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CWDA No. 2 <br />#01349-0001 <br />01/08/18 <br />X:\2008 ALL PROJECTS\01349 -Bowie Resources, LLC\01349-0001 Bowie Mine REVISED\200 - Geo\Gob 2\Instrumentation Monitoring\2017\01349-0001 GP2 4thQ 2017 L010818.doc 2 <br />Discussion of Inclinometer Monitoring <br />The latest inclinometer readings indicate no major movements since the last quarterly reading. <br />In general, the 4th Quarter 2017 monitoring data does not provide any indication of instability in <br />CWDA No. 2. <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 /> <br />Monitoring of the functioning piezometers was completed by DOWL on December 20th, 2017. <br />The attached monitoring report prepared by DOWL includes the piezometer monitoring data and <br />the data is summarized in the following table. <br /> <br />VWP ID Initial Pore <br />Pressure <br />(psi) <br />09/20/17 Pore <br />Pressure <br />(psi) <br />12/20/17 Pore <br />Pressure <br />(psi) <br />Difference Since <br />Installation <br />(psi) <br />Difference <br />Since Last <br />Reading (psi) <br />VWP-05 6.8 2.2 2.1 -4.7 -0.1 <br />VWP-06 11.3 13.2 13.0 +1.7 -0.2 <br />VWP-08 8.2 9.6 9.4 +1.2 -0.2 <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 /> <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 /> <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 /> <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 /> <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.