Revision as of 16:52, 19 November 2024

U.S. NUCLEAR REGULATORY COMMISSION

REGULATORY GUIDE 1.132, REVISION 3

Issue Date: December 2021 Technical Lead: Scott Stovall

GEOLOGIC AND GEOTECHNICAL SITE CHARACTERIZATION

INVESTIGATIONS FOR NUCLEAR POWER PLANTS

A. INTRODUCTION

Purpose

This regulatory guide (RG) provides guidance on field investiga tions for determining the geologic, geotechnical, geophysi cal, and hydrogeologic characteristics of a prospective site for engineering analysis and design of nuclear power plants.

Applicability

This RG applies to applicants and licensees subject to Title 10 of the Code of Federal Regulations

(10 CFR) Part 50, Domestic Licensing of Production and Utiliza tion Facilities (Ref. 1),

10 CFR Part 52, Licenses, Certifications, and Approvals for Nu clear Power Plants (Ref. 2), and

10 CFR Part 100, Reactor Site Criteria (Ref. 3).

Applicable Regulations

10 CFR Part 50, Appendix A, General Design Criteria for Nuclea r Power Plants, establishes minimum requirements for the principal design criteria for wate r-cooled nuclear power plants.

o General Design Criterion 2, Design Bases for Protection agains t Natural Phenomena, requires that structures important to safety be designed to wit hstand the effects of expected natural phenomena when combined with the effects of normal accident conditions without loss of capability to perform their safety function.

10 CFR Part 52, Licenses, Certifications, and Approvals for Nu clear Power Plants, governs the issuance of early site permits, standard design certifications, combined licenses, standard design approvals, and manufacturing licenses for nuclear power plants.

10 CFR Part 100, Reactor Site Criteria, requires the U.S. Nuc lear Regulatory Commission (NRC) to consider population dens ity; use of the site environs, including proximity to manmade hazards; and the physical characteristics of the site, including seismology, meteorology, geology, and hydrology, in determining the acceptability of a site for a nuclear power reactor.

Written suggestions regarding this guide or development of new guides may be submitted through the NRCs public Web site in the NRC Library at https://nrcweb.nrc.gov/reading-rm/doc-collections/reg-guides/, under Document Collections, in Regulatory Guides, at https://nrcweb.nrc.gov/reading-rm/doc-collections/reg-guides/contactus.html.

Electronic copies of this RG, p revious versions of RGs, and other recently issued guides are also available through the NRCs public Web site in the NRC Library at https://nrcweb.nrc.gov/reading-rm/doc-collections/reg-guides/, under Document Collections, in Regulatory Guides. This RG is also available th rough the NRCs Agencywide Documents Access and Management System (ADAMS) at http://www.nrc.gov/reading-rm/adams.html, under ADAMS Accession Number (No.)

ML21298A054. The regulatory analysis may be found in ADAMS under Accession No. ML21194A177.

o 10 CFR 100 Subpart B, Evaluation Factors for Stationary Power Reactor Site Applications on or after January 10, 1997," provides the requirements for th e factors to be considered.

Specific to this RG are 10 CFR 100.20(c), 100.21(d), and 100.23 that establish the requirements for conducting site i nvestigations which include seismology, geology, meteorology, and hydrology.

Related Guidance

NUREG-0800, Standard Review Plan for the Review of Safety Anal ysis Reports for Nuclear Power Plants: LWR Edition (Ref. 4), provides guidance to the N RC staff in performing safety reviews under 10 CFR Part 50 and 10 CFR Part 52. Chapter 2, Si te Characteristics and Site Parameters, gives general review guidance related to site characteristics and site parameters, together with site-related design parameters and design charact eristics, as applicable.

RG 1.29, Seismic Design Classification for Nuclear Power Plant s (Ref. 5), identifies the structures, systems, and component s (SSCs) that should be desig ned to withstand the effects of the safe shutdown earthquake and remain functional.

RG 1.70, Standard Format and Content of Safety Analysis Report s for Nuclear Power Plants:

LWR Edition (Ref. 6), and RG 1.2 06, Applications for Nuclear Power Plants (Ref. 7), provide general guidance on the types of information about the hydrolog ic setting and assessments of flooding hazards that a license application for a light-water r eactor (LWR) power plant should include.

RG 1.138, Laboratory Investigations of Soils and Rocks for Eng ineering Analysis and Design of Nuclear Power Plants (Ref. 8), provides guidance on sampling, storage, and laboratory investigations of the properties of soils for engineering analy sis and design of nuclear power plants.

RG1.201, Guidelines for Categorizing Structures, Systems, and Components in Nuclear Power Plants According to Their Safety Significance (Ref. 9), describes a risk-informed process for categorizing SSCs according to their safety significance that can remove SSCs of low safety significance from the scope of certain identified special treat ment requirements.

RG 4.7, General Site Suitability Criteria for Nuclear Power St ations (Ref. 10), assists applicants in the initial stage of selecting potential sites fo r a nuclear power station. The safety issues discussed include geological, seismic, hydrological, and meteorological characteristics of proposed sites as they relate to protecting the general public from the potential hazards of serious accidents.

Purpose of Regulatory Guides

The NRC issues RGs to describe methods that are acceptable to the staff for implementing specific parts of the agencys regulations, to explain techniqu es that the staff uses in evaluating specific issues or postulated events, and to describe information that the staff needs in its review of applications for permits and licenses. Regulatory guides are not NRC regulations and compliance with them is not required. Methods and solutions that differ from those set fort h in RGs are acceptable if supported by a basis for the issuance or continuance of a permit or license by the Commission.

RG 1.132, Page 2 Paperwork Reduction Act

This RG provides voluntary guidance for implementing the mandat ory information collections in

10 CFR Parts 50, 52, and 100 that are subject to the Paperwork Reduction Act of 1995 (44 U.S.C. 3501 et. seq.). These information collections were approved by the O ffice of Management and Budget (OMB),

approval numbers 3150-0011, 3150- 0151, and 3150-0093 respective ly. Send comments regarding this information collection to the FOIA, Library, and Information Co llections Branch, (T6-A10M), U.S.

Nuclear Regulatory Commission, Washington, DC 20555-0001, or by e-mail to Infocollects.Resource@nrc.gov, and to the OMB reviewer at: OMB Office of Information and Reg ulatory Affairs (3150-0011, 3150-0151, 3150-0093), Attn: Desk Officer f or the Nuclear Regulatory Commission,

725 17th Street, NW Washington, DC 20503; e- mail: oira_submission@omb.eop.gov .

Public Protection Notification

The NRC may not conduct or sponsor , and a person is not require d to respond to, a collection of information unless the document re questing or requiring the col lection displays a currently valid OMB

control number.

RG 1.132, Page 3 TABLE OF CONTENTS

A. INTRODUCTION

.................................................. ............................................................... .............. 1 Purpose ....................................................... ............................................................... ................................ 1 Applicability ................................................. ............................................................... ............................. 1 Applicable Regulations ........................................ ............................................................... ...................... 1 Related Guidance .............................................. ............................................................... ......................... 2 Purpose of Regulatory Guides .................................. ............................................................... ................. 2 Paperwork Reduction Act ....................................... ............................................................... ................... 3 Public Protection Notification ................................ ............................................................... .................... 3

B. DISCUSSION

.................................................... ............................................................... .................. 6 Reason for Revision ........................................... ............................................................... ........................ 6 Background .................................................... ............................................................... ............................ 6 Consideration of International Standards ...................... ............................................................... ............. 6 Documents Discussed in Staff Regulatory Guidance .............. ............................................................... .. 7 C. STAFF REGULATORY GUIDANCE ..................................... .......................................................... 8

1. General Requirements .......................................... ............................................................... .............. 8

2. Types of Data to Be Acquired .................................. ............................................................... .......... 8

2.1 Geologic Characteristics .................................. ............................................................... ................ 8

2.2 Engineering Properties of Soils and Rocks ................. ............................................................... ..... 9

2.3 Ground Water Conditions ................................... ............................................................... ............. 9

2.4 Human-Induced Conditions .................................. ............................................................... ........... 9

2.5 Cultural and Environmental Considerations ................. ............................................................... ... 9

2.6 Related Considerations .................................... ............................................................... ................ 9

3. Evaluation of Previously Pub lished Information, Field Reconn aissance, and Preliminary Assessment of Site Suitability ........................................... ............................................................... .......................... 10

3.1 General ................................................... ............................................................... ........................ 10

3.2 Evaluation of Previously Published Information ............ .............................................................. 10

3.3 Field Reconnaissance ...................................... ............................................................... ............... 11

3.4 Preliminary Assessment of Site Suitability ................ ............................................................... .... 11

4. Detailed Site Investigations ............................... ............................................................... .................. 11

4.1 General ................................................... ............................................................... ........................ 11

4.2 Surface Investigations .................................... ............................................................... ................ 12

4.3 Subsurface Investigations ................................. ............................................................... ............. 13

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4.4 Borings and Exploratory Excavations ....................... ............................................................... ..... 14

4.5 Sampling .................................................. ............................................................... ...................... 15

4.6 Borrow Materials .......................................... ............................................................... ................. 17

4.7 Materials Unsuitable for Foundations ...................... ............................................................... ...... 18

