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III IIIIIIIIIIIII III <br />• ENVIROCON, INC. <br />395 WEST IRONWOOD DRIVE <br />SOUTH SALT LAKE CITY, UTAH 8a 115 <br />TELEPHONE: (607(a65-9565 <br />FA%: (607) a85-1a4a <br />EN~~IROCON, INC. <br />September 27, 1994 <br />ENV # 1430.3004 <br />Mr. John Poulos <br />Mountain Coal Company <br />West Elk Mine <br />P.O. Box 591 - " <br />Somerset, Colorado 81434 <br />RE: FACTOR OF SAFETY FOR THE LONE PINE GULCH FAN BENCH <br />Deaz John: <br />• The following letter summarizes the recalculated factor of safety for the <br />proposed fan bench located in the upper portion of Lone Pine Gulch at a proposed <br />elevation of 6480 feet above mean sea level. The proposed fan bench will have a <br />cuUfill balance of approximately 18,000 cubic yards and will give a total fan bench <br />disturbance area of approximately 0.782 acres. The following paragraphs describe <br />the slope stability analysis required for permit submittal. <br />A slope stability analysis was performed on one profile. This profile <br />encompasses the widest and steepest portion of the proposed fan bench. The slope <br />stability analysis utilized the PCSTABL5 program to determine the factors of safety <br />against failure. The factor of safety is the ratio of the forces resisting the slope <br />movement to the forces which cause the slope to fail. The resisting forces are <br />determined by the sheaz strength of the native soils to resist failure along a specific <br />surface. The forces which tend to cause failure include, but are not limited to: (a) <br />the angle of the slope; (b) the location of existing roads and drainage ditches in <br />relation to the slope; (c) pore pressure or water table acting on the failure plane; and <br />(d) the characteristics of the native soil and bedrock found in the slope. A factor of, <br />safety of 1.0 implies that the slope is mazginally stable for the cross-section profile, <br />native clay/topsoil material strengths, groundwater, and the slope conditions. In <br />recalculating the factor of safety for the fan bench, Envirocon has designed the <br />proposed cut and fill slopes above the fan bench to have a minimum factor of safety <br />of 1.5, as recently required by the State of Colorado Mined Land Reclamation Board. <br />n <br />U <br />A a ~ 'i Company ~~ <br />