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Groundwater occurs in both the Sudduth coal seam and the lenticular sandstones of the Coalmont <br />Formation. Wyoming Fuel has conducted two aquifer tests (slug tests) on two different <br />monitoring wells, lA and SC, completed in the Sudduth coal seam. The aquifer test conducted <br />by and for Wyoming Fuel indicates that the Sudduth coal is poor aquifer, except in areas of <br />faulting where there is an increase secondary permeability. The Sudduth coal seam is the only <br />rock stratum within the lower Coalmont Formation with a large enough azeal extent to be <br />considered a regional aquifer. Flow within this aquifer is controlled by the dip of the coal bed. <br />Regional flow within the coal is downdip of the axis of the Bourg Syncline and the Johnny <br />Moore Syncline, and then down the plunge of the synclinal axes. The coal seam is overlain and <br />underlain by confining siltstone and shale strata which act as aquitards and aquicludes. The <br />confining layers restrict the coal recharge zone to a narrow outcrop and subcrop band and also <br />produces the artesian conditions observed in monitoring wells. <br />No permitted water wells are completed within the Sudduth coal seam. <br />The lower Coalmont Formation which overlies the Sudduth coal consists of interbedded and <br />lenticular calcareous sandstones and siltstones. Groundwater within this stratum is localized in <br />the lenticular sandstones. The siltstones which intertongue with the lenticulaz sandstones act as <br />aquitazds which restrict the vertical and horizontal movements of groundwater to and from these <br />sandstones. <br />Wyoming Fuel Company conducted both laboratory permeability tests on core samples and slug <br />aquifer tests on monitoring holes completed in the lower Coal Formation. The laboratory test <br />indicate that both the sandstones and siltstones have very low permeabilities, 0.05 and 0.02 <br />millidazcies, respectively. Slug tests conducted by Wyoming Fuel at well sites 1B and SC <br />yielded higher permeabilities, 1.09 millidarcies, or 0.02 gpd/ft2 for 1 B and 0.01 gpd/ftz for SC. <br />The higher permeabilities measured in the aquifer tests were attributed to the higher secondary <br />(fracture) porosities within the bore hole. Higher permeabilities were measured for this strata in <br />pumping tests conducted by Kerr Coal Company and the U.S.G.S. (0.37 to 7.5 gpd/ft2, <br />respectively). Kerr Coal Co. also noted that fractures greatly increase the aquifer's permeability <br />and that the sandstones, in the absence of fractures, have low permeabilities. <br />The only permitted water well in the area is completed in a 26 foot lenticular sandstone of the <br />Coalmont Formation. This water well is located in Section 35, T9N, R78W and is owned by <br />Kerr Coal Company. This sandstone tapped by the Kerr well is s[ratigraphically higher than the <br />strata that was disturbed during mining at the Kerr, Wyoming Fuel, and Bourg mines. <br />The Upland Terrace deposits which unconformably overlie the Pierre shale and the Coalmont <br />Formation have sufficient permeability to store and transmit water. Groundwater in this aquifer <br />is under unconfined water table conditions. Recharge to this aquifer is primarily through <br />infiltration during snowmelt and during sporadic precipitation events. Groundwater within these <br />deposits flows down along the contact between the permeable terrace deposits and the bedrock. <br />Springs and seeps develop where this contact has been adjacent to the Wyoming Fuel mine on a <br />Bourg Strip Mine. C-81-021 9 August 4, 1998 <br />