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Monitor Well GW-N11 was omitted from use in the construction of the underburden potentiometric <br />contour map. This monitor well had enigmatic static water level readings when compared to the <br />rest of the underburden monitor wells. Because of the poor completion record and the anomalous <br />static water level readings, it was decided to exclude this well from the potentiometric surface map. <br />Effects of the Irrigation System on Potentiometric Surfaces. During the summer months <br />when flood irrigation is in full swing, each of the aquifers monitored exhibits a rise in static water <br />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 <br />flood irrigation waters. Recharge also results from infiltration of precipitation and subsurface <br />ground water inflow. The Dakota coal and the underburden are generally confined but there is <br />enough leakage between the adjacent units to afford some recharge. <br />Recharge to the alluvial aquifers is by discharge from the bedrock aquifers and infiltration of <br />surface waters (return irrigation water and precipitation) <br />Hvdroloaic 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 cones of depression in these aquifers, with lowtransmissivities, <br />would be very small in areal extent. There are no faults, angular unconformities, or <br />nonconformitiestyithin the permit area which would act as impermeable boundaries. Some minor <br />lithologic boundaries are present in the bedrock aquifers as a result of their environment of <br />deposition. There is a no-flow boundary in the unsaturated units in the eastern portion of the New <br />Horizon 1 permit area (NW'/<, Section 31, R15W, T4iN and NE'/< Section 36, R16W, T41N). <br />Constant and semi-constant discharge boundaries occur where the aquifers crop in the bottom of <br />the draws. <br />Revised 25 Jul 2002 2.l)4.7-8 <br />