2021-10-11_REVISION - M1973021 (5)

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2 Aggregate Industries – Morrison Quarry GEI Consultants, Inc. AM-07 Geotechnical Stability Exhibit November 2020 section of this report, and Photo 1-1 and Photo 1-2 show highwall conditions as of December 2019. 1.3 Scope of Work The following scope of work (SOW) was included by GEI as part of the South and West Quarry highwall evaluation: • Establish site topography; • Perform onsite geological mapping and develop an updated three-dimensional (3D) geological model of the South, Central, and West Quarries, specifically highlighting the extents of sillimanitic gneiss and mafic dikes; • Evaluate subsurface information obtained by GEI and others, and perform laboratory testing to evaluate engineering characteristics of bedrock material from rock cores and grab samples; • Conduct stability analyses for global and local conditions with various highwall configurations for the South and West Quarries; and • Provide recommendations for the maximum highwall to bench ratio that can be mined within the mining cells. A series of kinematic, limit equilibrium, and finite difference stability analyses were performed to evaluate the proposed revised highwall configuration for the South Quarry and the proposed new highwall configuration for the West Quarry. The kinematic analyses were performed to evaluate toppling, wedge, and planar failure for rock bench exposures, and the limit equilibrium and finite element methods were used to evaluate local and global slope stability. The typical sections considered in these analyses are based on recent photos obtained from Unmanned Aerial Vehicle surveys (drones), topographic data, reconnaissance geologic mapping, borehole data, and GEI’s experience within the quarry. Results of the stability analyses were used to evaluate the proposed highwall configuration, including increased highwall height and the resultant overall highwall (pit) slope angle.