New Technical Bulletin - Environmental Consequence Classification

This Technical Bulletin, published in 2023, provides an update to the Environmental Consequence Classification (ECC) approach for mining dams.  Dam classification is based on the consequence of a potential failure and is an important aspect for establishing minimum dam design criteria and dam safety management requirements.  Dam classification considers the potential population at risk, and incremental impacts to loss of life, infrastructure and economic losses, and environmental and cultural losses.  The dam consequence classification is determined by whichever is the worst of the losses, based on incremental consequences of a hypothetical dam failure.

The ECC update is a systematic and evidence-based methodology to assess the environmental consequences that could result if a breach of a tailings facility would occur.  The consequence classification procedure is based on a hypothetical scenario and is intended to be used by dam owners, operators, regulators, and engineers involved in design, operation, and maintenance.  The updated methodology places an emphasis on semi-quantitative assessments requiring relevant training, experience, data, and verifiable facts.  The basis of the ECC system presented in the Technical Bulletin arises from the main mechanisms of environmental impact from a mining dam failure – to habitats.  These impacts are likely to be physical and, depending on the circumstances, may also be chemical, as could be the case with reactive tailings, sediments, sludges, and process-related water.  The ECC system is a high-level exercise and it therefore based on generalized principles of environmental science using three variable: Ecological Impact; Intrinsic Hazards of Contents, and; Duration of Impact. These variables are described and guidance on their intended manner of implementation is provided.  A detailed Glossary is provided.

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