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17 of the permit application package. A summary of that discussion is presented below. <br /> Groundwater <br /> The probable hydrologic consequences to groundwater resulting from coal extraction at <br /> the Yoast Mine include drawdowns to aquifers from pit inflows, and subsequent pit <br /> dewatering and production well pumping as well as impacts to groundwater quality <br /> resulting from flow through mine spoil. As the Yoast Mine is now reclaimed, pit <br /> dewatering and production well pumping will not occur during the 2025-2030 permit <br /> term. Seneca's predictions of the magnitude of these impacts are discussed in Tab 17 of <br /> the permit application and summarized below. <br /> Groundwater Inflows to Pits and Associated Drawdowns <br /> The Yoast Mine intercepted the following hydrologic units: the Wadge Overburden, <br /> Wadge Coal, Wolf Creek Overburden, and Wolf Creek Coal. Drawdowns due to pit <br /> inflows were to be mostly contained within the leasehold area, whereas adjacent water <br /> users are located beyond the one-foot drawdown contours, no significant impact on <br /> groundwater use due to pit inflows was predicted. <br /> Impacts of Production Well <br /> Seneca Property, LLC predicted that maximum drawdowns in the Trout Creek aquifer. <br /> The radial distance to the one-foot drawdown contour after 20 years of pumping was <br /> predicted to be 10 miles. The only known Trout Creek wells within this radius are <br /> associated with the Twentymile Coal Mine and are between seven and ten miles from the <br /> Yoast Mine 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 Creek <br /> channels due to changes in the groundwater regime were all predicted to be less than 0.55 <br /> acre-feet per year. However, streamflow depletions in Sage Creek and Grassy Creek were <br /> predicted to be higher: 4.9 acre-feet per year in Sage Creek and 5.8 acre-feet per year in <br /> 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 effect <br /> on groundwater would be degradation of quality with respect to total dissolved solids <br /> (TDS). Well yields in these bedrock units, the Wadge Coal and Overburden and the Wolf <br /> Creek Coal and Overburden, are insufficient for irrigation purposes. <br /> It was predicted that the increase in TDS concentrations in the bedrock aquifers will <br /> range from 70% in the Wadge Overburden to over 300% in the Wadge Coal. These <br /> predictions are for groundwater proximal to the re-saturated spoil, within the permit area. <br /> As groundwater migrates away from the re-saturated spoil, mixing, dilution from <br /> unaffected recharge, and geochemical changes will decrease the TDS concentrations. <br /> 12 <br />