Mt Milligan expansion approval to 2035: design and risk notes for mine engineers
Reviewed by Joe Ashwell
First reported on International Mining – News
30 Second Briefing
British Columbia’s Environmental Assessment Office has approved an amendment to Centerra Gold’s Mt Milligan copper-gold mine certificate, allowing increased production and extending operations near Fort St James to 2035. The decision by the Chief Executive Assessment Officer follows a detailed review of the EAO’s assessment report and associated conditions. Longer mine life and higher throughput will drive updates to waste rock and tailings management plans, water balance and discharge controls, and closure design for the open-pit operation.
Technical Brief
- Amendment modifies Mt Milligan’s existing environmental assessment certificate rather than issuing a new approval.
- Decision was taken by the EAO’s Chief Executive Assessment Officer, not a political appointee.
- EAO relied on a formal assessment report with project-specific conditions attached to the amended certificate.
- Conditions are expected to tighten operational controls on waste rock placement and tailings facility operation.
- Water balance modelling and discharge criteria become binding compliance points under the amended certificate conditions.
- Closure and reclamation concepts now need re-optimising to reflect the longer open-pit operating horizon.
Our Take
Extending Mt Milligan’s copper-gold operation in British Columbia to 2035 aligns with several other long-life copper items in our database, signalling that regulators in established jurisdictions are still prepared to back incremental brownfield expansions over greenfield builds.
The related piece noting an 11% throughput uplift at Mount Milligan suggests Centerra Gold is prioritising debottlenecking and mill efficiency, which typically lowers unit costs and can improve competitiveness against other North American copper-gold producers in our coverage.
Within the 250 copper- and gold-keyword pieces in our database, British Columbia projects like Mt Milligan and Gibraltar frequently feature in permitting and expansion stories, indicating the province remains a core jurisdiction for sustaining North American copper supply into the 2030s.
Prepared by collating external sources, AI-assisted tools, and Geomechanics.io’s proprietary mining database, then reviewed for technical accuracy & edited by our geotechnical team.
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