Document: NRC Regulatory Guide
Document ID: e5306f4f-dc8c-4f60-a71c-af7ad4080384
Document Type: regulatory_guide
Title: Aquatic Environmental Studies for Nuclear Power Stations + HISTORY - HISTORY 12/2014 – DG-4023 -Proposed New Guide
Source: NRC Regulatory Guide Division 4
Source URL: https://www.nrc.gov/docs/ML1318/ML13186A085.pdf
Revision Date: 2023-06
Chapter: 
Section ID: RG-4.24
CFR Part: 
CFR Title: 

Content:
leading to an embayment or canal from which there is no escape route. Impingement typically affects fish and positively buoyant vegetation more than other biota, and some species are more susceptible than others to impingement. For example, a flat fish, such as a flounder species, typically has a high impingement survivability rate while a torpedo-shaped fish, such as an anchovy species, has a high DG-4023, Page 22 impingement mortality rate because the morphological differences in body shape profoundly affect the ability of an impinged fish to swim off a screen against the intake withdrawal current. Other factors affecting impingement survivability include fish length, burst speed, and overall health (e.g., diseased, previous injury) of the individual. Analysts base entrainment estimates on estimated abundance of organisms smaller than the mesh size of the intake screen, and, for purposes of analysis, they assume entrainment results in complete mortality. Impact analyses should discuss the potential effects on populations of migratory, benthic, demersal, pelagic, and floating species. Analysts need to take into account species-specific reproductive strategies and fecundities when estimating population trends for species likely to be affected by entrapment, impingement, or entrainment. Analysts need to base such reviews on building and operational plans and designs of the intake system as well as spatiotemporal patterns of species presence, distribution, and life histories. In addition to data collection for the proposed project, analysts should also use existing data from studies from co-located or nearby nuclear, fossil, or other units. Other sources of intake operation data may also be appropriate for analysis. Discharge Analyses Cooling water discharge can affect aquatic habitats and species in several ways. The distribution, abundance, and richness of species in or near the discharge area should be described, including identification of important habitat