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

7 -
rocks and surface materials, and considering the total
• absence of visual subsidence effects, such as cracks or -
hummocked profiles,, no detectable damage to the roads is
expected. The company will take into account the magnitude
and nature of subsidence and subsidence-related phenomena
observed since 1981 in the future design and construction
of surface and other facilities over recently mined-out
workings or planned extraction areas. Subsidence-related
interaction between M and B bed workings has been noted.
In the B bed interaction has been limited to roof control
difficulties and accelerated bottom heave in the Main
Slopes of the No. 3 mine as a result of the extraction of
longwall panels 201, 202 and 203 in the overlying M bed.
In the M bed workings of the No. 2 mine, roof control
difficulties, rib instability, and generally minor bottom
heave, accompanied in isolated areas by severe "bounces;
or violent stress-release events, have been noted over
barrier pillars left between panels or between slopes and
longwall panel startlines in the B bed below. Mining con-
ditions in the M bed over mined-out B bed areas are gener-
ally excellent, even better than in areas where the under-
lying B bed has not been mired, indicating substantial
stress release in the B bed subsidence zones. In the
future, MCR intends to superimpose development entries and
longwall and room and pillar areas to the extent possible
in order to avoid high-stress areas (barriers and other
pillars) and to take advantage of destressed areas. .
No surface effects of subsidence, such as cracks or hummocked
profiles, or subsidence-induced slumps or landslides have
been observed in spite of nearly 30 years of mining activi-
ties in the area, including 8 years of longwall mining.
While measureable deformation of the surface has occurred,
failure of near-surface rocks and surficial materials is
plastic. Therefore no damage to or diminuation of the
limited grazing areas is expected. No change in surface
use is anticipated by the surface owner (USFS correspondence,
9/16/80 and 10/14/80) . There are no known bedrock aquifers
above the coal-bearing rocks. There are only short reaches
of perennial streams in the area of interest, near the
extreme southwestern boundary; in these areas, bedrock is
fairly close to the surface, and alluvial fill in the stream
valleys is minimal. In addition, the alluvial materials
present consist mostly of low-tranmissivity clays and weath-
ered shale materials, with little in the way of porous gravel .
Again, no surface cracks or abrupt changes in surface topog-
raphy have been noted, indicating plastic surface and near-
surface deformation. Therefore, no damage to or diminuation
of aquifer recharge areas, whether bedrock or alluvial , is
anticipated.
. The only aquifers in the area that would affect regional
groundwater hydrology would be those in the Williams Fork