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K. Probable Hydrologic Consequences <br />Groundwater Consequences <br />Although several impacts on groundwater by the Southfield Mine have been predicted and <br />observed (see list below), EFCI asserts, and the Division concurs, that there are no stratigraphic <br />units in the mine, loadout, or adjacent areas which can be considered as aquifers based upon the <br />definition of Rule 1.04(14). A number of the stratigraphic units do have the capability to store <br />and transmit water. However, these capabilities along with the potential for beneficial use are <br />limited by lack of lateral continuity, limited areal extent, and relatively low horizontal and <br />vertical hydraulic conductivities. The Trinidad Sandstone or the shallow colluvial /alluvial <br />deposits could be a source for groundwater to be put to beneficial use. However, these geologic <br />units are hydraulically isolated from the mined out areas and have been unaffected by the <br />mining. <br />The following list includes several significant observations related to potential impacts of the <br />Southfield Mine on groundwater resources in the area: <br />• It was previously determined that the Southfield Mine workings had the potential to <br />deplete the quantity of groundwater through mine - induced groundwater flows. Estimates <br />were that the mining operation would induce inflows by dewatering the coal seam and the <br />associated roof and floor strata as the mine workings advanced. In addition, overlying <br />aquifers could be dewatered through subsidence - related fractures. Locally perched <br />groundwater aquifers in strata above the workings could be dewatered through <br />subsidence cracks or fractures. Thus water would drain down through the fractures to the <br />voids created by the mine. <br />• Perched aquifers in the Vermejo Formation and the overlying Raton Formation can <br />possibly be dewatered by subsidence. Wells that use these perched aquifers could <br />experience drawdown effects. However, due to the low hydraulic conductivity of the <br />associated aquifers, the fact that the aquifers in this area tend to be laterally <br />discontinuous, and the effects of past surface and underground mining, groundwater <br />impacts (both magnitude and extent) are difficult to predict. <br />• The existence of the mine workings will permanently modify the pattern of groundwater <br />flow. The flooded mine constitutes a region of essentially infinite permeability that will <br />tend to cause groundwater to preferentially pass through the workings. The water passing <br />through the flooded mine could potentially be degraded in quality, relative to that in the <br />undisturbed strata. <br />• During operation, the mine had sources of inflow in both the north and south sections of <br />the mine. The primary source of water entering the mine appeared to be from the <br />abandoned workings nearby and above the mine. Quantities of mine inflows appear to <br />have decreased from 1995 to 2000. According to EFCI, this decrease was most likely due <br />to the mine reaching equilibrium with the surrounding groundwater such that water no <br />longer rises into the accessible area of the mine. <br />• The Corley Company Well completion zone in the Raton Formation is at least 400 feet <br />stratigraphically above the coal seams that were mined. Drawdown effects to the Corley <br />21 <br />