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0 <br />• intervals with slopes slightly exceeding 2.5:1, we do not believe stability will be <br />significantly reduced. Our experience indicates interbench slopes as steep at 2.2:1 <br />can provide stable fills. <br />The vertical interval between benches can also be varied if desired. Bench <br />intervals as high as 100 feet may be possible. To increase the bench interval the <br />effects of erosion will be a primary concern. Interbench slope angles may need to <br />be flattened to maintain the average slope face near 3:1 (H:V) overall. <br />The spoil is anticipated to be primarily shale (75 to 90 percent). When excess <br />spoil is generated it should be evaluated to determine engineering properties to <br />confirm strength assumptions and also to evaluate the susceptibility to degradation <br />with wetting and estimate settlement characteristics. Recommendations for sloping <br />of benches and crowning of the top of the fill are shown on Figs. 2 and 3. <br />Site Preparation <br />• <br />Stripping of topsoil and organic material within the fill area is required by <br />regulations and is recommended. Benching of the ground surface is not anticipated <br />to be required. However, it would be more favorable from a stability standpoint to <br />perform stripping operations parallel to the fill outslope. <br />If reconnaissance indicates localized unstable areas which could affect <br />stability, the best procedure may be excavation of the unstable mass. If a localized <br />steep valley side slope results in classification as a valley fill this could require the <br />large drains associated with valley fill regulations. It may be advantageous to cut <br />these slopes to less than 20 degrees to remove the valley classification. This will <br />need to be discussed with CDMG and drain costs estimated to determine if removal <br />is cost effective. <br />The fills will be constructed from above, with spoil trucked or dozed down to <br />• the fill surface. The surface mining should cut off surface water drainage from above <br />LOPENOITO COAL COMPANY <br />cTUr ss,zsi 11 <br />