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18 <br />similarity of the overburden characteristics at the two mines. ]n accord- • <br /> ante with our experience elsewhere, the most transmissive strata in the <br />1 ~ profile appear to be the coal seams encountered during drilling of wells <br />f LA 218A and LA 221A. Therefore, the second step in testing the e:xtrapo- <br /> lotion of experience from the Allen to the Maxwell was to conduct. "aquifer" <br /> tests of the Maxwell seam at wells LA 218A and LA 221A and of the: overburden <br /> at well LA 264. The location of the three wells utilized in the bedrock <br />1 aquifer tests are shown on Plate 18 and the test data and completion details <br /> are included as Appendix tables 81 through B3. Wells LA 218A an~i LA 221A <br />1 are redrills of welts 218 and 221 for which cores and strip logs were a1- <br />J ready available. <br /> i <br /> Our experience with a large number of s <br />ngle hole aquifer tests (i.e., <br /> no observation wells) in strata with small transmissivities has shown that <br /> the most reliable determination of transmissivity is obtained frcun recovery <br /> data following a prolonged period of pumping. The advantage gained by a <br /> substantial pumping period derives from the creation of a cone of drawdown <br /> that extends well ouL into the aquifer. The s„b~eauent recovery response <br /> is then influenced by the hydraulic properties in a larger volume of aquifer <br />. <br />• . <br />than would be the ease fora short pumping period. Also, water samples <br /> collected near the termination of ~m~ngp.~p~ping_perind~ld_a`better <br /> representation of the aquifer water. Such a test was originally planned <br />f~,~ for the bedrock wells established in this study. However, bath wells <br />Jl(~ <br />// LA1221A and LA 218A produced sufficient gas to severely disrupt the normal <br />!j~ operation of the pump to the point that pumping was possible for only a <br /> few minutes before the pump became gas locked and the discharge rapidly de- <br /> clined toward zero. Instantaneous drawdown (or slug) tests were performed <br /> on these two wells, therefore. Production from well LA 264 proved to be <br />I sufficient to permit a standard drawdown, at constant discharge, test to <br />i <br />be performed. <br /> The analysis of the recovery data following a rapid drawdown of <br /> so ~ 74.20 ft. in LA 221A is shown in Figure 3. The dots represent the <br /> data and the solid curve is the theoretical match curve (Cooper, et a1., <br /> 1967). The corresponding results for the test at LA 218A are shown in <br /> Figure 4. In both wells, the open hole available for water entry included <br />L the Maxwell seam and various thickness of shale, stltstone, and sandstone <br />