2020-11-05_REVISION - M1973021 (12)

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8.2.1 Visual Inspection Monitoring GEI believes continuous monitoring and examination of active and reclaimed areas within the South and West Quarries will be necessary through the life of the quarry. On a weekly basis, the active portions of the South and West Quarry highwalls should be monitored and inspected for signs of instability. The following warning signs of slope instability should be inspected and documented in the weekly inspection reports: • Tension Cracks—Monitor cracks on the top of slopes and/or benches for signs of highwall instability. • Scarp, bulges, or creep— Scarps are areas where material has vertically moved downslope. Scarps can be several inches to many feet, occur relatively fast, and have visible offset. Bulges and Creeps are areas where material has moves downslope slowly and can be evident. • Abnormal Water Flows—Flowing groundwater is typically not present within highwalls exposed within the Quarry, and if the presence of flowing water out of final or active highwalls is observed this indicates a change in subsurface conditions that could lead to slope failure. • Abnormal or increased rockfall at toe of cut 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, or a rockfall surface that extends through several benches. • Care to keep personnel and vehicles off inactive benches improve safety. 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 should be evaluated kinematically to verify that the recommendations provided herein are valid for the actual geological site conditions encountered during excavation. Our recommendation is that this should be conducted four(4) times annually for the first two (2) years of highwall development, two (2)times annually for the next two (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. 8.2.2 Survey Monitoring GEI also recommends that slope monitoring within the South and West Quarry areas utilizing total station 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 Aggregate Industry 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. 43 Aggregate Industries—Morrison Quarry GEI Consultants, Inc. AM-07 Geotechnical Stability Exhibit November 2020