Ecosystem restoration in the Rabbit Lake drainage basin : retaining 226Ra and uranium within the waste management area

Abstract

This final report is the culmination of a 12-year study into the ecology of the Rabbit Lake Drainage Basin, and the behavior of the contaminants in it, primarily U and 226Ra. It incorporates data compiled from 20 years of monitoring water quality in the basin. The natural processes documented in this report effectively remove uranium, 226Ra and other contaminants from the water column, and sequester them in the lake sediments; with time, the sediments will be further isolated by the gradual terrestrialization of the lakes brought about by semiaquatic and submerged vegetation including the Characeae that are naturally present in the lakes and enhanced in Upper Link Lake. The ecological characteristics (semi-aquatic and aquatic vegetation identification, limnological and topographical features) of the drainage basin are analogous to those documented in geological studies on the genesis of fluviatile surficial uranium deposits. The existence of these mineral forming (minerotrophic) conditions in the Rabbit Lake drainage basin guarantees the effectiveness of the natural uranium removal process there. Knowledge gained from this study could provide the basis for an ecologically based decommissioning strategy integrated into institutional control. The natural processes identified in this report, could be further enhanced to increase the natural retention of contaminants and reduce the release of 226Ra. The promotion of terrestrialization and the creation of new Characeaen habitat could be implemented gradually during the life of the Rabbit Lake Operation. Such modifications would not only complete the restoration of an ecologically disturbed drainage basin, but transform it into a dynamic component of an environmentally sound, economical decommissioning strategy.