The historic Aberfoyle Mine at Rossarden, in northeastern Tasmania, operated from 1931 to 1982 producing 11,000 tonnes of tin and 3,500 tonnes of wolfram. Ore from the Aberfoyle Mine and the nearby Storey’s Creek Mine was processed on site and pyritic tailings were pumped into nine tailings dams, also located at the site. Metal sulfides within the tailings dams are a known contaminant and a source of acid and metalliferous drainage (AMD), with metal levels, including cadmium, measured above national guideline values. Rehabilitation works previously undertaken have included the emplacement of an earth capping over the tailings dams and vegetation trials. The vegetation trials have, however, shown limited success, with grass species growing with a patchy coverage to approximately 20 cm high. In this study, tailings samples (n = 75) were collected to a depth of 1.9 at the site. Tailings were logged and then subjected to a rigorous mineralogical and geochemical characterisation program. In addition, a new bioaccessibility test method developed by van Veen et al. (2016) was performed to determine the quantity of potentially harmful elements readily available for uptake by plants.

The findings from our study revealed that where the established soil cover is 300 mm thick, it is sufficiently retarding oxidation of sulfidic tailings, which are in general sparse at the site except in localised hotspots at depth (0.5–1 m). However, bioaccessibility experiments confirm that Cd, Cu and Zn are present at concentrations above national guidelines, and therefore pose a risk to larger vegetation (i.e., acacia and wattle) which have attempted to naturally colonise the site. To chemically and physically stabilise the site, our study recommends that a clay cap is introduced in parts of the site where the soil cap is < 300 mm or tailings are exposed. Following this, a soil cap should be emplaced. Native grasses and rushes should be seeded but this time care should be taken to ensure regular irrigation.