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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 17, 2012 site <br />visit we were able to extract information at installations VWP -05, 06, 08, 09 and 10, which <br />provides good lateral representation of the coal waste in CDWA No. 2. <br />Pore pressures measured to date are presented on the attached figure. Pore pressures at VWP - <br />05, VWP -09 and VWP -10 were constant during the 3rd quarter 2012. Those reading are <br />consistent with consistent loading from new gob material at those sites and the readings <br />indicate generally stable conditions at those piezometer sites. Readings at these piezometers <br />have generally decreased since they were installed. This is a good indication that internal <br />drainage is occurring and that waste material is dewatering due to consolidation and trending <br />towards equilibrium. All measured pore pressures are well below the pore pressures at failure <br />for similar confining pressures for the CU triaxial shear tests that have been conducted as part <br />of the on -going stability evaluation for this refuse bank. Readings at VWP -06 and VWP -08, rose <br />slightly due to increased loading from additional wet coal waste being deposited on the <br />stockpile adjacent to those piezometers. The pore pressures, although slighted elevated, are <br />below the maximum pressures suitable to maintain stability. Therefore, there is no concern at <br />this time and we would anticipate those pressures to decrease as the waste material de- waters <br />over time. <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 />Closing <br />On -going monitoring of inclinometers and piezometers at CWDA No. 2 provides an indication of <br />the stability of the refuse as well as an indication of probable performance for other refuse piles <br />at Bowie. For these reasons, we recommend continued monitoring of this instrumentation on a <br />quarterly basis. We sincerely appreciate the opportunity to work with you on this project. If <br />you have any questions regarding this letter or the instrumentation monitoring at CWDA No. 2, <br />please don't hesitate to contact me at (970) 497 -8852 or dan0buckhorngeo.com. <br />3rd Qtr Monitoring Report.doc <br />Project #05- 126 -GEO <br />Page 2 of 3 <br />