2008-03-21_PERMIT FILE - C1980007A ‎(8)‎

• Permit No: C1980007A
• IBM Index Class Name: Permit File
• Doc Date: 3/21/2008
• Section_Exhibit Name: Exhibit 60E Subsidence Evaluation for the South of Divide & Dry Fork Mining Areas
• Media Type: D
• Archive: Yes

• 10.0 POTENTIAL IMPACTS OF SUBSIDENCE AND MINE-INDUCED
SEISMIC ACTIVITY ON LANDSLIDES AND ROCKFALLS
10.1 Landslides
The landslides listed below are all naturally occurring features, which become less stable, or
become unstable and slide, during periods of increased precipitation. A review of aerial
photographs of the Apache Rocks, Box Canyon, and South of Divide mining areas, which were
taken in 1963 and 2004, show that the slides listed below appeared to be more stable in 1963 than
they are now. Dunrud observed that many of the existing landslides during periods of high
precipitation were less stable, or became unstable and moved in the mid 1980s and mid 1990s.
The landslides in the southeast side of West Flatiron and on the west side of Deep Creek in the
Apache Rocks mining area showed no visual effects when longwall mining occurred beneath the
areas. It therefore seems apparent that wet seasons affect landslides more than does longwall
mining. During very wet periods, however, landslides that are already unstable may locally be
triggered by mine subsidence.
A total of twelve landslides, landslide areas, or landslide and rockfall areas, have been mapped in
the Apache Rocks, Box Canyon, and South of Divide mining areas during field mapping with the
U.S. Geological Survey (USGS) in the 1980s and also during the annual subsidence observations
in these areas (all the landslides listed in the Apache Rocks and Box Canyon mining areas occur in
Township 13 South, Range 90 West).
1. Apache Rocks mining area
a. Landslide located just north of Minnesota Reservoir in SWY4 of Section 29. No mining has
• occurred in the area.
b. Landslide area located above mined longwall panels 14 and 15 in NWY4 of Section 26.
These landslides appeared to be unaffected by longwall mining beneath them.
c. Landslide area located on the west side of Deep Creek, located above the southeastern part
of mined longwall panel 17 in the NWY4 of Section 35. This landslide also appeared to be
unaffected by mining below when observed in July 2003.
2. Box Canyon mining area (no mining had occurred when these landslides were last
observed):
a. Landslide and rockfall area located above mined longwall panel 22 and un-mined longwall
panel 23 in the NE% of Section 22 and the NW% of Section 23.
b. Landslide and rockfall area located above the southeastern part of un-mined longwall panel
21 in the NE% of Section 23.
c. Landslide area located above un-mined longwall panels 19, 20, and 21, on the east side of
Box Canyon in the W'/ of Section 14.
d. Landslide and rockfall area located above un-mined longwall panel 19 on the west side of
Box Canyon in the approximate center of Section 14.
e. Landslide located above un-mined longwall panel 18 on the east side of Box Canyon in the
NW% of Section14.
f. Extensive landslide area located south of the North Fork of the Gunnison River along State
Highway 133 in the SY2 of Sections 10, 11, and 12 and the N'/2 of Section 15.
•
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