GENERAL45636 - Laserfiche WebLink

Home Browse Search

' ~ zo CONCLUSIONS There is significant variation in the composition of Cresson overburden materials relative to content and reactivity of sulfides which can produce acid upon reaction with oxygen and water. Taken as a composite set, the data suggest that there is more net acid neutralization capacity than net acid generating capacity in the majority of the horizons sampled. The interpretation of the weathering history of the Cresson deposit, inferred from chemical and other analyses of the sampled materials appears to provide a reasonable explanation for the minerals present and their variation with depth. Increased acid generation appears to correlate well with increased total and pyritic sulfur in the samples. Increased acid generation promotes pH levels which may mobilize more trace metals than will be present at higher pH levels. Zinc appears to be the most significant trace metal subject to mobilization with some indication that copper and arsenic may be significantly mobilized in some samples. Detection limits in some of the test data are not low enough to satisfy comparisons with water quality limits of concern, particularly with respect to Cd. In cases where corroborative data on trace metals in selected samples were presented from analytical techniques with lower detection limits, the concentration of metals such as Cd were demonstrated to be generally below regulatory limits. Solutions exiting the humidity cells appear to be in various states of stable equilibrium at the end of the reported time periods but in some instances pH drift is still evident In the case of the humidity cell samples terminated after 28 weeks, there appears to be no clear justification for stopping the tests on the basis of the pH levels and trends alone. Terminating these tests does not appear to seriously compromise conclusions from the majority of the test cells. OMLR951DEH