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12. Response accepted. Since SCC has revised all postmine channel designs, the Division has the following comments regarding the new channel designs and culvert designs. a. The Pader method design for Channel PM-2 at both 11 % and 18% slopes indicates a D50: 6 inch riprap. Based on footnote 2) of Figure 20-1.2 4 (}2iprap D50 sized by taking the Pader Method Design size and doubling), the Lining Type given for PM-2 should be 12 inch as opposed to 9 inch. Please revise Figure No. 20-1.2 accordingly. b. The SEDCAD design provided for Culvert PM-12 is the same design information presented for PM-11. Please revise pages 13-7-243 through 13-7- 250 to include an appropriate SEDCAD demonstration and pipe size information for PM-12. 13-14. Items resolved. ] 5. Response accepted. However, it was noted that a stock tank designation was not included in the Legend of new Exhibit 20-2. Please add Stock Tanks to the Legend of Exhibit 20-2. 16. The Division did not intend for SCC to remove Section 6.0 (Post Mining Channels) of Attachment 13-SB Drainage and Sediment Control plan in its entirety. The Division simply intended for SCC to update Figure 1 of Section 6.0 with new and revised channel design information. This was accomplished with the submittal of new Figure 20-1.2 Postmine Channel Designs For South Area, which now appears in Attachment 20-1. The former Figure 1 of Section 6.0 was removed. What was lost in this transition was the commitment to providing a geotextile liner beneath the riprap in the Typical Channel Design. The geotextile liner as backing was part of the approved design, and the Division believes that this is an integral part of a stable channel design. The new Typical Postmine Channel Design (Figure 20-1.2) does not indicate use of a geotextile liner. If a geotextile liner is not used, then a granular filter blanket should be utilized. A granular filter blanket is preferable to a geotextile liner and serves two purposes. First, they protect the natural base from washing out through the riprap and, they provide "bedding" on which the riprap will rest. Please replace the text of Section 6.0, Attachment 13-SB and indicate on new Figure 20-1.2 (Typical Postmine Channel design) the type of backing to be utilized (geotextile/filter blanket). If an alternate design methodology is proposed please submit this information for review and design approval. 17. To demonstrate compliance with 4.05.9, please add embankment slope information to the Stock Tank designs (Exhibits 13-27.T25-T27).