Mineral resources are finite ore bodies, and as a result all mine facilities will eventually close and the reputation of the mining industry dependent on the legacy in which it leaves (Sassoon, 1996).
Closure is the general term used to describe all the activities involved in decommissioning a mining operation and/or processing facility including reclamation, re-vegetation, removing equipment and structures, removal of chemicals and reagents, removal of hazardous wastes, remediation of any releases of hazardous substances to the environment, and post closure monitoring. Closure refers to decommissioning an operation in accordance with its reclamation plan (Adapted from Lowrie, 2002).
In planning for closure, there are four key objectives that must be considered (Adapted from Ontario Mining Act, August 2005):
- Protect public health and safety;
- Alleviate or eliminate environmental damage;
- Achieve a productive use of the land, or a return to its original condition or achieve the highest practicable level in the rehabilitation hierarchy;
- To the extent achievable, provide for sustainability of social and economic benefits resulting from mine development and operations;
Mining operators should identify post-mining land uses that are acceptable to the community, local government and any other relevant stakeholders.
Main potential impacts associated with mining operations can be categorized in four groupings (Adapted from Ontario Mining Act, August 2005):
- Physical stability – buildings, structures, workings, pit slopes, underground openings etc. must be stable and not move so as to eliminate any hazard to the public health and safety or material erosion to the terrestrial or aquatic receiving environment at concentrations that are harmful. Engineered structures must not deteriorate and fail.
- Geochemical stability – minerals, metals and ‘other’ contaminants must be stable, that is, must not leach and/or migrate into the receiving environment at concentrations that are harmful. Weathering oxidation and leaching processes must not transport contaminants, in excessive concentrations, into the environment. Surface waters and groundwater must be protected against adverse environmental impacts resulting from mining and processing activities.
- Land use – the closed mine site should be rehabilitated to pre-mining conditions or conditions that are compatible with the surrounding lands or achieves an agreed alternative productive land use. Generally the former requires the land to be aesthetically similar to the surroundings and capable of supporting a self-sustaining ecosystem typical of the area.
- Sustainable development – elements of mine development that contribute to (impact) the sustainability of social and economic benefit, post mining, should be maintained and transferred to succeeding custodians. Mine closure may bring severe reduction in income and taxes and additional cost in terms of social and environmental mitigation initiatives.
Mine closure is an increasingly complex process, and given the concerns of all stakeholders regarding environmental, social, and economic impacts, best practice has long gone beyond technical solutions. Trilateral process of consultation and problem solving, involving mining companies, governments, and communities, is required for a mine to be closed successfully. In fact, to be fully effective, the process of planning for mine closure should start at the mine design stage (Adapted from Bond, 2002).
The cost of physical mine closure tends to be significantly lower if the mine operator is in charge of the closure and clean-up process, rather than government or environmental funds. This is primarily due to the operator’s familiarity with the mine site and the lower incremental cost of using on-site equipment and staff. Initial cost estimates should be prepared early in the mine’s life and should be updated systematically on a regular basis (Adapted from The World Bank Group, 2002).
Closure plans should be re-evaluated as the mine site development progresses since the initial plans are based on projected conditions which are expected to change in response to additional ore discoveries, changing conditions of product and mining economics, advances in technology and new regulatory requirements. Once the initial plan has been developed and is accepted, periodic, iterative re-assessments and revisions should be completed to ensure that the plan remains current, relevant and optimized. Reclamation commonly is planned before mining begins, allowing the mine to be developed in a manner that facilitates final reclamation. Additionally, reclamation plans must be integrated into the mine planning process (Adapted from Robertson and Shaw, 1998 and 1999).
Good mine closure planning should begin at the feasibility stage and contain at least the following six elements:
- Clarity about time lines and costs;
- Specifics about the expected final landform and surface rehabilitation, including removal of plant and equipment and stabilization and detoxification of dumps and impoundments;
- Risk assessment to help set priorities for preparatory work;
- Cost-benefit analysis of different options as the plan is being prepared, reviewed, and updated;
- A management plan for how closure will be implemented;
- Proposals for post-closure monitoring arrangements (who monitors, for how long, who pays, who enforces compliance with environmental requirements);
An initial mine closure plan can influence key technology and waste disposal choices before mining commences and thereby enable rehabilitation to be built into operational activities at a lower cost over the overall mine life. Also, considering closure early can result in a plan that places decisions regarding the size and location of townships and other social infrastructure in a time frame that goes beyond the life of the mine (Adapted from The World Bank Group, 2002).
Consistent deployment of sustainable practices and the use of progressive rehabilitation are critical elements for successful mine closure and rehabilitation.
Do you know any interesting post-mining land uses? Are there any potential synergies with other industries within your community?
Follow me on twitter @rcrdossantos
Sassoon, M., “Closure or Abandonment”, Mining Magazine, (August, 1996).
Ontario Mining Act Fact Sheet. August 2005. Last accessed on 07/10/2016 at http://www.canaryinstitute.ca/publications/Ontario_Closure_Brochure.pdf
Robertson, A. and Shaw, S., “Mine Closure”, InfoMine E-book, (2002). Last accessed on 07/10/2016 at http://www.infomine.com/library/publications/docs/e-book%2002%20mine%20closure.pdf
Lawrie, R. L.., “Mining Reference Handbook”, Society for Mining, Metallurgy, and Exploration, Inc, Denver, CO – US (2002).
The World Bank Group’s Mining Department, “It’s Not Over When It’s Over: Mine Closure Around the World”, The Energy and Mining Sector Board, World Bank and the International Finance Corporation. (2002). Last accessed on 07/10/2016 at http://siteresources.worldbank.org/INTOGMC/Resources/notoverwhenover.pdf
Bond, J., “Foreword at It’s Not Over When It’s Over: Mine Closure Around the World”, Mining Department, World Bank Group, Washington D.C. (June, 2002).