2014-04-16_REVISION - C1981008 - Laserfiche WebLink

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COLORADO Division of Reclamation, Mining and Safety Department of Natural Resources 1313 Sherman Street, Room 215 Denver, CO 80203 April 16, 2014 Chris Gilbreath Tri -State Generation and Transmission Association, Inc. P.O. Box 33695 Denver, CO 80233 -0695 Re: New Horizon Mine (Permit No. C- 1981 -008), TR- 63, second adequacy letter Dear Mr. Gilbreath: We received your responses to our first adequacy letter for TR -63 on April 9, 2014. I want to thank you and your staff (and consultant) for the considerable attention spent addressing our issues. However, there are still some remaining items to be clarified as explained in the following list (the numbers in the list correspond to the numbers in our original letter of April 3rd and also used by you in your response letter). Please provide an updated submittal and/or explanations for each item. 1. No further response required. 2. No further response required. 3. More information is required. The added text only addresses cover on the solid pipe. It should also include a discussion on the amount of cover on the perforated pipe segments. 4. No further response required. 5. More information is required regarding the selection of rock sizes in the design. The Division is concerned that placing the pipe in larger rock such as the 12" — 18" rock shown in Detail A will compromise the integrity of the pipe. Even the smaller rock shown in Detail B may be oversized. 6. More detail is required. Detail C does not illustrate where pipes end or are connected at the nexus. 7. The response addresses the confusing term "rock draw," but there appears to be another problem with the text box on Map 2.05.3(3) -21. The text indicates that the spring water flows from the nexus into a perforated pipe, but the pipe below the nexus is solid rather than perforated per other information in the submittal. 8. No further response required. 9. No further response required. 10. No further response required. 11. The text discussing the capacity of the pond should explain that in the model the pond holds 3 ac -ft of sediment. 12. No further response required as part of this revision. Further analysis of Pond 013 capacity is required, but not as part of TR -63. What maximum level of water in the pond allows a remaining capacity for the design event (10 -year, 24- hour)? What rate of continuous pumping from the NH2 Pit into the pond will keep the pond at or below this level9 oF. coLO�P 1313 Sherman Street, Room 215, Denver, CO 80203 P 303.866.3567 F 303.832.8106 http: / /mining.state.co.us John W. Hickenloo er Governor I Mike King, Director I Virginia Brannon Director ** P � �, $ 1 q6