2010-01-25_PERMIT FILE - C1981044A (4)

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this inflow is not considered significant to impact any of the surface and ground water resources. Amore significant inflow is anticipated from the above listed sandstone strata. However, because of the limited thickness of the sandstone strata and relatively low permeability, the inflow into the rock slopes will not be of such a degree to cause a major impact on the local ground water characteristics. It was calculated that the potential inflow from the three sandstone strata into the three rock ramps would not be higher than approximately 30 gpm during the excavation, and the initial inflow would decrease to about 18 gpm within a few weeks of all three inclines' completion. During the rock slope excavation and after the completion of all three rock slopes ground water in the three sandstone strata will be flowing towards the decline. This would cause a temporary change of ground water flow direction, and a temporary drawdown within the aquifers. The zone of influence caused by the ground water drainage into the rock slopes was calculated with the use of [he Sichardt equation applicable for steady state flow in confined aquifers fully penetrated by a well or mine workings: R = 3,000 s -/K K =hydraulic conductivity (m/sec); s =drawdown caused by drainage (m). The above calculation indicated that a maximum probable influence of the rock slopes drainage would reach approximately 1,593 feet from the inclines. The shape of the calculated zone of influence would not be circular, but elliptical, with the prolongated axis parallel to the ground water flow direction towards southeast. Within the calculated zone of influence there are no ground water wells used for water supply, which could be impacted by the inclines' drainage. The data for the three Middle Sandstone Wells, which are monitored for water quality show no adverse impact or [rend. Plots of field conductivity for these Middle Sandstone wells are presented in Figure 58B. Wells TR-7A and TR-4 indicate slight reduction in concentrations of major ions over time. All three wells show reduction in concentrations of iron, which shows considerable variation in concentrations. The general reduction in iron concentrations may be the result of better purging of well pore volumes prior to sampling plus a switch to dissolve concentration analysis. Water level monitoring results through year 1992 provided in Figures 18 through 2Q in Section 2.04-7, Hydrology Information, show no change in the piezometric levels in the Twentymile Sandstone that could be attributable to mining activities. The only trend indicated in these plots is, perhaps, a slight increase in the levels in Well 84-01. Since both the potentiometric gradients and the influence of gravity is from the Twentymile Sandstone toward the target coal seam, no change in water quality would be expected as a result of ]ongwal] mining operations at the EC #5 and #6 Mines. The water quality data for the two Twentymile Sandstone wells, No. 9 Mine Well and Well 259 show no adverse impact or trend. Plots of field conductivity over time are presented in Figure 58c, and Exhibit 42, Figures 58P and SSQ for wells 259 and No. 9 MN, respectively. Likewise, plots of dissolved iron are presented in Figures SSR and 58S and plots of pH are provided in Figures 58T and 58U for these wells. The only apparent trend in the plots is an apparent reduction in dissolved iron in well 259. This may be the result of improvements in sampling procedures or i[ could simply be an artifact of large variability in the dissolved iron measurements as has been observed in other wells. Ground water levels in the alluvium have remained fairly regular, with normal seasonal fluctuations, apparently related to changes in river levels. Ground water levels in the alluvium are plotted in Figure 22, in Section 2.04.7, Hydrology Information. The data indicates no impact on alluvial water levels related to mining. Plot of field conductivity versus time for the three alluvial wells, AVF-3, AVF-5 and AVF-6, are presented in Figures 58V, 58W and 58X, respectively. Likewise, plots of dissolved iron are presented in Figures 58Y, 58Z and 58AA and Permit Renewal No. 4 2.05-42 Revised 3/5/03