Cover System Design for PAG Mine Rock

Located near Wells, British Columbia, the Bonanza Ledge gold mine (which ceased operations in July 2022) has made a positive impact on the local community and economy. In collaboration with Osisko Development, Okane developed an Issued For Permitting design for the closure of the mine’s open pit. This design is submitted for approval to both the Ministry of Energy, Mines, and Low Carbon Innovation (EMLI) and the Ministry of Environment and Climate Strategy (ENV) under a joint permit amendment.

Our team of experts applied advanced geochemical and geotechnical knowledge to ensure cover system performance and minimize net percolation into the underlying potential acid-generating (PAG) mine rock. This involved comprehensive studies, including numerical modelling of seepage and oxygen ingress, slope stability analysis, and geochemical modelling. These findings informed the design, effectively addressing identified high risks during the failure modes and effects analysis.

The cover system design enables the effective closure of the backfilled open pit and demonstrates a commitment to responsible site reclamation by mitigating potential acid and metalliferous drainage. The design has been approved by regulators as part of the permitting process, and with an Issued For Construction status granted, the execution phase of the project has commenced.