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Ground water in the underburden aquifer is under artesian conditions. Mean artesian heads in the <br />underburden aquifer range from 9.7 feet at Monitor Well GW-N 11 to 86.7 feet at Monitor Well GW- <br />N33. The average artesian head for the underburden aquifer is 40.0 feet <br />A downward vertical head is generally observed in the underburden but an upward (recharging) <br />vertical head is exhibited at Monitor Well GW-N16. All of the underburden monitor wells at New <br />Horizon 1 & 2 display seasonal variability to some degree. The seasonal water level fluctuations <br />at the New Horizon 1 & 2 mining areas range from only a few tenths of a foot at Monitor Wells GW- <br />N3and GW-N11 to nearly 11.0 feet at monitorwell GW-N13. All of the underburden monitorwells <br />exhibit steady-state water levels over time with the exception of Monitor Wells GW-N1, GW-N1 P1 <br />and GW-N6. These wells have displayed a slight shallowing trend with time. There were no <br />distinguishable effects from the mining operation at New Horizon 1 area or recharge from <br />precipitation events on the underburden aquifer system. <br />Spoil Water Levels. Four monitor wells (GW-N10, GW-N26, GW-N27 and GW-N28) were <br />installed to monitor water levels in the spoil aquifer at the New Horizon 1 area. Map 2.04.7-1 shows <br />the spoil monitor well locations, Monthly water level data including hydrographs are contained in <br />Peabody Appendix 7-1. <br />The spoils aquifer is dry or nearly dry except for the area in the vicinity of GW-N27. At this location <br />the spoil aquifer has approximately6.4 feetof saturation. This well was installed in August of 1987. <br />In general, this well has shown seasonal fluctuation in the water level to correspond with the <br />irrigation ditch flow. <br />Multiale Completion Well Water Levels. Five wells with multiple seam completions have been <br />installed at the New Horizon 1 area (Map 2.04.7-1 ). Monitor Wells GW-N8 and GW-N9 were <br />installed in the overburden and the Dakota coal aquifers northwest of the New Horizon 1. Monitor <br />Wells GW-N23, GW-N24 and GW-N25 were located in what had been referred to as the scraper <br />area in the southeastern portion of the permit area. Those monitor wells were completed in early <br />June, 1986 in the overburden, Dakota coal and underburden aquifers. Water level information <br />indicates that the scraper area monitor wells are dry. Water level information has been gathered <br />Revised 25 Jul 2002 2.04.7-5 <br />