4.8 Transportation and Storage of Samples ..................... ............................................................... .... 18

4.9 In Situ Testing ........................................... ............................................................... ..................... 18

4.10 Geophysical Investigations ............................... ............................................................... ........... 19

4.11 Logs of Subsurface Investigations ........................ ............................................................... ....... 21

5. Ground Water Investigations ................................... ............................................................... ........ 21

6. Construction Mapping .......................................... ............................................................... ........... 22

7. Support Functions ............................................. ............................................................... ............... 23

7.1 Surveying, Mapping, and Development of the GIS Database ... ................................................... 23

7.2 Records, Sample Retention, and Quality Assurance .......... ........................................................... 23

D. IMPLEMENTATION

................................................ ............................................................... ........ 25 REFERENCES .................................................... ............................................................... ........................ 26 APPENDIX A .................................................... ............................................................... ........................ A-1 SPECIAL GEOLOGIC FEATURES AND CONDITIONS CONSIDERED IN OFFICE S TUDIES AND

FIELD OBSERVATIONS (adapted from EM 1110-1-1804, U.S. ARMY CORP S OF ENGINEERS,

2001) ........................................................ ............................................................... .................................. A-1 APPENDIX B .................................................... ............................................................... ........................ B-1 SOURCES OF GEOLOGIC INFORMATI ON (adapted from EM 1110-1-1804, U .S. ARMY CORPS OF

ENGINEERS, 2001) .............................................. ............................................................... .................... B-1 APPENDIX C .................................................... ............................................................... ........................ C-1 METHODS OF SUBSURFACE EXPLORATION ............................. .................................................... C-1 APPENDIX D .................................................... ............................................................... ........................ D-1 SPACING AND DEPTH OF SUBSURFACE EXPLORATIONS FOR FOUNDATIONS OF SAFETY-

RELATED ENGINEERED STRUCTURES ................................. ........................................................... D-1 APPENDIX E .................................................... ............................................................... ........................ E-1 APPLICATIONS OF SELECTED GEOPHYSICAL METHODS FOR DETERMINATION OF

ENGINEERING PARAMETERS ........................................ ............................................................... ..... E-1 APPENDIX F..................................................... ............................................................... ........................ F-1 IN SITU TESTING METHODS........................................ ............................................................... ........ F-1 APPENDIX G .................................................... ............................................................... ........................ G-1 INSTRUMENTS FOR MEASURING GROUND WATER PRESSURE ............... ................................ G-1

RG 1.132, Page 5

B. DISCUSSION

Reason for Revision

This revision of the guide (Revision 3) captures updates to th e U.S. Army Corps of Engineers Engineer Manuals that provide guidance for the procedures in th is RG. The manual changes are primarily modest updating of geophysical methods used for site exploratio n and characterization. In addition, RG 1.165, Identification and Characterization of Seismic Sourc es and Determination of Safe Shutdown Earthquake Ground Motion, was withdrawn in 2010 and replaced by RG 1.208, A Performance-Based Approach to Define the Sites-Specific Earthquake Ground Motion (Ref. 11).

Background

Site investigations are needed to define site-specific geologic, geotechnical, geophysical, and hydrogeologic characteristics to the degree necessary for understanding surface and subsurface conditions and identifying potential geologic hazards that might affect the site. Investigations for geologic hazards such as fault deformation, landslides, cavernous rocks (surface or subsurface karst), ground subsidence, soil liquefaction, and any other natural or manmade external ha zards are of particular importance. The density of data collected will depend on variability of the soil and rock materials and the safety-related importance of structures planned for a particular site location. Well-conducted site investigations can save time and money by reducing prob lems in licensing and construction.

The site investigations described in this RG are closely relate d to those in RG 1.208. The main purpose of that RG is to define the site-specific, performance-based ground motion response spectrum in order to determine the safe-shutdown earthquake ground motion b ased on information derived from geologic, geotechnical, geophys ical, and seismic investigations . Appendix C, Investigations to Characterize Site Geology, Seismology and Geophysics, to RG 1. 208 gives guidance on the appropriate information needed to identify and characterize seismic source zone parameters and assess the potential for surface fault rupture and associated deformation at the sit e for use in probabilistic seismic hazard analyses.

It is worthwhile to point out that good site investigations hav e the added benefit of saving time and money by reducing prob lems in licensing and construction. A case study report on geotechnical investigations by the National Research Council (R ef. 12), for example, concludes that additional geotechnical information would almost always save ti me and costs.

Consideration of International Standards

The International Atomic Energy Agency (IAEA) works with member states and other partners to promote the safe, secure, and peaceful use of nuclear technologies. The IAEA develops Safety Requirements and Safety Guides for protecting people and the en vironment from harmful effects of ionizing radiation. This system of safety fundamentals, safety requirements, safety guides, and other relevant reports reflects an international perspective on what constitutes a high level of safety. To inform its development of this RG, the NRC considered IAEA Safety Requ irements and Safety Guides under the Commissions International Policy Statement (Ref. 13) and Manag ement Directive 6.6, Regulatory Guides (Ref. 14).

The NRC staff considered the following IAEA safety requirements and guides in the development/update of this RG:

RG 1.132, Page 6

IAEA Safety Standards Series No. NS-G-3.6, Geotechnical Aspect s of Site Evaluation and Foundations for Nuclear Power Plants, issued 2005 (Ref. 15)

IAEA Specific Safety Guide No. SSG-9, Seismic Hazards in Site Evaluation for Nuclear Installations, issued 2010 (Ref. 16)

Documents Discussed in Staff Regulatory Guidance

This RG endorses the use of one or more codes or standards deve loped by external organizations, and other third-party guidance documents. These codes, standards, and third-party guidance documents may contain references to other codes, standards or third party guidance documents (secondary references). If a secondary reference has itself been incorporated by reference into NRC regulations as a requirement, then licensees and applicants must comply with tha t standard as set forth in the regulation. If the secondary reference has been endorsed in a RG as an acceptable approach for meeting an NRC

requirement, then the standard constitutes a method acceptable to the NRC staff for meeting that regulatory requirement as described in the specific RG. If the secondary reference has neither been incorporated by reference into NRC regulations nor endorsed in a RG, then the secondary reference is neither a legally-binding requirement nor a generic NRC approved acceptable approach for meeting an NRC requirement. However, licensees and applicants may consider and use the information in the secondary reference, if appropriately justified, consistent with current regulatory practice, and consistent with applicable NRC requirements.

RG 1.132, Page 7 C. STAFF REGULATORY GUIDANCE

1. General Requirements

A well-planned program of site exploration should be conducted using a phased approach that progresses from a literature search and reconnaissance investig ations to detailed site investigations, construction mapping, and final as-built data compilation to provide a strong basis for site suitability determination and foundation d esign and construction. The actual site investigation program should be tailored to the specific conditions of the site and based on so und professional judgment. The site investigation program should be f lexible and modified when need ed, as the site investigation proceeds based on the provisions and criteria of the project.

Site investigations for nuclear power plants should be adequate in terms of thoroughness, suitability of methods used, quality of execution of the work, and documentation to permit an accurate determination of the geologic and geotechnical conditions that affect the design, performance, and safety of the plant. The investigati ons should provide information nee ded to perform engineering analyses and design the plant with reasonable assurance that the geologic an d geotechnical conditions and associated uncertainties have been appropriately determined and considered .

This guide considers techniques available at the date of issuan ce. As science advances, useful procedures, standards, and equipment should be included as they are developed and accepted by the profession.

2. Types of Data to Be Acquired

2.1 Geologic Characteristics

Geologic characteristics include, but are not limited to, the f ollowing:

Lithology and other distinguishing features of rock units at th e surface and in the subsurface.

Depositional and tectonic deformation features include bedding planes, faults and shear zones, joints, and foliation surfaces, t he orientations of which are needed for characterization of the features.

Nature, degree, and extent of weathering at the surface and in the shallow subsurface.

Weathering-related characteristics include soil type, presence of expanding soils, and karst features that are active or relict (sinkholes and dolines, disa ppearing streams, caverns, and subsurface voids not detectable at the surface).

Potential for soil liquefaction and evidence for paleoliquefaction.

Natural hazards that include seismic events, surficial and blin d faults, landslide potential, nontectonic deformation, susceptibility to erosion, sea level r ise, flooding, tsunami, seiche, and storm wave action.

Appendix A to this guide lists special geologic features and co nditions that might need to be investigated during site characterization, either as office-bas ed or field studies.

RG 1.132, Page 8

2.2 Engineering Properties of Soils and Rocks

Engineering properties of soil and rock include static and dynamic properties such as density, moisture content, strength para meters, elasticity, plasticity, hydraulic conductivities, rock joint characteristics, seismic velocities, and degradation properties associated with strain. Some of these properties can be measured in situ, and those measurements, tog ether with sample collection methods, are discussed in this guide. Determination of these and other engin eering properties also requires laboratory testing, which is described in RG 1.138.

2.3 Ground Water Conditions

Ground water conditions that can i mpact the engineering design, performance, and durability of the foundations and structures should be determined. These cond itions include ground water levels, chemical properties of ground wa ter, thickness and extent of aq uifers and confining beds, ground water flow patterns, recharge areas, discharge points and transmissivities, and storage coefficients.

