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groundwater monitoring data indicate that mixed overburden and <br /> interburden waters have near neutral pH's. Sample pH's less than 6 are <br /> associated only with the lower Dakota coal. Where the coal's permeability <br /> is high enough to produce about 5gpm during sampling, the acid-producing <br /> reactions do not appear to be fast enough to maintain the pH of the water <br /> less than 5. Oxidation rates may increase because of the mining process. <br /> However, the supply of oxidation is only one of the constraints on the <br /> production of acid. Other constraints are imposed by the quantity of <br /> calcite present, and the reactivity of the pyrite. The paste-pH test, <br /> conducted under oxidizing conditions, indicates that a very small <br /> proportion of the overburden is likely to produce acid. The acid that is <br /> produced will be quickly neutralized. During the mining process, WFC <br /> will test the overburden and if acidic layers are encountered, they will be <br /> mixed with non-acidic layer to neutralize any acid forming effects. <br /> Potential impacts of replaced spoil on groundwater quality: The analysis <br /> of geochemical controls on groundwater quality suggests that the water <br /> chemistry and concentrations of most elements of concern are controlled <br /> by mineralogic reactions that will resist changes in water chemistry. <br /> Production of acid may occur in very local settings and is probably most <br /> prevalent in the coal which will be mined. Calculations indicate that <br /> neutralization of the acid will occur rapidly with mixing of water, or with <br /> movement of acidic water into calcite-bearing rocks. Also, the analysis <br /> conducted indicates that chemical changes are not likely to occur. <br /> Effects of mining on the local geomorphology: Impacts from mining on <br /> the local geomorphology will be long term, but appear to be of minimal <br /> significance. The reestablished reach of the drainage which will be mined <br /> will result in a shorter, slightly stepper stream channel. The potential for <br /> increased sediment loads in the drainage (once pond 007 is removed) <br /> should be offset by the stable banksides and the relatively small change in <br /> overall gradient. The increased runoff and consequent erosion potential <br /> on disturbed basins in the mining area due to the temporary loss of topsoil <br /> stricture should be of minimal significance. Contour ripping, mulching and <br /> revegetation have been demonstrated to minimize soil erosion and will be <br /> used to mitigate the increased runoff potential until the topsoil structure <br /> is developed. <br /> Effects of sediment ponds on channel characteristics and downstream <br /> users: Potential impacts of sediment pond 007 on downstream users will <br /> involve possible reductions in flow due to impounded water. The water <br /> augmentation plan discusses the available water which will be used should <br /> impacts be identified. WFC currently has rights to a sufficient quantity of <br /> water to supply all users associated with the mining activities, plus an <br /> 19 <br />