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West Ridge Permanent Impoundment <br />October, 1991 <br />Page 2 <br />• <br />Spillway Dimensions <br />Principal Spillway - <br />The purpose of having a principal spillway for this impoundment is to retain flood storage <br />capacity. The existing principal spillway in the West Ridge sediment pond will be retained with <br />its present specifications. Major assumptions and the results of flood routing aze summarized <br />below (all elevations are relative). <br />Crest Elevation 9.0 feet <br />Spillway Type Trickle Tube <br />Straight Barrel Diameter 36 inches <br />Barrel Length 52 feet <br />Initial Pool Elevation 9.0 feet <br />Maximum Pool Elevation 12.6 feet <br />Emergency Spillway - <br />The emergency spillway of the sediment pond will be retained at its present specifications. The <br />channel bottom and side slopes of the emergency spillway will be maintained with rip-rap to <br />ensure erosion control. Major assumptions and the results of flood routing for the emergency <br />spillway design flood aze summarized below (all elevations are relative). <br />• <br />Crest Elevation 12.0 feet <br />Spillway Type Open Channel <br />Width 30 feet <br />Spillway Side Slopes 1.2h:1v <br />Crest Length 20 feet <br />Initial Pool Elevation 9.0 feet <br />Maximum Pool Elevation 12.6 feet <br />Maximum L?ischazge (1° & 2~ 68.38 cfs <br />Top of Dam Elevation <br />The top of dam elevation will be 14.0 feet. The emergency spillway crest elevation of 12.0 feet <br />plus 0.6 feet of peak flow depth minus the top of dam elevation of 12.0 feet equals 1.4 feet of <br />freeboard. This is sufficient freeboazd to resist over topping by waves. <br />Inspection Procedures <br />A qualified registered professional engineer, or a qualified person under his direction, shall inspect <br />the impoundment. Inspections shall be made at least yearly until release of the performance bond. <br />The qualified registered professional engineer shall promptly, after the yearly inspection, provide to <br />the Colorado Mined Land Reclamation Division (CMLRD) a certified report that the impoundment <br />has been maintained as designed and in accordance with the approved plan. <br />App. 4.6-N-2 <br />September 7, 1993 <br />