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REPORT FOR <br />PEABODY COAL COMPANY <br />ON HYDRAULIC CONDUCTIVITY <br />TESTING AT SENECA MINE <br />HAYDEN,COLORADO <br />INTRODUCTION <br />The purpose of this testing was to establish the hydraulic characteristics <br />of subsurface materials at two locations. The first well, GWS-22 was <br />completed predominantly in replaced spoil, with the bottom penetrating <br />undisturbed shale by several feet. The second well, GWS-33, was completed <br />in undisturbed, fine grained alluvium west of the Seneca Mine offices. Logs <br />of both wells are attached. <br />Point Permeability Testing <br /> <br />There are many situations where aquifer pump testing is not practical or • <br />justifiable. In particular, it is difficult to conduct pump tests on low <br />yield (low permeability) formations or formations with little or no water <br />contained within them. In such cases an idea of formation permeability may <br />be obtained using a slug, reverse slug or constant head test. Such procedures <br />are run by either removing or adding (instantaneously) a quantity of water, <br />or by adding water at a rate which will maintain a constant head in the well, <br />piezometer or borehole. Amore sophisticated va-•iation on the constant head <br />test is the addition of one or more observation wells all with the test well <br />receiving water. In that situation the test becomes a reverse pump test which <br />may be used with Theis curve matching to obtain storativity or (for water <br />table situations) effective porosity. <br />Many methodologies can be found in the literature for point permeability <br />testing. A1) of them involve variations on party's law or the Theis equation, <br />adjusted for hole or hydraulic geometry and variations in head. The method- <br />ologies are too numerous to describe in detail but may may be found in refer- • <br />ences such as Lohman, 1972, C.A. Black et al, 1965, Cedergren, 1967, and <br />Bouwer, 1978. <br />?-9-20 <br />