Mining doesn’t have to leave a big hole in a community’s life once its useful life is over. There are many creative ways in which mine void transformations can benefit the whole community, writes Atlantech Director and Environmental Lead, Jason Desmond.

What is Mine Rehabilitation?

Mining operations are expansive and complex however they are still only temporary. Once all the accessible and valuable materials have been extracted, the site must be restored to a state that meets stringent environmental standards.

Rather than just covering up mine entrances, replanting grass and trees and testing water, soil and air for contaminants, there are many creative ways mine voids can be beneficial to the community after mining without being a burden or seen as an unused space essentially.

Typical post-mining land uses include crop production, grazing, ecological restoration or forestry. A two-year Upper Hunter Mining Dialogue study coordinated by the NSW Minerals Council has also looked at a wide variety of potential uses for mine voids. Suggestions included irrigation, flood mitigation, aquaculture, and hydro-electric power generation.

Pit lakes, or recreational lakes, are also an example of how post-mining land can be used after mining to benefit communities. Lakes provide increased tourism in regional and remote areas, add possibilities for eco-tourism such as kayaking tours and sailing activities, and provide highly sought-after sport and recreational activities for communities. One of the community concerns from such pit lakes is the water quality and any effects on human health or wildlife. Water quality modelling, in particular salinity modelling completed at the start of a mine life is quite conservative. This modelling takes into account the “worst case” scenario which is often a lot less than the salinity of sea water. Some known examples within Australia and across the world have in fact allowed human access a lot sooner than predicted. An influencing factor is completing effective mine rehabilitation in the mines operational phase well ahead of the mine’s end life.

Although mining conditions today are more stringent than ever and detailed restoration steps are included as part of the life-of-mine plan, there are some great examples of older mining areas that are now providing benefit to the community.

Creative Restoration Examples

• Central Germany

Take for example old mine voids that have been turned into recreational lakes, such as a mine district in central Germany which is being transformed into a lake district.

The district, which was once a centre for open-pit mines extracting lignite, or brown coal, for power generation, is now being reclaimed to serve completely different purposes. It is transforming from a district known for its unsightly pits to a pools district, as seen in NASA satellite imagery. More than 150 years of mining in the district took its toll on about 1770 square kilometres of German countryside – disrupting land and water environments and increasing greenhouse gas emissions. Somewhere in the 1990’s, miners, conservationists, governments, and water management leaders collaborated to create recreational spots for people, habitats for animals and amphibians, and places for flood management. At least 140 lignite mines have been reportedly filled to create artificial “pit lakes” across central Germany.

• Western Australia

An old coal mine was transformed into a camp site and ski lake in Western Australia. Lake Kepwari, just two hours from Perth, is now a popular tourist destination for boaters, campers, caravaners and water sport enthusiasts. Previously the site was the W05B coal mine for almost 30 years. Mining began in 1970 and when it closed a giant hole was left in the ground, which was backfilled in some areas, and then left to fill with water. In recent years, extensive work was done on the campground and surrounding area to make it a tourism destination. The waterbody has a 5.4km perimeter and is 65 metres at its deepest point. The lake and campsite officially opened in 2020.

Nearby, also near Collie in Western Australia is the Black Diamond Lake, with its vibrant blue waters. The lake, which is for strictly day use, is an example of a stunning artificial lake created from a disused open cut mine.

• Winery, Germany

In central Germany there is an interesting example of a former opencast mine which closed in 1993 and was progressively transformed into the country’s largest artificial lake, with a winery on its slopes. Following extensive earth and remediation work, Lake Geiseltalsee is more than 18 square kilometres. The lake helps reflect sunlight on to the grape vines at the winery, while the air’s moisture surrounding the lake aids in protecting the vines from frost during the winter.

Different Mine Rehabilitation Styles

Organisations carrying out mining activities are legally obligated to rehabilitate land where practical, so what are the different rehabilitation styles? Note there are different, essential regulatory approvals required based on what state in Australia mines operate. Companies need to regularly report (usually annually) on rehabilitation progress in line with their approval conditions.

As defined by the Australian Government in its handbook Leading Practice Sustainable Development Program for the Mining Industry, mine rehabilitation should be designed to meet three key objectives:

1. The long-term stability and sustainability of the landforms, soils, and hydrology of the site.

2. The partial or full repair of ecosystem capacity to provide habitats for biota and services for people (WA EPA 2006).

3. The prevention of pollution of the surrounding environment.

While a detailed life-of-mine dump balance is key in designing a final void, it’s important the volume and size of final voids are set for a mine’s entire life instead of just the final phase of mining. Decisions for the final voids need to consider a range of factors, including:
• The potential pollution impacts on creeks, aquifers, and other areas.
• Geotechnical risks of voids (for example if they are close to built or natural features).
• Mining tenure and land ownership constraints.
• Freeboard to minimise discharge to the external environment.
• Safe access.

The main types of rehabilitation practices include:

• Hydrogeology: Developing a conceptual model of the mine’s groundwater systems.
• Soil and capping material assessment – soil assessment activities (including topsoil) are carried out at appropriate intervals.
• Waste characterisation: Characterising how waste materials are likely to physically behave and chemically react in conditions they would be stored.
• Flooding: When flood plain modelling is used to rehabilitate mines to stable conditions.
• Landform and cover design: Land that is safe and structurally stable is the aim of a final landform design, while a cover design is needed for surface treatment and other waste material in a mine’s landform.
• Revegetation: A revegetation plan that includes methods to establish self-sustaining vegetation communities for post-mine life.
• Management of water: Long-term rehabilitation success is dependent on the success of a plan for surface and groundwater management.
• Tailings storage facilities (TSF): TSF often have the most hazardous materials and can place significant risk to environmental values. It is important they are managed effectively.

o The Minerals Council of Australia has a helpful resource for mine rehabilitation, closure planning and regulation here.

Is your life-of-mine, progressive rehabilitation and closure planning adequate?

Rehabilitation is an integral component of a mining company’s sustainable development strategies and forms part of how a company’s environmental performance is judged. We investigate and integrate rehabilitation planning into miners’ strategies and are up to date on the latest guidelines and legislation affecting the industry. Contact Atlantech for a confidential discussion.

Sources

• NASA Earth Observatory
• Leeeipzigseen
• Collie River Valley
• 4WDING Australia
• Perth Now
• Minerals Council of Australia (flyer)
• K3fly
• Australian Government (mine rehabilitation handbook)
• Glencore (fact sheet final voids)