Integrating Decommissioning and Environmental Remediation into the Life-Cycle Management of Mining and Milling Sites

Modern mining takes a life-cycle approach that covers the temporal evolution of a site from exploration to the final end-state or re-use of a mining and milling site.

 

Figure 1: The life-cycle of a mining and milling facility

The picture the public has of mining today is still shaped by the past, when mining companies often exhibited a nonchalant attitude towards social and environmental impacts. Historically, this has its roots in a predominance of shareholder-value considerations, when the costs of environmental and social impacts were tacitly externalised. It has resulted in a large number of mining legacy sites world-wide, the remediation of which continues to require considerable (public) resources.

Mining and milling operations will permanently alter, to some degree at least, the site at which the operations take place but also their surroundings. A complete return to greenfield conditions will generally not be possible. Open cast mines, spoil heaps, and/or tailings management facilities will remain at the surface. Underground open mine workings will also remain. These features will eventually become mining and milling legacies with which the local population will have to live. A life-cycle approach to mine planning takes this into account and will also involve the local population in the planning and decision-finding processes for the future of such sites. A mining and milling operation should integrate into the local socio-economic context and add value to the host communities, if possible beyond its active life-time.

The classical engineering paradigm in residues management is to contain the alien material; in other words, to design for resistance. As a result, such structures, particularly above ground, have significant amounts of potential and chemical energy stored in them. According to the 2nd Law of Thermodynamics this energy will be dissipated over time. To counteract this process more energy has to be invested to maintain and repair mining and milling residues impoundments, possibly forever, requiring long-term stewardship.

When designing such impoundments it is, therefore, wise to minimise the amount of potential energy stored in them, for instance by going underground. Impoundments are often designed with only the operational requirements in mind, not considering their long-term fate. This will require extensive remediation works at the time of the closure of a mine. Such works should not be left to the end, but impoundments should be prepared for long-term care during the operational phase, as and when they are not needed anymore.

Figure 2: Integration of decommissioning and remediation

Decommissioning of above-ground and underground mine-infrastructure requires human and other resources, as well as knowledge. Once the mine is closed, both will become scarce rapidly. It is, therefore, wise to integrate decommissioning into the operational plan. Decommissioning and remediation work should be carried out as soon as infrastructure is deemed superfluous from the operations point of view. While it is appreciated that planning ahead for years, or decades in the case of mines exploiting large deposits, is difficult, it is wise to develop a mine-management plan that already includes a decommissioning plan. Buildings and other infrastructure can also be designed in ways to facilitate (partial) decommissioning.

Undertaking decommissioning and environmental remediation as part of planned life-cycle management activities will create a variety of synergies, including:

  • Financial synergies – will level out cost peaks and saves time
  • Site assessment synergies – data are collected only once
  • Risk management synergies – risks are understood over the whole life-cycle
  • Materials and residue management synergies – segregated wastes can re-utilised in the project and residual wastes management together
  • Occupational health & safety risk management synergies – many OHS risks are the same over the whole life-cycle
  • Records management synergies – the same records support the whole life-cycle management

Project management synergies – use the same resources and the same management systems

Figure 3 and 4: Financial synergies and savings from integrating decommissioning and remediation

In the past, the need for decommissioning and remediation often was not considered adequately, resulting in difficult and expensive to manage legacies. Modern project planning for mining and milling sites covers the full life-cycle right from the start. Integrated life-cycle management shows a move away from the ‘end-of-the-pipe‘ treatment paradigm. Life-cycle planning facilitates decommissioning and reduces the need for remediation. As a result, decommissioning and remediation costs can be fully internalised, and no unresolved problems are left to future generations. The end-state of a mining or milling site is fully understood and agreed upon from the beginning by all stakeholders.

 

W. Eberhard Falck
WEFalck Scientific Advisory Services and
European Mine Mentoring Centre (EMMC)
wefalck@wefalck.eu