O'Connor Mine Remediation Project

Located on an island in O’Connor Lake, east of the small community of Fort Resolution and approximately 190 km southeast of Yellowknife, the former O’Connor Lake Mine produced copper, lead, and zinc from both surface and underground workings before operations ceased in 1949. Following decades of abandonment, the remote fly-in site presented environmental and safety risks.

Challenge

Public Services and Procurement Canada, on behalf of Crown Indigenous Relations and Northern Affairs Canada, required remediation planning and construction support to remediate the former O’Connor Lake Mine, a federal contaminated site.

The site posed a range of potential hazards, including dilapidated structures, hazardous building materials, open mine workings, approximately 4,300 metric tonnes of waste rock, scattered debris, and contaminated soil. Remediation planning was further complicated by the site's remote location, restricted access, extreme weather, short field seasons, limited subcontractor availability, permafrost conditions, and a lack of suitable local borrow material. In addition, unsafe building conditions prevented access during initial assessments, creating uncertainty about ground conditions and the extent of mine workings beneath the structures.

O'Connor Mine site hazards and challenges

Solution

From 2021 to 2025, SLR delivered remediation planning, procurement, and construction-phase services. The project began with a review of historical site information to identify key data gaps, followed by two supplemental investigations to support human health and ecological risk assessments and remediation design. Additional studies included archaeological, drone, and bathymetric surveys.

SLR led the remediation planning process, including logistics and borrow material evaluations, remedial options analysis, Class A cost estimating, stakeholder engagement, engineering design, closure and reclamation planning, permitting, and tender document preparation. Drawing on extensive northern experience, the team developed practical solutions that accounted for the site's remote location, limited access, short construction seasons, weather constraints, and permafrost conditions.

Unsafe conditions within several site buildings prevented access during early investigations, requiring portions of the design to be completed after demolition activities began. To maintain project momentum, SLR provided rapid technical review of contractor-developed designs during construction, ensuring compliance with project specifications and supporting key project milestones.

Permafrost considerations informed the design of the mine shaft cap and groundwater monitoring wells. The borrow material assessment also confirmed limited onsite aggregate resources, prompting a design approach that minimized imported material requirements and reduced the high costs associated with transporting aggregate to the fly-in site.

Following contractor selection, SLR served as Public Services and Procurement Canada's onsite construction representative and provided contract administration services throughout remediation.

Impact

SLR delivered end-to-end support from initial site investigations through remediation planning, tender preparation, and onsite construction representation for a remote federal contaminated site. The multidisciplinary approach addressed critical data gaps, northern logistics, permafrost conditions, and limited onsite material availability, enabling informed decision-making throughout the project. Throughout the project SLR also provided training and employment opportunities for members of the local Fort Resolution Metis Government.

By adapting designs to evolving site conditions and providing responsive technical support during construction, SLR helped keep remediation activities on track despite the challenges of a remote fly-in location. The project reduced environmental and safety risks associated with legacy mining infrastructure, contaminated materials, and open mine workings while supporting the site's long-term closure and reclamation objectives.