1987-12-01_PERMIT FILE - C1981017 ‎(185)‎

• Permit No: C1981017
• IBM Index Class Name: PERMIT FILE
• Doc Date: 12/1/1987
• Doc Name: Air Pollution Control Plan
• Section_Exhibit Name: Chaper IV Section A
• Media Type: D
• Archive: No

Chapter IV
volume would be between 76 and 92 feet high. To compact and fill this volume to 90
percent of the original mass would result in a subsidence choke at heights between 760
and 920 feet. This height is much less than the average depth of cover, hence surface
subsidence will not occur. (See Appendix IV -F -3 for further discussion on the
subsidence bulking factor).
There are no indications of surface subsidence in Coal Basin even though there were
extensive mining operations for several years around the turn of the century and
continuously on a much larger scale since 1956. An on -site inspection of the most
likely area where subsidence could occur, above Nos. 1 and 2 mines, was conducted
on September 12, 1980 by two representatives of Willard Owens Associates, Inc., Mr.
John G. Roscoe, Mining Engineer; Ms. Nancy B. Lamm, Project Geologist; and
Mr.Douglas Bowman, Environmental Coordinator for Mid - Continent Resources, Inc.
They could find no evidence that the land area above these two mines had been
affected by subsidence (See Willard Owens Subsidence Inspection Report at Appendix
IV -F -1).
Based on four years of monitoring data, Dr. Collins' study reads as follows:
— Subsidence of the land surface over mined -out areas of
theCoal Basin mines has been detected by the
subsidence monitoring program initiated by MCR in
1981. Maximum subsidence detected to date is 2.10
feet, at a point now apparently stable (MC -4). This
amount of subsidence resulted from the extraction of at
least 8 feet of coal, and possibly as much as 16 feet
(see discussion in paragraph 3 above). There are no
visible surface effects of subsidence, such as cracks,
hummocked profiles or subsidence induced slumps or
landslides in the large portion of the area inspected for
such features. There has been no subsidence damage
to the few structures, primarily mine ventilation fans, or
to power lines or light -use roads located over mined -out
areas. There are no known aquifers above the coal
beds being mined in the area, and renewable resource
lands are restricted to small livestock and wildlife
summer grazing areas. Neither MCR, White River
National Forest (letter of 10/14/80) nor Gunnison
National Forest (letter of 9/1/80) plan any change of use
of the renewable resource lands, or any structures.
Therefore it is determined that subsidence that has
occurred has not resulted in material damage to or
diminution of reasonably foreseeable use of structures
or renewable resource lands.
— The very nature of the renewable resources identified
with the land above and within the areas of possible
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