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Subsidence impacts to bedrock aquifer water quantity <br />Although the applicant presents no site specific information, the predicted consequences of <br />subsidence and effects to ground water quantity can be summarized as follows: <br />a) Longwall operation induced subsidence creates a zone of increased permeability <br />above the mined -out area and within a 15 to 25 degree angle of draw. <br />b) Cracking and opening of fissures at the ground surface can occur within the zone of <br />tensile strain. However, the depth of such subsidence fractures is limited. <br />c) The zone of increased permeability above the longwall operation is typically 30 to <br />50 times the thickness of the removed strata. <br />d) The thickness of the zone of increased permeability is dependent on the thickness of <br />the removed strata, speed of mining, and geologic character of the overburden. <br />After completion of mining, the permeability of the disturbed strata is predicted to <br />return to close to pre -mining conditions. <br />Subsidence impacts to alluvial water quantity <br />Alluvial water quantity should not be impacted due to mining and subsidence, due to the <br />presence of a 500-600 foot thick marine shale above the mined Wadge seam which acts as <br />an aquiclude and minimizes the disruption in the near surface. Previous subsidence along <br />Fish Creek in the Western Mining District recorded only minimal changes in the water <br />levels in the alluvial aquifer in Fish Creek. <br />Subsidence impacts to ,ground water quality <br />The mine predicts that subsidence fracturing could cause new hydrologic communication <br />between bedrock units with different quality. However, the applicant states that monitoring <br />does not indicate any substantial intercommunication of bedrock or alluvial aquifers. <br />Compliance with Basic Standards for Ground Water (Regulation 41 of the Colorado Water <br />Quality Control Commission) <br />Section 4.05.13(1) of the Regulations requires the establishment of one or more ground <br />water points of compliance (well) for an operation which has the potential to negatively <br />impact the quality of groundwater. The Wadge overburden and the Twentymile Sandstone <br />are the two major aquifers most likely to be affected by the Foidel Creek Mine. The <br />following wells serve as the Foidel Creek Mine's groundwater points of compliance: <br />97013TM (Twentymile sandstone), 008-77-58 (Wadge overburden), 008-AU3 (Fish Creek <br />alluvium), and 008 -AT -1 (Trout Creek alluvium), and 008 -AV -2 (Foidel Creek alluvium). <br />The mine's annual hydrology reports contain long-term data from these wells. These data <br />show Foidel Creek Mine is in compliance with the Basic Standards for Ground Water at the <br />groundwater points of compliance, with the following exception: <br />The ground water point of compliance well for the Trout Creek alluvium 008 -AT -1 was <br />identified as being destroyed in November of 2012. As such no data was collected for the <br />Trout Creek alluvium since April of 2012 through June of 2014. A determination of <br />Foidel Creek Mine 21 February 25, 2016 <br />