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<br />Memo to Erica Crosby <br />Bowie No. 1, TR-28 <br />page 2 <br /> <br />The proposed postmining reclaimed configuration, as depicted on Maps 6A-5N <br />("Postmining Contour Map") and 6A-50 ("Existing and Postmining Cross <br />Sections"), appear to me to reflect the original reclamation design intentions of <br />the approved Permit Application, specifically those design recommendations <br />within the Geo-Hydro Consultants stability analysis. The proposed <br />configurations adhere to the 2h:1 v maximum reclaimed slope gradients <br />recommended and analyzed within the original stability analysis. <br />I have only one concern regarding the proposed backfilled bench area reclaimed <br />configurations. Repeatedly within the Geo-Hydro Consultants stability analysis <br />the authors stated that the proposed backfilled configuration would <br />achieve a safety factor in excess of the regulatory requirement of <br />1.3 at a uniform 2h:1 v slope, providing that the fill is kept <br />effectively drained. I believe it is important to verify that this condition is <br />achieved during the reclamation of the Bowie No. 1 Mine surface facility area. <br />It will be important to carefully locate and construct the surface drainage <br />facilities to retard infiltration and saturation of the backfilled soil wedges. It <br />will be critical that ditches, such as the one occupying the narrowed bench <br />surface between the Shop Level and the Crushing & Screening Level benches be <br />well graded and sealed to prevent saturation of the adjacent downslope fill <br />wedge. <br />For this reason I recommend approval of the TR-28 proposed postmining <br />configuration with the following conditions. Particular care shall be exercised <br />in the location and construction of any drainage ditches in the immediate <br />upslope vicinity of backfilled areas. Existing location of properly performing <br />ditches shall be retained wherever practicable. Maximum possible grades shall <br />be maintained and care shall be exercised to render ditches as water tight as <br />possible. If appropriate, immediately upslope from large fill wedges, artificial <br />liners (membrane, gunnite or half round precast) might be used to seal the <br />critical ditches. In addition, Piezometers should be installed throughout the <br />entire thickness of the fill wedges within each of the significant backfilled soil <br />wedges, including the soil wedges located on the Crushing & Screening Level, <br />the eastern half of the Shop Level, the Portal Level, and the Fan Level. The <br />