The holistic approach of the Global Industry Standard on Tailings Management (GISTM) considers risks throughout the lifecycle of a Tailings Storage Facility (TSF) - including the decades following closure and, in some cases, even longer where stability or environmental concerns persist.
This has re-emphasised the importance of closure planning for mines, and the need to build these considerations into the initial mine design phase. James Lake, Partner and Principal Environmental Scientist at SRK Consulting South Africa (SA), said that closure is a theme that runs through the GISTM principles.
"The standard is explicit about the owners' responsibility to plan, build and operate TSFs to responsibly manage risk at all phrases of the lifecycle including closure and post-closure", said Lake. "This applies as much to the rights of project-affected people as it does to the maintenance of an interdisciplinary knowledge base and the operation of monitoring systems".
Robust Designs
Recent years have seen considerable activity in the mining sector to bring TSFs into compliance with the GISTM, and Lake noted that TSF designs are becoming more robust. Among the considerations is the likely impact of climate change, for instance, which will require tailings dams to remain stable in conditions of higher or more intense rainfall.
According to Roanne Sutcliffe, Principal Environmental Engineer at SRK Consulting SA, the GISTM reiterates the principle that effective closure planning begins when mines are being conceptualised and designed.
“The operational life of a mine and its TSF is typically measured in decades”, said Sutcliffe. “In contrast, when considering the post-closure aspects of a tailings facility, the design life will need to be much longer in most instances and may need to be considered in terms of centuries”.
In terms of the GISTM, mines need to be able to demonstrate that – from a chemical and physical stability perspective – TSFs will remain stable throughout the operational phase and for centuries to come after mine closure. She noted that an ‘active closure’ period typically follows for 10-20 years after a mine ceases operations, where the TSF requires a maintenance and monitoring team almost commensurate with the team required for operations. After that, a more ‘passive closure’ regime may be sufficient – where the teams involved slowly reduce but would last for many more decades if not centuries.
