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• multiple completion (overburden and Dakota coal) monitor wells. It was necessary to <br />include the two multiple completion monitor wells (GW-N8 and GW-N9) in the Dakota coal <br />potentiometric contour map because they are the only trvo wells in the northwest portion of <br />the permit area open to the Dakota coal. Generally (in the Dakota coal) static water <br />levels are slightly deeper than the overburden so the potentiometric surface in the <br />vicinity of the multiple completion wells may have a slightly higher water surface <br />elevation than the Dakota coal. <br />Ground water in the Dakota coal is confined in all of the areas monitored. The flow in <br />the Dakota coal aquifer is generally from the northeast to the southwest. The average <br />water level gradient is .0297 ft/ft with a range between .0228 ft/ft and .0343 ft/f t. <br />Recharge to the Dakota coal is generally from the agricultural crop areas situated to the <br />northeast and from vertical leakage from the irrigation ditches and flood irrigation via <br />overlying units. Discharge mainly occurs along the draws where the Dakota aquifer <br />intersects the ground surface and by discharge to contiguous aquifers. <br />Unde rburden. The potentiometric surface map of the underburden is presented on Exhibit <br />• 7-4. The water level contours were constructed based on September, 1987 water level data <br />from eight underburden monitoring wells. <br />Ground water in the underburden is under confined conditions. Flow in the underburden is <br />from the northeast to the southwest. The average water level gradient is .0301 with a <br />range between .0237 and .0368. The primary recharge area is located northeast of the mine <br />via leakage from the overlying units. Discharge occurs in the draws where the underburden <br />aquifer intersects the ground surface and to contiguous aquifers. The mining operation at <br />the Nucla Mine appears to have no effect on the underburden ground water potentiometric <br />surface. <br />Monitor Well GW-N11 has been omitted from use in the construction of the underburden <br />potentiometric contour map. This monitor well has enigmatic static water level readings <br />when compared to the rest of the underburden monitor wells. The completion information an <br />this monitor well (see Appendix 15-2) is inadequate. Because of the poor completion <br />record and the anomalous static water level readings, it was decided to exclude this well <br />from the potentiometric surface map. <br />• Effects of the Irrigation System on Pote ntiometric Surfaces. During the summer months <br />7-11 Revised 04/11/88 <br />