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r <br />.% <br />,/ <br />precipitation event at all times. The method of determining this volume <br />is to calculate the total runoff and peak flow for the design event and <br />insert these values in the Modified Universal Soil Loss Equation (MUSLE). <br />This method is described in Applied Hydrology and Sedimentology for Dis- <br />turbed Areas (Barfield, Warner and Haan, pp. 365-380). The sediment <br />yield thus derived is the minimum allowable storage volume of the pond <br />and is incorporated in the designs of the Energy Mine No. 3 Detention <br />Basin and the Middle Creek Detention Basin. Please refer to Appendix 6, <br />Sediment Yield Calculations. <br />Small Area Exemptions <br />There are three locations at the Energy Mine No. 3 that will require <br />small area exemptions as provided for under Rule 4.05.2(3). These are: <br />(1) a 2.0 acre area south of County Road 33 containing the Middle Creek <br />Mine Office; (2) a 6.3 acre area west of Ditch H3; and (3) a 16.8 acre <br />area upslope from the Homestead Ditch. Justification for the exemptions <br />and a description of alternative sediment con trot measures follows. <br />The 2.0 acre area contains an office complex and gravel parking lot. <br />The facilities are located on flat slopes which are poorly drained. Ad- <br />jacent to the facilities is the floodplain of Middle Creek. In order to <br />treat the drainage from the disturbed area, a system of diversion <br />ditches, berms and a sedimentation pond would need to be constructed in <br />the floodplain. It is felt that alternative sediment control measures <br />could be utilized on-site to prevent further disturbance of the flood- <br />plain. The drainage from the parking lot will be directed into a small <br />-3- <br />- ~ ..q~''Y'-o <br />