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because they are the only two wells in the northwest portion of the permit area open to the Dakota <br />coal. Generally (in the Dakota coal) static water levels are slightly deeper than the overburden so <br />the potentiometric surface in the vicinity of the multiple completion wells may have a slightly higher <br />water surface elevation than the Dakota coal. <br />Ground water in the Dakota coal is confined in all of the areas monitored. The flow in the Dakota <br />coal aquifer is generally from the northeast to the southwest. The average water level gradient is <br />.0297 fUft with a range between .0228 fUft and .0343 ftlft. Recharge to the Dakota coal is generally <br />from the agricultural crop areas situated to the northeast and from vertical leakage from the <br />irrigation ditches and flood irrigation via overlying units. Discharge mainly occurs along the draws <br />where the Dakota aquifer intersects the ground surface and by discharge to contiguous aquifers. <br />Underburden. The potentiometric surface map of the underburden is presented on Map 2.04.7-4. <br />The water level contours were constructed based on September, 1987 water level data from eight <br />underburden monitoring wells. <br />Ground water in the underburden is under confined conditions. Flow in the underburden is from <br />• the northeast to the southwest. The average water level gradient is .0301 with a range between <br />.0237 and .0368. The primary recharge area is located northeast of the mine via leakage from the <br />overlying units. Discharge occurs in the draws where the underburden aquifer intersects the <br />ground surface and to contiguous aquifers. The mining operation at the New Horizon 1 area <br />appears to have had no effect on the underburden ground water potentiometric surface. <br />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 Svstem 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 />• Revised 18 Aug 2003 2.[14.7-7 <br />