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of the drain, CONTRACTOR will remove any vegetation and topsoil existing within the <br />underdrain corridor. Salvaged topsoil will be removed to the storage facility identified in Map <br />3, Project Area. <br />(2) Excavation of the underdrain will then begin. The excavation will typically be rectangular <br />in shape, having vertical sides. In the case of constructing an underdrain at a fill location at <br />the Old Refuse Pile, excavation into the pile will be necessary. Excavation will occur for a <br />distance of approximately five to ten feet (5' to 10') . Excavation to ground level is required. <br />Excavation will occur so that the underdrain has a minimum gradient of two percent (2 %). <br />The minimum width of the excavation will be four feet (4') and the minimum depth below <br />native ground surface at the upper most extent of the excavation will three feet (3'). The <br />upper most foot of the excavation will be sloped away from the excavated trench at a slope of <br />not less than 4H:1V until ground level is encountered. See Figure 1, Typical Underdrain . <br />Excavation will continue until the end of the drain is no less than ten feet (10') from the toe of <br />the fill slope. <br />Excavation of an underdrain at the disposal area will be identical to that described above, <br />however, removal of rubbelized concrete or similar materials will be required, rather than <br />excavation of coal refuse. <br />(3) The base of the drain after excavation shall be compacted using a hand held compactor. <br />(4) Upon completion and acceptance of the excavation, a geotextile fabric, such as Mirafi <br />140N or pre- approved equivalent material, will be placed within the excavation. The <br />geotextile shall be placed so that it is not folded or wrinkled. The aggregate shall be carefully <br />placed on the geotextile so as to avoid puncturing the fabric. Aggregate shall fill the trench to <br />its full depth. Upon completion of filling the trench, the ends of the geotextile shall be <br />wrapped over the top of the aggregate, so that the fabric overlaps itself by a minimum of <br />twelve inches (12 "). <br />Durable rock materials, with an average size of no less than three quarters of an inch (3/4 ") <br />and no larger than four inches (4 ") as measured across the shortest axis of any one rock shall <br />be introduced into the excavated drain, so that the drain is filled from top to bottom and side to <br />side for its length. The 4H:1V side slopes of the uppermost one foot do not need to be filled <br />with rock, see Figure 1, Typical Underdrain. Durable rock is defined as competent granitic or <br />metamorphic rocks, excluding slightly metamorphosed sandstones, shales or other friable <br />materials. <br />Measurement and Payment <br />Underdrains will be measured to the nearest linear foot. Payment for this task will be paid for <br />at prices established in Item 7 of the Bid Schedule per linear foot installed. Installation of <br />Underdrains IS NOT guaranteed. Such payment shall be considered full compensation for all <br />labor, materials, equipment and all other items necessary and incidental to the furnishing and <br />placement of the Underdrains as directed and described in the specifications. Payment will be <br />as this task is completed and approved by the PROJECT MANAGER. Payment for this task <br />20 <br />