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<br />, , <br /> <br />. <br /> <br />. <br /> <br />, . <br /> <br />rights, and the divertib1e return f10ws,wi11 average 157,500 acre-feet <br />annually (140,700 acre-feet in 1973 DPR). <br /> <br />The project water supplies ~re estimated using potential reservoir <br />seepage rates ranging from 30 ft Is to 60 ft3/s,with reservoir contents <br />at elevations 4350 and 4392, respectively. These reservoir seepage <br />rates were utilized in the water supply analyses leading to the 1973 <br />DPR, and such seepage waters were anticipated to be recoverable down- <br />stream. Recent studies cond~c~ed by the Colorado District Office of <br />the Geological Survey, at the request of the Lower Missouri Region, <br />Bureau of Rec1amati~~llilve indicated that seepage of water from the <br />reservoir should be0..ess than that originally contemplated. The USGS <br />study results are to bl:'p~b1ished in an open-file report during the <br />spring of 1976. <br /> <br />,/ <br /> <br />The earlier estimated seepage rates have been determined to be <br />adequate for use in the current water supply analyses. <br /> <br />PHYSICAL CHANGES IN PLAN <br /> <br />Physical changes which have occurred since the 1973 DPR plan are <br />discussed in this section. The most significant change in the dam is <br />in the spillway design requirements as a result of a revised inflow <br />design flood. Other changes have occurred in plans for railroad and <br />highway relocations and in the recreation and fish and wildlife plans. <br />Wildlife habitat mitigation requirements have increased significantly. <br /> <br />Narrows Dam and Spillway <br /> <br />Narrows Dam, to be located about 7 miles upstream from Fort Morgan, <br />will be an earth embankment structure. The dam will have a maximum <br />structural height above streambed of 147 feet, a length of 22,400 feet, <br />and a crest width of 30 feet. A slurry trench in the right abutment <br />of the dam wi 11 provide a cutoff to control seepage for the safety of <br />the dam. <br /> <br />The maximum reservoir water surface elevation will be 4448.5, and <br />the total controlled capacity will be 973,000 acre-feet at elevation <br />4428.5. The service spillway, with a crest elevation of 4390, will <br />have two 25-foot-wide radial gates proportioned to satisfy flood <br />control release requirements. The auxiliary spillway, with a crest <br />elevation of 4432 and a length of 750 feet, will operate only during <br />major floods. The river outlet works will have a capacity of 3,900 ft3/s <br />at elevation 4399 to provide for normal river releases and for evacuation <br />of the conservation storage pool. <br /> <br />4 <br />