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6. Recommendations <br /> The minimum FOS for the mine highwalls within the South and West Quarries has been <br /> established at 1.2. This is considered the minimum FOS for rock in mine highwall situations. <br /> Designing highwalls for stability involves developing accurate and representative geological <br /> conditions within the South Quarry and West 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 and West Quarries is dependent on many different parameters. <br /> As the above mentioned geological conditions are highly variable within the mine, any <br /> design recommendations carry geotechnical risk. All mine highwall design <br /> recommendations made herein carry some risk of failure. For the both quarries, GEI <br /> weighed AI's desire to optimize reserves against developing highwall configurations that <br /> maximize local and global highwall 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 quarries,that could cause assumptions <br /> presented herein 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 Morrison Quarry. In <br /> addition, highwall locations where the sillimanitic gneiss is encountered at in-wall <br /> thicknesses greater than '/4 of the highwall height have a separate configuration. <br /> 6.1.1.1 South Quarry <br /> GEI's 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 up to 30H:70V <br /> (horizontal:vertical) benches. These areas exhibited favorable geological conditions <br /> Aggregate Industries Morrison Quarry GEI Consultants, Inc. <br /> AM-06 Geotechnical Stability Exhibit 38 August 2018 <br />