Examination of methods for evaluating remining a mine waste site. Part II. Indicator kriging for selective remediation

Indicator kriging (IK) techniques provide a methodology for risk-based economic evaluation of alternative toxicity thresholds for selective remediation of soil contaminated by mine wastes. For any given hazardous waste site, the cost of remediation is primarily a function of the volume of material to be handled and the level of contamination. Selective mining or selective in situ leaching of mine wastes which have concentrations of marketable metals is presented herein as a prime example of this application of IK. The relationship between the level of cleanup, risk of error and the cost of cleanup is presented using mine wastes from a portion of the Bunker Hill Superfund site near Kellogg, Idaho, as an example. As the cleanup threshold increases, the metal grade increases while the volume of material to be handled decreases; within the IK model for each threshold, the volume of waste to be handled is a function of the degree of certainty desired. Based on the metal recovered, on the cost of handling and processing the tailings and on the production rate, an optimal selective remediation strategy exists which defines both the optimal production rate and the selectivity of remediation by mining the waste.