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`�� Huddle.tnn•8ern <br />None of the shear strength testing shows a drained friction angle as low as 30 °. <br />HBET does not believe that this value is representative of the gob and as a result, <br />sensitivity analyses using this value is not warranted. However, for conservatism, HBET <br />conducted sensitivity analyses considering a drained friction angle of 32 °. The results <br />indicate that Gob Pile #2 at both cross sections will still have a factor -of- safety above 1.5 <br />Pore Pressures <br />With regard to sensitivity of the analyses to changes in pore pressures, the <br />piezometeric surface was changed by adjusting the pore pressures in piezometers VWP - <br />05, VWP -06, and VWP -08. The results of the sensitivity analyses indicate that the <br />stability of gob pile #2 with the coverfill stockpiles is most sensitive to changes in pore <br />pressures in VWP -05. For both Sections A -A' and 13-13% an increase in pore pressure of <br />4 psi (equivalent to approximately 9 feet of head) would result in a factor of safety of less <br />than 1.5. However, an increase in the pore pressure in VWP -08 of 9 psi (equivalent to <br />approximately 21 feet of head) would not reduce the factor -of- safety to less than 1.5 in <br />either cross section. In addition, an increase in the pore pressure in VWP -06 as much as <br />10 psi (equivalent to approximately 22 feet of head) did not significantly reduce the <br />factor -of- safety of gob pile #2 along either cross section. <br />3.6 Conclusions <br />As indicated previously, the analyses indicated that the placement of coverfill <br />stockpiles on gob pile #2 will not adversely impact the stability of gob pile #2. However, <br />as indicated previously, changes in the pore water pressures could affect the stability. <br />The referenced monitoring data does indicate slight increases in the pore <br />pressures of VWP -06 and VWP -08. However, these increases are likely due to active <br />gob placement in the vicinity of these instruments and are much lower than the values <br />used in the sensitivity analyses. <br />At VWP -05, the monitoring data indicate that the pore pressures near the toe are <br />fairly constant. While placement of coverfill near the toe may cause slight increases in <br />pore pressures at the toe, HBET does not believe that the increases will be sufficient to <br />cause instability in gob pile #2. However, quarterly monitoring of the piezometers is <br />recommended to identify any significant changes in pore pressures which may impact the <br />stability of gob pile #2. <br />4.0 GENERAL <br />This conclusions, results, etc. in this report is based upon the information in the <br />referenced documents, current analyses, and on our experience with similar projects. The <br />conclusions are valid only for the subject project. <br />Huddleston -Berry Engineering and Testing, LLC is pleased to be of service to <br />your project. Please contact us if you have any questions or comments regarding the <br />contents of this report. <br />X ~2008 ALL PROJECTS 01349 -Bowe Resources, LLC 01349.0001 Bos.ie Mine'200 - Geo'Gob 2'Co.'erfill Stability 01349.1N101 R091914 doc 5 <br />