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PERMFILE108142
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PERMFILE108142
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Last modified
8/24/2016 10:00:36 PM
Creation date
11/24/2007 4:19:47 PM
Metadata
Fields
Template:
DRMS Permit Index
Permit No
C1980007A
IBM Index Class Name
Permit File
Doc Date
6/6/2003
Doc Name
pages 2.05-84 to 2.05-166
Section_Exhibit Name
2.05 Operation & Reclamation Part 2
Media Type
D
Archive
Yes
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West Elk Mine <br />Box Canyon mining areas, there is latitude to develop the most efficient layout and method to <br />recover a maximum amount of the coal resource with a minimum of impact. <br />Strength and behavioral Dronerties ofthe rocks -These properties may control the amount and rate <br />of subsidence. Strong, brittle sandstones and siltstones tend to break and cave in large blocks on the <br />mine floor. The bulking factor is greater for strong rocks than it is for soft, weak rocks. The greater <br />bulking factor of strong, caved material commonly reduces the height of caving and the subsidence <br />factor over soft, weak rocks. Conversely, the height of fracturing often is greater for strong, brittle <br />rocks than it is for soft, weak rocks. <br />I~~ <br />Stratieraphic sequence -The stratigraphic distribution of rock units (stratigraphic sequence) <br />influences the effects of mining and subsidence. For example, strong and brittle sandstones in the <br />mine roof, as discussed above, can reduce the height of caving compared to shales, whereas <br />sandstones in the fractured zone above the caved zone may increase the height of fracturing <br />compared to shales. <br />In addition, the subsidence factor may be less where the overburden contains a greater proportion of <br />thick, strong sandstones compared to thin,. weak shales. A unit that may reduce the subsidence <br />factor is the locally thick Lower and Upper Marine Sandstones that underlie the D and E-Seams. <br />These sandstones aze about 100 feet thick in the eastern panel azea and the eastern part of the <br />western panels of the Apache Rocks mining area; they aze approximately 100 to 125 feet thick in <br />the Box Canyon mining azea and the northwestempart of the current West Elk Mine azea. <br />Moisture content -Wet or saturated conditions in the mine roof and overburden tend to reduce the <br />bulking factor of the caved roof rocks. Therefore, the subsidence factor commonly is greater under <br />wet conditions than it is in dry conditions. In general, the greater the saturation of the mine roof and <br />overburden rocks, the greater the subsidence factor. <br />Subsidence Prediction Based on Loca[ Mining Experience - 2.05.6 (6) (e) (i) (C) <br />Much infortation has been gathered regarding subsidence at the West Elk Mine due to local <br />mining of the F-Seam (room-and-pillar method) and B-Seam (longwall method). Subsidence <br />monitoring of a grid network has been conducted from 1985 to 1998, and has provided <br />considerable data regarding the effects of varying overburden thicknesses, mining heights, and <br />mining methods on the subsidence network. The grid has also verified MCC's predicted <br />subsidence and established when subsidence occurs, where it occurs, and when it is complete. <br />The grid demonstrated, in regazd to longwall mining, that the majority of the subsidence was <br />seen within the fast year after mining, and in most cases subsidence was completed within one <br />year to a year and-a-half. This information and its usefulness in predicting subsidence <br />parameters in the adjacent Apache Rocks and Box Canyon mining area is detailed in the <br />following section: In addition, some general observations obtained from the West Elk Mine <br />and neighboring mining operations are described below. <br />2.05-111 Revisedhm. 1995 PR06; 1196 RN03; Revised May 1944 7889: RevisedJan. 1998 PROS <br />
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