PASTE & TAILINGS 2021
Above : Chloe Bolton , right : Ashleigh Maritz
outfall pipelines . Pools can therefore still be responsibly decanted in the event of heavy rainfall , eliminating the concerns related to freeboard or over-topping , as well as excessive siltation in the decant water with subsequent siltation of the silt traps and return water dam basins .
In terms of addressing the risk of dam breaching , the application of probabilistic analysis presents an opportunity to incorporate climate change models into various breach scenarios . It is likely that such analyses will form an integral part of dam breach studies before too long . strategies for affected communities to lodge complaints about dust so that action can be taken . Ongoing rehabilitation and vegetation of the outer slopes remains an economical and efficient strategy to minimise dust being generated from TSF beaches and slopes . There is increased use of indigenous plants in this application , with some mines now harvesting wild grass seeds for use on TSF slopes . It is not uncommon for the TSF operators to have a nursery on site where thousands of young seedlings are prepared for planting on the TSFs .
In conclusion , the management of water has always been central to the responsible design and operation of tailings dams . Climate change has become an important variable in this process , adding a level of uncertainty that will occupy the minds of scientists , engineers and TSF owners for the foreseeable future . For now , though , there is considerable expertise being invested in the adaptive management of these facilities , and the GISTM provides a valuable tool for measuring and auditing the ongoing interventions and improvements .
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* Chloe Bolton , Civil Engineer ; Grant Macfarlane , Partner and Principal Engineering Geologist , Ashleigh Maritz , Senior Environmental Scientist , SRK Consulting
Water consumption
The rainfall variability caused by climate change is also leading mine operators and consultants to investigate opportunities of reducing and optimising water consumption in plants and tailings production . This can involve the broader application of dewatering technologies to produce thickened tailings and paste – which behave in a different manner to conventional slurry tailings . This in turn requires new deposition methods , altered TSF designs and modified water management strategies .
Optimising the use of already treated water is also a focus , with channels and trenches adjacent to TSFs being lined to minimise seepage and potential pollution – and thereby maximise water recovery and the potential to reuse on-site water resources . Where operations either have multiple TSFs or adequate capacity , deposition can be optimised to minimise evaporation from beaches and supernatant pools , making more water available for mine use .
The hotter and drier periods that demand better stewardship of water also result in more dust being generated off the TSF beaches . To address this , mines have adopted deposition strategies that reduce the cycle-time of deposition . Responsible mines also monitor their dust fallout and have implemented
. Prevented .
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JULY 2021 | International Mining SUPPLEMENT P9