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7 <br />difference (RPD) of 47.6%, which is not within control limits. One of these values is above <br />and one below the WAD cyanide mean concentration of 240 µg/1. The total cyanide <br />reanalysis concentration was 190 µg/1; however, this result is invalid because of the <br />exceedence of EPA holding times. Specific conductance, sodium, copper and calcium <br />concentrations were all lower than they were in May, 1993. The pH was lower and the iron <br />concentration higher than during the May, 1993 sampling. <br />Lower Tailings Impoundment. Both total and WAD cyanide concentrations in the lower <br />tailings impoundment were approximately twice those in the upper tailings impoundment in <br />the October 1993 sampling. Measured total cyanide concentrations were 58CI and 310 µg/l, <br />which results in a RPD of 60.7%, which is not within control levels for duplicate analysis <br />(allowable levels = ±20%RPD). As with the upper tailings impoundment samples for total <br />cyanide, Core Laboratories reran the samples but did so after the 14-day holding time had <br />been exceeded. Reanalysis of both the upper and lower tailings impoundment total cyanide <br />samples resulted in measured concentrations below those for WAD cyanide, beat as discussed ~ <br />above, the reanalyses are invalid because they were conducted after the 14-day holding time. <br />Unlike in the upper tailings impoundment, specific conductance, sodium, copper and calcium <br />concentrations were all higher than they were in May, 1993. As with the upper tailings <br />impoundment, however, the pH was slightly lower and the iron concentration higher than <br />during the May, 1993 sampling. <br />Collection Impoundment. Laboratory duplicate analysis of the collection impoundment <br />samples for total cyanide were within control levels (1050 and 1114 µg/1 = ±8% RPD), as <br />were lab duplicate analyses of WAD cyanide samples (620 and 720 µg/1 = ±15% RPD). <br />Therefore, no reanalysis of collection impoundment samples for cyanide was necessary. <br />Total cyanide concentrations were significantly higher than WAD cyanide concentrations in <br />collection impoundment samples, and both concentrations were slightly lower than those <br />measured in May, 1993. The collection impoundment again had the highest measured total <br />and WAD cyanide concentrations of the process point locations. Copper concentrations <br />were approximately half of those measured in May, 1993 and were the lowest measured <br />during the third-party samphng period. <br />3.1.3 Groundwater Samples <br />Groundwater Wells. Both total and WAD cyanide concentrations were again below <br />detection (at 20 µg/1) in all groundwater samples, although the total cyanide determination <br />on sample M-9 was conducted two days beyond the 14-day holding time (see letter, <br />Appendix E). Metals concentrations will be discussed below. <br />M_9. M-9 again had the highest calcium and sodium concentrations of the three <br />groundwater samples. Detection limits for copper, iron, and zinc were lower than those in <br />May, 1993, and concentrations of these three metals were consequently all at or above <br />RCG/Hagler, Bailly, lac <br />