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17. DRMS: The Division has no further concerns with this question. The first design run was <br />removed in the May 26, 2011 submittal. However, the Division has additional questions <br />concerning culverts and ditches. <br />a) The Sedcad hydrology design for Channel -1 consists of one ditch design page that is <br />located at the back of Appendix 2.05.3(3) -1, "Sedcad Runs for Culverts ". Please include <br />additional design pages that show how the peak discharge for Channel -1 was obtained, <br />as was done for the other ditches. Also, in order to avoid any confusion, please consider <br />moving the channel -1 Sedcad run pages to a more appropriate section, such as <br />Appendix 2.05.3(4) -2, "Sedcad Runs for Pond and Diversions ". Also, please consider <br />adding Channel -1 to Table 4: Ditch Design Parameters on page 7 of Appendix <br />2.05.3(4) -1, "Arcadis Report on Sediment Control ". <br />Response — Revised SEDCAD runs have been included for Channel -1 in Appendix <br />2.05.3(3) -1. Since the work was not performed by Arcadis, it is not included in Table <br />4. Sedcad runs under Appendix 2.05.3(3) -1 were performed by WFC staff and thus <br />are included separately from the Sedcad runs performed by Arcadis that are included <br />in Appendix 2.05.3(4) -2. <br />b) In Appendix 2.05.3(3) -1, "Sedcad Runs for Culverts ", there are Sedcad design sheets <br />for culvert C -1 that use a peak discharge of 4.78 cfs and a culvert diameter of 18 inches. <br />These parameters also appear in the Culvert Table on Map 2.05.3(3) -1 for that culvert. <br />However, directly after those design pages is one design page for culvert C -1 that uses a <br />peak discharge of 51.82 cfs. Please explain. <br />Response — The design page showing 51.82 cfs was inserted in error and has been <br />removed. <br />c) The Culvert Table on Map 2.05.3(3) -1 states that the subwatersheds for culvert C -13 <br />are SW1 -B and SW -FA. However, referring to Map 2.05.3(3) -1, it appears that the <br />subwatersheds should be SW -1C and SW -FA. If this is correct, please revise the Sedcad <br />designs and the Culvert Table on Map 2.05.3(3) -1 for culvert C -13. <br />Response — Map 2.05.3(3) -1 Surface Water Hydrology has now been labeled as Map <br />2.05.3(4) -1 Surface Water Hydrology. SEDCAD designs and Culvert Table in Map <br />2.05.3(4) -1 have been revised to show correct subwatersheds. <br />d) Please add the D50 riprap size of 6 inches for ditch NHN -002 South w /Riprap to Table <br />4: Ditch Design Parameters on page 7 of Appendix 2.05.3(4) -1, "Arcadis Report on <br />Sediment Control ". <br />Response — D5O riprap size of 6 inches has been recommended for ditch NHN -002 South <br />where the ditch channel slope exceeds 2 %. <br />19. DRMS: In the May 26, 2011 submittal cover letter, Western Fuels explained the <br />justification for using the curve number but did not revise any text since the culvert was <br />not in the mine's disturbed area. The Division's question could have been worded better. <br />The justification for the curve number of 91, used in the Sedcad design runs for all mine <br />Page 19 <br />