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Inclinometer casing was installed in the following boreholes: B -4, B -5, and B -8. The purpose of the <br />inclinometers was to measure any slope movement within the colluvium. The depths to which the <br />inclinometer casing was installed ranged from 25 to 35 feet. <br />2.2 Geotechnical Analysis and Design <br />MCC's coal preparation plant (CPP) will generate much of the coal refuse material to be placed in <br />the RPE East refuse pile described by this technical revision application. The screening and CPP <br />process will produce a refuse that is expected to be coarser than any refuse materials currently <br />available on site. Therefore, materials in the Lower Refuse Pile (LRP, see Figure 1 -2) were selected <br />as the most representative material for analysis and to provide a basis for geotechnical design. <br />The geotechnical analysis and design assumes that the refuse to be placed in the RPE East will have <br />geotechnical characteristics of the refuse to be produced by the new preparation plant are expected to <br />be equal to or better than the characteristics of the refuse in the LRP. The following sections <br />summarize the data used and analyses completed for the geotechnical analysis. <br />Two types of stability analyses are typically performed for dams and slopes: the Undrained Strength <br />Stability Analysis (USSA) and the Effective Stress Stability Analysis (ESSA). The USSA is <br />performed to analyze the case in which loading or unloading is applied rapidly and excess pore water <br />pressures do not have sufficient time to dissipate during shearing. This scenario typically applies to <br />loading from embankment construction, for example, where the loading takes place quickly relative <br />to the permeability of the soils. It 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 very slowly moving landslide is best analyzed using the ESSA method <br />(albeit over time the rate typically increases, resulting in an undrained condition). For this reason, the <br />ESSA is often referred to as the "long term" case. <br />Both the USSA and ESSA were performed as part of the slope stability analysis for the RPE East <br />refuse pile. <br />2.2.1 Software <br />Both seepage and stability modeling were performed on the RPE East refuse pile. The software <br />packages used in this exercise and modeling details are described below. <br />PAMpls \06 CO \26 \06261003 MCC Refuse Pile Site Review & Permit \WorkFiles\Permit Application \Text \2010- 04- 19_RPE East Permit Application.doc 3 <br />