Case Studies of Metal Leaching/ARD Mitigation and Assessment at British Columbia Mine Sites – Snip Gold Mine
British Columbia MEND Case Study Project
The objective of MEND Case Studies is to show the practical experience with different aspects of ML/ARD mitigation and assessment practices at well-characterized sites. In the British Columbia MEND Case Study Project, case studies were produced from the extensive work completed at Johnny Mountain Mine, Snip Mine and the Sulphurets project, three of the more than 60 mines in British Columbia with significant metal leaching / acid rock drainage concerns. The MEND Initiative intends to add additional case studies from BC and other sites in Canada. The information provided on prediction and design and the resulting performance should improve the ability of the mining community to estimate mine site liability and prevent future impacts.
The three British Columbia case studies outline site-specific issues and key design and performance parameters, along with constraints, information gaps, errors and their management implications. This information on operational practices should be of interest to educators, regulators and the public, in addition to practitioners directly or indirectly employed by the mining industry.
In each case study, an attempt was made to describe the evolution in understanding and the rationale for decisions, in addition to the results. Raw data are provided so readers can make their own assessments. There are also appendices explaining the theory behind some of the procedures used for the prediction of drainage chemistry. The inclusion of raw data along with maps and photos allows the reader to draw their own conclusions and could enable the case studies to be used as an educational tool in which students could be given the raw data and asked to predict the drainage chemistry, develop a mitigation plan and decide what additional test work and management practices they would recommend.
Conclusions from the case studies include the following.
• Samples should be spatially, temporally, physically and geochemically representative of and include the materials, events or locations of most concern.
• Assumptions regarding sampling, analysis and field performance should be checked. Before proceeding with monitoring, identify the objectives and question(s) that need to be answered and how the answers will be used.
• All plausible outcomes, hypotheses or mechanisms should be presented, not just the most easily managed.
• It is important to show how proposed explanation(s) may be verified if correct, or proven wrong if incorrect.
• Environmental problems may result from a relatively small portion of the mass and therefore variability and distribution of results are often more important than the central tendency.
• Not all properties and processes can be accurately measured and a critical part of management is dealing with this uncertainty.
These conclusions indicate the importance of evaluating the practical details and taking a scientific approach in the prediction and mitigation of sulphidic mine drainage. They also indicate that no amount of QA/QC, statistics, computer modeling and expert opinion will help if the assessment ignores some of the key properties, materials, events or processes, such as maintenance requirements.
