2016-02-25_PERMIT FILE - C1982056A ‎(6)‎

• Permit No: C1982056A
• IBM Index Class Name: Permit File
• Doc Date: 2/25/2016
• Section_Exhibit Name: Exhibit 7K Wolf Creek Reserve Subsidence Evaluation
• Media Type: D
• Archive: Yes

SubTerra, Inc. Peabody Twentymile Coal, LLC 03/16/2015
Foidel Creek Mine
Permit Revision for Longwall Mining in the Wolf Creek Seam - Subsidence Evaluation
4. Evaluation of Potential Impacts to County Road 33
This section of the report presents the results of our evaluation of subsidence along County Road 33
due to mining the Wolf Creek Seam Panels 1 -East through 5 -East. The layout of the Wolf Creek
Seam extractions in relation to County Road 33 is shown on Drawings 7 and 8.
4.1. Scope of Work
The scope of work included evaluating the potential effects of subsidence on County Road 33. Tasks
included:
• Estimating the magnitude of subsidence effects on County Road 33.
• Evaluating the potential for impacts including surface cracking.
4.2. Approach
This phase of remedial planning followed the process used to evaluate impacts from Wadge Seam
mining. The overall approach included:
1. Adding road elevation data to the spreadsheet for the length of CR33 that would be affected.
2. Estimating the subsidence for each panel extraction. These estimates are presented in both
tabular and graphical form.
3. Evaluating the potential for surface cracking based on anticipated subsidence and strains.
Our approach utilized one large, integrated spreadsheet to model maximum and transient subsidence
displacements at predetermined locations (or Stations) along the road alignment for each of the
planned longwall panels. The starting road elevations for Stations were determined from a
topographic map supplemented by a survey by Twentymile Coal, LLC.
4.3. Subsidence Prediction
Several panels in the Wadge Seam have previously undermined County Road 33 in the Northern
Mining District. Subsidence data, obtained from surveys of ground stations conducted during these
periods of undermining, were previously used to check the initial predictions and this will again be
done during undermining by the Wolf Creek Seam panels.
Table 2 and Figure 7 show the predicted subsidence profile along County Road 33 due to sequentially
mining panels 5 -East through 1 -East. Maximum subsidence effects without remediation are estimated
at:
1. Maximum subsidence of 77 -inches where CR33 crosses over the shallower panels.
2. Maximum slope change of 1.0%.
3. Maximum tensile strain of 0.005.
These predicted impacts will likely require patching to seal surface cracks where the road is founded
on the Twentymile Sandstone.
9 P N : 2013-26