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the remaining eight monitorwells (GW-N14, GW-N17, GW-N17P1, GW-N20, GW N29, GW-N30, <br />GW-N42 and GW-N45) were located at New Horizon 2 (Map 2.04.7-1A). Water level data for Well <br />GW-N4 was collected since August, 1979 and collection of water level data for Wells GW-N14, GW- <br />N17, GW N17P1, and GW-N20 began in July 1986. GW-N4R, GW-N29 and GW-N30 were <br />installed in September, 1987 and collection of water level information began immediately after they <br />were completed and developed. Map 2.04.7-3 shows the Dakota coal potentiometric surface. <br />Monthly water level data including hydrographs for New Horizon 2 monitor well sites are contained <br />in Appendix D of Attachment 2.04.7-5. An additional well, GW-N37, was drilled in May, 1993 in the <br />north-east corner of the permit area. <br />Ground water in the Dakota coal is under artesian conditions. Mean artesian heads in the lower <br />Dakota coal range from 18 feet at Monitor Well GW-N 14 and 42 feet at Monitor Well GW-N29. The <br />average artesian head for the lower Dakota coal is 34 feet. Water levels in the Dakota coal display <br />seasonal variability that coincides with the irrigation season and operation of the ditch irrigation <br />system. The maximum seasonal water level fluctuation observed in Monitor Well GW-N4 is about <br />3.0 feet due to its location in the valley bottom. The New Horizon 2 wells display seasonal <br />variability from 2.8 feet at Monitor Well GW-N17P1 to 14.6 feet at Monitor Well GW-N20. <br />Shallowing occurs from April to September and there appears to be little lag between when the <br />irrigation season starts and the shallowing of the static water levels occurs. There are no <br />discernible water level responses to precipitation, nor can any affect from mining be observed at <br />any of the Dakota coal monitor wells at the New Horizon 1 mining area. <br />Underburden Water Levels. Fourteen monitor wells have been installed to monitor water levels <br />in the underburden aquifer system. Six of those monitor wells (GW-N1, GW N1 P1, GW-N3, GW- <br />N5, GW-N6 and GW-N11) were located in and proximate to the New Horizon 1 mine area. The <br />remaining six monitor wells (GW-N13, GW-N16, GW-N16P1, GW-N19, GW-N33, GW-N34, GW- <br />N43 and GW N46) were located proximate to the New Horizon 2 mining area. Maps 2.04.7-1A <br />and 2.04.7-4 show the underburden monitor well site locations and the potentiometric surface, <br />respectively. Monthly water level data including hydrographs for New Horizon 2 Mine sites may be <br />found in Appendix D of Attachment 2.04.7-5. In may, 1993, an additional well (GW-N36) was <br />installed in the northeast corner of the permit area. Ground water in the underburden aquifer is <br />under artesian conditions. Mean artesian heads in the underburden aquifer range from 9.7 feet at <br />Monitor Well GW-N11 to 86.7 feet at Monitor Well GW-N33. The average artesian head for the <br />2.04.7-10