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. level. This ground water shallowing creates a uniform rise in the potentiometric surface. Perusal <br />of the water level data indicates that the rise in the potentiometric surface during the summer <br />months has a negligible effect on the ground water gradients. <br />Recharge. A predominate source of recharge to the shallow bedrock aquifer system at the New <br />Horizon 1 & 2 mining areas is leakage from the irrigation ditch system and infiltration of excess flood <br />irrigation waters. Recharge also results from infiltration of precipitation and subsurface ground <br />water inflow. The Dakota coal and the underburden are generally confined but there is enough <br />leakage between the adjacent units to afford some recharge. <br />Recharge tothe alluvial aquifers is by discharge from the bedrock aquifers and infiltration ofsurface <br />waters (return irrigation water and precipitation). <br />Hydrologic Boundaries <br />Aquifer testing of the low yield strata at New Horizon 1 & 2 did not yield the presence of any major <br />hydrologic boundaries. Bedrock aquifer testing of any duration would not yield the presence of <br />hydrologic boundaries because the conesofdepressionintheseaquifers,withlowtransmissivities, <br />would be very small in areal extent. There are no faults, angular unconformities, or nonconformities <br />within the permit area which would act as impermeable boundaries. Some minor lithologic <br />boundaries arepresentinthebedrockaquifersasaresultoftheirenvironmentofdeposition. There <br />is a no-flow boundary in the unsaturated units in the eastern portion of the New Horizon 1 permit <br />area (NW'/<, Section 31, R15W, T41 N and NE'/<Section 36, R16W, T41 N). Constant and semi- <br />constantdischarge boundaries occur where the aquifers crop in the bottom of the draws. <br />Infiltration and Permeability of the Unsaturated Zone <br />Using the soil hydrologic properties defined by the Soil Conservation Service ofthe U.S. Department <br />of Agriculture, it is possible to estimate the infiltration rates of soils occurring within the vicinity of the <br />New Horizon 1 & 2 mining areas. The New Horizon 1 & 2 soils have been mapped at a scale of 1 <br />inch equals 400 feet. The soils maps are included in Section 2.04.9 ofthis permitapplication. The <br />unsaturated zone can be divided into two categories. Thefirstistheundisturbedareas. AttheNew <br />Horizon 2 mining area, the majority of the soils have a moderate (0.6 - 2.0 in/fir} permeability and <br />infiltration rate. A minor amount of the soils have a moderately rapid (2.0 - 6.0 in/hr) permeability <br />• (REVISED 6/28/07) 2.04.7-$ <br />