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I, <br />9.0 WATER CHEMISTRY AFTER INSTALLAT/ON <br />OF PROPOSED BULKHEADS <br />1 <br />1 <br />1 <br />1 <br />9. 1 Introduction and Methodology <br />This section summarizes the results of numerical modeling of the geochemical <br />questions associated with the proposed system of bulkheads: estimating the <br />approximate chemistry of the impounded water, identifying what, if any, reactions <br />may occur as impounded water moves either through the country rock around the <br />bulkheads or as it moves through the natural fracture system back to the ground <br />surface, predicting the character of the discharging water once it equilibrates to the <br />atmosphere and precipitates any oversaturated minerals, and, finally, estimating the <br />impact of the discharged water on the overall chemistry of Cement Creek. Numerical <br />geochemical modeling is the computer-based simulation of the complex systems of <br />rock•water interactions. It permits the simultaneous consideration of numerous <br />chemical equilibria states and reactions among solid, aqueous and gaseous species. <br />Geochemical modeling is valued as a check on conceptual models because it permits <br />1) examination of a total chemical system, as well as critical subsets of that system, <br />2) protection against oversights that can occur when complex systems are <br />oversimplified, and 3? rapid investigation of modified or alternative expressions of the <br />conceptual model. <br />The model used was MINTEQA2, versions 3.0 and 3.11. This is a metal speciation <br />program developed by Battelle Northwest Laboratories and distributed by the United <br />suun,V+. na~.'~ ;.'ht ~!.I~rt993 Apt 5B <br />N''1 SIfT1011 HYDRO-SEARCH <br />