Risk-informed design is conducive to sustainable closure design
A mining client ceased mining operations at the end of the 20th century but maintained its tailings storage facility for some time. Barr was retained in advance of an impending regulatory closure and decommissioning deadline to assist in the development and implementation of a plan for closure of the tailings facility. We developed alternatives for future closure plans in accordance with Canadian Dam Association guidance and international best practices and assisted in ongoing operations to lay the groundwork for closure in parallel with final design.
In 2021, Barr developed several conceptual design options for closing the facility and managing residual wastes, which included developing detailed material and water balances for the site, modeling closure scenarios, and presenting alternatives to the client and regulators. The option for sustainable closure and eventual relinquishment of the site that was selected involved drying, blending, and placing the residual waste materials in an isolating containment structure at the highest point of the TSF boundary. This approach is intended to provide long-term physical and chemical stability for the former TSF area, eliminate long-term active care, and support natural ecological systems.
Detailed engineering and design work began in 2023 when Barr designed an impervious cover and prepared a vegetation plan to manage erosion risks temporarily during the transitional and active closure phases. We investigated impacted soils and water on the larger mine site and within the TSF to define the extent of contamination, to assess borrow material suitability for reuse, and to perform engineering and design services for:
- Conceptual, feasibility, and detailed design stages
- Decommissioning and closure of TSF, including containment structures
- Geotechnical stability evaluation
- Landform design
- End-land-use planning
- Ecological investigation and vegetation selection
- Support with regulatory evaluation and submittals
- Groundwater management and remediation support
- Surface water runoff monitoring, management, and redirection off site
- Detailed construction sequencing planning
- Performance monitoring program development and execution
This site posed additional challenges, such as the need to maintain an operational pond and pumphouse within the bounds of the TSF during and following closure, which required detailed sequencing planning to maintain containment during all closure phases and avoid unnecessary environmental impact outside the TSF.
This robust approach to closure planning and design for the facility led to approvals from the regulator to proceed with closure and decommissioning activities for the facility. Detailed engineering and design have been completed and construction is anticipated to begin no later than 2026.