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Center Ridge Permanent [mpoundment <br />October, 1992 <br />Page 1 <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 Center Ridge sediment pond will be retained <br />Major assumptions and the results of flood routing are summarized below (all elevations are <br />relative). <br />Crest Elevation 23.00 feet <br />Spillway Type Trickle Tube <br />Straight Barrel Diameter 36 inches <br />Barrel Length 25 fat <br />Initial Pool Elevation 23.00 feet <br />Maximum Pool Elevation 27.6 feet <br />Emergency Spillway - <br />The emergency spillway will be a trapezoidal shaped open channel. The channel bottom and <br />side slopes of the emergency spillway will berip-rap to costae erosion control. Major <br />assumptions and the results of flood routing for the emergency spillway design flood are <br />• s~immari~rtt below (all elevations are relative). <br />Crest Elevation 26.7 feet <br />Spillway Type Open Channel <br />Width 30 fat <br />Spillway Side Slopes 2h:ly <br />Crest Length 20 fat <br />Initial Pool Elevation 23.00 feet <br />Maximum Paol Elevation 27.6 feet <br />Maximum Discharge (1° 8c 2aj 100.05 cfs <br />Top of Dam Elevation <br />The settled top of dam elevation will be 28.7 fat The emergency spillway crest elevation of 26.7 <br />feet plus 0.9 feet of peak flow depth minus the top of dam elevation of 28.7 feet equals 1.1 feet of <br />freeboard. This is sufficient freeboard to resist over topping by waves. <br />Inspection Procedures <br />A qualified registered professional engineer, or a qualified person under his dirocdon, 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. 4.6-0-2 <br />September 7, 1993 <br />