CONTENTS

Page

Acknowledgments . . . . . . . . . . . . . . . . . . . . . . iiiForeword . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . v

Chapter 1 Introduction . . . . . . . . . . . . . . . . . 1

Chapter 2 Geologic Terminology andClassifications for GeologicMaterials . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Established References for GeologicalTerminology . . . . . . . . . . . . . . . . . . . . . . . . 3

Geologic Classification of Materials . . . . . . . 4Engineering Classification of Geologic

Materials . . . . . . . . . . . . . . . . . . . . . . . . . . 5Application and Use of Standard Indexes,

Terminology, and Descriptors . . . . . . . . . . 9Units of Measurements for Geologic Logs

of Exploration, Drawings, and Reports . . 12Bibliography . . . . . . . . . . . . . . . . . . . . . . . . . . 15

Chapter 3 Engineering Classification andDescription of Soil . . . . . . . . . . . . . . . . . 17

General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17Classifications of Soils . . . . . . . . . . . . . . . . . . 21Abbreviated Soil Classification Symbols . . . 39Description of the Physical Properties

of Soil . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40Narrative Descriptions and Examples . . . . . 48Use of Soil Classification as Secondary

Identification Method for MaterialsOther Than Natural Soils . . . . . . . . . . . . . 51

Bibliography . . . . . . . . . . . . . . . . . . . . . . . . . . 56

Chapter 4 Classification of Rocks andDescription of PhysicalProperties of Rock . . . . . . . . . . . . . . . . . 57

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . 57Rock Classification . . . . . . . . . . . . . . . . . . . . 57

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Chapter 4 Classification of Rocks andDescription of PhysicalProperties of Rock (continued)

Page

Description of Rock . . . . . . . . . . . . . . . . . . . . 59Example Descriptions . . . . . . . . . . . . . . . . . . 86Bibliography . . . . . . . . . . . . . . . . . . . . . . . . . . 90

Chapter 5 Terminology and Descriptionsfor Discontinuities . . . . . . . . . . . . . . . . . 91

General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91Indexes for Describing Fracturing . . . . . . . . 94Description of Fractures . . . . . . . . . . . . . . . . 98Descriptions of Shears and Shear Zones . . . 114Bibliography . . . . . . . . . . . . . . . . . . . . . . . . . . 126

Chapter 6 Geologic Mapping and Documentation . . . . . . . . . . . . . . . . . . . . 129

Responsibilities of the Engineering Geologist . . . . . . . . . . . . . . . . . . . . . . . . . . . 129

Development of a Study Plan . . . . . . . . . . . . 130Specific Mapping Requirements . . . . . . . . . . 133Global Positioning System . . . . . . . . . . . . . . 135Site Mapping . . . . . . . . . . . . . . . . . . . . . . . . . 153Dozer Trench Mapping . . . . . . . . . . . . . . . . . 157Backhoe Trench Mapping . . . . . . . . . . . . . . . 161Construction Geologic Mapping . . . . . . . . . . 167Large Excavation Mapping . . . . . . . . . . . . . . 168Steep Slope Mapping . . . . . . . . . . . . . . . . . . . 169Canal and Pipeline Mapping . . . . . . . . . . . . 170Underground Geologic Mapping . . . . . . . . . 171Underground Geologic Mapping Methods . . 185Photogeologic Mapping . . . . . . . . . . . . . . . . . 196Analysis of Aerial Photographs . . . . . . . . . . 198

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Chapter 6 Geologic Mapping and Documentation (continued)

Page

Photoanalysis for ReconnaissanceGeologic Mapping . . . . . . . . . . . . . . . . . . . . 199

Availability of Imagery . . . . . . . . . . . . . . . . . 200References . . . . . . . . . . . . . . . . . . . . . . . . . . . 202Bibliography . . . . . . . . . . . . . . . . . . . . . . . . . . 203

Chapter 7 Discontinuity Surveys . . . . . . . . 205General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 205Bibliography . . . . . . . . . . . . . . . . . . . . . . . . . . 211

Chapter 8 Exploration Drilling Programs . . . . . . . . . . . . . . . . . . . . . . . . . 213

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . 213Preparation of Drilling Specifications

and Format . . . . . . . . . . . . . . . . . . . . . . . . . 223

Chapter 9 Groundwater Data AcquisitionMethods . . . . . . . . . . . . . . . . . . . . . . . . . . . 227

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . 227Design and Installation of Observation

Wells and Piezometers . . . . . . . . . . . . . . . 229Methods Used to Measure Groundwater

Levels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 235Methods and Techniques Used to Estimate

Flows from Seeps, Springs, and SmallDrainages . . . . . . . . . . . . . . . . . . . . . . . . . . 241

Computer-Based Monitoring Systems . . . . . 242Definitions . . . . . . . . . . . . . . . . . . . . . . . . . . . 245References . . . . . . . . . . . . . . . . . . . . . . . . . . . 246Bibliography . . . . . . . . . . . . . . . . . . . . . . . . . . 247

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Chapter 10 Guidelines for Core Logging . 249General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 249Format and Required Data for the Final Geologic Log . . . . . . . . . . . . . . . . . . . . . . . . 252Method of Reporting Orientation of Planar Discontinuities and Structural Features . 284Core Recovery and Core Losses . . . . . . . . . . 285Samples . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 287Core Photography . . . . . . . . . . . . . . . . . . . . . 288Equipment Necessary for Preparing

Field Logs . . . . . . . . . . . . . . . . . . . . . . . . . . 291Instruction to Drillers, Daily Drill Reports, and General Drilling Procedures . . . . . . . . 294

Chapter 11 Instructions for Logging Soils 313General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 313Formats for Test Pits and Auger Hole Logs 325Format of Word Descriptions for Drill Hole Logs . . . . . . . . . . . . . . . . . . . . . . . . . . . 333Exceptions to Test Pit and Auger Hole

Format and Descriptions for Drill Hole Logs . . . . . . . . . . . . . . . . . . . . . . . . . . 339

Equipment Necessary for Preparing the Field Log . . . . . . . . . . . . . . . . . . . . . . . . . . . 347

Example Descriptions and Format . . . . . . . . 349Laboratory Classifications in Addition to

Visual Classifications . . . . . . . . . . . . . . . . 349Word Descriptions for Various Soil Classifications . . . . . . . . . . . . . . . . . . . . . . . 351Reporting Laboratory Data . . . . . . . . . . . . . . 351Special Cases for USCS Classification . . . . . 363Reporting In-Place Density Tests . . . . . . . . . 364Bibliography . . . . . . . . . . . . . . . . . . . . . . . . . . 366

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Page

Chapter 12 Hazardous Waste Site Investigations . . . . . . . . . . . . . . . . . . . . . 367

General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 367Common Terminology and Processes . . . . . . 368Documentation . . . . . . . . . . . . . . . . . . . . . . . . 369Contaminant Characteristics and

Migration . . . . . . . . . . . . . . . . . . . . . . . . . . 375Classification and Handling of Materials . . 381Field Sampling Protocol . . . . . . . . . . . . . . . . 383Sample Analysis . . . . . . . . . . . . . . . . . . . . . . 402Safety at Hazardous Waste Sites . . . . . . . . . 405Sample Quality Assurance and

Quality Control . . . . . . . . . . . . . . . . . . . . . 406Sample Management . . . . . . . . . . . . . . . . . . . 410Decontamination . . . . . . . . . . . . . . . . . . . . . . 417

AppendixAbbreviations and Acronyms CommonlyUsed in Bureau of Reclamation Engineering Geology and Related toHazardous Waste . . . . . . . . . . . . . . . . . . . . 419

Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 433

TABLES

Table Page

2-1 Ground behavior for earth tunneling with steel supports . . . . . . . . . . . . . . . 10

2-2 Useful conversion factors— metric andEnglish units (inch-pound) . . . . . . . . . 14

3-1 Basic group names, primary groups . . . 26

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TABLES (continued)

Table Page

3-2 Basic group names, 5 to 12 percent fines . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

3-3 Criteria for describing dry strength . . . 313-4 Criteria for describing dilatancy . . . . . . 323-5 Criteria for describing toughness . . . . . 333-6 Criteria for describing plasticity . . . . . . 343-7 Identification of inorganic fine-grained

soils from manual tests . . . . . . . . . . . 363-8 Criteria for describing angularity of

coarse-grained particles . . . . . . . . . . . 413-9 Criteria for describing particle shape . . 423-10 Criteria for describing moisture

condition . . . . . . . . . . . . . . . . . . . . . . . 433-11 Criteria for describing reaction

with HCl . . . . . . . . . . . . . . . . . . . . . . . 433-12 Criteria for describing consistency of

in-place or undisturbed fine-grainedsoils . . . . . . . . . . . . . . . . . . . . . . . . . . . 44

3-13 Criteria for describing cementation . . . 443-14 Criteria for describing structure . . . . . . 453-15 Particle sizes . . . . . . . . . . . . . . . . . . . . . . 463-16 Checklist for the description of soil

classification and identification . . . . . 483-17 Checklist for the description of in-place

conditions . . . . . . . . . . . . . . . . . . . . . . . . 494-1 Igneous and metamorphic rock grain

size descriptors . . . . . . . . . . . . . . . . . . 704-2 Sedimentary and pyroclastic rock

particle-size descriptors . . . . . . . . . . . 714-3 Bedding, foliation, or flow texture

descriptors . . . . . . . . . . . . . . . . . . . . . . . 744-4 Weathering descriptors . . . . . . . . . . . . . 774-5 Durability index descriptors . . . . . . . . . 79

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TABLES (continued)

Table Page

4-6 Rock hardness/strength descriptors . . . 835-1 Fracture density descriptors . . . . . . . . . 975-2 Fracture spacing descriptors . . . . . . . . . 1025-3 Fracture continuity descriptors . . . . . . . 1025-4 Descriptors for recording fracture ends

in joint surveys . . . . . . . . . . . . . . . . . . 1035-5 Fracture openness descriptors . . . . . . . . 1045-6 Fracture filling thickness descriptors . . 1045-7 Fracture healing descriptors . . . . . . . . . 1075-8 Fracture roughness descriptors . . . . . . . 1095-9 Fracture moisture conditions

descriptors . . . . . . . . . . . . . . . . . . . . . . 1106-1 U.S. State plane coordinate systems –

1927 datum . . . . . . . . . . . . . . . . . . . . . 1376-2 U.S. State plane coordinate systems –

1983 datum . . . . . . . . . . . . . . . . . . . . . 14311-1 Checklist for the description of soils in

test pit and auger hole logs . . . . . . . . 32612-1 EPA recommended sampling containers,

preservation requirements, and holding times for soil samples . . . . . . 385

12-2 Summary of soil sampling devices . . . . 38812-3 Common laboratory testing methods . . 404

FIGURES

Figure Page

3-1 Modifiers to basic soil group names . . . 223-2 Flow chart for inorganic fine-grained

soils, visual method . . . . . . . . . . . . . . 23

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FIGURES (continued)

Figure Page

3-3 Flow chart for organic soils, visual method . . . . . . . . . . . . . . . . . . . . . . . . . 24

3-4 Flow chart for coarse-grained soils,visual method . . . . . . . . . . . . . . . . . . . 25

3-5 Plasticity chart . . . . . . . . . . . . . . . . . . . . 353-6 Sample of test results summary . . . . . . 534-1 Field classification of igneous rocks . . . 604-2 Field classification of sedimentary

rocks . . . . . . . . . . . . . . . . . . . . . . . . . . . 614-3 Field classification of metamorphic

rocks . . . . . . . . . . . . . . . . . . . . . . . . . . . 624-4 Field classification of pyroclastic rocks . 634-5 Charts for estimating percentage of

composition of rocks and sediments . 644-6 Descriptor legend and explanation

example . . . . . . . . . . . . . . . . . . . . . . . . 674-7 Permeability conversion chart . . . . . . . . 875-1 Rock Quality Designation (RQD)

computation . . . . . . . . . . . . . . . . . . . . . 965-2 Comparison of true and apparent

spacing . . . . . . . . . . . . . . . . . . . . . . . . . 1015-3 Examples of roughness and waviness of

fracture surfaces, typical roughnessprofiles, and terminology . . . . . . . . . . 108

5-4 Uniform shear zone . . . . . . . . . . . . . . . . 1155-5 Structured shear zone (two zones or

layers) . . . . . . . . . . . . . . . . . . . . . . . . . 1165-6 Structured shear zone (three layers) . . 1165-7 Uniform shear zone with veinlets . . . . . 1165-8 Uniform shear zone (composite) . . . . . . 1175-9 Standard descriptors and descriptive

criteria for discontinuities . . . . . . . . . 121

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FIGURES (continued)

Figure Page

6-1 Process of engineering geology mapping . . . . . . . . . . . . . . . . . . . . . . . . 131

6-2 Sample trench log . . . . . . . . . . . . . . . . . . 1606-3 Sample completed trench log . . . . . . . . . 1656-4 Tunnel mapping form with key

alphanumeric descriptors and mapping data . . . . . . . . . . . . . . . . . . . 173

6-5 Tunnel mapping form with blocks for title and geologic data . . . . . . . . . . . . 174

6-6 As-built summary geology tunnel map . 1796-7 Full periphery mapping method

layout . . . . . . . . . . . . . . . . . . . . . . . . . . 1866-8 Full periphery geologic map example . . 1886-9 Map layout of a tunnel for geologic

mapping . . . . . . . . . . . . . . . . . . . . . . . . 1916-10 Relationship of planar feature trace to

map projections . . . . . . . . . . . . . . . . . . 1927-1 Equatorial equal area net . . . . . . . . . . . 2097-2 Discontinuity log field sheet . . . . . . . . . 21010-1 Drill hole log, DH-123 . . . . . . . . . . . . . . 25310-2 Drill hole log, B-102, for Standard

Penetration Test . . . . . . . . . . . . . . . . . 25510-3 Drill hole log, DH-SP-2 . . . . . . . . . . . . . 25910-4 Drill hole log, SPT-107-2 . . . . . . . . . . . . 26110-5 Drill hole log, DH-DN/P-60-1 . . . . . . . . . 27010-6 Daily drill report . . . . . . . . . . . . . . . . . . 29210-7 Water testing record . . . . . . . . . . . . . . . 29910-8 Use of half-round to protect core . . . . . . 30110-9 Standard N-size core box . . . . . . . . . . . . 30310-10 Log of concrete and rock core . . . . . . . . . 30811-1 Log of test pit or auger hole . . . . . . . . . . 31411-2 Clean coarse-grained soils . . . . . . . . . . . 315

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FIGURES (continued)

Figure Page

11-3 Fine-grained soils . . . . . . . . . . . . . . . . . . 31611-4 Soil classifications based on laboratory

test data . . . . . . . . . . . . . . . . . . . . . . . . 31711-5 Auger hole with samples taken . . . . . . . 31811-6 Reporting laboratory classification in

addition to visual classification . . . . . 31911-7 Undisturbed soils . . . . . . . . . . . . . . . . . . 32011-8 Coarse-grained soils with fines . . . . . . . 32111-9 Coarse-grained soils with dual

symbols . . . . . . . . . . . . . . . . . . . . . . . . 32211-10 Reporting in-place density tests and

percent compaction . . . . . . . . . . . . . . . 32311-11 Soil with measured percentages of

cobbles and boulders . . . . . . . . . . . . . . 32411-12 Field form - soil logging . . . . . . . . . . . . . 32911-13 Soil with more than 50 percent cobbles

and boulders . . . . . . . . . . . . . . . . . . . . 33411-14 Borderline soils . . . . . . . . . . . . . . . . . . . . 33511-15 Test pit with samples taken . . . . . . . . . 33611-16 Disturbed samples . . . . . . . . . . . . . . . . . 33711-17 Two descriptions from the same

horizon . . . . . . . . . . . . . . . . . . . . . . . . . 33811-18 Drill hole advanced by tri-cone

rock bit . . . . . . . . . . . . . . . . . . . . . . . . . 34011-19 Log showing poor recovery . . . . . . . . . . . 34211-20 Log of landslide material (a) . . . . . . . . . 34311-21 Log of landslide material (b) . . . . . . . . . 34411-22 Log of bedrock . . . . . . . . . . . . . . . . . . . . . 34511-23 Geologic interpretation in test pit

(sheet 1) . . . . . . . . . . . . . . . . . . . . . . . . 35011-24 Geologic interpretation in test pit

(sheet 2) . . . . . . . . . . . . . . . . . . . . . . . . 352

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FIGURES (continued)

Figure Page

11-25 Geologic interpretation in test pit usinga geologic profile (1) . . . . . . . . . . . . . . 353

11-26 Geologic interpretation in test pit(sheet 3) . . . . . . . . . . . . . . . . . . . . . . . . 354

11-27 Geologic interpretation in test pit(sheet 4) . . . . . . . . . . . . . . . . . . . . . . . . 355

11-28 Geologic interpretation in test pit usinga geologic profile (2) . . . . . . . . . . . . . . 356

11-29 Geologic interpretation in test pit(sheet 5) . . . . . . . . . . . . . . . . . . . . . . . . 357

11-30 Geologic interpretation in test pit(sheet 6) . . . . . . . . . . . . . . . . . . . . . . . . 358

11-31 Geologic interpretation in test pit(sheet 7) . . . . . . . . . . . . . . . . . . . . . . . . 359

11-32 Geologic interpretation in test pit(sheet 8) . . . . . . . . . . . . . . . . . . . . . . . . 360

11-33 Geologic interpretation in test pit usinga geologic profile (3) . . . . . . . . . . . . . . 361

12-1 Aquifer types . . . . . . . . . . . . . . . . . . . . . . 37912-2 Typical monitoring well construction for

water quality sampling . . . . . . . . . . . . 39912-3 Soil and water sample identification

labels . . . . . . . . . . . . . . . . . . . . . . . . . . 41212-4 Chain-of-custody record . . . . . . . . . . . . . 41312-5 Custody seal . . . . . . . . . . . . . . . . . . . . . . 415

Chapter 1

INTRODUCTION

This manual provides guidelines and instructions forperforming and documenting field work. The manual isa ready reference for anyone engaged in field-orientedengineering geology or geotechnical engineering. Themanual is written for general engineering geology use aswell as to meet Reclamation needs. The application ofgeology to solving engineering problems is emphasized,rather than academic or other aspects of geology. Themanual provides guidance for:

• Geologic classification and description of rock androck discontinuities

• Engineering classification and description of soiland surficial deposits

• Application of standard indexes, descriptors, andterminology

• Geologic mapping, sampling, testing, andperforming discontinuity surveys

• Exploratory drilling

• Soil and rock logging

• Acquisition of groundwater data

• Core logging

• Soil logging

• Investigation of hazardous waste sites

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Although the methods described in this manual areappropriate for most situations, complex sites, conditions,or design needs may require modification or expansion ofthe suggestions, criteria, and indices to fit specificrequirements.

Many of the chapters in this manual will always needrevision because they cover material that changes astechnology changes. Critical comments, especially sug-gestions for improvement, are welcome from all users,not just the Bureau of Reclamation.

The appendix contains abbreviations and acronymscommonly used in engineering geology.

1 Brackets refer to bibliography entries at end of each chapter.

Chapter 2

GEOLOGIC TERMINOLOGY AND CLASSIFICATIONS FOR

GEOLOGIC MATERIALS

Established References for GeologicalTerminology

Adaptations or refinements of the Bureau of Reclamation(Reclamation) standards presented in this and subse-quent chapters may be established to meet specific designrequirements or site-specific geologic complexity whenjustified.

The Glossary of Geology, Fourth Edition [1]1, published bythe American Geological Institute (AGI), 1997, is acceptedby Reclamation as the standard for definitions of geologicwords and terms except for the nomenclature, definitions,or usage established in this chapter and chapters 3, 4,and 5.

The North American Stratigraphic Code (NASC) [2] is theaccepted system for classifying and naming stratigraphicunits. However, Reclamation's engineering geology pro-grams are focused primarily on the engineering prop-erties of geologic units, not on the details of formalstratigraphic classification. Stratigraphic names are notalways consistent within the literature, often change fromone locality to another, and do not necessarily conveyengineering properties or rock types. Use of stratigraphicnames in Reclamation documents normally will beinformal (lower case) (see NASC for discussion of formalversus informal usage). Exceptions to informal usage arefor names previously used formally in the area in discus-sions of geologic setting or regional geology. Normally,

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4

the first use of formal names in a report should include areference to a geologic map or publication in which theterm is defined.

Geologic Classification of Materials

The following definitions of geologic materials more fullysatisfy general usage and supersede those in the Glossaryof Geology. These definitions are for geologic classifica-tion of materials. They should not be confused with engi-neering classifications of materials such as rock and soilor rock and common excavation.

• Bedrock is a general term that includes any of the gen-erally indurated or crystalline materials that make up theEarth's crust. Individual stratigraphic units or units sig-nificant to engineering geology within bedrock may in-clude poorly or nonindurated materials such as beds,lenses, or intercalations. These may be weak rock unitsor interbeds consisting of clay, silt, and sand (such as thegenerally soft and friable St. Peter Sandstone), or claybeds and bentonite partings in siliceous shales of theMorrison Formation.

•Surficial Deposits are the relatively younger materialsoccurring at or near the Earth's surface overlying bed-rock. They occur as two major classes: (1) transporteddeposits generally derived from bedrock materials bywater, wind, ice, gravity, and man's intervention and(2) residual deposits formed in place as a result ofweathering processes. Surficial deposits may be stratifiedor unstratified such as soil profiles, basin fill, alluvial orfluvial deposits, landslides, or talus. The material may bepartially indurated or cemented by silicates, oxides,carbonates, or other chemicals (caliche or hardpan). Thisterm is often used interchangeably with the imprecisely

TERMINOLOGY

5

defined word “overburden.” “Overburden” is a miningterm meaning, among other things, material overlying auseful material that has to be removed. “Surficialdeposit” is the preferred term.

In some localities, where the distinction between bedrockand surficial deposits is not clear, even if assigned astratigraphic name, a uniform practice should be estab-lished and documented and that definition followed forthe site or study.

Guidelines for the collection of data pertaining to bedrockand surficial deposits are presented in chapter 6.

Engineering Classification of GeologicMaterials

General

Geologic classification of materials as surficial deposits orbedrock is insufficient for engineering purposes. Usually,surficial deposits are described as soil for engineeringpurposes, and most bedrock is described as rock; however,there are exceptions. Contract documents often classifystructure excavations as to their ease of excavation. Also,classification systems for tunneling in geologic materialshave been established.

Classification as Soil or Rock

In engineering applications, soil may be defined as gener-ally unindurated accumulations of solid particlesproduced by the physical and/or chemical disintegrationof bedrock and which may or may not contain organicmatter. Surficial deposits, such as colluvium, alluvium,or residual soil, normally are described using Recla-

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mation Procedure 5005, Determining Unified SoilClassification (Visual Method) [3]. American Society forTesting and Materials (ASTM) Standards D2487-85,Standard Test Method for Classification of Soils forEngineering Purposes or D2488-84, Standard Practice forDescription and Identification of Soils (Visual-ManualProcedure), which are based on Reclamation 5000 and5005 [3] also may be used. Instructions for thedescription and classification of soils are provided inchapter 3. Chapter 11 provides instructions for thelogging of soils in geologic explorations. In some cases,partially indurated soils may have rock-likecharacteristics and may be described as rock.

The United States Department of Agriculture (USDA)Agricultural Soils Classification System is used for drain-age and land classification and some detailed Quaternarygeology studies, such as for seismotectonic investigations.

Rock as an engineering material is defined as lithified orindurated crystalline or noncrystalline materials. Rockis encountered in masses and as large fragments whichhave consequences to design and construction differingfrom those of soil. Field classification of igneous,metamorphic, sedimentary, and pyroclastic rocks areprovided in chapter 4. Chapter 4 also presents asuggested description format, standard descriptors, anddescriptive criteria for the lithologic and engineeringphysical properties of rock. Nonindurated materials with-in bedrock should be described using the Reclamation soilclassification standards and soil descriptors presented inchapter 3. Engineering and geological classification anddescription of discontinuities which may be present ineither soil or rock are discussed in chapter 5.

TERMINOLOGY

7

Classification of Excavations

The engineering classification of excavation as either rockexcavation or common excavation or the definition of rockin specifications must be evaluated and determined foreach contract document and should be based on thephysical properties of the materials (induration and othercharacteristics), quantity and method of excavation, andequipment constraints and size.

Classification of Materials for Tunneling

Classification systems are used for data reports, speci-fications, and construction monitoring for tunnel designsand construction. When appropriate for design, otherload prediction and classification systems may be usedsuch as the Q system developed by the Norwegian Geo-technical Institute (NGI), Rock Mass Rating SystemGeomechanics Classification (RMR), and Rock StructureRating (RSR).

The following terms for the classification of rock [4] fortunneling are suggested:

• Intact rock contains neither joints nor hairline cracks.If it breaks, it breaks across sound rock. On account ofdamage to the rock due to blasting, spalls may drop offthe roof several hours or days after blasting. This isknown as spalling condition. Hard, intact rock may alsobe encountered in the popping condition (rock burst)involving the spontaneous and violent detachment of rockslabs from sides or roof.

• Stratified rock consists of individual strata with littleor no resistance against separation along the boundaries

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between strata. The strata may or may not be weakenedby transverse joints. In such rock, the spalling conditionis quite common.

• Moderately jointed rock contains joints and hairlinecracks, but the blocks between joints are locally growntogether or so intimately interlocked that vertical wallsdo not require lateral support. In rocks of this type, boththe spalling and the popping condition may beencountered.

• Blocky and seamy rock consists of chemically intactor almost intact rock fragments which are entirelyseparated from each other and imperfectly interlocked.In such rock, vertical walls may require support.

• Crushed but chemically intact rock has the char-acter of a crusher run. If most or all of the fragments areas small as fine sand and no recementation has takenplace, crushed rock below the water table exhibits theproperties of a water-bearing sand.

• Squeezing rock slowly advances into the tunnelwithout perceptible volume increase. Movement is theresult of overstressing and plastic failure of the rock massand not due to swelling.

• Swelling rock advances into the tunnel chiefly on ac-count of expansion. The capacity to swell is generallylimited to those rocks which contain smectite, amontmorillonite group of clay minerals, with a highswelling capacity.

Although the terms are defined, no distinct boundariesexist between rock categories. Wide variations in thephysical properties of rocks classified by these terms androck loading are often the case.

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Table 2-1, Ground behavior for earth tunneling with steelsupports, provides ground classifications for differentreactions of ground to tunneling operations.

Application and Use of Standard Indexes,Terminology, and Descriptors

This section and subsequent chapters 3, 4, and 5 providedefinitions and standard descriptors for physicalproperties of geologic materials which are of engineeringsignificance. The ability of a foundation to support loadsimposed by various structures depends primarily on thedeformability and stability of the foundation materialsand the groundwater conditions. Description of geologicand some manmade materials (embankments) is one ofthe geologist's direct contributions to the design process.Judgment and intuition alone are not adequate for thesafe and economical design of large complex engineeringprojects. Preparation of geologic logs, maps and sections,and detailed descriptions of observed material is the leastexpensive aspect and most continuous record of a sub-surface exploration program. It is imperative to developdesign data properly because recent advances in soil androck mechanics have enabled engineers and geologists toanalyze more conditions than previously possible. Theseanalyses rely on physical models that are developedthrough geologic observation and which must bedescribed without ambiguity.

The need for standard geologic terminology, indexes, anddescriptors has long been recognized because it isimportant that design engineers and contractors, aswell as geologists, be able to have all the facts and quali-tative information as a common basis to arrive atconclusions from any log of exploration, report, or draw-ing, regardless of the preparer. Geologic terminology,

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Table 2-1.— Ground behavior for earth tunneling with steel supports (after Terzaghi, 1977) [4]

Ground classification Reaction of ground to tunneling operation

HARD Tunnel heading may be advanced without roof support.

