Laserfiche WebLink
2. Slope Stability Analysis <br /> A slope stability analysis was performed using GALENA Slope Stability Software, assuming the <br /> ground conditions described in the DRMS permit.The model assumes an average 2.5 feet of <br /> overburden and topsoil overlying a 25-foot-thick sand and gravel deposit for a total mining depth of <br /> -r27 feet. Also included in the model is the groundwater table at 4 feet below the surface, <br /> intercepted by a slurry wall. The materials used in the slope stability analysis are sand and gravel - <br /> mixed grain size for the aggregate deposit, and loose sand - mixed grain size for the overburden <br /> and topsoil. The material properties for these two materials are shown in Table 2 below. <br /> Table 2— Material Properties <br /> Aggregate Deposit Overburden and Topsoi <br /> Description_ sand and gravel, r n <br /> mixed rain size size <br /> Unit Weight(Ibs/ft3) 110 99 <br /> Friction'Angle (°) 45 34 <br /> Cohesion 0 0 <br /> *Material information is from the SME Mining Reference Handbook(2002 Edition)' <br /> Using these conditions, the failure slopes for the active mining, final mining, and reclaimed slopes <br /> were determined using Bishop's Method of Slices to identify the circular failure at various factors of <br /> safety (FOS). The inputs and results of this analysis are depicted in the attached Slope Stability <br /> Analysis Map and summarized in Table 3. More information on each slope condition is provided <br /> below. <br /> Table 3—Slope Stability Analysis Results <br /> Active Slope Lowest FOS = 1.5 Slope Distance to Sufficiency <br /> SlopeStatus <br /> FOS from Mining Crest (ft) Structure (ft) <br /> Active`,Mining ` Vertical ✓ 0.726' 27:$ 2.85 No <br /> Final Mining 2H:1V 1.39 6.33 18.6 Yes <br /> Reclaimed 314:1V 2.04 -- 48.0 Yes <br /> Table 2.5; Originally from Houk and Bray, 1977 <br /> Wattenberg West Slope <br /> Stability 3 ®Lcwicki&Associates <br /> May 2022 <br />