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M05003MT <br />Our stability analysis was also performed along a similar <br />proposed cross section of the gob pile site, as referenced above, <br />located at or near the maximum height of the proposed gob pile <br />fill. However, the slope face inclination in the lower fifty (50) <br />vertical feet is two and one half to one (2-1/2:1) and the upper <br />slope inclinations were also flattened to determine a, theoretical <br />calculated factor of safety of 1.5 or greater. The stability <br />analysis of these proposed cross sections indicates a theoretical <br />factor of safety ranging from about .87 to about 1.50 depending on <br />the upper slope inclination used. The theoretical calculated <br />factor of safety of 1.50 was associated with an upper slope face <br />inclination of five to one (5:1). The slope stability analysis for <br />the proposed flatter slope inclinations on the gob pile is <br />presented on Figures F, G, H and I. <br />=~ It should be noted that the coal gob strength characteristics are <br />based on limited sampling obtained from the lower limits of the <br />fill embankment. We suggest that additional laboratory strength <br />:~ tests be performed on the coal gob material during placement about <br />every ten (10) feet of gob fill height or about twice, per year, <br />whichever occurs more frequently, to verify that the material <br />_1 characteristics and strength do not vary significantly, with time <br />J and mined material changes. <br />I~ <br />IJ <br />IJ <br />IJ <br />IJ <br />IJ <br /> <br />4.0 POST DESIGN CONSIDERATIONS <br />The project geotechnical engineer should be consulted during <br />construction of the project to observe site conditions during <br />construction and to provide materials testing when needed. <br />This geotechnical engineering study and stability analysis is <br />based on limited sampling; therefore, it is necessary to assume <br />that the gob pile conditions do not vary greatly from those <br />encountered in the field study and laboratory study. Our <br />experience has shown that significant variations are likely to <br />exist and can become apparent only during additional on site work. <br />For this reason, and because of our familiarity with the project, <br />Lambert and Associates should be retained to observe site <br />conditions during construction, to observe the geotechnical <br />engineering aspects of the construction and to be available in the <br />6 <br />jitam6ert anD ~,s~,oociates <br />CONSULTING GEOTECNNICAL ENGINEERS AND <br />MATERIAL TESTING <br />• <br /> <br /> <br />