FIRM Ground in which a roof section of a tunnel can be leftunsupported for several days without inducing aperceptible movement of the ground.

RAVELING Chunks or flakes of soil begin to drop out of roof at somepoint during the ground-movement period.

SLOW RAVELING The time required to excavate 5 feet of tunnel andinstall a rib set and lagging in a small tunnel is about6 hours. Therefore, if the stand-up time of ravelingground is more than 6 hours, by using ribs and lagging,the steel rib sets may be spaced on 5-foot centers. Sucha soil would be classed as slow raveling.

FAST RAVELING If the stand-up time is less than 6 hours, set spacingmust be reduced to 4 feet, 3 feet, or even 2 feet. If thestand-up time is too short for these smaller spacings,liner plates should be used, either with or without ribsets, depending on the tunnel size.

SQUEEZING Ground slowly advances into tunnel without any signsof fracturing. The loss of ground caused by squeeze andthe resulting settlement of the ground surface can besubstantial.

SWELLING Ground slowly advances into the tunnel partly or chieflybecause of an increase in the volume of the ground. Thevolume increase is in response to an increase of watercontent. In every other respect, swelling ground in atunnel behaves like a stiff non-squeezing, or slowlysqueezing, non-swelling clay.

RUNNING The removal of lateral support on any surface rising atan angle of more than 34E (to the horizontal) isimmediately followed by a running movement of the soilparticles. This movement does not stop until the slopeof the moving soil becomes roughly equal to 34E• ifrunning ground has a trace of cohesion, then the run ispreceded by a brief period of progressive raveling.

VERY SOFT SQUEEZING Ground advances rapidly into tunnel in a plastic flow.

FLOWING Ground supporting a tunnel cannot be classified asflowing ground unless water flows or seeps through ittoward the tunnel. For this reason, a flowing conditionis encountered only in free air tunnels below thewatertable or under compressed air when the pressureis not high enough in the tunnel to dry the bottom. Asecond prerequisite for flowing is low cohesion of soil.Therefore, conditions for flowing ground occur only ininorganic silt, fine silty sand, clean sand or gravel, orsand-and-gravel with some clay binder. Organic siltmay behave either as a flowing or as a very soft,squeezing ground.

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standard descriptors, and descriptive criteria for physicalproperties have been established so that geologic data arerecorded uniformly, objectively, consistently, and accu-rately. The application of these indexes, terminology,descriptors, and various manual and visual tests must beapplied consistently by all geologists for each particularproject. The need to calibrate themselves with others per-forming similar tests and descriptions is imperative toensure that data are recorded and interpreted uniformly.The use of these standard descriptors and terminology isnot intended to replace the geologist's or engineer's indi-vidual judgment. The established standard qualitativeand quantitative descriptors will assist newly employedgeologists and engineers in understanding Reclamationterminology and procedures, permit better analysis ofdata, and permit better understanding by other geologistsand engineers, and by contractors. Most of the physicaldimensions established for the descriptive criteria per-taining to rock and discontinuity characteristics havebeen established using a 1-3-10-30-100 progression forconsistency, ease of memory, conversion from English tometric (30 millimeters [mm] = 0.1 foot [ft]) units, and toconform to many established standards used throughoutthe world. Their use will improve analysis, design andconstruction considerations, and specifications prepara-tion. Contractor claims also should be reduced due toconsistent and well defined terminology and descriptors.

Alphanumeric values for many physical properties havebeen established to enable the geotechnical engineer andengineering geologist to readily analyze the geologic data.These alphanumeric descriptors also will assist in compi-lation of data bases and computer searches when usingcomputer generated logs. For consistency, the lower thealphanumeric value, the more favorable the conditionbeing described. However, alphanumeric codes do notreplace a complete description of what is observed. A

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complete description provides physical dimensionsincluding a range and/or average in size, width, length orother physical property, and/or descriptive information.

It is important to start physical testing of the geologicmaterials as early as possible in an exploration program;descriptors alone are not sufficient. As data are inter-preted, index properties tests can be performed in thefield to obtain preliminary strength estimates for repre-sentative materials or materials requiring special con-sideration. The scope of such a program must be tailoredto each feature. Tests which are to be considered includepoint load, Schmidt hammer, sliding tilt, and pocketTorvane or penetrometer tests. These tests are describedbriefly in chapters 4 and 5. Indexes to be consideredinclude rock hardness, durability (slaking), and RockQuality Designation (RQD). The type of detailed labora-tory studies can be formulated better and the amount ofsampling and testing may be reduced if results from fieldtests are available.

Units of Measurements for Geologic Logs ofExploration, Drawings, and Reports

Metric Units

For metric specifications and studies, metric (Interna-tional System of Units) should be used from the start ofwork if possible. Logs of exploration providing depthmeasurements should be given to tenths or hundredths ofmeters. All linear measurements such as particle orcrystal sizes, ranges or averages in thickness, openness,and spacing, provided in descriptor definitions inchapters 3, 4, and 5, should be expressed in millimetersor meters as appropriate. Pressures should be given inpascals (Pa). Permeability (hydraulic conductivity)

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should be in centimeters per second (cm/s). In somecases, local usage of other units such as kilogram persquare centimeter (kg/cm2) for pressure or centimeters(cm) may be used.

English Units (U.S. Customary)

For specifications and studies using United States cus-tomary or English units (inch-pound), depth measure-ments should be given in feet and tenths of feet. Rangesin thickness, openness, and spacing, are preferred intenths or hundredths of a foot, or feet as shown in thedescriptor definitions in chapters 4 and 5. Pressureshould be in pound-force per square inch (lbf/in2 orPSI). Permeability should be in feet per year (ft/yr). Theexceptions to the use of English units (inch-pound) are fordescribing particle and grain sizes and age dating.Particle sizes for soils classified using American Societyfor Testing and Materials/Unified Soil ClassificationSystems (ASTM/USCS) should be in metric units on alllogs of exploration. For description of bedrock, particleand grain sizes are to be in millimeters.

Age Dates

If age dates are abbreviated, the North American Strati-graphic Commission (NASC) recommends ka for thousandyears and Ma for million years, but my or m.y. (millionyears) for time intervals (for example, ". . . during aperiod of 40 my . . .").

Conversion of Metric and English (U.S. Customary)Units

Table 2-2 provides many of the most frequently usedmetric and English (U.S. Customary) units forgeotechnical work.

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Table 2-2.— Useful conversion factors— metric and English units (inch-pound)

To convert units in column 1 to units in column 4, multiply column 1 by the factor in column 2.To convert units in column 4 to units in column 1, multiply column 4 by the factor in column 3.

Column 1 Column 2 Column 3 Column 4

Lengthinch (in) 2.540 X 10 1 3.937 X 10-2 millimeter (mm)hundredths of feet 3.048 X 102 3.281 X 10 -3 millimeter (mm)foot (ft) 3.048 X 10 -1 3.281 meter (m)mile (mi) 1.6093 6.2137 X 10-1 kilometer (km)

Areasquare inch (in2) 6.4516 X 10-4 1.550 X 10-3 square meter (m2)square foot (ft2) 9.2903 X 10 -2 1.0764 X 101 square meter (m2)acre 4.0469 X 10 -1 2.4711 hectaresquare mile (mi2) 0.386 X 10 -2 259.0 hectares

Volumecubic inch (in3) 1.6387 X 10-2 6.102 X 10-2 cubic centimeter (cm2)cubic feet (ft3) 2.8317 X 10-2 3.5315 x 101 cubic meter (m3)

cubic yard (yd3) 7.6455 X 101 1.3079 cubic meter (ms)cubic feet (ft3) 7.4805 1.3368 x 10-1 gallon (gal)gallon (gal) 3.7854 2.6417 X 10-1 liter (L)acre-feet (acre-ft) 1.2335 X 103 8.1071 X 10 -4 cubic meter (m3)

Flowgallon per minute (gal/min) 6.309 X 10-2 1.5850 X 101 liter per second (L/s)cubic foot per second (ft3/s) 4.4883 X 102 2.228 X 10-3 gallons per minute (gal/min)

1.9835 5.0417 X 10-1 acre-feet per day (acre-ft/d)cubic foot per second (ft3/s) 7.2398 X 102 1.3813 X 10-3 acre-feet per year (acre-ft/yr)

2.8317 X 10-2 3.531 X 101 cubic meters per second (m3/s)8.93 X 105 1.119 X 10-6 cubic meters per year (m3/yr)

Permeabilityk, feet/year 9.651 X 10-7 1.035 X 106 k, centimeter per second

(cm/sec)Density

pound-mass per cubic foot 1.6018 X 101 6.2429 X 10-2 kilogram per cubic meter (lb/ft3) (kg/m3)

Unit Weightpound force per cubic foot 0.157 6.366 kilonewton per cubic meter (lb/ft3) (kN/m3)

Pressurepounds per square inch (psi) 7.03 X 10-2 1.4223 X 101 kilogram per square

centimeter (kg/cm3)6.8948 0.145 kiloPascal (kPa)

Forceton 8.89644 1.12405 X 10-1 kilonewton (kN)pound-force 4.4482 X 10-3 224.8096 kilonewton (kN)

Temperature EC = 5/9 (EF - 32 E) EF = (9/5 EC) + 32 E

GroutingMetric bag cement per meter 3.0 0.33 U.S. bag cement per footWater:cement ratio 0.7 1.4 water:cement ratio by weight by volumepounds per square inch 0.2296 4.3554 kilogram per square centi- per foot meter per meter (kg/cm2/m)k, feet/year 0.1 10 Lugeon

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BIBLIOGRAPHY

[1] The Glossary of Geology, 4th edition, AmericanGeologic Institute, Alexandria, VA, 1997.

[2] The American Association of Petroleum GeologistsBulletin, v. 67, No. 5, pp. 841-875, May 1983.

[3] Bureau of Reclamation, Earth Manual, 3rd edition,part 2, Denver, CO, 1990.

[4 ] Proctor, Robert V., and Thomas L. White, "EarthTunneling with Steel Supports," CommercialShearing, Inc., 1775 Logan Avenue, Youngstown, OH44501, 1977.

Chapter 3

ENGINEERING CLASSIFICATIONAND DESCRIPTION OF SOIL

General

Application

Soil investigations conducted for engineering purposesthat use test pits, trenches, auger and drill holes, or otherexploratory methods and surface sampling and mappingare logged and described according to the Unified SoilClassification System (USCS) as presented in Bureau ofReclamation (Reclamation) standards USBR 5000 [1] and5005 [2]. Also, bedrock materials with the engineeringproperties of soils are described using these standards(chapter 2). The Reclamation standards are consistentwith the American Society for Testing Materials (ASTM)Designation D2487 and 2488 on the USCS system [3,4].Descriptive criteria and terminology presented areprimarily for the visual classification and manual tests.The identification portion of these methods in assigninggroup symbols is limited to soil particles smaller than3 inches (in) (75 millimeters [mm]) and to naturallyoccurring soils. Provisions are also made to estimate thepercentages of cobbles and boulders by volume. Thisdescriptive system may also be applied to shale, shells,crushed rock, and other materials if done according tocriteria established in this section. Chapter 11 addressesthe logging format and criteria for describing soil in testpits, trenches, auger holes, and drill hole logs.

All investigations associated with land classification forirrigation suitability, data collection, analyses of soiland substratum materials related to drainage inves-tigations, and Quaternary stratigraphy (e.g., fault andpaleoflood studies) are logged and described using the

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U.S. Department of Agriculture terminology outlined inappendix I to Agriculture Handbook No. 436 (SoilTaxonomy), dated December 1975 [5].

All soil classification descriptions for particle sizes lessthan No. 4 sieve size are to be in metric units.

Performing Tests and Obtaining DescriptiveInformation

The USCS groups soils according to potential engineeringbehavior. The descriptive information assists with esti-mating engineering properties such as shear strength,compressibility, and permeability. These guidelines canbe used not only for identification of soils in the field butalso in the office, laboratory, or wherever soil samples areinspected and described.

Laboratory classification of soils [1] is not alwaysrequired but should be performed as necessary and can beused as a check of visual-manual methods. The descrip-tors obtained from visual-manual inspection providevaluable information not obtainable from laboratorytesting. Visual-manual inspection is always required. The visual-manual method has particular value inidentifying and grouping similar soil samples so that onlya minimum number of laboratory tests are required forpositive soil classification. The ability to identify anddescribe soils correctly is learned more readily under theguidance of experienced personnel, but can be acquired bycomparing laboratory test results for typical soils of eachtype with their visual and manual characteristics. Whenidentifying and describing soil samples from an area orproject, all the procedures need not be followed. Similarsoils may be grouped together; for example, one sampleshould be identified and described completely, with theothers identified as similar based on performing only afew of the identification and descriptive procedures.

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Descriptive information should be evaluated and reportedon every sample.

The sample used for classification must be representativeof the stratum and be obtained by an appropriate ac-cepted or standard procedure. The origin of the materialmust be correctly identified. The origin description maybe a boring number and depth and/or sample number, ageologic stratum, a pedologic horizon, or a locationdescription with respect to a permanent monument, agrid system, or a station number and offset.

Terminology for Soils

Definitions for soil classification and description are inaccordance with USBR 3900 Standard Definitions ofTerms and Symbols Relating to Soil Mechanics [6]:

Cobbles and boulders—particles retained on a 3-inch(75-mm) U.S. Standard sieve. The following terminologydistinguishes between cobbles and boulders:

• Cobbles—particles of rock that will pass a 12-in(300-mm) square opening and be retained on a 3-in(75-mm) sieve.

• Boulders—particles of rock that will not pass a12-in (300-mm) square opening.

Gravel—particles of rock that will pass a 3-in (75-mm)sieve and is retained on a No. 4 (4.75-mm) sieve. Gravelis further subdivided as follows:

• Coarse gravel—passes a 3-in (75-mm) sieve and isretained on 3/4-in (19-mm) sieve.

• Fine gravel—passes a ¾-in (19-mm) sieve and isretained on No. 4 (4.75-mm) sieve.

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Sand—particles of rock that will pass a No. 4 (4.75-mm)sieve and is retained on a No. 200 (0.075-mm or 75-micro-meter [µm]) sieve. Sand is further subdivided as follows:

• Coarse sand—passes No. 4 (4.75-mm) sieve and isretained on No. 10 (2.00-mm) sieve.

• Medium sand—passes No. 10 (2.00-mm) sieve andis retained on No. 40 (425-µm) sieve.

• Fine sand—passes No. 40 (425-µm) sieve and isretained on No. 200 (0.075-mm or 75-µm) sieve.

Clay—passes a No. 200 (0.075-mm or 75-µm) sieve. Soilhas plasticity within a range of water contents and hasconsiderable strength when air-dry. For classification,clay is a fine-grained soil, or the fine-grained portion of asoil, with a plasticity index greater than 4 and the plot ofplasticity index versus liquid limit falls on or above the"A"-line (figure 3-5, later in this chapter).

Silt—passes a No. 200 (0.075-mm or 75-µm) sieve. Soilis nonplastic or very slightly plastic and that exhibitslittle or no strength when air-dry is a silt. Forclassification, a silt is a fine-grained soil, or the fine-grained portion of a soil, with a plasticity index less than4 or the plot of plasticity index versus liquid limit fallsbelow the "A"-line (figure 3-5).

Organic clay—clay with sufficient organic content to in-fluence the soil properties is an organic clay. For classifi-cation, an organic clay is a soil that would be classified asa clay except that its liquid limit value after oven-dryingis less than 75 percent of its liquid limit value beforeoven-drying.

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Organic silt—silt with sufficient organic content to in-flu-ence the soil properties. For classification, an organicsilt is a soil that would be classified as a silt except thatits liquid limit value after oven-drying is less than75 percent of its liquid limit value before oven-drying.

Peat—material composed primarily of vegetable tissuesin various stages of decomposition, usually with an or-ganic odor, a dark brown to black color, a spongy con-sistency, and a texture ranging from fibrous to amor-phous. Classification procedures are not applied to peat.

Classifications of Soils

Group Names and Group Symbols

The identification and naming of a soil based on resultsof visual and manual tests is presented in a subsequentsection. Soil is given an identification by assigning agroup symbol(s) and group name. Important informationabout the soil is added to the group name by the term"with" when appropriate (figures 3-1, 3-2, 3-3, 3-4). Thegroup name is modified using “with” to stress othersignificant components in the soil.

Figure 3-2 is a flow chart for assigning typical names andgroup symbols for inorganic fine-grained soils; figure 3-3is a flow chart for organic fine-grained soils; figure 3-4 isa flow chart for coarse-grained soils. Refer to tables 3-1and 3-2 for the basic group names without modifiers. Ifthe soil has properties which do not distinctly place it in

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FINE-GRAINED SOILS

Sandy BASIC

GROUP NAME

with sand

Gravelly with gravel

COARSE-GRAINED SOILS

with silt BASIC

GROUP NAME

with sand

with clay with gravel

Figure 3-1.—Modifiers to basic soil group names(for visual classification).

a specific group, borderline symbols may be used. Thereis a distinction between dual symbols and borderlinesymbols.

Dual Symbols.—Dual symbols separated by a hyphenare used in laboratory classification of soils and in visualclassification when soils are estimated to contain10 percent fines. A dual symbol (two symbols separatedby a hyphen, e.g., GP-GM, SW-SC, CL-ML) should beused to indicate that the soil has the properties of aclassification where two symbols are required. Dual sym-bols are required when the soil has between 5 and12 percent fines from laboratory tests (table 3-2), or finesare estimated as 10 percent by visual classification. Dualsymbols are also required when the liquid limit andplasticity index values plot in the CL-ML area of theplasticity chart (figure 3-5, later in this chapter).

SO

IL

23 Figure 3-2.—Flow chart for inorganic fine-grained soils, visual method.

FIE

LD

MA

NU

AL

24

Figure 3-3.—Flow chart for organic soils, visual method.

SO

IL

25 Figure 3-4.—Flow chart for coarse-grained soils, visual method.

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Table 3-1.—Basic group names, primary groups

Coarse-grained soils Fine-grained soils

GW - Well graded gravelGP - Poorly graded gravelGM - Silty gravelGC - Clayey gravel sandSW - Well graded sandSP - Poorly graded sandSM - Silty sandSC - Clayey sand

CL - Lean clayML - SiltOL - Organic clay (on or

above A-line- Organic silt (below A-line)

CH - Fat clayMH - Elastic siltOH - Organic clay (on or above

A-line)- Organic silt (below A-line)

Basic group name—hatched area on Plasticity Chart(Laboratory Classification)

CL-ML - Silty clayGC-GM - Silty, clayey gravelSC-SM - Silty, clayey sand

Table 3-2.—Basic group names, 5 to 12 percent fines(Laboratory Classification)

GW-GM - Well graded gravel with siltGW-GC - Well graded gravel with clay (if fines =

CL-ML) Well graded gravel with silty clayGP-GM - Poorly graded gravel with siltGP-GC - Poorly graded gravel with clay (if fines =

CL-ML) Poorly graded gravel with silty claySW-SM - Well graded sand with siltSW-SC - Well graded sand with clay (if fines = CL-ML)

Well graded sand with silty claySP-SM - Poorly graded sand with siltSP-SC - Poorly graded sand with clay (if fines =

CL-ML) Poorly graded sand with silty clay

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Borderline Symbols.—Borderline symbols are usedwhen soil properties indicate the soil is close to anotherclassification group. Two symbols separated by a slash,such as CL/CH, SC/CL, GM/SM, CL/ML, should be usedto indicate that the soil has properties that do notdistinctly place the soil into a specific group. Because thevisual classification of soil is based on estimates ofparticle-size distribution and plasticity characteristics, itmay be difficult to clearly identify the soil as belonging toone category. To indicate that the soil may fall into oneof two possible basic groups, a borderline symbol may beused with the two symbols separated by a slash. Aborderline classification symbol should not be usedindiscriminately. Every effort should be made first toplace the soil into a single group. Borderline symbols canalso be used in laboratory classification, but lessfrequently.

A borderline symbol may be used when the percentage offines is visually estimated to be between 45 and 55 per-cent. One symbol should be for a coarse-grained soil withfines and the other for a fine-grained soil. For example:GM/ML, CL/SC.

A borderline symbol may be used when the percentage ofsand and the percentage of gravel is estimated to beabout the same, for example, GP/SP, SC/GC, GM/SM. Itis practically impossible to have a soil that would have aborderline symbol of GW/SW. However, a borderlinesymbol may be used when the soil could be either wellgraded or poorly graded. For example: GW/GP, SW/SP.

A borderline symbol may be used when the soil could beeither a silt or a clay. For example: CL/ML, CH/MH,SC/SM.

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A borderline symbol may be used when a fine-grained soilhas properties at the boundary between a soil of low com-pressibility and a soil of high compressibility. Forexample: CL/CH, MH/ML.

The order of the borderline symbol should reflect simi-larity to surrounding or adjacent soils. For example, soilsin a borrow area have been predominantly identified asCH. One sample has the borderline symbol of CL andCH. To show similarity to the adjacent CH soils, theborderline symbol should be CH/CL.

The group name for a soil with a borderline symbolshould be the group name for the first symbol, except for:

CL/CH - lean to fat clayML/CL - clayey siltCL/ML - silty clay

Preparation for Identification and VisualClassification

A usually dark-brown to black material composedprimarily of vegetable tissue in various stages of decom-position with a fibrous to amorphous texture and organicodor is a highly organic soil and classified as peat, PT.Plant forms may or may not be readily recognized. Ingeneral, the greater the organic content, the greater thewater content, void ratio, and compressibility of peat. Organic soils are often identified by their odor. To checkfor organic content, the soil can be subjected to thelaboratory classification liquid limit test criteria. Organicsoils can also be identified through laboratory loss-on-ignition tests. Materials identified as peat are not sub-jected to the following identification procedures.

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Soil identification procedures are based on the minus 3-in(75-mm) particle sizes. All plus 3-in (75-mm) particlesmust be manually removed from a loose sample, ormentally for an intact sample, before classifying the soil. Estimate and note the percent by volume of the plus 3-in(75-mm) particles, both the percentage of cobbles and thepercentage of boulders.

Note: Because the percentages of the particle-size distribution in laboratory classification(ASTM: D 2487) are by dry weight and theestimates of percentages for gravel, sand, andfines are by dry weight, the description shouldstate that the percentages of cobbles andboulders are by volume, not weight, for visualclassification. Estimation of the volume of cob-bles and boulders is not an easy task. Accurateestimating requires experience. While exper-ienced loggers may be able to successfullyestimate the minus 3-in fraction to within5 percent, the margin of error could be larger foroversize particles. Estimates can be confirmedor calibrated with large scale field gradationtests on critical projects. Given the large pos-sible errors in these estimates, the estimatesshould not be used as the sole basis for design ofprocessing equipment. Large scale gradationsshould be obtained as part of the process plantdesigns.

In most cases, the volume of oversize is estimated inthree size ranges, 3 to 5, 5 to 12, and 12 inches andlarger. Cobbles are often divided into two size ranges,because in roller compacted fill of 6-in compacted liftthickness, the maximum size cobble is 5 inches. If thepurpose of the investigation is not for roller compactedfill, a single size range for cobbles can be estimated.

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Estimate and note the percentage by dry weight of thegravel, sand, and fines of the fraction of the soil smallerthan 3 in (75-mm). The percentages are estimated to theclosest 5 percent. The percentages of gravel, sand, andfines must add up to 100 percent, excluding traceamounts. The presence of a component not in sufficientquantity to be considered 5 percent in the minus 3-in(75-mm) portion, is indicated by the term "trace." For ex-ample: trace of fines. A trace is not considered in thetotal of 100 percent for the components.

The first step in the identification procedure is todetermine the percentages of fine-grained and coarse-grained materials in the sample. The soil is fine-grainedif it contains 50 percent or more fines. The soil is coarse-grained if it contains less than 50 percent fines.Procedures for the description and classification of thesetwo preliminary identification groups follow.

Procedures and Criteria for Visual Classificationof Fine-Grained Soils

Select a representative sample of the material forexamination and remove particles larger than theNo. 40 sieve (medium sand and larger) until a specimenequivalent to about a handful of representative materialis available. Use this specimen for performing theidentification tests.

Identification Criteria for Fine-Grained Soils.—Thetests for identifying properties of fines are dry strength,dilatency, toughness, and plasticity.

1. Dry strength.—Select from the specimen enoughmaterial to mold into a ball about 1 in (25 mm) indiameter. Mold or work the material until it has theconsistency of putty, adding water if necessary.

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31

From the molded material, make at least three testspecimens. Each test specimen should be a ball ofmaterial about ½ in (12 mm) in diameter. Allow thetest specimens to dry in air or sun, or dry by artificialmeans, as long as the temperature does not exceed60 degrees Centigrade (EC). In most cases, it will benecessary to prepare specimens and allow them todry over night. If the test specimen contains naturaldry lumps, those that are about ½ in (12 mm) indiameter may be used in place of molded balls. (Theprocess of molding and drying usually produceshigher strengths than are found in natural dry lumpsof soil). Test the strength of the dry balls or lumps bycrushing them between the fingers and note thestrength as none, low, medium, high, or very highaccording to the criteria in table 3-3. If natural drylumps are used, do not use the results of any of thelumps that are found to contain particles of coarsesand.

Table 3-3.—Criteria for describing dry strength

None The dry specimen crumbles with merepressure of handling.

Low The dry specimen crumbles with somefinger pressure.

Medium The dry specimen breaks into pieces orcrumbles with considerable fingerpressure.

High The dry specimen cannot be broken withfinger pressure. Specimen will break intopieces between thumb and a hard surface.

Very High The dry specimen cannot be brokenbetween thumb and a hard surface.

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The presence of high-strength, water-soluble cement-ing materials, such as calcium carbonate, may causeexceptionally high dry strengths. The presence ofcalcium carbonate can usually be detected from theintensity of the reaction with dilute hydrocloric acid(HCl). Criteria for reaction with HCl are presentedin a subsequent paragraph.

2. Dilatancy.—Select enough material from thespecimen to mold into a ball about ½ in (12 mm) indiameter. Mold the material, adding water if neces-sary, until it has a soft, but not sticky, consistency.Smooth the soil ball in the palm of one hand with theblade of a knife or spatula. Shake horizontally (thesoil ball), striking the side of the hand vigorouslyagainst the other hand several times. Note thereaction of the water appearing on the surface of thesoil. Squeeze the sample by closing the hand orpinching the soil between the fingers and notereaction as none, slow, or rapid according to thecriteria in table 3-4. The reaction criteria are thespeeds with which water appears while shaking anddisappears while squeezing.

Table 3-4.—Criteria for describing dilatancy

None No visible change in the specimen.

Slow Water slowly appears on the surface of thespecimen during shaking and does not disap-pear or disappears slowly upon squeezing.

Rapid Water quickly appears on the surface of thespecimen during shaking and disappearsupon squeezing.

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3. Toughness.—Following completion of thedilatancy test, the specimen is shaped into anelongated pat and rolled by hand on a smooth surfaceor between the palms into a thread about c in(3 mm) diameter. (If the sample is too wet to rolleasily, spread the sample out into a thin layer andallow some water loss by evaporation). Fold thesample threads and reroll repeatedly until the threadcrumbles at a diameter of about c in (3 mm) whenthe soil is near the plastic limit. Note the timerequired to reroll the thread to reach the plasticlimit. Note the pressure required to roll the threadnear the plastic limit. Also, note the strength of thethread. After the thread crumbles, the pieces shouldbe lumped together and kneaded until the lumpcrumbles. Note the toughness of the material duringkneading.

Describe the toughness of the thread and lump aslow, medium, or high according to the criteria intable 3-5.

Table 3-5.—Criteria for describing toughness

Low Only slight pressure is required to roll thethread near the plastic limit. The threadand the lump are weak and soft.

Medium Medium pressure is required to roll thethread to near the plastic limit. The threadand the lump have medium stiffness.

