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r <br /> 1 <br /> samples compacted to 90 % of the Maximum Standard Proctor Den- <br /> sities, are fully applicable for the existing waste pile. <br /> 5. 0 CONSTRUCTION PROCEDURES AND MODIFICATIONS <br /> 5. 1 COAL REFUSE DISPOSAL FACILITY <br /> The existing coal refuse disposal facility was designed and <br /> permitted to be constructed with side slopes 2 (H) : l (V) . The <br /> coal refuse was supposed to be deposited in lifts not exceeding <br /> 12 inches in thickness and compacted to densities that would as- <br /> sure long-term stability. Densities on the order of 90 % of <br /> maximum dry density should generally be achieved. No end-dumping <br /> or pushing the refuse over the crest of the existing pile should <br /> be allowed. <br /> According to the results of our work performed within this <br /> study, it is evident that the coal refuse was deposited in hori- <br /> zontal lifts and compacted according to the original design. <br /> Compactions equal to 100 % of Maximum Dry Density were found <br /> during the investigation. It was observed that the slopes of the <br /> existing facility are steeper than 2(H) : l(V). Such slopes have <br /> to be classified as temporary only. It was also found that <br /> recently, coal refuse was either end-dumped or pushed over the <br /> crest of the existing pile. This resulted in the development of <br /> shallow sloughs, slides and mudflows at the sides of the pile. <br /> To achieve long-term stability and to comply with the speci- <br /> fications and design as included in the Permit Application, we <br /> recommend to flatten slopes exceeding 2 (H) . 1 (V) to the <br /> orginal design slope and to eliminate the end-dumped zones or <br /> zones where the refuse was pushed over the crest. <br /> Flattening of the temporary slopes to the final design slope <br /> of 2 (H) : l (V) can be achieved by pushing the material from the <br /> upper pile portion to its toe. By applying this measure, the end- <br /> dumped material on the surface of temporary slopes will be re- <br /> moved and deposited in the lower parts of the pile. We recommend <br /> to prepare the foundations of the lower part of the pile accord- <br /> ing to M LRD regulastions and according to the specifications pre- <br /> sented in Mid-Continent's Permit Application. The preparation of <br /> the foundation should include keying of the toe of the pile on <br /> steeper slopes, as specified. <br /> When building the outer shell of the refuse facility, the <br /> specifications should be strictly followed with regard to the <br /> placement of the refuse in lifts not exceeding 12 inches in <br /> thickness. Each lift should be compacted by at least three passes <br /> of a crawler tractor . <br />_ 19 <br /> GE0411MW CONSULTING.INC. <br />