2014-01-28_REVISION - C1981010 (2)

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permit revision. Given this, please revise the cost estimate associated with F Pit to account for the pit area that has not been granted Phase I bond release. Trapper Response to Comment 28: See explanation on item #27. 29. The current cost estimate includes a cost for re- grading the Z dip -Pit. This cost appears to be based on volumes derived from cross sections submitted and associated with PR6 and the current Map M6. The Z dip -Pit area associated with the current reclamation cost has not been Phase I bond released. The Division cannot release liability associated with backfilling and grading through the permit revision. Given this, please revise the cost estimate associated with Z -dip Pit to account for the pit area that has not been granted Phase I bond release. Trapper Response to Comment 29: See explanation on item #27. 30. The current cost estimate for the AE Pit is based on backfilling 879,238 cubic yards of material. The new estimate is based on a cost for backfilling 471,746 cubic yards of material. This is 407,492 cubic yards less than the current estimate. It does not appear area within AE Pit has been granted Phase I bond release. Please explain this large decrease in volume needed to backfill this pit. Trapper Response to Comment 30: In PR6, the Bond Estimate for East Ashmore pit (AE pit) involved the grading of the proposed cut # 49, which is approximately 550 ft. east of the cut (# 45) that presently exists in AE pit. At the time that PR6 was submitted, Trapper had more aggressive plans for the development of AE pit and therefore the worst case scenario for this pit was several cuts farther to the east than where it has been developed to date. At this time, there are no plans to advance AE pit beyond the existing cut (# 45) in the current 5 year permit term. Therefore, final grading for the existin cut was estimated and reported in the PR7 Bond Estimate. The cut that is addressed in PR6, requires a greater volume of backfill due to being located farther eastward (than the existing cut referenced in PR7). The greater overburden depths (i.e. higher strip ratio) associated with higher elevation terrain to the east, results in the higher grading volume. Even though the pit depicted in PR6 is shorter in length, the higher strip ratio in this location results in a larger pit void and larger quantity to backfill. As the depth of the cut increases, the surface disturbance (and resulting volume required to fill the pit) also increases. This is a function of the depth and highwall /lowwall slope angles. Thus, the backfill volume increases with depth in a nonlinear way (i.e., parabolically). Cut AE 45, represented in the current PR7 Bond calculations, is the current pit that exists in the field today, and is not as deep as the proposed cut estimated in PR6. This is the primary reason for the difference in AE pit backfill volume between PR6 and PR7. 31. The current cost estimate for the K and G Pits are based on backfilling 3,799,225 cubic yards of material. The new estimate is based on a cost for backfilling 2,169,306 cubic yards of material. This is 1,629,919 cubic yards less than the current estimate. It does not appear areas within K/G Pits has been granted Phase I bond release and it appears the majority of the projected worst case disturbance used to calculate the current backfill volume amount has occurred. Given that Phase I bond release has not been approved for K/G pit disturbance please explain this large decrease in volume needed to backfill this pit.