2022-09-29_PERMIT FILE - C1980007 ‎(5)‎

• Permit No: C1980007
• IBM Index Class Name: Permit File
• Doc Date: 9/29/2022
• 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: No

831-032.923 Wright Water Engineers, Inc.
December 2021

EXHIBIT 60E
SUBSIDENCE EVALUATION
FOR THE SOUTHERN PANELS, APACHE ROCKS WEST,
& SUNSET TRAIL MINING AREAS
1.0 INTRODUCTION
This exhibit describes longwall panel subsidence processes that have been observed from studies
above longwall panels mined in Mountain Coal Company, LLC’s (MCC) West Elk Mine and from
other similar operations and studies. The subsidence information obtained from longwall mining
to date in the West Elk Mine has been used to project subsidence processes, amounts, and effects
to the Southern Panels, Apache Rocks West, and Sunset Trail mining areas within MCC’s permit
and affected area boundaries. This document is intended to comply with the Colorado Division of
Reclamation, Mining and Safety (DRMS) Regulations for Coal Mining, as revised September 14,
2005, under Section 2.05.6, Mitigation of the Impacts of Mining Operations.
This report was updated by Tetra Tech September 2007 and was added to the approved permit
document as Exhibit 60E to include the Dry Fork lease mining area with the longwall mining area
of the South of Divide coal leases within the permit area. Since these areas are being mined
together, it is logical to consider them together in one report. Most of the report is "as contained"
in the Exhibit 60B prepared by C. Richard Dunrud of Wright Waters Engineers, Inc. (WWE) in
March 2006 for the South of Divide mining area. Maximum projected mining was planned into
the Dry Fork mining area in E-seam longwall panels E2 to E6 to the east permit area boundary and
under the upper areas of Dry Fork, a tributary to Minnesota Creek, and the upper areas of Deep
Creek. Panels E1, E7, E8, and E15 through E17 remain within the boundaries of the South of
Divide mining area previously evaluated.
WWE further updated Exhibit 60E to reflect the maximum projected areal extent of potential
longwall mining within the potentially mineable coal reserves of the Dry Fork mining area. MCC’s
projected E-seam mining has not changed and continues to reflect the best available information
(including exploration and actual E-seam mining data) regarding the mineable E-seam coal.
However, during ongoing longwall panel development, additional mineable coal has been and may
be found to exist beyond the projected E-seam longwall panel shown on permit Map 51. If
mineable coal is found beyond the projected longwall panel and is within the Maximum Projected
Areal Extent area, MCC may continue mining within this area.
The 2015 update addressed a revised longwall panel layout in the two-seam mining area known as
the Apache Rocks West panels that was addressed in the original Exhibit 60 (May 1995). In
addition, the update evaluated the subsidence due to two-seam mining in the Southern Panels
mining area as shown in Figure 1. The 2018 update evaluated the subsidence associated with
longwall mining of the E-seam in the Sunset Trail mining area. WWE analyzed the proposed
layout for longwall panels SS1 through SS4 as shown in Figure 1. The 2020 update was performed