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Response to DBMS Adequacy Review(2)—Cotter-9 Mine Reclamation Plan Amendment <br /> minimum freeboard requirements. Please seethe revised Attachment for <br /> comments related to the Manning's n used. <br /> Given the wide range of possible Manning's "n" values used and the conservative <br /> approach of using worst case conditions in the analysis to determine the need for <br /> armoring or oversizing, we feel the original values and analyses were appropriate. <br /> c. Section 20-3. The one foot design berm height appears to meet the minimum <br /> freeboard requirements. However,please seethe revised Attachment A for <br /> comments related to the Manning's n used. <br /> Given the wide range of possible Manning's "n" values used and the conservative <br /> approach of using worst case conditions in the analysis to determine the need for <br /> armoring or oversizing,we feel the original values and analyses were appropriate. <br /> d. Please provide details or sections and analyses identified as missing or <br /> inadequate in the revised Attachment A. <br /> The additional channel segments suggested have been relocated, or added, and <br /> analyzed as requested. These can be seen on the drawings included in Attachment <br /> 4. Calculations for flow analysis can be found in Attachment 2. <br /> New Comments <br /> 12. Sheet 2 of 10. Some subbasin delineations have been revised since the 911212012 <br /> submittal. There are also additional existing and proposed channels that were not <br /> previously identified. Finally, the previously submitted subbasin Offsite 20 has been <br /> reduced in size and no longer adequately addresses the predicted runoff to the existing <br /> road ditch O(reference Sheet 3). The following items must be addressed to ensure the <br /> drainage plan is adequate: <br /> a. The missing subbasin (labeled 30C) contributing to the proposed retention pond <br /> 30, see Figure 1 below must be added to account for the runoff from this area to <br /> the pond. Adjustments will need to be made to spillway and chute design <br /> analyses. <br /> 6 <br />