By Tess Macallan, Journalist, Mining Magazine
When mineral resources are depleted and the machinery switches off, the significant impact a mine site has on the environment and surrounding communities remains. In Australia, mine operators have a responsibility to act sustainably and deliver enduring value to the regions in which they operate, including developing plans for post-mining land use. Here, we explore the different approaches to post-mining land use and take a look at some of the current processes underway for when mining operations cease.
In Australia, mine operators must comply with regulations related to land rehabilitation and post-mining land use. Such regulations are implemented across federal, state and local government levels.
There is no one-size-fits-all approach to reshaping and reusing a site after mining, with plans involving anything from restoration or rehabilitation of the land, to repurposing the site for agriculture, conservation, recreation or urban development. The process for determining a course of action often entails site assessments, working with relevant stakeholders, and developing a land use plan.
Determining best practices
When it comes to post-mining land use, it is important to distinguish between rehabilitation and restoration. Restoration is the process of re-establishing the ecosystem structure and the function of the land to its state prior to mining, or replicating a similar ecosystem to what previously existed.
In contrast, rehabilitation covers processes that do not involve land being restored to its original or close-to-original ecosystem. Rehabilitated land may, however, progress to a restored ecosystem over time.
Most states and territories have their own guidelines and regulations for rehabilitation. This often involves a requirement for companies to lodge cash bonds, unconditional financial institution guarantees or non-refundable contributions to pooled funds before any mining begins. These funds are generally intended to cover the full third party costs of rehabilitating mine sites.
Beyond legal requirements, implementing rehabilitation best practice is crucial for operators to maintain their reputation and keep the support of communities and governments.
Mine rehabilitation is a long and often complex process. Approaches to rehabilitation vary depending on, or even within, a site, and must take into account relevant regulations and the considerations of various stakeholders.
Best practice rehabilitation starts at the outset of a mining project and continues through to mine closure and the lease is relinquished.
According to the Federal Government’s Leading Practice Sustainable Development Program for the Mining Industry mine rehabilitation handbook, rehabilitation comprises “the design and construction of landforms as well as the establishment of sustainable ecosystems or alternative vegetation, depending upon desired post-operational land use”.
The handbook outlines three key objectives that mine site rehabilitation should be designed to meet:
- The long-term stability and sustainability of the landforms, soils and hydrology of the site
- The partial or full repair of ecosystem capacity to provide habitats for biota and services for people
- The prevention of pollution of the surrounding environment
Ripe for rehabilitation
Fosterville Gold Mine
The Fosterville Gold Mine in Victoria is an example of how mine rehabilitation begins long before a mine ceases operation. Rehabilitation plans at Fosterville are intended to return sites to a similar vegetation function and structure as existed prior to mining. However, plans may change depending on the new landform at the closure of the mine. In this case, species selection will be required.
According to the Minerals Council of Australia’s (MCA) Mine Rehabilitation: rehabilitation, closure planning and regulation report, the Fosterville rehabilitation plan aims to return parts of native forest back to a self-sustaining native forest while increasing the number of indigenous species and connecting up biodiversity corridors where possible.
The rehabilitation practices at Fosterville are under frequent review. Since 1989, Goldfields Revegetation has provided rehabilitation services to the mine, including seed collection of local indigenous species, seed treatment and propagation, and planting and monitoring. Current rehabilitation also includes landscaping, topsoiling, ripping and mulching.
Coal & Allied alluvial land rehabilitation
Australian coal mining company Coal & Allied undertook an unprecedented trial to demonstrate how alluvial land used for mining can be rehabilitated to match the crop production levels of nearby farms.
As a condition of Coal & Allied receiving approval to mine 165ha of farming land in the Upper Hunter Valley Region, the company was required to reinstate 65ha of the land to Class 1 and 2 lands suitable for irrigated agriculture.
In order to demonstrate that the land had been restored as required, Coal & Allied was required to produce Lucerne hay with a productivity yield equivalent to the average crop productivity yields for the Upper Hunter Region for three consecutive years.
The plans for rehabilitation commenced in 1990 – before mining activities had even begun. Mapping of the soil profile was carried out and topsoil and subsoil were stockpiled separately. By 2003, backfilling of the eastern section of the land was complete and rehabilitation commenced. The stockpiled subsoil and topsoil were replaced to a depth of 1.5m to accommodate crops with deep roots like Lucerne.
Following three years of consecutive production, hay yields were above the district average. The land was tendered out for commercial cropping in 2013 and is currently being used to grow crops such as Lucerne and triticale (a hybrid of wheat and rye used in cereals).
The Coal & Allied process demonstrated the potential for rehabilitation of agricultural land. The area will continue to be farmed and monitored and a valuable asset will remain even after mining operations cease.
Repurposing resources
It is sometimes extremely difficult – or impossible – to deliver productive agricultural landscapes or vegetation similar to original ecosystems post-mining. In this case, different rehabilitation or repurposing objectives are required. Australia’s mine operators must consult with regulators to determine appropriate post-mining land uses.
