A ground-breaking new report by researchers including lead author Dr Renee Young, from the ARC Centre for Mine Site Restoration in Curtin University’s School of Molecular and Life Sciences in Australia, has provided new guidelines for successful mine site rehabilitation.

Image ©Dr Renee Young

The report, A framework for developing mine-site completion criteria in Western Australia, aims to improve mining industry practice for mine-site rehabilitation and successfully transitioning land from mining to its next use such as for development, agriculture or conservation.

Dr Young believes that the development of acceptable and achievable completion criteria is a necessary part of mine closure planning and fundamental to the successful transition of mined land to a future use. “Completion criteria have been defined in the mining context as agreed standards or levels of performance that indicate the success of rehabilitation and enable an operator to determine when its liability for an area will cease,” Dr Young said.

“Once achieved, they demonstrate to the mining company, regulators and other stakeholders that financial assurances and liabilities can be removed. Because of this important function it is imperative that completion criteria are effectively formulated to capture end-state goals, are accepted by all stakeholders and agreed by regulators and the proponent, are achievable, and can demonstrate this achievement through transparent and appropriate monitoring and documentation.”

According to the report, while considerable progress has been made in mine closure and rehabilitation planning in Western Australia, there remains a need to build capacity and understanding of how to best measure rehabilitation success and to set practical outcomes and measurable completion criteria, particularly with respect to environmental parameters.

“To address this gap, The Western Australian Biodiversity Science Institute (WABSI) has brought together leading experts, mining industry representatives and regulatory agencies to develop this report,” commented Dr Young.

Being the first project of its kind, completed in a relatively short timeframe, the scope of the project gave priority to guidance in the development of biological completion criteria.

The report authors accepted that addressing the broader range of completion criteria to a high level of detail was not possible with the time and resources available.

Dr Young agrees that the development of acceptable and achievable completion criteria is a necessary part of mine closure planning and fundamental to the successful transition of mined land to a future use. “Completion criteria have been defined in the mining context as agreed standards or levels of performance that indicate the success of rehabilitation and enable an operator to determine when its liability for an area will cease,” she said.

“Planning for mine closure should occur across the life of mine phases. As a key aspect of the mine closure planning process, the development of completion criteria should be considered from approval stage with activity continuing post closure.”

The report stated that throughout the life of mine there are opportunities for continual refinement to ensure completion criteria are robust and will best demonstrate that closure objectives have been met.

Monitoring and the associated use of completion criteria provides a mechanism for adaptive management and refined risk assessments. This is particularly important as continual improvement in rehabilitation techniques will occur over time and proponents should actively include this in their mine closure planning.

“The importance of completion criteria in the mining life-cycle are well recognised in numerous international and national handbooks and guidelines for mine closure planning,” said Dr Young.

“While there is no international or national standard for the development of completion criteria, more than 30 documents with guidance for the establishment of completion criteria – from jurisdictions across Australia (state and federal), Canada (provincial and federal), Peru, Chile, South Africa, Finland, Asia Pacific Economic Cooperation (APEC) and states within the United States of America – were identified.”

Decision processes used by survey respondents to determine post-mining land use. ©Dr Young

Many Western Australian industry examples of completion criteria incorporate the additional dimension of sequential mine closure phases, with some criteria specific to each phase. Typically, these phases segregate into planning/design, rehabilitation execution, and vegetation establishment and development. “This reflects the reality that the physical elements of rehabilitation landforms are necessarily planned and constructed before biological components can be established,” Dr Young said.

“The structure of a progressive assessment sequence aims to eliminate re-work at later stages of ecosystem development. For example, the topography and soil profile of a rehabilitated site is best confirmed immediately following earthworks, when machinery is on site and access remains open.

“By contrast, rectification of landforms after several years of ecosystem development is inefficient, and risks disturbing the established ecosystem,” argued Dr Young.

The report proposes that an additional consideration in relation to ecosystem development is that different criteria may be appropriate at different phases. Successful rehabilitation is likely to follow a successional pattern which can be used to inform appropriate timeframes to apply to individual criteria or performance indicator targets.

Dr Young sees risk management as an integral part of closure, decommissioning, rehabilitation and post-closure monitoring.

“When implemented effectively, it can enable an operation or project to identify risks and develop controls to achieve sustainable mine closure and relinquishment. Risks associated with the closure and post-closure phases in the mine life cycle cover both economic and non-economic consequences,” Dr Young said.

“These risks are long-term, and the expectations of the local community, government, landowners, neighbouring property owners and nongovernment organisations (NGOs) need to be considered.”

An important consideration during risk assessments that was identified by the report authors, is that potential changes to regulations may lead to unacceptable performance outcomes, due to increasing requirements at closure.

Mechanisms to reduce this risk include keeping up to date with new and changing regulatory requirements and ensuring rehabilitation operations are consistent with scientific best practice.

Given that vegetation composition is a typical attribute measured in rehabilitated areas, it is critical that aspects such as successional patterns are well understood.

“The primary mine closure roadblock is a lack in knowledge,” Dr Young commented.

“Many respondents welcomed the development of a framework for developing mine completion criteria. This would provide clarity about the level of detail required in closure criteria, and examples of what is acceptable to regulators.”

A concerned that was raised – primarily by regulators and independent consultants – was the risk posed by divestment, as industry proponents plan to sell off their assets as a site nears its closure date.

“In such cases, proponents may sell off their liability by on-selling sites to (smaller) companies without the internal culture and commitment to achieve a good environmental outcome,” said Dr Young.

“There are opportunities for companies to build assurances around this issue, to increase regulators’ trust and social licence to operate.”

*Article published in the October-December 2019 issue of The Asia Miner