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Slope Evaluation and Remediation <br />West Elk Mine <br />Somerset, Colorado <br />Standard recommendations that likely will be generally applicable can be found in <br />Section 203 of the current CDOT Standard Specifications for Road and Bridge <br />Construction (2005). Coarse fragments should spaced widely enough to allow <br />compaction of the finer materials between them. Nesting of coarse fragments should not <br />be permitted. <br />Fill Placement and Compaction Prior to filling, the top 8 to 12 inches of in -place <br />materials on surfaces on which fill soils will be placed should be scarified, moisture <br />conditioned and properly compacted in accordance with the recommendations below to <br />provide a uniform base for fill placement. <br />If surfaces to receive fill expose loose, wet, soft or otherwise deleterious material, <br />additional material should be excavated, or other measures taken, to establish a firm <br />platform for filling. The surfaces to receive fill must be effectively stable prior to <br />placement of fill. <br />Fill materials should be thoroughly mixed to achieve a uniform moisture content, placed <br />in uniform lifts not exceeding 8 inches in loose thickness, and properly compacted. All <br />soils comprising the buttress fill should be compacted to 96 or more percent of <br />the maximum Proctor dry density at moisture contents within 2 percent of <br />optimum moisture content as determined by ASTM D1557, the "modified Proctor." <br />No fill materials should be placed, worked, rolled while they are frozen, thawing, or <br />during poor /inclement weather conditions. <br />Compaction areas should be kept separate, and no lift should be covered by another <br />until relative compaction and moisture content within the recommended ranges are <br />obtained. <br />To achieve adequate compaction near the outer faces of the buttress fill, it may be <br />beneficial to over -build the slopes and trim them back. <br />Settlements Settlements will occur in filled ground, typically on the order of 1 to 2 <br />percent of the fill depth. For a 20 -foot fill, for example, this corresponds to settlement on <br />the order of 3'/2 inches. If fill placement is performed properly and is tightly controlled, in <br />GROUND's experience the majority of that settlement (e.g., 60 to 80 percent) will take <br />Job No. 11 -6014 GROUND Engineering Consultants, Inc. Page 11 <br />