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situ vertical effective stresses anticipated for the ultimate waste bank. Failure was selected at <br />the maximum pore pressure for all samples. <br />Three points were tested for sample SH-1 (Borehole BG05-05 at 20-21.5 ft) at confining <br />pressures of 20, 40 and 80 psi. After consolidation, the samples were sheared at an <br />approximate rate of 0.003 in/min. The effective angle of internal friction, ~', was determined to <br />be approximately 34.3° with no cohesion. <br />Only enough sample was recovered from sample SH-2 (Borehole BG05-06 at 27.5-29.5 ft) for <br />two points. These two points were sheared at confining pressures of 40 and 80 psi. The <br />samples were sheared at an approximate strain rate of 0.003 in/min. The effective angle of <br />internal friction, ~', was determined to be approximately 33.6° with no cohesion. <br />Sample BS-3 consisted of three remolded points from a bulk sample of coal mine waste. The <br />three points were remolded to approximately 90% of the maximum dry density as determined <br />by the standard Proctor moisture contents of approximately 16.5%. These remold parameters <br />were intended to represent the lowest density that meets compaction specifications at a <br />relatively high moisture content. Sample BS-3 was consolidated at confining pressures of 20, <br />40, and 80 psi, and subsequently sheared at an approximate rate of 0.003 in/min. The <br />effective angle of internal friction, ~', was determined to be approximately 34.0° with no <br />cohesion. <br />The results of the CU triaxial shear testing are presented in Table 3. The effective friction <br />angles for the three tests are consistent for tests conducted on both remolded and thin-walled <br />samples. The average friction angle for the three CU triaxial tests is 34.0 degrees. <br />Table 3. Effective Strength Parameters <br />From CU Triaxial Testing <br /> <br />Sample Effective Stress <br />Parameters <br />i3oring <br />ID Sample <br />ID Depth <br />ft ~' <br />de . c' <br />BG05-05 SH-1 20-21.5 34.3 0 <br />BG05-06 SH-2 27.5-29.5 33.6 0 <br />N/A' BS-3 N At 34.0 0 <br />Average: 34.0 <br />NOTES: <br />1. Sample BS-3 remolded from bulk sample <br />5.0 UPDATED STABILITY EVALUATIONS <br />Stability evaluations of the Bowie CWDA No. 2 have been updated based on pore pressure <br />monitoring carried out over the past three years. Stability evaluations were conducted using <br />limit equilibrium methods and effective stress analysis. The following sections present the <br />revised stability evaluation. <br />• <br />Bowie No 2 2008 Reevalution of Coal Mine Waste Stability.doc <br />Project #OS-126-GEO <br />Page 8 of 15 <br />