2019-01-17_REVISION - C1982056 - Laserfiche WebLink

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7. Proposed revised page 2.05-50.10 does not appear to take into account the approval of MR299, the proposed revised text does not follow with the preceding page. Please review these pages and revise the most recently approved permit text and insure they follow the preceding and subsequent text and pagination. Please ensure updates from all approved revisions prior to the next response are included in updated pages. Response: Please see previous response to Comment 6. 8. The design information for the passive water treatment system contained in Exhibit 49EE must be certified by a qualified registered professional engineer experienced in the design and construction of impoundments per Rule 2.05.3(4)(a)(ii)(A). Please submit documentation to be included in the proposed Exhibit that these designs are certified per the cited rule. Addressed with 11/13/2018 submission 9. The current design information for the 6MN Reservoir is contained in Exhibit 8CC of the permit. Please update this exhibit to indicate that the design of the Reservoir has been updated with TR- 84 to include a spillway to facility discharge from the passive water treatment system. Please cite where the modified design can be found in the permit. No longer applicable to this revision as discharge is not being proposed. 10. The current 6MN Reservoir is designed as a closed system and the "upper diversion ditch " was designed to divert 13.16 acre-feet of runoff from a 119.09 -acre area around the reservoir based on a 100 year -24-hour storm event. Now it appears a large portion of this 119.09 -acre area watershed will be diverted directly into the 6MN Reservoir with the south and north diversion ditch around the proposed passive treatment system. TC submitted Exhibit 49EE-FI, Sheet I which also has "Exhibit EX49-F2 " which is a cross section of the modification of the reservoir embankment to include a new primary spillway for the 6MN Reservoir. However, TC did not provide documentation that the spillway design complies with Rule 4.05.9(2). The spillway system must be designed to safely pass the applicable design precipitation event (100 - year, 24-hour precipitation event because the Reservoir meets the size criteria outline in Rule 4.05.9(4)) plus inflow from the underground mine water. Please provide this documentation or modify the design as necessary for compliance with Rule 4.05.9(2). See December 2018 Adequacy items for additional requests for clarification on design submitted 11/13/2018 Response: Since the proposed Passive Treatment System (System) has been moved to the next drainage to the Northwest, the drainage area and diversion system for the 6MN Reservoir will remain unchanged. The north and south diversion ditches for the System will intercept runoff flows from the contributing drainage basin and route them around the System, returning them to the existing natural drainage below (east end) the System (as shown on Drawing C-01, Wetland Plan, of the revised design drawing set). At this time, TC does not plan to discharge from the 6MN Reservoir, except for pumped discharge to the existing mine water system, so the noted primary spillway is not part of the current plan. Recognizing that the System will result in treated water inputs to the 6MN Reservoir, both flows from the other main inflow source to the Reservoir (10 -Right Pipeline) and the pumped discharge rate to the mine water system will be adjusted to maintain reservoir levels at or below the design operating level. 11. Section 4.6 of proposed Exhibit 49EE contains a discussion of the basis for the design of the North and South Diversion Ditches. The diversions are depicted in the cross sections provided in Appendix C to Exhibit 49EE. In accordance with Rule 4.05.3(7) the diversion design shall incorporate thefollowing: a. Channel lining, including channel riprap, shall be designed using standard engineering practices to pass safely the design velocities. Addressed with 11/13/2018 submission