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:
evation of excavation equal to the depth of cut or to below the lowest potential failure zone of the slope.2 Borings should penetrate pervious strata below which ground water may influence stability.2 Pipelines Principal borings: This may vary depending on how well site conditions are understood from other plant site borings. For variable conditions, one per 30 m (100 ft) for buried pipelines; at least one boring for each footing for pipelines above ground. Principal borings: for buried pipelines, one of every three to penetrate sound rock or to dmax. Others to 5 times the pipe diameters below the elevation. For pipelines above ground, depths as for foundation structures.2 Tunnels Principal borings: one per 30 m (100 ft)2; may vary for rock tunnels, depending on rock type and characteristics and planned exploratory shafts or adits. Principal borings: one per 60 m (200 ft) to penetrate into sound rock or to dmax. Others to 5 times the tunnel diameter below the invert elevation.2,3 3 Also supplementary borings or soundings that are design dependent or necessary to define anomalies, critical conditions, etc. 4 Includes temporary cuts that would affect ultimate site safety. DG-1392, Appendix D, Page D-3 APPENDIX D, Cont’d. STRUCTURE SPACING OF BORINGS2 OR SOUNDINGS MINIMUM DEPTH OF PENETRATION Reservoirs, impoundments Principal borings: In addition to borings at the locations of dams or dikes, a number of borings should be used to investigate geologic conditions of the reservoir basin. The number and spacing of borings should vary, with the largest concentration near control structures and the coverage decreasing with distance upstream. Principal borings: at least one-fourth to penetrate that portion of the saturation zone that may influence seepage conditions or stability. Others to a depth of 7.5 m (25 ft) below reservoir bottom elevation.2 Sounding = An exploratory penetration below the ground surface used to measure or observe an in situ property of subsurface