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with Rule 4.05.6(8)(h). The pond will provide more than 95X <br />• removal of sediment larger than 0.05 mm in size. The pond <br />will be sized to store the runoff from a 10 year, 24 hour, <br />precipitation event plus the estimated sediment yield over a <br />2-year period. <br />Construction of the sediment pond will be supervised, in- <br />spected and certified after construction by a registered <br />professional engineer. Certification of the constructed pond <br />will be forwarded to the CMLRD upon completion of the pond. <br />The runoff volume and peak discharges for the laydown area <br />were determined using TR-55. The laydown area consists of <br />the following subareas with curve numbers indicated: <br /> <br />Area Designation Acreage Curve Number <br />Disturbed area 5.5 88 <br />Undisturbed area 1.4 70 <br />Total Area 6.9 84 <br />The disturbed area curve number was obtained from OSM (1981) for <br />active mining disturbed area with hydrologic soil group C. The <br />curve number of 70 is for woods in good condition also with <br />hydrologic soil group C. <br />Runoff volume expected from a 10 year, 24 hour event is deter- <br />mined as follows: <br />10 year, 24 hour rainfall <br />Curve number <br />Runoff volume {Q) <br />Q (10 yr., 24 hr. event) <br />Q <br /> <br />= 1.8 inches <br />= 84 <br />= 0.61 tnch <br />= 0.35 acre ft. <br />= 15,279 ft.3 <br />D-5 <br />