Key issues in mine closure planning related to pit lakes
Proceedings of the 10th International Conference on Acid Rock Drainage and IMWA Annual Conference
International Mine Water Association
School of Science / Centre for Ecosystem Management
Pit lakes form when surface mines close and open pits fill with water, either through groundwater recharge, surface water diversion or active pumping. Historically, the success in closing mines with pit lakes has varied tremendously: there are well known examples of legacy sites requiring perpetual treatment, whereas some other pit lakes have achieved various beneficial end uses. Although access to case studies is often limited, mining companies contemplating new open pit mines have a number of examples in both success and failure from which to draw “lessons learned” that can be used in future mine closure planning. This paper discusses key issues that should be addressed in the mine planning process to increase the likelihood of successful mine closure. Examples of issues and potential management strategies to address them are given. The key issues examined in this paper include: determining potential risks and beneficial end use opportunities, developing closure objectives and criteria, which may include various water quality, riparian and littoral targets; anticipating and meeting stakeholder and regulator expectations; subaqueous disposal of liquid and solid mine waste; predicting and managing water balances; identifying contaminants of concern; historical reliability of model predictions; mitigating acid mine drainage; the importance of understanding long-term vertical mixing regimes; and health and safety issues.