1. CHAPTER 1 INTRODUCTION Rehabilitation of Mined Land And

1. CHAPTER 1 INTRODUCTION Rehabilitation of mined land and the treatment of waste materials from mineral processing have become essential considerations for mining companies. The emphasis in recent times on rehabilitation is a reflection of modern attitudes toward the environment and a recognition of the need to protect the land resource. There is a greater awareness by mining companies, the community and the Government that safe, economic, and environmentally acceptable means of mine waste rehabilitation are required in an endeavour to reduce stream turbidity and pollution, minimize dust problems and return areas disturbed by mining to ecologically stable communities. In an era when mineral extraction is competing with other interests such as agriculture, forestry and urban development, and when the ever watchful eye of the environmentally minded is focused on the industry, the rapid rehabiliation of mined and waste disposal areas and the assurance of long term stability is essential. The majority of rehabilitation programmes are aimed at establishing a vegetative cover. There are many possible adverse chemical and physical conditions which are inhibitory to successful vegetative establishment. Mine sites and hence mining residues are very site specific with respect to their rehabilitation potential. The mineralogy, mining and processing method and treatment of waste materials will determine the physical and chemical characteristics of the material to be rehabilitated. The identification of the physical and chemical limitations to rehabilitation and the amelioration required has therefore become an essential prerequisite to the commencement of rehabilitation programmes. The aim of this study is to investigate the tailing disposal system of the New England Antimony Mines N.L. Company at Hillgrove, located 30 kilometres east of Armidale in New South Wales, to define the problems involved and to investigate the physical and chemical parameters of the tailings, with respect to the establishment of vegetation. This study results from an approach by the mining company to the Soil Conservation Service of New South Wales in 1976, to assist in the design of a tailings disposal system and provide recommendations for subsequent rehabilitation. 2. This thesis describes the mine environment, the milling and processing operations, and the design of the tailings disposal system, together with the investigations and experiments conducted on the tailings. Prior to the commencement of the investigations and experiments a literature review was undertaken to ascertain the current knowledge on mine rehabilitation. 3. CHAPTER 2 REVIEW OF LITERATURE 2.1 INTRODUCTION Revegetation of mining areas was carried out as early as 1815 when the Earl of Dudley made plantings on limestone workings at Dudley Castle and Wrens Nest in England (Whyte and Sisam, 1949). In South Africa, attempts were made in 1911 to control the dust nuisance arising from tailings dams. The general procedure was to spray the surface of the tailings with a sludge of black soil (James, 1964). In the United States, early rehabilitation work was undertaken by individual mining companies. However, it has not been until relatively recent times that a concerted and co-ordinated approach to rehabilitation has been adopted. The programmes have been initiated primarily as a result of public demand, individual company concern and conscience, and legislation. Kenahan and Flint (1971) have reviewed much of the work carried out by the United States Department of Mines, which pioneered work in the fields of secondary metals recovery and waste reclamation. Much of the early work was centred on the identification of natural colonizing vegetative species found on existing mined areas and waste sites. Brierley (1956) undertook such a study of 40 pit heaps in the Nottingham, Derbyshire and Yorkshire coalfields in an attempt to discover what factors led to the establishment of vegetation on such heaps, and the species of plants involved. Similiar studies have been carried out by Hall (1957) and Mitchell (1959). For all but the most hostile environments, natural revegetationfAlrill occur in the long term (Black and Truidinger, 1976). However, to achieve an effective cover which will reduce the erosion hazard and increase the stability and aesthetic appearance of mined sites and tailings areas the adoption of a sound programme to :establishh-vegetatiOn is-parumount. Natural recolonization will follow as a result of the improved physical and chemical conditions produced by the introduced species (James, 1966). Revegetation is universally recognised as an indispensable means of reclaiming strip mined land. Limstrom (1964) states that forestation is 4. recognised, as the most widely applicable type of vegetation, however, this would not necessarily be the case in the Australian environment. Massing (1974) cites a good example of co-ordinated development following lignite mining in the lower Rhine area of Germany. Of the 2 2,500 km which have been mined in the area since last century a total 2 2 cif 154 km have been restored; of this total 91 km have so far been 2 recultivated, approximately 45 km for forestry, approximately 34 km2 for agriculture and approximately 12 km2 for highways, housing and 2 recreational use. One of the Great Lakes covers 20 km and attracts over 20,000 visitors from the metropolitan areas of Cologne, Bonn and Dusseldorf at weekends. Erosion and leaching of waste dumps have caused considerable environ- mental pollution. Anderson et at. (1973) found a reduction in food supply and direct toxic effects from uranium mill waste on the biota. Verschuer (1976) stresses the need to incorporate the principles of landscape design into mining areas as rehabilitation success can be greatly enhanced. Dean et at. (1969) state that the principle requirements of plants which are used for vegetative stabilization are the ability of the plants to renew themselves and provide a suitable habitat for the encroachment of native plant species. Chenick (1960) states that plants should have the following properties to be successful rehabilitation species:- 1. Low growing - either bushy or mat forming. 2. Ability to develop quickly. 3. Herbaceous or perennial. 4. Frost resistant. 5. Heat resistant with an ability to withstand full exposure to the sun, on account of exposed habitats. 6. Easily propagated by seed or cuttings. 7. Production of abundant viable seed. 8. Ability to grow on an acid medium, but this is not universally essential. The establishment of an effective, self-perpetuating community of vegetation, which will afford maximum protection and stability whilst being aesthetically appealing, is the long term aim of the majority of rehabilitation programmes. Dean and Havens (1971) concur with the aim of establishing a self-perpetuating plant cover, but state that if this 5. cannot be achieved directly the vegetative stabilization should foster entrapment and germination of native plant seeds that will i be self- regenerating without the need for irrigation or special care. Permanence of vegetative cover could be achieved advantageously by selecting species adapted to growth, spread and reproduction (James, 1966). 2.2 TYPES OF MINE WASTE The type of mine waste has a major influence on the type of rehabilitation programme adopted and on the subsequent success of the programme. The general rehabilitation potential can be judged on the basis of climate, soil and vegetative site components, but each site will also have its own particular micro-climate in terms of specific physiographic, biotic and hydraulic components (Farmer et at., 1974). There is a great diversity of mining operations which produce specific waste materials of variable physical and chemical conditions. No attempts will be made here to discuss all of these, but the majority of operations will fall into one of the following broad categories. 2.2.1 Open cut Operations There are many scars on the Earths surface, especially in coal mining areas throughout Britain, Europe, the United States and Australia, which bear witness to the ravages of this process. The many forms of open cut mining are discussed by Gunnet (1975). He stresses the need to choose the best method for each particular case so as to ensure the selection of mining procedure that will provide maximum return on investment, desired production tonnages and effective land reclamation. Three broad categories of open cut mining can be recognised. Firstly, those operations which result in long term excavations and associated spoil dumps and/or benches. The surface mining for iron ore, copper and bauxite are examples of this type. The mining for bauxite in the Darling Range of Western Australia results in large excavated pits being left on the hillsides. Prior to the removal of the bauxite bearing material all topsoil.is removed. After the removal of the bauxite material, an infertile and densely compacted kaolin clay layer is left. Successful rehabilitation of these pits has been achieved by deep ripping, replacement of topsoil, contouring and planting of PhytophthoAa cinnamoni fungus resistant tree varieties (Anon, 1974a). 6. The second category is the open cut operations which allow for pro- gressive back filling of spoils. Strip mining for coal in the United States is a good example. Strip mining is the systematic process of simultaneously removing overburden and extracting the coal. This mining method facilitates the rehabilitation of the site in such a manner so as

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