Laserfiche WebLink
ai • • <br />ti <br />Cyprus Orchard Valley Mine <br />Page 2 <br />February 26, 1990 <br />DEN18343.A0 <br />Recommended cut slopes and bench configurations have not been based on any <br />stability analyses; they aze based on our experience with similar cut slopes in the <br />area of the Orchard Valley mine. As discussed in our original report, further <br />stability problems in the West Portal area cannot be ruled out. Because of the <br />upcoming spring season, we feel that any additional excavations or cut <br />modifications of this cut should be delayed after the 1990 spring and summer <br />season; this season will be critical for the cut stability. It will be evident whether <br />the present cut configuration is sufficient or whether additional stabilizing <br />measures will be required. <br />Lining of the upper bench below the topsoil area by an impermeable plastic <br />liner would increase the cut stability during the period of the snowmelt and early <br />spring precipitation; we recommend such a mitigative measure. <br />We would also appreciate the opportunity to inspect this cut if any signs of <br />instability are detected during the spring; such inspection might contribute to <br />identifying the reasons for the cut failures. We understand that MLRD <br />representatives are concerned with the possibility that groundwater contributes to <br />the cut instability; if this is verified by an early inspection, different stabilizing <br />measures might be implemented to increase the stability of the area. <br />We hope that these recommendations are sufficient for you and for the Mined <br />Land Reclamation Division at this time. Please call if you have any additional <br />questions. <br />Yours truly, <br />CH2M HILL <br />Michal Bukovansky <br />Senior Engineering Geologist <br />DEN/24C/242.50/amt <br />