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Spoils Water Quality Data. An indication of the effect of mining on water quality is <br />• also provided by monitoring data from the Nucia Mine, where coal and overburden properties <br />are similar to those at Nucla_East.• Wells CW-N10, G~W-N26, G~W-N27_and.CW=N28_were drib <br />and cocppier•d ~^ s;,oi.Lmaterial at the Nucia Mine. We" 11 GW-N10, drilled in 1979, has a <br />satu~r ated thickness of less than 0.5 ft and therefore, no Hater sample could be collected. <br />Well GW-N27 however, drilled in August of 1987, was successfully sampled two months later, <br />and currently has a saturated thickness of about 6 ft. Wells CW-N26 and CW-N28, also <br />drilled in August/September 1987, do not contain enough water to collect a sample from. <br />A comparison of mean parameter concentrations for Nucia mining area overburden, Nucia East <br />mining area overburden, spoils, spoil spring and NPDES Pond 001 water quality is presented <br />in Table 17-14. Because only one sample analysis has been obtained from Spoil Well <br />CW-N27, spoils concentrations for the spoil well and Spoil Spring k1 were averaged and <br />considered representative of the spoil aquifer. Comparisons between the Nucia mining area <br />overburden aquifer water chemistry and spoil aquifer water chemistry indicate that <br />alkalinity, bicarbonate, and calcium are the only major ions with increased concentrations <br />in the spoil. Concentration increases ranged from 5 to 13 percent. Fluoride is the only <br />• trace element that increased in concentration in the spoil. The mean spoil TDS level is <br />11 percent lower than the mean TDS level for the Nucia overburden aquifer. A comparison <br />of the Nucia mining area overburden aquifer chemistry with the 001 pond chemistry showed <br />that only the trace elements boron and fluoride increased slightly. The mean TDS level <br />measured in the 001 pond is 33 percent lower. <br />A comparison of Nucia mining area overburden aquifer chemistry with Nucia East mining area <br />overburden aquifer chemistry shows that, of the major ions, magnesium, sodium and sulfate <br />levels are higher in the Nucia East mining area resulting in a mean TDS increase of 22 <br />percent. Fluoride and nitrate were the only other parameters showing increases in the <br />Nucia East mining area. The dramatic increase in nitrate concentratl ons Ss probably a <br />reflection of the greater intensity of irrigation land use immediately upgradient of the <br />monitoring wells. <br />Based on these data, no adverse changes in ground water chemistry due to mining in the <br />Nucia mining area have occurred. All spoil and spoil spring TDS levels are below those <br />measured in the overburden monitoring wells. Although the Nucia East overburden aquifer <br />• mean TDS level is higher than that at the Nucia mining area, the spoil material fs <br />expected to yield water with TDS levels that are no greater than those measured in the <br />overburden aquifer in the Nucia East mining area. <br />17-59 iRevised 04/11/88 <br />