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provided for sizing this ditch as a permanent postmine channel in the unlikely event that the CRDA <br />Expansion activities were to cease after the initial fill sequence. <br />10. Please submit SEDCAD runs that use the ARCS Type II storm that is applicable to the mine <br />location. <br />Response: Revised SEDCAD runs and ditch design information, utilizing the correct design storm, <br />are provided with these responses for replacement in Attachments A and B. <br />11. The underdrain designs included in Exhibit 26C and discussions in the revised text discusses <br />wrapping the underdrain with geo fabric. During a discussion with the operator (Jerry Nettleton) <br />during an onsite inspection on July 15, 2009, TCC indicated that the underdrain would have layers <br />of finer aggregate instead of geo fabric. If this is a change to the underdrain design, please update <br />text, maps and exhibits in the application. Please assure that the change in design conforms with <br />Rule 4.103(1)(c). <br />Response: Experience has shown that, in this type of application, a graded cover material works more <br />effectively than geotextile to reduce fines infiltration into the underdrain to prevent clogging and <br />"blinding-off' of the drain. As the geotechnical consultant for this project, NWCC recommends the <br />construction method shown in cross-section on Drawing C-301. Both the revision text and supporting <br />materials have been reviewed and revised to reflect this design change. <br />12. Please correct Table 49A to sum the "Total Volume" column for the Eastern Mining District <br />Table. The Division's sum for this column is 20,505 cubic yards, instead of 5 cubic yards as shown <br />on the revised table. <br />Response: Table 49A has been corrected, and the revised table accompanies these responses. <br />13. Please tie the contours of the proposed CRDA expansion into the existing contours of the <br />current RDA on the Final Grading map. <br />Response: The Final Grading Map (Drawing C-101) has been revised to reflect grading of the CRDA <br />expansion to tie-in with the existing Refuse Disposal Area. <br />14. Please define where the 50ft. interval to the first bench on the north face of the CRDA initiates <br />from. This was not clearly defined on the north toe of the current RDA in the construction plans <br />Defining where the 50 ft. interval is measured from will minimize discrepancies as the construction <br />of the pile progresses <br />Response: TCC will establish a survey benchmark at the north end of the CRDA at the approximate <br />location shown on Drawing C-101. TCC will survey and document the coordinates and elevation of <br />the benchmark. Thereafter, the 50 foot (maximum) bench elevation may be measured from the crest of <br />the highest point on the bench (typically near the center of each contour bench) to the point where the <br />toe of the bench (at the same location) intersects natural ground. <br />15. Please clarify. Existing RDA is approximately 3 million cubic yards of material. TCC refers to <br />the proposed CRDA expansion as 20 million cubic yards Is the 20 million cubic yards of waste <br />material in addition to the existing 3 million cubic yards for a total of 23 million cubic yards, or will <br />the total pile: current RDA plus proposed CRDA, equal 20 million cubic yards total?