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:
lly sands or sands with deficiency of intermediate particle sizes may be unstable and develop piping when subject to seepage flow. Locate possible outcrop areas of sorted alluvial materials or terrace deposits. Examine seepage outcrop areas of slopes and riverbanks for piping. Area subsidence Area subsidence endangers long-term stability and performance of project. Locate areas of high ground water withdrawal, oil and gas fields, and subsurface mineral extraction (coal, solution mining, etc.) areas. Check project area for new wells or new mining activity. Are there any plans for new or increased recovery of subsurface water or mineral resources? Collapsing soils Determines need for removal of shallow foundation materials that would collapse upon wetting Determine how deposits were formed during geologic time and any collapse problems in area. Examine surface deposits for voids along eroded channels, especially in steep valleys eroded in fine-grained sedimentary formations. Were materials deposited by mud flows? DG-1392, Appendix A, Page A-4 APPENDIX A, Cont’d. GEOLOGIC FEATURE OR CONDITION INFLUENCE ON PROJECT OFFICE STUDIES FIELD OBSERVATIONS QUESTIONS TO ANSWER Locally lowered ground water May cause minor to large local and area settlements and result in flooding near rivers or open water and differential settlement of structures. Determine if heavy pumping from wells has occurred in project area; contact city and State agencies and U.S. Geological Survey. Obtain ground water levels in wells from owners and information on withdrawal rates and any planned increases. Observe condition of structures. Contact local water plant operators. Abnormally low pore water pressures (lower than anticipated from ground water levels) May indicate effective stresses are still increasing and may cause future slope instability in valley sites. Compare normal ground water levels with piezometric levels if data are available. Is a possible cause from past reduction in vertical