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- .......-M. .,.+... ~.- .. . i i.. .. ,. i 5~ t: .. 16 .Unless the presamprlon Char rock wtrh <0.8% su~trr was used Jo characterize NNP calculations s for surface or groundwater, it could be removed from the text. (f the Operator has used the assumption in any ARD predictive context, the statement should be verfjed j. Response: CC&V apologizes for the confusion caused by inseRing this statemem within the context of our discussion of ARD risk The prediction of ARD risk within the overburden stockpiles should not have relied on the aforementioned 0.8~ cutoff level. The OMLR is correct; the 0.6% total sulfur value was a criter'io'n chosen to protect the hydrologic system under circumstances of Amendment No. 6. Consequently, the following statement from Section 4.2 of the cited report relates more to the criteria of Amendment No. 6 and should not have been included without being appropriately qualified: ~ ~ Pi - ' "Given [he relative proportions of the overburden from these two areas, an estimated ~- 75% of the future overburden is projected to have total sulfur contents less than 0.896. - ~ This high percentage of material with total sulfur contents less than the cutoff value for - - 'acid generation indicated that the overburden is not likely to produce acidic leachates.•' Additionally, many of the statistical analyses that identify the proportion of overburden that has less than 0.8EYo total sulfur, though factually correct, should not be used as a mearu of estimating the abunda~a of non-acid generating rock within [he overburden stockp[les. A portion of the overburden material to be mined under Amendment No, 8, especially materials with NNP values of less than zero. may lx~ame locally acidic. This fact is acknowledged in the concluding paragraph of Section 4.0 of the aced report, Appendix J of Volume Il of the Amendment Na 8 application. which states: ,.: i. ~' ~ c _ "However, any acid leachates that infiltrate from the overburden Into the diatreme will '`^~be neutralized by reaction with carbonate minerals found in abundance at depth under the mine areas. The characterization of the ruvaelization properties of the dlatreme as a '' 4function of depth is described below in Section S:' This statement provides a critical link to undesstatr~ng the gevchentical behavior of [be en£ue Mining District: Within the oontext of Appendix 1 of the Amendment No. 8 application, ARD risk is best defined as the long-term pH observed in the Carlton Tunnel. The Cazlton Tunnel is identified as the receividg water for various water from the area including seepage out of the overburden stockpiles (to the exteri[ seepage may actor). Water was assumed to infiltrate through overburden material in the hydraulic model described in Section 6.0 of Appendix 1 of this application. Although acidic interstitial water may form within portions of the overburden piles, CCBrV has demonstrated that there is ample neutralisation within other pcations of the overburden storage areas and, more itnportandy, the diatreme system ib naurralize acidity that rosy migrate through it. Additionally, Appendix 1 describes the sequential reactions that occur along the deep flow path of water in the diatreme. The nature of these reactions will also provide a raechattism to remove touch of the zinc from water reaching the Carlton Tututel, even if additional zinc is released from the overburden stockpiles under Amendment No. 8. . ~.{.'. Aitlioilgli the text of Appendix I to Amendment No. 8 noes contain statements retateii to use of 0.8~ suifur,'such statetrrettts do not affect the final conclusions of the Appendix as discussed above. In addition; as discussed in subseAuent responses, CC&tV is providing additional modeling information on the overall acid neutralizing potential of the diatreme in attachments to this submittal. 2. ' 'Page Z2. 1~: s, ' , -The AGP formula indicates char b7R'o of the sulfur was su~i'de sulfur. The footnote, indicates G9~. 2.