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' no significant potential for planar type failures occurring <br />' within the existing highwall. <br />CONCLUSIONS AND RECOMMENDATIONS <br />' OPERATIONAL SLOPE <br />Although instability of the bench fill below the mine facilities <br />is apparent in the conditions analyzed, this particular <br />instability does not significantly affect the operational <br />conditions because the bench fill does not extend a significant <br />' distance into the operational bench. It is, however, recommended <br />that all structures be located inside the limits of fill at the <br />' crest of the bench fill to prevent any damage to these <br />structures. It is also recommended that surface drainage be <br />prevented insofar as possible from contacting the fill or <br />' highwall slopes, which would create the potential for <br />accelerating slope failure. Although cogditions of the existing <br />' highwall exhibit the potential for failure, due to specific <br />features of the intact rock, and from ravelling of the shales, <br />thereby undermining the sandstone rock, it is expected that the <br />' 15-foot bench constructed above the portal facility will contain <br />minor release of rock debris and reduce the potential for impact <br />' to portal facilities. Detailed discussions of the failure modes <br />within the highwall are found within the Joint Study section of <br />' this report. It is recommended that the 15-foot bench be <br />maintained for the life of the mine, and that periodic removal of <br />debris, which has fallen from the rock face be performed, such <br />' that the 15-foot width is maintained. <br /> <br />' 10 <br />