British Columbia Mine Reclamation Symposium

Protection of groundwater and surface water at a Bulk Explosives facility using calculated risk-based soil guidelines Bright, Doug; Flemming, Liza; Choi, Michael


The Kemess South Mine in northeast British Columbia operated between 1998 and 2011.The former Bulk Explosives Fabrication (BX) facility within the mine area produced ammonium nitrate based explosives to support mining operations. Production and handling caused significant accumulation of ammonia and nitrate (AN) in shallow soils surrounding the BX facility, and groundwater contamination of AN was identified beneath the site. Given that soil-based environmental quality guidelines/standards for ammonia and nitrate do not exist federally or provincially, site-specific remedial objectives (SSROs) were developed to allow appropriate remediation, in order to facilitate protection of groundwater for drinking water purposes, and to protect aquatic life in the adjacent Kemess Creek. The SSROs were calculated based on threshold leaching concentrations of ammonia and nitrate in soil below which soil concentrations would not cause future potential risks for humans drinking groundwater beneath the site, or for aquatic life in Kemess Creek. Calculations of SSROs were conservative considering attenuation biological and chemical attenuation will occur in the subsurface. Targeted areas of AN impacted soil were removed from the site, based on the SSROs, with post-remedial confirmatory sampling. Rather than bulk removal of soil impacted with AN (>1,200m³), a targeted removal of <400m³ was completed to meet acceptable site management objectives for groundwater and surface water protection.

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