2020-11-05_REVISION - M1973021 (12)

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6. Stability Analyses Methodology This section describes a series of stability analyses of the highwall configurations for the revised South Quarry configuration and proposed West Quarry highwall design. The purpose of these stability analyses is to: 1) Evaluate South Quarry slope stability due to the proposed increase in bench width to highwall height configuration from 401-1:40V to 30H:70V, where H is the horizontal bench width in feet and V is the vertical highwall height in feet); and, 2) Support the development of an optimum highwall configuration that meets industry standards for stability while optimizing remaining Quarry reserves. 6.1 Key Assumptions The information used to characterize the rock mass for both the South Quarry and West Quarry is mostly based on observations made at the South Quarry during annual inspections and drilling programs, and this information is considered applicable to the West Quarry, which has a much smaller dataset. The information includes foliation and joint set information(average strike, dip, and condition of discontinuities) as well as laboratory testing data. The surface and subsurface information from the West Quarry is limited, and the South Quarry subsurface information is applied to the West Quarry stability evaluations. The GEI's experience at Morrison Quarry indicates that structural geological characteristics are relatively consistent across the site, and only minor local variations in geological conditions are anticipated. This noted assumption, however, should be revised with measurable rock test data obtained as mining progresses within the West Quarry. 6.2 Kinematic Analyses A kinematic analysis was performed to evaluate structurally controlled block failures, including planar sliding, wedge sliding, direct toppling, and flexural toppling failures. The evaluation is performed to assess whether isolated block failures are possible for a given highwall orientation. The analyses were performed using the RocScience computer program Dips (V8.0). The kinematic analyses were performed using discontinuity data obtained during mapping of the South Quarry (2013 through 2019 Annual Reports) as well as from 2018 field mapping of the West Quarry. The dataset includes 655 discontinuity measurements which were collected during the South Quarry annual inspections and 29 measurements from geologic mapping at the West Quarry. The discontinuity measurements were used without processing or filtering, and no external loads were considered. Each discontinuity type was equally weighted. 25 Aggregate Industries—Morrison Quarry GEI Consultants, Inc. AM-07 Geotechnical Stability Exhibit November 2020