Abstract
Tailings dams remain on site following mine closures and must be designed and reclaimed to meet long-term goals, which may include walk-away closure or long-term care and maintenance. The underperformance of these structures can result in significant risks to public and environmental safety, as well as impacts on the future land use and economic activities near the structure. In Alberta, Canada, the expectation is for a tailings dam to be reclaimed and closed so that it can undergo deregistration. To aid in assessing the risks of underperformance during and after closure, a Generalized Failure Modes and Effects Analysis (G-FMEA) framework was developed to assess the long-term geotechnical risks for tailings dams in Alberta, with the goal of assessing the potential success of a tailings dam closure strategy. The G-FMEA is part of an initiative to enhance closure evaluations in Alberta in a collaborative effort between industry, the regulator, and academia. The G-FMEA incorporates the element of time to account for the evolution of the system, which should be applied at the planning stage and updated continually throughout the life of the facility. This paper presents the developed G-FMEA framework for tailings dams in Alberta, including the developed risk matrix framework.
Highlights
Tailings dams were designed with the consideration of geotechnical failure modes that could occur during the active life of the mine
This is problematic as the failure of these structures can still occur after the closure of a mine site, such as at the Matachewan Consolidated Mine in Ontario [1]; or when the mine is in a period of care and maintenance, such as at Obed Mountain Coal Mine in Alberta [2]
This paper presents the developed Generalized Failure Modes and Effects Analysis (G-FMEA) framework, including a developed risk matrix framework
Summary
Tailings dams were designed with the consideration of geotechnical failure modes that could occur during the active life of the mine. With the impending closure of a number of external tailings facilities in Alberta, a Generalized Failure Modes Effects and Analysis (G-FMEA) framework was developed to assess the landform design for closure. This assessment should ideally be conducted before mining begins (during permitting) and updated as the project progresses. While further advancements and an increased confidence in the results of the runout modelling and inundation mapping are useful for understanding the risks associated with flowable tailings, they may not be useful tools within the current deregistration framework They remain useful tools for assessing the long-term risks of tailings facilities where it is not possible to remove the flowable tailings or for orphaned facilities. The G-FMEA charts developed as part of the framework present the failure modes that are applicable to closure and should not be used to assess dam safety during construction or operation
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