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one strata. The sandstone is water bearing and the static water level (potentiometric surface) is at an elevation of <br />6,100 feet in the general area of the rock slopes. Hydraulic conductivity of the sandstone strata was estimated as 1.42 <br />ft/day (5x104 cm/sec). This estimate is based on permeability testing in other boreholes in the mine Permit Area. <br />Although some ground water inflow during the rock slopes excavation was expected to occur from the shales and coal <br />seams, this inflow was not expected to significantly impact any of the surface and ground water resources. A more <br />significant inflow was anticipated from the identified sandstone strata. Given, however, the limited thickness of the <br />sandstone strata and relatively low permeability, the inflow into the rock slopes would not significantly impact local <br />ground water characteristics. It was calculated that the potential inflow from the three sandstone strata into the three <br />rock ramps would not be higher than approximately 30 gpm during the excavation, and the initial inflow would <br />decrease to about 18 gpm within a few weeks of all three inclines' completion, which was similar to what was actually <br />encountered. <br />During the rock slope excavation and after the completion of all three rock slopes, ground water in the three sandstone <br />strata would flow towards the decline. This would cause a temporary change of ground water flow direction, and a <br />temporary drawdown within the aquifers. The zone of influence caused by the ground water drainage into the rock <br />slopes was calculated with the use of the Sichardt equation applicable for steady -state flow in confined aquifers fully <br />penetrated by a well or mine workings: <br />R = 3,000 s 4K <br />K = hydraulic conductivity (m/sec) <br />s = drawdown caused by drainage (m) <br />The above calculation indicated that a maximum probable influence of the rock slopes drainage would reach <br />approximately 1,593 feet from the inclines. The shape of the calculated zone of influence would not be circular, but <br />elliptical, with the long axis parallel to the ground water flow direction towards the southeast. Within the calculated <br />zone of influence, there are no ground water water supply wells, which could be impacted by drainage to the inclines. <br />The data for the three Middle Sandstone Wells, which are monitored for water quality, show no adverse impact or <br />trend. Plots of field conductivity for these Middle Sandstone wells are presented in Figure 58B. Wells TR -7A and <br />TR -4 indicate slight reduction in concentrations of major ions over time. All three wells show reduction in <br />concentrations of iron, which shows considerable variation in concentrations. The general reduction in iron <br />concentrations may be the result of better purging of well pore volumes prior to sampling plus a switch to dissolved <br />iron analysis. <br />Water level monitoring results through year 1992, provided in Figures 18 through 20, in Section 2.04 -7, Hydrology <br />Information, show no change in the piezometric levels in the Twentymile Sandstone that could be attributable to <br />mining activities. The only trend indicated in these plots is, perhaps, a slight increase in the levels in Well 84 -01. <br />Since both the potentiometric gradients and the influence of gravity is from the Twentymile Sandstone toward the <br />target coal seam, no change in water quality would be expected as a result of longwall mining operations at the No. 5 <br />and No. 6 mines. <br />The water quality data for the two Twentymile Sandstone wells, No. 9 Mine Well and Well 259 show no adverse <br />impact or trend. Plots of field conductivity over time are presented in Figure 58c, and Exhibit 42, Figures 58P and <br />58Q for wells 259 and No. 9 MN, respectively. Likewise, plots of dissolved iron are presented in Figures 58R and <br />58S and plots of pH are provided in Figures 58T and 58U for these wells. The only apparent trend in the plots is an <br />apparent reduction in dissolved iron in well 259. This may be the result of improvements in sampling procedures or it <br />could simply be an artifact of large variability in the dissolved iron measurements, as has been observed in other wells. <br />Ground water levels in the alluvium have remained fairly regular, with normal seasonal fluctuations, apparently <br />related to changes in river levels. Ground water levels in the alluvium are plotted in Figure 22, in Section 2.04.7, <br />Hydrology Information. The data indicates no impact on alluvial water levels related to mining. <br />TR14 -36 2.05 -42 Revised 03/20/14 <br />