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the alluvial aquifer irrespective of the general irrigation effects. There is a suggestion of chemical trends
<br />during periods of irrigation. Calcium and bicarbonate levels are decreasing slightly with time.
<br />The alluvial aquifer water exceeds the CWQCC agricultural standard for manganese. The water is
<br />acceptable for use as livestock drinking water. Measurable trace element concentrations in the alluvial
<br />aquifer include aluminum, boron, fluoride, lithium, manganese, nitrate, vanadium and zinc.
<br />Four wells (GW -N15, GW -N18, GW-N18P1 and GW -N21) monitored the overburden water quality in the
<br />New Horizon 2 mining area. The well locations are shown on Map 2.04.7-1A.
<br />The four overburden monitoring wells exhibited two water types during periods of irrigation. Well
<br />GW -N15 showed a magnesium sulfate type water and Wells GW -N18 and GW -N21 showed a calcium
<br />magnesium sulfate water type. During non -irrigation periods, none of the wells changed in water type.
<br />Measurable changes in TDS levels did occur when comparing irrigation versus non -irrigation periods. The
<br />TDS at well GW -N15 decreased, and the TDS at wells GW -N18 and CW -N21 increased during periods of
<br />no irrigation. The greatest change in TDS occured at well GW -N15 where there was a 1,662 mg/I drop in
<br />TDS during non -irrigation periods. Mean TDS levels for the three overburden wells (GW -N15, GW -N18
<br />and GW -N21) during periods of irrigation and no irrigation were 8,310 and 6,648 mg/1, 2,527 and 2,832
<br />mg/1, 3,154 and 3,450 mg/1, respectively.
<br />During periods of no irrigation, well GW -N15 showed a slight decrease in calcium and a decrease in
<br />magnesium and sulfate, with increases in sodium, bicarbonate and chloride. Well GW -N18 showed a slight
<br />decrease in magnesium, slight increases in sodium and bicarbonate and increases in calcium and sulfate.
<br />Well GW -N21 showed a slight decrease in calcium, a slight increase in bicarbonate, increases in
<br />magnesium, sodium and sulfate and a large increase in chloride.
<br />A range in pH values from 7.3 to 7.8 were measured at the four overburden wells. The mean pH values for
<br />wells GW -N15, GW -N18, GW-N18P1, and GW -N21 are 7.5, 7.61, 7.5 and 7.54, respectively.
<br />There appeared to be some seasonality to the overburden water chemistry at the New Horizon 2 mining area.
<br />In comparing spring versus fall chemistry, alkalinity, bicarbonate, chloride, potassium, sodium, sulfate and
<br />TDS levels tended to decrease in the fall. In comparing fall versus winter chemistry, alkalinity,
<br />bicarbonate, chloride, potassium and sodium levels increased and pH decreased in the winter. In comparing
<br />summer versus winter chemistry, alkalinity, bicarbonate, chloride and sodium levels increased and calcium
<br />levels decreased in the winter.
<br />In addition to chemical seasonality, there were some overburden chemical trends during the irrigation season
<br />with time. Well GW -N18 showed a decrease in calcium and an increase in sodium, bicarbonate, sulfate and
<br />TDS levels.
<br />Well GW -N18 water exceeded the CWQCC agricultural standards for fluoride and manganese and the water
<br />at Wells GW -N15 and GW -N21 exceeded the manganese standard. In comparison to livestock drinking
<br />water standards, well GW -N15 water exceeded the magnesium, sulfate and TDS standards and well
<br />GW -N18 water exceeded the fluoride standard. Well GW -N21 water was suitable for use as livestock
<br />drinking water and water at well GW -N 18P 1 was suitable for both agricultural and livestock use.
<br />Measurable trace element concentrations in the overburden aquifer included aluminum, arsenic, boron,
<br />cadmium, cobalt, fluoride, iron, lithium, manganese, nitrate, selenium, vanadium, silver and zinc. The
<br />highest concentrations of cadmium, nitrate, selenium and silver were measured in the overburden aquifer at
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