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3.2 Inclinometers <br />Three inclinometers, designated BG05-4, BG05-5, and BG05-7, were installed within the CWDA <br />No. 2 in August 2005. The inclinometers were installed along the bench in the waste bank <br />located approximately 50 feet above the toe of the waste bank. Locations of the inclinometers <br />are presented in Table 2 and on Drawing 1 (Appendix A). The inclinometers were installed <br />through the coal mine waste and approximately 20 feet into the native foundation soils. <br />Table 2. Inclinometer Locations <br />Borehole/ <br />Inclinometer ID <br />Northing <br />Easting <br />BG05-04 19094 37985 <br />BG05-05 18991 37824 <br />BG05-07 18980 37494 <br />Baseline readings were taken shortly after installation and subsequent readings have been <br />taken on roughly a quarterly basis. Cumulative displacement plots for each inclinometer are <br />presented in Appendix B. The A-Axis shows deformation with depth in the direction of <br />anticipated movement, while the B-Axis is orthogonal to Axis A. Displacements indicated on the <br />plots for the upper ten feet of the inclinometers occurred just after placement of cover soil on <br />the face of the waste bank in late 2006/early 2007 and are attributed to disturbance of the <br />inclinometer surface casings by equipment and/or cover soil placement. . <br />Other than the movement attributed to cover soil placement, no indications of deep-seated <br />slope failures are indicated by the inclinometers. Minor movement is indicated at inclinometer <br />BG05-05. These movements are approximately 0.25 inch in the A-axis and up to 0.5 inch in the <br />B-axis. These movements are interpreted to be due to settlement of the coal waste. The <br />deformations do not show a discrete failure surface, but appear like creep-type movement. <br />Also, the majority of the indicated movement is parallel to the slope of the waste bank (rather <br />than down the slope of the waste bank). We recommend continued monitoring of the <br />inclinometers on a quarterly basis. <br />4.0 SUMMARY OF PREVIOUS STRENGTH TESTING <br />Shear strength of coal mine waste at Bowie has been characterized by three consolidated <br />undrained (CU) triaxial shear tests with pore pressure measurement and by several <br />unconsolidated undrained (UU) triaxial tests. These samples were collected by BGI in 2005 and <br />are described in detail by BGI (2006). The results from the CU triaxial shear tests are <br />summarized in this section and the test results are presented again in Appendix C of this report. <br />The UU triaxial shear test results are not applicable to the updated stability evaluations <br />presented in this report, and are therefore not presented. <br />Two of the CU triaxial shear tests were conducted on thin-walled (Shelby tube) samples (SH-1 <br />. and SH-2) of previously placed coal mine waste, while one sample (BS-3) was conducted on <br />• remolded samples. Confining pressures for the CU triaxial tests were selected to span the in- <br />Bowie No 2 2008 Reevalution of Coal Mine Waste Stability.doc <br />Project #OS-126-GEO <br />Page 7 of 15 <br />