2021-02-05_PERMIT FILE - C1980007A ‎(5)‎

• Permit No: C1980007A
• IBM Index Class Name: Permit File
• Doc Date: 2/5/2021
• Doc Name: SUBSIDENCE EVALUATION
• Section_Exhibit Name: Exhibit 60E Subsidence Evaluation for the South of Divide and Dry Fork Mining Areas
• Media Type: D
• Archive: Yes

Subsidence Evaluation for the
Exhibit 60E Southern Panels, Apache Rocks West, & Sunset Trail Mining Areas Page 15
alignment of the E-seam panels from the B-seam panels, the maximum subsidence
over E-seam panel E 12 will have very little influence from the B-seam mining in
panel B 13-A.
Sunset Trail Minin Area: Overburden depth above the centers of the projected E-seam longwall
panels ranges from approximately 350 to 1,250 feet. With a projected longwall panel width of
1,080 feet, and assuming that the chain pillars (gate road pillars) are similar to those in longwall
panel B 17 of the Apache Rocks mining area, maximum subsidence (vertical displacement S. = a
• t) is predicted as follows (Table 4) for panels SS 1 through SS4:
• Panels SSI to SS4: These panels range from subcritical to supercritical (width-to-depth
ratio (W/d)ranges from 0.86 to 3.09).
1. Maximum vertical displacement above the chain pillars (S,,P) is expected to range
from 0.9 to 2.7 feet(0.1 to 0.3t)where the extraction thickness is 9 feet, and 1.4 to
4.2 feet where the extraction thickness is 14 feet.
2. Maximum vertical displacement (subsidence, S. = a • t) is projected to range from
5.4 to 7.2 feet(0.6 to 0.8t) where the extraction thickness is 9 feet, and 8.4 to 11.2
feet, where the extraction thickness is 14 feet.
5.3.1.2 Maximum Tilt
Maximum tilt (Mm) was calculated from differential vertical displacements at the West Elk Mine
monitoring network in terms of the ratio of maximum vertical displacement to overburden depth
(Sm/d in dimensionless units L/L)(Table 1 and Figure 5). Tilt values at West Elk Mine range from
1.4 to 2.1 percent. Maximum calculated tilt ranges from about two to three times Sm/d (2 to
3•(Sm/d))at West Elk Mine. Maximum tilt in the Southern Panels,Apache Rocks West,and Sunset
Trail mining areas is projected to range from 2.2 to 2.3 Sm/d. Maximum tilt in four different mining
areas studied by Dunrud in the Western United States ranges from 2.5 to 5•(Sm/d).
Southern Panels Mining Area:
As stated earlier in this report, tilt above the nine E-seam longwall panels (panels E1 to E9 and
E14)are projected to range between 2.2 and 2.3 Sm/d for coal extraction thickness ranging between
9 and 14 feet. These values are based on subsidence measurements at West Elk Mine (Table 1,
Figure 5). The overburden depth above the longwall panel centers ranges from 400 to 1,425 feet
(Table 2).
• Panels El to E9 and E14: Maximum tilt in these panels is projected to range from 0.008
to 0.045 (0.8 to 4.5 percent) where 9 feet of coal is extracted, and from 0.013 to 0.070
(1.3 to 7.0 percent)where 14 feet of coal is mined(Table 2).
Similarly, tilt above the longwall panels (panels B26 to B29) are projected to range between 2.2
and 2.3 Sm/d for coal extraction thickness ranging between 9 and 14 feet. These values are based
on subsidence measurements at West Elk Mine (Table 1, Figure 5). The overburden depth above
the longwall panel centers ranges from 600 to 1,500 feet (Table 2).
831-032.912 Wright Water Engineers, Inc.
December 2020