Environmental remediation of soils with heterogenous radioactive contamination in Canada. Characterization and verification methods

The distribution of contaminants in soil varies from site to site depending on the transport processes that have occurred. Natural transport processes tend produce a continuous or homogeneous distribution. Human activities, such as earth moving, often result in a discontinuous or heterogeneous distribution presenting special problems for characterization and cleanup. The volume of suspect soil can be orders of magnitude larger than the volume of the discrete particles and pockets of contaminated soil that are present. It is desirable to characterize soil with discontinuous contamination in sufficient detail to allow cleanup of only the contaminated material and to determine with a reasonable certainty, that the material remaining following the cleanup does not require any further action. In Canada, the Low-Level Radioactive Waste Management Office (LLRWMO) manages historic radioactive wastes that are a federal responsibility. The LLRWMO has developed and refined methods to characterize and verify the success of cleanups of soil with heterogenous uranium mineral and radium contamination. A combination of surface and sub-surface measurements are collected and statistically analyzed to determine the cleanup limits. The LLRWMO has been successful in cleaning up industrial and residential properties affected by heterogeneous contamination. Tens of thousands of cubic metres of uncontaminated soil, from 45 hectares of industrial land in Fort McMurray, Alberta and hundreds of private residential properties in Scarborough, Ontario have been freed Tom further actions or restrictions. This paper presents the methods the LLRWMO has developed and used for characterizing soil with heterogenous uranium ore and radium contamination, and for verifying the success of environmental cleanups. Examples from LLRWMO projects are described. (author)