Laserfiche WebLink
the upper unit are the result of the complex three-dimensional mosaic of <br />lithologies that were deposited in the deltaic environment. The best <br />aquifers are the pro-delta sandstone strata and the coal seams. Because <br />of the complex, lenticular nature of the sandstone units and the intervening <br />shale units, permeabilities of. the upper unit vary widely both laterally <br />and vertically, (Radian, 1980). <br />The presence of joints in the sandstone and coal strata provides a small <br />amount of secondary porosity and permeability over and above the intrinsic <br />permeability of the individual litho logic units. The influence of joints <br />is more important in providing a higher cross-bedding (perpendicular to <br />bedding) permeability than in adding significant porosity to the Upper <br />Williams Fork, (Radian, 1980). <br />Below the water table, only the uppermost aquiferous units are in un- <br />confined conditions. Aquifers below the first shale unit are generally <br />under confined conditions, and in some of the more northern e:;ploratory <br />coreholes, ground water flocaed to the surface. <br />Aquifer tests for these strata have been conducted at five locations at <br />the Trapper mine. Four of these tested the Upper Williams Fork. A fifth <br />test was done on the Lower Unit of the Iilliams Fork Forr..ation, but it <br />provides useful insight into likely h}'drauli-c proFerties of the Upper <br />Williams Fork. Table 2.7-21 sun~arices these aquifer tests. Ttiis table <br />gives a range Erom 174 to 2760 gal/day/ft for the transmissivity of the <br />• ~ Q and R coal seams and adjacent sandstone aquifer. A value of 250 gal/day/f[ <br />2-460 <br />