Remediation Strategies for the Long-term Management of Arsenic-trioxide Roaster Waste at the Giant Mine, Northwest Territories

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The Giant Mine, located in Yellowknife, Northwest Territories, was one of the largest gold mines in Canadaduring its 56 years of operation from 1948 until 2004. Ownership and responsibility for remediation of theGiant Mine site reverted to the Federal Government of Canada following the bankruptcy of the formeroperator, and the > $1B liability associated with this site is entirely borne by Canadian taxpayers. Disseminatedgold at the Giant Mine was associated with arsenopyrite (FeAsS)-bearing ore, which was roasted to liberate thegold from the sulfide matrix. This process generated an arsenic-trioxide roaster waste. Approximately 237,000tonnes of arsenic-trioxide roaster waste was deposited in mined-out stopes and purpose-built chambersunderground at the Giant Mine site. A critical challenge is the development and implementation of a viable,long-term solution for stabilizing and managing the arsenic-trioxide roaster waste. The overall goal of thisresearch program is to identify potential strategies for long-term stabilization and storage of arsenic-trioxideroaster waste. The proposed NSERC Alliance program, conducted in partnership with the Giant MineOversight Board, builds on existing research efforts focused on remediation of the Giant Mine to develop andevaluate strategies for managing the roaster waste. This Alliance program includes seven targeted researchprojects to address this challenge, including: 1) chemical and physical characterization of the arsenic-trioxideroaster waste; arsenic-trioxide roaster-waste stabilization through 2) precipitation of iron arsenates, 3) high-temperature sulfidation, 4) biogenic sulfidation, 5) vitrification, and 6) incorporation into cemented-paste backfill; and 7) application of non-traditional isotope systems for understanding the biogeochemical reaction mechanisms which contribute to transformation of arsenic-trioxide roaster waste. The results of this research program will contribute to the development of a permanent and safe strategy for remediation of arsenic-trioxide roaster waste, both at the Giant Mine site and other gold mines where arsenical wastes are generated.