2013-10-08_REVISION - C1982056 (22)

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Degradation of alluvial water quality in Fish Creek Water will move down gradient to the natural discharge points along Fish Creek. Alluvial aquifers are recharged mainly by stream flows during high flow conditions and to a lesser degree, bedrock discharge. Given the small amount of estimated discharge, this degraded water will easily be diluted by upstream flows. Degradation of alluvial water quality in Foidel Creek Only the area near the confluence of Foidel and Middle Creeks contain adequate saturation to be measured. As with Fish Creek, the water near the confluence of Foidel and Middle Creeks will move down gradient to the natural discharge points along Middle Creek. Alluvial aquifers are recharged mainly by stream flows during high flow conditions and to a lesser degree, bedrock discharge. Given the small amount of estimated discharge, any degraded water will easily be diluted by upstream flows. Subsidence impacts to bedrock aquifer water quantity Although the applicant presents no site specific information, the predicted consequences of subsidence and effects to ground water quantity can be summarized as follows: a)Longwall operation induced subsidence creates a zone of increased permeability above the mined-out area and within a 15 to 25 degree angle of draw. b)Cracking and opening of fissures at the ground surface can occur within the zone of tensile strain. However, the depth of such subsidence fractures is limited. c)The zone of increased permeability above the longwall operation is typically 30 to 50 times the thickness of the removed strata. The thickness of the zone of increased permeability is dependent on the thickness of the removed strata; speed of mining; and geologic character of the overburden. After completion of mining, the permeability of the disturbed strata is predicted to return to close to pre-mining conditions. Subsidence impacts to alluvial water quantity Alluvial waters should not be impacted due to mining and subsidence, due to the presence of a 500-600 foot thick marine shale above the mined Wadge seam which acts as an aquiclude and minimizes the disruption in the near surface. Previous subsidence along Fish Creek in the Western Mining District recorded only minimal changes in the water levels in the alluvial aquifer in Fish Creek. Subsidence impacts to ground water quality The mine predicts that subsidence fracturing could cause a new hydrologic communication between bedrock units with different quality. However, the applicant states that monitoring do not indicate any substantial intercommunication of bedrock or alluvial aquifers. 18 Foidel Creek MineOctober 8, 2013