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Reclamation of the Moffat Area included efforts to achieve a similar • density of shallow drainages in the postmining topography as existed prior to mining. A field review of the Moffat area indicated that the premining drainage basins did not exhibit defined drainage channels in the upper reaches of the basins and only marginal channel development occurred along the downslope portions of the ridge. As such, drainages based on design flow events to direct overland flow along the upper portions of the hillslope were not performed. It is anticipated that the reconstructed drainage basins in the upper reaches of the hillside will direct overland flow toward the more defined drainage system which exists at the westerly edge of the Moffat Area. Should concentrated flow channels begin to ~. develop in the upper reaches of the postmining drainage basins,, appropriate ~ control techniques will be implemented to minimize erosion. The techniques -' to control erosion in the reconstructed draws in the lower reaches of the hillside and in the upper reaches if _cha_nn_els develop. may include, but_are not limited to, designed flow channels, riprap, filter cloth, haybale checkdams, water bars, silt fences, matting and netting. Exhibit 3.4-5 provides several cross-sections which extend across the full length of the Moffat area. A review of these cross-sections indicates that f}ve drainage basins existed on the lower hillslope in the premining environment with two • of the basins being in close proximity to each other and in the immediate vicinity of the final pit. ,F.oyr-drainaoe basins exist on the lower hillslope in the postmining environment. The single large drainage basin constructed by the reclamation of the final pit encompasses the area previously occupied by the two smaller premining basins which were in close proximity to each other.-~ A total of six esigned drainage structures were proposed for the lower slops of the Moffat Area. These drainage channels are depicted on Exhibit 3.4-6. Desig4~ specifications for Moffat Downdrain #1 and #2 are V t ~ provided in Appendix 3.5-D. Design specifications for the South Collection Ditch are provided in Table 4.6-11. Design specifications for the three remaining drainage channels are provided in Appendix 3.9-B. Moffat Downdrain #3 and approximately 500 feet of the South Co lection Ditch are the only drainage structures which as proposed varied from the premining drainage characteristics. Downdrain #3 will be intersected by a proposed postmining road. At the intersection with the proposed road, the drainage will be directed across the slope in the road ditch and conveyed to the Moffat impoundment via the Moffat Downdrain #1 and the South Collection Ditch. This drainage pathway is designed to be supportive of the water rights appropriation £or the Moffat permanent impoundment. Additionally, • to accommodate a request from the CDMG, the riprap Dso to be used in Renewal-3 3.4-3 June 13, 1997