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Slope Evaluation and Remediation <br />West Elk Mine <br />Somerset, Colorado <br />dry to moist and low to high plasticity. These materials were derived from the <br />Cretaceous -aged Mesaverde Formation. <br />Groundwater was not encountered in the test holes at the time of the subsurface <br />exploration program but were measured in Test Hole 4 and 5 at depths of 20 (TH 4) and <br />24 (TH 5) feet below existing grades the following day. Groundwater was also measured <br />by a representative of the Client on September 16 (10 days later), at depths of 16 (TH 4) <br />and 23 (TH 5) feet below existing grades. However, based on our experience with <br />similar projects, groundwater levels should also be expected to fluctuate, and likely rise, <br />in response to annual and longer -term cycles of precipitation, irrigation, snow melt, <br />surface drainage, land use, and the development of transient, perched water conditions. <br />SLOPE EVALUATION <br />The existing gully (drainage channel) and associated slopes descending from the coal <br />stockpile and access road reportedly has been marginally stable for a number of years. <br />Additional fill material apparently has been added periodically to maintain grades along <br />the access road but particularly within the old drainage channel (gully). The rate of <br />movement of this local area has been significantly faster (i.e. feet per year) compared to <br />that of the much larger landslide that underlies much of the mine. We understand that <br />the older and larger landslide complex is currently moving at a rate of about 1 inch per <br />year. The interpreted limits of the subject landslide are shown on Figure 1 <br />Again, we understand that a gentle gully (drainage channel) previously descended along <br />roughly the centerline of the recent landslide. In addition, a coarse rock fill previously <br />had been placed in the Swale. <br />It is not readily apparent to what degree conventional densification of the previously <br />placed fill has contributed to the recurrent movements of the recent landslide feature in <br />this location. GROUND has assumed (conservatively) that movement has been the <br />result entirely of landslide -type movement within the recent landslide feature and <br />distinctly different (i.e. rate, magnitude, suspected cause, impact, etc.) from the larger <br />landslide complex. <br />SlopeW Modeling Stability modeling of the subject landslide was performed using the <br />SlopeW computer program along the geologic section line A — A'. Using estimated <br />values for the material properties of the geologic units based on the field and laboratory <br />Job No. 11 -6014 GROUND Engineering Consultants, Inc. Page 6 <br />