High Considerable pressure is required to roll thethread to near the plastic limit. The threadand the lump have very high stiffness.

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4. Plasticity.—On the basis of observations madeduring the toughness test, describe the plasticity ofthe material according to the criteria given intable 3-6 (figure 3-5).

Table 3-6.—Criteria for describing plasticity

Nonplastic A 3-mm thread cannot be rolled at anywater content.

Low The thread can barely be rolled, and thelump cannot be formed when drier thanthe plastic limit.

Medium The thread is easy to roll, and not muchtime is required to reach the plastic limit.The thread cannot be rerolled afterreaching the plastic limit. The lumpcrumbles when drier than the plasticlimit.

High It takes considerable time rolling andkneading to reach the plastic limit. Thethread can be rolled several times afterreaching the plastic limit. The lump canbe formed without crumbling when drierthan the plastic limit.

After the dry strength, dilatency, toughness, andplasticity tests have been performed, decide onwhether the soil is an organic or an inorganic fine-grained soil.

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35 Figure 3-5.—Plasticity chart.

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Identification of Inorganic Fine-Grained Soils.—Classify the soils using the results of the manual testsand the identifying criteria shown in table 3-7. Possibleinorganic soils include lean clay (CL), fat clay (CH), silt(ML), and elastic silt (MH). The properties of an elasticsilt are similar to those for a lean clay. However, the siltwill dry quickly on the hand and have a smooth, silky feelwhen dry. Some soils which classify as MH according tothe field classification criteria are difficult to distinguishfrom lean clays, CL. It may be necessary to performlaboratory testing to ensure proper classification.

Table 3-7.—Identification of inorganic fine-grained soils from manual tests

Group symbol

Dry strength Dilatancy Toughness

ML None to low Slow to rapid

Low or thread cannot be formed

CL Medium to high None to slow Medium

MH Low to medium None to slow Low to medium

CH High to very high

None High

Some soils undergo irreversible changes upon air drying.These irreversible processes may cause changes inatterberg limits and other index tests. Even unsuspectedsoils such as low plasticity silts may have differingatterberg limits due to processes like disaggregation. When tested at natural moisture, clay particles cling tosilt particles resulting in less plasticity. When dried, theclay disaggregates, making a finer and more well gradedmix of particles with increased plasticity.

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For foundation studies of existing or new structures,natural moisture atterberg limits are preferred becausethe in-place material will remain moist. Natural mois-ture atterberg limits are especially important in criticalstudies, such as earthquake liquefaction evaluation ofsilts. On some foundation studies, such as for pumpingplant design, consolidation tests will govern, and naturalmoisture atterbergs are not required. For borrow studies,soils will likely undergo moisture changes, and naturalmoisture atterberg limits are not required unless unusualmineralogy is encountered.

Identification of Organic Fine-Grained Soils.—If thesoil contains enough organic particles to influence the soilproperties, classify the soil as an organic soil, OL or OH.Organic soils usually are dark brown to black and usuallyhave an organic odor. Often organic soils will changecolor, (black to brown) when exposed to air. Organic soilsnormally do not have high toughness or plasticity. Thethread for the toughness test is spongy. In some cases,further identification of organic soils as organic silts ororganic clays, OL or OH is possible. Correlations betweenthe dilatancy, dry strength, and toughness tests withlaboratory tests can be made to classify organic soils insimilar materials.

Modifiers for Fine-Grained Soil Classifications.—Ifbased on visual observation, the soil is estimated to have15 to 25 percent sand and/or gravel, the words "with sandand/or gravel" are added to the group name, for example,LEAN CLAY WITH SAND, (CL); SILT WITH SAND ANDGRAVEL (ML). Refer to figures 3-2 and 3-3. If the soil isvisually estimated to be 30 percent or more sand and/orgravel, the words "sandy" or "gravelly" are added to thegroup name. Add the word "sandy" if there appears to bemore sand than gravel. Add the word "gravelly" if thereappears to be more gravel than sand, for example,SANDY LEAN CLAY (CL); GRAVELLY FAT CLAY (CH);

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SANDY SILT (ML). Refer to figures 3-2 and 3-3. Notethat the Laboratory Classification follows differentcriteria.

Procedures and Criteria for Visual Classificationof Coarse-Grained Soils

A representative sample containing less than 50 percentfines is identified as a coarse-grained soil.

The soil is a gravel if the percentage by weight of gravelis estimated to be more than the percentage of sand.

The soil is a sand if the percentage by weight of sand isestimated to be more than the percentage of gravel.

The soil is a clean gravel or clean sand if the percentagesof fines are visually estimated to be 5 percent or less. Aclean gravel or sand is further classified by grain sizedistribution.

The soil is classified as a WELL GRADED GRAVEL(GW), or as a WELL GRADED SAND (SW), if a widerange of particle sizes and substantial amounts of theintermediate particle sizes are present. The soil isclassified as a POORLY GRADED GRAVEL (GP) or as aPOORLY GRADED SAND (SP) if the material ispredominantly one size (uniformly graded) or the soil hasa wide range of sizes with some intermediate sizesobviously missing (gap or skip graded).

The soil is identified as either gravel with fines or sandwith fines if the percentage of fines is visually estimatedto be 15 percent or more.

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Classify the soil as a CLAYEY GRAVEL (GC) or aCLAYEY SAND (SC) if the fines are clayey as determinedby the procedures for fine-grained soil identification.

Identify the soil as a SILTY GRAVEL (GM) or a SILTYSAND (SM) if the fines are silty as determined by the pro-cedures for fine-grained soil identification.

If the soil is visually estimated to contain 10 percentfines, give the soil a dual classification using two groupsymbols. The first group symbol should correspond to aclean gravel or sand (GW, GP, SW, SP), and the secondsymbol should correspond to a gravel or sand with fines(GC, GM, SC, SM). The typical name is the first groupsymbol plus "with clay" or "with silt" to indicate theplasticity characteristics of the fines. For example,WELL GRADED GRAVEL WITH CLAY (GW-GC);POORLY GRADED SAND WITH SILT (SP-SM). Refer tofigure 3-4.

If the specimen is predominantly sand or gravel but con-tains an estimated 15 percent or more of the othercoarse-grained constituent, the words "with gravel" or"with sand" are added to the group name. For example:POORLY GRADED GRAVEL WITH SAND (GP); CLAY-EY SAND WITH GRAVEL (SC). Refer to figure 3-4.

If the field sample contained any cobbles and/or boulders,the words "with cobbles" or "with cobbles and boulders"are added to the group name, for example, SILTY GRA-VEL WITH COBBLES (GM).

Abbreviated Soil Classification Symbols

If space is limited, an abbreviated system may be used toindicate the soil classification symbol and name such asin logs, data bases, tables, etc. The abbreviated system

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is not a substitute for the full name and descriptive infor-mation but can be used in supplementary presentations.The abbreviated system consists of the soil classificationsystem based on this chapter, with prefixes and suffixesas listed below.

Prefix: s = sandy g = gravellySuffix: s = with sand g = with gravel

c = with cobbles b = with boulders

The soil classification symbol is enclosed in parentheses.Examples are:

CL, sandy lean clay s(CL)SP-SM, poorly graded sand (SP-GM)g with silt and gravelGP, poorly graded gravel with sand, (GP)scb cobbles, and bouldersML, gravelly silt with sand g(ML)sc and cobbles

Description of the Physical Properties of Soil

Descriptive information for classification and reportingsoil properties such as angularity, shape, color, moistureconditions, and consistency are presented in the followingparagraphs.

Angularity

Angularity is a descriptor for coarse-grained materialsonly. The angularity of the sand (coarse sizes only),gravel, cobbles, and boulders, are described as angular,

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subangular, subrounded, or rounded as indicated by thecriteria in table 3-8. A range of angularity may be stated,such as: sub-rounded to rounded.

Table 3-8.—Criteria for describing angularity of coarse-grained particles

Angular Particles have sharp edges and relativelyplanar sides with unpolished surfaces.

Subangular Particles are similar to angular descriptionbut have rounded edges.

Subrounded Particles have nearly planar sides but well-rounded corners and edges.

Rounded Particles have smoothly curved sides and noedges.

Shape

Describe the shape of the gravel, cobbles, and boulders as“flat, elongated” or “flat and elongated” if they meet thecriteria in table 3-9. Indicate the fraction of the particlesthat have the shape, such as: one-third of gravel particlesare flat. If the material is to be processed or used asaggregate for concrete, note any unusually shapedparticles.

Color

Color is an especially important property in identifyingorganic soils and is often important in identifying othertypes of soils. Within a given locality, color may also beuseful in identifying materials of similar geologic units.Color should be described for moist samples. Note if color

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Table 3-9.—Criteria for describing particle shape

The particle shape is described as follows, where length,width, and thickness refer to the greatest, intermediate, andleast dimensions of a particle, respectively.

Flat Particles with width/thickness >3.

Elongated Particles with length/width >3.

Flat and Particles meet criteria for both flat and elongated elongated.

represents a dry condition. If the sample contains layersor patches of varying colors, this should be noted, andrepresentative colors should be described. The MunselColor System may be used for consistent colordescriptions.

Odor

Describe the odor if organic or unusual. Soils containinga significant amount of organic material usually havea distinctive odor of decaying vegetation. This is espe-cially apparent in fresh samples, but if the samples aredried, the odor often may be revived by heating a moist-ened sample. If the odor is unusual, such as that of apetroleum product or other chemical, the material shouldbe described and identified if known. The material maybe hazardous, and combustion or exposure should beconsidered.

Moisture Conditions

Describe the moisture condition as dry, moist, or wet, asindicated by the criteria in table 3-10.

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Table 3-10.—Criteria for describing moisturecondition

Dry Absence of moisture, dusty, dry to the touch.

Moist Damp but no visible water.

Wet Visible free water, usually soil is below watertable.

Reaction with HCl

Describe the reaction with HCl as none, weak, or strong,as indicated by the criteria in table 3-11. Calciumcarbonate is a common cementing agent. The reactionwith dilute hydrochloric acid is important in determiningthe presence and abundance of calcium carbonate.

Table 3-11.—Criteria for describing reaction with HCl

None No visible reaction.

Weak Some reaction, with bubbles forming slowly.

Strong Violent reaction, with bubbles forming immediately.

Consistency

Describe consistency (degree of firmness) for intact fine-grained soils as very soft, soft, firm, hard, or very hard, asindicated by the criteria in table 3-12. This observationis inappropriate for soils with significant amounts ofgravel. Pocket penetrometer or torvane testing may sup-plement this data.

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Table 3-12.—Criteria for describing consistency of in-place orundisturbed fine-grained soils

Very soft Thumb will penetrate soil more than 1 in (25 mm).

Soft Thumb will penetrate soil about 1 in (25 mm).

Firm Thumb will indent soil about 1/4 in (5 mm).

Hard Thumb will not indent soil but readily indented with thumbnail.

Very hard Thumbnail will not indent soil.

Cementation

Describe the cementation of intact soils as weak,moderate, or strong, as indicated by the criteria intable 3-13.

Table 3-13.—Criteria for describing cementation

Weak Crumbles or breaks with handling or littlefinger pressure.

Moderate Crumbles or breaks with considerable fingerpressure.

Strong Will not crumble or break with finger pressure.

Structure (Fabric)

Describe the structure of the soil according to criteriadescribed in table 3-14. The descriptors presented are forsoils only; they are not synonymous with descriptors forrock.

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Table 3-14.—Criteria for describing structure

Stratified Alternating layers of varying material orcolor; note thicknesses.

Laminated1 Alternating layers of varying material orcolor with layers less than 6 mm thick; notethicknesses.

Fissured1 Breaks along definite planes with littleresistance to fracturing.

Slickensided1 Fracture planes appear polished or glossy,sometimes striated.

Blocky1 Cohesive soil that can be broken down intosmall angular lumps which resist furtherbreakdown.

Lenses Inclusion of small pockets of different soils,such as small lenses of sand scatteredthrough a mass of clay; note thicknesses.

Homogeneous Same color and textural or structuralappearance throughout.

1 Do not use for coarse-grained soils with the exception of finesands which can be laminated.

Particle Sizes

For gravel and sand-size components, describe the rangeof particle sizes within each component as defined in theprevious terminology paragraph. Descriptive terms,sizes, and examples of particle sizes are shown intable 3-15.

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Table 3-15.—Particle sizes

Descriptiveterm Size

Familiar example withinthe size range

Boulder 300 mm or more Larger than a volleyball

Cobble 300 mm to 75 mm Volleyball - grapefruit -orange

Coarse gravel 75 mm to 20 mm Orange - grape

Fine gravel 20 mm to No. 4sieve (5 mm)

Grape - pea

Coarse sand No. 4 sieve toNo. 10 sieve

Sidewalk salt

Medium sand No. 10 sieve toNo. 40 sieve

Openings in windowscreen

Fine sand No. 40 sieve toNo. 200 sieve

Sugar - table salt, grainsbarely visible

Describe the maximum particle size found in the sample.For reporting maximum particle size, use the followingdescriptors and size increments:

Fine sandMedium sand Coarse sand5-mm increments from 5 mm to 75 mm25-mm increments from 75 mm to 300 mm100-mm increments over 300 mm

For example: "maximum particle size 35 mm""maximum particle size 400 mm"

If the maximum particle size is sand size, describe asfine, medium, or coarse sand; for example, maximum par-ticle size, medium sand.

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If the maximum particle size is gravel size, describe themaximum particle size as the smallest sieve opening thatthe particle would pass.

If the maximum particle size is cobble or boulder size,describe the maximum dimension of the largest particle.

Particle Hardness

Describe the hardness of coarse sand and larger particlesas hard, or state what happens when the particles are hitby a hammer; e.g., gravel-size particles fracture withconsiderable hammer blow, some gravel-size particlescrumble with hammer blow. Hard means particles do notfracture or crumble when struck with a hammer.Remember that the larger the particle, the harder theblow required to fracture it. A good practice is to describethe particle size and the method that was used todetermine the hardness.

Additional Descriptive Information

Additional descriptive information may include unusualconditions, geological interpretation or other classifi-cation methods, such as:

Presence of roots or root holes or other organicmaterial or debris;

Degree of difficulty in drilling or augering hole or ex-cavating a pit; or

Raveling or caving of the trench, hole, pit, or exposure;

or

Presence of mica or other predominant minerals.

A local or commercial name and/or a geologic interpreta-tion should be provided for the soil.

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A classification or identification of the soil according toother classification systems may be added.

Narrative Descriptions and Examples

The description should include the information shown intables 3-16 and 3-17, a checklist for the description ofsoils. Example descriptions follow.

Table 3-16.—Checklist for the description of soilclassification and identification

1.2.3.4.

5.

6.

7.8.9.

10.

11.

12.

13.14.15.

16.

Group name and symbolPercent gravel, sand, and/or finesPercent by volume of cobbles and bouldersParticle size

Gravel - fine, coarseSand - fine, medium, coarse

Particle angularity angular subangular subrounded roundedParticle shape flat elongated flat and elongatedMaximum particle size or dimensionHardness of coarse sand and larger particlesPlasticity of fines nonplastic low medium highDry strength none low medium high very highDilatancy none slow rapidToughness low medium highColor (when moist)Odor (if organic or unusual)Moisture dry moist wetReaction with HCL none weak strong

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Table 3-17.—Checklist for the description of in-place conditions

In-place conditions:

1.

2.

3.

4.5.

Consistency (fine-grained soils only) very soft soft firm hard very hardCementation weak moderate strongStructure stratified laminated fissured slickened lensed homogeneousGeologic interpretation and/or local name, if anyAdditional comments and description

Presence of roots or root holesPresence of mica, gypsum, etc.Surface coatingsCaving or sloughing of excavationExcavation difficulty

Example 1: CLAYEY GRAVEL WITH SAND AND COB-BLES (GC)—Approximately 50 percent fine to coarse,sub-rounded to subangular gravel; approximately30 percent fine to coarse, subrounded sand;approximately 20 per-cent fines with medium plasticity,high dry strength, no dilatancy, medium toughness; weakreaction with HCl; original field sample had about5 percent (by volume) subrounded cobbles, maximum size150 mm.

IN-PLACE CONDITIONS: firm, homogeneous, dry,brown.

GEOLOGIC INTERPRETATION: alluvial fan.

Abbreviated symbol is (GC)sc.

Example 2: WELL GRADED GRAVEL WITH SAND(GW)—Approximately 75 percent fine to coarse, hard,sub-angular gravel; approximately 25 percent fine to

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coarse, hard, subangular sand; trace of fines; maximumsize 75 mm, brown, dry; no reaction with HCl.

Abbreviated symbol is (GW)s

Example 3: SILTY SAND WITH GRAVEL (SM)—Ap-proximately 60 percent predominantly fine sand; approxi-mately 25 percent silty fines with low plasticity, low drystrength, rapid dilatancy, and low toughness; approxi-mately 15 percent fine, hard, subrounded gravel, a fewgravel-size particles fractured with hammer blow;maximum size 25 mm; no reaction with HCl.

IN-PLACE CONDITIONS: firm, stratified, and containslenses of silt 1- to 2-in thick, moist, brown to gray;in-place density was 106 pounds per cubic foot (lb/ft3), andin-place moisture was 9 percent.

GEOLOGIC INTERPRETATION: ALLUVIUM

Abbreviated symbol is (SM)g.

Example 4: ORGANIC SOIL (OL/OH)—Approximately100 percent fines with low plasticity, slow dilatancy, lowdry strength, and low toughness; wet, dark brown,organic odor, weak reaction with HCl.

Abbreviated symbol is (OL/OH).

Example 5: SILTY SAND WITH ORGANIC FINES(SM)—Approximately 75 percent fine to coarse, hard, sub-angular reddish sand, approximately 25 percent organicand silty dark-brown nonplastic fines with no drystrength and slow dilatancy; wet; maximum size, coarsesand; weak reaction with HCl.

Abbreviated symbol is (SM)

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Example 6: POORLY GRADED GRAVEL WITH SILT,SAND, COBBLES, AND BOULDERS (GP-GM)—Approx-imately 75 percent fine to coarse, hard, subrounded tosubangular gravel; approximately 15 percent fine, hard,subrounded to subangular sand; approximately 10 per-cent silty nonplastic fines; moist, brown; no reaction withHCl; original field sample had approximately 5 percent(by volume) hard, subrounded cobbles and a trace of hard,subrounded boulders with a maximum dimension of500 mm.

Abbreviated symbol is (GP-GM)scb.

Use of Soil Classification as Secondary Identification Method for Materials Other

Than Natural Soils

General

Materials other than natural soils may be classified andtheir properties identified and described using the sameprocedures presented in the preceding subsections. Thefollowing materials are not considered soils and shouldnot be given a primary USCS soil classification:

Partially lithified or poorly cemented materials

Shale ClaystoneSandstone SiltstoneDecomposed granite

Processed, manmade, or other materials

Crushed rock SlagCrushed sandstone ShellsCinders Ashes

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Identification criteria may be used for describing thesematerials, especially for describing particle sizes andshapes and identifying those materials which convert tosoils after field or laboratory processing. Description for-mat and classification for these materials are discussedindividually in the following paragraphs.

Partially Lithified or Cemented Materials

Partially lithified or poorly cemented materials may needto be classified because the material will be excavated,processed, or manipulated for use as a constructionmaterial. When the physical properties are to be deter-mined for these materials for classification, the materialmust be processed into a soil by grinding or slaking inwater (shale, siltstone, poorly indurated ash deposits).

The physical properties and resulting classificationdescribe the soil type as created by reworking the originalmaterial. Soil classifications can then be used as asecondary identification. However, the classificationsymbol and group name must be reported in quotationmarks in any 1ogs, tables, figures, and reports. Iflaboratory tests are performed on these materials, theresults must be reported as shown in figure 3-6.

An example of a written narrative for either a test pit orauger hole log based on visual classification is as follows:Symbol Description

Shale Fragments 3.4- to 7.8-foot (ft) Shale Fragments—Retrieved as 2- to 4-in pieces of shalefrom power auger hole, dry, brown,no reaction with HCl. After slakingin water for 24 hours, materialclassified as "SANDY CLAY (CH)"—

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Figure 3-6.—Sample of test results summary.

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Approximately 60 percent fines withhigh plasticity, high dry strength, nodilatancy and high toughness;approximately 35 percent fine tomedium, hard sand; approximately5 percent gravel-size pieces of shale.

Processed or Manmade Materials

Processed, manmade, or other materials are also used asconstruction materials, and classification can be used asa secondary identification. However, for these processedmaterials, the group name and classification symbol areto be within quotation marks. If laboratory tests areperformed on these materials, the results must bereported as shown in table 3-6.

An example of a written narrative for logs for visual clas-sification is as follows:

Symbol Description

CRUSHED ROCK Stockpile No. 3 CRUSHEDROCK— processed gravel and cob-bles from P.T. NO. 7; "POORLY GRADEDGRAVEL (GP)"—approximately90 percent fine, hard, angular,gravel-size particles; approximately10 percent coarse, angular, sand-size particles; dry, tan, no reactionwith HCl.

Special Cases for Classification

Some materials that require a classification and descrip-tion according to USBR 5000 [1] or USBR 5005 [2] shouldnot have a heading that is a classification group name.

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When these materials will be used in, or influence, designand construction, they should be described according tothe criteria for logs of test pits and auger holes and theclassification symbol and typical name placed in quota-tion marks similar to the previous discussion on second-ary identification method for materials other thannatural soils. The heading should be as follows:

TopsoilLandfillRoad surfacing Uncompacted or CompactedFill

For example:

Classification

Symbol Description

TOPSOIL 0.0-0.8 meter (m) TOPSOIL—would beclassified as "ORGANIC SILT (OL)."Approximately 80 percent fines with lowplasticity, slow dilatancy, low drystrength, and low toughness; approxi-mately 20 percent fine to medium sand;wet, dark brown, organic odor, weak reac-tion with HCl; roots present throughout.

Some material should be described but not given a classi-fication symbol or group name, such as landfill (trash,garbage, etc.) or asphalt road. All of the above listedterms are only examples; this is not a complete list. If theabove materials are not to be used and will not influencedesign or construction, only the basic term listed aboveneed be shown on the logs without a complete descriptionor classification.

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BIBLIOGRAPHY

[1] Bureau of Reclamation, U.S. Department of theInterior, USBR-5000, “Procedure for DeterminingUnified Soil Classification (Laboratory Method),”Earth Manual, Part II, 3rd edition, 1990.

[2] Bureau of Reclamation, U.S. Department of theInterior, USBR-5005, “Procedure for DeterminingUnified Soil Classification (Visual Method),” EarthManual, Part II, 3rd edition, 1990.

[3] American Society for Testing and Materials, ASTMD-2487, “Standard Classification of Soils forEngineering Purposes,” ASTM Annual Book ofStandards, Volume 04.08 on Soil and Rock,Section 4 - Construction, West Conshohocken, PA,1996.

[4] American Society for Testing and Materials, ASTMD-2488, “Standard Practice for Description andIdentification of soils (Visual-Manual Procedure),”ASTM Annual Book of Standards, Volume 04.08 onSoil and Rock, Section 4 - Construction, West Con-shohocken, PA, 1996.

[5] U.S. Department of Agriculture, Agriculture Hand-book No. 436, Appendix I (Soil Taxonomy), December1975.

[6] Bureau of Reclamation, U.S. Department of theInterior, USBR 3900, “Standard Definitions ofTerms and Symbols Relating to Soil Mechanics,”Earth Manual, Part II, 3rd edition, 1990.

Chapter 4

CLASSIFICATION OF ROCKS AND DESCRIPTION OF PHYSICAL

PROPERTIES OF ROCK

Introduction

Uniformity of definitions, descriptors, and identificationof rock units is important to maintain continuity ingeologic logs, drawings, and reports from a project withmultiple drilling sessions, different loggers and mappers.Also important is the recording of all significant observ-able parameters when logging or mapping. This chapterpresents a system for the identification and classificationof rocks and includes standard terminology anddescriptive criteria for physical properties of engineeringsignificance. The standards presented in this chaptermay be expanded or modified to fit project requirements.

Rock Classification

Numerous systems are in use for field and petrographicclassification of rocks. Many classifications requiredetailed petrographic laboratory tests and thin sections,while others require limited petrographic examinationand field tests. The Bureau of Reclamation (Reclamation)has adopted a classification system which is modifiedfrom R.B. Travis [1]. While not based entirely on fieldtests or field identification of minerals, many of theclassification categories are sufficiently broad that fieldidentification is possible. Even where differences in themineral constituents cannot be determined precisely inthe field, differences usually are not significant enough toaffect the engineering properties of the rock if classifiedsomewhat incorrectly by lithologic name. Detailedmineralogical identification and petrographicclassification can be performed on hand samples or coresamples submitted to a petrographic laboratory.

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If samples are submitted to a petrographic laboratory, thepetrographic classification generally will coincide with theclassification according to Travis. The petrographicigneous rock classifications are somewhat more preciseand include specialty rock types based upon mineral com-position, texture, and occurrence. For example, alamprophyric dike composed of green hornblendephenocrysts or clinopyroxene in the groundmass could beclassified as spessartite, whereas a lamprophyrecontaining biotite with or without clinopyroxene could beclassified as a kersantite. Sedimentary rockclassifications generally include grain size, type of cementor matrix, mineral composition in order of increasingamounts greater than 15 percent, and the rock type, suchas medium-grained, calcite-cemented, feldspathic-quartzose sandstone, and coarse- to fine-grained, lithic-feldspathic-quartzose gray-wacke with an argillaceous-ferruginous-calcareous matrix. Metamorphic rockclassifications include specific rock types based uponcrystal size, diagnostic accessory minerals, mineralogicalcomposition in increasing amounts greater than15 percent, and structure. Two examples of metamorphicrock descriptions are medium-grained, hornblende-biotiteschist, or fine- to medium-grained, garnetiferous,muscovite-chlorite-feldspar-quartz gneiss. The aboveclassification can be abbreviated by the deletion ofmineral names from the left to right as desired. Themineral type immediately preceding the rock name is themost diagnostic.

The term "quartzite” is restricted to a metamorphic rockonly. The sedimentary sandstone equivalent is termed a"quartz cemented quartzose sandstone."

Samples submitted to a petrographic laboratory should berepresentative of the in-place rock unit. For example, ifa granitic gneiss is sampled but only the granite portionsubmitted, the rock will be petrographically classified as

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59

a granite since the gneissic portion cannot be observed orsubstantiated by the thin section and hand specimen.Petrographic classifications can be related to theengineering properties of rock units and are important.

Geologic rock unit names should be simple, and generalrock names should be based on either field identification,existing literature, or detailed petrographic examination,as well as engineering properties. Overclassification isdistracting and unnecessary. For example, use "horn-blende schist" or "amphibolite" instead of "sericite-chlorite-calcite-hornblende schist." The term "granite"may be used as the rock name and conveys more to thedesigner than the petrographically correct term"nepheline-syenite porphyry." Detailed mineralogicaldescriptions may be provided in reports when describingthe various rock units and may be required to correlatebetween observations, but mineralogical classificationsare not desirable as a rock unit name unless the mineralconstituents or fabric are significant to engineeringproperties.

The classification for igneous, sedimentary, metamorphic,and pyroclastic rocks is shown on figures 4-1, 4-2, 4-3, and4-4, respectively. These figures are condensed andmodified slightly from Travis' classifications, but themore detailed original classifications of Travis areacceptable. Figure 4-5 or appropriate AmericanGeological Institute (AGI) data sheets are suggested foruse when estimating composition percentages inclassification.

Description of Rock

Adequate descriptors, a uniform format, and standardterminology must be used for all geologic investigationsto properly describe rock foundation conditions. These

FIE

LD

MA

NU

AL

60

Figure 4-1.—Field classification of igneous rocks (modified after R.B. Travis [1955]).

