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• ,Inspection <br />The waste rock disposal area was inspected for stability on a quarterly basis by a <br />qualified engineer. In addition the area was inspected during the following critical <br />periods: removal of all organic material, large boulders and topsoil as previously <br />described, installation of surface drainage systems, placement and compaction of fill <br />materials, and during revegetation. A report was provided to the DRMS by the <br />inspecting engineer within two weeks of the completed inspections. A copy of this report <br />is kept at the mine site. <br />Placement and Compaction <br />The coal mine waste material was hauled by truck to the refuse disposal area <br />where it was spread in maximum lifts of 24 inches and compacted. <br />Compaction of the coal mine waste was performed by the handling and <br />• spreading operation. Special compaction equipment was not required to achieve <br />densities to ensure mass stability, prevent mass movement and prevent formation of <br />voids. The coal mine waste was compacted to attain 90 percent of the maximum dry <br />density to prevent spontaneous combustion and to provide the strength required for <br />stability of the refuse pile. -Dry densities were determined in accordance with AASHTO <br />T99-74. <br />Compaction tests were taken at a frequency and location of not less than one <br />per every other layer, at random locations across the pile. Test locations and results <br />were reported to the Division in the appropriate construction reports. <br />Stability Analysis <br />The stability of any slope is dependent on many factors. Typically the stability of <br />a slope is analyzed by calculating the anticipated gravitational forces that tend to drive <br />the mass of soil downhill and the anticipated internal strength of the soil along the <br />• expected plane of failure that will resist downhill movements. If the driving forces are <br />RN-05 2-18 09/07 <br />