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6. Recommendations <br /> The minimum FOS for the mine highwalls within the South Quarry has been established at <br /> 1.2. This is considered the minimum FOS for rock in mine highwall situations. Designing <br /> highwall for stability involves developing accurate and representative geological conditions <br /> within the South quarry including: <br /> • Rock type <br /> • Structural conditions within the rock (discontinues,joint sets, faults, etc.) <br /> • Geological stratification <br /> • Rock weathering <br /> • Rock strength <br /> Highwall design for the South Quarry is dependent on many different parameters. As the <br /> above mentioned geological conditions are highly variable within the mine, any design <br /> recommendations carry geotechnical risk. All mine highwall design recommendations made <br /> herein carry some risk of failure. For the South Quarry, GEI weighed AI's desire to optimize <br /> reserves against developing highwall configurations that maximize local and global highwall <br /> stability. <br /> Our recommendations presented below are based on drilling results conducted by various <br /> entities at various times within the life of the South Quarry as well as annual report mapping <br /> conducted by GEI. While these are considered to be representative of the overall material <br /> within the mine, there will be variability within the South Quarry, that could cause <br /> assumptions presented herin to become invalid. <br /> 6.1.1 Highwall Recommendations <br /> The results of kinematic and slope stability analyses conducted as part of our scope indicate <br /> that two main highwall/bench configurations will result in an acceptable FOS (>1.2) while <br /> allowing Al to best utilize the remining aggregate reserves within the South Quarry. In <br /> addition, highwall locations where the sillimanitic gneiss is encountered at in-wall <br /> thicknesses greater than '/4 of the highwall height will have a separate configuration. GEI's <br /> recommendations for South Quarry highwall configurations are presented below: <br /> • The recommended final highwall configuration within south and west highwalls <br /> (north and east facing) below El. 7,000 feet consists of 30H:70V benches. These <br /> Aggregate Industries Morrison Quarry GEI Consultants, Inc. <br /> South Quarry Highwall Design Technical Revision 27 August 2017 <br />