Consideration of the risks per-fluoroalkyl and poly-fluoroalkyl substances pose in adopting suitable mine closure rehabilitation milestones and completion criteria

Authors: East, K; Maier, A; Gimber, C Download Paper Open access courtesy of:

DOI https://doi.org/10.36487/ACG_repo/2215_30

Cite As:
East, K, Maier, A & Gimber, C 2022, 'Consideration of the risks per-fluoroalkyl and poly-fluoroalkyl substances pose in adopting suitable mine closure rehabilitation milestones and completion criteria', in AB Fourie, M Tibbett & G Boggs (eds), Mine Closure 2022: Proceedings of the 15th International Conference on Mine Closure, Australian Centre for Geomechanics, Perth, pp. 439-448, https://doi.org/10.36487/ACG_repo/2215_30



Abstract:
There are a number of activities associated with mining operations that may result in release of a range of constituents of potential concern (COPCs) into the environment. However, impacts associated with per- and poly-fluoroalkyl substances (PFAS) have the potential to require investigations (and potentially remediation) with cost, time and reputation implications over and above ‘conventional’ contaminants, due to the nature and behaviour of PFAS. These manufactured chemicals are known to be persistent in the environment, bioaccumulative in organisms and toxic at relatively low concentrations (PBT). As COPCs are most commonly discussed in relation to fire training activities at defence facilities and airports, the risks and liabilities to mine operators from PFAS related issues are not fully understood or adequately quantified. Undertaking environmental due diligence audits of mine operations (as the first stage of assessment) will provide a sound basis to develop a conceptual site model (CSM), in turn enabling order of magnitude (OoM) provisioning and scheduling in order to plan for any remedial and management measures associated with PFAS. Given the PBT nature of PFAS and the disturbed hydrogeological and hydrological systems associated with mine sites, there are potential risks to air, water and soil quality (and therefore rehabilitation success) that, if not better understood, may limit the practical adoption of appropriate remediation and monitoring measures to achieve relinquishment. Such risks include long-term uncertainty in water quality projections, particularly if a mining void is left as a permanent sink for groundwater or if the site is near a sensitive receiving environment. The implications this may have on setting reasonable and effective rehabilitation milestones and completion criteria are not fully understood, and if not appropriately considered, may also limit the assessment of reasonable residual risk posed. Key aspects to be discussed include (1) why the presence of PFAS (compared with ‘conventional’ contaminants) may require longer-term planning; (2) what are the long-term risks PFAS poses in terms of achieving relinquishment/accepted post-mining land-use (PMLU); (3) how can these risks be appropriately managed, including a proposed framework for creating appropriate rehabilitation milestones and completion criteria in terms of PFAS; and (4) implications for capturing sufficient closure provisioning based on the unique requirements for PFAS investigations, waste management and remediation.

Keywords: per-fluoroalkyl and poly-fluoroalkyl substances, contaminated land, remediation, mine closure planning

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