Close-out concepts for the Elliot Lake uranium mining operations

In the Elliot Lake area, approximately 100 million tonnes of tailings have been generated and deposited in ten separate management areas covering a total of 460 hectares. With continued placement of tailings into land-based management areas, the ultimate combined area covered with tailings would be in the order of 1500 to 2000 hectares. The principal environmental concerns associated with the land-based management areas in the long term (after mining has ceased), as seen by the Canadian regulatory authorities, are the potential of acid generation from pyrite oxidation, and the release and migration of radionuclides into air and water. The development of close-out criteria and concepts, therefore, has focussed on addressing these concerns. A position paper was issued for comment by the Canadian Atomic Energy Control Board on long-term aspects of uranium tailings management. In response, three of the uranium companies, Rio Algom Limited, Denison Mines Limited, and Eldorado Nuclear Limited, have countered with their own position and supported it with the extensive research on close-out procedures that has been carried out on their properties. The companies' position is that regulations should allow for site specific solutions and that institutional control is a valid long-term control option. As radiological loadings to air and water in the long term will be less than during operations, the only long-term concern in Elliot Lake is pyrite oxidation. Research has indicated that pyrite oxidation can be controlled in the upper zone of tailings. A summary of options available to control pyrite oxidation in this upper zone, including vegetation, limestone addition, pyrite removal, and physical cover is presented as well as preliminary cost estimates of each alternative. (author)