The Yellowtail Unit in Southcentral Montana is part of the Pick-Sloan Missouri Basin Program. It is a multi-purpose development providing irrigation water, flood control, recreation and power generation. Facilities consist of Yellowtail Dam and Bighorn Lake on the Bighorn River, Yellowtail Power Plant at the toe of the dam, Yellowtail Afterbay Dam -- a short distance downstream -- and related structures.
The Crow Indian Reservation, spreading over about 3,500 square miles, encompasses the dam site, a portion of the reservoir area. Yellowtail Dam at the mouth of Bighorn Canyon impounds the river for multi-purpose use. Bighorn Lake is about 72 miles long at maximum water surface elevation, 66 miles long at the top of joint-use storage, and extends into the Bighorn basin of Wyoming. The reservoir is confined in the canyon for most of its length.
Madison limestone which due to topographic expression has been divided into three members; lower, middle, and upper. Special treatment: Grouting beneath the dam, grouting in lower, middle, and upper Madison formations of the right and left abutments, supplemental grouting program of the left abutment.
General
Project
Yellowtail Unit, Pick-Sloan Missouri River Basin Program
Dam Type
Concrete thin arch
Location
On Bighorn River, near Fort Smith, Montana in Big Horn County in South-Central Montana, 43 miles southwest of Hardin Montana.
Longitude
-107.95775413513184
Latitude
45.3068700743631
Watercourse
Bighorn River
Reservoir
Bighorn River
Original Construction
1963-1966
National ID Number
MT00576
Base Width
147.00 ft
Dimensions
Top of Exclusive Flood Control Pool (Elevation)
3,657.00 ft
Top Parapet (Elevation)
3,664.00 ft
Structural Height
525.00 ft
Crest Length
1,480.00 ft
Crest Width
22.00 ft
Top of Active Conservation Pool (Elevation)
3,614.00 ft
Top of Inactive Conservation Pool (Elevation)
3,547.00 ft
Volume of Dam Construction Materials
1,545,664.00 cu yds
Spillway Crest Elevation
3,593.00 ft
Streambed at Dam Axis
3,166.00 ft
Crest Elevation
3,660.00 ft
Hydraulic Height (Normal Operating Depth at Dam)
495.00 ft
Top of Joint Use Pool (Elevation)
3,640.00 ft
Top of Dead Storage Pool (Elevation)
3,296.50 ft
Hydraulics & Hydrology
Spillway Type
Concrete tunnel through the left abutment, controlled by two 25- by 64.4- ft radial gates.
Spillway Capacity at Elevation
92,000.00 cfs at 3,660.00 ft
Outlet Works Capacity at Elevation
2,500.00 cfs
Total Water Storage at Elevation
1,381,189.00 acre-ft at 3,660.00 ft
Maximum Water Surface Elevation
1,381,189.00 acre-ft at 3,660.00 ft
Net Generation
510,564,280 kWh
Contact
Owner/Operator
Title: Area Manager Organization: Montana Area Office Address: P.O. Box 30137 City: Billings, MT 59107-0137 Fax: 406-247-7338 Phone: 406-247-7300
Operator
Title: Area Manager Organization: Montana Area Office Address: P.O. Box 30137 City: Billings, MT 59107-0137 Fax: 406-247-7338 Phone: 406-247-7300
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