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• 4.5 Geochemistry <br />In 1998, for Amendment No. 7, Shepherd Miller Inc. ("SMI") and Adrian Brown <br />Consultants ("ABC") conducted extensive investigations of the ground water hydrology <br />and geochemistry of the District. These studies have been reviewed and updated as a part <br />of the investigations for this Amendment No. 8. A copy of the most recent study is <br />included as Appendix 1 in Volume II of this document. The 1998 study is included in <br />Attachment 1 of Appendix 1 in Volume II of this document. The results of the studies <br />are summarized below. <br />The 1998 study reached three pertinent conclusions: <br />• surface mining activities are not expected to cause a meaningful change in the <br />hydrologic behavior of the system; <br />• any potential acid generation that might occur at the surface or in historical <br />• underground mines will be neutralized along the subsurface flow paths to the <br />Carlton Tunnel; and <br />• zinc concentrations in the Carlton Tunnel are affected by both hydrological <br />and geochemical processes but remain low and are expected to remain low in <br />the future. <br />For Amendment No. 8, these conclusions were re-evaluated in light of projected <br />increased mining activities and additional data that have been collected. Approximately <br />557 additional drill hole samples from locations throughout the proposed Amendment <br />No. 8 mine azeas were analyzed for acid generating potential ("AGP") and acid <br />neutralizing potential ("ANP"). Tn addition, approximately 116,585 blast hole samples <br />were analyzed for percent carbon and percent sulfur, and these numbers were correlated <br />to ANP and AGP using conversion factors as discussed in Appendix 1. Finally, the water <br />balance model was modified to reflect current information on temperature, precipitation, <br />and evaporation and to reflect Amendment No. 8 activities. <br />• <br />20 <br />