4.12 Completion criteria

Completion criteria (also known as ‘success criteria’) are critical elements of the mine closure process. The mining company requires completion criteria in order to demonstrate that rehabilitation and other objectives have been met, close the mine and relinquish the mining lease.

Leading practice mine completion criteria go beyond physical and biological rehabilitation and closure aspects to include social and economic criteria, in order to establish sustainable outcomes in communities that may have been negatively affected by mine operations, mine closure, or both. Governments need reliable measures of rehabilitation success to ensure that sites are stable and sustainable and the community is not inheriting an ongoing liability. The public wants to know that the rehabilitation will be successful; that the site is non-polluting, not having impacts beyond the mine boundaries and being safe for humans and fauna; and that sustainable land use will result. Examples of leading practice approaches to closure planning and design are in the Mine closure handbook (DIIS 2016e).

While completion criteria are a key requirement for demonstrating rehabilitation success, meeting regulator and other stakeholder expectations for mine closure also requires criteria relating to other parameters. They might include criteria relating to water quality (for a range of water bodies and downstream creeks or rivers), contaminated land, visual indicators linked to aesthetics or belief systems (such as landforms not visually detracting from significant landmarks), the agricultural productivity of farmland, or geotechnical stability. The need for each criterion should be defined during risk assessments undertaken as part of life-of-mine closure planning.

Procedures for developing completion criteria are described in a number of documents, including the Mine closure, Mine rehabilitation and Biodiversity management handbooks in this series (DIIS 2016e, 2016g and 2016f). Other key references describing important aspects of the process include the IMCC mine closure toolkit, Planning for integrated mine closure (ICMM 2008) and the ANZMEC–MCA Strategic framework for mine closure (2000). In the simplest terms, a clear closure objective is needed, accompanied by auditable measurement criteria that can be used to establish that the objective has been achieved. The criteria, together with any associated targets and standards, must be clear and unambiguous, measurable using indicators and methods acceptable to regulators and other key stakeholders, and achievable.

Monitoring, auditing and research can play a key role in the development of completion criteria by demonstrating what impacts have occurred due to mining activities and the extent to which rehabilitation can replace (or is replacing) the values affected, as outlined in the agreed objectives. The results can be compared with stakeholder expectations, and the criteria, together with any associated targets or milestones, can be modified according to new information, subject to the agreement of stakeholders. A process for developing ecological criteria is described in Nichols (2006), where it is illustrated using a flowchart.

More recently, several Australian states have provided guidance on the development of completion criteria, such as Western Australia (DMP–EPA 2011) and Queensland (DEHP 2013). Both emphasise the importance of having clear objectives, using indicators to measure the development of rehabilitation, and closely linking completion criteria to both of them. They also provide examples of criteria.

When developing rehabilitation completion criteria and associated indicators, it is important to note that expectations are increasing. Simply using the area rehabilitated as a measure of performance is no longer considered sufficient. Several companies are now either using or developing more detailed measures (or metrics) of rehabilitation quality. They include measures of species richness and diversity (such as the numbers of native species in a defined area), as well as measures of cover and indicators of nutrient accumulation and cycling. In several instances, rehabilitation quality metrics (RQM) or similar measures that integrate several indicators are being used to assess rehabilitation performance, sometimes in conjunction with the assessment of offsets (for example, Temple et al. 2012; Rio Tinto 2008). These can be useful for determining whether objectives linked to no net loss of biodiversity are being met.

When assessing the establishment of native ecosystems, it is now generally required that monitoring include unmined reference sites. However, the reference sites might not necessarily be equivalent to pre-mined sites. Also, in most mines, even when leading practice rehabilitation methods are used, differences in pre- and post-mining soil structure and parameters exist. For that reason, it is not realistic to require that rehabilitation sites exactly match unmined sites in terms of key ecological parameters. Rather, the monitoring and comparison of rehabilitation with reference sites should give an indication of the replacement of ecological values over time and likely long-term sustainability.

