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la <br /> similarity of the overburden characteristics at the two mines. In accord- • <br /> ante with our experience elseo-rhere, the most transmissive strata in the <br /> profile appear to De the coal seams encountered during drilling of wells <br />~ <br />-~ <br /> ~ <br />LA 218A and LA 221A. Therefore, the second step in testinc the extrapo- <br /> lation 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~4. The location of the three wells utilized in the bedrock <br /> aquifer tests are shown on Plate 18 and the test data and completion details <br /> are included as Appendix tables B1 through 63. Wells LA 218A and LA 221A <br /> are redrills of wells 218 and Z21 for which cores and strip loos were al- <br /> ready available. <br /> Our experience with a large number of single 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 from 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 out into the aquifer. ,The subsequent recovery response <br /> . <br />is then influenced by the hydraulic properties in a larger volume of aquifer <br /> than would be the case fora short pumping period. Also, water samoles <br /> collected near the termination of a prolonged pumping period yield a better <br /> representation of the aquifer water. Such a test was originally planned <br /> for the bedrock wells established in this study. However, bath wells <br /> LA-221A and LA 218A produced sufficient gas to seve 'srupt the normal <br /> operation o _ e o~ a ooin ing was possible for~on y a <br /> f minutes before t e~ume-~hecame gas locked and the discharge rapidly de- <br />~ <br />- <br /> ~ <br />clined toward zero. Instantaneous drawdown (or slug) tests were performed <br /> <br /> on these wo we s, therefore. Production from well LA 264 proved to be <br /> sufficient to permit a standard drawdown, at constant discharge, test to <br /> be performed. <br /> The analysis of the recovery data following a rapid drawdown of <br /> s <br />= 74.20 ft. in LA 221A is shown in Figure 3. The dots represent the <br /> o <br /> data and the solid curve is the theoretical match curve (Cooper, et al., <br /> 1967). The corresponding results for the test at LA 218A are shown in <br /> figure 4. In bath wells, the open hole available for water entry included <br /> • <br /> the Maxwell seam and various thickness of shale, siltstone, and sandstone <br />