1987-12-01_PERMIT FILE - C1981017 ‎(284)‎

• Permit No: C1981017
• IBM Index Class Name: PERMIT FILE
• Doc Date: 12/1/1987
• Doc Name: Subsidence Study By Dr. Bruce Collins
• Section_Exhibit Name: Chapter IV Appendix IV-F-4
• Media Type: D
• Archive: No

9 -
change of use of structures or renewable resource lands.
. Therefore it is determined that subsidence that has occurred
has not resulted in material damage to or diminuation of
reasonably foreseeable use of structures or renewable
resource lands.
6. Subsidence monitoring program. A subsidence monitoring
program was initiated by MCR in 1981 . Subsequent surveys
were carried out in 1982 , 1983 , 1984 and 1985 in accordance
with this plan (Vol . 7 , Chapter IV, pages 33-37) and subse-
quent revisions. The results of this program are summarized
below. MCR contends that sufficient data have been collected
to characterize subsidence and subsidence-related phenomena
in the Coal Basin area, i.e. that the subsidence ratio of
measured disturbance to coal thickness removed is approxi-
mately 0. 30, substantially less than the ratio of 0.55 as
predicted in the permit; that the angle of draw averages
approximately 18° as opposed to the CMLRD stipulated value
of 20. 59 and that there are no visually observable effects of
subsidence, such as surface cracks, hummocked profiles (sub-
sidence pits) , or subsidence-induced slumps or landslides.
There has been no observable damage to structures or other
man-made facilities such as roads or power lines over mined-
out areas, in spite of nearly 30 years of mining activities,
including 8 years of longwall mining, which results in
essentially total extraction of the full thickness of the
• coal bed involved over wide areas, or to renewable resource
lands or aquifer recharge areas. There are no significant
variations in the. general geology of the area that would
indicate that subsidence or subsidence-related phenomena will
differ in the future from what has been observed to date.
There is likewise no evidence, based on data accumulated to
date, that any damage due to subsidence or subsidence-related
phenomena will occur to structures, renewable resource lands
or. aquifer recharge areas in the future.
Because of the extremely rugged topography and severe climate
of the Coal Basin area, which limit dependable access to sub-
sidence monitoring and control points to between July and
September and in addition require helicopter-supported sur-
veying, the subsidence monitoring program is very costly.
Since data accumulated to date indicate that both the subsid-
ence ratio and the angle of draw are less than the worst
case predictions contained in the permit application, because
no visual effects of subsidence have been observed in spite
of the 30-year period during which mining activities have been
carried out in Coal Basin, and because there is no evidence
of damage to or diminuation of structures, renewable resource
lands or acquife.r recharge areas, or to foreseeable use of
structures or renewable resource lands , MCR requests suspension
of the subsidence monitoring program.
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