Document: NRC Regulatory Guide
Document ID: 96baa826-d3bb-478b-8f38-e74500f6d433
Document Type: regulatory_guide
Title: 06/2009 (Rev. 2)
Source: NRC Regulatory Guide Division 1
Source URL: https://www.nrc.gov/docs/ML0911/ML091170109.pdf
Revision Date: 2023-06
Chapter: 
Section ID: RG-1.21
CFR Part: 
CFR Title: 

Content:
22 depth of the release, depth to the local water table, ground water flow directions, ground water flow rates, geochemical conditions, and other geochemical processes (e.g., geochemical retardation). Additionally, water usage such as ground water pumping from wells may create local ground water depression(s) that can alter the natural ground water flow. Sites should perform a basic site hydrogeological characterization, in advance of leaks or spills, to be prepared to evaluate potential leaks and spills. Sites with significant residual radioactivity that are likely to exceed the radiological criteria for unrestricted use at the time of decommissioning (e.g., as described in 10 CFR 20.1402) should perform more extensive evaluation. Initial assessments should be conducted with relatively simple site conceptual models using scoping surveys and/or bounding assumptions. The complexity of the models should increase as (1) more knowledge is obtained about the system under evaluation (e.g., source of leak, plume size, concentrations, radionuclides, site characteristics, presence of preferential flow pathways, etc) and as (2) the dose estimates rise above significant residual radioactivity levels (see definition in the glossary). Industry documents (Refs. 31, 33, and 34) that contain details of various industry practices can be used as part of a ground-water monitoring program. Sites with low-level spills or leaks generally do not require extensive site characterization and monitoring. Some basic steps in monitoring ground water contamination are summarized below: 1. Use the site conceptual model (as necessary) to assist in monitoring, evaluating, and reporting radioactive releases and radioactive discharges. 2. Collect empirical data by one or more of the following (as necessary): a. sample and analyze ground water from existing monitoring wells, and b. conduct additional hydrogeologic testing using existing wells (or new wells) if required. 3. Test the site conceptual