Laserfiche WebLink
JAN-09-O1 TUE 10 41 AM DMG DURANGO FIELD OFFICE FAX NO, 970+247+5104 P, 03 <br />' ' <br />•.~ ... <br />Dickerson Quarry s_~pes Page 2 October 31, 2000 <br />breccia toward the west and south, Figures 9a and 4b are pictures <br />o£ the center of west quarry wall that emphasize the decomposed <br />granite. Fresh granite is exposed in frequent outcrops over the <br />western side of the Dickerson property, as shown on Figures 5a and <br />5b. These outcrops extend eastward from the property line at <br />least 300 feet on the north end to over 500 feet on the south end. <br />Fresh granite is also exposed along the south and southeast sides <br />of the planned quarry. Fresh granite is exposed down the steep <br />souL•h and southeast facing slopes that terminate at U.S. Highway <br />50, <br />Four joint sets were found in the fresh granite in the <br />existing quarry. The two most prominent, i.e. longest trace <br />lengths, joint sets are very steep. One of these two joint sets <br />strikes N54°f: and dips 77°SE. This joint set apparently permits <br />the sL•eep southeast facing road cuts and canyon walls along U.S. <br />Highway 50 southeast of the property. The other strikes N28°E and <br />dips 00°NFI, Soth of these joint sets are too steep to provide a <br />path for potential slope failure at the planned slope angles. <br />These two joint sets further steepen where exposed in the fresh <br />granite outcrops on the west side of the property. The third <br />joint :,et strikes N59°W and dips 61°SW. This joint set can not <br />represent a slope stability hazard to the quarry walls because <br />there will be no southwest facing quarry walls. This joint set, <br />shown on figure 5a, parallels Beaver Creek approximately 250 feet <br />west of the property, indicating its importance to southwest <br />facing natural granite slope angles. The N33°W to N3"o°w striking <br />le.i~ and 20°NE to 38°NE dipping joint set represents a potential slope <br />stability hazard to the planned northeast facing quarry wall in <br />the southwest corner of the quarry. The dip of this joint set is <br />steepest where exposed in the existing quarry and flattest where <br />exposed in the fresh granite outcrop surface on the west side of <br />the property, shown on Figure Sb. <br />PLANNED QUARRY SLOPES <br />The planned 63° (2 vertical to 1 horizontal) overall slope <br />angles will be excavated in 40 £eet high benches. The quarry <br />floor will be ai: elevation 7545 feet, the present quarry floor <br />elevation, with the other benches at 7585 feet, 7625 feet, 7665 <br />feet and 7705 feet. Excavation of the upper bench will lead, <br />followed successively by the lower benches. Temporary haulage <br />ramps will connect the benches to the screening plant, stockpile <br />area and scales. Figure 6 presents the cross section for the <br />initially planned 63° overall slope angle i.n the southwest corner <br />o£ the quarry , including the initially planned slope, the quarry <br />floor, the intermediate benches and the potentially adverse joint <br />set in the worst-case location through the toe of initially <br />planned slope. Figure 1 presents the plan view of the final <br />quarry crest, toe. and intermediate benches, with the recommended <br />