2008-12-09_PERMIT FILE - C1996083A ‎(3)‎

• Permit No: C1996083A
• IBM Index Class Name: Permit File
• Doc Date: 12/9/2008
• Doc Name: pg 2.05-59 to 2.05-126
• Section_Exhibit Name: 2.05 Operation and Reclamation Plans Part 2
• Media Type: D
• Archive: Yes

• 2.05.6(6)
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As explained in Exhibit 15, Section 1.6, data from the Bowie No. 1 Mine and
field measurements of subsidence cracks in the Mesaverde Formation by
Dunrud (1976), indicate subsidence cracks may develop through overburden
thicknesses of up to 800 feet under unfavorable conditions. While
unfavorable conditions can not be defined exactly, they may include zones of
weathered coal and overburden. Under normal conditions, subsidence
cracks do not appear likely to propagate through more than 500 feet of
overburden.
The permit area has been segregated into three zones of expected
subsidence impact. The zone of greatest subsidence impact is in areas
where the overburden is between 110 and 500 feet. The zone of
intermediate subsidence impact is in areas where the overburden is between
500 and 1,000 feet. The zone of minor subsidence impact is in areas where
the overburden is over 1,000 feet. Map 27, Subsidence, presents the
locations of these three zones. The discussion in Volume IIIA, Exhibit 15
Subsidence concludes that under normal conditions, subsidence cracks do
not appear likely to propagate through more than 500 feet of overburden.
Overburden thicknesses over 800 feet have been classified as having a
negligible risk of surface fracturing developing. This is a conservative upper
limit under normal conditions.
A table at the end of this section presents a listing of springs ponds and
water rights. The table presents the elevation of each feature and the
estimated depth each lies above the coal seam to be mined. Generally no
subsidence protection will be provided for springs unless they are a decreed
water right and only then if the spring has an overburden depth of less than
800 feet. Most of the springs and ponds within the permit boundary and
adjacent area have overburden depths which exceed 800 feet.
A limited extraction zone as referenced below is defined as an area in which,
if mined, will be limited to first mining only with no pillar slabbing. The
proposed location of the limited extraction zones are presented on Map 27,
Subsidence and Maps 14 & 14B, Mine Plans.
2.05 - 112 - 11 /08