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<br />001090 <br /> <br />. <br /> <br />. <br /> <br />then continues to rise at a flatter slope. The left abutment consists of a narrow, low-lying, <br />east-west trending ridge. :The ridge rises steeply from the val1ey 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 />block/riprap energy dissipation basin. A hydraulicany control1ed 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 likely 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 level have historical1y resulted in minor flooding of <br />farmlands. <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 connected to a <br />3 foot high by 12 foot wide horizontal gravel 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 />privately held lands at several locations. Lands surrounding the reservoir are used primarily <br />for livestock grazing. Surrounding lands are characterized by upland scrub vegetation with <br />very few trees around the perimeter of the reservoir. <br /> <br />Reservoir Operations <br /> <br />Storage Ownership <br /> <br />Elkhead Reservoir is currently owned by Tri-State Generation Association (Tri-State) <br />and the City of Craig. Tri-State owns 8,310 af of storage space in Elkhead for use as a backup <br />cooling water supply for the Craig Station thermal-electric power generation facility. The <br />remaining 5,390 af is owned by the City of Craig for municipal and industrial purposes. <br />Approximately 3,722 af of the total 13,700 af storage space lies below the level of the primary <br />outlet works of the reservoir. Access to this storage (3,772 at) must be by pumping. <br /> <br />Recreational Uses <br /> <br />Elkhead Reservoir is currently a popular recreation site for residents of Hayden and <br />Craig. The reservoir has a boat ramp, swimming and picnicking areas that are heavily used <br />during the summer months. Elkhead Reservoir is widely used for fishing, both from boats and <br />from the reservoir banks. Swimming is somewhat less popular at the reservoir, due in part to <br />high sediment loads of the water carried in from Elkhead Creek. Access to the reservoir is <br />excel1ent with paved roads to within a mile of the reservoir. <br /> <br />3 <br /> <br />,. <br /> <br />j;.,..i <br />