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material types encountered, the applicant's consultant has developed <br />recommendations regarding the maximum stable cut slope gradients for each <br />characteristic material type (see Table 2.2-2 of the application). The <br />consultant's methodology is sound in this analysis. <br />Geo-Hydro's report contains the statement, "If our recommendations are <br />accepted, the cuts will probably be stable for the lifetime of the mine; <br />sloughing will have to be expected and maintenance of the road will be <br />required." The applicant's consultant has determined those cut slope <br />gradients which should be stable during the operational life of the mine. <br />In other words, the consultant has deduced what cut slope gradients for <br />each characteristic solid or bedrock type encountered will assure a cut <br />slope with a static slope safety factor which exceeds 1.0. The <br />applicant's consultant did complete a mathematical stability analysis of <br />the cut slopes or fill embankments proposed to accommodate the enlarged <br />haul road. <br />Rule 4.03.1(3)(d)(ix) requires that no haul road fill embankment exceed a <br />slope of 2:1 (horizontal to vertical) unless the applicant demonstrates <br />that the steeper proposed embankment will be stable. All fill embankments <br />proposed within the application are specified as having slopes of 2:1 and <br />are, therefore, in compliance with the permanent regulations. <br />Rule 4.03.1(3)(c)(i) requires that no haul road cut slope exceed a slope <br />of 1.5:1 (horizontal to vertical) in unconsolidated materials or a slope <br />of 1/4:1 (horizontal to vertical) in competent rock. Rule 4.03.1(3)(c>(i) <br />does, however, allow for slopes in excess of the stated maximums. The <br />rule states, "except that steeper slopes may be specifically authorized <br />by the Division if geo-technical analysis demonstrates that a minimum <br />safety factor of 1.5 can be maintained or if geo-technical analysis <br />demonstrates that a safety factor less than 1.5 will not result in <br />significant environmental harm or harm to the public health and safety." <br />Close scrutiny of the applicant's proposed alignment and grading of the <br />haul road corridor has determined that the cut slopes proposed at various <br />locations between the design survey stations listed below exceed the <br />allowed maximum slope gradients for cut slopes constructed in <br />unconsolidated materials (see Figures 2.2-16> through 2.2-3). <br />Station 72+70' <br />Station 82+25' <br />Station 85+75' <br />Station 88+40' <br />Station 95+00' <br />Station 101-00' <br />through 75+50' <br />through 83+60' <br />through 87+25' <br />through 95+00' <br />through 101+00' <br />through 104+30' <br />The geological mapping included within Exhibit 0 and the report prepared <br />by Geo-Hydro Consultants, Inc. indicated that each of the above-listed <br />cut slopes will be excavated in materials which were mapped on <br />unconsolidated soils. (See geo-technical map, sheets 1,2 and 3, Exhibit <br />0 of the application.) The applicant proposes to excavate these soils to <br />finish slopes of roughly 1:1 (horizontal to vertical). Slope heights <br />will reach 135 feet. Slopes which exceed 60 feet in vertical height are <br />designed with a 15-foot-wide intermediate terrace bench, which will <br />result in overall slope gradients between 1.1:1 and 1.2:1 (horizontal to <br />vertical) for the affected cut slopes. <br />-16- <br />