RO

CK

S

61 Figure 4-2.—Field classification of sedimentary rocks (modified after R.B. Travis [1955]).

FIE

LD

MA

NU

AL

62

Figure 4-3.—Field classification of metamorphic rocks (modified after R.B. Travis [1955]).

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Figure 4-4.—Field classification of pyroclastic rocks.Blocks are angular to subangular clasts > 64 millimeters(mm); bombs are rounded to subrounded clasts > 64 mm.Determine percent of each size present (ash, lapilli,blocks, and bombs) and list in decreasing order after rockname. Preceed rock name with the term "welded" forpyroclastic rocks which retained enough heat to fuseafter deposition. Rock names for such deposits areusually selected from the lower right portion of theclassification diagram above. (Modified from Fisher, 1966[2] and Williams and McBirney, 1979 [3]).

paragraphs provide descriptors for those physical charac-teristics of rock that are used in logs of exploration, innarratives of reports, and on preconstruction geologicmaps and cross sections, as well as construction or "as-built" drawings. The alphanumeric descriptors providedmay be used in data-field entries of computer generated

FIE

LD

MA

NU

AL

64

Figure 4-5.—Charts for estimating percentage of composition of rocks and sediments.[4]

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logs. Chapter 5 establishes descriptors for the physicalcharacteristics of discontinuities in rock required forengineering geologic studies.

All descriptors should be defined and included in alegend when submitting data for design and/or records ofconstruction. An example of a legend and explanation isfigure 4-6, Reclamation standard drawing 40-D-6493,may be used for geologic reports and specifications wherethe standard descriptors and terminology established forrock are used during data collection.

Format for Descriptions of Rock

Engineering geology rock descriptions should include gen-eralized lithologic and physical characteristics usingqualitative and quantitative descriptors. A generalformat for describing rock in exploration logs and legendson general note drawings is:

• Rock unit (member or formation) name• Lithology with lithologic descriptors

composition (mineralogy) grain/particle size

texture color

• Bedding/foliation/flow texture• Weathering• Hardness/strength• Contacts• Discontinuities (includes fracture indexes)• Permeability data (as available from testing)• Moisture conditions

Example descriptions are presented in a later section.

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Rock Unit Names and Identification

Rock unit names not only are required for identificationpurposes but may also provide indicators of depositionalenvironment and geologic history, geotechnical char-acteristics, and correlations with other areas. A simpledescriptive name and map symbol should be assigned toprovide other users with possible engineeringcharacteristics of the rock type. The rock unit names maybe stratigraphic, lithologic, genetic, or a combination ofthese, such as Navajo Sandstone (Jn), Tertiary shale(Tsh), Jurassic chlorite schist (Jcs), Precambrian granite(Pcgr), or metasediments (ms). Bedrock units of similarphysical properties should be delineated and identified asto their engineering significance as early as possibleduring each geologic study. Planning study maps andother large-scale drawings may require geologicformations or groups of engineering geologic units withdescriptions of their engineering significance inaccompanying discussions.

Units should be differentiated by engineering propertiesand not necessarily formal stratigraphic units wheredifferences are significant. Although stratigraphicnames are not required, units should be correlated tostratigraphic names in the data report or by anillustration, such as a stratigraphic column.Stratigraphic names and ages (formation, member) maybe used as the rock unit name.

For engineering studies, each particular stratigraphicunit may require further subdivisions to identifyengineering parameters. Examples of importantengineering properties are:

• Susceptibility to weathering or presence ofalteration

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Figure 4-6.—Descriptor legend and explanation example.

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• Dominant discontinuity characteristics

• Hardness and/or strength

• Deformability

• Deletereous minerals or beds (such as swellingsusceptibility, sulfates, or clays)

For example, a Tertiary shale unit, Tsh, may bedifferentiated as Tsh1 or Tsh2 if unit 2 contains bentoniteinterbeds and unit 1 does not, and Tshc could be used asa unit name for the bentonite beds. A chlorite schist unit,Cs, may be differentiated as CsA or CsB where unit Acontains higher percentages of chlorite or talc and issignificantly softer (different deformation properties) thanunit B. A metasediment unit, ms, may be furtherdifferentiated on more detailed maps and logs as mssh

(shale) or msls (limestone). All differentiated units shouldbe assigned distinctive map symbols and should bedescribed on the General Geologic Legend, Explanation,and Notes drawings.

Descriptors and Descriptive Criteria for PhysicalCharacteristics of Rock

Lithologic Descriptors (Composition, Grain Size,and Texture).—Provide a brief lithologic description ofthe rock unit. This includes a general description ofmineralogy, induration, cementation, crystal and grainsizes and shapes, textural adjectives, and color.Lithologic descriptors are especially important for thedescription of engineering geology subunits when rockunit names are not specific. Examples of rock unit namesthat are not specific are metasediments, Tertiaryintrusives, or Quaternary volcanics.

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1. Composition.—Use standard adjectives such assandy, silty, calcareous, etc. Detailed mineral composition generally is not necessary or desirable unlessuseful in correlating units or indicating pertinentengineering physical properties. Note uniquefeatures such as fossils, large crystals, inclusions,concretions, and nodules which may be used asmarkers for correlations and interpretations.

2. Crystal or particle sizes and shapes.—Describe the typical crystal or grain shapes andprovide a description of sizes present in the rock unitbased on the following standards:

• Igneous and metamorphic rocks.—Table 4-1 isrecommended for descriptions of crystal sizes inigneous and metamorphic rocks. Crystal sizesgiven in millimeters (mm) are preferred ratherthan fractional inch (in) equivalents.

Table 4-1.—Igneous and metamorphic rock grain size descriptors

DescriptorAverage crystal

diameter

Very coarse-grained or pegmatiticCoarse-grainedMedium-grainedFine-grainedAphanitic (cannot be seen with the unaided eye

> 10 mm (3/8 in)5-10 mm (3/16 - 3/8 in)1-5 mm (1/32 - 3/16 in)0.1-1 mm (0.04 - 1/32 in)<0.1 mm (<0.04 in)

• S e d i m e n t a r y a n d p y r o c l a s t i crocks.—Terminology for particle sizes and theirlithified products which form sedimentary andpyroclastic rocks is provided in table 4-2. The size

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Table 4-2.—Sedimentary and pyroclastic rock particle-size descriptors (AGI Glossary)

USGS(soils only)

Particle size

Sizein

mm (inches)

Sedimentary (epiclastic)Rounded, subrounded,

subangular Volcanic (pyroclastic)

Particle orfragment

Lithifiedproduct

Frag-ment

Lithifiedproduct*

Boulder

Cobble

Coarse gravel

Fine gravel

Coarse sand

Medium sand

Fine sand

Fines Non- plastic Silt

Plastic Clay

300 (12)

256 (10)

75 (3) 64 (2.5)

32 (1.3)

20 (0.8)

4.75 (0.19) 4 (0.16)

2 (0.08)

1 (0.04) 0.5 (0.02)

0.42 0.25 0.125 0.074 0.0625

0.00391

Boulder

Cobble

Pebble

Granule

Very coarse sand Coarse sand

Medium sand Fine sand Very fine sand

Silt

Clay

Boulder conglomerate

Cobble conglomerate

Pebble conglomerate

Granule conglomerate

Sandstone (Very coarse, coarse, medium fine, or very fine)

Siltstone Shale

Claystone Shale

Block+

Bomb

Lapilli

Coarse ash

Fine ash

Volcanic breccia+

Agglo- merate

Lapilli tuff

Coarse tuff

Fine tuff

+ Broken from previous igneous rock block shaped (angular to subangular). Solidified from plastic material while in flight, rounded clasts. * Refer to figure 4-4.

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limits do not correspond to the Unified SoilClassification System for soil particle size but areused for the field description and petrographicclassification of rocks. These limits are theaccepted sizes in geologic literature and are usedby petrographic laboratories.

3. Textural adjectives.—Texture describes the ar-rangements of minerals, grains, or voids. Thesemicrostructural features can affect the engineeringproperties of the rock mass. Use simple, standard,textural adjectives or phrases such as porphyritic,vesicular, scoriaceous, pegmatitic, granular, welldeveloped grains, dense, fissile, slaty, or amorphous.Use of terms such as holohyaline, hypidiomorphicgranular, and crystaloblastic is inappropriate.

Textural terms which identify solutioning, leaching,or voids in bedrock are useful for describing primarytexture, weathering, alteration, permeability, anddensity.

The terminology which follows defines sizes of voids, orholes in bedrock. However, when describing pits, vugs,cavities, or vesicles, a complete description which includesthe typical diameter, or the "mostly" range, and the max-imum size observed is required. For example:

". . . randomly oriented, elliptically shaped vugs rangemostly from 0.03 to 0.06 foot (ft) in diameter,maximum size 0.2 foot; decreases in size away fromquartz-calcite vein; about 15 percent contain calcitecrystals. . .”

or". . . cavity, 3.3 ft wide by 16.4 ft long by 2.3 ft high,striking N 45EW, dipping 85ESW was. . ..”

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• Pit (pitted).—Pinhole to 0.03 ft [d in] (<1 to10 mm) openings.

• Vug (vuggy).—Small opening (usually lined withcrystals) ranging in diameter from 0.03 ft [d in] to0.33 ft [4 in] (10 to 100 mm).

• Cavity.—An opening larger than 0.33 ft [4 in](100 mm), size descriptions are required, and adjec-tives such as small, or large, may be used, if defined.

• Honeycombed.—Individual pits or vugs are sonumerous that they are separated only by thin walls;this term is used to describe a cell-like form.

• Vesicle (vesicular).—Small openings in volcanicrocks of variable shape formed by entrapped gasbubbles during solidification.

4. Color.—As a minimum, provide the color of wetaltered and unaltered or fresh rock. Reporting colorfor both wet and dry material is recommended sincethe colors may differ significantly and causeconfusion. The Munsell Color System, as used in theGeologic Society of America Rock Color Chart [5], isused to provide standard color names and assist incorrelation. The chart also provides uniform andidentifiable colors to others. Color designators areoptional unless necessary for clarity, e.g., light brown(5YR 5/6). Terms such as banded, streaked, mottled,speckled, and stained may be used to further describecolor. Also describe colors of bands, etc.

Bedding, Foliation, and Flow Texture.—Thesefeatures give the rock anisotropic properties or representpotential failure surfaces. Continuity and thickness ofthese features influence rock mass properties and cannot

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always be tested in the laboratory. Descriptors intable 4-3 are used to identify these thicknesses.

Table 4-3.—Bedding, foliation, or flow texture descriptors

Descriptors Thickness/spacing

Massive Greater than 10 ft (3 meters [m])

Very thickly, bedded, foliated, or banded

3 to 10 ft (1 to 3 m)

Thickly 1 to 3 ft (300 mm to 1 m)

Moderately 0.3 to 1 ft (100 to 300 mm)

Thinly 0.1 to 0.3 ft (30 to 100 mm)

Very thinly 0.03 [3/8 in] to 0.1 ft (10 to 30 mm)

Laminated (intensely foliated or banded)

Less than 0.03 ft [3/8 in] (<10 mm)

Weathering and Alteration.—

1. Weathering.—Weathering, the process ofchemical or mechanical degradation of rock, cansignificantly affect the engineering properties of therock and rock mass. For engineering geologydescriptions, the term "weathering" includes bothchemical disintegration (decomposition) andmechanical disaggregation as agents of alteration.

Weathering effects generally decrease with depth, al-though zones of differential weathering can occur andmay modify a simple layered sequence of weathering.

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Examples are: (1) differential weathering within asingle rock unit, apparently due to relatively higherpermeability along fractures; (2) differentialweathering due to compositional or texturaldifferences; (3) differential weathering of contactzones associated with thermal effects such asinterflow zones within volcanics; (4) directionalweathering along permeable joints, faults, shears, orcontacts which act as conduits along whichweathering agents penetrate more deeply into therock mass; and (5) topographic effects.

Weathering does not correlate directly with specificgeotechnical properties used for many rock massclassifications. However, weathering is importantbecause it may be the primary criterion fordetermining depth of excavation, cut slope design,method and ease of excavation, and use of excavatedmaterials. Porosity, absorption, compressibility,shear and compressive strengths, density, andresistance to erosion are the major engineeringparameters influenced by weathering. Weatheringgenerally is indicated by changes in the color andtexture of the body of the rock, color, and condition offracture fillings and surfaces, grain boundaryconditions, and physical properties such as hardness.

Weathering is reported using descriptors presentedin table 4-4, which divides weathering into categoriesthat reflect definable physical changes due tochemical and mechanical processes. This tablesummarizes general descriptions which are intendedto cover ranges in bedrock conditions. Weatheringtables are generally applicable to all rock types;however, they are easier to apply to crystalline rocksand rocks that contain ferromagnesian minerals.Weathering in many sedimentary rocks will notalways conform to the criteria established in

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table 4-4, and weathering categories may have to bemodified for particular site conditions. However, thebasic horizontal categories and descriptors presentedcan be used. Site-specific conditions, such as fractureopenness, filling, and degree and depth ofpenetration of oxidation from fracture surfaces,should be identified and described.

2. Alteration.—Chemical alteration effects aredistinct from chemical and mechanical degradation(weathering), such as hydrothermal alteration, maynot fit into the horizontal suite of weatheringcategories portrayed in table 4-4. Oxides may or maynot be present. Alteration is site-specific, may beeither deleterious or beneficial, and may affect somerock units and not others at a particular site. Forthose situations where the alteration does not relatewell to the weathering categories, adjusting thedescription within the framework of table 4-4 may benecessary. Many of the general characteristics maynot change, but the degree of discoloration andoxidation in the body of the rock and on fracturesurfaces could be very different. Appropriatedescriptors, such as moderately altered or intenselyaltered, may be assigned for each alteration category.Alteration products, depths of alteration, andminerals should be described.

3. Slaking.—Slaking is another type ofdisintegration which affects engineering properties ofrock. Terminology and descriptive criteria to identifythis deleterious property are difficult to standardizebecause some materials air slake, many water slake,and some only slake after one or more wet-dry cycles.The Durability Index (DI) is a simplified method fordescribing slaking. Criteria for the index are based

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Table 4-4.—Weathering descriptors

Descriptors

Diagnostic features

General characteristics(strength, excavation, etc.)§

Chemical weathering—Discoloration and/or oxidation

Mechanical weathering- Grain boundaryconditions(disaggregation)primarily for graniticsand some coarse-grained sediments

Texture and solutioning

Alpha-numeric

descriptor Descriptive term Body of rockFracture surfaces† Texture Solutioning

W1 Fresh. No discoloration, not oxidized. No discoloration oroxidation.

No separation, intact(tight).

No change. No solutioning. Hammer rings when crystalline rocksare struck. Almost always rock exca-vation except for naturally weak orweakly cemented rocks such assiltstones or shales.

W2 Slightly weathered tofresh.*

W3 Sllightly weathered. Discoloration or oxidation is limitedto surface of, or short distancefrom, fractures; some feldsparcrystals are dull.

Minor to completediscoloration oroxidation of mostsurfaces.

No visible separation,intact (tight).

Preserved. Minor leaching ofsome solubleminerals may benoted.

Hammer rings when crystalline rocksare struck. Body of rock notweakened. With few exceptions, suchas siltstones or shales, classified asrock excavation.

W4 Moderately to slightlyweathered.*

W5 Moderatelyweathered.

Discoloration or oxidation extendsfrom fractures, usually throughout;Fe-Mg minerals are “rusty,”feldspar crystals are “cloudy.”

All fracture surfacesare discolored oroxidized.

Partial separation ofboundaries visible.

Generallypreserved.

Soluble mineralsmay be mostlyleached.

Hammer does not ring when rock isstruck. Body of rock is slightly weak-ened. Depending on fracturing,usually is rock excavation except innaturally weak rocks such assiltstone or shales.

W6 Intensely tomoderatelyweathered.*

W7 Intensely weathered. Discoloration or oxidationthroughout; all feldspars and Fe-Mg minerals are altered to clay tosome extent; or chemical alterationproduces in situ disaggregation, seegrain boundary conditions.

All fracture surfacesare discolored oroxidized, surfacesfriable.

Partial separation, rockis friable; in semiaridconditions granitics aredisaggregated.

Texture al-tered bychemicaldisintegration(hydration,argillation).

Leaching of solubleminerals may becomplete.

Dull sound when struck withhammer; usually can be broken withmoderate to heavy manual pressureor by light hammer blow withoutreference to planes of weakness suchas incipient or hairline fractures, orveinlets. Rock is significantlyweakened. Usually commonexcavation.

W8 Very intenselyweathered.

W9 Decomposed. Discolored or oxidized throughout,but resistant minerals such asquartz may be unaltered; allfeldspars and Fe-Mg minerals arecompletely altered to clay.

Complete separation ofgrain boundaries(disaggregated).

Resembles a soil, partial or completeremnant rock structure may bepreserved; leaching of solubleminerals usually complete.

Can be granulated by hand. Alwayscommon excavation. Resistantminerals such as quartz may bepresent as “stringers” or “dikes.”

Note: This chart and its horizontal categories are more readily applied to rocks with feldspars and mafic minerals. Weathering in various sedimentary rocks, particularly limestones and poorly induratedsediments, will not always fit the categories established. This chart and weathering categories may have to be modified for particular site conditions or alteration such as hydrothermal effects; however, thebasic framework and similar descriptors are to be used. * Combination descriptors are permissible where equal distribution of both weathering characteristics are present over significant intervals or where characteristics present are “in between” thediagnostic feature. However, dual descriptors should not be used where significant, identifiable zones can be delineated. When given as a range, only two adjacent terms may be combined (i.e., decomposedto lightly weathered or moderately weathered to fresh) are not acceptable. † Does not include directional weathering along shears or faults and their associated features. For example, a shear zone that carried weathering to great depths into a fresh rock mass would not requirethe rock mass to be classified as weathered. § These are generalizations and should not be used as diagnostic features for weathering or excavation classification. These characteristics vary to a large extent based on naturally weak materials orcementation and type of excavation.

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on time exposed and effects noted in the field(see table 4-5). These simplified criteria do notspecify whether the specimen or exposure iswetted, dried, or subjected to cyclic wetting anddrying, and/or freeze-thaw. When reportingslaking or durability, a complete descriptionincludes the test exposure conditions. Forexample, the material could be classified ashaving "characteristics of DI 3 upon drying."Slaking is not the same as the effects of beddingseparation or disaggregation produced by stressrelief.

Table 4-5.—Durability index descriptors

Alpha-numeric

descriptor Criteria

DI0 Rock specimen or exposure remains intact withno deleterious cracking after exposure longerthan 1 year.

DI1 Rock specimen or exposure develops hairlinecracking on surfaces within 1 month, but nodisaggregation within 1 year of exposure.

DI2 Rock specimen or exposure develops hairlinecracking on surfaces within 1 week and/ordisaggregation within 1 month of exposure.

DI3 Specimen or exposure may develop hairlinecracks in 1 day and displays pronouncedseparation of bedding and/or disaggregationwithin 1 week of exposure.

DI4 Specimen or exposure displays pronouncedcracking and disaggregation within 1 day(24 hours) of exposure. Generally ravels anddegrades to small fragments.

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A field test suitable for evaluating the degreeand rate of slaking for materials, primarilyclayey materials and altered volcanics, isdescribed below. The slaking test evaluates thedisaggregation of an intact specimen in waterand reflects the fabric of the material, internalstresses, and character of the interparticlebonds.

To evaluate slaking behavior, immerse twointact specimens (pieces of core or rockfragments consisting of a few cubic inches orcentimeters) in water. One piece should be atnatural water content (wrapped jar sample) andone piece from an air-dried sample. Test resultsshould be photographed with labels to identifyspecimens and exposure times.

Results of the evaluation should be reported foreach specimen. Describe the behavior of thespecimens as follows:

a. Volume changes.—The volume of the materialreduced to individual particles should be estimatedand compared to the initial volume of material.The degree of disaggregation is described using thefollowing descriptive criteria:

None No discernable disaggregationSlight Less than 5 percent of the volume

disaggregatedModerate Between 5 and 25 percent of the

volume disaggregatedIntense More than 25 percent but less

than the total volume disaggregated

Complete No intact piece of the material remains

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b. Rate of slaking.—The following descriptors areused to identify the time to slake:

Slow slaking Action continues for several hours

Moderate Action completed within 1 hour slaking

Rapid Action completed within slaking 2 minutesSudden Complete reaction, action com- slaking pleted instantaneously

[Generally, slaking applies to rock; disaggregation appliesto soils.]

4. Character of material.—The character of theremaining pieces of material after the test iscompleted is described as follows:

No change Material remains intactPlates remain Remaining material present as

platy fragments of generally uniform thickness

Flakes remain Remaining material present as flaky or wedge-shaped fragments

Blocks remain Blocky fragments remainGrains remain Remaining material chiefly present

as sand-size grains

No fragments Remaining material entirely disag- gregated to clay-size particles

Hardness—Strength.—Hardness can be related tointact rock strength as a qualitative indication of densityand/or resistance to breaking or crushing. Strength is anecessary engineering parameter for design that

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frequently is not assessed, but plays a role in engineeringdesign and construction, such as tunnel supportrequirements, bit wear for drilling or tunnel boringmachine (TBM) operations, allowable bearing pressures,excavation methods, and support.

The hardness and strength of intact rock is a function ofthe individual rock type but may be modified byweathering or alteration. Hardness and strength aredescribed for each geologic unit when they are functionsof the rock type and also for zones of alteration orweathering when there are various degrees of hardnessand/or strength due to different degrees of weathering orchemical alteration. When evaluating strengths, it isimportant to note whether the core or rock fragmentsbreak around, along, or through grains; or along or acrossincipient fractures, bedding, or foliation.

Hardness and especially strength are difficultcharacteristics to assess with field tests. Two field testscan be used; one is a measure of the ability to scratch thesurface of a specimen with a knife, and the other is theresistance to fracturing by a hammer blow. Results fromboth tests should be reported. The diameter and lengthof core or the fragment size will influence the estimationof strength and should be kept in mind when correlatingstrengths. A 5- to 8-inch (130- to 200-mm) length ofN-size core or rock fragment, if available, should be usedfor hardness determinations to preclude erroneouslyreporting point, rather than average hardness, and toevaluate the tendency to break along incipient fracturesand textural or structural features when struck with arock pick. Standards (heavy, moderate, and lighthammer blow) should be calibrated with other geologistsmapping or logging core for a particular project.Descriptors used for rock hardness/strength are shown ontable 4-6.

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Table 4-6.—Rock hardness/strength descriptors

Alpha-numeric

descriptor Descriptor Criteria

H1 Extremely hard

Core, fragment, or exposure cannot bescratched with knife or sharp pick; can onlybe chipped with repeated heavy hammerblows.

H2 Very hard Cannot be scratched with knife or sharppick. Core or fragment breaks withrepeated heavy hammer blows.

H3 Hard Can be scratched with knife or sharp pickwith difficulty (heavy pressure). Heavyhammer blow required to break specimen.

H4 Moderately hard

Can be scratched with knife or sharp pickwith light or moderate pressure. Core orfragment breaks with moderate hammerblow

H5 Moderately soft

Can be grooved 1/16 inch (2 mm) deep byknife or sharp pick with moderate or heavypressure. Core or fragment breaks with lighthammer blow or heavy manual pressure.

H6 Soft Can be grooved or gouged easily by knife orsharp pick with light pressure, can bescratched with fingernail. Breaks with lightto moderate manual pressure.

H7 Very soft Can be readily indented, grooved or gougedwith fingernail, or carved with a knife.Breaks with light manual pressure.

Any bedrock unit softer than H7, very soft, is to be described usingUSBR 5000 consistency descriptors.

Note: Although "sharp pick" is included in these definitions, descrip-tions of ability to be scratched, grooved, or gouged by a knife is thepreferred criteria

A few empirical and quantitative field techniques whichare quick, easy, and inexpensive are available to providestrength estimates. Quantitative strength estimates can

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be obtained from the point load test. A lightweight andportable testing device is used to break a piece of core(with a minimum length at least 1.5 times the diameter)between two loading points. If a new fracture does notrun from one loading point to the other upon completionof the test, or if the points sink into the rock surfacecausing excessive deformation or crushing, the testshould not be recorded. Raw data are given with thereduced data (equations to empirically convert load datato compressive strengths are usually supplied with theequipment). The Schmidt (L) hammer may also be usedfor estimating rock strengths; refer to Field Index Testsin chapter 5. Each of these tests can be used to calibratethe manual index (empirical) properties described intable 4-6, and a range of compressive strengths can beassigned. Depending on the scope of the study andstructure being considered, laboratory testing may berequired and used to confirm the field test data.

Discontinuities.—Describe all discontinuities such asjoints, fractures, shear/faults, and shear/fault zones, andsignificant contacts. These descriptions should include allobservable characteristics such as orientation, spacing,continuity, openness, surface conditions, and fillings.Appropriate terminology, descriptive criteria anddescriptors, and examples pertaining to discontinuitiesare presented in chapter 5.

Contacts.—Contacts between various rock units or rock/soil units must be described. In addition to providing ageologic classification, describe the engineeringcharacteristics such as the planarity or irregularity andother descriptors used for discontinuities.

Descriptors applicable to the geologic classification of con-tacts are:

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• Conformable• Unconformable• Welded—contact between two lithologic units, one

of which is igneous, that has not been disruptedtectonically

• Concordant (intrusive rocks)• Discordant (intrusive rocks)

Descriptors pertinent to engineering classification of con-tacts are:

• Jointed—contact not welded, cemented, orhealed—a fracture

• Intact• Healed (by secondary process)• Sharp• Gradational• Sheared• Altered (baked or mineralized)• Solutioned

If jointed or sheared, additional discontinuity descriptorssuch as thickness of fillings, openness, moisture, androughness, should be provided also (see discontinuitydescriptors in chapter 5).

Permeability Data.—Permeability (hydraulicconductivity) is an important physical characteristic thatmust be described. Suggested methods for testing,terminology, and descriptors are available in the EarthManual and Ground Water Manual. Numerical valuesfor hydraulic conductivity (K) can be determined usingany of several methods. These values may be shown ondrill hole logs. For narrative discussions or summarydescriptions, the numerical value and descriptors may beused. Descriptors to be used—such as low,

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moderate—are those shown on figure 4-7. Whetherpermeability is primary (through intact rock) orsecondary (through fractures) should be indicated.

Example Descriptions

The examples which follow are in representative formatsfor describing bedrock in the physical conditions columnof drill hole logs and on a legend, explanation, and notesdrawing.

Core Log Narrative

Several examples of descriptions for core logs arepresented. These examples illustrate format and the useof the lithologic descriptors but do not include adescription of discontinuities.

Log with Alphanumeric Descriptors and EnglishUnits.—

. . . 12.6 to 103.6: Amphibolite Schist (JKam). Fine-grained (0.5 to 1 mm); subschistose to massive; greenish-black (5G 2/1) with numerous blebs andstringers of white calcite to 0.02 ft thick withsolution pits and vugs to 0.03 ft, mostly 0.01 ft,aligned subparallel to foliation; very thinly foliated,foliation dips 65E to 85E, steepening with depth.Moderately to slightly weathered (W4), iron oxidestaining on all discontinuities. Hard (H3), can bescratched with knife with heavy pressure, corebreaks parallel to foliation with heavy hammerblow. Slightly fractured (FD3),. . ..

RO

CK

S

87 Figure 4-7.—Permeability conversion chart.

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Log with Alphanumeric Descriptors Using MetricUnits.—

103.60 to 183.22: Sandstone (TUsa). Ferruginousquartzose sandstone. Medium-grained (0.25 to0.5 mm), well sorted, subrounded to rounded quartzgrains are well cemented by silica; hematite occursas minor cement agent and as thin coating ongrains. Moderate reddish-brown (10R 6/6).Moderately bedded, beds 250 to 310 mm thick,bedding dips 15E to 29E, averages 18E. Slightlyweathered. Hard, cannot be scratched with knife,core breaks with heavy hammer blow across beddingand through grains. Moderately fractured. Corerecovered. . ..

