2021-10-05_REVISION - M1983033

• Permit No: M1983033
• IBM Index Class Name: Revision
• Doc Date: 10/5/2021
• Doc Name: Adequacy Review Response
• From: Albert Frei & Sons
• To: DRMS
• Type & Sequence: AM9
• Email Name: PSH
• Media Type: D
• Archive: No

Walstrum Spur Amendment,Geotechnical Stability Exhibit Revised September 30, 2021
Table 5:Slope Stability Modeling Results
OVERALL SLOPEOF •
SEISMIC •-
SECTION DIP OF ROCK FACTOR OF
COEFFICIENT I REQUIREMENTS
ABOVE 8000 BELOW 8000 SAFETY
1 41 Degrees 1:1 0.6:1.0 0.00 2.63 1.3
1 41 Degrees 1:1 0.6:1.0 0.12 2.12 1.15
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 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 mogeneous N/A 0.6:1.0 0.12 4.65 1.15
Sensitivity Analysis(Hypothetical),Seismic/Dynamic Results-Band of Low Strength Rock in Footwall Slope
2 10-ft-thick Xb N/A 0.6:1.0 0.12 1.15 N/A*
at 35 Degrees*
2 20-ft-thick Xb N/A 0.6:1.0 0.12 0.98 N/A*
at 35 Degrees*
*Sensitivity analysis assumes hypothetical lower quality(poor) rock that is outside the range of actual data.
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
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