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be 186 feet. After 20 years of recovery, the residual drawdown within one mile of <br />the well is predicted to be less than two feet. The radial distance to the one -foot <br />drawdown contour after 20 years of pumping was predicted to be 10 miles. The <br />only known Trout Creek wells within this radius are associated with the <br />Twentymile Coal Mine and are between seven and ten miles from the Yoast Mine <br />well. The drawdown at this distance from the Yoast Mine well should not <br />significantly impact these wells. <br />Streamflow Depletion Predictions <br />Streamflow depletions in the Yampa River, Fish Creek, Middle Creek, and Trout <br />Creek channels due to changes in the groundwater regime were all predicted to be <br />less than 0.55 acre-feet per year. However, streamflow depletions in Sage Creek <br />and Grassy Creek were predicted to be higher: 4.9 acre-feet per year in Sage Creek <br />and 5.8 acre-feet per year in Grassy Creek. <br />Impact of Replaced Spoil on Groundwater <br />Seneca Property, LLC predicted that the replaced spoil would have a 25% higher <br />hydraulic conductivity than the undisturbed material. Other than that, the primary <br />effect on groundwater would be degradation of quality with respect to total <br />dissolved solids (TDS). <br />It was predicted that the increase in TDS concentrations in the bedrock aquifers <br />will range from 70% in the Wadge Overburden to over 300% in the Wadge Coal. <br />These predictions are for groundwater in close proximity to the re -saturated spoil, <br />within the permit area. As groundwater migrates away from the re -saturated spoil, <br />mixing, dilution from unaffected recharge, and geochemical changes will decrease <br />the TDS concentrations. Well yields in these bedrock units, the Wadge Coal and <br />Overburden and the Wolf Creek Coal and Overburden, are insufficient for <br />irrigation purposes. <br />The alluvial aquifers that will be affected by the re -saturated spoil include the <br />Annand Draw, Upper Grassy Creek, Lower Grassy Creek, and Sage Creek <br />alluvium. Within the Grassy Creek basin, above the confluence with Scotchman's <br />Gulch, the magnitude of the TDS increase will be high immediately below the re - <br />saturated spoil, but will be undetectable a short distance beyond within the Upper <br />Grassy Creek Alluvium. This diminution of TDS will result from low hydraulic <br />conductivities in the Grassy Creek Alluvium, additional downgradient chemical <br />changes, and dilution and mixing from shallow bedrock units which discharge to <br />the alluvium. <br />Seneca Property, LLC predicts that the maximum TDS increase in the Annand <br />Draw Alluvium will be 58% immediately below the re -saturated spoil, attenuating <br />to less than 5% near the confluence of Lower Grassy Creek and Scotchman's <br />Gulch. The predicted TDS increases in the Grassy Creek and Annand Draw <br />22 <br />