Arsenic Rich Waste Rock Disposal under Subaqueous and Anoxic Conditions

Abstract

Waste rock from the Cigar Lake project in Northern Saskatchewan, Canada, was evaluated for in-pit disposal under subaqueous and anoxic conditions. Column tests were conducted to assess arsenic release rates and sequential leach tests were conducted to form the basis of a mass balance approach for predicting arsenic concentrations over time. The arsenic concentration in pore water was a function of the pore water residence time and this suggests a new paradigm for interpretation of column tests under subaqueous conditions. The relatively ’steady state’ concentration of arsenic in pore water correlated well with the ’leachable’ fraction of arsenic in the solids. The relationship provided a tool to assess the risk of arsenic leaching in wastes using solids assays.