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Geotechnical Instabilities <br /> Appendix 1 —Geotechnical Stability Exhibit, Annual Performance Monitoring Geotechnical <br /> Addendums for South Quarry work to date, and DRMS comments on Appendix 1 all identify <br /> rock stability issues that must be addressed to ensure mining bench configurations and <br /> reclamation activities are conducted in a manner that meets Section 30.0—Factors of Safety for <br /> Slope Stability/Geotechnical Analyses requirements. After submission of AM07, Aggregate <br /> Industries has since moved on from the contractor which performed the geotechnical stability <br /> investigation. As a result, Aggregate Industries currently does not have access to the raw data <br /> and modeling information used by the previous contractor to assemble Appendix 1 — <br /> Geotechnical Stability Exhibit or the information gathered while conducting the past Annual <br /> Inspections and developing the Geotechnical Addendums. Based on the contractor change and <br /> unavailability of data, as you will see in Table 1 for many comments, Appendix 1 was not <br /> modified. <br /> Although this appendix was not modified, Aggregate Industries prioritizes safe working <br /> conditions for its employees, contractors, and future users of the property. They recognize the <br /> concerns identified by DRMS and in these reports, they have developed the following approach <br /> to prioritize additional investigations while ensuring operations can continue in a safe manner: <br /> Updated Mining Plan: Exhibit D — Mining Plan has been updated to require a more conservative <br /> benching configuration in areas where sillimanitic gneiss and foliations or fractures (that have <br /> resulted in kinematic failures) are observed. Specifically, a 401-1:40V (horizontal to vertical) <br /> bench configuration will be used in areas with thick units (more than 5 feet) of sillimanitic gneiss, <br /> and 2HAV maximum bench configuration will be used in areas where foliations or fractures are <br /> steeply dipping into the excavation and the strike is parallel to the bench face. Additionally, <br /> conservative benching configurations are applied in areas where studies or visual observations <br /> have identified instabilities and slope failures. For Phase III, 401-1:40V benches will be employed <br /> in the southwestern corner and eastern face of the South Quarry. This approach errs on the <br /> side of caution and allows mining to continue while additional studies are completed, as <br /> discussed below. <br /> Additional Studies: Based on Aggregate Industries' review of the reports to date, additional <br /> geotechnical studies will be conducted within the next year to address identified data gaps (e.g., <br /> seismic analysis, saturated rock stability, northwestern face rock stability) and DRMS <br /> comments, and to further support the application of the Observational Approach as mining <br /> continues. The geotechnical analysis will: <br /> • Complete an analysis of slope failures and other observed rock instabilities on the South <br /> Quarry western face. This will inform the need to conduct additional rockfall mitigation <br /> activities, either via catchment berms, rock scaling, buttressing, or other techniques, to <br /> support safe mining and reclamation working conditions. <br />