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It is Barr's opinion that the construction activities and quality control measures performed as part of <br />the project are in general accordance with the recommendations provided by Barr to West Elk Mine <br />personnel. <br />2.4 Final Conditions <br />As -built survey shots of key locations on the repaired slope were received by Barr on May 3, 2012. <br />The seepage and slope stability models were updated to reflect the as -built conditions. A topographic <br />map that incorporates the survey information is shown on Figure 6. <br />2.4.1 Approach to Slope Stability Analysis <br />A slope stability analysis was performed to quantify the stability of the reconstructed slope. The main <br />objective of the slope stability analysis was to evaluate the stability of the reconstructed slope with <br />the associated haul road under static conditions. Two types of stability analyses are typically <br />performed for slopes: the Undrained Strength Stability Analysis (USSA) and the Effective Stress <br />Stability Analysis (ESSA). The USSA is performed to analyze the case in which loading or <br />unloading is applied rapidly and excess porewater pressures do not have sufficient time to dissipate <br />during shearing. This scenario typically applies to loading from, for example, embankment <br />construction where the loading takes place quickly relative to the permeability of the soils. Loading <br />from floodwaters also meets these qualifications. Unloading, such as dragline excavation during strip <br />mining, falls into this category, as well. This is often referred to as the "end -of -construction" case. <br />The ESSA is performed to account for much slower loading or unloading, or no external loading, in <br />which the drained shear strength of the materials is mobilized and no shear -induced pressures are <br />developed. For example, a slowly moving landslide is usually analyzed using the ESSA method. For <br />this reason, the ESSA is often referred to as the "long term" case. <br />Both the USSA and ESSA cases were examined as part of the Haul Road HR -1 slide stabilization <br />project. <br />2.4.2 Modeling <br />The seepage analysis was performed by SEEP/W, a finite element program that analyzes <br />groundwater seepage within porous materials like rock and soil for traditional steady-state flow or <br />transient analyses. The computed pore -water pressures and groundwater surface can then be imported <br />into SLOPE/W analyses, allowing the program to analyze complex saturated/unsaturated or transient <br />conditions. SLOPE/W uses limit equilibrium theory to compute a factor of safety for earth and rock <br />P:\Mpls\06 CO\26\06261003 Haul Road Slide Repair\WorkFiles\Report\MCC—Slump—Repair-Instrumentation-Drain Rev 2012-12-12.docx 8 <br />