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~~ 5- ~ <br />KENNETH C. KO & ASSOCIATES, iNC. <br />215 WEST LOUIS{ANA DENVER, COLORA00 80223 (303 778.8748 <br />~• TLX 45-0225 <br />May 13, 1982 <br />Pueblo Coal, Inc. <br />28525 EasC U.S. 160 <br />Durango, Colorado 81301 <br />ACtn: Mr. Ray Lewis <br />Report <br />Stability Analysis <br />Proposed Pit Backfill Slopes <br />Carbon Junction Mine, Colorado <br />For Pueblo Coal, Inc. <br />INTRODUCTION <br />In response to your letter of request dated May 3, 1982, and in regards <br />• to the requirements of the Colorado Mined Land Reclamation Board (MLRB), <br />Kenneth C. Ko S Associates, Inc. (KCKA) has completed the stability analyses <br />for the proposed pit backfill slopes at the Carbon Junction Mine. This <br />letter report summarizes the results of our investigation. <br />For our use in this study, we were provided a copy of the mine permit <br />application and addendum, volume calculations, plan maps of both the original <br />topography and tt{e proposed fills, and boring logs. From this data we have <br />prepared cross sections and profiles for our analyses. Although no labora- <br />tory test results are available for the soil engineering characteristics of <br />the proposed fill materials, and natural soils and rock, the provided data <br />has enabled us to conservatively estimate the properties (i.e., compacted <br />density, shear strength, cohesion and friction angle) required for the analyses. <br />The proposed exterior slope ratio for the backfill material is 3:1 (hori- <br />zontal to vertical). The most critical areas of the fill slope from a slope <br />stability standpoint, will be in areas where the foundation soils may become <br />saturated in time. We have therefore chosen two sections in the vicinity <br />,. <br />. 1 <br />