Environmental risk assessment as a tool for mine closure planning

Tommi Kauppila, Geological Survey of Finland, PO Box 1237, 70211 Kuopio, Finland; tommi.kauppila(at)gtk.fi

Environmental risk assessment (ERA), in its broad definition, consists of ecological and human health risk assessment (Kauppila et al. (eds) 2013). It is a systematic procedure for predicting potential risks to human health or the environment. Intuitively, the term risk contains an element of uncertainty or unpredictability, suggesting that environmental risk assessment should mainly be used to assess the effects and likelihoods of unforeseen events such as system failures or extreme climatic events. While such events should also be taken into account in mine closure planning, there are other types of uncertainties that can be studied using ERA. The consequences at the receptor may be uncertain and exposure concentrations may be difficult to determine exactly. We may, therefore, use ERA to compare the effects of different closure management decisions or design options on the receptor or the ecological or health value to be protected.

Environmental risk assessments generally employ the source-pathway-receptor conceptual model where hazards have sources (e.g., reactions in the tailings pond are the source of the hazard of metal rich seepage), pathways (the seepage percolates to groundwaters and is transported to a nearby well), and receptors (the well is used for human consumption). Such a framework is useful for the identification of closure-related risks as well. In general, ERA consists of four steps:

• Identifying hazards, sources, pathways, and the resulting exposure concentrations in the surrounding environment
  • Closed processes and facilities and their residual emissions
  • Contaminant transport and spread
  • Concentrations in surrounding media, speciation
• Determining exposure of humans and biota
• Characterizing ecological and health effects
• Integrating the risk characterizations

A full ERA is a complex and costly undertaking but it may be done in a tiered manner. Even compiling a conceptual risk model of mine closure will greatly increase the closure team’s understanding of the issues that need to be considered. The results of the EIA also may be utilized. A properly made EIA goes a long way towards providing information of the type that environmental risk assessment produces and the scope of the EIA should include the closure and post closure periods. As with stakeholder consultations, EIA and the mine closure process can support one another, providing cost savings.

References

Kauppila, T., Homulainen, H., Makkonen, S. & Tuomisto J. (eds), Ahvensalmi, A., Backnäs, S., Forsman, P., Huhta, H.-K., Karjalainen, N., Karlsson, T., Kauppila, P., Koikkalainen, K., Koivuhuhta, A., Kollanus, V., Kousa, A., Kuusisto, E., Mäkinen, J., Nerg, A.-M., Niittynen, M., Nikkarinen, M., Pasanen, A., Ruokolainen, S., Ryhänen, N., Solismaa, L., Tarvainen, M., Tornivaara, A. & Waissi-Leinonen, G. 2013. Metallikaivosalueiden ympäristöriskinarviointiosaamisen kehittäminen – MINERA-hankkeen loppuraportti. Summary: Improving Environmental Risk Assessments for Metal Mines: Final Report of the MINERA Project. Geological Survey of Finland, Report of Investigation 199, 223 p.