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Abstract

Closure assurance is a quickly developing area of both engineering, regulatory and investor focus. Given the high level of complexity involved, closure cost has historically been overlooked in the decision-making process with an overreliance on conceptual design. This can negatively impact the ultimate profitability of a project, though this impact may not be seen until later in the project life. Currently regulatory trends are moving in the direction of risk informed design, with requirements for at least feasibility level closure plans and supporting cost estimates which mature with the facility. The best opportunity to make a positive impact on the post-closure cost and risk profile is early in the life of the project. During the project life cycle there exist other major decision points where there is value in making the adjustments to the closure strategy. This must be supported by a risk-informed understanding of the short-term and long-term effects. As the site matures, and additional studies are completed, more information is made available, and therefore potential constraints may be better understood. This presents an opportunity (or requirement) to pivot strategy or methodology. These studies need to be used to update the site-specific risk assessment as an input to the closure plan. Anticipating the use of a site-specific risk assessment to revisit the closure plan allows for earlier trade-off studies to take advantage of emerging site trends and data. These studies make use of Qualitative assessments, taking advantage of the knowledge of experts. But this needs to be expanded upon. A more detailed analysis is required. Tying Qualitative risk analysis to a Quantitative Risk Review allows the plan to look more broadly at the impact of the decisions made in the design basis. Modeling the potential cost and schedule impact on the plan will also better inform the impact on a company’s bottom line as well as increase the accuracy of the closure estimate. The goal of these tools is a robust plan, and a more realistic closure estimate. Both items will ultimately work to derisk the project. This paper discusses how key risk assessment tools can be used to reduce post closure liability throughout the Life of Mine (LOM). These tools should offer the ability to trade off the benefits and drawbacks of decisions made as the mine plan evolves. Closure alternatives should be revised based on risks and opportunities as the operation matures, and more information is defined through studies and work with stakeholders. The motivation for developing this paper is from an observed need to increase dialogue on this topic for practitioners and closure stakeholders.