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permeability and infiltration rate. A minor amount of the soils have a moderately rapid (2.0 - 6.0 <br />in/hr) permeability and infiltration rate. The subsurface strata in these areas consist predominately <br />of tightly cemented sandstones and shales which act as barriers inhibiting vertical percolation. <br />However, field observation of exposed outcrops and aquifer analysis data indicate that secondary <br />porosity (weathered and fractured bedrock strata) play a significant role in allowing vertically <br />infiltrating ground water to infiltrate through the unsaturated to the saturated zone. Quantification <br />of the transmissivity and permeability associated with secondary porosity is difficult because of the <br />lack of reliable aquifer analysis techniques to determine secondary porosity in low yielding aquifers. <br />The entire study area is impacted by irrigation which is a primary source of infiltrating water. <br />Infiltration as a result of precipitation is a component of recharge in the Nucla area, but the majority <br />of infiltration comes from irrigation. The large majority of the soils in the mining area have a slow <br />to medium runoff potential. <br />The second area of concern is the reclaimed areas. The strata at the New Horizon 1 & 2 mining <br />areas are quite similar. The lithologic logs indicate that the spoils material will generally be <br />composed of more than 50 percent fragments of blasted sandstone with lesser amounts of shale, <br />bentonite and gypsum. Sections 2.05.3 and 2.05.4 describe the details of the mining and <br />reclamation methods. Using the described mining and reclamation techniques the approximate <br />recharge capacity and permeability of the spoils material will be increased due to greater porosity <br />and hydrologic conductivities due to increased void volumes.. The resaturation rate of the spoils <br />will be quite rapid because of the irrigation occurring in the area. Infiltration resulting from <br />precipitation is only a very minor (2" per year) component, but does comprise a measurable <br />percentage of the infiltration. <br />Discharge <br />Ground water is discharged through streams, evapotranspiration, wells, springs and seeps, and by <br />subsurface outflow to contiguous aquifers to the southwest <br />Discharge rates from overburden, Dakota coal and the underburden can be calculated using <br />Darcy's law. Calculations of ground water flow (inflow) from the overburden, Dakota coal and <br />underburden indicate that the aquifers are discharging 77,058 ft3/day, 663 ft3/day, and 4,133 ft3/day, <br />respectively through the defined cross sections. Discharge from the Dakota coal and the <br />2.04.7-15