The consideration of ALARP (As Low as Reasonably Practicable) features in several state-of-the-art guidelines, such as the Canadian Dam Association, the Mining Association of Canada and the Australian National Committee on Large Dams, as well as in GISTM/ICMM. ALARP considerations can be applied to any project involving the selection of an appropriate level of mitigation, including the operations and closure phases of pits, dumps, and tailings storage facilities. In some literature, ALARP represents the trade-off equilibrium between remediation costs and risk reduction benefits. However, in its most modern definition, ALARP means that a residual risk, i.e., the risk after mitigation, shall be as low as reasonably practicable. To be considered ALARP, one requirement is to demonstrate that the cost involved in further risk reduction would be grossly disproportionate to the benefit gained. Demonstrating ALARP status—specifically locating the minimum ALARP point (LMALARP)—is crucial for owners, engineers of record, the public, insurers, lenders, and regulators.
Choices based on LMALARP can yield better decisions, enhance values of projects, and avoid overspending mitigative funds. However, LMALARP should not be seen as a static process, as it has to encompass various time horizons along the life of a project. The short-term ALARP may differ significantly from the long-term ALARP due to uncertainties, changing system conditions, and external factors, such as evolving land use in the vicinity of the facility.
This short article, based on the full paper by the same authors, showcases a high-level overview of how to quantitatively incorporate lifespan in the ALARP assessment when looking at a specific mitigation program, and/or to compare different remediation options. To do so, annualized quantitative risks must be evaluated for each mitigative alternative, as well as the cost of the various mitigative actions. For each time horizon, the result is the crossover point between remediation costs and risk reduction benefits, which represents the minimum theoretical ALARP point. Various considerations can then guide decision makers to select the point where the cost involved in reducing risk further would be disproportionate to the benefit gained.
This process has been applied to existing facilities and has shown how the optimum solution varies not only when the weighting of different consequences (environmental, financial, reputational, etc.) is shifted, but also when the lifespan of the structure is considered.
