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• Trinidad Sandstone is underlain by the 3,900 foot thick Pierre Shale which <br />is considered impermeable relative to groundwater movement. Information <br />obtained from oil and gas exploration drilling in the region indicates a <br />hydraulic conductivity for the Trinidad Sandstone of approximately 10' to <br />10'' feet per day. Given these low conductivity values and its relative <br />depth, the Trinidad Sandstone cannot be considered an effective aquifer <br />for groundwater use over most of the basin. Some groundwater use from the <br />Trinidad Sandstone does occur immediately adjacent to the Arkansas River <br />with well yields ranging from 20 to 100 gallons per minute. However, <br />these wells are relatively shallow, occur near the outcrop of the Trinidad <br />Sandstone and probably reflect some interconnection between the alluvium <br />of the Arkansas River and this stratigraphic unit. <br />The loadout area is located on an upper colluvial/alluvial terrace of the <br />Oak Creek drainage. colluvial/alluvial deposits in this area are similar <br />to the terrace deposits previously described, being of limited thickness <br />• and draining to the surface water system along exposed margins where the <br />deposits are intersected by ephemeral streams. In the adjacent area, <br />colluvial/alluvial deposits occur within the Oak Creek floodplain. <br />However, as described in Section 2.06.8, Surface Coal Mining and <br />Reclamation Operations on Areas or Adjacent to Areas Including Alluvial <br />Valley Floors, these deposits do not appear to store or transmit <br />significant quantities of groundwater as indicated by the lack of sub- <br />irrigation. <br />In summary, there are no stratigraphic units in the mine, loadout, or <br />adjacent areas which can be considered as aquifers based upon the <br />definition of Rule 1.4(14). A number of the stratigraphic units do have <br />the capability to store and transmit water. However, these capabilities <br />along with the potential for beneficial use are limited by lack of lateral <br />continuity, limited areal extent and relatively low horizontal and <br />vertical hydraulic conductivities. <br />• Groundwater resources generally occur as isolated perched reservoirs <br />either within the stratigraphic sequence where favorable localized <br />lithologic and recharge characteristics exist or where the stratigraphic <br />sequence has been modified by underground mining. Underground mining <br />2.04.7-5 <br />