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Huddleston-Berry <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, VWP -08, and VWP -09. The results of the sensitivity analyses indicate that <br />the stability of gob pile #2 at Section B -B' with the coverfill stockpiles is most sensitive <br />to changes in pore pressures in VWP -05. For Section B -B', an increase in pore pressure <br />of 4 psi, from 2.5 to 6.5 psi would result in a factor of safety of less than 1.5. However, <br />for Section C -C', an increase in pore pressure of 7 psi, from 2.9 to 9.9 psi in VWP -09 <br />would be required to reduce the factor of safety to less than 1.5. <br />With regard to VWP -08, an increase in the pore pressure of 9 psi, from 9.7 to 18.7 <br />psi would not reduce the factor -of- safety to less than 1.5 in either cross section. In <br />addition, an increase in the pore pressure in VWP -06 as much as 10 psi, from 17.1 to 27.1 <br />psi did not significantly reduce the factor -of- safety of gob pile #2 along either cross <br />section. <br />3.6 Conclusions <br />As indicated previously, the analyses indicated that the existing coverfill stockpile <br />has not adversely impacted the stability of gob pile #2. In addition, the proposed new <br />coverfill stockpile will not adversely impact the stability of gob pile #2. However, also <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 over the last few months. However, these increases <br />are likely due to active gob placement in the vicinity of these instruments and are much <br />lower than the values used in the sensitivity analyses. <br />At VWP -05 and VWP -09, the monitoring data indicate that the pore pressures <br />near the toe are fairly constant. While placement of new coverfill may cause slight <br />increases in pore pressures near the toe, HBET does not believe that the increases will be <br />sufficient to cause instability in gob pile #2. However, quarterly monitoring of the <br />piezometers is recommended to identify any significant changes in pore pressures which <br />may impact the 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 />X:\2008 ALL PROJECTS \01349 -Bowie Resources, LLC \01349 -0001 Bowie Mine\200 - Geo \Gob 2 \Cowrfill Stability\01349 -0001 R091914R2.doc <br />