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<br />YELLOWTAIL UNIT - Lower Bighorn Division
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<br />The Yellowtail Unit, located on the Bighorn River, Big Horn County,
<br />Montana, consists of Yellowtail Dam, Powerplant, and Afterbay Dam.
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<br />The dam is a concrete-arch structure approximately 520 feet high
<br />at the maximum section, and 1,450 feet long at the crest. Four l2-foot-
<br />diameter penstocks, two 7-foot-diameter outlet pipes, and one 9-foot
<br />6-inch diameter pipe outlet is embedded in the concrete of the dam. A
<br />28-foot-diameter concrete-lined diversion tunnel, approximately 860 feet
<br />long, was constructed in the left abutment and connects to the spillway
<br />tunnel. About 1,240 feet of the downstream portion of the spillway
<br />tunnel was used during the diversion period. The spillway, located on
<br />the left abutment of the dam, consists of an unlined inlet channel, an
<br />intake structure with two 25-foot by 64-foot radial gates, a concrete-
<br />lined tunnel transition section, a concrete-lined 32-foot-diameter
<br />tunnel, and a stilling basin.
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<br />The powerplant, located at the toe of the dam, accommodates four
<br />generating units with a capacity of 62,500 kilowatts each, driven by a
<br />87,500-hp. hydraulic turbine.
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<br />The multipurpose dam provides a reservoir of 1,375,000 acre-feet
<br />to regulate runoff for irrigation, flood control, power generation, and
<br />municipal water. Benefits also will be provided for fish and wildlife
<br />and recreation.
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<br />Program FY 1968
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<br />Funds available - $3,926,625
<br />Continue grouting and spillway
<br />modifications on Yellowtail
<br />Dam.
<br />Construct retaining wall on
<br />right abutment.
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<br />Accomplishments FY 1968
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<br />Expenditures - $2,427,174
<br />Grouting contract 50% complete and
<br />spillway modification contract
<br />69% complete.
<br />Contract for retaining wall 15%
<br />complete.
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