PERMFILE43236

• Permit No: C1982056
• IBM Index Class Name: Permit File
• Doc Date: 12/11/2001
• Doc Name: Also Titled-Revised Subsidence Prediction for PR2
• Section_Exhibit Name: EXHIBIT 07d Analysis of Angle of Draw
• Media Type: D
• Archive: No

• 1.0 INTRODUCTION
The results of the existing subsidence data base were analyzed to develop asite-specific angle of draw
for the Foidel Creek Mine. The recommended site specific draw angle is 15 degrees.
Figure 1 shows the locations of the monitoring lines used in this anaysis. Figures 2 through 6 illustrate
the subsidence profiles used to calculate the angle of draw values. Table 1 summarizes the results of
this anatysis.
2.0 METHODOLOGY
Determination of the angle of draw correlates directty with the precision of the monitoring surveys. At
the Foidel Creek mine site, subsidence monitoring was performed to a precision of 0.5 ft. Therefore,
any subsidence value less than 0.5-ft is potentially the point of zero subsidence. The point of zero
subsidence was determined with a graphical method to compensate for the precision of the subsidence
monitoring surveys.
The graphical method was applied as follows:
1. The subsidence values determined from surveys before and after mining were plotted on
Figures 2 through 6 along with the locations of the corresponding solid coal ribsides.
2. Ysual inspections of the trends of the subsidence profiles were used to establish an estimated
point of zero subsidence. The point of zero subsidence is defined as the point where the
subsidence profile first begins an essentially horizontal, Anear trend.
3. The horizontal distance, d, between the point of zero subsidence and the corresponding ribside
was measured otf of the graphs.
4. The vertical distance, h, from the surface to the mining horizon was determined from an
• overburden map with a 50-ft contour interval.
5. The angle of draw, e, was calculated as:
e =Tan' (d / h)
8. The calculated angle of draw was rounded up to the next integer value.
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