2011-01-25_REPORT - C1980007 - Laserfiche WebLink

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Memorandum to Kathy Welt January 25, 2011 Page 2 WWE believes that this accounts for the vertical distance value difference between those cited in the CDRMS letter and those in the August 2, 2010 WWE memorandum. WWE believes the methodology used and explained in our August 2010 memorandum is correct and consistent with the description of draw angle cited by the National Coal Board and other sources (see Figures A and B of Appendix A of the Spring 2010 Subsidence and Geologic Field Observations report). As such, we have recalculated the angle of draw for each of the five stations using the revised horizontal distances for Stations 10, 57, and 80 as noted above. A revised Table 1 is provided to reflect these updated calculations for angle of draw at the various panel edges. TABLE 1 Angle of Draw Calculations Monument Grid Used Horizontal Distance (feet) Vertical Distance (feet) Angle of Draw W Station 10 340 1240 15.3 Station 37 340 1360 14.0 Station 57 290 1150 14.2 Station 80 290 1150 14.2 Station 101 380 1320 16.0° Figure 1 is attached with this memorandum as further support for the numbers cited in Table 1. As stated in the August 2010 memorandum to MCC, WWE believes that Station 101 should be considered to have the greatest weight in evaluation of the E -seam draw angle in the South of Divide mining area. By doubly- weighting the draw angle for Station 101, a computed arithmetic mean for the data represented in Table 1 is 14.95 This is consistent with the conclusion of 15 reached by WWE in our August 2010 memorandum. Attachment: Table 1 — SOD E -Seam Grid and Overburden cc: Jonathan Kelly, WWE Z:\Project Files \72 - 99\831- 032 \831- 032.792\Engineering\Angle ofDraw\Response to CDRMS Commetits.docx