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Sudan Burgmaier -8- June 12, 2014 <br />include the results of any additional laboratory testing that has been <br />conducted on coal mine waste at the Bowie No, 2 Mine. <br />B 2: Please see Appendix A of the HBET stability analysis, which includes the <br />most recent laboratory data conducted at gob pile #3. <br />b) For the native soil, an assumed � of 34 degrees was used. This value is not <br />consistent with the � of 30 degrees that was determined by Buckhorn in Mar -2007, <br />based on laboratory testing of on -site materials. Pleaseprovidejustification for <br />using a revised value for the angle of internal friction of native soil, or <br />revert to using the original value, <br />W2: Please see Section 4.2 of the HBET stability analysis, discusses the material <br />properties used in the analysis. <br />45. The third bullet in the Assumptions section of the 15 -Oct -2013 Buckhorn analysis refers <br />to piezometers at Gob Pile #3 that were monitored in June 2013 (no groundwater was <br />observed). The Mar -2007 Buckhorn report approved under TR -45 documents the <br />installation of seven standpipe piezometers in the footprint of Gob Pile #3. Based on <br />readings taken in Nov -2007, a phreatic surface was developed for use in the various <br />stability analyses. <br />a) Please expand the discussion of the groundwater phreatic surface to <br />address the condition of each ofthe piezometersinstalledin 2007, Which <br />of these piezometers have been disturbed or destroyed? Which, if any, <br />are still in use? What pi szometers were utilized in 2013? <br />B W2: Please see section 4.3 of the attached HBET stability analysis. <br />b) The current analysis fails to consider the effects (if any) of the sub - excavation of soil <br />from the footprint of the pile on the proximity of the phreatic surface. Please <br />expand the analysis to consider Buckhorn's original predicted location of <br />the groundwater phreatic surface (based on the seven standpipe <br />piezometers) and the approved additional excavation ofsoilmaterial from <br />the footprint of the pile, <br />B W2: Please see the attached section 4.3 of the HBET stability analysis. <br />