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forwarded to you as soon as possible. See Adequacy Review 5 dated December 4, <br /> 2018. <br /> d. DRMS Response 5: DRMS is concerned about the potential for a massive block <br /> failure in the surface quarry. Table 1 in the analysis submitted indicates there is a <br /> principle joint set striking essentially eat-west through the site with a dip angle <br /> 75' to the south. Our understanding is the highwall in the quarry will generally <br /> trend east-west as well, with 30-foot near vertical intra-bench highwalls. If this <br /> principle joint set were to daylight new the toe of one of the intra-bench <br /> highwalls, the potential for a massive block failure seems likely. Please provide a <br /> cross-section showing the local geologic structures and how the intra-bench <br /> highwalls will be designed and constructed to control and mitigate a massive <br /> block failure. <br /> e. GLA Response 4/5: To mitigate potential mass rock movement along the above <br /> detailed 75' south dipping fracture, the batter angle will be pushed to 70°, see the <br /> below Figure 1 cross-section. Any fractures within the pit wall cannot daylight <br /> and allow a massive block failure. The dashed green line represents a hypothetical <br /> 75' fracture—notice how rock mass above the intersection of the fracture and the <br /> face will be cleared as the final 70' batter angle is realized. Rock mass below the <br /> intersection of the fracture and the face will not experience movement as the rock <br /> mass will be contained in the catch bench. If the 75' fracture occurs along a catch <br /> bench, no failure will occur as the fracture will be constrained within the catch ' <br /> bench unable to daylight. By changing the batter angle to 70' the previously <br /> proposed 30 foot catch bench will now have a length of—19 feet. This length will <br /> be more than adequate to account for mining equipment traffic. Additionally, best <br /> management practices will be utilized during every phase of surface excavation <br /> including but not limited to: highwall scaling, erection of safety berms, and <br /> potential closure of hazard areas until the hazard can be fully mitigated. <br /> 5 <br />