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JD -6 Mine Drainage Design — Revised Third Adequacy Review <br />Page 3 <br />April 2, 2014 <br />potential for insufficient channel capacity exists and therefore requires the MDS, <br />LDS -N, and LSD -E channels be upgraded or reconstructed with a consistent <br />geometry in a similar fashion to that now proposed for the UDS. Please provide <br />the requisite analyses, signed drawings, and consider Comment 5a above in your <br />response. <br />b. Please provide stability analysis results... The provided response is inadequate. <br />Please provide the requisite analyses discussed in Comment 5a above in your <br />response. <br />11. Page 26, SWRP spillway... <br />a. The expected depth to erosion resistant material... The provided response is <br />partially adequate. The reconfiguration of the spillway is acceptable. However, <br />based on the response to Comment l Lc, to use a pump to drain the SWRP, the <br />DRMS considers the spillway size and/or revetment protection to be inadequate. <br />As there is no gravity outlet to drain the SWRP, the spillway must be sized to pass <br />the 100 -year, 24 -hour peak flow (12.56 cfs) assuming the SWRP is full to the <br />spillway invert at the onset of the design storm. Given the size of the SWRP, the <br />DRMS expects attenuation in the full pond to be negligible. Please design the <br />spillway and spillway chute to pass the unattenuated design peak flow. <br />b. Based on Figures 4 and 5... The response is adequate. <br />c. There is no way presented in the SWRP design plan... The response is adequate. <br />d. Please address the reclamation /post mining plan for the SWRP. The response is <br />adequate. <br />12. Page 30, Section 6.1. The response is adequate. <br />13. Page 36, Attachment 3. The response is adequate. <br />New Comments: <br />14. Plate 2: Plate 2 shows six check/drop structures (drop face) proposed for the Upper <br />Diversion Channel. Please provide the following: <br />a. Specifications or reference to specifications for the "D84 Grain Size of 16 " ", <br />b. Riprap or "D84 Grain Size of 16 "" sizing analyses for the proposed revetment. <br />15. Plate 6: Some explanation of the rock apron is required. Please provide the following: <br />a. Dimensioned thickness of the rock apron and "D50 = 75 "" material, <br />b. Specifications or reference to specifications for the "D50 = 75 "" material, <br />c. Specifications or reference to specifications for the rock apron revetment, and <br />d. How is the "D50 = 75 "" material proposed for the spillway crest prevented from <br />migrating into the presumably larger material in the rock apron. <br />If either you or the applicants have any questions regarding the comments above, please call me <br />at (303) 866 -3567, extension 8169. <br />m- \min \tc1 \_uranium \m -77 -310 jd -6\m -77- 310_ 3rdstrmMrcmnts _mem02apr14crtdhdr.docx <br />