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<br /> <br />Mr: Brent Anderson - 2 - April 24, 1991 <br /> <br />Rule 3,03 and 34-33-125 both indicate that the applicant must include <br />"a description of the results achieved .. ". It is the Division's <br />opinion and policy that topographic mapping and cross-sections are the <br />appropriate descriptions for backfilling and grading results, There is <br />no substitute for the mapping. Therefore, we reiterate our request that <br />topographic mapping and cross-sections or AOC slope analysis be provided <br />for Pits 5 and 6. <br />Rock castle has amended the map to include permit and disturbance <br />boundaries, title block, and professional certification. As an aside, it <br />is apparent that the topography depicted in Pits 5 and 6 on the map <br />Reclaimed Topo~raQhy 1990 is not reclaimed topography. Therefore, the <br />cer i~ica~ion is ~n error. <br />The Division does not agree that theoretical drainage modeling is <br />incompatible with site specific remediation measures. Prudent, site <br />specific hydraulic designs require the use of careful topographic <br />mapping. It is also not apparent that the designs found in Attachment 2 <br />are the worst case. <br />T, The Pit 5 prainage Remediation Plan calls for the mixing of undisturbed <br />and reclaimed area drainage. This is acceptable if the drainage <br />structures are sized to handle the runoff from these areas. Please <br />• ensure that your mapping includes the entire drainage above Pit 5 and <br />documents the entire extent of the disturbed area (pit and stockpile <br />areas). In addition, re-evaluate the acreages noted on-F'igure 1 of <br />Attachment 2, Acreages shown for the Pit 5 ditches are vastly <br />underestimated. <br />2. The Division is unable to accept the general concept behind the Pit 5 <br />Drainage Remediation Plan until we have a certified post-mining <br />topography map. The Division is very concerned about the steep slopes <br />along the north perimeter ditch and west of the access road and on the <br />west edge of the disturbed area. It is the Division's preference that <br />Rockcastle armor drainageways through the steep slopes on the north and <br />south central portions of the pit perimeter. <br />3. Provide calculations to document that the reconstructed natural <br />drainageway (No. 1) can handle the 100-year 24-hour event. ~ <br />4, Commit to removal of the diversion ditch on the northeast end of Pit 5 <br />and provide quantitative documentation tied to a 10-year 24-hour event <br />that the surrounding area qualifies as a small area exemption per <br />IV(4)(a) and Rule 4.05.2(3). <br />5, All permanent drainageways at the site must be designed and constructed <br />to handle the 100-year 24-hour event, per Rule 4.05.4(2)(1), Revise the <br />ditch, riprap and culvert calculations to reflect this sizing. <br />r1 <br />U <br />