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:
ss in the crust? DG-1392, Appendix A, Page A-2 APPENDIX A, Cont’d. GEOLOGIC FEATURE OR CONDITION INFLUENCE ON PROJECT OFFICE STUDIES FIELD OBSERVATIONS QUESTIONS TO ANSWER Stress relief cracking and valley rebounding Valley walls may have cracking parallel to valley. Valley floors may have horizontal cracking. In some clay shales, stress relief from valley erosion or glacial action may not be complete. Review pertinent geologic literature and reports for the valley area. Check existing piezometer data for abnormally low levels in valley sides and foundation; compare with normal ground water levels outside valley. Examine wells and piezometers in valleys to determine if levels are lower than normal ground water regime (indicates valley rebound not complete). Sinkholes; karst topography Might affect stability of foundation. Major effect on location of structures and feasibility of potential site. Consider the local geology and stratigraphy from previous publications in site vicinity. Examine topographic maps (old and recent), LiDAR, and aerial photos (old and recent) for evidence of undrained depressions and disappearing streams. Consider the location and density of caves in the vicinity. Consider alternate rock dissolution processes such as epigenic and hypogenic systems. Locate depressions in the field and measure size depth and slopes. Differences in elevation between center and edges may be almost negligible or many feet. From local residents, attempt to date appearance of sinkhole. Consider the presence, size, and frequency of voids identified in core. Conduct field review of features identified in office studies. Are potentially soluble rock units present, such as limestone, dolomite, gypsum, anhydrite, or halite? Are undrained depressions present that cannot be explained by glaciation? How do the water table and deeper aquifers inform understanding about cavern formation? Is surface topography rough and irregular without apparent cause? Anhydrites or gypsum