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N33. The average artesian head for the underburden aquifer is 40.0 feet. A downward vertical head is generally observed in the underburden but an upward (recharging) vertical head is exhibited at Monitor Well GW-N16. All of the underburden monitor wells at New Horizon 1 & 2 display seasonal variability to some degree. The seasonal water level fluctuations at the New Horizon 1 & 2 mining areas range from only a few tenths of a foot at Monitor Wells GW- N3and GW-N11 to nearly 11.0 feet atmonitorwell GW-N13. All ofthe underburden monitorwells exhibit steady-state water levels overtimewith the exception of Monitor Wells GW-N1, GW-N1 P1 and GW-N6. These wells have displayed a slight shallowing trend with time. There were no distinguishable effects from the mining operation at New Horizon 1 area or recharge from precipitation events on the underburden aquifer system. Spoil Water Levels. Four monitor wells (GW-N10, GW-N26, GW-N27 and GW-N28) were installed to monitorwater levels in the spoil aquiferatthe New Horizon 1 area. Map 2.04.7-1 shows the spoil monitorwell locations. Monthly water level data including hydrographs are contained in Peabody Appendix 7-1. The spoils aquifer is dry or nearly dry exceptforthearea inthe vicinity of GW-N27. Atthis location the spoilaquiferhasapproximately6.4feetofsaturation. ThiswellwasinstalledinAugustof1987. In general, this well has shown seasonal fluctuation in the water level to correspond with the irrigation ditch flow. Multiple Completion Well Water Levels. Five wells with multiple seam completions have been installed at the New Horizon 1 area (Map 2.04.7-1 ). Monitor Wells GW-N8 and GW-N9 were installed in the overburden and the Dakota coal aquifers northwest of the New Horizon 1. Monitor Wells GW-N23, GW-N24 and GW-N25 were located in what had been referred to as the scraper area in the southeastern portion of the permit area. Those monitor wells were completed in early June, 1986 in the overburden, Dakota coal and underburden aquifers. Water level information indicates that the scraper area monitorwells are dry. Water level information has been gathered for Monitor Wells GW-N8 and GW-N9 on a monthly basis since September, 1979. Monitor Well GW-N8 is located up gradientand adjacenttothe mine pit. As a result, a 13 footdrawdown in static water level occurred prior to 1983. Since mining ceased in late 1983, the static water level has • (REVISED 6/28/01) 2.4.7-5