2.4 Human-Induced Conditions

Existing infrastructure should be located, including dams or re servoirs that might cause a flooding hazard or induce loading effects at the site. Past or ongoing a ctivities, such as mining, oil and gas production to include hydrofracking, and other fluid extraction or injection activities, should be assessed and documented. The presence of f ormer or current industrial sites, underground storage tanks, abandoned well casings, buried f oundations, conduits, pipes, su mps, or landfills should be identified. The potential for hazardous, toxic, or radioactive waste should also be investigated and documented.

2.5 Cultural and Environmental Considerations

Assessment for cultural resources, such as archaeological sites and artifacts, must comply with the Archaeological Resources Protection Act of 1979 and the Nat ive American Graves Protection and Repatriation Act of 1990.

The National Historic Preservation Act (36 CFR Part 800, Prote ction of Historic Properties)

must be considered if the site investigation will affect historic property. Under that condition, the Section 106 review process must be followed.

Aspects of the Clean Water Act (33 U.S.C. 1344) must be taken i nto account. Placement of fill in wetlands is regulated at the national level, and State and loca l wetland protection laws may also apply.

The Corps of Engineers Wetlands Delineation Manual (Ref. 17) gives guidance on identifying and delineating wetlands. Information on applications for Section 4 04 permits for modifying wetlands can be obtained from District Offices of the Army Corps of Engineers.

2.6 Related Considerations

RG 1.208 provides guidance on seism icity and related seismic data and historical records, together with guidance on determin ation of vibratory ground mot ion resulting from earthquakes. Many of the investigations listed in RG 1.208 could and should be coord inated with the site investigations described in this guide and conduc ted at the same time for greater efficiency. Appendix C to RG 1.208 should be used as guidance for investigating tectonic and nonte ctonic surface deformation.

RG 1.132, Page 9

3. Evaluation of Previously Published Information, Field Recon naissance, and Preliminary Assessment of Site Suitability

3.1 General

Establishing the geologic characteristics and engineering prope rties of a site is an iterative process during which successive phases of investigation produce increasingly detailed data. Therefore, it is important to have a proper sy stem for recording the data and gaining a three-dimensional spatial understanding of site conditions.

A geographic information system (GIS) database is an efficient way to collect and present spatial data. A well-planned database system for compiling pertinent data is important for data retrieval and analysis and is a part of the quality assurance requirements fo r a project (see Regulatory Position 7.2).

RG 1.208 indicates that geologic, seismic, and geophysical inve stigations are to be performed to develop an up-to-date, site-specific, geoscience database that supports the site characterization efforts.

3.2 Evaluation of Previously Published Information

The first step in the site investigation process is to acquire and evaluate existing data related to geologic characteristics and engineering properties of the site . Information about regional geology should be considered to assist with unde rstanding rock and soil proper ties of the site in the proper regional context. Reconnaissance-level inv estigations can start with review of published reports, data, and existing maps illustrating topography, geology, hydrology, previous land use and construction, and infrastructure.

Study of aerial photographs, satellite imagery, light detection and ranging (LiDAR) surveys, and other remote sensing imagery can be used to complement this informati on. If available, regional strain rates measured using the Global Positioning System (GPS) (Ref. 18) sh ould be collected to correlate with strain rates obtained from geologic data and other data sets.

Possible sources of current and historical documentary informat ion could include the following:

geology and engineering departme nts of State and local universi ties;

county governments, many of which have GIS data of various kinds available;

State government agencies, such as State geological surveys;

U.S. government agencies, such as the U.S. Geological Survey, the Bureau of Reclamation, and the U.S. Army Corps of Engineers;

newspaper records of earthquak es, floods, landslides, and other natural events of significance;

interviews with local inhabitants and knowledgeable professionals; and

reputable and relevant online documents.

Appendix B to this guide lists additional potential sources for maps, imagery, and other pertinent geologic data.

For license applications for a site near an existing nuclear po wer plant with a similar geologic setting, documents related to the site investigation for the existing plant could provide valuable information. Plans held by utilities should be consulted to loc ate services such as water, gas, electric, and

RG 1.132, Page 10

communication lines. Locations of power lines, pipelines, and a ccess routes should be established.

Mining records should be consulted to determine locations of ab andoned adits, shafts, mining works, benches, and tailings ponds and embankments. Oil, gas, and water well records and oil and gas field exploration data can provide valuable subsurface information. Historical and archaeological sites should be identified to document locations of potential cultural resou rces.

3.3 Field Reconnaissance

In addition to evaluating and do cumenting previously published information, it is necessary to perform preliminary field reconnaissance of the site and the su rrounding area. This step enables an assessment of field data related to site conditions and regiona l geology and establishes the basis for a detailed site investigation plan. Appendix A to this guide list s special geologic features and conditions that should be considered. In addition to site-specific conditions, areas containing potential borrow sources, quarry sites, and water impoundments should be investi gated.

The team performing the reconnaissance should include, as a min imum, a geologist and a geotechnical engineer and could al so include other specialists (e.g., an engineering geologist or geophysicist). Appropriate topogr aphic and geologic maps should be used during the field reconnaissance, if available, to locate features of potential i nterest. A GPS unit would be advantageous for recording locations in the field, as noted in more detail in Re gulatory Position 7.1.

3.4 Preliminary Assessment of Site Suitability

After completion of the field r econnaissance investigations and in conjunction with the information in the developed d atabase, a preliminary determination of site suitability should be made to identify information gaps and potential hazards to help formulate the plan for the detailed site investigation stage. The presence of features or characteristic s that could potentially result in deleterious ground displacement (e.g., fault displacement, subsurface disso lution, and settlement or subsidence),

swelling soils and shales, or other natural hazards (e.g., unde rground cavities, landslides, or periodic flooding) could make plant design difficult and require additio nal extensive investigations to assess properly. For sites where such features and characteristics exist, it might be advantageous to search for a more suitable site.

4. Detailed Site Investigations

4.1 General

The detailed site investigation phase acquires all geologic and material property data needed for the engineering analyses, design, and construction of a plant, including the related critical structures. A

multidisciplinary team is needed to accomplish the different ta sks during this phase. Subsequent site investigations might be needed i f additional data are required to supplement a gap in the knowledge associated with the geologic characteristics and subsurface material properties at the site.

The engineering properties of rock and soil can be determined t hrough drilling and sampling, in situ testing, field geophysical measurements, and laboratory testing. This guide describes in situ testing and field geophysical measurements, as well as drilling and sampling procedures used to gather samples for laboratory testing. For guidance on laboratory testing proc edures, refer to RG 1.138.

All pertinent conclusions should be presented and linked directly to the information that provides the bases for the conclusions. Site-specific information to be developed and analyzed should include, but not be limited to, the following:

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(1) Topographic and geologic maps. T he geologic maps should show ro ck types and locations of tectonic and nontectonic geologic features, as well as points w here field samples were collected for laboratory analysis (e.g., for radiometric age dating and d etermination of material properties).

(2) Plot plans showing the locations of major anticipated engineere d structures and points at which site investigation tests were conducted and data or measurement s were collected.

(3) Boring logs and geologic logs of exploratory trenches and excav ations.

(4) Geologic profiles illustrating subsurface geology and excavation limits for engineered structures.

(5) Geophysical information such as survey lines, seismic survey time-distance plots, resistivity curves, seismic reflection and refraction plots, seismic wave v elocity profiles, surface wave dispersion plots, and borehole loggings.

Locations of all boreholes, gr ound water observation wells and piezometers, in situ tests, trenches, exploration pits, and ge ophysical measurements should be surveyed in both plan and elevation.

This three-dimensional information should be entered into a GIS database. Suitable cross sections, maps, and plans should be prepared to facilitate visualization of the geologic information. Regulatory Position 7.1 gives further details.

Detailed site investigations shoul d use applicable industrial standards for specific techniques, methods, and procedures. Regulat ory Position 7.2 provides quali ty assurance requirements. Use of investigative and sampling techniques other than those discusse d in this guide is acceptable when it can be shown that the alternative techniques yield satisfactory results.

4.2 Surface Investigations

Detailed surface geologic and geotechnical engineering investigations should be conducted over the site area to assess all pertinent soil and rock characteristics. The definition of site area, as specified in RG 1.208, is that area within a radius of 8 kilometers (5 miles ) of the site. Appendix A to this guide lists some of the special geologic features and conditions to be cons idered.

The initial step in conducting de tailed surface investigations for a site is to prepare three-dimensional topographic maps at a scale suitable for plot ting the geologic features and characteristics and showing features in the surrounding area th at are related, for example, to borrow areas, quarries, and access roads. Aerial photographs and stereoscopic image pairs, other remote sensing imagery (e.g., satellite imagery and LiDAR), and the results of geophysical surveys are valuable for regional analysis, determination of fault and fracture patterns , location of potential nontectonic surficial features related to possible subsurface dissolution, and other features of interest.

Depending on the site, detailed mapping of the following site c haracteristics and associated features should be considered dur ing conduct of the surface investigations:

topography (including geomorphic features, lineaments, paleo-la ndslides, closed depressions, river terraces, and alluvial and glacial deposits),

hydrology (including rivers, str eams, lakes, wetlands, local drainage channels, springs, and sinkholes),

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geology (including outcrops; tectonic features such as faults, shear zones, and zones exhibiting strong fracturing or alteration; nontectonic features such as s urficial indicators of subsurface dissolution; rock unit contacts), and

engineering geology (including soil conditions and soil types, chemically or physically weathered zones and horizons, and areas exhibiting material properties conducive to soil liquefaction).

