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Twentymile Coal, LLC. <br />Page 8 <br />November 16th 2018 <br />a. It appears to DRMS that weep holes may be needed, particularly at the discharge end of <br />the cascade structure. Please explain why these are not necessary or consider modifying <br />the design. <br />b. Please provide a description and update diagram showing how the inlet pipe and cascade <br />are being anchored into the drainage, so that neither water moving throw the pipe or <br />precipitation will compromise the function of the cascade. <br />12. Please provide side slope ratios and spillway crest elevations for each of the system spillways. <br />13. Please provide SedCad for treatment system diversion ditches, curve numbers, acreage of the <br />drainage specifying what portion will go to the north and south ditch, and design as per 4.05.3(7). <br />Some of the adequacy review issues identified in the Division's first adequacy review letter are no longer <br />applicable due the location change and that no discharge is being proposed at this time. However, for <br />those that have not been resolved at the writing of this letter, TC must address the issues or provide <br />discussion as to how they have addressed or why they no longer apply. The Division is required to issue a <br />proposed decision for this revision by December 28, 2018. If you need additional time to address the <br />adequacy review items, please request an extension of the decision date. <br />If you have any questions feel free to contact me at (303) 866-3567, extension 8147. <br />Sincerely, <br />Tabetha Lynch <br />Environmental Protection Specialist <br />