by two 25- by 64.4-foot (7.62-by 19.63-meter) radial gates.

The 1,865-foot-long (568.45-meter) tunnel varies in diameter from 40-1/2 feet (12.34 meters) at the end of the inlet transition to 32 feet (9.75 meters) at the downstream portal.

Elevation top of gates: 3657.00 feet (1114.65 meters)

Crest elevation: 3593.00 feet (1095.15 meters)

Capacity: 92,000 cubic feet per second (2605.16 cubic meters per second) with a maximum reservoir elevation of 3660 feet (1115.57 meters)

Outlet works:

One 84-inch-diameter (2.13-meter) steel irrigation outlet pipe and one 84-inch-diameter (2.13-meter) steel evacuation outlet pipe through dam

A 9.04- by 9.04-foot (2.76- by 2.76-meter) bulkhead gate is provided on upstream face of dam to close either outlet pipe for inspection or maintenance.

Each outlet pipe has an 84-inch (2.13-meter) ring-follower gate for emergency closure and an 84-inch
(2.13-meter) hollow-jet valve for regulation located in an outlet structure at the toe of the dam. A
stilling basin is provided downstream of the hollow-jet valves.

Centerline elevation of irrigation pipe inlet: 3400.00 feet (1036.32 meters)
Centerline elevation of irrigation pipe outlet: 3197.00 feet (974.45 meters)
Centerline elevation of evacuation pipe inlet: 3300.00 feet (1005.84 meters)
Centerline elevation of evacuation pipe outlet: 3197.00 feet (974.45 meters)

Maximum capacity of each pipe: 2,500 cubic feet per second (70.79 cubic meters per second) at reservoir
elevation 3547 feet (1081.13 meters)

« PreviousContinue »