Tailings dam seepage at the rehabilitated Mary Kathleen uranium mine, Australia

Lottermoser, B.G., and Ashley, P.M. (2005) Tailings dam seepage at the rehabilitated Mary Kathleen uranium mine, Australia. Journal of Geochemical Exploration, 85 (3). pp. 119-137.

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This study reports on the seepage of metals, metalloids and radionuclides from the Mary Kathleen uranium mill tailings repository. Since rehabilitation in the 1980s, the capped tailings have developed a stratified hydrochemistry, with acid (pH 3.7), saline, metal-rich (Fe, Mn, Ni, U ± As, Pb, Zn), oxygenated (1.05 mg L^−1 DO), radioactive waters in the upper tailings pile and near-neutral pH (pH 7.57), metal-poor, reduced (0.08 mg L−1 DO) waters at depth. Seepage (~0.5 L s^−1) of acid (pH 5.5), metal-rich (Fe, Mn ± Ni, U, Zn), radioactive (U-235, U-238, Ra-226, Ra-228, Ac-227) waters occurs from the base of the tailings dam retaining wall into the former evaporation pond and local drainage system. Oxygenation of the seepage waters causes the precipitation of Fe and coprecipitation and adsorption of other metals (U, Y), metalloids (As), rare earth elements (Ce, La) and radionuclides (U-235, U-238). By contrast, alkalis and alkaline–earth elements (Ca, K, Mg, Na, Sr), Mn, sulfate and to some degree metals (U, Zn, Ni), rare earth elements (Ce, La) and radionuclides (U-235, U-238, Ra-226, Ra-228) remain in solution until pH neutralisation and evaporation lead to their precipitation in efflorescences and sulfate-rich evaporative sediments. While the release of contaminant loads from the waste repository through seepage is insignificant (~5 kg of U per year), surface waters downstream of the tailings impoundment possess TDS, U and SO4 concentrations that exceed Australian water quality guideline values in livestock drinking water. Thus, in areas with a semi-arid climate, even insignificant load releases of contaminants from capped tailings repositories can still cause the deterioration of water quality in ephemeral creek systems.

Item ID: 4527
Item Type: Article (Research - C1)
ISSN: 0375-6742
Keywords: contamination, Australia; uranium, tailings, seepage
Date Deposited: 29 Sep 2009 23:07
FoR Codes: 04 EARTH SCIENCES > 0402 Geochemistry > 040202 Inorganic Geochemistry @ 100%
SEO Codes: 85 ENERGY > 8598 Environmentally Sustainable Energy Activities > 859899 Environmentally Sustainable Energy Activities not elsewhere classified @ 100%
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