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<br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br /> <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br /> <br />INTRODUCTION <br /> <br />Hourglass Dam is an earth embankment wtth a ma>cimum height of 45 feet and a crest lenglh of about <br />2,400 feet. The crest elevation Is 9,372 feet above sea level (40 gage). The dam Impounds 1,693 acre- <br />feet of storage at an elevation of 9.366.5 feet (34.5 gage). <br /> <br />The dam Is located in Larimer County on a small tributary to Beaver Creek some nine miles south of <br />Rustic, Colorado. Most of the reservoir Inflow is supplied from Comanche Dam through a feeder canal. <br /> <br />The dam was originally constructed about 1898 and was enlarged about 1901. Reservoir use was <br />reduced and finally abandoned In Ihe late 1940's because of outlet works deterioration, Rehabllltalion <br />plans were drawn up in 1965 and the following Improvemenls were made in 1966, <br /> <br />1, The existing outlet was removed and replaced by a 33-inch reinforced concrete outlet conduit <br />controlled by two parallel upstream control gates. A downstream stilling basin was provided. <br /> <br />2. Parts of the dam were reshaped and the crest was raised to a uniform level, <br /> <br />3. Riprap was provided al Ihe upslream face of the maximum dam section, <br /> <br />4. A primary side channel spillway was provided In the inlet channel wtth tts crest at elevation <br />9,366,5 (34,5 gage). <br /> <br />5, A secondary emergency spillway was provided a the right side of the dam wtth tts crest at <br />elevation 9.367.2 (35,2 gage). <br /> <br />Excessive seepage developed at the downstream toe of the dam adjacent to the slilling basin when the <br />reservoir was filled, The outlet was then extended about 72 feet downstream, the downstream dam <br />slope was flattened and the stilling basin was reconstructed, Excessive seepage persisted at high <br />reservoir levels following those improvemenls and the State Engineer's Office restricted storage levels <br />In the reservoir In the 1970's, <br /> <br />Runoff from a severe thunderstorm in August 1985 ran down the downslream face of the dam al the <br />left groin, The deep gully caused by this flow erosion extended from the top of the dam to tts <br />downstream toe, Seepage was observed entering the gully from the left abutment. The erosion was <br />promptly backfilled, The dam performed satisfaclorily at the post reconstruclion reservoir Iimtt elevation <br />