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CWDA No. 3 <br />#01349-0001 1"ruddicaon-Berry <br />01/11/16 `�; <br />Discussion of Vibrating Wire Piezometers <br />VWP-A DeeW <br />VWP-A Deep was installed on October 6, 2014 near the northern edge of CWDA No. 3. VWP- <br />A Deep was installed in the foundation soil approximately eight feet below the bottom of the <br />gob. The pore pressures recorded at VWP-A Deep generally decreased since installation until <br />September 2015. However, between September and December 2015, the pore pressures <br />increased slightly. In general, HBET does not believe that the pore pressure changes in VWP-A <br />Deep are cause for concern regarding stability of the gob pile. <br />VWP-A Shallow <br />VWP-A Shallow was installed on October 6, 2014 near the northern edge of CWDA No. 3. <br />VWP-A Shallow was installed approximately ten feet above the base of the gob. After <br />installation, the pore pressures dropped until November 2014. Between November 2014 and <br />September 2015, increases in the pore pressures were recorded at VWP-A Shallow. However, <br />between September and December 2015, the pore pressures decreased. The increases through <br />September 2015 likely reflect the active gob placement at CWDA No. 3 which has slowed down <br />since then. In general, HBET does not believe that the pore pressure changes in VWP-A <br />Shallow are an indication of instability in CWDA No. 3. <br />VWP-B DeeW <br />VWP-B Deep was installed on October 6, 2014 in the west -central portion of CWDA No. 3. <br />VWP-B Deep was installed in the foundation soil approximately ten feet below the bottom of the <br />gob. Since installation, the pore pressures recorded at VWP-B Deep have been fairly constant. <br />HBET does not believe that the pore pressure changes in VWP-B Deep are an indication of <br />instability in CWDA No. 3. <br />VWP-B Shallow <br />VWP-B Shallow was installed on October 6, 2014 in the west -central portion of CWDA No. 3. <br />VWP-B Shallow was installed approximately ten feet above the base of the gob. Since <br />installation, the pore pressures recorded at VWP-B Shallow have fluctuated with periods of <br />slight increase and slight decrease. Between March and September 2015, the pore pressures at <br />VWP-B Shallow increased. However, between September and December 2015, the pore <br />pressures decreased. The increases through September 2015 likely reflect the active gob <br />placement at CWDA No. 3 which has slowed down since then. In general, HBET does not <br />believe that the pore pressure changes in VWP-B Shallow are an indication of instability in <br />CWDA No. 3. <br />VWP-1) <br />VWP-D was installed on October 7, 2014 in the east -central portion of CWDA No. 3. VWP-D <br />was installed approximately ten feet above the base of the gob. Since installation, the pore <br />pressures recorded at VWP-D have fluctuated. However, there was a slight increase in pore <br />pressures between June and September 2015. Between September and December 2015, the pore <br />pressures again decreased. This likely reflects active gob placement at CWDA No. 3 during the <br />summer and early fall. In general, HBET does not believe that the pore pressure changes in <br />VWP-D are an indication of instability in CWDA No. 3. <br />X:A2008 ALL PROJECTS'01349 -Bowie Resources, LLCA01349-0001 Bowie MineA200 - GeoAGob 3'Instrumentation Monitoring'2015'01349-0001 GP3 4thQ 2015 LR011116.doc 2 <br />