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RULE 2 - PERMITS <br />aquifer, and both marine shale and altered volcanic ash (Yampa Bed) separating the Wadge coal <br />• from the underlying Trout Creek aquifer. <br />PSCM development also has the potential to affect the Seneca II spoil aquifer, located upgradient <br />and in hydrologic connection with the units to be disturbed by mining, and may lead to increased <br />spoil aquifer effects on groundwater quality. As detailed in the Probable Hydrologic Consequences, <br />the spoils aquifer has ten times the recharge rate and hundreds of times the hydraulic conductivity <br />of the undisturbed bedrock units. Groundwater flow from the spoils aquifer to the mine workings <br />will therefore be limited by the low - permeability bedrock that separates the portal box cut from the <br />Seneca lI spoils, and will not materially affect the spoil aquifer levels. Spoil water will gradually <br />replace a portion of the native groundwater in these intervening undisturbed bedrock units that will <br />discharge to the mine workings. This effect is highly localized, and does not occur in any geologic <br />units characterized as regional aquifers of significance. <br />During the initial permit term, all mining will be conducted with continuous miners, and no <br />subsidence is anticipated. Revisions to this PAP for subsequent permit terms will address the <br />potential effects of subsidence on groundwater resources. <br />Underground mining operations will expose coal, floor, and roof materials to oxidation and <br />increased leaching as mining is completed and working areas are abandoned. Natural caving will <br />also expose substantial quantities of broken coal and roof material to oxidation and leaching as <br />groundwater floods these areas. It is anticipated pH will increase slightly and the ground water <br />chemistry will evolve toward a calcium - magnesium sulfate water type with increases in TDS and <br />certain mineral constituents, including iron and manganese. In order to effectively prevent or <br />mitigate these impacts, underground mining operations will be limited to development and <br />disturbance of the minimum area necessary to provide for effective coal extraction. PSCM will <br />also keep all development within the mineable coal seams to the extent operationally practical. <br />While there will undoubtedly be some impacts on ground water quality, these impacts will generally <br />be confined to the mine and immediately adjacent areas by the relatively low permeability of the <br />geologic units and the limited hydrologic connection with other more permeable units. With <br />gradual collapse and caving of the mine workings following conventional mining, the void space <br />available for ground water storage will be significantly reduced, expediting restoration of <br />equilibrium with the natural water table with a resulting reduction in the amount of time that mine <br />materials will be exposed to oxidizing conditions. <br />Minor changes in ground water quality will not affect any ground water users since existing ground <br />water use in the immediate area is limited to the Trout Creek and Twentymile aquifers, which are <br />isolated from the affected units by thick, relatively impermeable shale and/or ash deposits. Any <br />potential postmining mine water discharge will be prevented by closing and sealing mine openings, <br />and restoring the portal access pit to the approximate original contour. Anticipated mining- related <br />changes in ground water quality should not significantly affect the beneficial use of any <br />groundwater. <br />Surface placement of coal has the potential to affect ground water quantity and quality as a result of <br />• increased runoff from the associated disturbance areas, and reinfiltration of this runoff into alluvial <br />aquifers. (Analyses of both actual existing and potential future coal e development waste3 <br />durlrc A f Q,x — h� 4 fa <br />PSCM Permit App. 2.05 -100 Revision 03/05/10 <br />