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Michael Boulay May 21-2008 <br />CAM: Both Drainage basins are in fact D-6, they tie together below the design <br />point for C-7. <br />34. DRMS: For analysis of material that will comprise the Coal Mine Waste <br />pile, the geotechnical consultant had access to only a small stockpile from which <br />to collect samples. Consequently, the stability analyses conducted may not <br />represent the potential variability in coal mine waste that may occur as the pile is <br />constructed. In order to validate the findings and factors of safety reported, <br />additional testing of physical properties should be conducted from the additional <br />volumes of waste that have accumulated subsequent to the original sampling. If <br />these test results [i.e. gradations, Atterberg limits, and moisture/density (Proctor) <br />curves] bear close resemblance to those achieved for the original samples <br />collected, then no additional testing and analysis may be warranted. However, if <br />it becomes apparent that the coal mine waste is quite variable in composition, <br />further analyses may be required. <br />Please obtain additional samples from the mine bench and sediment <br />storage stockpiles, and from pond and ditch sediments, with separate <br />samples for materials having visually differing physical characteristics, and <br />provide test results for these additional samples, consistent with the <br />original testing performed by Buckhorn Geotech. Please provide an <br />updated stability analysis, as appropriate, based on the additional test <br />results. <br />CAM: Text has been added to page 2-27i addressing the DRMS's comments. <br />In general, the Operator will perform another stability analysis of the coal mine <br />waste pile with site specific strength parameters for the coal mine waste after five <br />feet of fill have been placed in the pile. <br />35. DRMS: Recommendation No. 4 of the Appendix "R" Stability Evaluation <br />states that the gob pile should be designed and graded to shed surface water <br />and precipitation off all portions of the pile both during and after gob placement. <br />Applicable regulations specify diversion of surface drainage from above the <br />waste bank and from the crest and face of the waste disposal area (4.10.3(2)), <br />and further specify that drainage shall not be directed over the outslope of the fill <br />(4.09.2(5)). Based on design grades and ditch locations depicted on Figure 2.2-3 <br />topography and cross sections, it appears that the final pile configuration would <br />comply with the referenced rules and stability evaluation recommendation. <br />However, it is not clear from design figures or narrative how compliance with the <br />drainage requirements will be maintained during interim stages of waste pile <br />construction (to divert runoff from above the pile and from the pile surface to <br />stabilized drainages off the fill, prevent runoff from being directed over the <br />outslope, and to prevent ponding on the fill). Demonstration of compliance will <br />likely require grade specifications for completed lifts, and may require use of a <br />14