2010-04-16_PERMIT FILE - C1996083

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• 3.2 Far -Field Horizontal Stress The USBM researchers measured the far -field horizontal stress in the Bowie No. 1 mine using the overcoring technique in roof rocks. These measurements were obtained at two locations at the Orchard Valley Mine (Bickel 1993). More recently, another measurement was completed in the Bowie No 2 mine using the same technique. Both sets of measurements are consistent and reliable and thus provide a good estimate of far -field horizontal stress in the vicinity of the Terror Creek. Table 1 provides a summary of these measurements. Table 1— Far -field measured horizontal stress in the BRL properties. Site Depth of cover, Max stress (P), psi Min stress (Q), Orientation of ft psi P 1 (Orchard 340 1,100 240 N 69 E Valley) 2 (Orchard 1625 1,630 480 N 83 E Valley) 3 (D Seam, 1,000 1,330 245 N 85 W Bowie No. 2) Overall trend N 80° to 90° E Regional measurements show excess horizontal stress in the Somerset Coal Field along the regional structural trend (N 74° to 80° E). Horizontal stress is only gravity induced along the secondary direction (N 10° W). The excess stress is moderate, but increases with depth (table 1). The far -field horizontal stress is very anisotropic in this basin. The ratio of maximum to minimum secondary principal horizontal stress (P /Q ratio) is approximately 4 to 6 (Maleki and others 1997). The orientation of maximum principal stress is consistent, trending east -west near BRL properties. It is possible that some stress reorientation may be found near stream valleys. To estimate premining horizontal stress at the Terror Creek we have utilized the existing measurements of shallow cover conditions at site 1 while accounting for variations in topography using the results of measurements and modeling by the USBM (Molinda and Maleki Technologies, Inc. Page 12