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• -i8- <br />considerations are the same. The only variable may be the extent of the <br />pit in which the highwall is prepared. It may be viable to prepare the <br />entry face primarily within the area of the experimental entries. If <br />it is later determined that the mining operation is economically attrac- <br />tive, then the remaining portion of the pit could be prepared. <br />The entry face prepared for the initial operation should, in our <br />opinion, extend beyond the immediate limits of the experimental entries. <br />The distance which the prepared face should extend should be determined <br />considering the effect future blasting will have on the experimental <br />entries and other facilities previously constructed within the pit. <br />SPOIL SLOPE EVALUATION <br />• The geometry, subsurface conditions, and the strength of materials must <br />be defined to evaluate stability of the existing spoil. We have been provided <br />with topography of the general pit area as it currently exists. Based upon <br />topography provided and our observations we believe that there are three <br />basic slope configurations within the pit. The three configurations can be <br />seen at Sta. 0 +00, Sta. 6 +00, and Sta. 10 +00. The configurations at Sta. D +00 <br />and Sta. 6 +00 are relatively similar essentially consisting of about 80 -foot <br />high spoil banks which appear to be at the angle of repose (34 to 37 degrees). <br />At Sta. 0 +00 the base of the slope flattens near mid - height to about 26 <br />degrees. At Sta. 10 +00 the slope is separated by a 100± foot wide bench which <br />occurs about 40 feet above the toe of the spoil. It appears that the "bench" <br />was created by preliminary grading of the spoil and is not the result of past <br />slope failure. Cross - sections at Sta. 0 +00 and Sta. 6 +00 are typical of <br />r 1 <br />LJ <br />