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Walstrum Spur Amendment,Geotechnical Stability Exhibit Revised September 2021 Table 1: Slope Stability Modeling Results OVERALL SLOPEOF SECTION DIP OF ROCK SEISMIC FACTOR OF DRMS FoS ABOVE 8000 BELOW 8000 COEFFICIENT SAFETY REQUIREMENTS 1 41 Degrees 1:1 0.6:1.0 i 0.00 2.63 1.3 1 41 Degrees 1:1 0.6:1.0 0.12 2.12 1.15 I 1 31 Degrees 1:1 0.6:1.0 0.12 2.18 1.15 1 51 Degrees 1:1 0.6:1.0 0.12 2.11 1.15 2 Homogeneous N/A 0.6:1.0 0.00 2.42 1.3 2 Homogeneous N/A 0.6:1.0 0.12 2.12 1.15 3 41 Degrees 1:1 0.6:1.0 0.00 2.49 1.3 3 41 Degrees 1:1 0.6:1.0 0.12 2.17 1.15 4 i 41 Degrees 1:1 0.6:1.0 0.00 3.14 1.3 4 41 Degrees 1 1 0.6:1.0 0.12 2.73 1.15 5 41 Degrees N/A ' 0.6:1.0 0.00 3.76 1.3 5 41 Degrees N/A 0.6:1.0 0.12 3.19 1.15 6 Xf mogeneous N/A 0.6:1.0 0.00 5.68 1.3 6 Xf Homogeneous N/A 0.6:1.0 I 0.12 4.65 I 1.15 Hypotheticald of Low Strength Rock in FootwallSlope 10-ft-thick Xb 2 0.6:1.0 0.12 1.15 1.15 at 35 Degrees 2 j 20-ft-thick Xb i - ----,-- --_-at 35 Degrees' 0.6:1.0 0.12 0.95 i 1.15 "Sensitivity analysis 6.5.5 Kinematic Studies As mentioned earlier, geophysical logging was used to determine foliation trends and identify structural discontinuities. The data provided by Jet West were uploaded into RocScience DIPS for analysis. As is typical with metamorphic rock, the degree of folding can make analysis challenging because of the dynamic geometry. By observing the foliation trends for 100-foot depth intervals, it can be seen that while the majority of the foliation planes dip toward the north at around 40 degrees, the pole of the predominant joint set changes azimuth by 10 to 20 degrees and dip by around 10 degrees between those 100-foot depth filtered intervals. Some features that appeared to be open fractures or disconformities were identified in the geophysical logging. When 100-foot intervals are prepared, there are very few intervals that have more than four poles with the same pole (+/-5 degrees in azimuth and or dip). This is indicative of a generally wide fracture spacing. Planar failure may occur if a geologic disconformity dips out of the rock slope at an angle that is shallower than the angle of the slope and greater than the effective friction angle along the disconformity, as shown with the hypothetical layer of low strength biotite gneiss. The work of Wylie and Mah in Rock Slope Engineering (Wylie & Mah 2004) notes that planar sliding is not possible if the dip direction of the discontinuity differs from the direction of the face by more than 20 degrees. The stereonets presented in Appendix F indicate that there are foliation OTETRA TECH Page 31135