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Detention of surface water runoff in sedimentation ponds and related evaporation loss <br />Treatment of disturbed azea runoff will cause a decrease in peak flows in the Fish Creek and <br />Foidel Creek watersheds. However, any decrease due to retention in sedimentation ponds <br />would be offset by increased water downstream if mine water was discharged from the <br />underground workings. Increased levels of suspended solids will be minimized due to <br />sedimentation ponds and NPDES effluent limitations established for each point-source <br />discharge from the mining operation. <br />Diversion of overland flow with ditches <br />Diversions will deprive small azeas of water but will not significantly reduce flows <br />downstream. <br />Induced rechazge or dischazge by underground mine dewatering <br />Mine dewatering can cause changes in the natural process of stream discharge and rechazge. <br />Mine dewatering and gradient reversal may cause small decreases in Fish Creek and Foidel <br />Creek stream flows in and azound the mined azea. Increased or modified recharge is also <br />possible due to subsidence. Due to the small areal extent and the shale aquitazds between the <br />Wadge coal and the streams, increased rechazge would likely not be significant. <br />Subsidence impacts on Foidel and Middle Creeks <br />Subsidence of portions of Foidel Creek and Middle Creek will cause gradient changes in <br />short reaches of the streams. These gradient changes will result in ponding and channel <br />incision controlled by the streams' relationships to orientation of the longwall panels and <br />gateroads. Subsidence cracks in the near surface also have the potential to disrupt the <br />streamflow. Based on the presence offine-grained alluvial material, any disruption of stream <br />flows would be temporary. Site-specific experience from Foidel Creek resulted in a complete <br />loss of streamflow for approximately 24 hours followed by a recovery over the subsequent <br />two months. <br />See Section B, part IIIB of this document for more information concerning the surface and <br />ground water monitoring plan. <br />The Division has evaluated each of these impacts and finds that the operations proposed <br />under the application have been designed to prevent damage to the hydrologic balance <br />outside the proposed permit area [2.07.6(2)(c)]. <br />4. The Division finds that the affected azea is, subject to valid rights existing as of August <br />3, 1977, not within: <br />a) An area designated unsuitable for surface coal mining operations [2.07.6(2}(d)(i)]; <br />16 <br />