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shown by considering the coefficient of variation (ratio of standard deviation to <br />mean) for each parameter. Sixteen of the twenty-one parameters have a coefficient <br />of variation of less than 1. and three of [he parameters (As, Hg, and Se) have only <br />non-detectable values for all five samples. For these ttineteen parameters, the data <br />and statistics indicate substantial homogeneity. <br />The only two parameters for which. the coefficient Of variation exceeds unity are <br />total iron (c.v. = 1.26), and weak-acid dissociable cyanide (c. v. = 1.79). In both <br />cases, the relatively large coefficient of variation is due Io a single outlier <br />concentration, anti even in these cases, the coefficient of variation does not suggest <br />wide variability in pre-water chemistry. <br />The apparently lileh iron concentrations ate due to the low redox condition:c in the <br />tailings pore water. (The values cannot be due [o solubilization of iron undler acidic <br />conditions, because the pore water Itas a high pH.) If such water were [o be <br />exposed to air, the iron would precipitate as ferric oxyhydroxidc. <br />For WAD cyanide, ttu~ee of the five samples have concentrations lower than the <br />quantitation limit, and one has a measured concentration of orily 0.05 mg/1. Not <br />only are the WAD cyanide values low, but natural attenuation mechanisms are <br />expected to further decrease the W.~D cyanide values over time. <br />3. Table 5 compares the acid-base accounting data for the new samples to those <br />obtained in pre-operational testing and for the earlicr samples from the Lower <br />Impoundment. Table 5 demonstrates that the five new, deeper samples are entirely <br />comparable in tertns of acid-base accounts with the expectation from pre- <br />operational testing and with earlier testing of operational samples from dtis <br />impoundment. <br />Table 5 Acid-Base Accounting: Comparison of Pre-Operational and Lower <br />Impoundment Operational Data <br />PARAIvIETER PR)1 OPERATIONAL TAILINGS - <br /> OPERATIONAL LOWER IMPOUNDMENT <br /> TAILINGS October 1993 This Report <br /> Unrinsed Rinsed Unrinsed Rinsed Unrinsed Rinsed <br />Total Sulfur 2.32 2.79 1.15 1.10 1.68 1 84 <br />(%) <br />P}~ritic Sulfur 1.73 1.~6 0.86 0.49 1.44 1 59 <br />(`70) <br />Sulfate Sulfur 0.02 < 0.01 0.23 0.13 0.23 0 15 <br />(%) <br />AGP - St 53.1 87.2 35.9 34.8 52.6 5 .4 <br />(tCaCO3/kt) <br />Geochiinica, lnc. 4 26 Seyiember, l996 <br />