2023-07-14_PERMIT FILE - C1981010 (16)

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January 2, 2020 Page 2-2 Agapito Associates, Inc. Table 2-2. Slake Durability Classification Second Cycle Slake Durability (%) Classification 0–25 Very low 25–50 Low 50–75 Medium 75–90 High 90–95 Very high 95–100 Extremely high Two known normal faults intersect the HWM area for the J Pit, H Seam, trending about north 80 degrees west (N80°W) (Figure 1-1). The faults have displacements of 15 and 25 ft and are located within gouge zones approximately 30 ft wide. The precise location of the faults is uncertain; therefore, the boundary of the HWM area excludes a 75-ft buffer zone on either side of the suspected fault location. Once the highwall is exposed and the fault locations are better defined, the buffer zone width may be reduced, allowing additional HWM openings to be mined. No other faults that may impact mining have been identified in the other HWM areas. Aquifers at Trapper are associated with the coal seams and adjacent sandstones, with intervening shales and clays inhibiting vertical movement. Some groundwater inflows can be expected during HWM operations. Most highwall miner openings will be downdip, but water quantities are not expected to hamper HWM operations. For each HWM area, seam models provided by Trapper were examined to establish the geometric characteristics and assess their minability. A summary of characteristics of the target seams in the various Pits is shown in Table 2-3. Table 2-3. Physical Characteristics of the Target Seams Pit Seam Cover Range (ft) Thickness Range (ft) Interburden Range to Target Seam Below (ft) I Pit East F 35–95 2–5n/a I Pit Middle F 40–215 5–660–120 I Pit West F 65–140 5–6n/a J Pit East G2 45–170 4 n/a J Pit West G2 45–195 4–5n/a N Pit L 40–230* 2–830–50 M 60–270* 3–550–60 Q 100–320* 7–11 n/a L Pit H 60–240 7–12 n/a K 60–210 8–11 75–100 Q 120–300 9–11 n/a To account for spoil, values reflect the equivalent rock depth of cover, with a rock unit weight of 162 pcf.