PERMFILE114489

• Permit No: C1982056
• IBM Index Class Name: Permit File
• Doc Date: 12/11/2001
• Section_Exhibit Name: EXHIBIT 07e-1 Northern Mining District Subsidence Report
• Media Type: D
• Archive: No

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SubTerra, Inc. ~ IG . Tw~tymde C al Company III IIIIIIIIIIIII III
Northem Mining District Subsidence ses
Doc Date:12/11/2001
1. Introduction
Cyprus Twentymile Coal Company (CTCC) is currently preparing the detailed mining plans for
the first 5 panels in their Northem mining District at the Twentymile coal mine. This report
contains an estimate of the subsidence that will occur during mining of the first five panels in
the Northem Mining District.
The Payout of the mine workings and surface features is shown on Drawing 1. Mining will
include extraction of 5, 840 ft wide longwall panels separated by 160 ft wide, 3-entry,
submains.
2. Subsidence Prediction
Cyprus' Twentymile Coal Company (CTCC) has developed an extensive subsidence database
from monitoring longwall panel extraction in the West, Southwest, and Eastern mining districts.
This data has been submitted to the Division of Mines and Geology in semi-annual subsidence
reports and in reports attached to permit documents (e.g., SubTen'a, Inc., 1992, 1993).
TCC has supplemented these published data with results from monitoring the county road,
power lines, and the Energy Spur track which crosses both the Eastem and Northem mining
districts.
The process of incorporating these data in the current predictions is described in the following
paragraphs:
1. Transverse profile data for Panel 9-Right (northernmost panel in the Eastem Mining
District) have been used to predict subsidence for the first panel in the NMD, Panel
12-Right. These data are contained in Table 1 and Figure 1.
2. Time phased data from the initial surveys of Panels 1, 2, and 3 in the Western
Mining District (Subsidence Line 12000E), representing the surface response to the
first, second, and third panel extraction, have been used to predict the effects of 13-
Right, and subsequent panel, extraction. These data are contained in the semi-
annual reports and in SubTerra, Inc., 1993.
3. Subsidence over the rigid-yield pillars separating adjacent longwall panels was ~
estimated using the data from monitoring line 4000 in the Fish Creek study area
(panels 1 LLW and 2LLW). These data are contained in the semi-annual reports
(CTCC, 1994) and in SubTerra, Inc., 1993.
4. The start profile for Panel 15-Right was estimated using data from monitoring lines
1000 and 3000 in the Fish Creek study area (panels 1 LLW and 2LLW). These data
are contained in the semi-annual reports (CTCC, 1994) and in SubTerra, Inc., 1993.
Subsidence predictions were made for overburden thickness of 1,100 and 1,400 ft
representing the range of conditions in the study area. The results of these predictions are
contained in Figures 2 and 3. Summary data include:
• Maximum subsidence of 56 and 62 inches for overburden thickness of 1,400 and
• 1,100 ft, respectively.
APPROVED APR 2 0 1998
-___. P-R 97-04 EX. 7E-1-1 4/1/97