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<br />000337 <br /> <br />trending ridge which rises steeply from the channel bottom to an elevation of about 6,400 <br />feet,then continues to rise at a flatter slope. The left abutment consists of a narrow, Iow-Iying, <br />east-west trending ridge. The ridge rises steeply from the valley bottom to an elevation of <br />approximately 6,375 feet, then continues to rise on a flatter slope. <br /> <br />The existing dam axis runs from southwest to northeast from the right abutment, <br />bending gently to the east as it reaches the left abutment. The dam has a concrete "duckbill" <br />spillway with an arch shaped crest approximately 140 feet long located at the left abutment <br />interface. The existing spillway has a 40 foot wide concrete chute which ends in a baffle <br />bIock/riprap energy dissipation basin, A hydraulically controlled 36-inch diameter primary <br />outlet releases water from the reservoir at a location to the right of the spillway into the <br />spillway chute. An irrigation outlet exists to the left of the spillway. <br /> <br />The present hydraulic capacity of the primary outlet of Elkhead Reservoir is 165 cfs. To <br />meet dam safety requirements, Elkhead Dam (if not enlarged) will undergo major spillway <br />modifications in the near future, These modifications would likeIy include enlargement of the <br />outlet capacity to at least 250 cfs. There are currently no hydroelectric generation facilities at <br />the dam. The maximum conveyance of the Elkhead Creek channel below the reservoir has <br />been estimated at 250 cfs; flows above this Ievel have historically resulted in minor flooding of <br />fannlands. <br /> <br />A gravel road crosses the 20 foot wide crest of Elkhead Dam with a bridge over the <br />spillway chute, The riprap faced upstream dam slope is 3: 1 and the downstream grass lined <br />slope is 2.5: 1. A 20 foot wide cutoff trench extends to bedrock. A 6 foot wide vertical <br />chimney drain/filter provides internal drainage of the embankment. The drain is cOlmected to a <br />3 foot high by 12 foot wide horizontal graveI finger drain at the foundation interface. <br /> <br />Elkhead Reservoir is located primarily on lands owned by the Colorado Division of <br />Wildlife and the Bureau of Land Management. At its upstream, the reservoir extends onto <br />privateIy held lands at several locations. Lands surrounding the reservoir are used primarily <br />for livestock grazing. Surrounding Iands are characterized by upland scrub vegetation with <br />very few trees around the perimeter of the reservoir. <br /> <br />Reservoir Operations <br />Storage Ownership <br /> <br />Elkhead Reservoir is currently owned by the Yampa Project Participants and the <br />Colorado Division of Wildlife. The Yampa Project Participants is comprised of Colorado-Ute <br />Electric Association, Inc., Platte River Municipal Power Association, Salt River Agricultural <br />Improvement and Power District, Tri-State Generation and Transmission Association, Inc. and <br />Utah International, Inc. Tri-State is the managing partner of the Yampa Project Participants. <br />The Yampa Project Participants own 8,310 af of storage space in Elkhead Reservoir for use as <br />a backup cooling water supply for the Craig Station thermaI-electric power generation facility. <br />The remaining 5,390 af is leased by the City of Craig from the Division of Wildlife for <br />municipal and indnstrial purposes. The City of Craig is currently negotiating with Division of <br />Wildlife to purchase this storage space. Approximately 3,722 af of the total 13,700 af storage <br />space lies below the level of the primary outlet works of the reservoir and is, practically <br />speaking, dead storage. <br /> <br />3 <br />