The process of repurposing former mines for a diversity of economic, social and environmental purposes, such as tourism and recreation, is commonplace.
Lake Kepwari
The repurposing of part of a coal mine in Collie, Western Australia, is an example of how mining assets can be repurposed to a variety of uses that support a region’s economic transition following a long period of reliance on the mining industry.
The Collie deep coal mine pit was part of a larger coal mine site, which produced black coal for Western Australian domestic and industrial power. Mining at the Lake Kepwari site began 50 years ago and concluded in 1996. The pit lake was repurposed and relinquished back to the Western Australia Government and the Collie community in 2020 as Lake Kepwari.
Kepwari is a Noongar word meaning “playing in water”. The transformation of the site also included the rehabilitation and revegetation of 120ha of land surrounding the lake.
25 years of studies, monitoring and reporting went into ensuring the successful transition of the Collie mining pit into a safe and usable asset that met the stakeholder-agreed closure objectives. Safe for swimming, boating and fishing, Lake Kepwari supports the promotion of the Collie region as a tourist destination. Fish and crustaceans have been successfully reintroduced and the lake has been incorporated into the Collie River Waugal Aboriginal Heritage site, which includes the entire Collie River system.
Stawell
Gold mining has long been integral to the local economy of Stawell. At its peak in 2011, the Stawell Gold Mines (SGM) was the largest employer in the area and contributed over $58.3 million to the local community in wages, purchased goods and services per year.¹
In 2013, following warnings by SGM that its operations might soon be closing, the community started seeking alternative uses for the mine that would maintain local employment levels.
The Northern Grampians Shire formed a Project Control Group consisting of a range of community representatives, local government, state government agencies, business operators and the mining industry, including SGM, to consider potential transformation and repurposing initiatives for the SGM assets.
At the same time, physicists were seeking a southern hemisphere location for a deep cavern in a rock protected location to conduct experiments for the potential detection of dark matter – the mysterious substance that is thought to make up 80 per cent of matter in the universe.
The Stawell Underground Physics Laboratory (SUPL) was subsequently proposed, located 1km below ground in what was, until 2012, a deep volcanic basalt gold mine cavern. The depth, equivalent to a shield of 3km of water, blocks the earth’s surface radioactive cosmic waves which are unable to infiltrate the abandoned mining tunnels. This maximises the effectiveness of the very sensitive detectors and sensors for exploring the theorised existence of dark matter.²
In July 2019, a formal agreement between Stawell Gold Mines, the Northern Grampians Shire Council and the University of Melbourne was signed to build and operate the laboratory with funding from the Federal and Victorian Governments as well as the Australian Research Council.
SGM agreed to excavate the required underground cavern. While the mine continues to operate, it provides ventilation, vehicular access, power and fibre-optic infrastructure and water management for the SUPL.
Stage one of the project involved constructing the laboratory, which was unveiled in August 2022. It occupies a bespoke cavity created by excavating two interconnected caverns. There is enough room for experimental laboratories, physical plant and other support facilities, loading bays and lay down areas.³
The next step to be completed is the transporting of the Sodium Iodide with Active Background Rejection Experiment (SABRE) into the lab. Data collection is expected to begin later in 2023.
The Stawell facility, once operational, will attract physicists, scientists, research students and potentially even scientific tourists from around the world for extended periods, offering a tourism boost for the town.
SUPL will provide further research opportunities beyond dark matter. It is expected that SUPL and other projects in the lab will generate 80 new jobs and an estimated $18 million annual boost to the local economy through the attraction of new business opportunities to the town.⁴
When it comes to post-mining land use, rehabilitation and restoration are not the only routes available. Recent years have seen an increase in land repurposing for tourism, recreation and economic opportunities.
The repurposing activities at Stawell and Lake Kepwari demonstrate how long-term planning and collaboration between mining operators, the community, stakeholders and government can lead to the creation of valuable assets once mining operations cease. However, while achievements have been made in rehabilitating and repurposing mine sites across Australia, there are abundant opportunities to ensure degraded land is restored or rehabilitated with the best possible result. Following leading practice in post-mining land use secures more sustainable outcomes for communities and leaves behind a positive legacy.
Footnotes:
- Northern Grampians Shire Council 2014, The Stawell Underground Physics Laboratory: The Northern Grampians Shire Council’s Response to the Regional Development Australia Grampians Committee GREAT Project Assessment Tool, Stawell.
- Slezak, M 2014, Panning for dark matter in an Australian gold mine, New Scientist. Retrieved from https://www.newscientist.com/article/mg22329782-800-panning-for-dark-matter-in-an-australian-goldmine/?ignored=irrelevant
- Urquijo, P 2016, Searching for dark matter at the Stawell Underground Physics Laboratory. Paper presented at the Heavy Ion Acceleration Symposium 2016, pp 1–7. arXiv:1605.03299. doi:10.1051/epjconf/201612304002, Canberra
- Northern Grampians Shire Council 2014, The Stawell Underground Physics Laboratory: The Northern Grampians Shire Council’s Response to the Regional Development Australia Grampians Committee GREAT Project Assessment Tool, Stawell.
