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Page Twelve <br />Preliminary Adsquecy Rev.'.ew <br />GEX - Roadside S Cameo Mines ' <br />April 27, 1981 <br />4.05.3 Diversions and Conveyances of Overland Flow <br />1. Peak Flow Estimates: GEX has used the SCS method described in the manual <br />Peak Flows in Colorado to estimate peak flows. None of the estimates appear <br />to have considered basin shape corrections as described in Appendix E of <br />the manual. Estimates using the Homographs should also include slope cor- <br />rections where the slope is not exactly as stated on the graphs. GEX must: <br />a. show all information necessary to generate the CN's used; <br />i. hydrologic soil group, <br />ii, land use, or <br />iii. cover type and density, <br />b. provide an estimate of average watershed slope; <br />c. provide basin shape and slope corrections where applicable. <br />2. Design Velocities: In several cases, specifically in cast-over ditch <br />designs, the channel geometry is not sufficiently defined to determine area <br />(A) and wetted perimeter (P). These parameters should be shown as functions <br />of depth (d) in order to determine design depth, velocity and freeboard <br />(See Barfield and Haan (1978) page 130-131). Several of the ditches had <br />erosive velocities at design flows. GEX must: <br />a. provide sufficient dimensional detail to completely define the channels; <br />b. show area (A) and wetted perimeter (P) in terms of depth (d); <br />c. provide estimates of velocity at design flows; <br />d. provide information on channel lining necessary to prevent erosion at <br />design velocities (4.05.3(6)(a)); <br />e. show that 0.3 ft. freeboard will exist under design flows (4.05.3 <br />(6) (b)) . <br />4.05.4 Steam Channel Diversions <br />1. North Decline Area Diversion: The stream channel diversion shown in <br />the Sedimentation Plan Exhibit 22 is not described in the text. GEX must <br />provide sufficient information to assure compliance with all sections of <br />Rule 4,05.4. <br />