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Brock Bowles <br />Page 3 <br />May 26, 2015 <br />Several drainages within the RSDA Borrow Area are depicted on Map Exhibit 6C. The <br />cross section of these drainages is depicted on Exhibit 26. The Division could not locate <br />the model results used to design these structures in Appendix 13-2. In accordance with <br />Rule 4.05.3(1)(e) these structures need to be designed, located, constructed and <br />maintained and used to minimize adverse impacts to the hydrologic balance. It is unclear <br />if these drainages have been designed in accordance with Rule 4.05.3(7). Please submit <br />results of the model used to design these drainages in accordance with Rule 4.05.3(7). <br />For the North Portal, the Western Diversion Ditch and Eastern Diversion Ditches are <br />depicted on Exhibit 8C. Cross sections of these diversions are also depicted on Exhibit <br />8C. The designs for these ditches are included in Appendix 13-2. The cross sections <br />provided in Appendix 13-2 and Exhibit 8C are different for these ditches. Please clarify <br />which ditch design was used to construct the Western Diversion Ditch and Eastern <br />Diversion Ditch. <br />4.05.4(1)44) Stream Channel Diversions (Relocation of Streams) and Stream Channel <br />Reconstruction <br />A review of the permit regarding stream channel diversions and stream channel reconstruction <br />was conducted. Review of permanent diversions found at the site is discussed in section <br />4.05.3(1)-(7) and 2.05.4(4)(d) above. It appears one channel in the North Decline area has been <br />constructed and the Coal Canyon drainage channel was realigned. A discussion of each area is <br />below. <br />A permanent channel is designed for the North Decline, the channel reestablishment calculations <br />are given in Appendix 13-2. The channel appears to be designed in accordance with Rule <br />4.05.3(1)(b -f), (7). According to the page 40 of the RN6 Findings Document, "The North <br />Decline had been constructed prior to the Act so accurate records of pre mine contours do not <br />exist. The final reclaimed contours blend with landforms observed in the undisturbed <br />surrounding landscape. The drainage channel of the unnamed drainage was reestablished through <br />the regraded area and riprapped with 12 inch or greater riprap on the 7.5 percent slope areas and 6 <br />inches or greater on the 2.5 percent grades". No issues were identified. <br />As part of the design for CRDA 2, the Coal Canyon drainage channel was realigned to provide a more <br />uniform controlled flow between CRDA 1 and 2. According to the RN6 Findings document, the <br />drainage channel was graded to an approximate uniform grade to the cross sections presented on <br />Exhibits 53 and 55 of the permit document. These exhibits are located in Volume 4, Tab 13 of <br />the permit. No issues were identified. <br />-No adequacy review issues were identified for this section. <br />