172.41-176.30: Claystone (TUc2). Calcareousmontmorillonitic clay with 20 percent subangular,fine sand-size quartz fragments. Strong reactionwith hydrochloric acid (HCl), grayish pink (5R 8/2).Moderately to rapidly slaking when dropped inwater. Very thinly bedded to laminated with bedthickness from 8 to 20 mm. Very intenselyweathered. Very soft, can be gouged with fingernail,friable, core breaks with manual pressure, smallerfragments can be crushed with fingers. . . Uppercontact is parallel to bedding, conformable,gradational, and intact; lower contact isunconformable, sharp and jointed but tight; dips 35E. . ..

Legend

The example which follows could be typical of a rock unitdescription on a general legend, explanation, and notedrawing. The object is to describe as many physicalproperties as possible which apply to the entire rock unitat the site. If individual subunits can be differentiated,they could be assigned corresponding symbols and

ROCKS

89

described below the undifferentiated description. Thosecharacteristics in the subunits which are similar or areincluded in the undifferentiated unit do not need to berepeated for each subunit.

Amphibolite Schist - Undifferentiated.—Mineralogyvariable but generally consists of greater than 30 percentamphibole. Contains varying percentages of feldspar,quartz, and epidote in numerous, thin, white and lightgreen (5G 7/4), discontinuous stringers and blebs.Texture ranges from fine grained and schistose tomedium grained and subschistose. Overall, color rangesfrom greenish black (5G 2/1) to olive black (5Y 2/1).Thinly foliated; foliation dips steeply 75E to 85E NE.Weathering is variable but generally moderately wea-thered to depths of 75 ft, slightly weathered to 120 ft, andfresh below. Where oxidized, moderate reddish-brown(10R 4/6), frequently with dendritic patterns of oxides ondiscontinuities. Hard, fresh rock can be scratched slightlywith heavy knife pressure; fresh N-size core breaks alongfoliation with moderate to heavy hammer blow. Foliationjoints are variably spaced and discontinuous, spaced moreclosely where weathered. Joint sets are prominent butdiscontinuous. (Joint sets are identified in thespecifications paragraphs). Commonly altered 0.1 to 6 ftalong contacts of dikes and larger shears with epidote andquartz ("altered amphibolite" on logs of exploration).When altered, harder than amphibolite. Based on drillhole permeability testing, hydraulic conductivity is verylow to low, with values ranging from 0.09 to 130 feet peryear (ft/yr) averages 1.5 ft/yr in slightly weathered andfresh rock.

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BIBLIOGRAPHY

[1] Travis, Russell B., "Classification of Rocks," v. 50,No. 1, Quarterly of the Colorado School of Mines,Golden, CO, January 1955.

[2] Fisher, R.V., "Rocks Composed of Volcanic Frag-ments: Earth Science Review, v. I, pp. 287-298, 1966.

[3] Williams, H., and McBirney, A., Volcanology,published by Freeman, Cooper and Company,San Francisco, CA. 391 pp., 1979.

[4] Compton, Robert R., Geology in the Field, publishedby John Wiley & Sons, Inc., New York, NY, 1985.

[5] Geological Society of America Rock Color Chart,8th printing, 1995.

Chapter 6

GEOLOGIC MAPPING ANDDOCUMENTATION

Geologic mapping is defined as the examination ofnatural and manmade exposures of rock or uncon-solidated materials, the systematic recording of geologicdata from these exposures, and the analysis and inter-pretation of these data in two- or three-dimensionalformat (maps, cross sections, and perspective [block]diagrams). The maps and cross sections generated fromthese data: (1) serve as a record of the location of factualdata; (2) present a graphic picture of the conceptualmodel of the study area based on the available factualdata; and (3) serve as tools for solving three-dimensionalproblems related to the design, construction, and/ormaintenance of engineered structures or site characteri-zation. This chapter presents guidelines for thecollection and documentation of surface and subsurfacegeologic field data for use in the design, specifications,construc-tion, or maintenance of engineered structuresand site characterization studies.

Responsibilities of the Engineering Geologist

An engineering geologist defines, evaluates, and docu-ments site-specific geologic conditions relating to thedesign, construction, maintenance, and remediation ofengineered structures or other sites. This responsibilityalso may include more regionally based geologic studies,such as materials investigations or regional reconnais-sance mapping. An engineering geologist engaged ingeologic mapping is responsible for:

• Recognizing the key geologic conditions in a studyarea that will or could significantly affect hazardousand toxic waste sites or a proposed or existingstructure;

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• Integrating all the available, pertinent geologicdata into a rational, interpretive, three-dimensionalconceptual model of the study area and presentingthis conceptual model to design and constructionengineers, other geologists, hydrologists, sitemanagers, and contractors in a form that can beunderstood.

The process and responsibilities of engineering geologymapping are illustrated in figure 6-1.

The engineering geologist needs to realize that geologicmapping for site characterization is a dynamic process ofgathering, evaluating, and revising geologic data andthat the significance of these data, both to the structureand to further exploration, must be continually assessed.The initial exploration program for a structure is alwaysbased on incomplete data and must be modifiedcontinuously as the site geology becomes betterunderstood. The key to understanding the site geologyis through interpretive geologic drawings such asgeologic maps, cross sections, isopachs, and contourmaps of surfaces. These working drawings, periodicallyrevised and re-interpreted as new data become available,are continuously used to assess the effects of the sitegeology and to delineate areas where additional explora-tion is needed. These drawings are used in designs,specifica-tions, and modeling and maintained in thetechnical record of the project.

Development of a Study Plan

Prior to mapping any project, a study plan must bedeveloped. Depending on the complexity of the sitegeology, the nature of the engineered structure, and thelevel of

MA

PP

ING

131 Figure 6-1.—Process of engineering geology mapping.

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previous studies, the study plan may be preliminary orcomprehensive. Although elements of the plan may bemodified, expanded, or deleted as geologic data becomeavailable, the primary purpose of the study plan—coordination among all geologists and engineers workingon the project—should be retained. Early study plandevelopment and agreement to this plan by thoseinvolved in the project are necessary to prevent thecollection of unneeded, possibly costly data and ensureneeded data are available at the correct time in theanalysis, design, and construction process.

Scope of Study

The purpose and scope of the mapping project arestrongly influenced by the primary engineering andgeologic considerations, the level of previous studies, andoverall job schedules. The purpose and scope areformulated jointly by the geologists and engineers on theproject. Time of year and critical dates for neededinformation also will have a great impact on the pace ofdata collection and the personnel needed to handle amapping project. Discussion of these factors prior toinitiating the mapping program is essential so that onlynecessary data are obtained and the work can becompleted on schedule. Items to consider when definingthe scope of a mapping program are:

1. Study limits.—Set general regional and site studylimits based on engineering and geologic needs.

2. Critical features and properties.—Determine thecritical geologic features and physical properties of sitematerials that will need to be defined and discuss thedifficulties in collecting data on these features.

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3. Schedules.—Determine schedules under which thework will be performed and define key data due dates.Prioritize work to be done. The time of year the mappingis to be performed, the type of mapping required,available personnel and their skills, the availability ofsupport personnel such as drill crews and surveyors, andbudget constraints will influence the work schedule andmust be carefully evaluated.

4. Extent of previous studies.—Collect and study allavailable geologic literature for the study area. The ex-tent and adequacy of previous studies helps to define thetypes of mapping required and how data will becollected, i.e., based on analyses, design, or constructionneeds.

5. Photography.—Aerial and terrestrial photo-graphy should be considered for any project. As a mini-mum, aerial photographs of the site should be reviewed.Aerial photographs reveal features that are difficult torecognize from the ground or at small scales. Extensiveuse of terrestrial or aerial photography will require adifferent approach to the mapping program. Defineareas where terrestrial photogrammetry could aidmapping progress. Terrestrial photography of varioustypes is an integral part of the final study record.

Specific Mapping Requirements

This section provides the basic considerations anengineering geologist should evaluate prior to startingany mapping project or portion of a mapping project.

Map Type

Define the types of mapping required and how data areto be collected, including special equipment needed for

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data collection. The types of mapping required dependon the study purpose or the type of structure or site thatis to be built or rehabilitated, structure size, the phase ofstudy (planning through operation and maintenance),and the specific design needs.

Scales and Controls

Define the required scales for design or constructionneeds. Although finished maps can be enlarged orreduced photographically or by Computer-Aided DraftingDesign (CADD)-generated drawings to any desired scale,in most cases map text and symbols will have to beredone for legibility. Selection of an adequate map scaleat the beginning of a mapping project will save time andenergy as well as help ensure that the types of dataneeded can be portrayed adequately on the finaldrawings. Suggested map scales for various types ofinvestigations are listed under specific mappingtechniques.

The horizontal and vertical accuracy and precision oflocations on a map depend on the spatial control of thebase map. General base map controls are listed indecreasing significance: (1) Survey Control or ControlledTerrestrial Photogrammetry—geology mapped fromsurvey controlled observation points or by plane table orstadia; (2) Existing Topographic Maps—control for thesemaps vary with scale. The most accurate are large-scalephotogrammetric topographic maps generated fromaerial photographs for specific site studies; (3)U n c o n t r o l l e d A e r i a l / T e r r e s t r i a lPhotogrammetry—Camera lens distor-tion is the chiefsource of error; (4) Brunton Compass/ Tape Surveys—canbe reasonably accurate if measure-ments are taken withcare; and (5) Sketch Mapping— Practice is needed tomake reasonably accurate sketch

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maps. The Global Positioning System can provide ade-quate position locations depending on the requiredaccuracy or precision.

Global Positioning System

The Global Positioning System (GPS) is a system ofsatellites that provides positioning data to receivers onearth. The receiver uses the positioning data to calculatethe location of the receiver on earth. Accuracy and typeof data output depends on many factors that must beevaluated before using the system. The factors thatmust be evaluated are: (1) the needs of the project, (2)the capabilities of the GPS equipment, and (3) theparameters necessary for collecting the data in anappropriate form.

Project Requirements

The location accuracy or precision needed by the projectis a controlling factor whether GPS is appropriate for theproject. The actual needs of the project should be deter-mined, being careful to differentiate with “what would benice.” Costs should be compared between traditionalsurveying and GPS.

GPS Equipment

Different GPS receiver/systems have differentaccuracies. Accuracies can range from 300 ft to inches(100 m to cm) depending on the GPS system. Costsincrease exponen-tially with the increase in accuracy. Arealistic evalua-tion of the typical accuracy of theequipment to be used is necessary, and a realisticevaluation of the needed, not “what would be nice,”accuracy is important. Possible accuracy and typicalaccuracy are often not the same.

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Datums

The datum or theoretical reference surface to be used forthe project must be determined at the start. U.S.Geologi-cal Survey (USGS) topographic maps commonlyuse North American Datum (NAD) 27, but most newsurveys use NAD 83. Changing from one datum toanother can result in apparent location differences ofseveral hundred feet or meters if not done properly.

Map Projections

The map projection is the projection used to depict theround shape of the earth on a flat plane or map. Themost common projections used in the United States arethe Transverse Mercator and the Lambert ConformalConic. State plane coordinate systems almostexclusively use one or the other. To use these stateplane projections, location and definition parameters arenecessary. Table 6-1 has the types of projections and theprojection parameters for each state in the UnitedStates. A discussion of map projections and coordinatesystems is in Map Projections - A Working Manual,USGS Profes-sional Paper 1395[1].

Transverse Mercator.—The Transverse Mercatorprojection requires a central meridian, scale reduction,and origin for each state or state zone.

Lambert Conformal Conic.—The Lambert ConformalConic projection requires two standard parallels and anorigin for each state or state zone.

Coordinate System.—The coordinate system is the gridsystem that is to be used on the project. The state plane

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Table 6-1.—U.S. State plane coordinate systems – 1927 datum

(T indicates Transverse Mercator: L. Lambert Conformal Conic: H. Hotine Oblique Mercator. Modified slightly and updated from

Mitchell and Simmons, 1945, p. 45-47)

AreaProjec-

tion Zones AreaProjec-

tion Zones

Alabama _______Alaska ________

Arizona _______Arkansas ______California _____Colorado ______Connecticut ____Deleware ______Florida ________

Georgia _______Hawaii ________Idaho _________Illinois ________Indiana _______Iowa __________Kansas ________Kentucky ______Louisiana _____Maine _________Maryland _____Massachusetts _Michigan1

obsolete _____current _____

Minnesota _____Mississippi ____Missouri ______Montana ______Nebraska _____

TTLHTLLLLTTLTTTTTLLLLTLL

TLLTTLL

281132731121253222223212

3332332

Nevada _______New Hampshire __New Jersey ___New Mexico ___New York _____

North Carolina North Dakota _Ohio __________Oklahoma _____Oregon _______Pennsylvania __Puerto Rico & Virgin Islands _____Rhode Island __Samoa ________South Carolina ____South Dakota _Tennessee ____Texas ________Utah _________Vermont ______Virginia ______Washington ___West Virginia _Wisconsin ____Wyoming _____

T

TTTTL

LLLLLL

LTL

LLLLLTLLLLT

3

11331

122222

211

22153122234

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Table 6-1.—U.S. State plane coordinate systems – 1927 datum(continued)

Transverse Mercator Projection

ZoneCentral

meridianScale

reduction2Origin3

(latitude)

AlabamaEast ______________West _____________

85E87

50' W.30

1:25,0001:15,000

30E30

30' N.00

Alaska4

2 _________________ 142 00 1:10,000 54 003 _________________ 146 00 1:10,000 54 004 _________________ 150 00 1:10,000 54 005 _________________ 154 00 1:10,000 54 006 _________________ 158 00 1:10,000 54 007 _________________ 162 00 1:10,000 54 008 _________________ 166 00 1:10,000 54 009 _________________ 170 00 1:10,000 54 00

ArizonaEast _____________ 110 10 1:10,000 31 00Central ___________ 111 55 1:10,000 31 00West _____________ 113 45 1:15,000 31 00

Delaware ___________ 75 25 1:200,000 38 00Florida4

East _____________ 81 00 1:17,000 24 20West _____________ 82 00 1:17,000 24 20

GeorgiaEast _____________ 82 10 1:10,000 30 00 West ____________ 84 10 1:10,000 30 00

Hawaii1 ________________ 155 30 1:30,000 18 502 ________________ 156 40 1:30,000 20 203 ________________ 158 00 1:100,000 21 104 ________________ 159 30 1:100,000 21 505 ________________ 160 10 0 21 40

IdahoEast ______________ 112 10 1:19,000 41 40Central ___________ 114 00 1:19,000 41 40West _____________ 115 45 1:15,000 41 40

IllinoisEast ______________ 88 20 1:40,000 36 40West _____________ 90 10 1:17,000 36 40

Indiana East _____________ 85 40 1:30,000 37 30West _____________ 87 05 1:30,000 37 30

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139

Table 6-1.—U.S. State plane coordinate systems – 1927 datum(continued)

Transverse Mercator Projection

ZoneCentral

meridianScale

reduction2Origin3

(latitude)

MaineEast _____________ 68E30' W. 1:10,000 43E 50' N.West _____________ 70 10 1:30,000 42 50

Michigan (old)4

East _____________ 83 40 1:17,500 41 30Central ___________ 85 45 1:11,000 41 30West _____________ 88 45 1:11,000 41 30

MississippiEast ______________ 88 50 1:25,000 29 40West _____________ 90 20 1:17,000 30 30

MissouriEast ______________ 90 30 1:15,000 35 50Central ___________ 92 30 1:15,000 35 50West _____________ 94 30 1:17,000 36 10

NevadaEast ______________ 115 35 1:10,000 34 45Central ___________ 116 40 1:10,000 34 45West _____________ 118 35 1:10,000 34 45

New Hampshire ______ 71 40 1:30,000 42 30New Jersey __________ 74 40 1:40,000 38 50New Mexico

East ______________ 104 20 1:11,000 31 00Central ___________ 106 15 1:10,000 31 00West _____________ 107 50 1:12,000 31 00

New York4

East ______________ 74 20 1:30,000 40 00Central ___________ 76 35 1:16,000 40 00West _____________ 78 35 1:16,000 40 00

Rhode Island ________ 71 30 1:160,000 41 05Vermont _____________ 72 30 1:28,000 42 30Wyoming

East _____________ 105 10 1:17,000 40 40East Central 107 20 1:17,000 40 40West Central 108 45 1:17,000 40 40West _____________ 110 05 1:17,000 40 40

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Table 6-1.—U.S. State plane coordinate systems – 1927 datum(continued)

Lambert Conformal Conic projection

ZoneStandardparallels

Origin5

Longitude Latitude

Alaska4

10 ___________ 51E50' N. 53E 50' N. 176E00' W.5a 51E 00' N.Arkansas

North ________ 34 56 36 14 92 00 34 20South ________ 33 18 34 46 92 00 32 40

California I ____________ 40 00 41 40 122 00 39 20II ___________ 38 20 39 50 122 00 37 40III ___________ 37 04 38 26 120 30 36 30IV ___________ 36 00 37 15 119 00 35 20V ____________ 34 02 35 28 118 00 33 30VI ___________ 32 47 33 53 116 15 32 10VII __________ 33 52 34 25 118 20 34 085b

ColoradoNorth _______ 39 43 40 47 105 30 39 20Central ______ 38 27 39 45 105 30 37 50South _______ 37 14 38 26 105 30 36 40

Connecticut ____ 41 12 41 52 72 45 40 505d

Florida4 North _______ 29 35 30 45 84 30 29 00

Iowa North _______ 42 04 43 16 93 30 41 30South _______ 40 37 41 47 93 30 40 00

Kansas North _______ 38 43 39 47 98 00 38 20South _______ 37 16 38 34 98 30 36 40

Kentucky North _______ 37 58 38 58 84 15 37 30South _______ 36 44 37 56 85 45 36 20

Louisiana North _______ 31 10 32 40 92 30 30 40South _______ 29 18 30 42 91 20 28 40Offshore _____ 26 10 27 50 91 20 25 40

Maryland ______ 38 18 39 27 77 00 37 505c

Massachusetts Mainland ____ 41 43 42 41 71 30 41 005d

Island _______ 41 17 41 29 70 30 41 005c

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141

Table 6-1.—U.S. State plane coordinate systems – 1927 datum(continued)

Lambert Conformal Conic projection (continued)

ZoneStandardparallels

Origin5

Longitude LatitudeMichigan

(current)4

North _______ 45E29' N. 47E 05' N. 87E00' W. 44E 47' N.Central ______ 44 11 45 42 84 20 43 19South _______ 42 06 43 40 84 20 41 30

MinnesotaNorth _______ 47 02 48 38 93 06 46 30Central ______ 45 37 47 03 94 15 45 00South _______ 43 47 45 13 94 00 43 00

MontanaNorth _______ 47 51 48 43 109 30 47 00Central ______ 46 27 47 53 109 30 45 50South _______ 44 52 46 24 109 30 44 00

NebraskaNorth _______ 41 51 42 49 100 00 41 20South _______ 40 17 41 43 99 30 39 40

New York4

Long Island __ 40 40 41 02 74 00 40 305f

North Carolina ______

34 20 36 10

79 00 33 45

North Dakota North _______ 47 26 48 44 100 30 47 00South _______ 46 11 47 29 100 30 45 40

OhioNorth _______ 40 26 41 42 82 30 39 40South _______ 38 44 40 02 82 30 38 00

Oklahoma North _______ 35 34 36 46 98 00 35 00South _______ 33 56 35 14 98 00 33 20

OregonNorth _______ 44 20 46 00 120 30 43 40South _______ 42 20 44 00 120 30 41 40

PennsylvaniaNorth _______ 40 53 41 57 77 45 40 10South _______ 39 56 40 58 77 45 39 20

Puerto Rico and Virgin Islands

1 ___________ 18E 02' N. 18E 26' N. 66E 26' W. 17E 50' N.5g

2 (St. Croix) __ 18 02 18 26 66 26 17 505f, g

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Table 6-1.—U.S. State plane coordinate systems – 1927 datum(continued)

Lambert Conformal Conic projection (continued)

ZoneStandardparallels

Origin5

Longitude Latitude

Samoa _________ 14E16' S. (single) 170 005h — —South Carolina

North _______ 33E46' N. 34 58 81 00 33 00South _______ 32 20 33 40 81 00 31 50

South DakotaNorth ________ 44 25 45 41 100 00 43 50South _______ 42 50 44 24 100 20 42 20

Tennessee ______ 35 15 36 25 86 00 34 405f

Note: All these systems are based on the Clarke 1866 ellipsoid and arebased on the 1927 datum. Origin refers to rectangular coordinates. 1 The major and minor axes of the ellipsoid are taken at exactly1.0000382 times those of the Clarke 1866, for Michigan only. Thisincorporates an average elevation throughout the State of about 800 ft,with limited variation. 2 Along the central meridian. 3 At origin, x = 500,000 ft, y = 0 ft, except for Alaska zone 7, x =700,000 ft; Alaska zone 9, x = 600,000 ft; and New Jersey, x =2,000,000 ft. 4 Additional zones listed in this table under other projection(s). 5 At origin, x = 2,000,000 ft, 7 = 0 ft, except (a) x = 3,000,000 ft, (b) x =4,186,692.58, y = 4,160,926.74 ft, (c) x = 800,000 ft, (d) x = 600,000 ft,(e) x = 200,000 ft, (f) y = 100,000 ft, (g) x = 500,000 ft, (h) x = 500,000 ft,y = 0, but radius to latitude of origin = -82,000,000 ft.

system is used by most projects, but latitude/longitude,universal transverse mercator, or a local coordinatesystem may be used.

State Plane Coordinate Systems-changes for 1983datum.—This listing indicates changes for the NAD1983 datum from projections, parameters, and origins ofzones for the NAD 1927 datum. State plane coordinatesbased on the 1927 datum cannot be correctly convertedto coordinates on the 1983 datum merely by usinginverse formulas to convert from 1927 rectangularcoordinates to latitude and longitude, and then using

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143

forward formulas with this latitude and longitude toconvert to 1983 rectangular coordinates. Due toreadjustment of the survey control networks and to thechange of ellipsoid, the latitude and longitude alsochange slightly from one datum to the other.

These changes are given in the same order as the entriesin the 1927 table, except that only the changes areshown. All parameters not listed remain as before,except for the different ellipsoid and datum. Because allcoordinates at the origin have been changed, and becausethey vary considerably, the coordinates are presented inthe body of the table rather than as footnotes. Somoa isnot being changed to the new datum.

Table 6-2.—U.S. State plane coordinate systems – 1983 datum

[L indicates Lambert Conformal Conic]

Area Projection Zones

California L 6

Montana L 1

Nebraska L 1

Puerto Rico and Virgin Islands L 1

South Carolina L 1

Wyoming UnresolvedTransverse Mercator projection

Coordinates of origin (meters)

Zone x y Other Changes

AlabamaEastWest

200,000600,000

00

Alaska, 2-9 500,000 0

Arizona, all 213,360 0 Origin in Intl. feet1

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Table 6-2.—U.S. State plane coordinate systems – 1983 datum(continued)

Transverse Mercator projection (continued)

Coordinates of origin (meters)

Zone x y Other Changes

Delaware 200,000 0

FloridaEast, West 200,000 0

GeorgiaEastWest

200,000700,000

00

Hawaii, all 500,000 0

IdahoEastCentralWest

200,000500,000800,000

000

IllinoisEastWest

300,000700,000

00

IndianaEastWest

100,000900,000

250,000250,000

MaineEastWest

300,000900,000

00

Lat. of origin 43E40' N.

MississippiEast

West

300,000

700,000

0

0

Scale reduction 1:20,000,Lat. of origin 29E30' N.Scale reduction 1:20,000,Lat. of origin 29E30' N.

MissouriEastCentralWest

250,000500,000850,000

000

NevadaEastCentralWest

200,000500,000800,000

8,000,0006,000,0004,000,000

New Hampshire 300,000 0

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145

Table 6-2.—U.S. State plane coordinate systems – 1983 datum(continued)

Transverse Mercator projection (continued)

Coordinates of origin (meters)

Zone x y Other Changes

New Jersey 150,000 0 Central meridian 74E30'W.Scale reduction 1:10,000.

New MexicoEastCentralWest

165,000500,000830,000

000

New YorkEast All parameters identical with above New Jersey zone.CentralWest

250,000350,000

00

Rhode Island 100,000 0

Vermont 500,000 0

Wyoming Unresolved

Lambert Conformal Conic projection

Coordinates of origin (meters)

Zone x y Other Changes

Alaska, 10 1,000,000 0

ArkansasNorth 400,000 0South 400,000 400,000

California1-6 2,000,000 500,000

Zone 7 deleted.

Colorado, all 914,401.8289 304,800.6096

Connecticut 304,800.6096 152,400.3048

Florida, North 600,000 0Iowa

North 1,500,000 1,000,000South 500,000 0

KansasNorth 400,000 0South 400,000 400,000

KentuckyNorth 500,000 0South 500,000 500,000

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Table 6-2.—U.S. State plane coordinate systems – 1983 datum(continued)

Lambert Conformal Conic projection (continued)

Coordinates of origin (meters)

Zone x y Other Changes

KansasNorth 400,000 0South 400,000 400,000

KentuckyNorth 500,000 0South 500,000 500,000

LouisianaNorthSouthOffshore

1,000,0001,000,0001,000,000

000

Lat. of origin 30E30' N.Lat. of origin 28E30' N.Lat of origin 25E30' N.

Maryland 400,000 0 Lat. of origin 37E40' N.

MassachusettsMainland 200,000 750,000Island 500,000 0

MichiganGRS 80 ellipsoid usedwithout alteration.

NorthCentralSouth

8,000,0006,000,0004,000,000

000

Long. of origin 84E22'W.Long. of origin 84E22'W.

Minnesota, all 800,000 100,000

Montana(single zone)

600,000 0 Standard parallels, 45E00'and 49E00' N.Long. of origin 109E30' W.Lat. of origin 44E15' N.

Nebraska(single zone)

500,000 0 Standard parallels, 40E00'and 43E00' N.Long. of origin 100E00' W.Lat. of origin 39E50' N.

New YorkLong Island 300,000 0 Lat. of origin 40E10' N.

North Carolina 609,621.22 0

North Dakota, all 600,000 0

Ohio, all 600,000 0

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147

Table 6-2.—U.S. State plane coordinate systems – 1983 datum(continued)

Lambert Conformal Conic projection (continued)

Coordinates of origin (meters)

Zone x y Other Changes

Oklahoma, all 600,000 0

OregonNorthSouth

2,500,0001,500,000

00

Pennsylvania, all 600,000 0

Puerto Rico andVirgin Islands

200,000 200,000 (Two previous zonesidentical except for x and yor origin.)

South Carolina(single zone)

609,600 0 Standard parallels, 32E30'and 34E50' N.Long. of origin 81E00' W.Lat. of origin 31E50' N.

South Dakota, all 600,000 0

Tennessee 600,000 0 Lat. of origin 34E20' N.

TexasNorthNorth CentralCentralSouth CentralSouth

200,000600,000700,000600,000300,000

1,000,0002,000,0003,000,0004,000,0005,000,000

Central meridian 98E30' W.

UtahNorthCentralSouth

500,000500,000500,000

1,000,0002,000,0003,000,000

VirginiaNorthSouth

3,500,0003,500,000

2,000,0001,000,000

Washington, all 500,000 0

West Virginia, all 600,000 0

Wisconsin, all 600,000 0

NOTE: All these systems are based on the GRS 80 ellipsoid. 1 For the International foot, 1 in = 2.54 cm, or 1 ft = 30.48 cm.

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Units

English or metric units should be selected as early in theproject as possible. Conversions are possible, butconvert-ing a large 1-foot contour map to meters is notrivial matter.

