The quality of a mine operator’s rehabilitation practices is a reflection of its social and environmental legacy, and a key factor against which the company’s overall environmental performance will be judged.
The Australian government’s Leading Practice Sustainable Development Program for the Mining Industry handbook outlines three key objectives of mine site rehabilitation. These include the long-term stability and sustainability of the site’s landforms, soil and hydrology; the full or partial repair of ecosystem capacity; and the prevention of pollution in the surrounding environment.
The Importance of Rehabilitation to Business Success
Successful mine site rehabilitation is critical to ongoing business success and the viability of future operations. Companies that can demonstrate leading practice mine rehabilitation methods will hold an advantage over competitors when it comes to securing land access and gaining future development opportunities.
Failure to meet stringent regulatory requirements around site rehabilitation could also lead to increased government scrutiny, restrictions on operations, higher compliance costs and possible legal trouble. A poor rehabilitation record can damage a company’s reputation, which will ultimately have adverse financial consequences.
Mine site rehabilitation is an undoubtedly costly process that requires careful planning and implementation. However, the consequences of neglecting this critically important area could be even more costly, in business, social and environmental terms.
Early Planning and Engagement to Ensure Effective Closure
Successful mine rehabilitation means starting with the end in mind. Planning begins early and communities should be engaged at the earliest possible time to help develop positive relationships.
Having an effective closure plan helps to ensure all necessary tasks can be completed on time and within budget, with appropriate resources allocated. Understanding stakeholder requirements, including community expectations for the final land use, can help to inform both technical and social decisions around closure.
Establishing a closure committee incorporating a wide range of stakeholders and community representatives can be a powerful way to gather community input and demonstrate to regulators that stakeholder input has been thoroughly considered in the closure plans.
Rehabilitating Landforms and Reintroducing Flora and Fauna
The rehabilitation techniques used may vary substantially between sites and are often informed by mining excavation methods and the proposed long-term use of the site following closure.
The physical landforms of the rehabilitated site can often be designed ahead of time through optimising waste dumping locations. With the rehabilitation plan in mind, initial dumping can be directed to the most appropriate locations so there is minimal need for final reshaping works following closure.
Surface roughness is another important consideration as a rough surface traps water and seeds to facilitate faster establishment of vegetation over the landforms. However, excessive roughness can increase erosion and instability in the longer term.
The plant species selected to revegetate post-mining landscapes are generally based on rehabilitation objectives and the intended land use. Different parts of a site may benefit from different species, with relevant factors including the physical, chemical and biological characteristics of the soil.
Native species are generally preferred, though non-natives may be considered in some circumstances. Sometimes, a cover crop is sown to protect the soil against erosion for the first year, while slower-growing native species establish themselves.
Animals will usually return to rehabilitated areas once native vegetation is re-established, though it can sometimes help to reintroduce some missing habitat components. This may include constructing nest boxes, transplanting mature grasstrees, or adding surface features such as logs and boulders.
Long-Term Management of Decommissioned Tailings Storage Facilities
Tailings storage facilities require careful management and monitoring throughout their life cycle, from the early planning and construction phases through active operations to their eventual decommissioning and closure. Aftercare and monitoring of decommissioned tailings storage facilities is an essential part of minimising their ongoing risks to the environment and public health.
Many of the usual operational risks associated with tailings storage facilities remain active following their closure, though some additional post-closure risks are added. These may include rainfall-induced erosion mobilising tailings, spillway failure or overtopping caused by rainfall run-off, and failure of cover systems placed on the tailings surface leaving exposed sediments vulnerable to wind and rainfall run-off.
The closure of tailings storage facilities must be carefully considered as part of the larger mine closure plan. The leading practice approach to closure planning requires the proposed post-closure land use and landform design to be defined and built into the tailings management plan as early as possible to ensure the most stable and cost-effective outcome is achieved.
Community engagement is particularly important when it comes to managing decommissioning tailings storage facilities to ensure concerns and expectations can be identified and addressed. The ultimate objective is to leave the facility safe and stable so that it won’t contaminate the surrounding environment and has minimal ongoing maintenance requirements.
Aftercare, monitoring and maintenance requirements typically extend for at least ten years following the closure of a tailings storage facility, although the extent and duration of these requirements depend on the site conditions and the type of tailings storage facility used.
Engage the Right Team for Post-Closure Success
Mining companies face increased pressure from regulatory authorities and shareholders to act in an environmentally responsible manner, so careful rehabilitation planning is now more important than ever. For optimal results, forward planning of closure objectives should begin while the mine is still operational.
Hall Water & Tailings has proven expertise and capabilities to assist in delivering your closure landform requirements, including:
– Achieving the final closure landform via the required combination of hydro-mining techniques and conventional bulk earthworks construction.
– Removing tailings, sediments, water and contaminated materials for reprocessing, in-line treatment or relocating to alternative disposal locations so structures can be safely decommissioned.
– Capping tailings facilities for closure through hydraulic material placement techniques with the aid of amphibious and conventional construction equipment.
– Placing topsoil using best practice material handling techniques.
– Applying a combination of seeding techniques to achieve short-term landform stabilisation goals and establish healthy ecosystems and assist in revegetation efforts, in line with closure rehabilitation objectives.