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60 Groundwater <br />Water level data from the pumping test (hydrographs and drawdown curves) for all <br />groundwater observation points are presented in Appendix 5.H. Drawdowns in the <br />observation wells vary as a function of distance from the pumping well and the relative <br />permeabilities of the stressed units. The greatest drawdowns were observed in <br />piezometers monitoring the Fab, F5 /176, and Gb coals. The greatest amount of <br />drawdown (135 ft) was observed in the Gb coal seams at VWP -1, which, at 75 ft of <br />separation, is the piezometer closest to C -04 -1613. Drawdowns observed in the lower - <br />permeability interburden below the Gb and Fab coals are indicative of a strong hydraulic <br />connection between the coal and the adjoining interburden. This correlation was <br />observed at VWP -1, VWP -2, VWP -5, and VWPC- 04 -17. <br />Coals with lesser amounts of drawdown include the Gc, F7, Ho, and E2 seams. Very <br />little drawdown was observed in the F sandstone and other sand units below thin coal <br />seams that had minimal drawdowns during the test period. The drawdown in the <br />sandstone and less permeable coal units is attributed largely to vertical flow from the <br />sandstone units into the more conductive coal seams. Therefore, aquifer parameters <br />were calculated for the F/G and Fab coal sequence as well as more discrete intervals for <br />the Ga, Gb, and Gc coal seams. Hydraulic parameters from the long -term pumping test <br />are presented in Table 5.6. The aquifer test also provided significant information on the <br />relative contributions to flow of the various tested units and the overall behavior of the <br />water - bearing units. These observations are listed and discussed in the hydrogeologic <br />conceptual model (Section 5.3). <br />5.2.8 Summary of aquifer test results <br />Results from the historic and recent well tests indicate that the most permeable bedrock <br />units are within the F/G sequence (Table 5.7). The sandstone units have lower <br />permeabilities than the coal seams. Hydraulic conductivities for wells in the vicinity of <br />C- 04 -16B are listed in Table 5.6. Table 5.7 summarizes the range and geometric mean <br />of hydraulic conductivities for specific units of interest in the Collom Pit area. Data in <br />Table 5.7 are shown graphically in Figure 5.9. The coal seams have average hydraulic <br />conductivities ranging from approximately 0.187 to 0.039 ft/day. The highest hydraulic <br />conductivities were observed in the Fab and G seams. The sand units have average <br />hydraulic conductivity values ranging from a high of approximately 0.008 ft/day <br />(F sandstone) to 0.0017 ft for the H sandstone. <br />2572 -R2 <br />Water Management Consultants <br />Colowyo Coal Company <br />