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<br />r <br /> <br /> <br />Figure 6,--The remains of the outlet valve from Lawn Lake dam. <br />Investigations of this valve led to the conclusion that lead <br />caulking had severely deteriorated. <br /> <br />Cascade Lake Dam <br /> <br />Cascade Lake dam, a concrete gravity dam, was located on the Fall River <br />in Rocky Mountain National Park,S. 3 mi west of Estes Park (fig. 1). A <br />diversion dam was originally constructed at the site in 1908 for a pipeline to <br />a hydropowerplant downstream, The powerplant supplied electricity to the <br />Stanley Hotel and the town of Estes Park. The site was at the head of a steep <br />drop with numerous rapids and large boulders in the Fall River, where the <br />stream eroded through several Pleistocene terminal moraines that dammed the <br />Fall River, creating a glacial lake in Horseshoe Park just upstream, The dam <br />consisted of a concrete wall several feet thick, reinforced with a masonry <br />rock buttress on the downstream side. The foundation and abutments were in <br />glacial terminal-moraine sediments; no bedrock is evident in the foundation. <br />A photograph at Cascade Lake dam is shown in figure 8. <br /> <br />The dam was acquired in 1945 by the town of Estes Park, which owned it at <br />the time of failure. Various improvements were made on the structure. It was <br />enlarged to 17 ft high in 1923, The reservoir behind the dam was dredged at <br />least twice since 1945, most recently in November 1981. Postfailure surveys <br />indicated that the water behind Cascade Lake dam was approximately 12 ft deep, <br />and the dam was 143 ft long prior to failure. Because' of the sediment accumu- <br />1 at i on of 5 ft, a hei ght of the dam of 12 ft was used for ana lys is of the <br />flood hydraul i cs. Postflood surveys i ndi cated the capaci ty of the dam was <br />12.1 acre-ft, corresponding to the top of the dam. <br /> <br />13 <br />