Leading practice waste dump rehabilitation at the Ginkgo mineral sands mine

Abstract

Bemax Resources Ltd operates the Ginkgo mineral sands mine located 35 km west of Pooncarie in far western New South Wales. Large 'start-up' overburden stockpiles are present at the mine site and will remain after closure. The first overburden stockpile to be constructed and revegetated is overburden stockpile OB3, which covers an area of 34 ha. Material characterisation studies by Landloch Pty Ltd provided detailed information on runoff and erosion potential of the outer batter slopes, underpinning recommendations with respect to batter profiles, heights, and gradients, and surface treatments such as placement of tree debris to control wind and water erosion. Associated trials have shown the value of tree debris in reducing impacts of sand movement on emerging seedlings. Perimeter and cross bunding to manage runoff from the top of the landform were also recommended. Soil stripping operations have followed a two-step process, using tractors towing laser scoop buckets to ensure accurate collection and placement of topsoil and subsoil layers. Stockpile management aimed to minimise deterioration of topsoil properties, though significant changes in a range of soil parameters have been documented, leading to some modification of existing practices. Vegetation studies guided development of seed mixes for direct seeding, which was carried out using a dozer-mounted drum seeder able to work through the tree debris. The initial seeding shows excellent stability to erosion, and observations have confirmed the importance of perimeter bunding. Initial soil and vegetation monitoring confirms establishment of a chenopod shrubland vegetation at the desired indigenous plant cover levels, but has identified a need for improvement of soil fertility in subsequent rehabilitation operations (continuing improvement is essential). Data from the various stages of design, rehabilitation and monitoring are presented to illustrate the range of areas to be addressed if rehabilitation is to be successful. https://papers.acg.uwa.edu.au/p/1208_07_Loch_Squires/ Leading practice waste dump rehabilitation at the Ginkgo mineral sands mine H. Squires et al. 60 | Mine Closure 2012, Brisbane, Australia Successful mine site rehabilitation requires a high standard to be maintained across all components of the process, from planning through to execution and monitoring. Failure to achieve high standards in only one component of the project may be sufficient to cause overall failure. Well planned and executed rehabilitation does not guarantee success. Extreme rainfall events are always possible, but adoption of leading practices regularly achieves considerable reductions in rehabilitation costs, and strongly increases the probability of success. It makes sound economic sense to get mine site rehabilitation right the first time. This paper details the rehabilitation methods applied at the Bemax Ginkgo Mine, and the results achieved by its combination of sound science and sound construction practices to achieve cost-effective and excellent rehabilitation outc...

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