Geology Reference
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FIGURE 6.1 Cross section of a hypothetical waste impoundment and geologic
features that control site stability. (A) Deeply penetrating tectonic fracture sets.
(B) Shallow, near-surface or stress-relief fracture zone. (C) Rock cut from
contour to supply a coarse blanket for bank stabilization and support. (D)
Mined out areas of an underground coal seam. (E) Roof collapse above mine
void, creating a zone of structural weakness. Modified from S.Greb, J.Dinger,
and D.Cumbie, Kentucky Geological Survey, personal communication, 2001.
adequate to prevent uncontrolled entry of water into the openings. The
strata in the aquitard must be identified and their thickness determined. This
must be done with site-specific investigations and rock-properties data. If
specific data cannot be obtained where longwall or other full extraction pillar
recovery has occurred, the surface fractured zone may be considered to be from
50 to 200 feet thick (Kipp and Dinger, 1987; Singh and Kendorski, 1981). The
permeable zone immediately above the openings may be 60
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