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Response to DBMS General Stormwater Comments — Cotter JD -9 Mine Drainage Design Plan <br />The 72" culvert and embankment will be removed following approval of the <br />amendment application. <br />d. The embankment through which this culvert conveys stormwater is not <br />designated as a road to remain in place after reclamation. As this drainage is <br />expected to experience significant stormwater flows, this embankment and <br />culvert should be removed to complete reclamation. Please revise the <br />reclamation plan and map to reflect the removal of the embankment and culvert. <br />See response to "c" above. <br />7. Pages ESWMP -48 and 49, NOAA Atlas Charts. These two charts are illegible at the scale <br />provided and appear to be identical based on the isopluvial patterns. Please state <br />explicitly the rainfall depths used for the 10 year and 100 year, 24 -hour design storms as <br />this information is not provided in the Pond Pack computer output. <br />The design storm precipitation depths used in the analysis for this site are 1.9 inches and 3.0 <br />inches, respectively, for the 10 -year and 100 -year, 24 -hour events. This information was <br />taken from the NOAA Atlas 2, Volume III isopluvial charts. <br />DPP Drawings: <br />8. Sheet 3 of 7. Please label additional channel segments analyzed as a result of Comment 3 <br />above. <br />Additional channel segments analyzed as requested are labeled on the drawings included in <br />Attachment 5. <br />9. Sheet 4 of 7. No spillway or low level outlet is provided for the retention pond. Please <br />provide spillway location, designs (sections and profile), and specifications sufficient to <br />convey the design flow to the toe of the embankment. <br />Spillway details and location are provided in the revised drawings included in Attachment 5 <br />of this document. <br />10. Sheets S and 6 of 7. No water surface (W. S.) elevations or velocities are provided for <br />these sections. The slopes are suspect. Please see Attachment A. <br />a. Please provide water surface (W. S.) elevations for each section or eliminate <br />reference, indicating FlowMaster results are appropriate. <br />Water surface elevations are included on the revised drawings in Attachment 5 and <br />the calculations can be seen on the worksheets in Attachment 3. <br />5 <br />