Effect of different stockpiling procedures on topsoil characteristics in open cut coal mine rehabilitation in the Hunter Valley, New South Wales

Abstract

There are currently 17 open cut coal mines in the Hunter Valley (New South Wales, Australia) 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 landuse. 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 and age on the physical, chemical and biological components of topsoil used to rehabilitate open cut coal mines in the Hunter Valley.