All maps produced should include s tandard map labels such as sc ales, a north arrow, map projection information, title, and citation of original data or data sources.

4.3 Subsurface Investigations

Subsurface investigations expand knowledge of the three-dimensional distribution of geologic features and characteristics and geotechnical engineering properties at the site and in borrow areas.

Subsurface investigations also provide information on potential natural hazards such as nontectonic underground features (e.g., disso lution cavities), hidden faults, soft zones, or geologic contacts. The investigations should use a vari ety of appropriate methods, including borings and excavations augmented by geophysical measurements and geophysical surveys. Appendix C to this guide tabulates methods of conducting subsurface investigations. Techniques employing diff erent measurement approaches should be used to determine geologic cond itions and geotechnical engineer ing properties to account for uncertainties in the data and to cross-check the conformability and reasonableness of the data obtained during site investigations. An adequate number of tests for eac h method should be performed to quantify the mean and variability of pertinent site parameters and geote chnical engineering properties of subsurface materials.

Locations and depths of borings , excavations, and geophysical measurements should be selected such that site-specific geology and foundation support conditions are sufficiently defined in both lateral extent and depth to permit the suitable design of all necessary excavations and engineered structures. The information acquired should also support development of geologi c cross sections and subsurface profiles that contain field testing data (e.g., N-values, cone penetrati on test values, and seismic wave velocities)

constructed through the foundations of safety-related structure s and other important structures at the site.

Subsurface investigations for less critical foundations of power plants should be carried out at a spacing and depth of penetration necessary to define the geologic conditions and geotechnical engineering properties of the subsurface materials. Subsurface investigatio ns in areas remote from plant foundations might be needed to complete the geologic description and confir m the geologic conditions of the site.

Subsurface investigations for materials to be used for backfill , improvement of subsurface conditions, or ground water contro l under the foundations of safety-related structures, including granular and nongranular materials, should be performed to confirm that stability and durability requirements will be met and to validate the material properties to be used for design and analysis.

Boreholes are one effective way to obtain detailed information on subsurface geologic conditions and the engineering properties of subsurface materials. Core and other samples recovered from boreholes, geophysical and borehole surveys, and other in situ borehole te sts can provide important subsurface information. Test pits, trenches, and exploratory shafts can be used to complement the borehole exploration results; provide add itional detailed information on rock and soil conditions, faulting, and density of in situ materials; and obtain high-quality undisturb ed samples.

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4.4 Borings and Exploratory Excavations

Field operations conducted at the site should be supervised by experienced personnel familiar with site operations, and systematic standards of practice should be followed. Procedures and equipment used to carry out field operations, including necessary calibrations, and all conditions encountered in various phases of the investigations should be documented. Pers onnel who are experienced and thoroughly familiar with sampli ng and testing procedures should inspect and document sampling results and transfer samples from the field to storage or laboratory facilities with a properly executed chain-of-custody record.

The complexity of geologic cond itions and foundation requirements should be considered in choosing the distribution, numbe r, and depth of borings and oth er excavations at the site. The investigative efforts should be greatest at the locations of sa fety-related structures and might vary in density and scope in other areas according to spatial and geolo gic relationships to the specific site.

Excavation trenches across faults or shear zones might be required to determine the age of last movement on these tectonic features to better assess the potential impac t of the features on site safety. At least one continuously sampled boring sh ould be drilled for each safety-related structure, and the boring should extend to a depth sufficient for defining the geologic and hydr ogeologic characteristics of the subsurface materials that will influence the stability and suitability of the safety-related structures.

NUREG/CR-5738, Field Investigations for Foundations of Nuclear Power Plants, issued November 1999, describes procedures for borings and exploratory excavations. Appendix C to this guide reproduces a table from NUREG/CR-5738 showing widely used techn iques for subsurface investigations and describing the applicability and limitations of the techniq ues. Appendix D to this RG contains general guidelines for spacing and depth of borings.

4.4.1 Spacing and Depth

Spacing, depth, and the number of borings for safety-related st ructures should be chosen and justified based on foundation requirements and the complexity of anticipated subsurface conditions.

Appendix D provides general guidelines on this topic. Spacing o f borings for a deeply embedded structure with smaller foundation dimensi ons should be reduced, and addit ional boreholes should be located outside the foundation footprint to obtain detailed geologic an d geotechnical information about the surrounding materials. This information will provide pertinent data for the analysis of soil-structure interactions and determination of lateral earth pressures.

Uniform subsurface conditions permit the maximum spacing of bor ings in a regular grid for adequate definition of those conditions. Subsurface conditions can be considered uniform if the geologic characteristics and features to be defined can be correlated fr om one boring location to the next with relatively smooth variations in thicknesses and properties of t he geologic units. An occasional anomaly or a limited number of unexpected lateral variations might occur.

If subsurface conditions are not uniform, a regular grid might not provide the most effective distribution of boreholes. Soil deposits or rock units could be encountered in which the geologic characteristics are so complex that only the major rock unit co ntacts are correlated. Material types and properties might also vary within major geologic units in an ap parently random manner from one boring to another. The number and distribution of borings needed for s uch nonuniform conditio ns are determined by the degree of resolution needed to define geotechnical prope rties required for engineering design. In locations with sedimentary rock formations, it will be helpful to understand the environment of deposition for the various geologic units at the site in order to understa nd lateral and vertical variations within the units. The goal of the investiga tions is to define the thicknesses of the different subsurface materials,

RG 1.132, Page 14 degree of lateral and vertical variability of the materials, an d the range of geologic characteristics and geotechnical properties of the materials that underlie all majo r structures.

If there is evidence suggesting the presence of local adverse a nomalies or discontinuities in the subsurface (e.g., cavities, sinkholes, fissures, faults, brecciated zones, lenses, or pockets of unsuitable material), then supplementary borings at a spacing small enough to detect and delineate these features are needed. At locations with limestone, dolostone, and anhydrite, the size, frequency, and depth of voids or caverns should be considered because different mechanisms or di ssolution processes may exist. It is important that the supplementary borings penetrate all potentia lly detrimental zones or extend to depths below which presence of these zones would not influence stability of the structures. Geophysical investigations should be used t ogether with the borings to bett er characterize subsurface conditions at the site.

4.4.2 Drilling Procedures

Drilling methods and procedures s hould be compatible with sampl ing requirements and the methods of sample recovery. Many of the methods are discussed i n detail in U.S. Army Corps of Engineers Engineer Manual (EM) 1110-1-1804, Geotechnical Inves tigations, issued 2001 (Ref. 19).

The top of the borehole should be protected by a suitable surfa ce casing where needed. Below ground surface, the borehole should be p rotected 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 p revent upward movement of soil into the casing. After use, each borehole should be grouted in accordanc e with State and local codes to prevent vertical movement of ground water through the borehole.

Borehole elevation and depths i nto the ground should be measure d to the nearest 3 centimeters

(0.1 foot) and should be correla ted with the elevation datum us ed for the site. Surveys of vertical deviation should be run in all boreholes that are used for in s itu 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 a bout 30 meters (100 feet) should also be surveyed for deviation. Regulatory Position 4.5 details the inf ormation 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. M any States have requirements about backfilling boreholes. Therefore, appropriate State officials shoul d be consulted. Borings that are preserved for future use should be protected with a short section of surface casing, capped, and i dentified.

4.5 Sampling

Suitable samples of rock and so il should be obtained for identification and classification, mechanical analyses, and anticipated laboratory testing. The need for, number, and distribution of samples will depend on testing requirements and the variability of the field conditions. A sufficient number of samples should be collected to meet the needs of labo ratory testing, especially when undisturbed samples are required. It is important to obtain goo d-quality undisturbed samples for cyclic load testing. In general, soil and rock samples should be colle cted from more than one principal boring within the foundation support zone of each safety-related struc ture.

Sampling of soil and rock in boreholes should include, as a min imum, recovery of samples at regular intervals and where changes in materials occur. One or more borings for each major structure

RG 1.132, Page 15 should be continuously sampled. P roper sampling methods should be used to collect soil samples.

Standard penetration and cone penetration tests should be used with sufficient coverage to define the soil profile and variations in soil conditions. Alternating split spoon and undisturbed samples with depth is recommended for soil samples. Color photographs of all cores sh ould be taken soon after removal from the borehole to document the c ondition of subsurface materials at the time of drilling. For a deeply embedded structure, sampling inte rvals should be properly determined and detailed field testing should be carried out along the length of t he embedded portion of the str ucture to obtain sufficient geologic and geotechnical information.

4.5.1 Sampling Rock

The engineering characteristics of the rock mass are related pr imarily to composition and geologic features of the rock units, including bedding planes, joints, fractures, orientation, position, length and spacing of any other geologi c discontinuities, surface infilling, and weathering. Rock outcrops may be one of the information sour ces necessary for rock mass characterization, especially for structures that require relatively shallow excavations. Core samples can also p rovide reliable information to define the engineering characteristics of the rock mass. Suitable coring m ethods should be employed, and rocks should be sampled to a depth belo w which rock characteristics do not influence foundation performance.

