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berm which will be 5-8 feet high. The ditch will be a minimum of 1.0 feet deep with 2H:1V sideslopes <br />and will have a maximum grade of 7% to keep erosion of the ditch itself to a minimum. No lining of <br />the ditches will be needed if this grade is maintained. Until mining progresses to the new lease area, <br />the existing sediment pond will be used, as shown on Map C-2. This pond will contain the runoff from <br />the 100 year 24 hour event of 2.4 inches, therefore, no NPDES permit will be needed. Since the gen- <br />eral grade of the terrain is to the southwest, very little berming or ditching is needed on the north and <br />east sides of the site. The existing mining operation has more or less dug a hole in the terrain. <br />When the new lease area is mined, a new sediment pond will be constructed on the southwest corner <br />(lowest point) of the mine area, which will contain the runoff from the 100 year 24 hour event for the <br />combined drainage area of 67.5 acres, therefore, no discharge permit is needed. The drainage area <br />(same as disturbed area) that drains to the pond is shown on Map C-2. It is demonstrated below that <br />the area of the pond is adequate to handle the entire runoff for the 100 year event <br />Area = 67.5 acres <br />Curve number = 82 (Combination of porous gravel, exposed soil, partially reclaimed area and fully <br />reclaimed area) <br />100 year 24 hour rainfall = 2.4 inches <br />Runoff @ CN 82 = 0.92 inches <br />Total volume = 0.92 inches x 1 ft/12 in x 67.5 acres = 5.17 acre-feet or 225,423 cubic feet. <br />Since much of the site area will be flat, some ponding will occur. 10% ponding of the runoff is as- <br />sumed, therefore, the pond needs to hold 202,880 cubic feet. <br />The pond has an average area of 0.92 acres, therefore an average depth of 5.1 feet is needed so that the <br />volume will be entirely stored in the sediment pond. The entire pond will be incised, therefore, 2H:1V <br />sideslopes will be used. This is more than adequate to contain the 100 year event. <br />4. Mine Facilities and Operation <br />The site will consist of a portable crushing and screening plant, portable stacker conveyors, portable <br />asphalt plant, portable concrete plant, truck scale, potential portable office trailer and gen-set porta- <br />ble light fixtures in case some urgent work is needed at night. No night operations are scheduled for <br />Berry Pit 3/02 9 <br />