Passive uranium remediation at Cluff Lake, Saskatchewan

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AREVA Resources Canada, headquartered in Saskatoon, SK, has been operating in Canada for over 50 years. For over 20 years AREVA and their predecessor companies operated the Cluff Lake uranium mine, located in northwestern Saskatchewan. Following closure of the mine in 2002, physical decommissioning activities at Cluff Lake were completed between 2004 and 2006. Large areas were re-sloped, while underground mines and the open-pit excavations were either backfilled or allowed to flood with groundwater and surface water. At present, the flooded pits contain elevated levels of metals including uranium (U), nickel (Ni) and arsenic (As),which are sourced from surrounding waste rock, bedrock, groundwater, and surface runoff. The objectives of this study are to: (1) identify the sources of aqueous trace metals which are in excess of provincial and federal guidelines, with a focus on U, Ni and As; (2) understand U cycling in two flooded mine pits of different ages at the Cluff Lake site, and to quantify the benefits of the passive remediation option and identify any long term uncertainties in the passive remediation approach; and (3) gather data to assess if the passive remediation approach could be enhanced through active intervention, such as biostimulation, to facilitate aqueous metalsequestration in the cold climatic region in which the mine site is located.