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• of summer versus fall chemistry suggested that bicarbonate, chloride and pH levels increased and <br />magnesium levels decreased in the winter. <br />Chemical trends over time are also evident in the Dakota coal aquifer. Well GW-Ni4 showed a <br />decreasing trend in calcium levels during irrigation periods. Well GW-N17P1 showed a decreasing <br />trend in calcium, magnesium and bicarbonate levels and an increasing trend in sodium and chloride <br />levels during periods of irrigation. Irrigation period trends for well GW-N20 included decreasing <br />calcium, magnesium, sodium, sulfate and TDS levels and increasing chloride levels. <br />Trace elements in the Dakota coal wells were measured. Well GW-N14 water exceeded the <br />CWQCC agricultural standards for aluminum, iron, fluoride, manganese and pH; Well GW-N17P1 <br />water exceeded the pH standard; and Well GW-N20 water exceeded the iron, manganese and pH <br />standards. In comparison to livestock drinking water standards, Well GW-N14 water exceeded the <br />aluminum and fluoride standards and Well GW-N20 exceeded the aluminum standard. Measurable <br />trace element concentrations in the Dakota coal aquifer included aluminum, arsenic, beryllium, <br />boron, cadmium, chromium, cobalt, copper, fluoride, iron, lithium, manganese, nickel, nitrite, <br />• nitrate, vanadium and zinc. The highest concentrations of aluminum, beryllium, boron, cobalt, <br />fluoride, iron, lithium, manganese, nickel, nitrite and zincwere measured in the Dakota coal aquifer <br />at the New Horizon 2 mining area. Also, the lowest pH values were recorded in this aquifer. <br />Three wells (GW-N13, GW-N16 and GW-N19) monitored the underburden aquifer water quality <br />in the New Horizon 2 mining area. The individual water quality analyses for the underburden <br />aquifer wells in the New Horizon 2 mining area are presented in Attachment 2.04.7-7 (Peabody <br />Appendix 7-4). The well locations are shown on Map 2.04.7-1A. <br />The three underburden monitoring wells exhibited three water types during periods of irrigation. <br />Well GW-N13 showed calcium magnesium sulfate water type, Well GW-N13 showed a calcium <br />magnesium sulfate water type, Well GW-N16 showed a sodium bicarbonate water type, and Well <br />GW-N19 showed a sodium calcium magnesium bicarbonate sulfate water type. During the <br />non-irrigation periods the only water type change was at Well GW-N19 where the water type <br />became a sodium magnesium calcium sulfate bicarbonate. All three wells increased in TDS during <br />non-irrigation periods. The greatest increase in TDS, 220 mg/I, occured at Well GW-N19. Mean <br />• TDS levels for the three underburden wells (GW-N13, GW-N16 and GW-N19) during periods of <br />REVISED JULY 2006 2.04.7-21 <br />