Deeper borings may be needed to investigate zones critical to the evaluation of site geologic conditions. Within the depth int ervals influencing foundation p erformance, zones of poor core recovery or low rock quality designation, zones requiring casing, and other zones where drilling difficulties are encountered should be investigated . The nature, geometry, and spacing of any discontinuities or anomalous zones should be determi ned by means of suitable loggi ng or in situ observation methods, such as an in-hole camera or televiewer. Areas with evidence of sign ificant residual stresses should be evaluated based on in situ stress or strain measurements. Dip a nd strike of bedding planes and joints in the near-surface region can be measured at the outcrop. However, or iented cores are needed to estimate dips and strikes at depth.

A sufficient number of samples of both intact rock and jointed rock mass should be collected for strength property testing. The parameters developed from the ro ck mass characterization program provide input to different rock mass classification schemes (e.g., Rock Mass Rating system, Q system, Geological Strength Index system). The quality of the rock mass, estimated using the classification schemes, may be used in empirical design methods of rock excavation.

4.5.2 Sampling Coarse-Grained Soils

For coarse-grained soils, samples should be taken at depth inte rvals no greater than 1.5 meters

(5 feet). Beyond a depth of 15 meters (50 feet) below foundatio n level, the depth interval for sampling may be increased to 3 meters (10 feet). Requirements for undist urbed sampling of coarse-grained soils will depend on actual site conditi ons and planned laboratory testing. Experimentation with different sampling techniques may be necessary to determine the method th at is best suited to local soil conditions.

Coarse-grained soils containing gravels and boulders are among the most difficult materials to sample. Obtaining good-quality samples often requires the use of trenches, pits, or other accessible excavations into the zones of interest. Standard penetration te st results from these materials may be misleading and must be interpreted very carefully. When samplin g of coarse soils is difficult, information that may be lost when the soil is later classified in the laboratory should be recorded in the field. This information should include observed estimates of the percentage of cobbles, boulders, and coarse material and the hardness, shape, surface coating, and degree of weathering of coarse materials.

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4.5.3 Sampling Moderately Compressible or Normally Consolidated Clay or Clayey Soils

The properties of a fine-grained soil are related to the in sit u structure of the soil, and undisturbed samples should be obtained. Regulatory Position 4.5.4 of this g uide discusses procedures for obtaining undisturbed samples.

For compressible or normally cons olidated clays, undisturbed sa mples should be continuous throughout the compressible strata in one or more principal bor ings. These samples should be obtained by means of suitable fixed-piston, thin-wall tube samplers (see Ap pendix F to EM 1110-1-1804 for detailed procedures) or by methods that yield samples of equivalent qual ity. Borings used for undisturbed sampling of soils should be at l east 7.6 centimeters (3 inches) in diameter.

4.5.4 Obtaining Undisturbed Samples

In a strict sense, it is physically impossible to obtain undis turbed samples in borings because of the adverse effects resulting from the sampling process (e.g., unloading caused by removal from confinement) and from shipping or handling. Undisturbed samples are normally obtained using one of two general methods: push sample rs or rotary samplers. These methods permit obtaining satisfactory samples for shear strength, consolidation, permeability, and de nsity tests, provided careful measurements are made to document volume changes that occur during each step in the sampling process. Undisturbed samples can be sliced to permit detailed study of subsoil stratification, joints, fissures, failure planes, and other details. Guidance on commonly used undisturbed sampling m ethods can be found in relevant America Society for Testing and Materials (ASTM) standards.

Undisturbed samples of clays and silts can be obtained, as well as nearly undisturbed samples of some sands. Care is necessary in transporting any undisturbed s ample, and sands and silts are particularly vulnerable to vibration disturba nce. One method to prevent hand ling disturbance is to obtain

7.6-centimeter (3-inch) Shelby tube samples, drain them, and freeze them before transportation. The commonly used general procedure for recovering cohesionless soi l is to stabilize the soil, extract the sample, and later remove (rever se) the stabilizing agent after transportation, then trim and confine the specimen in a testing device. Reversible stabilization methods include the biopolymers agar and agarose, Elmers glue, and freezing. These stabilization methods must be durable enough to allow handling, transportation, and trimming of the samples. The methods also need to be reversible so that cohesionless soil can be restored to its in situ state before laboratory testing for evaluation of stress-stain-strength properties. Disturbance associated with these methods, such as volume changes in the soil and pore water when using chemical or biochemical solutions or by cryogenic ef fects, must be taken into account.

Test pits, trenches, and shafts offer the only effective access for collecting high-quality undisturbed samples and obtaining detailed information on strat ification, discontinuities, or preexisting shear surfaces. Cost increases with penetration depth as the ne ed for sidewall support arises. Samples can be obtained by hand-carving oversized blocks of soil or hand-ad vancing thin-walled tubes.

4.6 Borrow Materials

Exploration for borrow sources determines the location and amou nt of available borrow materials. Borrow area investigations should consider horizonta l and vertical intervals sufficient to determine material variability and include adequate sampling of representative materials for laboratory testing. Exploration of borrow sources should be tied to perfor mance requirements expected from the backfill. It is preferable that one source or quarry be selecte d as a candidate for supplying all project fill material when possible; otherwise, the number of candidate borr ow sources or quarries should be minimized for optimum quality assurance and quality control. Th e quantity of samples required should be

RG 1.132, Page 17 determined based on the type and number of tests planned. A suf ficient quantity of each fill type should be collected, preferably all during the initial sampling efforts, to ensure better uniformity in soils collected and sampling methods.

4.7 Materials Unsuitable for Foundations

Boundaries of unsuitable materials should be delineated by bori ngs and representative sampling and testing. These boundaries should be used to define the requ ired excavation limits.

4.8 Transportation and Storage of Samples

Handling, storage, and transporta tion of samples are as critical for sample quality as the collection procedures used. Disturbance of samples after collection can happen in a variety of ways and transform samples from high quality to slightly disturbed to unusable. So il samples can change dramatically because of moisture loss, moisture migration within the sample, freezin g, vibration, shock, or chemical reactions.

Moisture loss might not be critical on representative samples b ut should be kept to a minimum.

Moisture migration within a sample can cause differential residual pore pressure to equalize with time.

Water can move from one layer to another, causing significant c hanges in the undrained strength and compressibility of the sample. Freezing of clay or silt samples can cause ice lenses to form and severely disturb the samples. Therefore, s torage room temperatures for clay and silt samples should be kept above

4 degrees Celsius (C). Vibration or shock can provoke remolding and strength or density changes, especially in soft and sensitive clays, and cohesionless samples. Transportation should be carefully arranged to avoid such effects. Chemical reactions between samples and sample containers can occur during storage and induce changes that affect soil plasticity, compressibility, and shear strength.

Therefore, selection of the correct sample container material is important.

Unless stabilized chemically or by freezing, cohesionless soil samples are particularly sensitive to disturbance from impact and vibration during removal from the b orehole or sampler and subsequent handling. Samples should (1) be kept in the same orientation as that in which the samples were taken at all times (e.g., in a vertical position if sampled in a vertica l borehole), (2) be well padded for isolation from vibration and impact, and (3 ) be transported with extreme care if undisturbed sa mples are required.

4.9 In Situ Testing

In situ testing of soil and rock materials should be conducted where necessary for definition of subsurface material properties and in situ state of stress usin g boreholes, excavations, test pits, and trenches that are either available or have been prepared for sampling and testing. Larger block samples for laboratory testing can also be obtained at the same locations. Appendix F to this guide shows some applicable in situ testing methods. NUREG/CR-5738 further describes the procedures.

In situ tests are often the best means to determine the enginee ring properties of subsurface materials and, in some cases, might be the only way to obtain meaningful results. Some materials are hard to sample and transport while keeping them representative of fi eld conditions, because of softness, lack of cohesion, or composition. In situ testing techniques offer a va luable option for evaluating soils and rocks that cannot be sampled for laboratory analysis.

Interpretation of in situ test results in soils, clay-rich shal es, and moisture-sensitive rocks requires consideration of the drainage that may occur during the test. C onsolidation during soil testing makes it difficult to determine whether the results relate to unconsolid ated-undrained, consolidated-undrained, consolidated-drained, or unconso lidated-drained conditions or t o intermediate conditions between these

RG 1.132, Page 18 limiting states. Interpretation of in situ test results require s the complete evaluation of test conditions and limitations.

Rock units commonly contain natu ral joints, bedding planes, or other discontinuities (e.g., faults and shear zones) that result in irregularly shaped blocks that respond as a discontinuum to various loading conditions. Individual solid blocks might have relatively high compressive and shear strengths, whereas strength along the discontinuity surfaces can be significantly lower and highly anisotropic. Commonly, little or no tensile strength exists across discontinuities. La rge-scale in situ tests tend to average out effects of the complex interactions between intact rock blocks and discontinuities. In situ tests in rock are used to determine in situ stresses and deformation properties, including strength and deformation modulus of the jointed rock mass. These tests also help to determine strength and residual stresses along discontinuities in the rock mass . In situ testing performed in weak, near-surface rocks includes penetration tests, plate loading tests, pressure-meter tests, and field geophysical tests.

