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- I ,_ stone un derburden acts as an nguiclude, preventing dewaterinp of the Sandy Ple tuber into the pit. Only nu:nimal disturbance trill occur to thi:; siltstonn. aquiclude during mining. Faults which cut through the mine area will, however, transmit small quantities of water from the Upper Sandy nfember to the pit. This has occured in Pit 1, and is expected to occur in Pit 2. [Jyoming Fuel has estimated inflows to Pit 2 to be between 0 and 10 glom. No wells have been completed into the Upper Shale Ffember of the Pierre Shale to date due to its salinity and the low yields. No seeps or springs emirate from this unit within t/re mine plan and adjacent areas. Ground water occurs in both the Sudduth coat seam and the lenticular sandstones of the Coalmont Formation. [ryoming Fuel has conducted two aquifer tests (slug tests) on two different monitoring wells, IA and SC, completed in the Sudduth coal seam. The aquifer test conducted by and for Wyoming Fuel indicates that the Sudduth coal is a poor aquifer, except in areas of faulting where there is an increased secondary permeability. The Sudduth coal seam is the only rock strata within the lower Coalmont Formation with a large enough areal extent to be considered a regional aquifer. Flow within this aquifer is controlled by the dip of the coal bed. Regional flow within the coal is down dip to the axis of the Johnny hfoore Sun cline and then down the plunge of the synclinal axis. The coal seam is overlain and underlain by confining siltstone and shale strata which act as aquitarrls acrd aguicludes. The confining layers restrict the coal recharge zone to a narrow outcrop and subcrop band and also produces the~astesian conditions observed in monitoring wells. No permitted water wells arc completed with the Sur]duth coal seam. The lower Coalmont Formation which overlies the Sudduth coal consists of interbedded and lenticular cal carioas sandstones and siltstones. Ground water within this stratum is localized in the lenticular sandstones. The siltstones which intertongue with the lenticular sandstones act as aquitards which restrict the vertical and horizontal movement of ground water to and from these sandstones. Wyoming Fuel has conducted both laboratory permeability tests on core samples and slug aquifer tests on monitoring holes completed in the lower Coalmont Formation. Results are contained in Tables I4, 15 and 18 of Appendix C. The laboratory tests indicate that both the sandstones and siltstones have very 1o~~r permeabilities, 0.05 and 0.02 millidarcies respectively. Aquifer tests conducted at well sites 18 and SC yielded higher permeabilities, i.00 mill.idarr`.ies, or 0.02 ypd/ft2 for 1B and O.OZ gpd/ft2 for SC. The higher permeabilities Fran the aquifer tests were attributed to the higher secondary (fracture) porosities within the bore hole. Higher perme- abilities crere measured for this strata in pumping tests conducted by Kert Coal Company and the U.S.G.S. to t/re north of the fJyoming Fuel operation, 0.37 to 7.5 gpd/ft Kerr also noted that fractures also greatly increase the aquifer's perme- ability and that the sandstones, in the absence of fractures, have low permeabilities. The only permitted water well in the area is completed in a 26 foot lenticular sand- stone of the Coalmont Formation. This water well is located in Section 35, T9N, R78W and is owned by the Kerr Coal Company. This sanrlstonc tapped by the Kerr well is stratigraphically higher than the strata which will be disturbed during mining at the Kerr and Wyoming Fuel mines.