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• aluminum and fluoride standards andWeIIGW-N20exceededthealuminumstandard. 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, nitrate,
<br />vanadium and zinc. The highestconcentrations ofaluminum, beryllium, boron, cobalt, fluoride, iron,
<br />lithium, manganese, nickel, nitrite and zinc were measured in the Dakota coal aquifer at the New
<br />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 aquiferwater quality in
<br />the New Horizon 2 mining area. The individual water quality analyses for the underburden aquifer
<br />wells in the New Horizon 2 mining area are presented in Peabody Appendix 7-4. The well locations
<br />are shown on Map 2.04.7-1.
<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 />irrigation and no irrigation were 2,592 and 2,632 mg/I, 1,059 and 1,079 ragA, and 1,204 mg/I and
<br />1,424 mg/I, respectively.
<br />During periods of no irrigation, Well GW-N13 showed slight increases in calcium, sulfate and
<br />chloride levels and slight decreases in magnesium and sodium levels; Well GW-N16 showed a
<br />decrease in magnesium and slight increases in sodium, bicarbonate and chloride levels; and Well
<br />GW-N19 showed a slight decrease in bicarbonate and increases in calcium, magnesium sodium,
<br />sulfate and chloride levels.
<br />The pH levels for the three underburden wells ranged from 7.0 to 9.1. Wells GW-N13, GW-N16 and
<br />GW-N19 were 7.28, 8.44 and 7.8, respectively.
<br />• Revised 18 Aug 2003 2.04.7-16
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