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• <br />AW -15 has been dry during all monitoring events. <br />The average conductivity at the upstream North Fork of the Gunnison River <br />monitoring station for the baseline period (2008 AHR) is 180 umhos /cm. The <br />following table presents the estimated affect the coal pile and gob pile <br />leachate will have on the quality of water in the North Fork of the Gunnison <br />River at low flow: <br />n <br />U <br />VrIU Nor[n rorK OT ine Vunnlson <br />AW -4 <br />AW -5 <br />AW -6 <br />AW -11 <br />AW -12 <br />I AW -16 <br />AW -17 <br />Min <br />2900 <br />3100 <br />3300 <br />480 <br />485 <br />740 <br />200 <br />Max <br />5300 <br />6800 <br />5600 <br />1480 <br />760 <br />740 <br />272 <br />Average <br />3786 <br />5464 <br />4555 <br />929 <br />609 <br />740 <br />236 <br />Gob Pile Leachate 2 <br />1190 <br />1190 <br />1190 <br />1190 <br />1190 <br />1190 <br />1190 <br />AW -15 has been dry during all monitoring events. <br />The average conductivity at the upstream North Fork of the Gunnison River <br />monitoring station for the baseline period (2008 AHR) is 180 umhos /cm. The <br />following table presents the estimated affect the coal pile and gob pile <br />leachate will have on the quality of water in the North Fork of the Gunnison <br />River at low flow: <br />n <br />U <br />VrIU Nor[n rorK OT ine Vunnlson <br />raver <br />Flow gpm <br />Flow (cfs) <br />Conductivity <br />(umhos /cm) <br />North Fork <br />11,220 <br />25.00 <br />180 <br />Gob Leachate Discharge <br />50.9 <br />0.11 <br />1190 <br />Coal Pile Leachate <br />4.7 <br />0.01 <br />505 <br />Combined Flow <br />11,275.6 <br />25.12 <br />184.7 <br />Based on a combined 55.6 gallon per minute flow rate through the coal <br />stockpile and gob pile, the potential impact to the North Fork of the Gunnison <br />River that may result from alluvial ground water migration is minimal as <br />shown above. Additionally, the actual leachate flow through the gob piles is <br />likely to be minimal considering a curve number in excess of 90 is used to <br />predict surface run -off. The conductivity of the alluvial well water is greater <br />than the predicted leachate that could impact the wells except for AW -16 and <br />AW -17. <br />- - -- Predicted based -on- conductivity measurements from Upper B -Seam samples -of roof, floor -- - <br />and interburden. <br />PR -12 2.05-112 02/10 <br />,APfR6VC,D <br />11 114 1/0 <br />