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The mining in the EMD will result in subsiding areas where springs exist. TC's experience is that there will be a <br />temporary disruption in flow, and then recovery of the springs. The reader is referred to TC's 1996 AHR for a <br />further discussion of the recovery of springs SW1 and SW2. No long -term impacts are anticipated to the springs <br />in this area. <br />The present interpretation of the impacts of subsidence on the water - bearing strata in the study area is supported <br />by numerous studies in various coalfields worldwide_ <br />Subsidence Impacts on Ground Water Ouality <br />The potential impacts of subsidence on ground water quality could develop in the following ways: <br />• Caved overburden materials replace part of the coal seam unit; and <br />• Fracturing develops a new hydraulic connection between units with different water quality. <br />The first potential impact is applicable only in cases where the coal seam acts as a unit, which is not the case in <br />the study area. The second example is more common in cases where several units with different water quality <br />are, present. In the Foidel, Middle and Fish Creek alluvium areas, the potential interconnection could be, for <br />example, between the Twentymile Sandstone and the alluvial unit. One apparent impact to the Twentymile <br />Sandstone from subsidence is the drop in water level in Monitoring Well 006- 82 -48A. This drop in water level <br />is attributed to a possible mechanical failure of the casing and loss of the well seal, or increased porosity <br />resulting in a lowering of the water level. Monitoring Well 006 -82 -48A was installed in a borehole that had <br />originally been drilled through the Twentymile Sandstone to the Wadge Seam. Although subsidence may have <br />resulted in the loss of this well, no impacts on the ground water quality in the Foidel and Middle Creek <br />alluviums are anticipated. This conclusion is consistent with experience in other coal fields. <br />Most of the studies of subsidence effects of surface and ground water quality in the Appalachian coal fields <br />concluded that no significant long -term effects on water quality were observed, which confirms observations <br />from the Foidel Creek Mine (Owili -Eger, 1987; Moebs and Barton, 1985; Schultz, 1988). After over 15 years of <br />monitoring of alluvial and bedrock wells (see Annual Hydrologic Reports), no impacts to the water quality of <br />the Trout Creek Sandstone, Twentymile Sandstone, or overlying alluvial aquifers has been found. The only <br />impacts to sub - surface water quality have been an increase in TDS and iron in the water stored in the mine. In <br />addition, high TDS water from the adjacent surface mine has moved into the underground workings (see in <br />Effects on Ground Water Quality of Aquifers). <br />SURFACE WATER SYSTEM <br />A detailed discussion of surface water hydrology is presented under Rule 2.04.7(2). The proposed life -of -mine <br />area for the Foidel Creek Mine is located within the Foidel Creek and Fish Creek surface water- drainages. <br />Therefore, any mining impacts on surface water systems will be confined to these drainages and their receiving <br />streams. <br />Potential Minim- Related Impacts on Surface Water Ouant%ty and Quality <br />The planned underground mining and associated activities have the potential of creating changes in the existing <br />surface water quantity in terms of runoff volumes, flow rates, and direction and location of surface water <br />drainage. The potential mechanisms of impact are: <br />1) Direct disturbance of surface flow channels <br />2) Discharge of mine inflow water to surface water drainages via sedimentation ponds or direct discharge <br />3) Detention of surface runoff in sedimentation ponds and related evaporation loss <br />4) Diversion of overland flow with ditches <br />5) Induced recharge or discharge by underground mine dewatering <br />TR13 -83 2.05 -149 11/03/14 <br />