Table F-2 in Appendix F lists in situ tests that are useful for determining the shear strength of subsurface materials. Direct shear-strength tests in rock measure peak and residual direct shear strength as a function of normal stress on the shear plane. Direct shear st rength from intact rock can be measured in the laboratory if the specimen can be cut and transported witho ut disturbance. In situ shear tests are discussed and compared by Nicholson (1983; Ref. 20) and Bowles (1996; Ref. 21). The suggested in situ method for determining direct shear strength of rocks is descri bed in RTH 321-80, Suggested Method for In Situ Determination of Direct Shear Strength (ISRM), issued 1980 (Ref. 22). Although the standard penetration test (SPT) is used ext ensively in investigations of soil liquefaction susceptibility, the cone penetration test (CPT) is also widely used in site investigatio n because (1) the CPT provides continuous penetration resistance profiles for soils and (2) CPT results a re more repeatable and consistent (Ref. 23).

Both Appendix C and Appendix F compare the applicability and li mitations of the CPT and SPT.

4.10 Geophysical Investigations

4.10.1 General

Geophysical investigations include surface geophysical surveys and borehole logging and other testing techniques, which are important for determining subsurf ace engineering properties and geologic and hydrologic characteristics, features, and conditions. Data from these investigations should be used to provide more continuous, and po ssibly deeper, subsurface information for filling in between data derived from surface outcrops, trenches, and boreholes and correlating data from other sources.

Available geophysical and borehol e logging methods are listed in Appendix E to this guide and in EM-1110-1-1802, Geophysical Exploration for Engineering and En vironmental Investigations, issued

1995 (Ref. 24). A geophysical expl oration should consider the f ollowing factors:

(1) Subsurface and surface geophysical investigations cannot be sub stituted for each other. Both surface and subsurface geophysical investigations should be con ducted to validate and calibrate site investigation results.

(2) For subsurface material engineering properties that could have high consequences if they are not determined properly, or are deemed critical to safe performance of the facility, multiple tests using different methods are recommended to capture uncertaintie s.

(3) Geophysical explorations should be carried out by personnel hav ing the necessary technical background and experience in the techniques used.

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(4) Information related to acquisition of raw and processed field t est data (e.g., spacing of data collection locations and instrume nt settings) should be recorde d following applicable standards and quality assurance/quality cont rol procedures to allow for proper interpretation of test results.

Selection of the appropriate pen etration depths for geophysical investigations shall consider the need for information on site-specific stratigraphy and paramete rs of the materials encountered for input to analyses of site seismic response, soil-structure interaction, and foundation/structure stability. To properly determine site shear wave velocity profiles, borehole testing m ethods (e.g., P-S suspension logging and crosshole testing) combined with surface geophysical tests, suc h as seismic refraction and reflection surveys and spectral analysis of surface wave (SASW) methods (Ref. 25), should be used to cross-check and consolidate test results. Applicable ASTM and American Soci ety of Civil Engineers standards should be used when conducting geophysical investigations.

4.10.2 Surface Geophysics

Recommended surface geophysical techniques include seismic methods (e.g., reflection, refraction, and surface wave methods), electrical methods (e.g. , resistivity), electromagnetic methods (e.g., ground-penetrating radar) , and potential field methods ( e.g., gravity and magnetics). Surface geophysical methods can be used to (1) measure shear-wave veloc ity profiles, (2) determine subsurface geologic conditions such as str ata layers and thickness, faults, voids, and underground objects, and

(3) derive important material engineering properties (e.g., ela stic moduli). The surface geophysical measurements should be correlated with borehole geophysical data and geologic logs to derive maximum benefit from the measurements.

4.10.3 Borehole Geophysics

Geophysical borehole logs are very useful for determining geolo gic, hydrologic, and engineering properties of subsurface materials, including correlation of lithologic units between boreholes. A suitable suite of geophysical logging methods (Ref. 23) should be used f or borehole geophysics study.

Appendix E to this guide lists so me of the applicable geophysical logging methods, along with the geologic characteristics and engineering parameters the methods can help to determine.

Crosshole and single borehole geophysical methods can be used t o obtain detailed information about subsurface materials in both horizontal and vertical dire ctions. These methods can be used to determine site shear wave velocity profiles and derive engineer ing and hydrogeologic properties, such as shear modulus, porosity, and perm eability. When very detailed i nformation is needed, tomographic methods can be used to determine the geophysical properties of materials between boreholes.

Geophysical borehole logging met hods include P-S suspension (Re f. 26), caliper, gamma, electrical resistivity, electromagnetic induction, fluid resist ivity, temperature, flowmeter, television, acoustic televiewer, and other logs. These borehole loggings ca n measure in situ seismic waves;

determine lithology; measure dip and strike of important struct ural features of the rock units; evaluate intrusion of grout into the rock mass; distinguish and analyze fractures, shear zones, soft zones, cavities, and other discontinuities; and characterize water quality and f low.

Borehole logging and crosshole shear-wave measurements are generally low-strain measurements. In rock, these measurements provide a suitable ap proximation of shear modulus even under high-strain conditions. In soil, the shear modulus depend s strongly on strain level. Therefore, these methods are usually insufficient because nonlinear effects can occur that may lead to misinterpretation of the test results. Laboratory tests (e.g., resonant column torsi onal shear test) are more promising for shear modulus determination.

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4.11 Logs of Subsurface Investigations

It is important to have a complet e and detailed log for every borehole. Boring logs should contain dates, locations, and depths of all borings, as well as elevations that are related to a permanent benchmark for the top and bottom of borings, boundaries of soil layers an d rock units, and the level at which the water table was encountered. In addition, classification and description of soil layers and rock units, blow count values obtained from SPTs, percent recovery of rock core, quantity of core not recovered for each core interval or drill run, and rock quality designation should be noted. The factors that are needed for blow count correction, such as th e type of sampler, hammer, and drill rod used in the SPT test, should also be recorded.

Results of field permeability tests and geophysical borehole lo gging should be included on the logs. The type of tools used to make the boring should be recor ded. Notes should be provided for everything significant to the interpretation of subsurface conditions, such as drilling rate, settling or dropping of drill rods, abnormally low resistance to drilling o r advance of samplers, core loss, and instability or heave of the side and bottom of boreholes. Influ x of ground water, depths and amounts of water or drilling mud losses and depths at which circulation is recovered, and any other unique feature or occurrence should be recorded on the boring logs and geologic c ross sections. Incomplete or abandoned borings should be described with the same care as successfully completed borings.

Logs of the walls and floor of exploratory trenches and other e xcavations should be presented in a graphic format that shows impor tant components of the soil and structural features in rock units in sufficient detail to permit independent evaluation. Photomosaic panoramas can provide additional perspective and verification of t rench features. Locations of a ll exploration efforts should be recorded in a GIS database and shown on geologic cross sections along with elevations and all pertinent data.

5. Ground Water Investigations

Knowledge of ground water conditio ns and the relationship of th ose conditions to surface water and variations associated with seasons or tides is needed for foundation analyses. Ground water levels and conditions are normally observed in boreholes at the time they are drilled. However, these observations should be supplemented by additi onal data from properly install ed wells with piezometers that are monitored at regular intervals from time of installation at lea st through the construction period.

Appendix G to this guide tabulates types of instruments for mea suring ground water pressure and the advantages and limitations of each. ASTM D5092, Standard Pract ice for Design and Installation of Groundwater Monitoring Wells (Ref. 27) provides guidance on th e design and installation of ground water monitoring wells. Types of piezometers, construction details, and sounding devices are described in EM 1110-2-1908, Instrumentati on of Embankment Dams and Levees, issued 1995 (Ref. 28).

Ground water conditions should be observed during site investig ations, and water level measurements should be taken in exploratory borings. Ground wat er or drilling mud level should be measured at the start of each workday for borings in progress, at the completion of drilling, and when water levels in the borings have stabilized. Ground water observation wells should be i nstalled in as many locations as needed to adequately define the ground water envir onment. Pumping tests are preferred for evaluating local permeability and conductivity parameters and the level of confinement between aquifers.

These parameters are input into calculations for assessing dewa tering requirements for construction and operation of the plant. For major excavations where constructio n dewatering is required, piezometers or observation wells should be used during construction to monitor the ground water surface and pore pressures beneath the excavation and in the adjacent ground. Th is guide does not cover ground water monitoring during construction of plants that are designed with permanent dewatering systems.

RG 1.132, Page 21 In areas where perched ground water tables or artesian aquifer systems are expected, piezometers should be installed in each groun d water element so that the piezometric level can be determined for the particular aquifer or ground water unit. Care should be taken i n the design and installation of piezometers to prevent hydraulic communication between aquifers. The occurr ence of artesian pressure in borings should be noted on boring logs, and the artesian heads should b e measured and logged.

6. Construction Mapping

It is necessary to confirm that in situ conditions revealed in excavations for safety-related structures were accurately captured and interpreted during the preconstruction site characterization stage to ensure that information rela ted to actual in situ conditions is properly incorporated into plant design analyses. Detailed geologic mapping should be performed for all construction excavations for safety-related structures and other excavations important for v erification of subsurface conditions (e.g., cut slopes, tunnels, chamb ers, and water inlets and outlets). Particular attention should be given to geologic features and characteristics that might be important i n assessment of the behavior of foundation materials, including tectonic and nontectonic features and lith ologic variations, which might be undetected and different from what was assumed based on the res ults of site investigations prior to excavations. The detailed geologic mapping should be performed after the completion of excavations and before placement of backfill.

