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Placement and Compaction <br />The coal mine waste material is hauled by truck to the disposal area and initially end - <br />dumped in an area for drying. The coal mine waste is worked with dozers and track hoes <br />to assist in the drying process, and when necessary mixed with coverfill material to <br />expedite drying efforts. Mixing of coverfill material with refuse will be managed to ensure <br />the minimum amount of coverfill material required to cover Gob Pile #2 and Gob Pile #4 <br />will be reserved at all times. Appendix A in this volume presents the minimum amount of <br />coverfill material required to cover Gob Pile #2 and #4. <br />Trenches are cut through the end -dumped material to allow better drainage. Berms are <br />constructed in the low areas to collect the water and to keep water from flowing over the <br />outslopes of the pile. Temporary drain pipes are used to convey water that is collected in <br />the low areas to existing stabilized ditches. Water is not allowed to flow over the <br />outslopes of the pile. The pipes only function is to collect water that is draining from the <br />coal mine waste material. The pipes are not an integral part of the surface water control <br />system. <br />The top of gob pile #2 will serve as a drying area for end dumped gob as shown on page <br />14a. Gob will be stacked to a maximum height of 20 feet, with a slope angle up to <br />1.5h:1v. A 25 foot buffer zone on the face of the gob pile will be maintained at all times. <br />Gob will be spread and compacted to the currently approved slope configuration as <br />soon as gob and weather conditions allow. The maximum amount of un -compacted gob <br />in both refuse areas (Gob Pile #2 and Gob Pile #3) will not exceed 425,000 cy total. <br />The coal mine waste is placed and compacted in the active working area after it is <br />sufficiently dried. The top of the pile is sloped to ensure run-off from the fill surface flows <br />to the collection ditches and is not allowed to flow over the outslope of the fill. A berm <br />will be maintained to assure water does not flow over the outslope. <br />Coal mine waste will be placed and compacted to 90 percent of the maximum dry density <br />to prevent spontaneous combustion and to provide the strength required for stability of <br />the refuse pile. Dry densities will be determined in accordance with AASHTO T99-74. <br />The placing and spreading of the coal mine waste will be started at the lowest point of <br />the foundation. The coal mine waste will be keyed into the natural ground. Materials will <br />be spread in approximately horizontal lifts no more than 24 -inches thick, and such lifts <br />made uniformly over long stretches. Each lift will be moistened or dried to a uniform <br />moisture content suitable for maximum compaction. Compaction will be carried to the <br />edge of the fills so that the final slopes are firm. The fill will be shaped and benches <br />(terraces) constructed as shown on Figure 1 and in accordance with the design <br />parameters listed above. <br />TR -98 -13- 01/15 <br />