Integrating decision analysis, engineering and water quality modelling for remedial option evaluation of the 2200 level and Mount Sheer townsite at Britannia Mine Jia, Kun; Mills, Ryan; Sumsion, Stephen; O'Grady, Tyler
This case study presented a modified MAA approach that considers copper load reduction and cost to evaluate and select a preferred remedial option for the management of mine waste. A remedial option evaluation was undertaken to identify, design, cost and evaluate risk-based remedial options that could be employed to reduce copper loadings to Britannia Creek by >50% and address unacceptable aquatic risks at the 2200 Level of Britannia Mine. Previous investigations found the primary sources of copper were waste rock, highly leachable copper plant residuals and contaminated soils. Remedial approaches were screened for five Areas of Environmental Concern (AECs) using a modified Multiple Accounts Analysis approach with input from experienced professionals at technical workshops. Five remedial options were designed for the 2200 Level and two remedial options were developed for Mount Sheer using best management practices for control of metal leaching and acid rock drainage. Remedial options utilized passive approaches to maintain separation between clean water and waste materials at the remote unpowered site. Remedial options and detailed cost estimates were developed in consideration of the Overall Closure Plan Framework for the Britannia Mine Site. A water balance and water quality model was developed based on the Conceptual Site Model to quantitatively estimate copper load reduction to Britannia Creek for each remedial option. Input data for the model was obtained from public sources and historical studies documenting the extents of the AECs, geochemistry of waste materials, hydrology and hydrogeology. The model was used to predict water quality in Britannia Creek and estimate copper load reduction for each remedial option. Two options did not achieve the remedial goal of 50% copper load reduction and were abandoned. The other three options met the remedial goal with an estimated reduction of 65-69%. The preferred remedial option was selected after consideration of capital costs, long-term costs and estimated load reduction that is supported by a rapid, defensible and traceable evaluation process.
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