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4~ 14 <br />Most of the boreholes were drilled with the use of air as a drilling fluid; and most of the <br />• boreholes were geophysically logged. The geophysical logs consist usually of gamma•gamma, <br />density and resistivity logs. The presence of water and its level, or absence of groundwater, is <br />indicated by electric resistivity logs. The interpretation depends on the type of medium used for <br />drilling. If water was used for drilling, the interpretation of electric resistivity log cannot <br />determine the difference in level of ground water or drilling fluid. Therefore, it is necessary to <br />use not only geophysical logs for the interpretation but also driller logs. <br />Because most of the bore holes were drilled with air with some occasional use of foam, the <br />electric resistivity logs indicate in most cases the depth to water table. Using data from <br />resistivity logs, it was possible to develop a map, Figure 4.2-3, showing approximately the <br />unsaturated and saturated zones of the Cameo Coal Seam. <br />For the McClane Canyon Mine permit area, the results of the interpretations of geophysical <br />logs were confirmed in two exploration bore holes. Borehole 7-21-3 was drilled on the mine <br />bench to help determine the characteristics of the graben. The hole was collared about ten feet <br />below the cameo seam and did not encounter water until a depth of 200 feet. This indicates <br />• that the saturated sandstone strata are about 210 feet below the cameo coal seam, and <br />therefore, beyond any possible impact caused by mining activities. Borehole 7-15.3.3, located <br />in the southwest quarter of Section 15, was drilled about 38 feet below the Cameo coal seam <br />and was dry. <br />An absence of springs or seeps was observed in the area during various seasons of the <br />year. From the experience in other mines in the Book Clrffs Coal Field, direct observations on <br />the surface, and the results of exploration borings, it is possible to anticipate that no significant <br />quantities of groundwater will be encountered above local stream beds during mining. <br />4.2.2.1 CHARACTERISTICS OF AQUIFERS <br />The occurrence of groundwater in the lease area is controlled mostly by the combination of <br />local topography, stratigraphy and geologic structure. Water bearing strata are developed in <br />alluvial sediments along the local streams and in the bedrock. The bedrock aquifers are <br />contained in sandstone strata and locally in the coal seams. <br /> <br />M` Volume 1 4 - 29 -96 <br />