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Twentymile Coal, LLC. <br />Page 3 <br />November 16th 2018 <br />the proposed passive treatment system. TC submitted Exhibit 49EE-F1, Sheet 1 which also has <br />"Exhibit EX49-F2" which is a cross section of the modification of the reservoir embankment to <br />include a new primary spillway for the 6MN Reservoir. However, TC did not provide <br />documentation that the spillway design complies with Rule 4.05.9(2). The spillway system must <br />be designed to safely pass the applicable design precipitation event (100 -year, 24-hour <br />precipitation event because the Reservoir meets the size criteria outline in Rule 4.05.9(4)) plus <br />inflow from the underground mine water. Please provide this documentation or modify the <br />design as necessary for compliance with Rule 4.05.9(2). <br />See December 2018 Adequacy items for additional requests for clarification on design <br />submitted 11/13/2018 <br />11. Section 4.6 of proposed Exhibit 49EE contains a discussion of the basis for the design of the <br />North and South Diversion Ditches. The diversions are depicted in the cross sections provided in <br />Appendix C to Exhibit 49EE. In accordance with Rule 4.05.3(7) the diversion design shall <br />incorporate the following: <br />a. Channel lining, including channel riprap, shall be designed using standard engineering <br />practices to pass safely the design velocities. <br />Addressed with 11/13/2018 submission <br />b. Freeboard shall be no less than .3 feet. <br />The discussion in section 4.6 of Exhibit 49EE and the cross-sections in Appendix C do not show <br />how the designs meet the above requirements. Please revise the design to incorporate these <br />requirements. <br />See December 2018 Adequacy items for additional requests for clarification on design <br />submitted 11/13/2108 <br />12. Please update Map 23c to depict the new surface disturbance area associated with the proposed <br />passive water treatment system. Not yet addressed <br />Rule 2.05.4 <br />13. Rule 2.05.4 indicates that the application shall contain a reclamation plan for reclamation of lands <br />within the proposed permit area. In order for the treatment cells and the 6MN Reservoir to be <br />retained as permanent features TC must provide the permanent impoundment demonstration <br />required by Rule 4.05.9(13). Until these demonstrations have been submitted, TC must supply a <br />reclamation plan for the passive water treatment system and the 6MN reservoir in accordance <br />with Rule 2.05.4. The reclamation plan submitted on proposed revised page 2.05-106 and 106.1 <br />does not provide a detailed description to demonstrate compliance with Rule 2.05.4. Appendix I <br />of proposed Exhibit 49EE shows the post mine configuration of the Passive Water Treatment <br />System and 6MN Reservoir. However, Appendix I depicts very little reclamation or modification <br />of the system features and does not depict how TC intends to provide "flow through" the cells <br />