Prior to mining an initial site assessment is performed to identify potential physical constraints and risks that may prevent rehabilitation. Key considerations would include law requirements and community views through public consultations. This planning stage is important to validate methods that will be used to manage risks, develop a success criteria which rehabilitation can be measured against and monitoring success. Rehabilitation phases are then divided into sub-components: landforming, soil management, water management and the establishment of vegetation.
Landforming involves the reshaping and grading of any disturbed topography, and of particular importance is the need to reshape slopes. It needs to be carefully considered since earth moving is the most expensive part of rehabilitation. Soil management is of vital importance as it is here where many seeds and propagules are stored and is the prime site for nutrient cycling in terrestrial ecosystems. Soil can be also be removed and stockpiled or transferred from one site to another but its handling must be closely observed to certain conditions ensuring seed viability. Water management is vital in order to minimise the level of disturbance. It must be managed to avoid pollution due to erosion and sediment deposition, either at the point of discharge or further downstream. This is a vital process in aiding the establishment of vegetation, reducing run-off and managing water leaving the site. The successful development of vegetation in mining rehabilitation depends on a number of factors. There needs to be adequate plant nutrients and soil physical and chemical environmental conditions which are conductive to the growth of plants. After disturbance by mining and the creation of a new soil system, the rehabilitated soil medium can be compacted, have reduced fertility or be contaminated with salts and/or toxic elements.
Monitoring is the principal means of re-using information gained from the rehabilitation effort. There are various components of ecosystem functions that require continued observance in order to check against the pre-determined completion criteria. It may take 10-20 years before the rehabilitated site is considered to be complete with respect to the long-term land use. Regular monitoring will also enable assessment of the success of the whole process and detect trends where decisions can be made as to whether to manage the rehabilitation site further. The rehabilitation team can also study and predict the success and long-term outcome of specific rehabilitation practices to be used in future situations.
The quality and long-term success of mine site rehabilitation is dependent upon research. This is especially the case where the need is to rehabilitate the site back to a self-sustaining functional ecosystem. Establishment of an ecological knowledge base also will help to ensure that the rehabilitation of mined lands will ultimately produce a self-sustaining ecosystem comparable to the pre-mining condition. Experiments such as developing techniques for growing trees on overburden or dormancy mechanisms are examples of academics making progressive inroads for effective rehabilitation results.
Rehabilitation should be part of an integrated program of effective environmental management through all phases of resource development, from exploration to construction, operation and closure. Sustainable development requires the current generation to prevent the negative environmental and socio-economic legacies which remain long after the mine has originally closed and been rehabilitated. Hopefully, it is this discipline that will ensure continued funding and support from political, economic and social stakeholders and set better environmental standards to ensure greater mine-site rehabilitation success.
photo credit: <a href="http://www.flickr.com/photos/greenfleet/6946323452/">Greenfleet Australia</a> via <a href="http://photopin.com">photopin</a> <a href="http://creativecommons.org/licenses/by-nc-nd/2.0/">cc</a>
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