For most projects, monitoring and auditing for performance evaluation have an important role in demonstrating that agreed completion criteria have been fulfilled and rehabilitation objectives have been met. Completion criteria can be derived from a number of sources, such as the conditions of an approval or an enabling agreement, agreements with individual landowners or regulatory requirements. The biophysical and social contexts of the mine also need to be taken into account. Often an operation commences with some broadly agreed closure objectives and associated completion criteria. They are generally easier to develop for mines that have a shorter life and clearly defined footprint than for longer lived mines with a more dynamic footprint. As the mine evolves, the objectives and criteria may be adjusted to reflect changing community expectations where they can be accommodated. The criteria may progressively become more refined and specific as mine closure approaches. Changes made to them, for whatever reason, may require altered monitoring procedures and auditing criteria.

Leading practice requires that, where practicable, mines implement progressive rehabilitation on an ongoing basis during mining operations. This can be linked to progressive sign-off through evaluations of rehabilitation performance and thereby increase stakeholders’ confidence in final rehabilitation outcomes and the mine closure process. Where progressive rehabilitation is carried out, definitions of rehabilitation success may need to be modified to cater for specific aspects of the rehabilitation process. For example, if progressively rehabilitated areas have poor connectivity with undisturbed areas, opportunities for the return of fauna and natural floral recolonisation may be more limited.

Completion criteria are usually developed for each ‘domain’; that is, for each different operational area of the mine, including open pits, WRDs, TSFs, infrastructure and so on. The criteria include consideration of social, cultural, economic and environmental values, all of which will need to be measured or assessed in some way to determine whether the target or milestone has been met. It is important that criteria are ‘SMART’ (Specific, Measurable, Attainable, Realistic, Timely).

Completion criteria for the closure and rehabilitation of open pits, WRDs and TSFs commonly include consideration of the following elements:

  • The final waste landforms are physically and chemically stable; they are safe for people and animals, blend with the surrounding landscape and are aesthetically and functionally acceptable.
  • Open pits, surface WRDs and TSFs maintain geotechnical stability.
  • Seepage to the receiving surface waters and groundwaters can be assimilated by the receiving environment and will not cause unacceptable harm.
  • Open pits remain regional ‘sinks’ unless a flooded and flow-through pit is the objective. If the pit is backfilled, the need to remain a sink will depend on the geochemical characteristics of the backfill material.
  • All drainage works remain functional and stable.
  • Erosion loss rates do not cause unacceptable environmental harm or geotechnical instability or threaten the sustainability of vegetation communities.
  • Downstream water quality will not be negatively affected by mine run-off and seepage.
  • Stream flows are not permanently reduced in the post-mining landscape (such as by catchment diversions).
  • Final void water quality matches the post-mining land-use requirements and community expectations.
  • Dust generation does not cause unacceptable amenity or health impacts or unacceptable harm to the environment.
  • Soil nutrient banks are established and soil chemical and physical parameters are suitable for the intended post-mining vegetation.
  • Appropriate vegetation is established and sustainable and satisfies the agreed post-mining land use, which may be an agricultural system (cropping, grazing, or both) or a native ecosystem.
  • Native animals are recolonising rehabilitated native ecosystems in adequate numbers and diversity.

It is important to demonstrate that completion criteria can (and will) be met over an extended period. The design of the monitoring and research programs discussed above must take into account the long-term sustainability of rehabilitation and how it is measured and demonstrated.

Socioeconomic completion criteria are usually whole-operation matters. Community baseline studies enable relevant information on the population and economy to be gathered and appropriate completion criteria to be developed. Criteria are influenced by the population and skills mix of the local community and by business activity either at the mine site (such as the adaptive reuse of buildings or interpretation of mining heritage through tours) or in neighbouring communities. An important part of mine closure is ongoing monitoring of the success of social and community development programs, for example through periodic household surveys seeking information on the health, education and economic status of the community.

It is important to monitor or audit the financial aspects relating to mine closure. The issue of funding for mine closure can pose challenges. While annual rehabilitation budgets are relatively easy to establish and monitor, the cost of closure to meet the completion criteria is more difficult to assess. However, those costs should still be modelled and should be reviewed at key milestones in an operation. Ideally, this should occur annually, but 3–5-year time frames may be adequate during expansion phases. Leading practice monitoring and auditing criteria ensure that internal funding is established to achieve both completion criteria and regulatory financial assurance requirements, verifying that sufficient funds are provided throughout the mine’s life to allow for both planned closure costs and contingency costs for unexpected developments. Costing and provisioning for mine closure are discussed in more detail in the Mine closure handbook in this series (DIIS 2016e).

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