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1lV V <br />~YJ <br />No. 7 and Plate C-1. Improvements to the stilling or impact area should be <br />made to control and limit erosion at the outlet. A suitably graded rip rap <br />zone would probably be adequate, considering the limited flow. <br />The gate control is located about 40 feet from the outlet, and the <br />opening or closiny of the gate consists of turning a shaft in a well 20 + <br />feet deep to the valve (see Pi ate C-I}. At the time of inspection, the <br />valve was in an inoperable condition and could not be opened. There is a <br />definite need for improvement and modification of the outlet r+orks. It is <br />recommended that the owners consider constructing an inlet structure tr+ith a <br />control gate at the inlet with the operating mechanism on the crest of the <br />dam. <br />e. ~SPillwa.. The spillway is illustrated in Ptrotograph No. B. It <br />appears tom to good operating condition. The spillway was operating at <br />the time of the inspection. The spillway cross-section at the crest, as <br />measured in the field, is trapezoidal in shape with a 14 + foot bottom <br />width with 2H:LV side slopes. <br />7. HYDROLOGIC AND HYDRAULIC EVALUATION. <br />The Monument Dam and Reservoir is located in Section 32, Township 13 <br />South, Range 90 West, of the 6th Principal Meridian, in Gunnison County, <br />Colorado. The dam is an irrigation water storage structure. <br />The drainage area, including the reservoir area at high water line, <br />is 5.54 square miles in size as determined by planimetering the area on <br />7-1/2 minute U.S.G.S. quadrangle topographic maps. <br />The only information on file with the State Engineer's Office <br />regarding any hydrological and hydraulic analysis for Monument Reservoir is <br />a study performed in November, 1976, by the State Engineer (see page 1 of <br />Plate D-1) for a low hazard storm. <br />The results of the repeated technical hydrologic and hydraulic analy- <br />ses are summarized in Plates D-1 through D-5 in Appendix D. The area- <br />capacity curves for the reservoir are included in Appendix D as Plate D-6. <br />The curves were generated using the data obtained from the Water <br />Commissioner. Plate D-7 presents some of the computer printout sheets for <br />the hydrograph development and flood routing analysis. Prates D-2, D-3, <br />and D-4 present the Probable Maximum General Storm (PP1G5) and Probable <br />Maximum Thunderstorm (PMTS) rainfal] from "Design of Sztali Dams" and <br />"Hydro-Met Report No. 49", respectively. The maximum rainfall obtained <br />from either source is PMGS (6-hour) = 4.60 inches and PMTS = 6.28 inches. <br />The computed peak flows into the reservoir from a 6-hour PMGS storm <br />extended to 18-hours and a PMTS storm, including the precipitation which <br />falls directly on the reservoir, is 2,340 cfs and 10,493 cfs, respectively. <br />The hydrographs for the 18-hour PMGS and PMTS storms toere routed through <br />the reservoir using an initial starting reservoir level at the spillway <br />crest elevation of 7326.0. The spillway rating, as tabulated on Plate D-5, <br />was based upon the crass-section shown on Plate C-1 as «reasured in the <br />field. When routing both the Ph1G5 and PMTS floods, as indicated above, the <br />dam is overtopped in both instances. <br />• -5- <br />