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0 <br />-29- <br />PIT FLOOR CUT <br />We understand that consideration is being given to flattening the pit <br />floor in the area of the underground operation and providing a slight grade <br />- downward from the toe of the entry highwall toward the spoil. This is one <br />alternative being considered to provide for surface drainage away from <br />entries. The pit floor would slope downward in a direction parallel to <br />the pit strike so that overall drainage is directed toward the southwest. <br />A sump would be provided to collect and remove surface water. <br />We analyzed stability of the rock cut using methods similar to those <br />described for analyzation of the entry wall. In contrast to the entry wall, <br />the bedrock bedding dips adverse to the spoil cut. Mlarklin's test indicates <br />• that the cut would be stable at 55 degrees provided the bedrock has a friction <br />angle of at least 30 degrees. Marklin's test is not valid for this cut slope, <br />in our opinion, since it does not consider the effect of the overlying spoil <br />and infiltration of water into vertical tension cracks. <br />Detailed information regarding joint patterns within the rock below the <br />old pit floor was not available to us. Based upon our observations of the <br />overlying rock exposed, and the relative consistency of the occurrence of near - <br />vertical joints, we believe that similar joint patterns exist in the rock under- <br />lying the spoil. Infiltration of water into these joints is probable since <br />there is evidence that water is moving down dip along the old pit floor be- <br />neath the spoil. <br />We analyzed the rock cut for failure based upon a failure mode which <br />includes presence of hydrostatic pressures in vertical joints and sliding of <br />