Giant Mine Oversight Board, 157 pp, 2017

The gold ore at the Giant Mine is collocated with arsenopyrite, an arsenic-bearing mineral. During ore processing, an arsenic trioxide (As₂O₃) dust mixture was generated, precipitated, and collected in baghouses. Beginning in 1951, the dust was stored on site in purpose-built vaults or in previously mined-out chambers (stopes). Over ~50 years of operation, 237,000 tonnes of As₂O₃ dust were generated and stored on site. The dust is, on average, ~60% As by weight. As₂O₃ is water soluble and therefore poses a risk to both people and the environment through transport to local water bodies. Long-term management of the dust is complicated by its large quantity, physical characteristics, and subsurface storage location. Integration of different technologies likely will be needed to provide effective treatment. Alternatives evaluated for this report included frozen block containment; vitrification with extraction, gold processing, and storage; cement stabilization and cement paste backfill with extraction and storage; and mineral precipitation with extraction and storage. Vitrification was the top-ranked dust stabilization and processing method identified in this report. https://www.gmob.ca/wp-content/uploads/2017/09/2017-08-Giant-Mine-State-of-Knowledge-Review_FINAL.pdf