2010-06-04_PERMIT FILE - C1982056A (10)

Home Browse Search

The mining in the EMD will result in subsiding areas where springs exist. TCC's experience is that there will be a temporary disruption in flow, and then recovery of the springs. The reader is referred to TCC's 1996 AHR for a further discussion of the recovery of springs SW1 and SW2. No long -term impacts are anticipated to the springs in this area. The present interpretation of the impacts of subsidence on the water - bearing strata in the study area is supported by numerous studies in various coalfields worldwide. Subsidence Impacts on Ground Water Quality The potential impacts of subsidence on ground water quality could develop in the following ways: • Caved overburden materials replace part of the coal seam unit; and • Fracturing develops a new hydraulic connection between units with different water quality. The first potential impact is applicable only in cases where the coal seam acts as a unit, which is not the case in the study area. The second example is more common in cases where several units with different water quality are, present. In the Foidel, Middle and Fish Creek alluvium areas, the potential interconnection could be, for example, between the Twentymile Sandstone and the alluvial unit. One apparent impact to the Twentymile Sandstone from subsidence is the drop in water level in monitoring well 006- 82 -48A. This drop in water level is attributed to a possible mechanical failure of the casing and loss of the well seal, or increased porosity resulting in a lowering of the water level. Monitoring Well 006 -82 -48A was installed in a borehole that had originally been drilled through the Twentymile Sandstone to the Wadge Seam. Although subsidence may have resulted in the loss of this well, no impacts on the ground water quality in the Foidel and Middle Creek alluviums are anticipated. This conclusion is consistent with experience in other coal fields. Most of the studies of subsidence effects of surface and ground water quality in the Appalachian coal fields concluded that no significant long -term effects on water quality were observed, which confirms observations from the Foidel Creek Mine (Owili -Eger, 1987; Moebs and Barton, 1985; Schultz, 1988). After over 15 years of monitoring of alluvial and bedrock wells (see Annual Hydrologic Reports), no impacts to the water quality of the Trout Creek Sandstone, Twentymile Sandstone, or overlying alluvial aquifers has been found. The only impacts to sub - surface water quality have been an increase in TDS and iron in the water stored in the mine. In addition, high TDS water from the adjacent surface mine has moved into the underground workings (see in Effects on Ground Water Quality of Aquifers). SURFACE WATER SYSTEM A detailed discussion of surface water hydrology is presented under Rule 2.04.7(2). The proposed life -of -mine area for the Foidel Creek Mine is located within the Foidel Creek and Fish Creek surface water drainages. Therefore, any mining impacts on surface water systems will be confined to these drainages and their receiving streams. Potential Mining- Related Impacts on Surface Water Quantity and Quality The planned underground mining and associated activities have the potential of creating changes in the existing surface water quantity in terms of runoff volumes, flow rates, and direction and location of surface water drainage. The potential mechanisms of impact are: 1) Direct disturbance of surface flow channels 2) Discharge of mine inflow water to surface water drainages via sedimentation ponds or direct discharge 3) Detention of surface runoff in sedimentation ponds and related evaporation loss • 4) Diversion of overland flow with ditches 5) Induced recharge or discharge by underground mine dewatering PR09 -08 2.05 -149 04/27/09