Laserfiche WebLink
3.2 Annual Inspections <br /> Al performs annual monitoring at Morrison Quarry that includes a visual inspection of <br /> exposed highwalls, reclaimed areas, haul roads, and other features to document mine <br /> progress and changes in conditions. New areas affected by mining each year are mapped to <br /> characterize rock joint and foliation features, as well as other factors affecting rock stability <br /> including persistent intrusions, shear zones, faults, or failure surfaces. Orientations are <br /> collected using a Brunton compass and are taken from a safe distance from highwalls <br /> (approximately 30 ft) due to mining activities and rockfall safety concerns. <br /> The annual monitoring inspection is performed using observational methods described in <br /> Amendment No. 3 and Amendment No. 4. The annual reports document changes in the <br /> bench stability and include collecting Rock Mass Rating values (Bieniawski, 1976)for <br /> recently exposed highwall benches. <br /> 3.3 Groundwater <br /> No flowing groundwater is noted within any of the highwalls during annual report mapping. <br /> Groundwater levels as observed in monitoring wells east of the South Quarry suggest the <br /> water level is around El. 6,450 to El. 6,600 feet below the base on the pit based on <br /> measurements collected in monitoring wells MW-19-01 and MW-19-02. Permit <br /> requirements state that any groundwater exposed during mining activities must be addressed <br /> as though it were a groundwater well, and Al maintains a requirement that all excavations <br /> must be performed in the dry. Al recently began measuring groundwater levels on a monthly <br /> basis to monitor levels in advance of excavation. <br /> 3.4 3D Geological Model <br /> A three-dimensional (313) geologic model of the South Quarry and West Quarry was <br /> developed to provide a visual representation of bedrock conditions observed in <br /> reconnaissance mapping and data obtained from the subsurface explorations. The 3D <br /> geologic model was developed using Earth Volumetric Studio (EVS) software <br /> version 2017.6.0 produced by C Tech Development Corporation. The main inputs included <br /> surface topography, aerial imagery, simplified borehole lithology, and mapped surface <br /> geology. The 3D model is documented in a Technical Memorandum (TM) that is provided in <br /> Appendix B. Figures 6 through 10 show the interpreted subsurface conditions based on the <br /> model outputs. <br /> The model indicates that sillimanitic gneiss is likely to be present at lower elevations of the <br /> South Quarry highwall and within the south-facing highwalls of the West Quarry. The <br /> sillimanitic gneiss is likely to contain metasomatized gneiss and will require special <br /> stabilization and monitoring considerations for highwall stability. <br /> 13 <br /> Aggregate Industries—Morrison Quarry GEI Consultants, Inc. <br /> AM-07 Geotechnical Stability Exhibit November 2020 <br />