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• Response: The watershed areas were reviewed and revised as appropriate and drainage and ditch sizing calculations have been revised to reflect corrected watershed deliniations. Watershed areas are shown on Map 3211, Drainage and Sediment Control Plan, and design calculations aze provided for insertion in Appendix B. Please see accompanying revisions. 30. Based on Figure 4.1, it appears that the undisturbed area above the West [/alley Fill, but below the upland diversion, will drain to the refuse pile collection ditches. This being the case, the collection ditches will also serve as a diversion for the pile, and so should be designed for the 100- year, 24-hour event. Response: Inclusion of the drainage calculations for the 2-, 25-, and 100-year design storm events in Appendix B co the WESTEC Report may be the source of confusion regarding the storm event utilized in the design of the West Valley Fill collection ditches. As referenced on pages 5 and 10 and documented by the drainage design calculations presented in Appendix B, both the upland diversion and the runoff control ditches for the Wesc Valley Fill are designed to safely pass the peak flows resulting from the 100-year, 24-hour design storm event. This design approach is consistent with applicable regulatory requirements of Rules 4.10 and 4.09 For drainage ditches for permanent refuse fill structures. 31. 7Tie upland diversion ditch over the West [/alley Fill is shown differently on several small scale maps, so it is difficult to determine exactly where the constructed ditch initiates (east) and terminates (westJ. Please provide a small scale map ojthe ditch location which clearly indicates where the ditch starts and ends, so the DMG can verify the adequary of the ditch design. • Response: After reviewing the DMG's comments and field considerations relative to construction of the upland diversion, the upland diversion was shifred downhill (below a resistant sandstone outcrop) and shortened to discharge to the first west drainage. The Drainage and Sediment Control Plan Map, Map 3211, has been revised and now shows the entire upland diversion. Please see accompanying revisions. 32. Map E-3211 indicates the west end of the upland diversion ditch flows to the Second Drainage. /f the ditch will actually end where the rymbol ends, flow will be overland through an undisturbed area before it reaches the drainage. Please either clarify that the ditch will be constructed until it intersects the drainage, or provide a plan for routing flows form the ditch to the drainage. Response: Please refer to previous Response 31. The upland diversion has been shifted and will follow the contour at a grade of approximately -2 percent. The ditch will extend to and intersect the existing natural flow channel in the first ephemeral drainage (beyond the West Vally Fill) to the west of Elk Creek as shown on Map 3211, Drainage and Sediment Control Plan. The angle of intersection will be minimized and appropriate channel armoring will be placed ac and downgradient from the point of intersection to minimize the potential for erosion due to changes in flow energy. Please see accompanying revisions. 33. Please provide additional information which will demonstrate that Second Drainage is capable ojcarrying the additional flow from the upland diversion ditch without excessive erosion. • Response: As noted in the two previous responses, the upland diversion has been shifred and will now discharge to the first west drainage. This drainage was Inspected in the field and, because it is deeply incised, offers a more than adequate cross-sectional area to accommodate flows from the upland diversion. Excessive erosion should not be a problem, given a well defined natural channel, significant natural armoring (channel has cut to