Mine Closure

by: Dr. A. Robertson and S. Shaw

This secition of EnviroMine was created with the objective of providing an introduction to typical mine closure philosophies, plan development processes and evaluation tools, as well as providing links to useful resources. An introduction to closure planning is provided on this page, which has been organised into the following sections:


Introduction


In recent decades, in response to both external public activisim and internal desires to improve their stewardship, mining companies and regulatory authorities have applied ever more stringent environmental protection measures and standards during mining operations and on closure. During the 80's and 90's, there was a global trend towards 'Designing for Closure', with environmental protection and closure measures being designed into existing mine operations, and being mandatory for opening new mines. As a result, closure planning has evolved so that the mine's closure is addressed as part of the operating decisions and practices. Through prior planning, and progressive planning and implementation of measures, costs and impacts can be minimized.

As we progress into the twentyfirst century, there is increasing awareness of the need to provide for 'sustainability' of ecological and social settings in which mines are developed, operated and closed. The 'six tenets for sustainability of mining' provide the foundation for sustainability planning at a mine site. This gives rise to the need to do more than 'Design for Closure', requiring that we also prepare 'Post Mining Sustainable Use Plans' for the mine site and affected area. This concept is described by Robertson et al., 1998 and Robertson and Shaw, 1999. It also requires that all stakeholders, including the succeeding custodian, be consulted in the preparation of mine development, operations, closure and post closure sustainable use plans.

An example of innovate post mining land use development is the redevelopment of an abandoned mine in Cornwall called the Eden Project.

In planning for closure, there are four key objectives that must be considered:

  1. protect public health and safety;
  2. alleviate or eliminate environmental damage;
  3. achieve a productive use of the land, or a return to its original condition or an acceptable alternative; and,
  4. to the extent achievable, provide for sustainability of social and economic benefits resulting from mine development and operations.

Impacts that change conditions affecting these objecties are often broadly discussed as the 'impacts' or the environmental impacts of a site or a closure plan. It is convenient to consider potential impacts in four groupings:

  1. Physical stability - buildings, structures, workings, pit slopes, underground openings etc. must be stable and not move so as to eliminate any hazard to the publich 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.
  2. 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.
  3. 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.
  4. Sustainable development - elements of mine development that contribute to (impact) the sustainability of social and economic benefit, post miing, should be maintained and transferred to succeeding custodians.

Clearly the assessment of these types of impacts and closure requirements must address components of the site as well as the region and must select measures and allocate resources to address the major issues of impact. In order to minimize the various impacts, risks and liabilities, it is necessary to anticipate, as early in the process as possible, potential future liabilities and risks, and to plan for their elimination or minimization. In many areas, much of the liability or risk is associated with the uncertainty of the requirements for closure and rehabilitation from the succeeding custodian (be it a government agency, community organization or corporate entity). Early identification of the succeeding custodian, and their involvement in the development of the closure plan enables the closure requirements to be established and agreed and considered in the closure plan development. This allows the mining company to determine, and provide for, the requirements of the succeeding custodians, gain their support for the closure plan and minimize the risks and liabilities that may derive from succeeding custodian rejection or objection to the closure measures at the time of mine closure.

Foward to Closure Plan Development Steps