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• C3.1, Q~4.95, H=1' ~ I. 4.95 3.1 (L) L 1.6' make L ~ 2' At critical flow, this spillway has enough freeboard. Not having seen the area, I would suggest the spillway placement be fiend determined when the pond is constructed. It should be placed so that it~ will easily drain, probably in the north or northwest portions of the pond. Ifi there is an existing channel that is a continuation of the channel which~is proposed to be diverted, this may be the place into which to channelize the spillway. An access road will block the pond drainage from the spillway and some consideration should be given to how this drainage will get across the road (either a culvert or a drainage Swale). i 3. The operator should install some type of measuring device to indicate the level at which the pond needs to be cleaned. This does not have to be anything sophisticated, a simple iron rod with a line painted on it will work. Where will the accumulated sediment be dumped? It must be disposed of within the permitted area. 4. Designs for the drainage ditch into the pond were not provided. Following is a design which could be used: • Q (10 years) = 3.53 CFS 5 = 31% A Y-ditch would be the easiest to build, however, velocities in this ditch will be high and a trapezoidal ditch would reduce these velocities somewhat. H = 0.03 Reference: "Handbook of Hydraulics" by King and Drater, Table 1-11. y ,_ . _ :., K = QN/b8/3 S 1/2 .. K' = 0.03 D/b = 0.093 D = 0.186 V = Q/A V = 8.0 FPS Velocities in this channel will be high and depending on the channel characteristics erosion may be a problem and channel protection may be necessary. The Division should inspect the channel upon completion to evaluate channel characteristics and what channel protection is necessary. • 5. An NPDES point source discharge permit should be obtained for the pond from the Colorado Department of Health.