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Land restoration and mine rehabilitation

Our land restoration and mine rehabilitation research has concentrated on the revegetation of mine residues to complement expertise on mine rehabilitation available in other research groups in WA. This research has pragmatic goals to find solutions to land degradation problems on mine sites, and has been a fertile area for the training of students at the masters, honours and 4th year undergraduate level. Our mine rehabilitation research also benefits from collaboration with the Centre for Land Rehabilitation, University of Western Australia. The major joint project with CLR was commenced in January 1999 with a study funded jointly by Worsley Alumina and Alcoa (see summary below). The Land Management Group was involved in the organisation and hosting of the Second International Conference on Remediation and Management of Degraded Lands (Remade Lands 2000) held at Fremantle from 30 November to 1 December 2000.

This research is split into two main areas

  • Gold ore refining residue
  • factors affecting revegetation success at bulong nickel operation

Gold Ore Refining Residue

The focus of this study was the revegetation of gold-processing residue storage areas located in the eastern jarrah forest in the south-west of Western Australia. Ore refinery residues are among the most difficult of substrates to revegetate, because of the extreme chemical, physical and biological properties of the material. Since 1991, we have worked with Boddington Gold Mine and Hedges Gold Mine to identify the limiting factors to plant growth on gold ore refining residue and to develop strategies for growing plants on the material.

The principal component of the research was a large field experiment investigating treatments, identified in the earlier phase of research, to improve soil conditions for plant growth, and determine the suitability of native species for residue rehabilitation.

Generally, the growth of plants exceeded expectations and a wide range of species have proved suitable for use in rehabilitation of residue storage areas, including many from the jarrah forest. The requirements for optimum vegetation establishment appear to be: treating the residue with gypsum to assist in the reduction of salinity, sodicity and alkalinity; using 10 cm of a sandy gravel topsoil covering on residue to maximise the survival and establishment of seedlings over the first year, and; providing adequate nutrient sources for plant growth. Based on this prescription, vegetation was well established and had density and canopy cover comparable to bauxite mine revegetation. Species diversity was very dependent on an appropriate seed mix and favourable seedbed conditions supplemented by transplants. The topsoil had little value as a seed source. The necessity for long term topsoil storage on site means that little can be done to overcome this limitation in the value of topsoil.

The study has demonstrated that vigorous, diverse vegetation can be established on the residue using a simplified prescription compared to that previously recommended (Bell et al., 1999). The simplified prescription involves fewer operations and decreased use of machinery for land preparation. Not only that but a much wider diversity of plant species were rapidly established than in the previous prescription, and the reliance on potentially weedy, pioneer species has been avoided. The revised prescription should be a more cost-effective method for achieving satisfactory rehabilitation of the perimeter areas of RSAs.

Factors Affecting Revegetation Success At Bulong Nickel Operation

The primary objective of this research was to investigate the constraints for successful mine site revegetation at the Bulong Nickel Operation (BNO) in the arid Eucalyptus woodlands of the Eastern Goldfields of Western Australia. The chemical properties of two waste dump substrates and one sub-soil at BNO were investigated to determine the nature of the material and its suitability for growth of the legume, Acacia acuminata subsp. burkittii and the salt tolerant blue bush, Maireana pyramidata. The most serious constraint affecting successful revegetation of the waste dumps at BNO is the inhospitable nature of the overburden used to construct the dumps.

Current rehabilitation plans envisage the creation of waste dumps using this material and placing a 15-cm layer of topsoil over the top as a seedbed for germination and plant growth. 

Further research is required to investigate the effect of gypsum and organic matter on the physical properties of the material and the subsequent effect on plant growth. However, it is strongly recommended that research be undertaken into the characterisation of the sub-soils and overburden materials at BNO to determine if more benign substrates can be identified within the overburden and sub-soil materials in the mine waste steam.