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Case F - Existing conservation easement to the west. A property owner <br />agreement that authorizes GP to mine within 200 feet of the conservation <br />easement has been obtained, and has been provided to the DRMS. This case has <br />been analyzed to assure GP that the mining slope/setback will provide adequate <br />protection for the conservation easement. The mining operation is adjacent to an <br />existing conservation easement in this area. The proposed setback for mining is 90 feet <br />from the boundary of the easement. The mining depth was assumed to be 71 feet in this <br />area based on bore log information in the JAC report. The mining side slope in this <br />location will be vertical. <br />Case G - Existing wetland area to the north. Although the wetland is not a <br />permanent, valuable man-made structure this case has been analyzed to assure <br />GP that the mining slope/setback will provide adequate protection for the wetland. <br />The mining operation is adjacent to an existing wetland area in this area. The proposed <br />setback for mining is 40 feet from the proposed permit boundary, 60 feet from the <br />property boundary, and 97 feet from the edge of the existing wetland area. The mining <br />depth was assumed to be 68 feet in this area based on bore log information in the JAC <br />report. The mining side slope in this location will be vertical. <br />The cross-sections located in Appendix B show the proposed mining slope geometry, estimated <br />phreatic surface, location of the man made structures relative to the mining slope, and location <br />of the most critical slope failure surface for each case. <br />V - METHODOLOGY <br />The mining embankment configuration shown in the computer analysis represents the estimated <br />conditions for this site. If mining conditions differ from the estimated conditions, the slope <br />stability will need to be re-evaluated on a case by case basis. The Bishop Method was used in <br />the computer analysis for determining safety factors. The procedure searches for circular shear <br />failures and automatically searches for the lowest safety factor. 9,000 separate failure surfaces <br />were analyzed for each case. The required minimum safety factors are based on the current <br />standards used by the Colorado State Engineer's Office (SEO) in evaluating embankment <br />dams, and industry accepted standards for the evaluation of temporary structures during <br />construction. <br />' West Farm Gravel Pit <br />Slope Stability Analysis <br />Page 3