PERMFILE103730

• Permit No: C1980007
• IBM Index Class Name: Revision
• Doc Date: 12/2/2004
• Doc Name: 2.05.5 Post-Mining Land Uses
• Type & Sequence: PR10
• Media Type: D
• Archive: No

West Elk Mine
percent) where 12 feet of coal is mined, and from 0.013 to 0.064 (1.3 to 6.4 percent)
where a 14-foot thickness of coal is mined.
• Panel E9. Maximum tilt is this panel is predicted to range from 0.034 to 0.044 (3.4 and
4.4 percent), where 12 feet of coal is mined and from 0.039 to 0.052 (3.9 to 5.2 percent)
where 14 feet of coal is produced.
Maximum Horizontal Strain
Maximum positive horizontal strain (Em) measured in the West Elk Mine monitoring
network ranges from 1.1 to 1.4'(S,„/d) (0.0058 to 0.0102, that is 0.58 and 1.0 percent);
maximum negative strain between -0.20 and -4.0 times (Sm/d) (or 0.0009 and 0.0307, that is
0.09 to 3.0 percent) (Table 1 of Exhibit 60B}. The range of horizontal tensile strain in four
different mine areas of the Western United States studied by Mr. Dunrud is 0.45 to 3 (Sm/d).
Maximum tensile and compressive strain is significantly greater above large barrier pillars
and rigid chain pillars and mine boundaries than it is above longwall mining faces. This is
because tensile strains caused by mining the two adjacent panels are additive above the
common rigid chain pillars or unyielding mine panel boundary pillars. Cracks tend to be
wider and deeper above barrier pillars or lease boundary barrier pillars than chain pillars
because of their greater rigidity {for example, the large tension crack on the north side of
Lone Pine Gulch).
. The tensile strains presented in Exhibit 60B (Figure 4) are believed to be conservative for the
South of Divide mining area. Maximum horizontal tensile strains, measured by Mr. Dunrud in
bedrock during annual observations in the Apache Rocks area (in hazd brittle sandstone, where
the only strain is revealed by cracks), were 0.0031 to 0.0062 (0.31 to 0.62 percent). The tensile
strain is considered to be close to a maximum value For those observed by Mr. Dunrud in the
Apache rocks azea because (1) the features aze located above the area if influence of a large solid
coal pillaz and (2) no greater strain was observed in the Apache Rocks mining area.
Apache Rocks Mining Area -The horizontal tensile strain in the eastern panels after B Seam mining
is projected to range from 0.003 on the south flank of West Flatiron (overburden depth is about
2,250 feet) to 0.013 (units aze dimensionless [L2]) neaz the head of Sylvester Gulch
Projected horizontal tensile strain for the western panels for E Seam mining are 0.008 above the
thickest overburden on the ridges to 0.023 above the thinnest overburden in Horse Gulch. Tensile
strain after both E and B Seam mining is completed may range from about 0.016 to 0.041 above
thickest and thinnest overburden, respectively.
Projected horizontal compressive strain will be in the panel centers. In the eastern panel area, using
an average value of 2.0 (Sm/d) from the West Ells Mine subsidence network, compressive strain is
projected to range from -0.004 neaz the south flank of West Flatiron to -0.020 near the head of
Sylvester Gulch. Compressive strain above the western panels after E Seam mining is estimated to
range from -0.013 in azeas of thickest overburden to -0.035 in azeas of thinnest overburden. After
mining both the E and B Seams, compressive strain is estimated to range from -0.025 to -0.062 in
thickness for thickest and thinnest overburden, respectively.
2.05-1 / 1 Revised November 2004 PR/0