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• Data collected for the seven Nucla East piezometers are presented in Appendix G, and Table <br />6 gives a comparison of total dissolved solids (TDS) values for these piezome to rs versus <br />historical seasonal TDS values for all other Nucla East wells. Water quality data for <br />piezometers GV!-N35 and GW-N38 were not used in this comparison due to probable incomplete <br />well development or residual completion effects. <br />Pursuant to the March 17, 1989 CMLRD request for a one-time sampling of six of the new <br />(1987-1988) Nucla East piezometers, Peabody conducted water quality sampling at seven of <br />these piezometers on May 16-17, 1989. Water quality analyses for these vrells are <br />presented in Appendix G, along with comparative water quality statistical reports for <br />PJUCIa East aquifers, representing data both inclusive and non-inclusive of these seven <br />piezometers. A comparison of TDS values for these sites with other Nucla East wells is <br />presented in Table 6. Note that results for piezometers GW-N35 and GW-N38 are not <br />included in this table due to anomalously high values for total suspended solids. <br />Improper well development, both at the time of drilling and during water quality sampling, <br />along with possible residual completion effects, are thought to contribute to these <br />results (values of total suspended solids for both samples are more than double historic <br />• maximums for all other hydrologically comparable Nucla East wells). <br />Predicated on TDS values alone, piezometers GW-N31 and GW-N36 do not fall outside the <br />historic range for Nucla East overburden wells; however, comparison of other water quality <br />parameters indicates that these sites contain near-maximum concentrations of calcium, <br />potassium, magnesium, sodium and sulfate. <br />Dakota Coal piez ane ters GW-N29 and GW-N30 both fall near or outside the historic limits <br />fof chloride, potassium, sodium and sulfate, as well as for total disso l'ved solids (TDS), <br />Since total suspended solids (TSS) is low for both wells, it would appear that Dakota Coal <br />water is more highly variable than first assumed. Water at both wells is pH controlled <br />(5.03 at GW-N30 and 8.65 at CW-N29), and this factor could account for the variability <br />seen. <br />Only a single underburden piezometer, CW-1134, was found suitable for comparison with <br />historic data from Nucla East wells. The TDS value for this well falls within the <br />historic range, but sodium and bicarbonate are at or beyond the historic maximums for <br />those parameters for Nucla East untle rburden wells. <br />16 <br />