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Evaluating the benefits of water covers as a rehabilitation strategy in temperate climates: a Tasmanian perspective
Citation
Jackson, L and Parbhakar-Fox, A and Gregory, D and Hughes, A and Agius, J and Ferguson, T and Lester, D, Evaluating the benefits of water covers as a rehabilitation strategy in temperate climates: a Tasmanian perspective, Proceedings of the 10th International Conference on Acid Rock Drainage and IMWA Annual Conference, 21-24 April 2015, Santiago, Chile, pp. 1-11. ISBN 978-956-9393-28-0 (2015) [Refereed Conference Paper]
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Abstract
Environmentally safe disposal of reactive sulphidic tailings is one of the major management
challenges facing the mining industry. Consequently, there are a broad range of tailings
rehabilitation strategies suitable for a variety of climates. One option is placement of tailings under
a water cover to reduce oxygen influx. However, for sites in Australia that lie in a cool temperate
climate, the suitability of engineered water covers is not well documented. The Old Tailings Dam
(OTD) located at the Savage River Mine, Tasmania provides a unique opportunity to evaluate water
covers as a rehabilitation strategy. The OTD extends roughly 1500 m northeast to southwest and
170 m east to west at its widest point (Hassell, 2005). The northern end is submerged under water,
as the OTD was constructed on a natural gradient. Therefore, up to 0.2 km2 are permanently
submerged under water (maximum depth of 10 m) with some seasonal variation. In contrast, the
southern portion in contrast has been exposed since 1982. Tailings from 14 trenches and 11
sediment cores were collected across the OTD. Selected samples were subjected to geochemical
testwork and also used in mineralogical studies whereby a modified sulphide alteration index was
developed. Results revealed a complex, heterogeneous sediment architecture with ten facies
observed. From this, four zones were defined (A, unsaturated and coarse-grained, B- unsaturated
and fine-grained, C- intermediate saturation and D- saturated). Geochemically, Zone D was
identified as the lowest risk, with Zones A to C classified as having a high to extreme acid forming
nature, which concurred with bulk mineralogy evaluations showing relatively high quantities of
unoxidised pyritic tailings (5 to 9 wt. %). Sulphide alteration index assessments allowed for
oxidation to be observed on a micro-scale, and indicated that a minimum water cover depth of
approximately 1 to 1.5 m would be sufficient to significantly retard oxidation. Ultimately, a phased
rehabilitation strategy which requires geotechnical earthworks and installation of flow-through
reactors in combination with a water cover should be developed to successfully reduce AMD from
this site.
Item Details
Item Type: | Refereed Conference Paper |
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Keywords: | cover, tailings, mineralogy, acid mine drainage |
Research Division: | Earth Sciences |
Research Group: | Geochemistry |
Research Field: | Exploration geochemistry |
Objective Division: | Environmental Management |
Objective Group: | Terrestrial systems and management |
Objective Field: | Evaluation, allocation, and impacts of land use |
UTAS Author: | Jackson, L (Miss Laura Jackson) |
UTAS Author: | Parbhakar-Fox, A (Dr Anita Parbhakar-Fox) |
UTAS Author: | Gregory, D (Dr Daniel Gregory) |
ID Code: | 100067 |
Year Published: | 2015 |
Deposited By: | Earth Sciences |
Deposited On: | 2015-04-29 |
Last Modified: | 2017-11-02 |
Downloads: | 4 View Download Statistics |
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