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• <br />TABLE 17-29 <br />(Continued) <br /> <br />Probable Hydrologic Consequences Analysis Results Sionifica nce <br />3. (Continued) water level in the Trout Creek aquifer will Appendix 16-1). No other wells produce from <br />recover to within 12,5 ft. of the pre-pumpage the Trout Creek Sandstone within the cone <br />water level over a 40 year period based on of influence of the Peabody well. <br />maximum pumping conditions. <br />4. Impact of replaced spoil material on <br />ground water flow and recharge capacity <br />5. Containment of pit inflow pumpage <br />and impacts on water quality. <br />6. Impact of spoil water on ground <br />water quality <br />Literature research indicates that hydraulic <br />conductivity and porosity are estimated to <br />increase by 25 percent in spoil material <br />compared to its original premined condition, <br />A more homogeneous texture within spoil <br />material will lessen differences between <br />horizontal and vertical permeability <br />present in the premined material. <br />Impermeable and poor hydraulically <br />conductive strata will be broken up by <br />mining and replacement activities. <br />Replaced topsoil is estimated to display <br />a more even mix of moderate infiltration <br />rates. Prompt revegetation of reclaimed <br />areas will induce retention of soil <br />moisture, enhance infiltration, and <br />prevent surface runoff. <br />The highest Overburden and Wadge Coal yearly <br />pit inflows will occur in year 2001, Pit <br />inflows will discharge primarily to Dry <br />Creek. Using pit inflow rates for 2001 and <br />average TDS values for the Overburden <br />and Wadge Coal, pit inflow discharge to <br />Dry Creek will result in an increase in <br />Dry Creek's average TDS from 1048 to 1071 <br />mg/1, a 2@ increase. <br />Spoil discharge to the overburden aquifer <br />will result in a 5-7 percent TDS increase. <br />Spoil discharge to the Wadge Coal aquifer <br />may increase TDS levels from 74-98 percent. <br />Spoil discharge to the Dry Creek alluvial <br />Short term impact on ground water flow and <br />recharge capacity until spoil material re- <br />saturates and the natural hydraulic gradient <br />is reestablished. Infiltration rates will <br />be slow to moderate in the spoil, but will <br />still exceed premining rates. Horizontal <br />and vertical flow of infiltration water and <br />ground water will become more uniform. No <br />long-term impact of any significance. <br />A 2~ increase in the average TDS for Dry <br />Creek as a result of pit discharges <br />represents a minimum impact. Since these <br />calculations are based on conservative <br />assumptions, pit inflow discharges will <br />probably have an unmeasurable impact on <br />Dry Creek water chemistry. <br />The premining water use potential for the <br />overburden and coal aquifers is marginal to <br />unsuitable for stock use and unsuitable for <br />irrigation use. There are no local wells <br />completed in the overburden and coal units <br /> <br />