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:
availability, and population size, trends, and stability. Cooling Tower Drift Analyses Operation of cooling towers releases plumes of water vapor and droplets of condensed water to the atmosphere. The plume generally travels farther from taller natural draft cooling towers than it does from lower mechanical draft towers. Water circulating through cooling towers never comes in contact with the reactor core; therefore, radioactive contamination in drift is not a concern. However, drift can carry dissolved salts, biocides, and other constituents. Salts originate from makeup (source) water and become concentrated as water evaporates inside the tower. Brackish makeup water is of greater concern than fresh makeup water. Biocides are used to control microorganisms in the water. Aquatic habitat and species in water bodies near cooling towers can be exposed to drift, including salts and biocides. Drift deposition rarely results in a significant effect on aquatic habitats and biota, but analysts should consider conducting an analysis, especially in systems using saltwater for condenser cooling. DG-4023, Page 23 Transmission Line Water Crossings Building, operation, and maintenance of transmission lines and towers can affect aquatic habitat and species where transmission lines cross water bodies. Vehicles, equipment, and vegetation maintenance procedures could introduce chemical contaminants into the water body either directly or indirectly through runoff; installation, maintenance, and other activities also could increase sedimentation because of increased erosion or storm-water runoff. Analysts should evaluate conditions and potential effects from such activities where transmission lines or towers are near or cross water bodies. The analysis can be qualitative if quantitative assessments are not practicable. Often best management practices are relied upon instead of monitoring programs if no species or habitats warrant intensive monitoring. However, at the request of NMFS or