Seabridge Gold KSM court review: tailings, access works and risks for mine planners
Reviewed by Tom Sullivan

First reported on MINING.com
30 Second Briefing
British Columbia’s Supreme Court has ordered the Environmental Assessment Office to reopen its “substantial start” decision for Seabridge Gold’s C$8.8 billion KSM project, giving the Tsetsaut Skii km Lax Ha Nation 90 days to file submissions over planned processing and tailings facilities in Treaty Creek Valley. The First Nation warns the tailings pond could reach about 52 storeys deep on its exclusive traditional territory, while Seabridge points to a 17-km access road, power foundations and extensive early works underpinning the original ruling. The decision threatens the validity of KSM’s 2014 environmental certificate, despite C$1.2 billion already spent on one of the world’s largest undeveloped gold-copper deposits.
Technical Brief
- KSM’s substantial start status hinges on early works: 17 km access road, power foundations, camps, mine roads and fish habitat compensation.
- Justice Emily Burke ruled BC had updated its assessment of Tsetsaut Skii km Lax Ha claims around Treaty Creek but failed to integrate that into the substantial-start process.
- The Environmental Assessment Office must now reopen the determination and allow 90 days for written submissions from Tsetsaut Skii km Lax Ha.
- KSM remains unbuilt 12 years after securing provincial and federal approvals, despite extensive site preparation.
- A separate petition by SkeenaWild Conservation Trust was dismissed, narrowing the current legal challenge to Indigenous consultation.
- KSM’s proven and probable reserves total 2.29 billion tonnes at 0.64 g/t Au and 0.14% Cu, plus 160 Moz Ag.
- Seabridge reports C$1.2 billion already invested, including about C$208 million on permanent works since January 2024.
- A parallel dispute with Tudor Gold over a 12.5 km Mitchell Treaty Tunnel segment is delaying related permit amendments, adding further schedule risk.
Our Take
In our database, KSM is one of the few copper-gold projects with both very low grades (0.64 g/t Au, 0.14% Cu) and mega-project capex in Canada, which typically means any permitting delay materially erodes its competitiveness against brownfield expansions like Highland Valley Copper referenced in the 4 June 2026 piece.
Seabridge’s parallel push on the Iskut (Snip North) copper-gold resource in the Golden Triangle (15 April 2026 article) suggests the company is already hedging KSM’s permitting and legal uncertainty by building an alternative project pipeline in the same regional infrastructure corridor.
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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