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• Placement and Compaction <br />The coal mine waste material will be hauled by truck to the refuse disposal area where it will be <br />spread in maximum lifts of 24 inches and compacted. The top of the pile will be sloped to the <br />east and west to ensure run-off from the fill surface flows to the collection ditches and is not <br />allowed to flow over the outslope of the fill. A berm will be maintained to assure water does not <br />flow over the outslope. <br />Coal mine waste will be placed and compacted to 90 percent of the maximum dry density to <br />prevent spontaneous combustion and to provide the strength required for stability of the refuse <br />pile. Dry densities will be determined in accordance with AASHTO T99-74. The placing and <br />spreading of the coal mine waste will be started at the lowest point of the foundation. The coal <br />mine waste will be keyed into the natural ground. Materials will be spread in approximately <br />horizontal lifts no more than 24-inches thick, and such lifts made uniformly over long stretches. <br />Each lift will be moistened or dried to a uniform moisture content suitable for maximum <br />compaction. Compaction will be carried to the edge of the fills so that the final slopes are firm. <br />The fill will be shaped and benches (terraces) constructed as shown on Figure 1 and in <br />accordance with the design parameters listed above. <br />Compaction tests will be taken at a frequency and location of not less than one per every other <br />layer, at random locations across the pile. On average, when coal mine waste is being placed, <br />compaction testing occurs weekly. Test locations and results will be reported to the Division in the <br />is appropriate construction reports. <br />Coal mine waste materials from activities located outside of the permit area, such as those <br />activities at other mines or abandoned waste piles, will not be placed in the coal mine waste bank <br />unless approved by the Division. <br />In accordance with Buckhorn Geotech recommendations regarding taking the 5:1 gob slopes to <br />3:1 slopes, all topsoil previously placed must be removed and stockpiled for later use. <br />Placement of additional coal waste shall commence from the bottom and proceed up the slope. <br />Additional coal waste must be keyed or benched into the existing (previously placed) coal waste. <br />The vertical cut for each key into the coal waste should be on the order of 4 to 6 feet high. Keying <br />the additional coal mine waste into the existing waste will eliminate a potentially weak surface <br />along the previous and newly places waste. If any zones of seepage are encountered during the <br />benching/keying operations, we recommend construction of a gravel drain to allow drainage and <br />relieve pore pressures. Care should be taken during fill placement, keying and benching to not <br />damage the vibrating wire piezometers and inclinometers installed at CWDA. The piezometers <br />have cables that are routed through the coal waste to the bench located 50 feet above the toe of <br />the waste bank. <br />• <br />TR-61 -9- 06/09 <br />Apego1'D <br />6f19/pq