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CWDA No.2 ,��'E <br /> #01349-0001 Huddleston-Berry <br /> 1 0/16/19 � fiz Engineering&Testing,LLC <br /> .=-LQCJSJv <br /> Discussion of Inclinometer Monitoring <br /> The last two inclinometer readings show deflection in BG05-5. However, the deflection is <br /> perpendicular to the slope direction. As a result, HBET does not believe that the reported <br /> deflection is an indication of instability. However, the 4th Quarter data will provide additional <br /> information for evaluation. No significant movements were reported for the other inclinometers. <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 September 3 Oth, 2019. 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 Initial Pore 06/14/19 Pore 09/30/19 Pore Difference Since Difference <br /> Pressure Pressure Pressure Installation Since Last <br /> (psi) (psi) (psi) (psi) Reading(psi) <br /> VWP-05 6.8 1.5 1.9 -4.9 +0.4 <br /> VWP-06 11.3 12.2 12.0 +0.7 -0.2 <br /> VWP-08 8.2 8.9 8.8 +0.6 -0.1 <br /> VWP-09 2.8 2.8 2.8 0.0 0.0 <br /> VWP-10 -1.9 -1.8 -1.8 +0.1 0.0 <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 shown some seasonal fluctuations; <br /> however, the range of pore pressure changes is fairly small. In general, HBET does not believe <br /> that the pore pressures in 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. In general, the fluctuations <br /> have been seasonal and reflect the level of coal mine waste placement activity on top of CWDA <br /> No. 2. In general, HBET does not believe that the measured pore pressures are an indication of <br /> any instability in 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. The measured pore pressures are generally <br /> consistent with the level of coal mine waste placement activity at CWDA No. 2. <br /> As indicated in the referenced Stability Evaluation report, the stability of CWDA No. 2 is <br /> sensitive to increases in pore pressures in VWP-08. An increase in the pore pressure of 7 psi in <br /> VWP-08 would result in a reduction of the Factor of Safety to below 1.5. <br /> Z:\2008 ALL PROJECTS\01349-Bowie Resources,LLC\01349-0001 Bowie Mine REVISED\200-Geo\Gob 2\Instrumentation Monitoring\2019\01349-0001 GP2 3rdQ 2019 L101619.doc 2 <br />