A detailed risk assessment of a disused tailings pond was undertaken for a range of heavy metals using USEPA protocols. The assessment involved detailed air dispersion modelling using CALPUFF followed by a Source-Pathway-Receptor Model using the Dutch RISC HUMAN Software to predict human health risk.

The emission of particles from the tailings pond in the CALPUFF model was determined by the particle size distribution, geometric mean diameter and geometric standard deviation values based on emission factors obtained from an extensive literature study.

For the purposes of modelling the tailings pond MM5 data covering 120km x 120km was acquired consisting of 3-D hourly meteorological data for the full year. The MM5 data has a fine grid horizontal resolution of 12 km which was nested from an intermediate grid size of 36 km. The hourly 3-D meteorological parameters in the tiles included wind speed, wind direction, temperature, pressure and relative humidity. The computational modelling grid used to run CALMET and CALPUFF had a grid size of 50 km x 50 km.

The Quantitative Risk Assessment (QRA) was conducted on the MARI based on the human health risk associated with heavy metals from the tailings pond.