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
CFR Part: 
CFR Title: 

Content:
the evaluation. Alternative interpretations of data and characteristics should be described when reasonable or when uncertainty in impacts exist. Characteristics should be substantially based on data obtained from a pre-application monitoring program and integrated with data from other studies conducted in the area and region (as applicable). DG-4026, Page 30 A statistical description should accompany all data. Average or median values, standard deviations or interquartile range, and the historical extremes should be described. Temporal trends in characteristics, including seasonal variation, should be identified and explained. Temporal variations of important characteristics (e.g., river flow rates) should be described in sufficient detail to provide accurate evaluation of impacts. For many characteristics, monthly variations may be sufficient, but daily or shorter increments should be provided when important for evaluating environmental impacts. Spatial variations of characteristics (e.g., aquifer hydraulic conductivity) should be described when important for evaluating environmental impacts (e.g., radionuclide transport in groundwater). All data for characteristics, including water use, should be adjusted to both present-day conditions and to those that may reasonably be expected to occur over the proposed period of the license. Where features of a proposed station (e.g., foundations, excavations, artificial lakes, and canals) modify the hydrologic conditions, the applicant should furnish sufficient site-specific detail to justify evaluation of the effects from building and operating the station on hydrologic characteristics, water use, and potential radionuclide transport. In addition, the applicant should describe reasonably foreseeable changes in the hydrologic environment (e.g., climate and land use). When a mathematical model is used to support the evaluation of hydrologic characteristics, the applicant should describe the conceptual basis for the model,