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variable within the Trout Creek Sandstone, 'though; this variability probably causes • <br />permeability to vary within the region. Stewart also describes the thin sandstone beds <br />that occur within the Wadge Overburden as lenticular, again indicating that aquifer <br />properties such as cementation, fracturing, areal extent, etc. vary with location. <br />It should be noted that due to the low yielding nature of the Seneca II-W shallow <br />aquifers, the majority of aquifer tests performed at the Seneca II-W Mine are some <br />variation of the slug or bailer test. Since these tests stress a relatively small volume <br />of the aquifer, transmissivity and hydraulic conductivity values probably reflect <br />conditions immediately near the well bores. <br />C round Water Chemistry. The following section discusses the regional geochemical <br />reactions that affect ground water chemistry and details site specific ground water <br />quality. <br />The general geochemical processes ghat affect ground water quality in the Seneca II-W area <br />are as follows. Water containing carbon dioxide percolates below ground surface, • <br />dissolves carbonate minerals and possibly gypsum, and exchanges calcium and magnesium ions <br />for sodium ions. The following reactions illustrate these processes more specifically. <br />In a near-surface environment, carbon dioxide gas (COZ) from the atmosphere and from <br />organic decay reacts with water (H~0): <br />COZ + HZ ~ HZC03 (1) <br />The resulting carbonic acid (HZC03) dissociates: <br />HZC03 ~ H + HC03 (2) <br />HC03 ~_ H+ + C032 (3) <br />The effect of reactions 1, 2, and 3 is to produce a slightly acidic environment conducive <br />to the dissolution of calcite (CaC03) and dolomite CaMg(C03)2 . <br />CaC03 CaZ+ + C032 (4) <br />CaMg(C03)Z ~_ CaZ+ + M92+ + X032 (5) • <br />34 <br />