Remember that when using several sources of locationdata, the reference datum must be known. Systematicdifferences in location data are generally due to mixingdatums.

Specific Nomenclature and Definitions

Establish a uniform nomenclature system with writtendefinitions for rock types, map units, and map symbolsused. The American Geologic Institute Glossary ofGeology [2] is the standard for geologic terms exceptwhere Reclamation has established definitions for itsown needs. These definitions and nomenclature arediscussed in chapters 2 through 5.

Field Equipment and Techniques

General geologic mapping equipment and techniques arediscussed in field geology manuals such as Lahee (1961)[3] and Compton (1985) [4]. Refer to these texts for dis-cussions of suggested field equipment and generalgeologic mapping techniques.

Use of Computers

Computers are used during a mapping program in fourbasic ways: (1) to process and analyze voluminousnumerical data (e.g., joint data), (2) as a tool in theanalysis of basic geologic data (e.g., construction of pre-liminary or final plan and section views which

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incorporate previously entered geologic data),(3) Computer Aided Drafting and Design (CADD) ofsection and plan views, and (4) in modeling geologicconditions. How computers will be used in the reduction,analysis, and drafting of the geologic data generatedduring a mapping program needs to be decided earlybecause records of field data will depend on whetherdata are to be stored in digital format and restructuringthese data at a later date is costly, time consuming, andintroduces transcription errors.

Right-of-Way

Right-of-way is needed for any mapping of non-Reclamation land and should be obtained early toprevent work delays. Although "walk on" permissionusually is obtained easily, permission for trenching anddrilling may take several months, especially ifarcheological or environmental assessment is necessary.

Records

Systematic methods of recording field observations,traverse data, outcrop data, and trench logs areimportant. Suggested sample field book formats areshown under each section below dealing with specificmapping procedures, but any format should allow clearrepresentation of the field data.

Geologic Considerations

The following are some key items that should beevaluated during a mapping project. The degree ofimportance varies with the project but the factors arecommon to most.

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Lithology.—Differentiation between the various geo-logic deposits and lithologies in a study area is basic togeologic mapping. However, an engineering geologist ismore concerned with the engineering characteristics ofthe unit than with its geologic definition, and these char-acteristics should be the controlling factor in how geo-logic units are subdivided. For some engineeringgeologic purposes, it may be reasonable to consolidategeologic units with similar engineering properties into asingle engineering geologic map unit. Depending on theneeds of the project, lithologic subunits may be definedjointly between the engineers and the geologists workingon the job.

After the basic geologic subdivisions for a mapping jobhave been agreed upon, detailed descriptions of eachsubunit should be compiled and mapping symbolsselected. Map unit definitions usually will applyspecifically to the job or project area and normally will bemodified as additional data are collected. Map symbolsfall into several categories. American GeologicalInstitute data sheets have a comprehensive tabulation ofsymbols.

Geologic contacts.—Two different line types normallyare used on geologic maps to denote the precision andaccuracy of geologic contacts. These are solid and broken(dashed or dotted) lines. Solid lines usually are usedwhere exposures are excellent, such as a cleanedfoundation or an area with nearly continuous outcrops.Solid lines indicate that the contacts are located with aprescribed degree of accuracy. Broken contacts are usedwhen unsure of the accurate location of the contact, i.e.,when the contact is covered by thin slopewash deposits(dashed line) or where the contact is buried by deepsurficial deposits (dotted line). Confidence levels,expressed in feet or meters, for both types of contactsshould be stated clearly in the definition of the contact

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line. The mapper should keep in mind the type of geo-logic data being compiled and use the appropriate line.

Discontinuities.—Discontinuities separate geologicalmaterials into discrete blocks that can control thestability and bearing capacity of a foundation or slope.Intersecting discontinuities in cut slopes can formunstable wedges. Because of the destabilizing orweakening effects, mapping and adequately describingdiscontinuities is critical in engineering geology studies.The various types of discontinuities and the terminologyfor describing their engineering properties are discussedin chapter 5.

Weathering and alteration.—The mechanical andchemical alteration of geological materials can signifi-cantly affect stability and bearing strengths. Adequatelydetermining weathering depths, extent of alteredmaterials and the engineering properties of theseweathered and altered materials is critical inengineering geologic mapping. Refer to chapter 4 fordefinitions of weathering and alteration descriptors.

Water.—The location and amount of groundwater to beexpected in an excavation and how it can be controlled iscritical to the overall success of a project.

Geomorphology.—Study of landforms is often the keyto interpreting the geologic history, structure, lithology,and materials at a site. Exploration programs can bebetter designed and implemented using landforms as abasis. The geomorphic history is important indetermining the relative age of faults.

Vegetation indicators.—Differences in vegetationtypes and patterns can provide indirect data onlithologies, dis-continuities, weathering, groundwater,

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and mineralization. The water holding capacity of soildeveloped on one rock (e.g., shale) may differ con-siderably from the water holding capacity of soildeveloped on another type of rock (e.g., sandstone);consequently, the types of vegetation that grow in thesesoils can vary considerably. Minerals present in theparent rock may affect soil chemistry and may limitvegetation to types tolerant of highly acidic or alkalinesoils or high concentrations of trace elements.Vegetation seeking groundwater moving up major jointsand faults will form vegetation lineations that are highlyvisible on aerial photographs, particularly color infraredphoto-graphs. In most locations, local conditions have tobe assessed to use vegetative indicators effectively.

Cultural features (manmade).—Cultural features,such as water, gas or oil wells, road cuts or foundationexcavations, can provide surface and subsurface dataand should be reviewed early in the mapping project.When data collection through trenching and core drillingprograms is considered, buried utility lines (water, gas,electrical, sewage, or specialized lines) can be hazardousor embarrassing when broken. Usually the utility orowners will locate their lines.

Field checking.—Field checking by both mapper andindependent reviewer is a critical part of the mappingprocess. Field checking after a map is complete allowsthe mapper to check the interpretations at a givenlocation with the geologic concepts developed on the mapas a whole. Field checking by the independent reviewerensures that the basic field data are correct and conformto project standards. Periodic field checking of pre-viously mapped areas can be useful as the mapper'sconcept of the site geology changes with the addition ofnew surface and subsurface data.

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Site Mapping

Engineering geologic mapping has two phases—mappingprior to construction and mapping during construction.In general, the following guidelines are for: (1) generalmapping requirements, (2) suggested equipment, (3) spe-cific preparations needed for the job, (4) type of documen-tation needed, and (5) special considerations that themapping may require. General

Detailed site geologic mapping studies generally are donefor most structures or sites. Site mapping requirementsare controlled by numerous factors, the most importantof which are the type and size of structure to be built orrehabilitated or site to be remediated, the phase of study(planning through operation and maintenance), and thespecific design needs.

Site mapping studies for major engineering featuresshould be performed within an approximate 5-mile (8-km) radius of the feature, with smaller areas mapped forless critical structures. These studies consist of detailedmapping and a study of the immediate site, with moregeneralized studies of the surrounding area. Thisapproach allows an integration of the detailed sitegeology with the regional geology. The overall process ofsite mapping is a progression from preliminary, highlyinterpretive concepts based on limited data to finalconcepts based on detailed, reasonably well-defined dataand interpretation. This progression builds on each pre-vious step using more detailed methods of data collectionto acquire better defined geologic information. Typically,site mapping is performed in two phases:(1) preliminary surface geologic mapping and (2) detailedsurface geologic mapping. All site mapping studies begin

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with preparation of a preliminary surface geologic mapwhich delineates surficial deposits and existing bedrockexposures. The preliminary surface geologic map is thenused to select sites for dozer trenches, backhoe trenches,and drill holes. Surface geologic maps are then re-interpreted based on the detailed surface and subsurfacedata. If required, detailed subsurface geologic data arealso obtained from exploratory shafts and adits.

Suggested Equipment

The following list of basic equipment should meet mostneeds. Not all listed equipment is necessary for everyproject, but a Brunton Compass, geologist’s pick, (2-pound hammer may be necessary for rock sampling),maps, map board, aerial photographs, notebook, scale,tape measure, protractor, knife, hand lens, various pensand pencils, and a GPS should meet most needs.

Preparation

Whether a site mapping program is completed in onefield season or over several years, the overall projectschedule and budget are critical. A critical assessmentshould be made of the time available for the mappingprogram, the skills and availability of personnel toaccomplish the work, weather conditions, and budgetconstraints.

Documentation

Site data are documented on drawings (and associatednotes) generated during the study. The drawings fallinto two general categories—working drawings and finaldrawings. Working drawings serve as tools to evaluateand analyze data as it is collected and to define areaswhere additional data are needed. Analysis of data in athree-dimensional format is the only way the geologist

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can understand the site geology. Drawings should begenerated early in the study and continuously updatedas the work progresses. These drawings are used forpre-liminary data transmittals. Scales used for workingdrawings may permit more detailed descriptions andcollection of data that are not as significant to the finaldrawings. Final drawings are generated late in themapping program, after the basic geology is wellunderstood. Many times new maps and cross sectionsare generated to illustrate specific data that were notavailable or well understood when the working drawingswere made. Final drawings serve as a record of theinvestigations for special studies, specifications, ortechnical record reports.

Preliminary Surface Geologic Mapping.—Thepurpose of preliminary surface geologic mapping is todefine the major geologic units and structures in the sitearea and the general engineering properties of the units.Suggested basic geologic maps are a regional recon-naissance map at scales between 1 inch = 2,000 feet and1 inch = 5,280 feet (1:24,000 to 1:62,500), and a sitegeology map at scales between 1 inch = 20 feet and 1inch = 1,000 feet (1:250 to 1:12,000). Scale selectiondepends on the size of the engineered structure and thecomplexity of the geology. Maps of smaller areas may begenerated at scales larger than the base map toillustrate critical conditions. Cross sections should bemade at a natural scale (equal horizontal and vertical) asthe base maps unless specific data are better illustratedat an exaggerated scale. Exaggerated scale crosssections are generally not suited for geologic analysisbecause the distortion makes projection andinterpretation of geologic data difficult.

Initial studies generally are a reconnaissance-level effort,and the time available to do the work usually is limited.

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Initially, previous geologic studies in the general sitearea are used. These studies should be reviewed andfield checked for adequacy and new data added. Initialbase maps usually are generated from existingtopographic maps, but because most readily availabletopography is unsuitable for detailed studies, sitetopography at a suitable scale should be obtained ifpossible. Existing aerial photographs can be used astemporary base maps if topographic maps are notavailable. Sketch maps and Brunton/tape surveys orGPS location of surface geologic data can be done ifsurvey accuracy or control is not available or necessary.Good notes and records of outcrop locations and data areimportant to minimize re-examination of previouslymapped areas. Aerial photo-graphy is useful at thisstage in the investigation, as photos can be studied inthe office for additional data. Only after reasonablyaccurate surface geology maps have been compiled canother investigative techniques, such as trenching andcore drilling, be used to full advantage. For some levelsof study, this phase may be all that is required.

Detailed Surface Geologic Mapping.— The purposeof detailed surface geologic mapping is to define theregional geology and site geology in sufficient detail sogeologic questions critical to the structure can beanswered and addressed. Specific geologic featurescritical to this assessment are identified and studied,and detailed descriptions of the engineering properties ofthe site geologic units are compiled. Projectnomenclature should be systematized and standarddefinitions used. Suggested basic geologic maps aresimilar to those for preliminary studies, althoughdrawing scales may be changed based on the results ofthe initial mapping program. Maps of smaller areas maybe generated to illustrate critical data at scales largerthan the base map.

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The preliminary surface geology maps are used to selectsites for dozer trenches, backhoe trenches, and drill coreholes. As the surface geology is better defined, drill holelocations can be selected to help clarify multiple geologicproblems. Detailed topography of the study site shouldbe obtained, if not obtained during the initialinvestigations. Data collected during the preliminaryinvestigations should be transferred to the new basemaps, if possible, to save drafting time. Field mappingcontrol is provided primarily by the detailed topographicmaps and/or GPS, supplemented by survey control ifavailable or Brunton/ tape survey. If not, large scaleaerial photographs of a site area flown to obtain detailedtopography are useful in geologic mapping.

Dozer Trench Mapping

General

Dozer trenches are cut to expose rock or unconsolidatedmaterials below the surface and major surface creep.Walls normally should be excavated vertically, free ofnarrow benches and loose debris. Upon completion ofexcavation, floors must be cleaned below any depth ofripping, loose rubble should be removed, and a newsurface exposed. Structures such as contacts and shearzones must be traceable from wall into floor for optimumdetermination of their nature and attitude. Thegeologist is responsible to ensure the dozer operatorproduces a safe finished trench that meets Reclamationand Occupational Safety and Health Administration(OSHA) safety standards. If livestock are present,fencing of the trench with four strands of barbed wiremay be required. After trench logging is completed,decide whether to leave the trench open or to backfill. Atsites with complex geology, it is desirable to leave the

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trench open for reinterpretation of the trench in light ofnewly acquired data. Backfilling of the dozer trench maybe necessary where an open trench would be a safetyhazard. Generally, all trenches should be backfilled andcom-pacted prior to abandonment.

Suggested Equipment

Additional equipment needed may include hard hat,scraper or putty knife, square-nosed shovel, plasticflagging, nails, wooden stakes, surveyors chain or tapemeasure (feet or meters) and log book. Use putty knife,shovel, and whisk broom for cleaning trench exposuresand a Brunton tripod for more accurate trench bearings.

Preparation

Prior to working in a dozer trench, the geologist shouldinspect the excavation trench walls for failure planes(obvious or incipient) or loose materials. These should beremoved before mapping starts. An examination of thewhole trench should be made at the start of each workperiod. A baseline should be laid out along the toe of thetrench wall or at the top of the excavation. Becausedozer trenches often are not straight, the trench shouldbe divided into a series of straight segments withstations established at each point where the trenchchanges direction. Each station should be marked by astake, tied with flagging, and marked with the trenchnumber and station letter (e.g., DT-12A). Flaggingstrips should be nailed to the wall approximately 6 feet(2 meters [m]) vertically above or below the station foranother reference point in case minor sloughing buries ordislodges the stake.

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Documentation

The scale and format selected for logging a backhoetrench depends on the type of data needed and theamount of detail to be illustrated. Typical dozer trenchlog scales are between 1 inch (in) = 5 feet (ft) (1:100) and1 in = 10 ft (1 : 200), but scales of 1 in = 1 ft (1: 50) maybe required in critical areas to adequately showstructural and stratigraphic details. If trench geology isnot complex, record trench logs, along with names of thefield party and date in a field book. Determine andrecord the bearing, slope distance, and slope anglebetween each station. Survey the coordinates andelevations of each station. Orient the log book so thesketch and description may be viewed together (seefigure 6-2). Sketch the walls and floors across the toppage of the open log book. Mark the baseline at 5-foot(1.5-m) intervals and draw a single "hinge line”; wallabove, floor below. Determine the vertical heights of thetrench walls at each station and between stations, if theprofile or thickness of surficial materials changesbetween stations.

Sketches should be accurate and illustrate the fieldrelationship of soil and geologic units and structures.Use nails and flagging strips to mark obscure contacts orother features for ready reference during logging.Designate geologic units by name and symbol. Accuratelyplot the attitude of contacts, bedding, foliation orcleavage, faults, shear zones, and joints where they aredetermined using standard symbols, and write adescription. If attitudes are determined from the wall,they may be projected along strike into the floor, if nochange is apparent in the floor. Note and show thebedding or foliation wherever relationships are complexand differ from the recorded attitude (i.e., where surfacecreep, drag folds, or disturbed zones are exposed in thewall). Record unit attitudes that may have beenaffected

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Figure 6-2.—Sample trench log.

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by surface creep or slumping. Written descriptions ofsoil and rock units and structural zones should berestricted to the page below the sketch and should notbe written over the sketch. Main heading for writtendescriptions are restricted to mappable geologic units.Intervals are noted where the contacts intersect thebaseline. Indent subheadings within text to describelithologic or structural variations within the mappableunit. An example of heading order is as follows:

DT-58, Sta. B-C, Distance - 27.5', Bearing - S. 45EW., Slope + 2 22.5-50.0': Metasediments (description) 39.9-41.0': Chlorite Schist B (description) 47.5-49.0': Talc Schist (description) 48.2-48.4': Shear Zone (description)

Stratigraphic units should be colored to complete the log.Photograph the trench to complement the log or to recordspecific details within the trench.

Backhoe Trench Mapping

General

Backhoe trenches are excavated to expose rock orunconsolidated materials below surficial deposits andmajor surface creep. Generally, backhoe trenches areexcavated at sites which must be returned to near-original conditions and where dozer trenching wouldproduce unacceptable damage. Backhoe trenches oftenare excavated in the floor of an existing dozer trench todeepen the excavation. Walls should be excavatedvertically and free of narrow benches and loose debris.In most cases, the trench should be about 3 to 3-1/2 feetwide (1 m) (width of standard backhoe bucket), 10 to 12

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feet (3 to 3.6 m) deep, and slope at one end for easyaccess. Upon excavation completion, hydraulic trenchshores are placed and pressurized or wooden shoresconstructed to support the trench walls. Shoreconstruction and spacing must meet OSHA standardsand standards outlined in Reclamation's ConstructionSafety and Health Standards manual. At no time shouldpersonnel enter unshored portions of the trench over5 feet deep. The geologist who oversees the excavationof the backhoe trench is respon-sible for the constructionof a safe, stable trench.

After trench logging is completed, decide whether toleave the trench open or to backfill. At sites withcomplex geology, leave the trench open, if possible, asthis allows reinterpretation of the trench in light ofnewly acquired data. However, backhoe trenches areprone to sloughing with time, even when supported, andbackfilling of the trench may be necessary for safetyreasons. The coordi-nates and elevation of each end ofthe backhoe trench should be surveyed prior tobackfilling.

Suggested Equipment

Standard field equipment is used during backhoe trenchmapping. Additional equipment may include a hard hat,large knife, flat-blade pick or army trenching tool toclean off trench walls, putty knife, whisk broom, nails,flagging, twine, small string level, 100-foot (30-m) longsurveyor's chain or tape, and map board or log book. Thetype of backhoe needed depends on how consolidated orcemented the material is, site accessibility, and depth tobe excavated. Most of the larger, rubber-tired backhoesare suitable for excavation of typical trenches, but wellconsolidated or cemented material, steep site terrain, ortrench depths over about 12 feet (3.6 m) may require alarger track-mounted hydraulic excavator.

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Preparation

Each day prior to working in a backhoe trench, thetrench along both sides and the trench walls should beexamined for incipient fractures or loose materials,particularly within the surficial materials. These loosematerials should be removed before work starts.Hydraulic trench shores should be checked visually forleakage and for loss of pressure by pushing on them witha foot. Re-pressure any loose shores and replace leakingshores. The stability of each shore should be checkedbefore the mapper's weight is put on it, particularly ifthe shore is to be used to examine the upper trench wallor to climb out of the trench.

A backhoe trench must be cleaned prior to logging.During excavation, the backhoe bucket may smear clayand silt along the walls, obscuring structural and strati-graphic relationships. This smeared zone may be any-where from a fraction of an inch thick to several inchesthick, depending on the amount of fines and moisture inthe material excavated. The smeared material can beremoved by chipping or scraping with a large knife, flat-bladed pick, or army trenching tool. If the trench isexcavated in reasonably consolidated material and thetrench is free draining, a high pressure water and/or airjet will remove this material. Both walls should be spotcleaned and examined prior to major cleaning to deter-mine which wall exposes the best geologic data. Usuallyonly one wall is completely cleaned; the other wall is spotcleaned during trench logging to expose another view ofcritical features or relationships. After a wall is cleaned,a horizontal base line is established. The baseline is runat about eye level and constructed by stringing twinebetween nails driven into the cleaned trench wall. Thetwine can be leveled using a small string level (availablein most hardware stores) prior to driving nails. Whenthe baseline becomes either too high or too low for

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comfort-able measurements, a vertical offset of the stringline is made and the baseline continued at the newhorizon. In complex, critical areas where accuratelylocated contacts are needed, a string grid with horizontaland vertical elements can be constructed off the baselineto assist in mapping.

Documentation

The scale and format selected for logging a backhoetrench depends on the type of data needed and theamount of detail to be illustrated. Typical backhoetrench log scales are between 1 in = 5 ft (1:100) and 1 in= 10 ft (1 : 200), but scales of 1 in = 1 ft (1 : 50) may berequired in critical areas to adequately show structuraland stratigraphic details. If trench geology is notcomplex, a notebook is suggested. The log book shouldbe oriented so the sketch and description may be viewedtogether. The names of the field party, date, trenchnumber, location, and other pertinent data should berecorded. If trench geology is complex and a larger scaleis desired, cut sheets of grid paper attached to a mapboard may be used. These sheets are usually redraftedafter trench logging is completed. If the backhoe trenchis wet or wall material is sloughing down onto the mapboard, a blank grid sheet can be taped to the map boardand overlain by sheets of mylar. Trench data sketchedonto the mylar will not be smeared as easily, and thesheets can be erased without tearing. Prints of thesheets can be made for use in preliminary datatransmittal or as check prints for field checking. Figure6-3 shows a completed trench log.

Because the log sheets are separated easily, each sheetshould be marked with the names of the field party,date, trench number, location, and other pertinent data.

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165 Figure 6-3.—Sample completed trench log.

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Begin trench logging by recording the trench bearing.Begin at one end of the trench; place a surveyors chainor tape along the horizontal base line string. Verticaldistance of the trench wall above and below the base lineshould be measured every 10 feet (3 m) or so and thetrench outlines sketched. Sketches must be as accurateas possible to illustrate the field relationships of soil,geologic units, and structures. Use flagging to markobscure contacts or other features for easier logging.

Intervals for the various geologic units and features areto be noted where the contacts intersect the baseline.Contacts above and below the baseline are located by twomeasurements—the vertical distance from the baselineand baseline distance—and sketched onto the log.Geologic units should be designated by name or symbol.Symbols to illustrate the attitude of contacts, bedding,fol-iation or cleavage, faults, shear zones, and jointsshould be drawn at the point where determined and alsore-corded in the written description. Bedding or foliationshould be depicted and noted wherever relationships arecomplex and differ from the recorded attitude (i.e., wheresurface creep, drag folds, or disturbed zones are exposedin the wall). Attitudes on units that may have beenaffected by surface creep or slumping should also be sonoted.

Written descriptions of soil and rock units and structuralzones should be restricted to the area below the sketch.Main headings for written descriptions are restricted tomappable geologic units. Description format is similarto that discussed for dozer trench mapping. After trenchlogging is completed, geologic units should be colored tocomplete the log and the trench field checked. Photo-graph the trench to complement the trench log or torecord specific details within the trench. The limitedspace and poor lighting conditions in a backhoe trench

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many times make it difficult to obtain satisfactoryphotos. Generally, cameras capable of closeup focusingand loaded with fast film work best. Photographs takenwhile standing at the top of the trench generally aremarginal because of poor lighting and perspective. Theends of the trench should be located by GPS or survey.

Construction Geologic Mapping

Geologic mapping during construction is to: (1) identifyand delineate potential or actual construction-relatedneeds and problems; (2) verify and better define geologicinterpretations made during design studies, particularlyfor critical geologic features and properties;(3) determine if the geologic conditions are as interpretedduring the design phase and ensure that the actualconditions revealed are as interpreted. If thoseconditions are not as interpreted, design modificationsmay be required; and (4) provide a record of as-builtconditions in the event of litigation or operationalproblems.

To obtain meaningful data for mapping during con-struction, cooperation and coordination between theContractor and the construction staff is required. Thefield geologist prioritizes mapping; and when the specificarea is ready for mapping and approval, the staff andsurveyors (if required) should accomplish the work asquickly as possible. Photographs should be taken usingappropriate photographic equipment. All photographsshould be captioned and dated.

Possible safety hazards that might occur during mappingshould be evaluated, and appropriate precautions shouldbe taken.

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Large Excavation Mapping

General

Construction considerations prepared before constructionbegins should contain guidelines for the mapping of spe-cific features. The scope and detail of mapping requiredat each portion of the site should be determined andsuitable mapping scales determined. Suggested scalesfor detailed foundation mapping are 1 in = 5 ft to 1 in =50 ft (1:50 to 1: 600), generalized foundation invert mapscale 1 in = 20 ft to 1 in = 100 ft (1:20 to 1:1,000).Detailed, as-built foundation geology maps are used infinal design modification, as a final record, and for use inpossible future operation and maintenance problems.Mapping can be done on detailed topographic base mapsgenerated from survey control, GPS, or plane table.Preferably, geology points are flagged and surveyed by asurvey crew. Terrestrial photography, photogrammetry,and GPS can also be used to supplement mapping.Detailed photo-graphy of the entire foundation isimportant for inclusion in the final construction geologyreport and as a part of the construction record. Usestandard nomenclature and symbols both on maps andphotographs, but be consistent with those used in earlierstudies and specifications. Use a systematic method ofcollecting mapping data, then compile these data into auseful and accurate geologic map.

Detailed, as-built geology maps of cutslopes are requiredin delineating and solving major slope stability problemsand in selecting general slope support systems. Recom-mended scale selection for detailed cut-slope geologymaps are 1 inch = 10 feet to 1 inch = 50 feet (1:100 to1:600), generalized cutslope geology maps use a scale1 inch = 20 feet to 1 inch = 100 feet (1:200 to 1:1,000).Generally, maps are on detailed topographic base maps

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generated from survey control. Geologic points may beflagged for survey by survey crews. Detailedphotographs of the slopes are important.

Steep Slope Mapping

General

Define the purpose and goal for mapping and researchthe stratigraphy and structural geology prior to starting.Select scaling and safety equipment for specific areas.

Preparation

Special training is required for scaling. While scalingand mapping, a pocket tape recorder and camera areuseful for documentation.

Suggested Equipment

Use the appropriate scaling equipment and systems.Standard mapping equipment needs to be reviewed andmodified for scaling operations.

Documentation

Establish ground control for mapping including ter-restrial photo mapping. Data collected while scalingshould be based on the purpose of mapping and detailrequired. Establish general map controls such as gridcontrols.

Special Considerations

Select specific portions of an exposure to be mapped.

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Canal and Pipeline Mapping

General

In reconnaissance investigations, surface geologic map-ping is used to determine the most feasible alignment,which may be representative of the geologic conditions tobe encountered, the lining requirements, andconstruction materials available. Design datainvestigations along canal alignments must be detailedenough to determine the final alignment and allassociated requirements for specifications andconstruction.

Preconstruction investigations for canals and pipelinesare less detailed because of the long distances involved.Consequently, geologic construction mapping isnecessary to verify preconstruction assumptions,document changes from original assumptions, andprovide data for potential design changes or claimanalyses.

Preparation

General field mapping requirements.

Documentation

Pertinent geologic data that should be shown on the basemaps include: soil and geologic units, all natural andmanmade exposures, geologic structures, springs andseepage, surface channels, and potentially unstableareas. Where appropriate, photographs with overlays ordetailed site-specific drawings should be used to showsurface conditions in relation to the canal prism orassociated canal structures. Base maps should be planstrip topo-graphy or orthophotography with scales of 1 in= 20 ft (1:400) to 1 in = 100 ft (1:2,000) with associatedtopographic profiles.

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Underground Geologic Mapping

General

This is a general guide for recording tunnel geology anddescribes mapping requirements and procedures. Thisguide and the field geologist's judgement and experienceshould permit development of geologic data whichadequately document geologic factors that are significantto design, construction, and stability of tunnels andshafts. Some of the necessary data may be obtainedfrom other project personnel such as engineers,surveyors, and inspectors. The following items are ofprimary impor-tance during the construction orexploration for a wide range of tunnel and shaft types,excavation problems, geologic conditions, and contractadministration require-ments. The data recorded andthe emphasis given each item should be determined foreach specific tunnel. (Note: references to tunnels applyequally to shafts)

Three principal objectives are to:

• Acquire progressive, timely mapping of allsignificant geologic features as exposed during theadvance of the tunnel or shaft. These initial fea-tures are important for subsequent identification ofchanges which may take place, such as water flow,rock slaking, or support behavior, as the headingprogresses and before lining or other completionmeasures are undertaken.

