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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 | 10 <br />4 Laboratory Testing <br />4.1 Previous Testing <br />Previous testing results from several firms, mostly performed by Advanced Terra Testing, Inc. of <br />Lakewood, CO, was made available to HDR. Refer to the sections below for a summary of the <br />performed laboratory testing, and refer to Appendix A, Subsurface Exploration Findings, for the <br />full laboratory reports. <br />4.1.1 Historic Strength Testing <br />A total of seven (7) Uniaxial Compressive Strength (UCS) tests were performed on historic <br />borings in accordance with ASTM D7012-14, Method D. Refer to Table 2 below for a summary <br />of the testing results. <br />Table 2 – Summary of Historic UCS Testing <br />Boring Depth Rock Type <br />Unconfined <br />Compressive Strength <br />(psi) <br />M-2-18 43.0-43.5 Biotite Gneiss 20314 <br />M-2-18 264.0-264.5 Granitic Gneiss 33012 <br />M-3-18 303.7-304.5 Talc Gneiss 8386 <br />M-3-18 337.0-337.5 Talc Gneiss 5321 <br />M-4-18 173.0-174.0 Granitic Gneiss 9221 <br />M-5-18 270.0-271.0 Biotite Gneiss 3601 <br />M-5-18 305.0-306.0 Pegmatite 7658 <br /> <br />Direct shear testing was performed on a total of 22 samples in accordance with ASTM D5607. <br />Samples were tested using either natural fracture points or saw cuts, and with normal stresses <br />approximately equivalent to in situ conditions. Refer to Table 3 below for a summary of the test <br />results. <br />