ENFORCE21661

• Permit No: C1981013
• IBM Index Class Name: Enforcement
• Doc Name: WRIGHT WATER ENGINEERS EXHIBIT A-U
• Violation No.: CV2000009
• Media Type: D
• Archive: No

Rebuttal Report to Gerity Expert Report of February 2001
35 degrees. It is our understanding that the Tatum residence may be located very close to the
zone where the angle of draw would encolmter the surface" Even with that incorrect
information, his cazefully hedged statement was: "Given the possible closeness of the mine
workings and the timing of mining; in our opinion mine subsidence provides a reasonable
explanation for the damage that has been observed."
9.0 ERRONEOUS INPUT TO GERITY'S COMPUTER MODEL&
Mr. Gerity (in the last pazagraph of page 9) correctly states that "When a pillar fails by punching
into the mine floor, the material from the floor expands to fill the mine entries azound the
pillars." He then erroneously states that "The maximum amount of space available to subside,
for that model, would be on the order of 3 feet fora 6 foot thick coal scam." This could be true
if the thine has extracted 50 percent of the coal. However, the mine only extracted 33.34 percern
of the coal. Therefore, since one cannot create space underground except by mining, Ute void
space to be filled cannot exceed the 33.34 percent of the coal. Total maximum underground
subsidence, therefore, must be limited to 33.34 percent of the 6-foot coal seam, which would be
2 feet. This reduces possible maximum subsurface subsidence by one-third.
The Tatum subsidence cw-ve shown on Figttre T-3 of Appendix 2 is incorrect. It would be
considerably different if the maximum subsidence were limited to 2 feet instead of the 3.8 feet
Mr. Gerity used. Likewise, the input data shown on Figure T-1 would provide a different curve
if the subsidence for points 1, 2. and 3 (which are, respectively, 3.861, 3.237 and 2.530 feet)
were limited to 2 feet.
Mr. Gerity (on pages 4 and 5 and in Appendix 7) has established that the August 1993 restuvey
is more accurate than the July ] 993 survey. Yet data on page 16 shows that be used the less-
accurate .470 feet instead of the more-accurate 3.40 feet for point 14 (1N-2) and the less-accurate
.352 feet instead of the more accurate 0.130 feet for point 3 (1N-1).
Wr[ght water Engineer, Inc. -4- 001-161.000
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