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_ A small ditch should be cut from the toe of the coal mine waste bank to discharge to the west <br />of the sediment pond, as shown in the Drawings. Cut at a 2 percent grade, this ditch will <br />divert runoff from the western side of the sediment pond. Side slopes for this ditch should <br />be 1:1, with a 1 foot depth. Flow rates should be very small in this ditch, so riprap for scour <br />prevention is not required. <br />Filter material required for the runoff control ditches can be replaced by a non-woven geofabric <br />where ditch grades are 10 percent or less. Geofabric is not recommended for side ditches on <br />steep grades. The geofabric should be durable and puncture resistant for placing large <br />diameter riprap. It is suggested that the minimum weight be 12 to 14 ounce per square yard, <br />with an apparent opening size lAOS) no larger than 0.1 millimeter to provide proper filter <br />properties. <br />4.1.6 Material Balance <br />A material balance was performed to calculate the quantities of topsoil and cover material that <br />will be required at the site to place four feet of cover for reclamation as required by Rule <br />4.10.415). An existing coal mine waste bank still in use at the site will be phased out and <br />• reclaimed as part of its closure. The excess cut volumes obtained from the construction of <br />the haul roads for the proposed coal mine waste bank will be taken directly to the existing <br />waste bank for cover fill. This volume amounts to approximately 7,341 cubic yards (cyl. <br />Material used as cover fill for the proposed waste bank will be obtained from excavations of <br />undisturbed soil directly above the advancing. Through the borehole investigation, it was <br />determined that enough unconsolidated material is available near the ground surface for the <br />excavation. As the proposed coal mine waste bank is constructed, after every ten toot lift of <br />coal mine waste is placed, approximately 4 feet of unconsolidated material on the ground <br />surface will then be excavated at the back of the crest where the topsoil had been removed. <br />The height of the excavation will be approximately 10 feet, and will probably be the length of <br />the crest/natural ground contact. As the material is being excavated, it will be placed directly <br />on the exposed 10 feet of freshly placed coal mine waste. The topsoil above the excavated <br />cover fill will be placed on a lower covered 10-foot lift on the side slope to complete <br />reclamation. Thereby, the proposed waste bank will be contemporaneously reclaimed in 10- <br />foot increments. Additional cover and topsoil that will be required to complete the reclamation <br />of the crest and haul roads will be obtained from the initial excavations in the draw (stored in <br />• <br />96256/1424.RPT Coel Mine Weete Benk Design for the Sanborn Creek Mine <br />October 1998 WESTEC, Inc. t2 <br />