• Facilitate periodic transmittal of these data in pre-liminary form to the office so that conditions beingencountered and their effect on the excavation canbe used in immediate evaluation of currentconstruction activities and anticipation of futureexcavation conditions.

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• Assure that a systematic, clear, record of geologicconditions is compiled for design reviews and use bythe project and contractor. These data should beincluded in the final construction geology report.These records may prove invaluable during subse-quent operation and maintenance and in theplanning and design of future tunnels and shafts. Ifgeologically related problems occur, these data willbe essential in evaluating the conditions.

Accuracy is essential, and consistency of data shown ontunnel maps is vital. If the maps are used in contractclaim negotiations or in litigation, even a few errors orinconsistencies may compromise the entire map.

The preparation of an adequate tunnel or shaft geologicmap requires a careful study of geologic structure, lith-ology, mineralogy, groundwater, and their effects on rockquality and behavior, tunneling methods, stability, andsupport. The preparation of a tunnel or shaft geologicmap is a geologic mapping process; geologic data shouldbe recorded directly on the map while making the obser-vations and not described in notes for subsequentdrafting in the office. An appropriately scaled tunnel orshaft mapping form, prepared prior to starting themapping, is essential to systematic data collection. One-matte-sided mylar tunnel forms should be used in wetexcavations and are recommended as a standard for alltunnel and shaft mapping. Figures 6-4 and 6-5 areexamples of field mapping forms. The use of mylars inall tunnels facili-tates copying and immediate use. Theextent or amount of mapping detail for a specific tunnelor shaft will depend on the driving method, geologicconditions, and design considerations. For example,tunnel face (head-ing) maps can be obtained under mostconditions when conventional excavation (drill/blast)methods are used but are difficult to obtain in tunnelsexcavated by tunnel

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173 Figure 6-4.—Tunnel mapping form with key alphanumeric descriptors and mapping data.

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Figure 6-5.—Tunnel mapping form with blocks for title and geologic data.

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boring machine (TBM). TBM excavated tunnels may bemore difficult to map than conventionally excavatedtunnels, depending on the level of detail required,machine configuration, and the support method.However, the key rock characteristics relative to tunnelstability must be mapped. In tunnels where shotcrete orprecast segments are used for support, detailed mappingmay be impossible; this does not cancel the requirementfor mapping and recording of important data on thegeologic conditions. The geologist must obtain requireddata with the available resources and under the specificconditions. These guidelines apply to all tunnel or shaftexcavations regardless of whether the mapping isperformed during project planning, design data acqui-sition, or construction.

Safety

Underground construction activities are inherently morehazardous than surface construction. Before workingunderground, the specific safety requirements for theparticular tunnel should be determined. Self-rescuertraining commonly is required, and the safety require-ments as described in the Reclamation Safety and HealthStandards [5] should be reviewed. Additional training oradditional requirements may exist under specialcircumstances such as gassy conditions. Beforebeginning work, a familiarization tour of the work site(including the underground workings) should be madewith project personnel, such as an inspector, intimatelyfamiliar with the job. Also, assume that every piece ofequipment and worker is out to get you; you shouldalways maintain an awareness of what the workers andequipment are doing around you.

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General Preparation

Tunnel construction is essentially a linear activity. Allaccess, equipment haulage, and work activities takeplace in a line. The mapping process should be plannedsuch that a minimum number of trips to the heading arerequired and a minimum amount of time is spent at theheading. Geologic mapping can usually be integratedinto an optimum part of the construction cycle.Unnecessarily spending time at the heading is not onlyinefficient but can interfere with the constructionprocess by adding to an already congested situation.

Available geologic data should be reviewed andestablished nomenclature used as appropriate. Geologicfeatures described in the available literature should bespecifically investigated while mapping, especially thosedescribed in specifications documents. Forms should bedesigned to expedite the work as much as possible(figures 6-4 and 6-5), required mapping equipment mustbe available, and the construction cycle should be ana-lyzed to determine the best and safest time to map.Tunnel map sheets should be a convenient size such as8.5 x 11 inches (A4) or 11 x 18 inches (A3). This permits100 feet (30 m) of tunnel on a scale of 1 inch = 10 feet(1:200) with sufficient space for concise explanations anda title block. The geology should be mapped in thetunnel directly on the matt side of mylar film. This map,developed in the tunnel, can be edited and copied forquick transmittal to the office. The value of current datacannot be overemphasized. Except under very specialconditions, the recording of geologic data in a notebookwithout mapping for subsequent preparation of a graphictunnel map is unacceptable. Without a graphicrepresen-tation during data acquisition, theinterrelationships of geologic data cannot be properlyevaluated, and data are missed or errors are introduced.Some items listed above will not apply to every tunnel,

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and some items may be shown more appropriately in asummary tunnel map (figure 6-6). This map presents asummary of essential engineering and geologicrelationships. Plotting engi-neering and geologic data asa time line permits direct comparison of geologicconditions, supports installed, overbreak, excavationrate, etc., for correlation. Sum-mary sheet scales mayrange from 1 inch = 10 to 100 feet (1:100 to 1:1,000)depending on amount of data and complexity of thegeology. Ongoing maintenance of these data avoidsexcessive compilation time after construction iscompleted. A summary tunnel map is required ontunnels for construction records.

When several individuals are mapping and/or contractrequirements hinge on geologic data, e.g., payment basedon ground classification, a project or specific mappingmanual may be necessary. A manual provides an easyreference for data requirements and format, reducesinconsistency between geologists, and sets a specificmapping standard.

Excavation Configuration

Conventionally excavated tunnels are usually a modifiedhorseshoe shape. Departures from this shape areusually for a special configuration or when groundconditions dictate a circular shape for optimizing support effective-ness. Machine-excavated tunnels are round if boredunless a road-header type machine is used. Road-headerexcavated tunnels are usually horseshoe shaped for con-struction convenience. Shafts are almost always roundfor optimizing support effectiveness and because mostare drilled or bored either from the surface or raise-boredfrom the bottom. Exploratory shafts may be sunkconven-tionally if shallow. Whatever the shape, the mapformat should be designed to minimize the amount ofprojection

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and interpretation required. Whenever possible, the fullperiphery mapping method should be employed.

Data Requirements

The relationship of the geology to the engineeringaspects of the tunnel or shaft is of primary importance.If geologi-cally related problems occur, the recorded datawill be valuable to the geologist and engineer inevaluating the conditions, the cause(s), and in devisingremedial measures. In most cases, geologicdiscontinuities, such as joints, faults, bedding, etc., arethe most important factors affecting excavation stability;and these data are of primary importance. Also, the rockstrength is important in high cover tunnels, and water isimportant in many situations. The following data aremost important:

1. Rock Classification.— Lithology and relatedfeatures such as foliation, schistosity, and flow structure.Rock descriptions should be concise; use standarddescriptors.

• Formation boundaries — describe beddingthick-ness and attitude, areas of soft, or unstablerock. Give dip and strike unless otherwise noted.Dips of planes (not necessarily true dip) into tunnelare desirable in cases where they may influenceexcavation stability.

• Physical properties of the rock — determinehardness by comparison with common or familiarmaterials, brittleness, reaction to pick or knife, andcolor.

• Alteration — describe degree, type, extent, andeffects on construction. Differentiate between wea-thering, other alteration, and cementation.

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• Features — describe the size, form (tabular,irregular), contacts (sharp, gradational, sheared),and mineralization, if any.

2. Conditions Which Affect Stability of the Rock.—

• Joints or joint systems — describe spacing,conti-nuity, length, whether open or tight,slickensides, planarity, waviness, cementation,fillings, dip and strike, and water.

• Shear zones — describe severity of shearing andphysical condition of rock in and adjacent to thezone, whether material is crushed or composed ofbreccia, gouge, or mylonite; describe gougethickness, physi-cal properties, mineralogy andalteration; dip and strike, and water.

• Faults — give dimensions of fault breccia and/orgouge and adjacent disturbed or fractured zones,amount of displacement, if determinable, and thefault's effect on stability of rock.

3. Effects of Tunneling on Rock.— Comment on: thecondition of rock after excavation, rate of air slaking orother deterioration of rock where appropriate, rockbursts, fallouts, development of squeezing or heavyground, and time interval between first exposure and thebeginning of these effects. Include the evidence used inevaluation, and the reaction of different rock types toconventional blasting or mechanical excavation method.

Periodic re-examination of the tunnel and comparison oforiginally mapped conditions with those existing later isrecommended.

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4. Tunnel Excavation Methods.—

Blast pattern — Give example of typical blast roundpattern, type of explosive and quantity per yard(powder factor) of rock blasted, size of rock fragments,ease or difficulty of rock breakage and condition of thewalls of the tunnel such as whether half-rounds (halfof peripheral shot holes) are visible. Some of thisinfor-mation should be obtainable from the inspectors.

Overbreak — Overbreak and fallout should be mea-sured as a peripheral average from "B" line (excavationpay line), where practical, and maximum at specificstations. Plot average overbreak on the section alongtunnel alignment. Relate this to geologic conditionsand construction methods, particularly blastingprocedure.

Ground behavior — Blockiness, caving, swelling,and/ or squeezing should be described with evidenceand effects.

Supports — Give size and spacing of ribs, size andtypes of struts, and behavior of supports in reaches ofbad ground. Where supports show distress or havefailed, give reason for failure, time after installationfor load to develop, the remedial measuresundertaken, and size and spacing of replaced supportsor jump sets. If a ground classification system is beingused, relate to geologic conditions and support used.Incorporate some reference to the actual need forsupport versus that installed. Use the properterminology when describing supports. A goodreference for tunnel supports (and conventionaltunneling) is Rock Tunneling with Steel Supports [6].

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Indicate where special supports such as mats, spiling,or breast boards are required and geologic reason.Where rock bolts (or split sets) are used, give spacing,size, length, type, anchor type, torque loading values,and quantities used. Note retorquing, if performed.Locations of rock bolts should be plotted on thegeologic maps.

Machine excavation — In machine-type excavations(in addition to appropriate items above) give: rate ofadvance, pressures used, and description of cuttings orrock breakage. Describe the effect of cutters andgrippers on rock walls, or other geologically relatedproblems such as abrasive rock wearing cutters.

5. Hydrogeology .—Water flows should be mapped andquantities estimated. Daily heading and portal measure-ments should be recorded. The location of all significantflows should be plotted on the tunnel map and changesin rate or duration of flow recorded. If the water ishighly mineralized, obtain chemical analyses of water forpos-sible effect on concrete or steel linings orcontamination of water being discharged or to beconveyed by the tunnel.

6. Gas.—The following should be done:

• Determine type, quantity, occurrence, geologic asso-ciations, and points of discharge should be mapped.

• Samples should be taken. This is usually done bysafety personnel.

• Record actions taken.

7. Instrumentation, Special Tests, Grout, andFeeler Holes.—Locations and logs (if available) shouldbe shown on the tunnel maps.

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8. Miscellaneous Excavations.—Geologic maps andsections of related excavations such as surge tanks, gateshafts, inlet and outlet portal open cuts are necessary.

Tunnel maps should include brief comments on thegeologic conditions being encountered and their possibleeffects.

9. Sampling.—A systematic sampling program of thetunnel rock is essential to adequately record tunnelgeology. These samples may be 2 in x 3 in (5 cm x 8 cm)or larger and should be secured in a labeled sample bagshowing station, date, and wall position with anappropriate description. Rock that easily deterioratesshould be protected with wax or plastic. Sampling atirregular (and locally close) intervals may be required toensure that all important rock, geologic, and physicalconditions are adequately represented. A representativestratigraphic series of samples should be collected. Thejudgement of the geologist who is familiar with thegeology is the best guide in determining the mostappropriate sampling interval.

Thorough photographic coverage provides a visual recordof construction and geologic conditions. Postconstructionevaluations use construction photographs extensivelyand are an important part of the construction record. Acamera should be part of the mapping equipment androutinely used. Photographs that show typical, as wellas atypical, geologic conditions should be takenroutinely. Identify photographs of significant features bynumber on the appropriate map sheet.

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Underground Geologic Mapping Methods

Full Periphery Mapping

The full periphery (or developed surface) mappingmethod is widely used in engineering practice andinvolves creating a map of the surface of theunderground excavation regardless of shape. Themethod produces a map which is virtually free fromdistortion and interpretation present in other methodswhere geologic features are projected onto a plane orsection. The method has been used successfully invarious types and shapes of excavations (Hatheway,1982 [7]; U.S. Army Corps of Engineers, 1970 [8];Proctor, 1971 [9]) and on numerous Reclamationprojects.

The method uses a developed surface created by"unrolling" or "flattening out" the circumference of thetunnel or shaft to form a "plan" of the entire wall surface(figure 6-7). The geologic features are plotted on thisplan. The method is especially effective in that geologicfeatures of all types can be plotted directly onto the mapregardless of orientation or location with no projectionrequired. The method is useful for plotting curving orirregular discontinuities which are difficult to project toa flat plane as in other methods.

Procedure.—Full periphery mapping generally requiresthe assembly of field sheets prior to the actual start ofmapping. This is done for drifts and tunnels by firstdrawing in the crown centerline of the plan (figure 6-7).The bases of the walls or the invert are then plotted at acircumferential distance from the crown centerline onthe plan. For instance, if the tunnel is 10 feet (3.048 m)in excavated diameter, the invert centerline will beplotted 15.71 feet (4.79 m) (in scale) from the crowncenterline. Plot springline at the appropriate circumferential

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distance from the crown centerline. This process is donefor both walls and produces a plan which represents theactual wall surface of the excavation. The map layout isdesigned to be viewed from above the tunnel. Shaft dataare plotted as viewed from inside the excavation. Thetunnel invert is not mapped because rock surfacesusually are covered with muck or invert segments. Plotscales on either side of the plan to provide distancecontrol while mapping. A longitudinal section view ofthe excavation may be added alongside the plan toprovide a space to record types and locations of support,overbreak, etc. Plot geologic features on the field sheets(figures 6-4 and 6-5) by noting where the featuresintercept known lines, such as where a particular jointintercepts the crown centerline, the spring line on bothwalls, or the base of either wall. The trace of the joint issketched to scale between these known points. Thestrike and dip of the discontinuity are recorded directlyon the field sheet adjacent to the trace. The locations ofsamples, photographs, water seeps, and flows are plottedon the map (figure 6-8).

The Brunton compass is used to measure dips on thevarious discontinuities; but due to the presence ofsupport steel, rock bolts, utilities, and any naturalmagnetism of the wall rock, a Brunton may not bereliable for deter-mining the strike of the feature. Inthis case, the strike may be determined by one of severalmethods. The first method is to align the map parallelto the tunnel where the feature is exposed in the walland plot the strike by eye on the sheet parallel to thestrike of the feature in the wall. The second method isto observe the strike of the feature on the map where itintersects the crown centerline. At this point, the crownis essentially hori-zontal, and the trace of the feature atthis point represents the strike. The third method isslightly more complex but is the most accurate methodof the three.

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Figure 6-8.—Full periphery geologic map example.

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This method requires locating where the feature inter-sects springline on each wall of the full periphery map.These points are projected to the corrected springline. Aline drawn between the projected points represents thestrike of the feature. Note that these methods assumethat the tunnel or drift is relatively horizontal. In somecases, if the excavation is inclined, the apparent strikecan be corrected for the amount of inclination. A fourthmethod is to use a gyroscopic compass.

Other Applications.—With minor variations in themethod described above, the full periphery method canbe used equally well in vertical or inclined shafts,horseshoe shaped drifts and tunnels, and other regularshaped excavations.

Advantages.—The full periphery method:

• Involves plotting the actual traces of geologicfeatures as they are exposed in the tunnel. Thiseliminates the distortion and interpretation introducedby other methods where the traces are projected backto a plane tangent to the tunnel.

• Allows the geologist to observe and plot irregu-larities in geologic features and make accurate three-dimensional interpretations of the features.

• Allows rapid and easy plotting of the locations ofsamples and photographs.

• Allows easy and rapid recording of the locations ofrock bolts and other types of rock reinforcement.

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Disadvantages.—

• Since the surface of the excavation is generally acurved surface, the trace of planar features, such asfractures, faults, and bedding planes, produce curveswhen plotted on the map.

• The full periphery method requires that the pointsat which features intersect springline be projected tothe original tunnel diameter in order to compute thetrue strike of the discontinuity (figure 6-7).

Plan and Section

The plan and section method has been used in engi-neering practice but has generally been replaced by thefull periphery mapping method. The plan and sectionmethod is still used where data interpretation isfacilitated by the flat plan and sections. The methodcreates vertical sections commonly coincident with a wallor walls of a tunnel or shaft, through centerline, or istangent to a curving surface commonly at springline oran edge of a shaft (figure 6-9). Geologic features areprojected to the sections and plotted as they are mapped.

The method produces a map which is a combination ofdirect trace and projection or a projection of the wallsexcept where the map is tangent to the excavation(figure 6-10). The plan through tunnel springline andcenterline or shaft centerline is a projection of thegeologic features exposed in the excavation.

Procedure.—The plan and section method generallyrequires the assembly of field sheets prior to the actualstart of mapping. This is done for drifts and tunnels bydrawing vertical sections the height of the excavation.

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Figure 6-9.—Map layout of a tunnel for geologic mapping.

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Figure 6-10.—Relationship of planar feature trace to map projections.

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The bases of the walls or the invert form the base of thesection with springline plotted and the crown formingthe top of the section. For instance, if the tunnel is 20feet (6 m) high, the crown will be 20 feet (6 m) from theinvert. Springline is plotted the appropriate verticaldistance from the crown or invert (figure 6-10). Thisprocess may be done for one or both walls, producing oneor two vertical representations of the wall/arch exposure.Shafts are similar, but the section corresponds to thewall of a rectangular shaft or is tangent to the shaft wallat a point, and the map is a projection of the shaft of onediameter.

A section through tunnel springlines produces a planprojection of the arch except at the plan intersection withthe wall at springline. The corresponding sectionthrough a shaft produces a vertical projection of thewall(s) through a shaft or along a diameter. The maprepresents the actual wall surface of the excavation onlywhere the projection intersects the wall.

Scales are added on either side of the sections to providedistance control while plotting. An additional longitu-dinal section view of the excavation may be added to pro-vide a space to record types and locations of support oroverbreak. Geologic features are then plotted on thefield sheets by noting where the features interceptknown lines, such as where a particular joint interceptsthe crown centerline, the spring line on both walls, or thebase of either wall. The trace of the joint is then pro-jected to the section between these known points. Theattitudes of features are recorded on the field sheet adja-cent to the trace. The location of samples, photographs,water seeps, and flows can be recorded by finding theirlocation on the wall and projecting that location to themap.

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Advantages.—The plan and section method:

• Produces two-dimensional sections and plans that donot require conversion. The sections and plans can beintegrated directly with other plans and sections. Thesections and plans are easily understood by individualsnot familiar with full periphery mapping or individualswho have difficulty visualizing structural features inthree-dimensions.

• Permits direct determination of strikes by spring-line intersections.

Disadvantages.—Since the surface of the excavation isgenerally a curved surface, the trace of planar features,such as fractures, faults, and bedding planes, are projec-tions to a plane. The only objective data is where themap is coincident or tangent to the excavation surface.

The plan and section method requires:

• Plotting and observing geologic features and makingaccurate three-dimensional interpretations of thefeatures by projecting locations to a plane.

• Plotting locations of samples and photographs byprojection.

• Recording locations of rock bolts and other types ofrock reinforcement by projection.

• Plotting is done after data collection and re-examination of the site is difficult or not practical.

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Face Maps

The geology exposed in an excavation face is plotteddirectly on a map. The purpose of the face map is toprovide a quick appraisal of rock conditions and providedata for special detailed studies. The combination ofwall and face maps will usually give an adequate andclear permanent record of any complex tunnel geology.Natural scales such as 1 inch = 1 to 2 feet (1:50) are themost satisfactory. All significant geologic features whichmay affect the stability of the tunnel must be mapped.

Photogrammetric Mapping

Photogrammetric geologic mapping is a specializedmethod consisting of the interpretation of close-rangestereophotography of excavation walls. Photogrammetriccontrol is provided by surveyed targets or by a gnomon orscale in the photographs. The stereophotos are inter-preted using photogrammetric software or an analyticalplotter. Feature location accuracy can vary from a fewinches (cm) to one-eighth of an inch (3mm) depending onequipment and survey control accuracy. The photogram-metric mapping can be combined with detail line surveysfor small-scale data collection and control.

Exploration Mapping Method Selection

The geologic mapping format for exploratory drifts andshafts should be determined by data uses. Directintegra-tion of excavation maps into composite maps ofa dam foundation is much easier if undistorted sectionsare available. The maps can be treated in the samemanner as drill hole logs. The disadvantages of plan andsection mapping may be offset by the advantages of easyinter-pretation and integration into other data bases.

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Construction Mapping.—Full periphery geologicmapping should be used for routine constructionactivities. The advantages of increased speed andaccuracy in production mapping and the reduction ofinterpretation offsets the disadvantages.

Summary

This guide to tunnel geologic mapping during construc-tion has been developed for general use and serves tostandardize procedures and data collection. Items ofprimary significance are included, but some are notadaptable to all tunnels or methods of tunnel excavation.The judgment of an experienced geologist is the bestguide to the specific items and amount of detail requiredto provide pertinent, informative data. To ensurereliable and useful tunnel geologic studies, all importantgeology and related engineering construction data whichmay be significant to tunnel construction as well asin the planning, designing, and constructing of futuretunnels should be considered for inclusion in the tunnelmap and report.

Photogeologic Mapping

General

Aerial photographs generally are used in reconnaissancegeologic mapping, geologic field mapping, and in gener-ation of photo-interpretive geologic maps. Various scalesof airphotos are valuable for regional and site studies, forboth detection and mapping of a wide variety of geologicfeatures important to engineering geology.

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Types of Aerial Photographs

Panchromatic (Black and White).—Panchromaticphotography records images essentially across the entirevisible spectrum, and with proper film and filters alsocan record into the near-infrared. In aerial photography,blue is generally filtered out to reduce the effects ofatmospheric haze.

Natural Color.—Images are recorded in the naturalcolors seen by the human eye in the visible portion of thespectrum.

False-Color Infrared.—Images are recorded using partof the visible spectrum and part of the near-infrared, butthe colors in the resultant photographs are not natural(false-color). Infrared film is commonly used and is lessaffected by haze than other types. False-color photo-graphy is not the same as thermal-infrared imagingwhich uses the thermal part of the infrared spectrum.

Multispectral.—Photographs acquired by multiplecameras simultaneously recording different portions ofthe spectrum can aid interpretation.

Photogrammetry and Equipment

Use stereoscopes to view aerial photographs formaximum utility and ease of interpretation. Pocketstereoscopes are useful in the field or office. Largemirror stereoscopes are useful for viewing largequantities of photos or photos in rolls. Know the photoscale, resolution, and exaggeration. Be aware of thetypes of distortions inherent in airphotos.

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Compilation of Photogeologic Map Data

Mapping should be done on transparent one-side-mattemylar overlays and not on the photographs. Any lines,even if erased, can confuse later interpretations usingthe photos. The mapping is then transferred to basemaps minimizing the effects of distortions in photos dueto the camera optics. Orthophoto quadrangles can helpreduce this distortion.

Analysis of Aerial Photographs

General Interpretive Factors

Analysis of aerial photographs involves interpretingindirect data. In most cases, several factors are used tointerpret geologic conditions. Interpretive factorsusually used in the analysis of aerial photographs are:

Sun Angle.—High or low illumination angles may bedesired, depending on the nature of the features to bedetected.

Photographic Tone.—Variations in color, intensity,shade and shadows.

Texture.—Frequency of change in tone, evident asroughness, smoothness.

Color.—True and false-color imagery may be easier tointerpret than panchromatic photographs, depending onfeatures being observed. For some applications (e.g., low sun angle photography), panchromatic photographyis better.

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Geomorphic Shape and Pattern.—Geologic conditionscan be identified by mapping various types of geomorphicfeatures related to drainage, bedding, and structure.

Vegetation.—Some types of vegetation and vegetal pat-terns can assist in interpreting geology. Vegetation mayindicate depth of soil, type of soil, available moisture,and type of bedrock.

Photoanalysis for ReconnaissanceGeologic Mapping

Photo-reconnaissance geologic mapping can be done toproduce a preliminary geologic map of the study areaprior to going into the field to check and verify theinterpreted geologic data or to produce a finishedgeologic map with little or no field checking. These mapsare called photo-reconnaissance geologic maps andphoto-interpretive geologic maps, respectively.

Photo-Reconnaissance Geologic Mapping

Photo-analysis prior to field work allows the mapper toform a preliminary concept of the geology of the studyarea and to select areas for detailed examination. Priorphoto-analysis is critical if available field time is limited,especially when a large area is involved, as in regionalstudies, reservoir area mapping, and pipeline or canalalignment studies.

Photo-Interpretive Geologic Mapping

Geologic maps produced solely from aerial photographswith little or no field checking are useful when time,funds, or access are limited or when adverse weatherprevents a more detailed field mapping program. The

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limitations of this form of geologic map are dependent onoutcrop density and degree of exposure, amount ofvegetative cover, contrast of the geologic units, and theskills of the photogeologic mapper. This type of map isuseful for preliminary or reconnaissance levelevaluations but should never be used for design levelwork.

Photoanalysis During Geologic Field Mapping

The location and verification of geologic features in thefield can usually be expedited by using aerial photo-graphs. Photographs often reveal landforms that aredifficult to see or interpret from the ground, such asland-slides. Photographs can be used to clarify andspeed up field mapping by allowing a comprehensiveview of the study site and the relationships of thevarious geologic features exposed. Alternately viewingphotos and exam-ining outcrops can greatly facilitatemapping.

Availability of Imagery

Aerial photography is available, commonly in a variety ofscales and types, for essentially the entire conterminousUnited States. The principal repositories of publiclyowned airphotos is the EROS Data Center, operated bythe U.S. Geological Survey and the AgriculturalStabilization and Conservation Service (ASCS) of theU.S. Department of Agriculture. The USGS has severalregional offices of the Earth Science Information Center(ESIC). The ESIC operates the Aerial PhotographySummary Record System (APSRS), which is a standardreference data base for users of aerial photographs. TheAPSRS lists aerial photography available from a largenumber of government agencies and commercial com-panies. The lists are comprehensive and categorized bystate and by latitude and longitude. APSRS data are

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available on request from ESIC. ESIC also providesinformation about cartographic products other thanimagery.

Some important addresses and telephone numbers are:

USDA-ASCS (801) 524-5856Aerial Photography Field OfficeCustomer Services2222 West 2300 SouthP.O. Box 30010Salt Lake City, UT 84130-0010

USGS (605) 594-6151EROS Data CenterSioux Falls, SD 57198

USGS (303) 202-4200ESICDenver Federal CenterDenver, CO 80225

USGS (650) 329-4309ESIC345 Middlefield RoadMenlo Park, CA 94025

Aerial Photography Flight Planning

If air photos are not available at the right scale, or of theright type for an area, specific flights can be made.Successful airphoto mission planning requires considera-tion of several factors, including film type, scale, time ofday (sun-angle), time of year, and the size of the area tobe covered. Mission planning should not be done bysomeone unfamiliar with the process without assistance.Specifications should be written to ensure that theresult-ing photographs will be appropriate for the

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intended purpose. Information critical to missionplanning is available from the references listed below.

Time and Cost Estimating

The cost of data acquisition is relatively easy to estimate.The cost of interpretation is much harder to estimate,being a function of the time required, which is related tothe size and complexity of the study area and the skill ofthe interpreter. The cost of a single drill hole will payfor a lot of aerial photography and interpretation.

