2011-09-23_REPORT - C1980007 (8)

Home Browse Search

• • • Memorandum to Ryan Sweetwood and Kathy Welt August 2, 2010 (Revised February 1, 2011) Page 3 A review of the information summarized in Table 1 shows that the smallest angle of draw calculated is at Station 57 and the largest is at Station 101. However, survey information in the vicinity of Stations 37 and 57 are difficult to evaluate because there is no clear definition of the effects between the longwall panel extraction and development mining of the chain pillars. Therefore, these calculated values have less certainty than values calculated at Stations 10, 80 and 101. Excluding Stations 37 and 57 results in a mean angle of draw value of 16.3° and a range of 14.0 ° - 18.4 °. The predicted angle of draw for the E -seam presented in Exhibit 60E ranges from 15° to 17° and was based on the subsidence monitoring data from MCC's B -seam longwall mining. The E -seam subsidence data predominantly conforms to this predicted range with one exception (Station 101) at 18.4 °. All other data from the B -seam and E -seam show angles of draw less than the maximum predicted value of 17 °. Considering the measurement at Station 101, WWE recommends that the maximum predicted angle of draw for the E -seam be increased to 19° for the South of Divide and Dry Fork mining areas. Tom Kaldenbach of CDRMS asked that this be raised to 20° to "recognize the maximum angle of draw at a location may be greater than 18.4 degrees ". Z:\Project Files \72 -99 \831 -032 \831 -032.792\Engineering\Angle of Draw\Angle of Draw Memorandum 020211.docx