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<br />.... Water Supply and Storage Company <br />Page 3 <br /> <br />consideration in the design of the entire facility which was approved by all agencies of <br />interest. <br /> <br />As part of establishing the overall negotiated .planning and design crltena, the invert <br />(bottom) of the outlet works was set high at elevation 10,059 feet so as to create a <br />permanent recreational pool which would never be emptied. The recreational pool rises up <br />29 feet above the former outlet works of the old dam. Then, even when the. new Long <br />Draw Reservoir is "completely drained," there remains in the reservoir a permanent pool <br />with a water depth of 29 feet, a surface water area of about 84 acres, and approximately 685 <br />acre-feet of water. <br /> <br />EMBANKMENT DESIGN <br /> <br />Long Draw Dam construction in 1973 and 1974 was to enlarge the former dam built in 1931. <br />The old dam embankment had been built without modern-day geotechnical control and with <br />primitive equipment, and therefore the dam had moderate seepage characteristics of dam <br />structures common in those days. <br /> <br />The . new dam design incorporated the old embankment in its entirety as reco=ended by <br />the embankment geotechnical engineer, Woodward-Clyde and Associates. To account for <br />seepage control and dam safety needs, the new embankment included a specially-connected <br />chimney drain which collects seepage water and carries it safely to the dam toe drain for <br />discharge into Long Draw Creek downstream of the dam toe (Figure 3). The old outlet <br />works conduit was fIlled with permeable material with a direct connection to the toe drain. <br /> <br />Even under "empty" reservoir conditions, Long Draw Reservoir contains a depth of 29 feet <br />of water against the dam structure which ensures a continuous moderate seepage water <br />supply year around to Long Draw Creek (a/kJa La Poudre Pass Creek) downstream of the <br />dam structure. <br /> <br />BASIN HYDROLOGY <br /> <br />Dam safety considerations included provisions for m:!":!ging the design flood. A bathtub <br />spillway was selected having a surcharge of 3.25 feet over the top of the spillway crest. In' <br />addition, 6 feet of freeboard were built into the dam structure as an added safety feature <br />to avoid dam overtopping and failure risks at this remote location taking into consideration <br />the large (approximately 11,000 acre-feet) volume of water behind the dam which would <br />cause a great flood if the dam were to fail. As designed and constructed, Long Draw Dam <br />is completely safe and free of regulatory restrictions. <br />