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about a month later than at wells GW -N48 and GW -N51 suggesting that rise in water level at <br />that well is due to up dip recharge. This further suggests that the coal zone at this monitoring <br />well is relatively well confined and isolated from the overburden zone and the underburden <br />(below the lowest coal seam to be mined) zone. Well GW -N54 has about 10 feet of artesian head <br />during the summer months. The amplitude of the seasonal fluctuation due to irrigation is about <br />12 feet, 19 feet, and 9 feet for wells GW -N48, GW -N51 and GW -N54, respectively. Map 2.04.7- <br />4 and Map 2.04.7-5, respectively shows the potentiometric surfaces and direction of flow of the <br />coal zone at both the lowest level (winter conditions, no irrigation flow) and highest level <br />(summer conditions with full irrigation). The gradient of the potentiometric surface varies from <br />about 0.029 ft/ft to about 0.047 ft/ft during the seasonal low levels and 0.033 ft/ft and 0.051 ft/ft <br />during seasonal high levels. The area directly north of the old Peabody highwall has a low <br />seasonal gradient of 0.028 ft/ft and a gradient during the irrigation season of 0.079 ft/ft. <br />Underburden Water Levels Two (GW -N47 and GW -N50) of the three under burden zone <br />monitoring wells that have been monitored since October 2008 clearly show the seasonal effects <br />of surface irrigation (see Appendix 2.04.7-1 for hydrographs). Similar to the overburden at wells <br />GW -N55, GW -N53, indicate very little if any response to surface irrigation. GW -N53 produced <br />negligible water during drilling and the recovery from the first water level measurement to the <br />second measurement attests to the low rate of water level recovery at this location. As with the <br />GW -55 at this site, the GW -N53 monitoring well shows that the rates of vertical and lateral <br />recharge of the under burden is low. Map 2.04.7-6 and Map 2.04.7-7, respectively shows the <br />potentiometric surfaces and the direction of flow of the under burden zone at both the lowest <br />level (winter conditions, no irrigation flow) and highest level (summer conditions with full <br />irrigation). The amplitude of the seasonal fluctuation due to irrigation is about 7 feet and 23 feet <br />for wells GW -N47 and GW -N50, respectively. The gradient of the potentiometric surface varies <br />from about 0.029 ft/ft to about 0.046 ft/ft during the seasonal low levels and 0.0396 ft/ft and <br />0.055 ft/ft during seasonal high levels. The area directly north of the old Peabody highwall has a <br />low seasonal gradient of 0.024 ft/ft and a gradient during the irrigation season of 0.08 ft/ft. The <br />under burden zone at GW -N47 has an artesian head varying from 34 to 40 ft above the zone from <br />winter to summer. The under burden zone artesian head at GW -N50 varies from about 15 feet to <br />about 39 feet above the zone from winter to summer. <br />Backfill Water Levels The NHN permit area encompasses part of the area of the old Peabody <br />Nucla Mine, which ceased production in 1983. Overburden backfill material exists south of the <br />old Peabody high -wall. Four wells (GW -N10, GW -N26, GW -N27 and GW -N28) monitored <br />water levels in this backfill material through the end of 1987. All four of these wells were <br />abandoned and reclaimed in November of 2001. Map 2.04.7-1 shows these backfill monitor well <br />locations. The backfill is essentially dry with the exception of the area in the vicinity of GW -N27 <br />and GW -N10. At GW -N27 the back fill has approximately 6.4 feet of maximum saturation. At <br />GW -N10 the backfill is dry from time to time with maximum saturation of only slightly more <br />Section 2.04.7 Page 4 April 2016 (PR -01) <br />