The Institute of Waste Management of Southern Africa (IWMSA) convened in Rustenburg, in the North West, last month to discuss a risk-based approach to the planning and management of residue stockpiles and deposits at mines.
The workshop offered participants the opportunity to gain a better understanding of the proposed amendments to the National Environmental Management: Waste Act.
IWMSA VP Jonathan Shamrock pointed out during the event that the proposed changes, which Environmental Affairs Minister Edna Molewa published last year, favoured a risk-based approach to managing residue stockpiles and deposits at mines. “The main aim of this approach is to allow for a pollution-control barrier system to be determined on a case-by-case basis, based on a risk analysis conducted by a competent person.”
Engineering consultancy Jones & Wagener technical director Marius van Zyl noted that the new risk-based approach used the source-pathway-receptor model. “The model starts with the source, where the pollution comes from. This can be anything from vehicle exhaust emissions to drums that leak oil.”
‘Pathway’ refers to “the medium by which the pollution will travel through the environment, such as air, land or water” and ‘receptor’ to who or what could be affected by the pollution emanating from the source, he added.
Mining consulting engineering firm SRK Consulting principal scientist James Lake highlighted the importance of the planning and management of residue stockpiles and deposits. He noted: that “The proposed amendments require one to determine the leakage rates through barrier systems, but they do not specify acceptable leakage rates. “Once the leakage rate is known, one needs to establish how the environment will be impacted, as this will differ from site to site.”
Jones & Wagener waste and tailings associate Riva Nortje explained how to estimate leakage rates using pollution-control barrier systems. She warned that leakage rates increase in magnitude through uninformed design and specification, poor construction quality control and operational issues.
Nortje also highlighted the importance of using competent and experienced specialists when determining reasonable leakage rates, as well as ensuring that the assumptions made when determining these rates were achieved in the design, construction, operation and rehabilitation stages.
Global consulting, design and construction services company Golder Associates technical director Dr Heidi Snyman discussed pathway receptor modelling, while Lake discussed the regulations that govern the planning and management of residue stockpiles and deposits.
Shamrack noted that the workshop was an excellent platform for waste management experts to discuss the implications of the draft regulations on the mining industry, which was responsible for over 80% of the waste generated in South Africa every year.
“We will continue to facilitate learning opportunities like this workshop to grapple with amendments to waste management legislation,” he said.