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Geotechnical Stability Exhibit <br /> Engineering Evaluation of Highwall Design for the South Quarry of the Morrison Quarry <br /> <br /> January 2024 | 22 <br />values are comparable to those utilized by GEI in their previous stability design and analyses. <br />This comparison indicates a consistent trend in the distribution of very hard quartz and quartz- <br />like material, hard biotite gneiss of varying mineral assemblages, and veins or regions of heavily <br />fractured and/or altered soft material such as talc, chlorite, and intermixed sedimentary material. <br /> <br />Figure 7: Scatter Plot of Laboratory Tested UCS Values and Categories for Design <br />5.2.1.2 Design GSI Value <br />Design GSI values were based on field evaluations by HDR geologists of exposed typical <br />competent and talc-gneiss material within the quarry. GSI values are inherently variable by <br />definition, and the existing variability of a metamorphic environment suggests that the <br />recommended GSI values may differ from location to location. A holistic view of the geologic <br />conditions at the site were considered in developing the recommended GSI values. An example <br />of a typical exposed rock face for competent material is presented in Figure 8 and an example <br />of a typical exposed rock face for talc-gneiss material is presented in Figure 9.