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Thompson Properties November 7, 2006 Page 2 the top of the slope. No slump or earth slide features suggesting the potential for deep-seated instability of the existing slopes was observed. Subsurface Conditions: Afield exploration program consisting of exploratory borings was not performed to evaluate subsurface conditions for the proposed mine expansion. Instead, surface conditions observed in the east cut slope of the existing mine (described above), and information on subsurface conditions provided by the completion logs for 6 wells located within and immediately adjacent to the proposed expansion were considered. The well completion logs were included as part of a study performed for the proposed expansion titled "Hydrological Assessment for Gravel Pit Expansion, Granby, Colorado' by ERO Resources Corporation dated May 10, 2006. Subsurface conditions reported in the well completion logs generally consisted of gravel, which extended from the surface to depths ranging from 58 to 72 feet, and was underlain by shale bedrock. Based on subsurface conditions reported for 3 of the six wells that were located within or immediately adjacent to the proposed expansion, bedrock was encountered at elevations ranging from about Elevations 7967 to 7976 feet, approximately 24 to 33 feet below the proposed mine bottom Elevation 8000 feet. Ground water was encountered at depths ranging from Elevations 7972 to 7987 feet, approximately 13 to 28 feet below the proposed mine bottom. Laboratory tests were performed on four soil samples obtained from the surface of the east cut slope of the existing pit at the time of our geologic reconnaissance to help characterize the shear strength and engineering characteristics of the soil anticipated to be encountered in the excavated slopes of the proposed expansion. The results of gradation tests performed on the samples are presented on Figs. 2 and 3, and a summary of gradation and Atterberg limits tests performed on the samples is presented in Table 1. Slooe Stability: Slope stability analyses were performed to evaluate the global stability of the final cut slope proposed for reclamation of the mine. Two-dimensional, limit-equilibrium analyses were performed using Spencer's method and the computer program titled UTEXAS3. A 40-foot high cut slope inclined 2:1 (horizontal:vertical) was modeled, and estimated drained (effective) shear strengths for the natural alluvial gravel and underlying shale bedrock were developed using information obtained from our field observations, laboratory test results, and published correlations between shear strength and other engineering properties for similar materials. A relatively high ground water table located at the proposed pit bottom Elevation 8000 feet, approximately 13 to 28 feet above that measured in the well borings described above, was also modeled, which we consider to be conservative. A minimum acceptable slope stability factor of safety of 1.5, generally considered acceptable for the long-term stability of slopes, was considered. o,5~nr , Kumar & Associates, Inc.