Laserfiche WebLink
<br />-2- <br /> <br />obtaining large sandstone boulders from the required excavation and using <br />these rocks to construct and line the drainage ditches. We have specifically <br />cove red the items regarding our recommendations for drainage in Item 9 on <br />Page 27 of our report. We refer to Area IIB, however, the same type of <br />recommendations would be applicable should Energy Fuels Corporation <br />elect to use design configuration IIA. <br />Item 5 The question is with respect to the terraces on the slopes <br />of the excess spoil pile. As indicated in our recommendation No. 12 on Page <br />27 of our report, we recommend 2.5:1 (horizontal to vertical) slopes with <br />a 50-foot vertical interval. Item 3 under paragraph 816.102 indicates <br />slopes as steep as 2:1 would be acceptable. We have recommended a slope <br />flatter than allowed by the regulation. The recommended intermediate slope <br />is governed overall by stability considerations. We suggested in our ori- <br />ginal reconunendation minimum bench widths of 30 feet. We used a bench <br />width of 20 feet in the stability analysis, as shown on the drawings - for <br />example Fig. 12. The 30-foot width can be reduced to 20 feet to comply <br />with the OSM regulations with no adverse impact on the stability. In Item 12 <br />we recommended that the benches be sloped to the outslope of the fill at a <br />5 percent grade. This is contrary to OSM regulations. This is a matter of <br />engineering opinion. IJe can accept reversing the slope on the bench so that <br />the 5 percent grade goes from the outslope towards the fill. This type of <br />design results in water ponding at the point of intersection of the bench with <br />• the adjacent fill slope and, in our opinion, increases the risk of water sat- <br />urating the individual benches. We can accept the OSM and MLRB position of <br />a 5 percent grade from the outslope towards the fill. However, we recommend <br />that a drain ditch be provided at the point of intersection a` the bench with <br />the fill to be certain that water which collects on individual benches would <br />then flow to the outside of the fill and collect on surface drain ditches, as <br />recommended in Item 9 and be carried away from the fill areas. Paragraph <br />816.102 requires individual bench stability must exceed a factor of safety <br />of 1.3. On Fig. 14 in our original report, we presented a stability analysis <br />of individual benches with a bench height of 50 feet. As evidenced by <br />Figure 14 our computed factor of safety exceeds 3, which is in excess of the <br />minimum required factor of safety. <br />Memo, Keith Kirk, Mike McCarthy <br />January 2, 1980 <br />Page 3, Item (3) requests that the applicant present a more thorough <br />discussion o e ong-term stability of the pile, as well as the long-term <br />drainage off the permanent stockpile. The drainage off the stockpiles is <br />covered in the discussion which was presented above. However, regarding <br />long-term stability of the pile, we believe our analysis of the stability <br />as summarized in our report, is a very conservative approach. The strength <br />r1 <br />~J <br />