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by the Carlton Tunnel through what would have otherwise become increasingly preferential pathways. VI. S.: We must consider the possibility that waste rock leachate may escape the capture system, as a result of unforeseen circumstances such as extreme precipitation events, dump geotechnical failures, short circuiting, etc., and therefore potential interactions of the leachate with geologic material outside the diatreme must be taken into account. Without such an assessment, the downgradient ground water monitoring must be extensive. The Operator cites the numerous humidity cell tests. How many of the tests involved interaction of acidic waste rock leachate with geologic materials outside of the diatreme? CC&V Response: CC&V has considered the possibility that leachate from overburden may escape the diatremal capture system. CC&V has conducted a water balance evaluation for the diatreme and surrounding areas (MLE Application, Appendix 1, Volume II, Attachment 1) and for the Grassy Valley drainage, the only drainage within the permit area with frequent surface flow. The results of both these evaluations is that there is no water that contacts mining material that is not expected to enter the diatremal rock and report to the regional ground water table intersected by the Carlton Tunnel. These studies show that flow from the diatreme to the surrounding granite is impossible; the surrounding granite is always upgradient from the saturated portion of the diatreme. Even if it were possible, the low hydraulic conductivity of the Precambrian rock would prevent more than a very small flow. However, unforeseen excursions are always possible in any mining activity. With the guidance and concurrence of DRMS and CDPHE, CC&V has developed and maintained an extensive groundwater and surface water monitoring system, which will identify any excursions of mine-related constituents from the permitted area to the external environment. These monitoring systems and locations are described in MLE Application, Appendix 2, Volume II, and cover groundwater and surface water in Grassy Valley, Vindicator Valley, Wilson Creek, Bateman Creek, Arequa Gulch, Gold Run, Squaw Gulch, Poverty Gulch, and Cripple Creek. As a part of the MLE permit review process, DRMS recommended, and CC&V has proposed, augmentation of the existing Poverty Gulch monitoring to recognize the proposed additional mine disturbance in that drainage. With respect to the humidity cell testing, a total of 17 of the 42 tests (40%) were conducted in the Precambrian rock (granite, granodiorite, or schist) that surround the diatremal rocks (MLE Application, Appendix 1, Volume II, Attachment 1, p 1-1). This extensive database is considered appropriate to support the detailed evaluation of the interaction of oxidants with the rock, both in-situ and after mining. VI. T.: Flow rate will be irrelevant only if the uniform batch reactor concept proposed by the Operator turns out to be correct, a concept that will only be validated through long-term post-closure monitoring. CC&V Response: CC&V's conclusion that the flow rate is irrelevant to the impact of transport of sulfate oxidation products from ECOSA is derived as follows. Oxidation will take place at some rate in the ECOSA pile (depending on the access of oxygen to the overburden, which is designed to be very limited). The oxidation releases a quantity of sulfate and metals at a rate that is primarily limited by the oxygen availability. This mass of materials is dissolved by whatever infiltrating flow occurs, and is transported out of the ECOSA by that same flow. If the flow rate is high, the concentration is lower; if the flow rate is low the concentration is higher. The mass of dissolved constituents is transported through the diatreme to the regional ground water table intersected by the Carlton Tunnel (as further demonstrated by the results of the current ECOSA hydrology drilling program, which show that ECOSA is within the collection area of the diatreme). The mass of constituents