Laserfiche WebLink
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 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 to the alluvial aquifers is by discharge from the bedrock aquifers and infiltration of surface <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 cones of depression in these aquifers, with low transmissivities, <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 are present in the bedrock aquifers as a result of their environment of deposition. 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, R1 5W, T41 N and NE% Section 36, R1 6W, T41 N). Constant and semi- <br />constant discharge boundaries occur where the aquifers crop in the bottom of the draws. <br />Infiltration and Permeabilitv of the Unsaturated Zone <br />Using the soil hydrologic properties defined by the Soil Conservation Service of the U.S. <br />Department of Agriculture, it is possible to estimate the infiltration rates of soils occurring within the <br />vicinity of the New Horizon 1 & 2 mining areas. The New Horizon 1 & 2 soils have been mapped <br />at a scale of 1 inch equals 400 feet. The soils maps are included in Section 2.04.9 of this permit <br />application. The unsaturated zone can be divided into two categories. The first is the undisturbed <br />areas. At the New Horizon 2 mining area, the majority of the soils have a moderate (0.6 - 2.0 in/hr) <br />2.04.7-14