Document: NRC Regulatory Guide
Document ID: f0baf50b-5bb7-4783-b2f9-9586e09c97e1
Document Type: regulatory_guide
Title: Preparation of Environmental Reports for Nuclear Power Stations + HISTORY - HISTORY 02/2017 – DG-4026 , Proposed Revision 3 09/2014 – Periodic Review of Revision 2 – Revise (Rev. 3)
Source: NRC Regulatory Guide Division 4
Source URL: https://www.nrc.gov/docs/ML1611/ML16116A068.pdf
Revision Date: 2023-06
Chapter: 
Section ID: RG-4.2
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CFR Title: 

Content:
mplementing NEPA at 40 CFR 1502.1, “Purpose,” and consistent with the definition of “Significantly,” at 40 CFR 1508.27. In assessing the significance of environmental impacts, the NRC uses the following definitions of significance levels codified in the footnotes to Table B-1 in Appendix B to Subpart A, “Environmental Effect of Renewing the Operating License of a Nuclear Power Plant,” of 10 CFR Part 51: • SMALL: For the issue, environmental effects are not detectable or are so minor that they will neither destabilize nor noticeably alter any important attribute of the resource. For the purposes of assessing radiological impacts, the Commission has concluded that those impacts that do not exceed permissible levels in the Commission’s regulations are small. • MODERATE: For the issue, environmental effects are sufficient to alter noticeably, but not to destabilize, important attributes of the resource. • LARGE: For the issue, environmental effects are clearly noticeable and are sufficient to destabilize important attributes of the resource. V. Mitigation of Adverse Effects Applicants are required to consider alternatives available for reducing or avoiding any adverse effects as described in 10 CFR 51.45(c). In addition, applicants should identify in their ERs any ongoing or planned mitigation for other permit-related activities and discuss the potential need for additional mitigation. Mitigation alternatives should be considered in proportion to the significance of the impact. In 40 CFR 1508.20, “Mitigation,” the Council on Environmental Quality identifies five types of mitigative actions: • avoiding the impact altogether by not taking a certain action or parts of an action; • minimizing impacts by limiting the degree or magnitude of the action and its implementation; • rectifying the impact by repairing, rehabilitating, or restoring the affected environment; • reducing or eliminating the impact over time by preservation and maintenance