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readings. The previous movement in the B -axis of BH05 -05 is interpreted to be due to <br />settlement of the coal refuse. <br />Vibrating Wire Piezometers <br />Five vibrating wire piezometers, designated VWP -01 through VWP -05, were installed in coal <br />refuse at CWDA No. 2 in June 2005. The piezometers were grouted in drilled boreholes as <br />described by BGI (2006). Piezometer locations are presented on the attached site plan. Since <br />installation two of the vibrating wire piezometers have stopped working correctly (VWP -01 and <br />VWP -04). Diagnostic tests indicate that shorts have developed, likely due to damaged cables. <br />Three additional vibrating wire piezometers, designated VWP -06 through VWP -08, were <br />installed at CWDA No. 2 in June 2009 to supplement the remaining piezometers. Completion <br />details of these piezometers are described by BGI (2009). During the September 22, 2011 site <br />we were able to extract information at installations VWP -05, 06 and 08. All other vibrating wire <br />piezometers have been damaged beyond readability and an we recommend that they be <br />repaired or re- installed prior to our next quarterly instrumentation readings to maintain <br />continuity of measurements in those locations. <br />Pore pressures measured to date are presented on the attached figure. Pore pressures at all <br />three remaining workable piezometers increased slightly between the June 2011 and September <br />2011 readings. Those reading are consistent with increased loading from new gob material at <br />those sites and the increases are within an acceptable range based on the increased loads. <br />Readings at all three piezometers have generally decreased since they were installed. This is a <br />good indication that internal drainage is occurring and that waste material is dewatering due to <br />consolidation and trending towards equilibrium. All measured pore pressures are well below the <br />pore pressures at failure for similar confining pressures for the CU triaxial shear tests that have <br />been conducted as part of the on -going stability evaluation for this refuse bank. <br />Pore pressures are anticipated to continue to decrease as drainage occurs. In any event, on- <br />going monitoring of all piezometers is recommended to monitor pore pressure responses to the <br />on -going refuse placement. Otherwise, the measured pore pressures are consistent with the <br />revised stability evaluation for the coal refuse performed by BGI (2008). <br />Bowie Gob Pile 2 Instrumentation Monitoring 3rd Qtr 2011.doc <br />Project #05- 126 -GEO <br />Page 2 of 4 <br />