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• i <br />minerals. Thus, as the report stresses, the mineralogy, per se, indicates a potential for generation <br />of AMD. <br />Oxygen consumption. According to the report, the oxygen profile and oxygen consumption <br />measurements indicate that sulfides are not weathering because there is no appreciable change in <br />oxygen content between the shallow and deeper parts of the tailings profiles. Using the same <br />data, however, one could arrive at a separate conclusion. Namely, because there is no change in <br />oxygen content with depth, the tailings aze generally open to the atmosphere, and therefore <br />variations in oxygen consumption cannot be read because the tails aze constantly replenished <br />with atmospheric oxygen. Without further information, I could not favor either interpretation <br />over the other. <br />Petrographic analyses. The petrographic sections aze subject to similaz permissive <br />interpretations. (have seen polished sections of acid producing, pyritic tails, which were <br />exposed to the atmosphere for several yeazs to several tens of yeazs, exhibit a similar absence of <br />iron oxide weathering rinds azound the pyrite grains. Thus, I could not accept that the absence of <br />iron oxide rinding is evidence that the tails aze not exposed to the atmosphere. <br />Attenuation tests. The attenuation tests produced what I would consider to be wildly divergent <br />distribution coefficients, and as such, should be considered suspect. Provided the soils are <br />similaz in composition, if the K,'s are meaningful, they should be similaz. To me, it seems that <br />the test methods, usingjust about any organic or clayey soil, would tend to overestimate the <br />distribution coefficients, as well as the attenuation rates, above what would exist under natural <br />conditions. <br />The tests were conducted in a manner such that the contaminated waters came into contact with <br />higher volumes of rock than might be expected if the waters were percolating through static <br />sediments. Under these circumstances, even though the wa[er:rock ratio for the test was <br />measured to be 2:1 (by weight?), the effective water:rock ratio, that is, the ratio between the fluid <br />volume and the total surface azea of rock with which it may come in contact, is considerably <br />greater than what would be encountered in a simple drain-down orthrough-flowing system. <br />Paste pH tests. There is a minor question about whether the samples were rinsed prior to <br />analysis or not. (They should not have been rinsed.) The text does not specify how the paste pH <br />tests were run. <br />SUMMARY <br />Conditions that would most adversely affect the composition of the groundwater in this case are <br />those that control the generation, neutralization, attenuation and the release rate of contaminants <br />from tailings-derived waters. The condition for which we have the more reasonable data in this <br />