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Chandler Martin July 14, 2006 Page 2 Geotechnical Requirements (Refer to CCR sections 3502,3704) SMARA establishes performance standards for slope stability and requires that cut slopes, including final highwalls and quarry faces, have a minimum slope stability factor of safety that is suitable for the proposed end use and conform to the surrounding topography and/or approved end use. CCR section 3502 (b)(3) states that the designed steepness and proposed treatment of the final slopes shall take into consideration the physical properties of the slope material, its probable maximum water content, landscaping requirements, and other factors. In all cases, reclamation plans shall specify slope angles flatter than the critical gradient for the type of material involved. Whenever final slopes approach the critical gradient for the type of material involved, regulatory agencies shall require an engineering analysis of the slope stability. Special emphasis on slope stability and design shall be necessary when public safety or adjacent property may be affected. A preliminary geotechnical study was prepared for the site by Geomatrix Consultants, Inc. and is dated March 28, 2002. The geotechnical report summarizes the results of a preliminary assessment of slope stability for the proposed temporary (active mining) and permanent (final reclamation) slopes. Factors of safety are stated to range from 1.2 to 1.6 for temporary and permanent slopes under static conditions; pseudo static values are reported as less than 1 (unstable). _ 3. The geotechnical report does not provide any geotechnical cross-sections to demonstrate the geologic conditions of the proposed mine slopes. OMR recommends that geologic cross-sections of the proposed mine's cut and fill slopes, both temporary and final, be provided to document the site's geotechnical conditions. The number and orientation of the cross-sections _. should be adequate to provide the basis for the engineering slope stability analysis. 4. The geotechnical study presents an evaluation of slope stability starting on page five and lists factors of safety on page six of the report. However, the report does not provide any of the estimated soil parameters (e.g. angle of internal friction or cohesion) or computer model output for OMR to determine if the calculated results are correct and that the factor of safety of the proposed final cut slopes for the mine will be adequate for the proposed end land use. OMR recommends that the geotechnical report be revised to provide a more complete engineering analysis of the proposed final mine slopes. OMR recommends that the slope stability analysis include the following elements: