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• Response: There are three existing ditches and one culvert in the Pit 4 area. <br />The intermediate ditch, which runs east to west across the reclaimed area, <br />is not a designed component of the postmining drainage system and serves <br />only to prevent limited flow from the central pit area from crossing the small <br />undisturbed aspen grove at the west edge of the former shop area. Flows <br />from this ditch enter the southwest perimeter ditch, which in turn routes flows <br />to Pond 4. The intermediate ditch appears to be stable, with no evidence of <br />significant erosion or siltation. <br />The southwest perimeter ditch collects all disturbed area drainage from the <br />southern portion of the Pit 4 disturbance area, along with undisturbed area <br />drainage from the upper portion of the sub-watershed (Along the eastern <br />ridgeline) and the aspen grove on the west edge of the disturbance area. <br />Recent inspections noted some siltation in the upper reaches of this collection <br />ditch resulting from breaching of upgradient contour furrows. Rockcastie <br />• plans to repair the contour furrows and remove sediment accumulations from <br />the perimeter ditch. Given the level of vegetative reestablishment on the Pit <br />4 reclaimed area, these repairs should effectively prevent future build-up of <br />any significant sediment accumulations. <br />The inlet to Pond 4 from the southwest perimeter ditch (CMLRD designation <br />4C-1) is currently stable, with minor channel erosion having resulted in <br />establishment of natural armoring. In conjunction with required pond <br />mod cations, Rockcastle will regrade and reseed the inlet sideslopes to <br />repair minor erosion damage, and will place additional riprap as necessary <br />to supplement the existing natural armoring. <br />The northwest perimeter ditch collects all disturbed area runoff from the <br />northern portion of the Pit 4 disturbance area and a small amount of <br />undisturbed runoff from the upper portion of the sub-watershed (Along the <br />• eastern ridgeline). Flows from this ditch presently pass under the access <br />road to Pit 4 through a 36-inch culvert before discharging to Pond 4. <br />-4- <br />