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<br />II-3 <br /> <br />the Clear Creek alluvial terrace area, such as the Crestview Water and Sani- <br />tation District ponds, Lake Sangraco (Brannan) and the Aloha Beach ponds, <br />were excavated by sand and gravel extraction operations during the late 1950's <br />and early 1960's. Prior to that time, the Clear Creek terrace area was farmed <br />to truck garden or high-value horticulture crops. <br />Hidden Lake appears to be located on the site of a natural pond or swampy <br />area. The dam impounding the water to the present level was originally con- <br />structed during the 1890 decade and is approximately eight to ten feet high. <br />A filing by the Westminster Resort Reservoir and Irrigation Company in 1907 <br />indicated plans to enlarge the reservoir to over 3400 acre-feet of storage <br />with a total dam height of 24 feet. This filing was apparently never imple- <br />mented. A series of drawings setting forth certain improvements to the dam <br />and spillway were filed with the Colorado State Engineer's Office in 1958 and <br />again this work was apparently not completed. The dam, in its present con- <br />figuration, has a nominal crest elevation of 5281.5 feet. A simple broadcrest, <br />uncontrolled spillway is located in the left (north) abutment area. The crest <br />of the spillway is at elevation 5280.5 feet, which provides only one foot of <br />freeboard. A makeshift installation of flashboards or planks have been in- <br />stalled in a contraction joint in the spillway, which raises the potential <br />normal maximum water surface by approximately six inches. The outlet from <br />the reservoir is located adjacent to the spillway and consists of a twelve- <br />inch diameter pipe with an Armco slide gate for control. <br />During late 1974 or early 1975, this outlet was plugged by concrete so <br />the reservoir water surface could not be lowered through this outlet. <br />During the May 5-6, 1973 storm, the dam was overtopped along the right <br />abutment area (southeast corner). Based upon comparison between a survey <br />