Determining the Magnitude and Significance of Impacts

The last step in the impact assessment process is determining the magnitude and significance of impacts. This determination provides decision makers with the information needed to determine if a project should be approved or modified in some way that would make impacts acceptable.

This section provides guidance on determining the anticipated magnitude and significance of direct, indirect, and cumulative impacts. Consideration is given to the size of the area affected, status of resources, sensitivity of resources, and the anticipated departure from current conditions. For cumulative impacts, guidance is provided on determining other actions that may affect the resources of concern and add to cumulative impact. Guidance on identifying mitigation strategies to reduce these impacts is also provided.

Follow the links below for guidance on determining impact magnitude, determining impact significance, identifying uncertainties, and determining mitigation requirements.

• Determining the Magnitude of Impacts
  This section provides guidance on determining the magnitude of impacts associated with different project phases, including site characterization, project construction, operations, and decommissioning and reclamation.
• Determining the Significance of Impacts
  This section provides guidance on determining the significance of impacts. Significant impacts will be the focus of mitigation measures and possible adjustment of project features.
• Identifying Uncertainties
  This section provides guidance on identifying uncertainties. There are often many assumptions on which impact determinations are based. It is important to understand the level of uncertainty associated with the impact assessment. Uncertain impacts will be the focus of monitoring programs.
• Determining Mitigation Requirements
  This section provides guidance on determining the mitigation associated with different project phases including site characterization, project construction, operations, and decommissioning and reclamation. Mitigation generally focuses on significant impacts.