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May 1992 <br />Rockcastle Coal Company • Grassy Creek Mine ~ 2 <br />• 4) Whaz equipment will be used to construct diuhes with bottom widths of 2.0-3.5 ft? <br />Response: Given the relatively rugged terrain and the desire to minimize disturbance <br />related to equipment access, Rockcastle proposes to use a tratxor-mounted backhoe for <br />construction of smaller ditches. <br />S) Ponds 4 and 5/6, if approved to be left as permanent, will require as-built cenifuation when <br />completed <br />Response: Rockcastle has proposed specific modifications to Ponds 4 and 5/6 in order <br />to address existing impoundment concerns and meet applicable permanent impoundment <br />design/construction criteria. It is anticipated that, upon receipt of required Division <br />approvals, modification work could be initiated, with completion projected during the <br />1992 construction season. Both during and on completion of pond modifications, the <br />ponds and associated structures will be inspected and as-built drawings, showing final <br />impoundment configurations will be developed and certified. <br />6J In the permanent pond demonsrration for Pond 4 it is stated that the emergenry spillway will <br />be lowered to 7545.2 ft, yez design plans show the zop of the 10-year, 24-hour event cresting <br />at 7547. S ft. Lowering the elevation of the emergenry spillway would not allow for rreatment <br />of the required 10-year, 24-hour event. An alternative would be to add a riser to the principle <br />spillway at 7545.2 ft. which would allow the pond to dewater to the 2 acre ft limit, yet <br />maintaining the proper elevation for the open channel emergency spillway, and retain most <br />of the detention time for the 10-year, 24-hour event please provide revised plan details which <br />• satisfy both the water rights issue and compliance with Rules 4.05.6 and 4.04.9. <br />Response: Appendix D, Sedimentation Pond Retention/Reclamation, reflected <br />Rockcastle's proposal to complete specific modifications to Pond 4 consistent with <br />backsloping plans and retention of the pond as a sedimentation structure during the <br />reclamation liability period. This proposal also reflected removal of the riser structure, <br />installation of a gated decant on the remaining outlet culvert, and lowering of the <br />emergenry spillway to limit storage capacity to less than 2 acre-feet. These modifications <br />would be completed at the end of the bond liability period to in order meet applicable <br />permanent impoundment requirements. <br />The Division's suggestion, to cut an additional orifice at the design permanent storage <br />level, which would remain plugged until the end of the reclamation liability period, <br />minimizes future work requirements and appears to be a more practical option. Inherent <br />in this approach is the idea that the existing lower orifice would be plugged to maintain <br />impoundment storage capacity and the new upper orifice would function to dewater any <br />storm runoff or accumulated storage greater than the maximum storage capacity of 2 <br />acre-feet. Rockcastle accepts the Division's suggestion and has revised appropriate pages <br />of Appendices A and D and Map R-3 to reflex this change. Revised documentation <br />accompanies these responses for replacement in the correspondence files. <br />7) There were no SEDCAD runs for Pit S drainage srructures depicting the 2S-year, 24•hour <br />event, other zhan a cover page. Please provide these calculations. <br />• <br />~~,,.~~ <br />os~v~ ~ <br />