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29 <br /> shale and siltstone-sandstone together with the thicknesses of these two <br /> types of strata. The geometric mean permeability of the 23 values of <br /> vertical permeability measured in the Raton formation (Table 1 ) is 0.39 <br /> milli-darcys. This converts to a vertical hydraulic conductivity to water <br /> ! at 63° F of 0.001 ft/d. and applies to the sandstone-siltstone strata. The <br /> J corresponding value for the shale is 0.00013 ft/d. (Table 1 ) . The thickness <br /> of shale and sandstone-siltstone encountered in various drill holes ranges <br /> widely. However, examination of several geophysical and lithologic logs <br /> suggests that the first 225 ft. above the coal contains approximately 50 <br /> _ percent shale and 50 percent siltstone-sandstone. Thus , the effective mean <br /> conductivity to water flowing normal to the bedding planes is (McWhorter and <br /> Sunada, 19M. -- <br /> Ka Ll + L2 112 2+5 113 - 2.3x10-4 ft/d. <br /> K1 K2 0.001 0.00013 <br /> The vertical hydraulic conductivity computed in this manner is observed to <br /> agree very closely with that obtained using the drawdown in LA 218A. <br /> The current Maxwell Mine extends over an area of approximately <br /> 3.4x106ft2. Using a 65 percent extraction factor, the exposed roof area is <br /> estimated to be 2.2x106ft2. The current perimeter of the workings forms a <br /> rectangle with a perimeter length of 8700 ft. Eventually, the Maxwell Mine <br /> may encompass 6 sq. mi . with an exposed roof area of 1 .lx108ft2 and a peri- <br /> meter length of 4.6x104ft. <br /> The calculations of mine inflow are made for three different cases, <br /> differentiated by the value of coal transmissivity used. The model para- <br /> meters for each case are summarized in Table 3. The transmissivity for <br /> i Case III is the mean of the two measured values. <br /> i, <br /> I <br /> 1 <br /> 4 <br /> i <br />