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0 Fill Placement CDMG regulations require that spoil be "placed in horizontal lifts in a controlled manner, concurrently compacted as necessary to ensure mass stability." Maximum lift thicknesses are not specified. We understand current plans are to transport spoil by mine trucks or by pushing with a dozer. Lift thicknesses on the order of 4 to 10 feet are anticipated. We believe even thicker lifts can be used, particularly back from the face of fills. Our strength testing showed little correlation between density of the specimen and strength (Fig. C-3). The friction angle was similar, a slight increase in cohesion could be inferred. Since the tests were on finer grained samples, and adequate stability is inferred with a friction angle of 30 degrees and no cohesion, we believe compactive effort is not critical to stability. Very high lift thicknesses on the order of 30 to 100 feet have been used for similar material in northwest Colorado, which resulted in stable fills. •~ We recommend the thinner lifts of 6 to 8 feet, with leveling and compactive effort supplied by dozer or trucks, be utilized within 50 feet of the slope face for excess spoil fills, area fills and contour backfill. Beyond the 50-foot horizontal zone we believe thicker lifts up to 50 to 100 feet with end dumping can be used. Where spoil placement is pertormed by dozing the spoil down to the fill, care should be used to place fill in near horizontal layers and not create fill layers which slope down toward the fill face. This could result in adversely orientated layers of finer spoil which could affect stability. Cover material should be provided per regulation. Inspection of the fill placement should be performed quarterly as required by regulations to observe and document stripping, drain construction, fill placement, stability and surtace drainage conditions. • LORENCITO COAL COMPANY, LLC LORENCITO SURFACE MINE -PHASE I CTLR 32, 671 17