Document: NRC Regulatory Guide
Document ID: a094549d-8685-4dad-b90f-c28c7d279a53
Document Type: regulatory_guide
Title: Geologic and Geotechnical Site Characterization Investigations for Nuclear Power Plants + HISTORY – HISTORY 08/2021 – DG-1392 , Proposed Revision 3 07/2014 – Periodic Review of Revision 2 – Reviewed with no issues identified 02/2001 – DG-1101 , Proposed Revision 2 (Rev. 3)
Source: NRC Regulatory Guide Division 1
Source URL: https://www.nrc.gov/docs/ML2119/ML21194A176.pdf
Revision Date: 2023-05
Chapter: 
Section ID: RG-1.132
CFR Part: 
CFR Title: 

Content:
Engineer Manual (EM) 1110-1-1804, “Geotechnical Investigations,” issued 2001 (Ref. 19). The top of the borehole should be protected by a suitable surface casing where needed. Below ground surface, the borehole should be protected by drilling mud or casing, as necessary, to prevent caving and disturbance of materials to be sampled. The use of drilling mud is preferred to prevent disturbance when obtaining undisturbed samples of coarse-grained soils. However, casing may be used if proper steps are taken to prevent disturbance of the soil being sampled and to prevent upward movement of soil into the casing. After use, each borehole should be grouted in accordance with State and local codes to prevent vertical movement of ground water through the borehole. Borehole elevation and depths into the ground should be measured to the nearest 3 centimeters (0.1 foot) and should be correlated with the elevation datum used for the site. Surveys of vertical deviation should be run in all boreholes that are used for in situ seismic tests (e.g., crosshole, downhole, compression wave-shear wave (P-S) suspension logging) and other tests where deviation potentially affects the data obtained. Boreholes with depths greater than about 30 meters (100 feet) should also be surveyed for deviation. Regulatory Position 4.5 details the information that should be presented in logs of subsurface investigations. Except where the borehole is being preserved for future use, all boreholes and exploratory excavations should be backfilled. Many States have requirements about backfilling boreholes. Therefore, appropriate State officials should be consulted. Borings that are preserved for future use should be protected with a short section of surface casing, capped, and identified. 4.5 Sampling Suitable samples of rock and soil should be obtained for identification and classification, mechanical analyses, and anticipated laboratory testing. The need for, number, and distribution of samples will depend