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. ~ • ' / • <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 tfre 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 />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 />vridely. 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 flo~++ing normal to the bedding planes is (t•1cWhorter and <br />Sunada, 1977). <br />K L = 225 2,3x10-q ft/d. <br />i a Ll + L2 112 + 113 <br />Kl KZ 0.'JOl 0.00013 <br />The vertical hydraulic conductivity computed in this manner is observed to <br />agree very closely with that obtained using the dravrdown in L1 218A. <br />~' <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 r•rorkings forms a <br />rectangle with a perimeter length of 8700 ft. Eventually, the Max•++ell Mine <br />may encompass 6 sq. mi, with an exposed roof area of 1.1x108ft2 and a peri- <br />l meter length of 4.6x104ft. <br />f The calculations of mine inflow are made for three different cases, <br />differentiated by the va1•ue of coal transmissivity used. The model para- <br />meters for each case are summarized in Table 3. The transmissivity for <br />j Case III is the mean of the two measured values. <br /> <br />.... <br />