Physical hazards of tailings dams.

Abstract

In his News Focus article “Wildlife deaths are a grim wake-up call in eastern Europe” (10 Mar., p. [1737][1]), Robert Koenig discusses the effects on wildlife of chemical contamination resulting from breaks in tailings dams. The Tisza River incident in Romania and Hungary illustrates one type of damage caused by uncontrolled release of wastes from mining and milling. Unstable tailings dams, which contain solids in addition to waste water, present physical as well as chemical hazards to humans and the environment. Such situations exist at many mining sites. Two examples at former uranium mining and processing sites are at Kowary, Poland, and Sillamae, Estonia. At Kowary, a tailings dam in a mountain valley formed a pond with a surface area of 1.3 hectares containing more than 250,000 metric tons of mining and processing wastes. The Jedlica River is eroding the foot of the dam. The river is the source of water for Kowary, which is downstream of the dam ([1][2]). At Sillamae, a tailings pond was constructed on the shore of the Gulf of Finland in the late 1940s within 50 meters of the shore. It now contains about 12 million tons of uranium and rare earth metal tailings mixed with oil shale ash. Wave erosion had been destabilizing the dam, so in 1997 a breakwater was constructed to protect it ([1][2]). Should the dam break, the solids would enter the sea immediately and then migrate to other coastal areas with the currents of the Gulf of Finland. It could take years for the insoluble fraction of the contaminants (uranium, thorium, various heavy metals, nitrates, etc.) to settle to the bottom and the soluble fraction to disperse over the Gulf. The potential for the toxic compounds entering the food chain has not been assessed, but could be a threat for decades. In addition, the pond is adjacent to the former site of a harbor. Redevelopment of the harbor is being considered for economic improvement of the region. Release of the tailings would make redevelopment of the harbor much more difficult, perhaps impossible. The European Union (E.U.), through its Phare program (which facilitates financial and technical cooperation between the E.U. and the countries of central and eastern Europe), has funded work leading to remediation of these two tailings ponds. For the pond at Sillamae, Norway, Sweden, Finland, Denmark, and Estonia have also contributed funds for remediation. The German government is remediating similar sites in eastern Germany. Both chemical and physical hazards of mining wastes need to be considered in avoiding future disasters. 1. [↵][3]1. C. K. Rofer, 2. T. Kaasik Turning a Problem into a Resource: Remediation and Waste Management at the Sillamae Site, Estonia (NATO Science Series, Kluwer, Dordrecht, Netherlands, 2000). [1]: /lookup/doi/10.1126/science.287.5459.1737 [2]: #ref-1 [3]: #xref-ref-1-1 View reference 1 in text