Examination of methods for evaluating remining a mine waste site. Part I. Geostatistical characterization methodology

Comprehensive characterization of the distribution and metal content of mine wastes is a crucial component of any project which aims at selective remediation as a function of minimization of cost and risk. Knowledge of the existence of structures and horizons within the sediments is critical to remediation since metal concentrations can vary significantly both within and between groupings of wastes and sediments. The exploratory techniques for structural and statistical analyses of the wastes as presented herein were used to identify population domains between observed waste/sediment classes and by locality within waste/sediment classes. Analysis of Variance (ANOVA) of split spoon samples extracted from the wastes proved to be effective in identifying population domains within the various observed waste/sediment classes. Variography identified the nature and continuity of variability in metal concentrations. Metal concentrations in mine and mill waste may vary rapidly over distance. For this reason, exploratory variogram analysis was used to relate estimation variance to sampling grid design and orientation. Where the deposition of mine wastes is influenced by fluvial processes, gravity separation can take place across areas that are sometimes flooded. This process produces drift in metal concentrations and can complicate the characterization of water deposited or reworked waste/sediment sites. Contaminant levels in mine and mill wastes are controlled by forces that can be very local in nature. As a result, the covariance structure can be non-stationary over relatively short distances. A methodology is presented herein for checking covariance stationarity.