1981-11-13_PERMIT FILE - C1981013 (28)

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21 immediately above and below the coal seam. The lithology of the strata exposed in the open holes is described on the data sheets in Tables Bl and B2 in Appendix B. The geophysical logs of these intervals are in the map pocket. The transmissivities determined in the tests represent weighted mean values for the open intervals. Strata immediately above and below the coal seam were purposely included in the test interval so that we could assess the potential mine inflows from adjacent roof and floor rocks should fracturing of these strata occur during mining. Well LA 264 was designed to provide an assessment of the water bearing capacity of the overburden in addition to that provided by the core per- meability tests. The completion details for this well are included on the test data sheet in Appendix B, Table B3, and the geophysical log is in the map pocket. Note that the open interval in LA 264 extends from a depth of 62 ft. to 276 ft. During drilling, water inflow was encountered at about 72 ft. and estimated to be about 15 gpm. No significant increase in dis- charge was observed over the remainder of the hole. Examination of drill cuttings and the geophysical logs indicate that the water encountered at 72 ft. was produced from a thin layer of siltstone. The gamma-gamma log indicates a washout (hole enlargement) beginning at 72 ft. and extending to perhaps 74 ft. It is probable that a thin fractured zone at this level accounts for essentially all of produced water. The "aquifer" test con- ducted at LA 264 consisted of pumping at a constant rate for more than two hours and the analysis of the drawdown data was accomplished using the standard Jacob Method (McWhorter and Sunada, 1977) as shown in Figure 5. The hydraulic properties determined from these tests are summarized in Table 2. Even the largest of the transmissivities in Table 2 is small relative to values required for most water supply purposes. The average } permeabilities K are very small and are indicative of very poor water pro- ducing capabilities. The values of K shown in the right-hand column were obtained by dividing the measured transmissivities by the thickness of the stratum believed to be contributing the water during the tests. In the cafe of wells LA 221A and LA 218A, this stratum is the coal seam and the permeability values are those for the coal . The coal permeabilities given ' in Table 2 fall within the range of coal permeabilities that we have measured at other locations. The permeability value of 45.4 ft/d is believed to �j