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• .0375 ft/ft. <br />Dakota Coal. The potentiometric surface map of the Dakota coal is presented on Map 2.04.7-3. <br />The water level contours were constructed based on the static water level measurements collected <br />in September, 1987 from seven Dakota coal monitor wells and two multiple completion <br />(overburden and Dakota coal) monitor wells. It was necessary to include the two multiple <br />completion monitor wells (GW-N8 and GW-N9) in the Dakota coal potentiometric contour map <br />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 ft/ft and .0343 ft/fr. 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 />• <br />REVISED JULY 2006 2.04.7-12 <br />