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What are the 6 steps of a mine completion criteria framework?

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Mine Rehabilitation & Closure / Mining & Resources

What are the 6 steps of a mine completion criteria framework?

A recent report commissioned and published by The Western Australian Biodiversity Science Institute (WABSI) offers a recommended outline for the development of acceptable criteria within a mine closure plan. This project developed a standalone framework and full project report, both of which can be accessed here.

What is mine completion?

Mining is a temporary land use, therefore operators have a responsibility to enable safe post-mining land use after mining activity has ended. Mine completion means that mined land has been closed and rehabilitated to an extent that land can safely transition to future use.

For the purpose of this guide, rehabilitation can be defined as:

“the return of disturbed land to a safe, stable, nonpolluting/ non-contaminating landform in an ecologically sustainable manner that is productive and/or self-sustaining, and is consistent with the agreed post-mining land use” (DMP & EPA 2015).

A mine completion framework includes agreed standards or levels of performance that indicate the success of rehabilitation and enable the operator to determine when its liability will cease.The Department of Mines, Industry Regulation and Safety (DMIRS) and the Environmental Protection Authority (EPA) determine that a Mine Closure Plan must consider:

  • Completion criteria that will be used to measure rehabilitation success
  • Completion criteria that will demonstrate the closure objectives have been met
  • Completion criteria developed for each domain which consider environmental values

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What are the 6 steps of a completion criteria framework?

The mine completion framework is made up of six key components:

  1. Selection of post-mining land uses (PMLUs)
  2. Aspects and closure objectives
  3. Selection of references
  4. Selection of attributes and risk-based prioritisation
  5. Development of completion criteria
  6. Monitoring

1. Identifying post-mining land uses (PMLUs)

In Western Australia, the most common outcome is to revert to pre-mining land use. However it may be that an alternative land use option is a beneficial outcome, so consideration should be given to all options, with a thorough examination of possibilities. PMLUs must be considered early in the planning stage, with PMLUs identified before approval of any new projects.

There are five primary land use classifications in Australia:

  • Conservation and natural environments
  • Production from relatively natural environments
  • Production from dryland agriculture and plantations
  • Intensive uses
  • Water

2. Identifying aspects and defining closure objectives

Once PMLUs have been selected, it’s necessary to identify relevant aspects (specific themes or elements) of a site, that must be addressed during closure. From here, closure objectives can be developed that ensure that the site is safe, stable, non-polluting and suitable to support the decided land use. Closure objectives are necessary to address issues specific to the mine site. Typical sites may have 10-15 aspects and related closure objectives, while more complex mine sites may require more.

Examples of aspects, and their corresponding closure objectives are included below:

  • Social – actively engaged and consulted key stakeholders that have agreement on the post-mining land use
  • Physical and surface stability – creation of safe and stable landform that minimises erosion and supports vegetation
  • Mine wastes and hazardous materials – achieve conditions where contaminants of the site are consistent
  • Water and drainage – surface drainage patters are reinstated and consistent with the regional drainage function
  • Soil fertility and drainage – suitable growth medium is in place to facilitate rehabilitation and agreed post-mining land use
  • Flora and vegetation – restored landscapes that are comparable to reference vegetation communities established through leading practice restoration techniques and within the constraints of the post-mining environment
  • Ecosystem function and sustainability – the rehabilitated ecosystem has function and resilience indicative of target ecosystem

3. Establishing a reference

In order to measure progress towards completion and rehabilitation criteria, operators need to select references against which they’ll be able to define completion criteria. The ongoing collection of data from these references is then used to evaluate progress towards satisfactory mine-site completion. It’s preferable to take reference data from an analogue site – this is an intact area that represents the desired closure outcomes.

This could include:

  • Ecosystems with the same vegetation type
  • Mining sites with similar characteristics
  • Areas with the same PMLU where the same completion criteria has been achieved

A mine closure plan needs to include a record of the processes used in the identification and selection of references. Examples of possible references are included below:

  • Baseline conditions – conditions present at the site prior to mine use
  • Analogue site – adjacent or near-by sites from which the necessary attributes to can be quantified to develop completion criteria for the sites agreed upon PMLUs
  • Leading-practice outcome – the conditions that most closely define the values desired for the site and that can be realistically achieved
  • Other alternative sites – example sites for alternate PMLUs, such as renewable energy farm or residential development
  • Conceptual model – synthesis of several data-based references including existing sites, field indicators and historical and predictive records

4. Identifying attributes

In the context of this guide, an attribute is defined as ‘a specific parameter that can be quantified, or task that can be verified to have been achieved’. Attributes should be measurable, with metrics that can be reviewed against the targets determined by the references collected in the previous step. Attributes are grouped in relation to aspects, however the same attribute can apply to multiple aspects. That means that a single attribute could offer evidence for several closure objectives, or conversely, several attributes may need to combine in order to meet the requirements of a single closure objective (determined in step 2).

While there are many attributes that can be considered, relevant attributes should be chosen based on a site’s specific use, location and requirements. Not all attributes are relevant for all sites. Given that some attributes pose a greater risk to the fulfillment of closure objectives than others, you will, however, need to prioritise attributes that are more critical than those that present less risk.

5. Establishing completion criteria

With your attributes selected, you can now set criteria that will represent targets for the successful fulfilment of closure objectives. These targets are determined by the reference value (step 3).
Targets must:

  • Be attainable for the site
  • Have a defined timeframe
  • Represent outcomes that align with the requirements of the determined PMLU (from step 1)

It’s not always possible to determine what these targets will be during early stages of closure planning, however the data you have available from reference sites may provide indicative levels. Given that different ecosystems may take longer to reinstate post-disturbance, completion criteria must be associated to a certain point in time – meaning, they must be time-bound. Understanding how a reference indicator is performing relative to this timeframe is important, as such, timelines with periodic targets for meeting completion criteria may need to be considered. If it appears that attributes are failing to maintain necessary levels of progress, corrective rehabilitation efforts may be necessary.

6. Monitoring

Monitoring of progress is linked directly to the completion criteria, with the main objective being to determine whether this criteria has been fulfilled to align with your closure plan.
There are three main categories to cover:

  • Data monitoring – collection, review and interpretation of data which will provide an indication of progress towards meeting completion criteria.
  • Auditing and evaluation – reviewing information against completion criteria to see whether it has been met, or is on track to meet desired outcomes. Auditing is time-bound in order to ensure that performance is on track to reach targets before the planned closure date.
  • Corrective action – depending on data obtained in the auditing process, it may be necessary to redefine completion criteria or review the existing rehabilitation program if significant risks are likely to prevent the completion of criteria before the planned closure date

Reviewing your rehabilitation practices
If results do indicate that a mine site risks not meeting completion criteria, it may be necessary to review why rehabilitation practices may be falling short. A review should consider:

  • Do the practices need to be amended, or new practices considered?
  • Is the existing completion criteria actually achievable?
  • Do both practices, and completion criteria need to be modified?

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