The importance of the geologic mapping is reinforced by the geo logic mapping license condition normally imposed in a combined or construction license. This li cense condition requires a licensee to commit to performing the follo wing associated activities: (1) conduct detailed geologic mapping of excavations for safety-related structures, (2) examine and eval uate geologic features discovered in those excavations, and (3) notify the N RC once the excavations are open for inspection by NRC staff. Changes in foundation design that result from information acquired by t he detailed geologic mapping should be noted on appropriate plans and in cluded in maps, cross sections, and the database. All pertinent newly discovered geologic features shoul d be evaluated for their pote ntial impact on foundation materials. This evaluation might require relative or absolute age dates on cert ain features and particular tectonic structures such as faults and shear zones. The maps, cross sections, and database should include any features installed to improve, modify, or control geologic cond itions (e.g., reinforcing systems, permanent dewatering systems, and special treatment areas). Photographic records of foundation geologic mapping and treatments should be made and retained in the database. The GIS and other databases should be continuously updated, up to and including the construction phase, resulting in inclusion of final as-built information in the database.

Appendix A to NUREG/CR-5738 provides detailed guidance on appro priate technical procedures for geologic mapping of foundatio n materials. Geologic mapping of tunnels and other underground openings must be planned differe ntly from foundation mapping. T echnical procedures for mapping tunnels are outlined in Appendi x B to NUREG/CR-5738 and can be modified for large chambers. The individual in charge of foundati on geologic mapping should be f amiliar with plant design and subsurface features and characteristics based on previous site investigati ons. This person should consult with plant design personnel during excavation whenever differences between the actual geology and the design-basis geologic model are discovered. T he same individual should be in volved in all decisions about changes in plant foundation design and any additional foundation treatment s that might be necessary based on actual observed conditions of the foundation materials.

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7. Support Functions

7.1 Surveying, Mapping, and Development of the GIS Database

Surveying is an important function that should accompany all es sential site investigation activities from reconnaissance through construction mapping. Many methods of surveying are available, from traditional triangulation or plane table work and leveling to e lectronic distance and GPS measurements.

For mapping small areas, plane table methods may still be rapid enough. In most cases, however, GPS or differential GPS together with automated recording and computin g procedures is the most suitable method. Procedures for GPS surveying can be found in EM-1110-1- 1003, NAVSTAR Global Positioning System Surveying, issued 2011 (Ref. 18). The GPS m easurements and other surveyed locations should be tied to Nati onal Geodetic Survey (NGS) markers to be compatible with topographic and digital maps of various typ es. Survey results should have adequate precision with no more than

0.3 meter (1.0 foot) onshore and 1.5 meters (5.0 feet) offshore for plan coordinates and 3 centimeters

(0.1 foot) onshore and 0.3 meter (1.0 foot) offshore for elevat ion. For greater accuracy, it might still be necessary to perform a certain amount of conventional leveling.

A suitable coordinate system for the site should be chosen. Thr ee-dimensional coordinate systems include the World Geodetic System of 1984, the International Te rrestrial Reference Frame, and the North American Datum of 1983 (NAD 83). Coordinates should be referred to NAD 83 to be legally recognized in most U.S. jurisdictions. More over, NGS provides software for converting the ellipsoid-based heights of NAD 83 to the sea-level-based heights that appear on topographi c maps. NAD 83 coordinates are readily determined when measurements tie the site to an NGS marker.

All three-dimensional information should be entered into a GIS database because data of various types, in the form of tables, can be associated with a coordinate system and recalled to form the desired graphical output. Choice of a specific system is up to the appl icant, but the data should be in a format that is readily readable. It is necessary to have personnel with experience in surveying and storing and displaying data in a GIS database throughout all phases of site investigation and construction in order to

(1) accurately record information obtained, (2) place geologic, geotechnical, sampling, and testing information into a spatial contex t, and (3) permit visual displ ay of data on maps and cross sections.

Development of the GIS database is an essential activity that should be given proper emphasis and support by applicants and licensees.

7.2 Records, Sample Retention, and Quality Assurance

All data acquired during site characterization investigations should be organized into logical categories and preserved as a permanent record, at least until the power plant is licensed to operate and all matters relating to the interpretation of subsurface conditions at the site have been resolved. Much of the data will already be part of the GIS database, but other data a nd records, such as logs of operations, photographs, test results, and engineering evaluations and calc ulations, should also be preserved for further reference.

Samples and rock cores from principal borings should also be re tained. Regulatory Position 4.3.3 and Chapter 7 of NUREG/CR-5738 describe procedures for handling and storing samples. The need to retain samples and cores beyond the recommended time is a matter of judgment and should be evaluated on a case-by-case basis. For example, soil samples in tubes will deteriorate with time and will not be suitable for undisturbed testing. However, they may be used as a visual record of the foundation material.

Similarly, rock cores subject to slaking and rapid weathering, such as shale, will also deteriorate.

Photographs of soil samples and rock cores, with field and fina l logs of all borings, should be preserved for a permanent record.

RG 1.132, Page 23 The site investigations should be included in the overall quali ty assurance program for plant design and construction according to the guidance in RG 1.28, Quality Assurance Program Criteria (Design and Construction) (Ref. 29), and the requirements of A ppendix B, Quality Assurance Criteria for Nuclear Power Plants and Fuel Reprocessing Plants, to 10 C FR Part 50. Therefore, field operations and records preservation should be conducted in accordance with quality assurance principles and procedures.

RG 1.132, Page 24

D. IMPLEMENTATION

The NRC staff may use this regulatory guide as a reference in its regulatory processes, such as licensing, inspection, or enforcement. However, the NRC staff d oes not intend to use the guidance in this regulatory guide to support NRC staff actions in a manner that would constitute backfitting as that term is defined in 10 CFR 50.109, Backfitting, and as described in NR C Management Directive 8.4, Management of Backfitting, Forward Fitting, Issue Finality, an d

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Rev 3, Geologic and Geotechnical Site Characterization Investigations for Nuclear Power Plants
	ML21298A054
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Issue date:	12/31/2021
From:	Scott Stovall; NRC/RES/DE/SGSEB
To:	;
	O'Donnell E
Shared Package
ML21295A502	List: ML21298A059; Regulatory Guide 1.132;
References
	DG-1392 RG 1.132 Rev 3
	Download: ML21298A054 (56)
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, (Ref. 30), nor does the NRC staff intend to use the guidance to affect the issue finality of an approval under

10 CFR Part 52, Licenses, Certifications, and Approvals for Nu clear Power Plants. The staff also does not intend to use the guidance to support NRC staff actions in a manner that constitutes forward fitting as that term is defined and described in Management Directive 8.4. If a licensee believes that the NRC is using this regulatory guide in a manner inconsistent with the d iscussion in this Implementation section, then the licensee may file a backfitting or forward fitting app eal with the NRC in accordance with the process in Management Directive 8.4.

RG 1.132, Page 25 REFERENCES1

1. U.S. Code of Federal Regulations , Domestic Licensing of Production and Utilization Facilities, Part 50, Chapter I, Title 10, Energy.

2. U.S. Code of Federal Regulations , Licenses, Certifications, and Approvals for Nuclear Power Plants, Part 52, Chapter I, Title 10, Energy.

3. U.S. Code of Federal Regulations , Reactor Site Criteria, Part 100, Chapter I, Title 10,

Energy.

4. U.S. Nuclear Regulatory Commission, Standard Review Plan for t he Review of Safety Analysis Reports for Nuclear Power Plants: LWR Edition, NUREG-0800.

5. U.S. Nuclear Regulatory Commission, Seismic Design Classificat ion for Nuclear Power Plants, Regulatory Guide 1.29, Revision 5, July 2016.

6. U.S. Nuclear Regulatory Commission, Standard Format and Conten t of Safety Analysis Reports for Nuclear Power Plants: LWR Edition, Regulatory Guide 1.70, Revision 3, November 1978.

7. U.S. Nuclear Regulatory Commission, Applications for Nuclear P ower Plants (LWR Edition),

Regulatory Guide 1.206, Revision 1, October 2018.

8. U.S. Nuclear Regulatory Commission, Laboratory Investigations of Soils and Rocks for Engineering Analysis and Design of Nuclear Power Plants, Regul atory Guide 1.138, Revision 3, December 2014.

9. U.S. Nuclear Regulatory Commission, Guidelines for Categorizin g Structures, Systems, and Components in Nuclear Power Plants According to Their Safety Si gnificance, Regulatory Guide 1.201, Revision 1, May 2006.

10. U.S. Nuclear Regulatory Commission, General Site Suitability C riteria for Nuclear Power Stations, Regulatory Guide 4.7, Revision 3, March 2014.

11. U.S. Nuclear Regulatory Commission, A Performance-Based Approach to Define the Site-Specific Earthquake Ground Motion, Regulatory Guide 1.208 , March 2007.

12. National Research Council, Geotechnical Site Investigations fo r Underground Projects, Vols. 1-2, The National Academie s Press, Washington, DC, 1984.

