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significance for ABA data were potentially toxic' materials having a net (ABP) of less than -5 ppt <br />CaCO3 (tons CaCO3 equivalent/iooo tons of material), or `acid toxic' if paste pH was less than <br />4.0 (Smith et al., 1974a and b). In general, if the net neutral (ABP) potential is largely positive, <br />then there is little to no potential for available acid to form (Sobek et al., 1987). <br />Paste pH is a common measure that presents the present condition of the sample at one point in <br />time. It reflects past conditions by measuring active acidity, but it is not predictive of future acid <br />or neutralization potential (Sobek et al., 1987). Determining paste pH can be helpful because <br />many heavy metals increase in solubility when pH is less than 4.0. Therefore, the paste pH <br />provides an indication of the solubility potential of potentially toxic metals. <br />The results of the forms of sulfur analysis are strictly interpretive. These results identify the <br />form of sulfur associated with the sampled material. Sulfur is a nonmetal and can react with <br />both inorganic and organic constituents. Its ability to react is based upon its `form'. For <br />instance, sulfur as sulfate (5042-) is very soluble, but `bound' and unable to react further (such as <br />for the formation of sulfuric acid). Residual sulfur is a form of sulfur bound to other organic <br />constituents. Since it is bound to `like' elements it is relatively unavailable for further reaction <br />(and creation of acid). Pyritic sulfur is a very unstable form of sulfur; therefore it is available for <br />further reaction and of potential concern due to its ability to form acid (Sobek et al., 1987). The <br />pyritic sulfur percent composition can be used in combination with ABA results to quantify the <br />acid generation/acid neutralization potential that is directly attributable to pyritic sulfur (vs the <br />total amount attributable to all forms of sulfur) (refer to Table 4). <br />The results of the water sample measurement of pH provides an indication of the buffering <br />capacity of the underground water managed by the mine. The pH measures from the permitted <br />portal discharge have ranged from 6.9 to 8, with an average of 7.3 (based on 1o quarters of <br />measurements). <br />81 Page