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Dan Mathews <br />Page 2 <br />Mazch 10, 2006 <br />16. The Division did not intend for SCC to remove Section 6.0 (Post Mining Channels) of <br />Attachment 13-SB Drainage and Sediment Control plan in its entirety. The Division simply <br />intended for SCC to update Figure 1 of Section 6.0 with new and revised channel design <br />information. This was accomplished with the submittal of new Figure ZO-1.2 Postmine <br />Channel Designs For South Area, which now appears in Attachment 20-1. The former <br />Figure 1 of Section 6.0 was removed. What was lost in this transition was the commitment <br />to providing a geotextile liner beneath the riprap in the Typical Channel Design. The <br />geotextile liner as backing was part of the approved design, and the Division believes that <br />this is an integral part of a stable channel design. The new Typical Postmine Channel <br />Design (Figure 20-1.2) does not indicate use of a geotextile liner. 1f a geotextile liner is not <br />used, then a granulaz filter blanket should be ufilized. A granulaz filter blanket is preferable <br />to a geotextile liner and serves two purposes. First, they protect the natural base from <br />washing out through the riprap and, they provide "bedding" on which the riprap will rest. <br />Please replace the text of Section 6.Q Attachment 13-SB and indicate on new Figure 20-1.2 <br />(Typical Postmine Channel design) the type of backing to be utilized (geotextile/filter <br />blanket). If an alternate design methodology is proposed please submit this information for <br />review and design approval. <br />17. To demonstrate compliance with 4.05.9, please add embankment slope infornation to the <br />Stock Tank designs (Exhibits 13-27.T25-T27). <br />Please let me know if you have any questions regazding my review of PR-OS adequacy responses <br />from SCC. <br />c: Sandy Brown <br />