Rehabilitation of Historic Mine Workings – A Phased Approach Category: Mining, Reclamation and Remediation
Sue Longo, Golder Associates Ltd, Canada – Sue_Longo@golder.com
Jonathon Taylor, Golder Associates Ltd, Canada – Jonathon_Taylor@golder.com
Darren Kennard, Golder Associates Ltd, Canada – Darren_Kennard@golder.com
John Scholte, Golder Associates Ltd, Canada – John_Scholte@golder.com
This course aims to walk participants through the process of investigating, mitigating, and rehabilitating hazards associated with abandoned, orphaned or historic mines. With these old mine workings the typical issues are around unmitigated hazards that can present themselves in two ways – gradually or as sudden event. These hazards can include open mine voids on surface, land subsidence, sinkholes, etc. The problems associated with these sites can be complex and difficult to manage from a technical, environmental and especially economic perspective. The mechanisms of surface impacts can be difficult to understand, making assessment of hazards and suitable mitigation or remediation efforts to limit risk complex. In some cases, there is considerable uncertainty around the accuracy/availability of the geometry of the mine workings and the geology. Challenges such as historical mine plans along with physical constraints like limited safe underground access, access for equipment and logistics, and proximity to local communities with the overarching umbrella of potential adverse environmental impacts are common
Over the last decade robust processes have been developed to cut through the complexity and develop solutions to manage or remove these hazards while optimizing costs and timelines.
Recent experience has shown that developing a holistic site wide investigation and rehabilitation approach can result in benefits to both the mineral rights holder, government, and/or the general public/landowners in the area of the hazards, resulting in cost savings and/or less intrusive rehabilitation methods.
The expected audience will include mine managers, environment and risk managers, and regulatory personnel that are dealing with issues related to land adversely impacted by historic mining. This can be in the context of active mining near historical mine workings or abandoned/orphaned mines.
The course will cover four main technical components:
- Session 1: Stability assessment of underground mine openings.
- Session 2: Remediation options for hazard mitigation
- Session 3: Backfill system development
- Session 4: Execution of stabilization options
Each session will have case studies presented that demonstrate the potential issues involved as well as the potential solutions.
Session 1: Stability assessment of voids, openings and workings
Stability assessments are generally completed using an iterative/phased approach. This session will discuss the phased approach to stability assessments:
- Data gathering and validation
- Desktop stability and data gap assessments
- Planning and execution of the physical investigation
- Stability assessments
- Identification of what mine openings require rehabilitation
Session 2: Options development for hazard mitigation and risk management
In order to optimize the mitigation and/or rehabilitation effort required to address hazards posed by historical mining activity, it is important to develop an overall rehabilitation strategy for a site including end land-uses. This can be achieved in a phased approach. It is also important to develop rehabilitation priorities as these may markedly impact cost and schedule impacts. This session will discuss:
- Potential rehabilitation option identification
- Order of magnitude costing and data gap/advantage/disadvantage assessment
- Detailed option design and assessment
- Prioritizing rehabilitation methods and developing a rehabilitation strategy
Session 3: Backfill system development
One of the remediation options available is backfilling voids to limit the progression of any failure and reduce or remove the potential for surface impacts. There are multiple types and methods for applying backfill in these situations. This session will discuss:
- Backfill type / method assessment
- Testing programs and recipe development
- Planning and sequencing strategy development
- QA/QC planning
Session 4: Execution of stabilization options
This is the actual site execution phase of the work. There are ways to phase the execution that can help manage costs and schedule. This session will discuss:
- Execution planning
- Labour, Materials, Equipment required
- Site examples
Handouts will be provided