13. U.S. Nuclear Regulatory Commission, Nuclear Regulatory Commiss ion International Policy Statement, Federal Register, Vol. 79, No. 132, July 10, 2014, pp. 39415-3941.

1 Publicly available NRC published documents are available electronically through the NRC Library on the NRCs public Web site at http://www.nrc.gov/reading-rm/doc-collections/ and through the NRCs Agencywide Documents Access and Management System (ADAMS) at http://www.nrc.gov/reading-rm/adams.html. The documents can also be viewed online or printed for a f ee in the NRCs Public Document Room (PDR) at 11555 Rockville Pike, Rockville, MD. For problems with ADAMS, contact the PDR staff at (301) 415-4737 or (800) 397-4209; fax (301) 415-3548; or e-mail pdr.resource@nrc.gov.

RG 1.132, Page 26

14. U.S. Nuclear Regulatory Commission, Regulatory Guides, Manage ment Directive 6.6, May 2, 2016, ADAMS Accession No. ML18073A170.

15. International Atomic Energy Agency, Geotechnical Aspects of Si te Evaluation and Foundations for Nuclear Power Plants, IAEA Safety Standards Series No. NS- G-3.6, 2005.2

16. International Atomic Energy Agency, Seismic Hazards in Site Evaluation for Nuclear Installations. IAEA Specific Safety Guide No. SSG-9, 2010.

17. Environmental Laboratory, Corps of Engineers Wetlands Delineat ion Manual, Technical Report Y-87-1, U.S. Army Corps of Engineers Waterways Experimen t Station, Vicksburg, MS,

1987.

18. U.S. Army Corps of Engineers, NAVSTAR Global Positioning Syste m Surveying, Engineer Manual (EM) 1110-1-1003, Washington, DC, 2011.

19. U.S. Army Corps of Engineers, Geotechnical Investigations, En gineer Manual EM 1110-1-1804, Washington, DC, 2001.

20. Nicholson, G.A., In Situ and Laboratory Shear Devices for Rock : A Comparison, Technical Report GL-83-14, U.S. Army Corps of Engineers, Waterways Experi ment Station, Vicksburg, MS, 1983.

21. Bowles, J.E., Foundation Analysis and Design , 5th Ed., McGraw-Hill, New York, 1996.

22. U.S. Army Corps of Engineers, Suggested Method for In Situ Det ermination of Direct Shear Strength (ISRM), RTH 321-80, Waterways Experiment Station, Vic ksburg, MS, 1980.

23. ASTM International, Standard G uide for Planning and Conducting Borehole Geophysical Logging, ASTM D5753-05, 2010. 3

24. U.S. Army Corps of Engineers, Geophysical Exploration for Engi neering and Environmental Investigations, Engineer Manual EM 1110-1-1802, Washington, DC , 1995.

25. Gucunski, N., and R.D. Woods, In strumentation for SASW Testing, Recent Advances in Instrumentation, Data Acquisition, and Testing in Soil Dynamics Proceedings , Geotechnical Special Publication No. 29, pp. 1-16, American Society of Civil Engineers, New York, 1991.

26. Diehl, J.G., Martin, A.J., and R.A. Steller, Twenty-Year Retro spective on the OYO P-S

Suspension Logger, Proceedings of the 8th U.S. National Conference on Earthquake Engineering, April 18-22, 2006 , San Francisco, California.

2 Copies of International Atomic Energy Agency (IAEA) documents may be obtained through their Web site:

WWW.IAEA.Org/ or by writing the International Atomic Energy Agency, P.O. Box 100 Wagramer Strasse 5, A-1400

Vienna, Austria.

3 Copies of ASTM International (ASTM) standards may be purchased from ASTM, 100 Barr Harbor Drive, P.O.

Box C700, West Conshohocken, Pennsylvania 19428-2959; telephone (610) 832-9585. Purchase information is available through the ASTM Web site at http://www.astm.org.

RG 1.132, Page 27

27. ASTM International, Standard Pr actice for Design and Installation of Groundwater Monitoring Wells, ASTM D5092-04, 2010.

28. U.S. Army Corps of Engineers, Instrumentation of Embankment Da ms and Levees, Engineer Manual EM 1110-2-1908 (Part 1), Washington, DC, 1995.

29. U.S. Nuclear Regulatory Commission, Quality Assurance Program Criteria (Design and Construction), Regulatory Guid e 1.28, Revision 5, October 2017 .

30. U.S Nuclear Regulatory Commission, Management of Backfitting, Forward Fitting, Issue Finality, and Information Request s, Management Directive 8.4, Washington, DC.

RG 1.132, Page 28

APPENDIX F

IN SITU TESTING METHODS

Table F-1 In Situ Tests for Rock and Soil (adapted from EM 1110-1-1804, U.S . Army Corps of Engineers, 2001)

APPLICABILITY TO

PURPOSE OF TEST TYPE OF TEST SOIL ROCK

Shear strength Standard penetration test X

Field vane shear X

Cone penetrometer test X

Direct shear X

Plate bearing or jacking X Xa Borehole direct shearb X

Pressuremeterb X

Uniaxial compressiveb X

Borehole jackingb X

Bearing capacity Plate bearing X Xa Standard penetration X

Stress conditions Hydraulic fracturing X X

Pressuremeter X Xa Overcoring X

Flatjack X

Uniaxial (tunnel) jacking X X

Borehole jackingb X

Chamber (gallery) pressureb X

Mass deformability Geophysical (refraction) X X

Pressuremeter or dilatometer X Xa Plate bearing X X

Standard penetration X

Uniaxial (tunnel) jacking X X

Borehole jackingb X

Chamber (gallery) pressureb X

Relative density Standard penetration X

In situ sampling X

Coneb penetration X

Liquefaction susceptibility Standard penetration X

Cone penetration test X

Shear wave velocity (vs) X

a. Primarily for clay shales, badly decomposed, or moderately soft rocks, and rock with soft seams.

b. Less frequently used.

RG 1.132, Appendix F, Page F-1 APPENDIX F, Contd.

Table F-2 In Situ Tests to Determine Shear Strength (adapted from EM 1110-1-1804, U.S . Army Corps of Engineers, 2001)

FOR

TEST SOILS ROCKS REMARKS

Standard X Use as index test only for strength. Develop local correlations.

penetration Unconfined compressive strength in tons/square foot) is often 1 /6 to

1/8 of N-value.

Direct shear X X Expensive. Use when representative undisturbed samples cannot be obtained.

Field vane shear X Use strength reduction factor.

Plate bearing X X Evaluate consolidation effects that may occur during test.

Uniaxial X Primarily for weak rock. Expensive since several sizes of specimens compression must be tested.

Cone penetration X Consolidated undrained strength of clays. Requires estimate of test bearing factor, Nc.

Table F-3 In Situ Tests to Determine Stress Conditions (adapted from EM 1110-1-1804, U.S . Army Corps of Engineers, 2001)

TEST SOILS ROCKS REMARKS

Hydraulic fracturing X Only for normally consolidated or slightly consolidated soils

Hydraulic fracturing X Stress measurements in deep holes for tunnels

Vane shear X Only for recently compacted clays, silts and fine sands (see Blight,

1974,1 for details and limitations)

Overcoring X Usually limited to shallow depth in rock techniques

Flatjacks X

Uniaxial (tunnel) X X May be useful for measuring lateral stresses in clay shales and rocks, jacking also in soils

Pressuremeter X

(Menard)

1 Blight, G.E., Indirect Determination of in situ Stress Ratios in Particulate Materials, Proceedings of a Specialty Conference, Subsurface Explorations for Underground Excavation and Heavy Construction, American Society of Civil Engineers, New York, 1974.

RG 1.132, Appendix F, Page F-2 APPENDIX F, Contd.

Table F-4 In Situ Tests to Determine Deformation Characteristics (adapted from EM 1110-1-1804, U.S . Army Corps of Engineers, 2001)

FOR

TEST SOILS ROCKS REMARKS

Geophysical X X For determining dynamic Youngs Modulus, E, at the small strain refraction, induced by test procedure. Test values for E must be reduced to values crosshole and corresponding to strain levels induced by structure or seismic loads.

downhole

Pressuremeter X X Consider test as possibly useful but not fully evaluated. For s oils and soft rocks, shales, etc.

Chamber test X X

Uniaxial (tunnel) X X

jacking

Flatjacking X

Borehole jack or X

dilatometer

Plate bearing X

Standard X Used in empirical correlations to estimate settlement of footings; a penetration number of relationships are published in the literature to relate penetration test blow counts to settlement potential.

RG 1.132, Appendix F, Page F-3

Regulatory Guide 1.132: Difference between revisions

Revision as of 16:52, 19 November 2024

Contents

A. INTRODUCTION

A. INTRODUCTION

B. DISCUSSION

D. IMPLEMENTATION

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1. General Requirements

6. Construction Mapping

7. Support Functions

D. IMPLEMENTATION

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Revision as of 16:52, 19 November 2024

A. INTRODUCTION

A. INTRODUCTION

B. DISCUSSION

D. IMPLEMENTATION

B. DISCUSSION

1. General Requirements

6. Construction Mapping

7. Support Functions

D. IMPLEMENTATION

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