Laserfiche WebLink
bench highwall should be sloped at a 2H:IV. We anticipate that this configuration will <br /> reduce the"crushing" instability. <br /> Recommendations for Sillimantitic Gneiss highwall slope configurations were developed <br /> sent to Al for approval. These recommendations are included in this report in Figure 9. <br /> 6.1.1.4 Highwall-Mafic Dike Interactions <br /> Mapped mafic dikes present within the Central, South, and West quarries are not projected to <br /> adversely impact future South or West Quarry highwalls. However, due to variations in local <br /> geology, the nature and extent of the mafic dikes may be different than mapped, leading to <br /> possible impact to future highwalls. Therefore, the minimum highwall offsets, discussed in <br /> Section 6.1.1.2 above, should be anticipated if mafic dikes are believed to impact highwalls. <br /> During ongoing mining operations, monitoring of the geological and structural conditions of <br /> the quarry areas should be performed as discussed below, so that mafic dike offset <br /> recommendations can be evaluated for current conditions and highwall offsets implemented, <br /> if necessary. <br /> II <br /> 6.1.2 Monitoring Recommendations <br /> Along with a robust engineering analysis and design program for highwall development, <br /> monitoring of the mine highwalls is a critical step in recognizing and reducing the potential <br /> for both small and large-scale failures. A site-specific monitoring plan has been developed <br /> and implemented within the South u and GEI strongly recommends that a similar plan <br /> P Quarry g Y <br /> should be developed and implemented in the West Quarry so differing structural <br /> discontinuity conditions (from what was assumed in this stability exhibit) and potential slope <br /> instabilities can be detected and addressed at an early, non-critical time in mine development. <br /> 6.1.2.1 Visual Inspection Monitoring <br /> GEI believes continuous monitoring and examination of active and reclaimed areas within <br /> the South and West Quarries will be necessary through the life of the mine. On a monthly <br /> basis, the South and West Quarry areas should be monitored and inspected. At a minimum, <br /> the following warning signs of slope instability (global and local) should be looked for noted <br /> and addressed : <br /> • Tension Cracks-Cracks on the tops of slopes and/or benches are signs of highwall <br /> instability. <br /> • Scarp, bulges, or creep- Scarps are areas where material has vertically moved <br /> downslope. Scarps can be several inches to many feet, occur relatively fast, and <br /> would have visible"offset". Bulges and Creeps are areas where material has moves <br /> downslope slowly and can be evident in bent vegetation or"incorrectly" oriented <br /> trees. These warning signs are likely to be present in reclaimed slopes and/or areas <br /> not undergoing active mining, such as areas outside the mine footprint, either beyond <br /> the permitted mine limit or in future expansion areas. <br /> • Abnormal Water Flows-Excessive flowing groundwater is typically not present <br /> within highwalls exposed within the Quarry. The presence of flowing water out of <br /> Aggregate Industries Morrison Quarry GEI Consultants, Inc. <br /> AM-06 Geotechnical Stability Exhibit 40 August 2018 <br />