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CWDA No. 3 <br />#01349 -0001 ;' Hudd[eston -Berry <br />04/20/15 �;'% ensmmsst� =ra�,u� <br />Discussion of Vibrating Wire Piezometers <br />VWP -A Deep <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. Since installation, the pore pressures recorded at VWP -A Deep have decreased. Due to the <br />limited time since installation, it is difficult to make any meaningful determinations regarding the <br />measured pore pressures and stability of the gob pile. However, HBET does not believe that the <br />pore pressure changes in VWP -A 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. However, since that time, slight <br />increases in the pore pressures have been recorded at VWP -A Shallow. Due to the limited time <br />since installation, it is difficult to make any meaningful determinations regarding the measured <br />pore pressures and stability of the gob pile. However, the increases in the pore pressures have <br />been small and HBET does not believe that the pore pressure changes in VWP -A Shallow are an <br />indication of instability in CWDA No. 3. <br />VWP -B Deep <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 />Due to the limited time since installation, it is difficult to make any meaningful determinations <br />regarding the measured pore pressures and stability of the gob pile. However, due to the fairly <br />constant nature of the readings, HBET does not have any concern regarding the measured pore <br />pressures and stability of the gob pile. <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 decreased slightly, increased <br />slightly, and then decreases slightly again. Due to the limited time since installation, it is <br />difficult to make any meaningful determinations regarding the measured pore pressures and <br />stability of the gob pile. However, the changes in pore pressure have been fairly small and HBET <br />does not believe that these changes are of sufficient magnitude to cause any concern regarding <br />the stability of the gob pile. <br />VWP -D <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 increased through December 2014. However, the pore pressures <br />have decrease since then. Due to the limited time since installation, it is difficult to make any <br />meaningful determinations regarding the measured pore pressures and stability of the gob pile. <br />However, the changes in pore pressure have been fairly small and HBET does not believe that <br />these changes are of sufficient magnitude to cause any concern regarding the stability of the gob <br />pile. <br />X:\2008 ALL PROJECTS \01349 -Bowie Resources, LLC \01349 -0001 Bowie Mine\200 - Geo \Gob 3\Imtr ntation Monitoring\2015 \01349 -0001 LR042015. doe 2 <br />