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Tegre Corporation <br /> Job No. 3124JS057 <br /> 6.4 Stability Analysis—Proposed Improvements <br /> Detailed information regarding the proposed improvements planned to occur on the site <br /> was not available. It is understood that mining operations will consist of removing the clay <br /> overburden and stockpiling this material on the site, excavating the granular deposits to the <br /> top of bedrock; processing the granular material and trucking the material for use off-site; <br /> and backfilling the excavations with the stockpiled overburden to reclaim the area. <br /> Excavations created to remove material for processing are temporary and were analyzed <br /> based upon the short-term condition. The short-term condition is the case during mining <br /> operations where the side slopes will remain unsupported for less than about 4 months and <br /> the excess pore water pressures do not have time to dissipate. <br /> In areas where the crest of the excavation face will be located at least 1.5 times the <br /> excavation depth away from mine improvements a short-term factor of safety of at least 1.5 <br /> is recommended. The calculated factor of safety will be a function of the soil conditions and <br /> the excavation depth. A summary of the stability analysis for the short-term condition <br /> where excavations will not be located in the area of improvements is presented in the <br /> following table. The results of the stability analysis are presented on Figures C-1 through C-8 <br /> in Appendix C. <br /> TABLE 3 <br /> TEMPORARY EXCAVATIONS AWAY FROM IMPROVEMENTS; <br /> SHORT-TERM CONDITON; F.S. = 1.5 <br /> Maximum Slope Maximum Slope <br /> Excavation Depth Inclination Inclination <br /> (Granular Profile) (Clay/Granular Profile) <br /> 20 feet 1.5H:1V 1H:1V <br /> 40 feet 1.5H:1V 1H:1V <br /> 60 feet 1.5H:1V 1.5H:1V <br /> 80 feet 2H:1V 1.5H:1V <br /> In areas where the crest of the excavation face will be located less than 1.5 times the <br /> excavation depth away from mine improvements a factor of safety of at least 2.0 is <br /> recommended. The calculated factor of safety will be a function of the soil conditions and <br /> the excavation depth. A summary of the stability analysis for the short-term condition <br /> where excavations will be located in the area of improvements is presented in the following <br /> table. The results of the stability analysis are presented on Figures C-9 through C-16 in <br /> Appendix C. <br /> 8 <br />