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irrigation and no irrigation were 2,592 and 2,632 mg/I, 1,059 and 1,079 rag/I, 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 <br />and GW-N19 were 7.28, 8.44 and 7.8, respectively. <br />There was a limited amount of seasonal variability in the chemistry of the underburden aquifer. In <br />comparing spring versus fall chemistry, calcium, magnesium, sodium, potassium and sulfate levels <br />tended to increase in the fall. Fall versus winter chemistry suggested that only calcium levels <br />decreased in the winter. The only trend when comparing summer versus winter chemistry was an <br />increase in chloride in the winter. <br />Chemical trends over time were also evident in the underburden aquifer during irrigation periods. <br />Well GW-N13 showed an increasing trend in magnesium, sulfate and TDS levels; Well GW-N16 <br />showed an increasing trend in magnesium and bicarbonate levels; and Well GW-N19 showed a <br />decreasing trend in bicarbonate and an increasing trend in magnesium, sodium, sulfate and TDS <br />levels. <br />Trace elements measured were also measured in the underburden wells. Well GW-N13 water <br />exceeded the CWQCC agricultural standard for manganese and Well GW-N16 water exceeded <br />the pH standard. Well GW-N19 water met all of the standards. All three wells met the livestock <br />drinking water standards. Measurable trace element concentrations in the underburden aquifer <br />include aluminum, arsenic, boron, cadmium, copper, fluoride, iron, lithium, manganese, mercury, <br />nitrate, vanadium and zinc. The highest concentrations of arsenic, mercury and copper were <br />measured in the underburden aquifer at the New Horizon 2 mining area. <br />Revised 25 Jul 2002 2.[14.7-17 <br />