2007-11-30_REPORT - C1980007

• Permit No: C1980007
• IBM Index Class Name: REPORT
• Doc Date: 11/30/2007
• Doc Name: 2007 Fall Subsidence Report - Box Canyon, Apache Rocks, and South of the Divide Mining Areas
• From: West Elk
• To: DRMS
• Permit Index Doc Type: Subsidence Report
• Media Type: D
• Archive: No

Fall 2007 Subsidence and Geologic Field Observations
Box Canyon, Apache Rocks, and South of Divide Mining Areas
vertical displacement (subsidence) projected above the center of these mined longwall panels is
as much as 11.2 feet where 14 feet of coal is extracted. A maximum tilt of 6.4 percent also is
expected (see Table 2 and pages 4 and 5 of Appendix A for more details).
It is therefore important to obtain baseline measurements of the stream channel bottoms,
particularly the channel of Dry Fork, prior to mining. Survey measurements for the deepest part
of the Dry Fork stream bed (thalweg), from where the flume crosses Deep Creek to Minnesota
Reservoir, were completed this fall. This survey also includes the invert and outlet elevations on
all flumes and corrugated metal pipe culverts along this reach. This data, as presented in
Appendix C of this report, provides baseline data to assess vertical displacement and tilt (change
of slope) produced by future mining of the longwall panels in this area.
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831-032.780 Wright Water Engineers, Inc. Page 11
November 2007