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

-,, - 6 -
301 , L.S. Wood No.' 3 mine. Point TP-4 , which has subsided
• but is nearly stable (-0 . 06 feet of movement between Sep-
tember of 1984 and'„ August of 1985) , is located directly
ahead (north) of the longwall 301 tailgate; mining ceased
in early 1981. TP-2 , which has not subsided, is located
northwest of the headgate of the abandoned 301 face, and
MC-8 , which also has not subsided, is southwest of the
headgate entries 350 feet back from the face (exact loca-
tions are given below) . Using the same methods as above,
except that the elevation of the intersection of H with
the surface was taken from topographic maps, for TP-4 H is
`2 ,265 feet, angle 0 is 36 . 33 , and x is 340 feet, giving
an apparent angle of draw of 13 . 02 . For TP-2 , H is also
(by coincidence) 2 ,265 feet, 0 is 30 .450 and x equals 820
feet, for an apparent angle of draw of 25 . 97 . Finally,
for MC-8 , H is 2 ,530 feet, 0 equals 25 .57 , and x is 790
feet, for an apparent angle of draw of 20.99° From this
data 0it is cle$r that the actual angle of draw is between
13 . 0 and 21 . 0 .
In summary, adjacent to an active mining area, the angle of
draw appears to be approximately 16 .5 , in an area of tight
control . Adjacent to an area that has not been worked for
over 5 years and that now appears to be almost stable, where
data points are admittedly less concentrated, the angle of
draw is between 130 and 21° Given this information, it
would appear that the angle of draw stipulated by CMLRD is
too conservative . The actual angle of draw is probably in
the vicinity of 18° Using this angle, measurable subsidence
should be expected from 400 to 815 feet from the edge of
mined-out areas, assuming slopes angles from 0 to 450 and
an average depth of cover of 2 ,500 feet.
In conclusion, based on actual subsidence monitoring data
obtained since the baseline survey in 1981, the maximum verti-
cal subsidence above the Coal Basin underground workings
should not exceed 7 .2 feet. These data also indicate that
the actual angle of draw is approximately 18 , which could
result in measureable subsidence effects from 400 to 815
feet horizontally from the edge of mined-out areas.
4 . Description of damage or diminuation of reasonably fore-
seeable use of structures and renewable resource lands which
could result from subsidence. The only structures currently
located above mined-out areas consist of mine ventilation
fans and associated facilities, such as access roads and
power lines. All of these facilities are located above areas
mined out years ago (in most cases over 20 years) and assumed
to be stable. Most of these structures have been in place
for a number of years and no subsidence damage has been noted.
Other man-made features are limited to light-duty roads on the
surface, and the M bed mine workings over mined-out areas in
�t
the B bed. Given the apparent plastic yield of near-surface