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CWDA No. 2 <br />#01349 -0001 Huddleston -Bern <br />04/20/15 0Ll,., <br />Discussion of Inclinometer Monitoring <br />The latest inclinometer readings indicate no significant movements since the last quarterly <br />reading. <br />Vibrating Wire Piezometers <br />Between 2005 and 2012, a total of ten vibrating wire piezometers were installed in CWDA No. <br />2. However, several of the piezometers have been damaged or have otherwise ceased to <br />function. Currently, five of the piezometers are functional. <br />Monitoring of the functioning piezometers was completed by DOWL on March 1 It', 2015. The <br />attached monitoring report prepared by DOWL includes the piezometer monitoring data and the <br />data is summarized in the following table. <br />VWP ID <br />Initial Pore <br />Pressure <br />(psi) <br />1/6/15 Pore <br />Pressure <br />(psi) <br />03/11/15 Pore <br />Pressure <br />(psi) <br />Difference Since <br />Installation <br />(psi) <br />Difference <br />Since Last <br />Reading (psi) <br />VWP -05 <br />6.8 <br />2.3 <br />1.8 <br />-5.0 <br />-0.5 <br />VWP -06 <br />11.3 <br />16.8 <br />17.0 <br />+5.7 <br />+02 <br />VWP -08 <br />8.2 <br />9.8 <br />9.6 <br />+1.4 <br />-0.2 <br />VWP -09 <br />2.8 <br />3.0 <br />2.9 <br />+0.1 <br />-0.1 <br />VWP -10 <br />-1.9 <br />-1.7 <br />-1.8 <br />+0.1 <br />-0.1 <br />Discussion of Vibrating Wire Piezometers <br />VWP -05 <br />VWP -05 was installed on August 3, 2005 near the toe of CWDA No. 2 adjacent to the access <br />road/bench. The pore pressures recorded at VWP -05 have been slightly decreasing since the 3rd <br />Quarter 2014 monitoring. In general, HBET does not believe that the pore pressure changes in <br />VWP -05 are cause for concern regarding stability of the gob pile. <br />VWP -06 <br />VWP -06 was installed on June 5, 2009 near the existing top of CWDA No. 2. The pore <br />pressures recorded at VWP -06 have fluctuated since installation. The pore pressures increased <br />following installation until March 2013 and then fell until April 2014. However, between April <br />2014 and August 2014, the pore pressures again increased. This likely reflects the fact that gob <br />placement was occurring in the vicinity of this instrument during the spring and summer 2014. <br />There was a slight decrease between August 2014 and January 2015 which likely reflects the fact <br />that gob placement operations slowed and finally ceased for the winter. A slight increase was <br />reported between January 2015 and March 2015; however, the increase was small. In general, <br />HBET does not believe that the measured pore pressures are an indication of any instability in <br />CWDA No. 2. <br />VWP -08 <br />VWP -08 was installed on June 5, 2009 at a slightly lower elevation than VWP -06. The pore <br />pressures recorded at VWP -08 have fluctuated since installation. However, the fluctuations have <br />generally been within a narrow range of values. Slight pore pressure increases were recorded in <br />VWP -08 from April 2015 through January 2015. However, a slight increase occurred between <br />January and March 2015. As indicated in the referenced Stability Evaluation report, the stability <br />of CWDA No. 2 is sensitive to increases in pore pressures in VWP -08. An increase in the pore <br />pressure of 7 psi in VWP -08 would result in a reduction of the Factor of Safety to below 1.5. <br />X:\2008 ALL PROJECTS \01349 -Bowie Resources, LLC \01349 -0001 Bowie Mine\200 - Geo \Gob 2\Imtr ntation Monitoring\2015 \01349 -0001 GP2 LR042015.doe 2 <br />