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• Placement and Compaction <br />State regulations for compaction of coal waste require spreading in layers no <br />more than 24 inches thick and compaction to at least 90 percent of the maximum dry <br />density per AASHTO T 99-74. Variations are allowed with approval of the MSHA <br />District Manager. <br />In our previous investigation we developed preliminary recommendations for <br />an uncompacted zone within the pile. The uncompacted zone was located a <br />minimum distance behind the face of the pile. The configuration of the revised ROA <br />is comparatively narrow and uncompacted zones of significant size do not exist. <br />Based upon the planned configuration we recommend all coal waste within the <br />revised RDA be placed in lifts and compacted. <br />• It is possible that thicker lifts can be used depending on the placement <br />process and equipment utilized. We believe the well-graded granular nature of the <br />^ coal waste enhancesthe possibility that adequate compaction can be achieved using <br />. ~•I lifts thicker than 24 inches. Heavy, vibratory compaction equipment may be required <br />\' ` _ to achieve compaction for lifts thicker than 24 inches. This should be confirmed with <br />~Q~\ Qi field testing during construction. <br />~ ~ It should be possible to stockpile uncompacted material on the waste pile <br />~~ during periods of inclement weather when spreading and compaction may be limited <br />~S ~ by snow or low temperature. Temporary stockpiles less than 25 feet in height can <br />~ 6~ be placed loose wkh slopes at the natural angle of repose. Temporary stockpiles <br />greater than about 25 feet in height should be laid back at a slope of 3:1 (H:V). <br /> <br />When conditions permit, the temporary stockpiles should be spread in lifts and <br />• compacted as discussed above. <br />22 <br /> <br />