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• <br />-17- <br />1. The portal entry wall should be cut no steeper than 75 <br />degrees. <br />2. The cut slope is based upon a pit cut strike of N66 and the <br />observed joint orientations. If the direction of the cut <br />is altered from that used in our analysis, we should be <br />contacted to review our recommendations. <br />3. We recommend that soils above bedrock be cut at slopes no <br />steeper than 2:1 (horizontal to vertical). The ground surface <br />above the cut crest should be sloped downward away from the <br />crest to provide drainage away from the cut. Overall surface <br />drainage must be planned to preclude ponding of water near <br />the cut crest. <br />4. A bench at least 15 feet in width should be provided near the <br />interface between the brown and gray sandstone layers. The <br />top of the bench should be sloped downward toward the inside <br />of the cut face at least 2 percent. Overall, the bench should <br />be graded to provide for the rapid removal of runoff and to <br />avoid ponding of water on the bench which could result in <br />formation of water in the joints and failure of the entry wall <br />cut. <br />• 5. In our opinion, portal liners should extend beyond the entry <br />face, into the open pit to provide some protection from <br />rockfall. We believe that the liner should extend at least <br />10 feet into the pit. <br />6. The slakeable shales which occur in the lower portions of the <br />highwall can be covered with shotcrete or similar product to <br />reduce the likelihood of local block failure in the rock. <br />This treatment could probably be delayed during the life of <br />the experimental mine unless slaking presents a threat to <br />stability of the entry wail. <br />7. We recommend that the cut be inspected by a representative of <br />our office periodically during construction to confirm that <br />exposed joint orientations are similar to those observed during <br />our field investigation and to check for anomalies which could <br />adversely affect mass stability of the cut. <br />We have been asked to consider both short -term and long -term design <br />lives of the mining operation in our analysis. Considering that mine <br />entries for short -term operations will also be utilized if the operation <br />is expanded to full - scale, we believe that the short -term and long -term <br />