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final or active highwalls, reclaimed slopes, and/or areas not undergoing active mining would indicate a change in subsurface conditions that could lead to slope instability. • Abnormal rockfall at toe of slopes and or highwalls—Rockfall is a typical feature within the Quarry. When monitoring for"abnormal"rockfall,rubble in areas where rockfall is typically not present, an increase in volume, and/or a distinct change in rubble dimensions could indicate slope instability and/or movement. GEI recommends that as mining progresses within the West Quarry, RMR data should be obtained structural features within the highwalls exposed during mining. The RMR data obtained should be evaluated kinematically to verify that the recommendations provided herein are valid for the actual geological site conditions encountered. Our recommendation is that this should be conducted 4 times annually for the first 2 years of highwall development, 2 times annually for the next 2 years of highwall development. If the conditions noted verify our assumptions, RMR should be obtained annually thereafter during the Geotechnical Addendum to the M-1973-021 Annual Report. 6.1.2.2 Survey Monitoring GEI also recommends that slope monitoring within the South and West Quarry areas utilizing electronic distance measurement (EDM) techniques should be conducted in concert with monitoring for warning signs discussed in section 6.1.2.1 above. EDM is a common and effective method for monitoring slope movement within rock quarries. The Al surveyor should set monitoring control points (prisms) at critical locations within the South Quarry. The control points should be permanent and located in areas where ongoing mining activities will not impact them, yet be in locations central enough to capture any potential slope movement. A control point installation plan should be developed in consultation with GEI, so that critical areas can be monitored sufficiently. The control points should be monitored weekly, after the initial installation. After several months of monitoring, the results should be reviewed by GEI for signs of slope movement. Depending on this review, the slope monitoring frequency can be adjusted up or down. It should be noted that AI has contracted with GEI to implement a monitoring program within the South Quarry. As mining within the West Quarry progresses,the South Quarry monitoring program should be expanded to cover active areas of the West Quarry as well. 6.1.2.3 Additional Monitoring Additional monitoring can be implemented if signs of slope instability are noted or anticipated. This monitoring can be tailored to specific areas and/or failure modes and include: • Crack meters • Inclinometers • Piezometers • Wireline or borehole extensometers • Time domain reflectometry (TDR) Aggregate Industries Morrison Quarry GEI Consultants, Inc. AM-06 Geotechnical Stability Exhibit 41 August 2018