Open Cut » Environment
There are currently 17 open cut coal mines in the Hunter Valley that produce 58 Mt/annum of coal for export and domestic use. Mines are legislatively required to rehabilitate land on completion of mining operations. The most common rehabilitation objective in the Hunter Valley is to return mined land to pasture ecosystems for low intensity cattle grazing. Topsoil management is an important factor in determining the long-term success of rehabilitation and sustainable post-mining land-use. However, topsoil in the Hunter Valley is often scarce and of poor quality, in terms of its physical, chemical and biological properties. Current Department of Infrastructure, Planning and Natural Resources (DIPNR) guidelines recommend that if storage of topsoil is needed stockpiles should be constructed to a height of less than 3 m. However, no studies in the Hunter Valley have directly assessed the effect of stockpile height and age on soil quality. When compared to smaller stockpiles, larger stockpiles lead to the disturbance of smaller areas of land, and a decreased cost of construction and management. The major objective of this study was to examine the effect of increasing stockpile heights on the physical, chemical and biological components of topsoil used to rehabilitate open cut coal mines in the Hunter Valley.
The specific project objectives were to:
- Identify possible techniques to construct and manage topsoil stockpiles by conducting a literature review on previous studies undertaken within Australia and overseas (Keipert et al., 2002, chapter 3);
- Conduct a preliminary survey of existing stockpiles at 12 mines in the Hunter Valley and compare stockpiling practices to the Bowen Basin (Keipert et al., 2002, chapter 4);
- Establish and monitor a field trial at three mine sites in the Hunter Valley to investigate the effect of stockpile height and age on physical, chemical and biological properties of the topsoil (chapter 3);
- Establish a glasshouse trial to propose practical ameliorative measures to address topsoil degradation following stockpiling in the Hunter Valley (Keipert et al., 2002, chapter 6);
- Establish and monitor rehabilitation field trials to investigate the amelioration of stockpiled topsoil through plant establishment and soil properties based on the results of the glasshouse trial (chapter 4);
- Compare characteristics of sites rehabilitated with direct return versus stockpiled topsoil (chapter 4) and;
- Synthesise collected data and make recommendations on best practice topsoil management and rehabilitation techniques of the Hunter Valley (chapter 5).
The methods and results obtained in addressing these specific objectives of the project are outlined individually below and more detail can be found in chapters 3 to 5 of this report.