References

A classic text on the use of airphotos in geology wasreprinted in 1985 and should be readily available. Someof the equipment described is obsolete and it isessentially limited to discussion of panchromaticphotography. The publication contains numerousstereopairs with geologic descriptions and is one of thebest works on airphoto interpretation for geologists:

Ray, R.G., Aerial photographs in geologic interpretationand mapping, USGS Professional Paper 373, 230 p.,1960.

Other useful references are:

Lattman, L.H., and Ray, R.G., Aerial photographs infield geology, Holt, Rinehart and Winston, New York, NY221 p., 1965.

Miller, V.C., Photogeology, McGraw-Hill, New York, NY,248 p., 1961.

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A reference containing no general discussion ofprinciples, but with excellent examples of stereopairs ofgeologic features, associated topographic maps, andgeologic annotations is:

Scovel, J.L., et al., Atlas of Landforms, Wiley & Sons,New York, NY, 164 p., 1965.

A broad and lengthy reference covering remote sensingin general, including much information about aerialphotography of all types, is:

Colwell, R.N., editor, Manual of remote sensing,2nd edition, American Society of Photogrammetry, FallsChurch, VA, 272 p., 1983.

BIBLIOGRAPHY

[1] U.S. Geological Survey, Map Projections - A WorkingManual, U.S. Geological Survey ProfessionalPaper 1395, 1987.

[2 ] Jackson, Julia A., editor, The Glossary of Geology,4th edition, American Geologic Institute,Alexandria, VA, 1997.

[3] Lahee, Frederic H., Field Geology, 6th edition,McGraw-Hill, Inc., New York, NY, 1961.

[4] Compton, Robert R., Geology in the Field, JohnWiley and Sons, New York, NY, 1985.

[5] Bureau of Reclamation, Division of Safety, Safetyand Health Standards, Denver Office, Denver, CO.

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[6] Proctor, M.E., and White, T.L., Rock Tunneling withSteel Supports, Commercial Shearing, Inc., Youngs-town, OH, 1977.

[7] Hatheway, A.W., “Trench, Shaft, and Tunnel Map-ping,” Bulletin of the Association of EngineeringGeologists, v. XIX, 1982.

[8] U.S. Army Corps of Engineers, “Engineering andDesign, Geologic Mapping of Tunnels and Shafts bythe Full Periphery Method,” Engineer TechnicalLetter No. 1110-1-37, Washington, DC, 1970.

[9] Proctor, R.J., “Mapping Geological Conditions inTunnels,” Bulletin of the Association of EngineeringGeologists, v. VIII, 1971.

Chapter 7

DISCONTINUITY SURVEYS

General

Physical properties of discontinuities generally controlthe engineering characteristics of a rock mass. Accurateand thorough description of discontinuities is an integralpart of geological mapping conducted for design andconstruction of civil structures. It is improbable that anysurvey will provide complete information on all thediscontinuities at a site. However, properly conductedsurveys will furnish data with a high probability ofaccurately representing the site discontinuities. Thischapter discusses discontinuity recording methodology.These recording methods can be applied to outcrops, drillholes, open excavations, and the perimeters of under-ground openings. The evaluation of discontinuity data iswell described in the literature. For example, plottingdiscontinuity data on stereograms, contouring to deter-mine prominent orientations, and subsequent wedgeanalyses are described in Rock Slope Engineering [1] andMethods of Geological Engineering in Discontinuous Rockand Introduction to Rock Mechanics [2,3]. “Chapter 5,Terminology and Descriptions for Discontinuities,” listsdata that are typically recorded in discontinuity surveys.

It is extremely important that the actual discontinuitydescriptors and measurement units be selected to supportthe anticipated rock mass classification system(s).Acquiring incomplete or excessive data may limit datausefulness in subsequent analyses, and result inexcessive costs due to repeating surveys or from collectingmore data than needed.

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Empirical Methods for Rock Mass Classification

A number of empirical methods have been developed topredict the stability of rock slopes and undergroundopenings in rock and to determine the supportrequirements of such features. A method for estimatingsteel-arch support requirements in tunnels was one of thefirst [4], and various methods which address open-cutexcavations and existing rock slopes have been usedsince. The Geomechanical Classification (Rock MassRating [RMR]) [5,6] and the Norwegian GeotechnicalInstitute (NGI) (Q-system Classification [Q]) [7] are com-monly used. Both of these methods incorporate RockQuality Designation (RQD) [8]. Since both the RMR andQ-system are based on actual case histories, both systemscan be somewhat dynamic, and refinements based on newdata are widely suggested. Additional information onRQD, RMR, and the Q-system is provided in chapter 2.

Other predictive methods include the Rock StructureRating (RSR) [9] and the Unified Rock ClassificationSystem (URCS) [10]. “Keyblock” analysis [11,12] is ameans of determining the most critical or “key” blocks ofrock formed by an excavation in jointed, competent rock.An excellent single source of information on the variousclassification systems is in American Society for TestingMaterials Special Technical Publication 984, RockClassification Systems for Engineering Purposes.

Data Collection

Discontinuity data can be collected using areal or detailline survey methods. The areal method, which consistsof the spot recording of discontinuities in outcrops withinan area of interest, is of limited use in geotechnicalanalyses. Areal surveys should be applied only forpreliminary scoping of a site or in cases where the lateral

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extent of exposed rock is inadequate to perform detail linesurveys. The detail line survey (DLS) method (DLS orline mapping) provides spacial control necessary to accu-rately portray and analyze site discontinuities. DLS map-ping was originally a method of mapping road cuts andopen pit excavations. DLS use has been expanded both inscope and types of exposures mapped. Each geologicfeature that intercepts a usually linear traverse isrecorded. The traverse can be a 100-ft (30 m) tape placedacross an outcrop, the wall of a tunnel, a shaft wall at afixed elevation, or an oriented drill core. In all cases, thealignment of the traverse and the location of both ends ofthe traverse should be determined. The mapper movesalong the line and records everything, as noted inchapter 5, or as needed to support analyses. Featurelocations are projected along strike to the tape, and thedistance is recorded. Regardless of the survey method,the mapper must obtain a statistically significant numberof observations. A minimum of 60 discontinuity measure-ments per rock type is suggested for confidence insubsequent analyses [14].

The orientation of a discontinuity can be recorded eitheras a strike azimuth and dip magnitude, preferably usingthe right-hand rule, or as a dip azimuth and magnitude(eliminating the need for dip direction and alphacharacters required by the quadrant system). Accordingto the right-hand rule, the strike azimuth is always to theleft of the dip direction. When the thumb of the righthand is pointed in the strike direction, the fingers pointin the dip direction. The selected recording methodshould be used consistently throughout the survey.

Data acquired in a single straight-line survey areinherently biased. The more nearly the strike of a discon-tinuity parallels the path of a line survey, the lessfrequently discontinuities with that strike will be

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recorded in the survey. This is called line bias. Thenumber of intersecting discontinuities is proportional tothe sine of the angle of intersection. In order to compen-sate for line bias, a sufficient number of line surveys at asufficient variety of orientations should be conducted toensure that discontinuities of any orientation are inter-sected by at least one survey at an angle of at least30 degrees. Common practice is to perform two surveysat nearly right angles or three surveys at radial angles of120 degrees. True discontinuity (set) spacing and tracelengths can be obtained by correcting the bias producedby line surveys [15, 16].

All discontinuities should be recorded regardless ofsubtlety, continuity, or other property until determinedotherwise. Data collection should be as systematic aspracticable, and accessible or easily measurable discon-tinuities should not be preferentially measured. Con-sistency and completeness of descriptions are alsoimportant. Consistency and completeness are best main-tained if all measurements are taken by the same mapperand data are recorded on a form that prompts the mapperfor the necessary descriptors. A form minimizes theprobability of descriptor omission and facilitates plottingon an equal area projection, commonly the Schmidt net(figure 7-1), or entering data for subsequent analysis.Computer programs are available that plotdiscontinuities in a variety of projections and perform avariety of analyses. Whether the plot format is the equalarea projection (Schmidt net) or equal angle projection(Wulff net), evaluation of the plotted data requires anunderstanding of the method of data collection, form ofpresentation, and any data bias corrections. References2 and 3 in the bibliography are good sources of dataanalysis background information.

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Figure 7-1.—Equatorial equal area net (Schmidt net).

Different rock types in the same structural terrain canhave different discontinuity properties and patterns, andthe host rock for each discontinuity should be recorded.This could be an important factor for understanding sub-sequent evaluations of tunneling conditions, rock slopes,or the inplace stress field in underground openings.

Figure 7-2 is a form that can be used to record the data inan abbreviated or coded format. Recording these datawill provide the necessary information for determiningRMR and Q. These codes are derived from the descriptorsfor discontinuities presented in chapter 5.

FIE

LD

MA

NU

AL

210

Figure 7-2.—Discontinuity log field sheet.

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BIBLIOGRAPHY

[1] Hoek, E., and J. Bray, Rock Slope Engineering, revised3rd edition, The Institute of Mining, London, 1981.

[2] Goodman, R.L., Methods of Geological Engineering inDiscontinuous Rock, 1976.

[3] Goodman, R.L., Introduction to Rock Mechanics, 1980.

[4] Terzaghi, K., “Rock defects and loads on tunnel sup-port,”Rock Tunneling with Steel Supports, CommercialShearing, Inc., Youngstown, OH, 1946.

[5] Bieniawski, Z.T., Engineering Rock Mass Classifica-tions, 1989.

[6] Bieniawski, Z.T.,and C.M. Orr, “Rapid site appraisalfor dam foundations by the geomechanics classification,”Proceedings 12th Congress Large Dams, ICOLD, MexicoCity, pp. 483-501, 1976.

[7] Barton, N., F. Lien, and J. Lunde, “Engineering classi-fication of rock masses for the design of tunnel support,”Rock Mechanics, v. 6, No. 4, pp. 189-236, 1974.

[8] Deere, D.U., A.J. Hendron, F.D. Patton, and E.J. Cord-ing, “Design of surface and near surface construction inrock,” Proceedings 8th U.S. Symposium Rock Mechanics,AIME, New York, pp. 237-302, 1967.

[9] Wickham, G.E., and H.R. Tiedemann, “Ground sup-port prediction model—RSR concept,” Proceedings RapidExcavation Tunneling Conference, AIME, New York,pp. 691-707, 1974.

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[10] Williamson, D.A., “Unified rock classificationsystem,” Bulletin of the Association of EngineeringGeologists, v. XXI, No. 3, pp. 345-354, 1984.

[11] Goodman, R.E., and Gen-Hua Shi, “Geology and rockslope stability—application of a “keyblock” concept forrock slopes,” Proceedings 3rd International Conference onStability in Open Pit Mining, Vancouver, June 1981.

[12] Goodman, R.E., and Gen-Hua Shi, Block Theory andIts Application to Rock Engineering, 1985.

[13] Piteau, D., “Geological factors significant to thestability of the slopes cut in rock,” Proceedings of the OpenPit Mining Symposium, South African Institute of Miningand Metallurgy, September 1970.

[14] Savely, J., “Orientation and Engineering Propertiesof Joints in Sierrita Pit, Arizona,” MS thesis, Universityof Arizona, 1972.

[15] Priest, S.D., and J.A. Hudson., “Estimation of discon-tinuity spacing and trace length using scanline surveys,”International Journal of Rock Mechanics-Mining Sciencesand Geomechanics Abstracts, v. 18, No. 3, pp. 183-197,1981.

[16] Terzaghi, R.D., “Sources of error in joint surveys,”Geotechnique, v. 15, No. 3, pp. 287-304, 1965.

Chapter 8

EXPLORATION DRILLING PROGRAMS

Introduction

This chapter is a guide for developing effective andefficient exploration drilling programs. Drillingprograms that involve extensive soil sampling, rockcoring, instrumentation installations, or in-place testingcommonly have excessive cost overruns and latecompletion times. The effort put into developing a wellorganized drilling program that explicitly defines drillingand sampling requirements can lower exploration costssignificantly by eliminating unnecessary or redundantwork and meeting schedules. Good references on drillingmethods and equipment are Groundwater and Wells,second edition, by Fletcher G. Driscoll, published byJohnson Division, St. Paul, Minnesota 55112, andDrilling: The Manual of Methods, Applications, andManagement, CRC Lewis Publishers, Boca Raton,Florida, 1996.

Planning the Exploration Drilling Program

Developing an exploration program requires a thoroughknowledge of the design requirements, site conditions,drilling equipment requirements and capabilities, andsoil or rock core testing. It is extremely important thatexploration needs be identified to avoid overdesign of aprogram by too many “it would be nice” requests.

A complete and detailed description of the drill sitelocation, accessibility, work requirements, geology, andother pertinent information should be made available toeither the drilling contractor or in-house drilling staff.This information is necessary for an effective andefficient drilling operation that will accomplish theprogram objectives. A major objective is to obtain themost information and samples possible from each hole by

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optimizing location, drilling and sampling methods,depth, and completion. For example, a drill hole on theintersection of dam and outlet works centerlines drilledto the depth of the deepest data requirement andsampled for both structures provides data for bothstructures.

Most exploration is done in phases, with subsequentexploration designed to refine the understanding of asite. Drill holes should be logged as the holes are drilled,so hole depths and subsequent hole locations can bechanged as exploration progresses. Because anexploration program evolves as data are acquired,information should be reviewed and added to maps andsections as the data become available.

Site Inspection

An onsite inspection of the drilling location should bemade by the geologist, designers, and other essentialmembers of the exploration team. The purpose of theonsite inspection is to determine the exploration neededto provide the data required for design. Data arerequired for several design disciplines with differentneeds. Having knowledgeable representatives see thesite is important when formulating an explorationprogram. Changes and additions to explorationprograms during or after exploration are expected butcan be minimized with careful planning.

During the site inspection, the geologist and designersshould discuss in detail all the design concerns that canonly be solved by analyzing the subsurface geology. Theteam should be explicit as to the size, quantity, type, andquality of soil or rock samples that are necessary todevelop an accurate evaluation of geologic conditions.The geologist can recommend the type of equipment and

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drilling procedures needed, based on the drilling andsampling requirements, and to address design concernsas well as to provide samples needed for laboratorytesting.

The onsite inspection should provide other pertinentinformation which is critical to the selection of specificequipment. The following factors should be addressedwhen preparing the exploration plan.

Topography-drill site accessibility.—The type ofdrilling equipment most suitable for the work needs tobe determined. Truck-mounted, all-terrain, skid-mounted, or a combination of several types may beappropriate. Heavy excavation and hauling equipmentmay be required to construct access roads, drill pads,stream crossings, temporary bridges, or pipe culverts forriver crossings. Explosives and track drills may berequired to prepare drill pads or remove unsafe rockoverhangs from drill sites, and roadbase or rockfill mayhave to be to be placed over soft mud or swamp.Helicopter support may be needed for fly-in rigs andheavy timber clearing. A source of water for drillingneeds to be identified. Other considerations are whetherthere is a relatively close and level area that may beused as a temporary drill yard/staging area and howclose equipment can be safely driven into the drill area.

Right-of-way, access permits, drilling permits,construction or clearing permits.—The drillinglocations, whether on public or private land, may requireaccess permits. Several different types of permits maybe needed, including archeological and environmentalpermits. These permits may take considerable time toobtain and should be acquired as soon as possible. Thelimitations of the permits should be determined.Construction or clearing permits may be needed. Most

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states require special licenses or permits for drill op-erators who perform water-well drilling and installation.

Protection of the Environment

Environmental, archeological, and biological factors mayplace restrictions or conditions on a site. Disposal of thecleared material should be arranged. The use of drillingmud requires planning and implementation prior todrilling. If the drill mud circulation pits can beexcavated, the mud pits may have to be enclosed withfencing to keep out animals. Drill mud and cuttings aswell as fuel and oil spills or oil change residue willrequire disposal. Some drill mud, cuttings, and watershould be stored because the material is considered ahazardous waste. These materials may have to bedisposed of at approved sites. Crossing shallow streamscan create contamination or turbidity problems. Drillhole completion and site restoration should beformulated. Dust abatement may be necessary for travelover the access roads. Routes through planted fieldsshould be arranged before travel.

Drilling

Many factors should be considered during thedevelopment of the exploration plan as listed below:

• Are the drill sites on rock

• Can downhole hammers be used to set collarcasing

• Are surficial materials suitable for hollow-stemauger use

• If the drill hole is to be water-pressure tested,may drilling mud or air foam be used

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• Are soil samples required

• Can casing or hollow-stem augers be advancedthrough the surficial deposits so that rock coringcan be performed

• Can the drill hole be used to combine geophysicaland in-place testing

• Will geophysical testing be required in the drillhole

• Are angle holes required

• Will the holes require directional drilling controland then be verified by survey

• Will polyvinyl chloride (PVC) casing have to beinstalled for survey confirmation

• Will water pressure tests or permeability tests berequired as the hole is drilled or can the testing beperformed after the hole is completed

• Will the permeability tests require packers andpressure testing or gravity head pressure

• Will the holes require instrumentation installation

• What are the requirements for the backfill in theinstrumentation drill hole and how is it to beplaced

• Will the outside annulus of the casing requiregrouting

• What are the hole completion requirements

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Equipment

• Are the requirements for soil sample and/or rockcore sizes compatible with existing commerciallyavailable equipment

• Will the samples or cores have to be transmittedto the testing laboratories in sealed liners, splittube liners, thin-wall steel tubes, or cheeseclothand wax seals in core boxes

• Are there special concerns for the samples andtheir delivery

• Will those concerns require them to betransported in vibration-free containers

• Should the samples be protected from freezing

• Should the samples be weighed in the field andthe density and moisture content determinedbefore delivery to the laboratories

• What is the minimum drill equipment that shouldbe specified considering the total hole depth, sizeof core or soil sample requirements, boreholediameter, and rod size

• What is the minimum mud pump or aircompressor rating that should be specified

• Where is the water source; will water have to behauled or can it be pumped to the drill site

• How much water line will have to be laid

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Traffic Control and Safety

• Will the drill locations require traffic control,detours, barricades, flag personnel, etc., for safetyand public protection

• Will road or highway travel require reroutingduring the drilling program

• Has permission been obtained from local, county,or state officials to close roads

• Will drilling be performed in high visibility areas

• Will equipment security and vandalism be enoughof a problem to warrant nighttime securitypersonnel or fencing

Special Considerations

• Will the drilling require excavating orconstructing ramps and drill pads on the slopeface of an earth embankment

• Will the embankment slope face drilling have tobe done with skid-rigs on timber cribbingplatforms or with specialized drills that arecapable of traversing and drilling intoembankment slope faces without excavatingramps or benches

• Will underground drilling be required

• Establish and include all underground safetyrequirements in the drilling specifications

• Size the underground drilling equipment so it willbe suitable for the height and width of the tunnelor drift

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• Is there potential for large water inflows

• Is there potential to intercept reservoir waterduring underground drilling operations

• Will the drilling program require drill setups onscaffolds or hanging platforms

• Are qualified personnel available to review thedesign of any scaffold or hanging platform drillsetup, and will they have the authority to acceptor reject the construction

• Will the drilling program require operation froma floating plant (barge) or a jack-up platform

• Obtain data for fluctuating river rises or falls,flow rate, and depth of water under normal flowconditions

• Will drilling be required in the vicinity of overheadtransmission lines, transformer boxes, or under-ground buried utilities

• Have all underground utilities been located andflagged

• Will the program require helicopter service for fly-in rigs

• Have fly-in hazards been identified prior to start,such as transmission lines, heavy timber,turbulent winds, and rough terrain

• Are artesian pressures anticipated

• Are circulation loss zones anticipated

• Have contingency plans been prepared to seal andcontain artesian water flow or large volume waterflow that may be encountered during any drillingoperations

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• Has it been determined how the drill holes are tobe completed, i.e., capped and locked collar casing,collar casing guard fixtures, or install piezometersor other monitoring instrumentation, or backfilledand grouted

Drilling in Dam Embankments

The Bureau of Reclamation's (Reclamation) embankmentdesign practice minimizes development of stress patternswithin an embankment. Stress patterns could lead tohydraulic fracturing by drill fluids during drilling.Certain embankment locations and conditions have ahigher potential for hydraulic fracturing than others, andimproper drilling procedures or methods will increasethe potential for hydraulic fracturing. Site locations andconditions where hydraulic fracturing by drilling mediaare more likely to occur and adversely affect a structure'sperformance include the following:

1. In impervious cores with slopes steeper than0.5H:1V, cut-off trenches, and upstream-inclinedcores.

2. Near abutments steeper than 0.5H:1V, whereabrupt changes in slopes occur, and above boundariesin the foundation which sharply separate areas ofcontrasting compressibility.

3. Near structures within embankments.

4. In impervious zones consisting of silt or mixturesof fine sand and silt.

Recommended procedures for developing exploration andinstrumentation programs and for drilling in theimpervious portion of embankment dams are as follows:

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1. The embankment design should indicate whethera hydraulic fracturing potential exists.

2. If a high potential for hydrofracturing exists, thetype of equipment and the method and technique tobe used for drilling must have the approval of theexploration team. Once drilling has commenced,drilling personnel are responsible for controlling andmonitoring drill media pressure, drill mediacirculation loss, and penetration rate to assure thatthe drilling operation minimizes the possibility forhydraulic fracturing.

3. If a sudden loss of drill fluid occurs during anyembankment drilling within the dam core, drillingshould be stopped immediately. Action should betaken to stop the loss of drill fluid. The reason forloss should be determined, and if hydraulic fracturingmay have been the reason for the fluid loss, thegeologist and designer should be notified.

With the exception of augering, any drilling method hasthe potential to hydraulically fracture an embankmentif care is not taken and attention is not paid to detail.Augering is the preferred method of drilling in the coreof embankment dams. Augering does not pressurize theembankment, and no potential for hydrofracturingexists. Use of a hollow-stem auger permits sampling inthe embankment and allows sampling/testing of thefounda-tion through the auger’s hollow stem, which actsas casing.

Drilling methods which may be approved for drilling inembankment dams if augering is not practical (i.e.,cobbly fill) are as follows:

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1. Cable tool

2. Direct rotary with mud (bentonite orbiodegradable)

3. Direct rotary with water

4. Direct rotary with air-foam

5. Down-hole hammer with reverse circulation

Selection of any one of the above methods should bebased on site-specific conditions, hole utilization,economic considerations, and availability of equipmentand trained personnel.

Any drilling into the impervious core of an embankmentdam should be performed by experienced drill crews thatemploy methods and procedures that minimize thepotential for hydraulic fracturing. It is essential thatdrillers be well trained and aware of the causes of andthe problems resulting from hydraulic fracturing.

Safety

Drilling safety requirements and safety requirements ingeneral are available in Reclamation Safety and HealthStandards, Bureau of Reclamation, United StatesDepartment of Interior, 1993.

Preparation of Drilling Specificationsand Format

The work requirements should be compiled in a clearand concise manner for use by the personnel who will

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perform and inspect the work. The following is asuggested specifications format for drilling contracts.

a. General Description of Exploration Program

(1) Available Geologic Data

(2) Identification of Design Concerns

(3) Generalized Exploration Drilling, Coring,Testing, Instrumentation Requirements

b. Location of Work

(1) Area Identification

(2) Nearest Community

(3) Emergency Facilities

(4) Nearest Living Quarters/Crew Camp Area

(5) Freight Facilities

(6) Fuel and Supply Business Locations

(7) Travel Routes/Road Restrictions

(8) Public/Private Land Access Routes/Restrictions

(9) Right-of-Way Permits

c. Site Location

(1) Hole Locations

(2) Topography/Accessibility

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(3) Protection of the Environment

(4) Water Source

(5) Waste Disposal Area/Acceptable Waste DisposalMethod

(6) Drill Yard Storage Area—Restrictions

d. Work Requirements

(1) Site Preparation

(2) Collaring Holes—Boring Size—Angle

(3) Casing Requirements

(4) Sample Requirements (Disturbed/Undisturbed)

(5) Sample Sizes and Intervals

(6) Care and Transportation of Samples

(7) Core Sizes and Intervals

(8) Care and Preservation of Rock Core

(9) In-Place Testing Requirements

(10) Instrumentation Requirements

(11) Hole Backfill and Completion

(12) Site Cleanup

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e. Equipment Requirements

(1) Drill Rig Capabilities

(2) Pump/Air Compressor Capabilities

(3) Drilling Media

(4) Sampling/Coring Equipment

(5) In Situ Testing Equipment

(6) Instrumentation Equipment

(7) Core Boxes/Sample Containers

f. Special Drilling Concerns

g. Potential for Program Change, Modification,or Extension

h. Safety Program/Safety Requirements/SafetyContingency Plans

i. Exploration Drilling Reports and Logs

j. Labor Checks/Equipment Checks/CostAccounting

Chapter 9

GROUNDWATER DATA ACQUISITION METHODS

Introduction

This chapter provides information that will help select,install, and operate appropriate groundwater instrumen-tation and to collect, establish, maintain, and present thegroundwater data. Most types of engineering geologyinvestigations require acquisition and use ofgroundwater data. The data required may vary fromsimple monthly verification of the water level elevationsalong a canal-axis profile to hourly monitoring ofpiezometric conditions in multiple zones within alandslide or embankment. Successful implementation ofa groundwater instrumen-tation program depends onknowledge of subsurface conditions, preliminaryidentification of all probable future uses of the data, andcareful planning of an instrumentation system and dataacquisition program to meet these data requirements.This chapter will provide the user with:

• A detailed description of methods employed indesigning and installing groundwater monitoringsystems.

• A detailed description of available manual andautomated methods and techniques used inmonitoring ground and surface water.

• A discussion of data base management and datapresentation.

• A listing of more detailed and specific sourcematerial on groundwater data acquisition methods.

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General

The importance of fully evaluating and understandinggeologic factors controlling groundwater flow—includingporosity, storativity, permeability, transmissivity, velo-city, recharge, and discharge—cannot beoveremphasized. This evaluation needs to be made at theonset of the exploration program and continuallyrepeated throughout the investigations. These factorswill ultimately control the type of groundwateracquisition methods required.

Geologic Controls on Groundwater

Geologic controls on groundwater flow impact the designof observation systems and must be identified in thepreliminary planning of the instrumentation program.For example:

1. Permeable materials, such as clastic sediments,karstic limestone, and fractured rock, control thetype and size of well point, well screen, orpiezometer to be used and must be accounted for indesigning instrumentation for the program.

2. Relatively impermeable materials, such as clays,silts, shales, siltstones, and massive rock presentspecial problems which must be accounted for inselecting the type and size of piezometer to beinstalled. Generally these materials require use ofthe smallest size piezometer practical becausechanges in water level and volume in the hole aresmall and require long periods of time to react. Porepressure measurements in this type of geologicenvironment should be considered, particularly ifshort-term periodic—daily or weekly—changes ingroundwater conditions are needed.

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3. Layering, attitude of layers, boundaries, weath-ering and alteration, and environment of depositionall influence selection of instrumentation.

Design and Installation of ObservationWells and Piezometers

Analysis of the Geologic Environment

The presence of variations in the geologic environmentmust be anticipated. Perched water tables, artesianaquifers, sources of recharge and discharge, knownboundaries and barriers, and structural controls such asfractures, joints, faults, shears, slides, folds, and strati-graphic contacts should be considered when selectinginstrument types and sizes. The preliminary instrumen-tation design should be advanced enough to allowprocurement of needed equipment, but flexible enough toadapt to changes in the environment.

Different types of groundwater observation instrumentsprovide different data types. Observation wells andpiezometers are selected in accordance with the datarequired and the aquifer material and type. To beuseful, reliable, and accurate, the well or piezometerdesign must be tailored to the subsurface conditions.Single or unconfined aquifer zones can be monitored byusing a screened or perforated standpipe or porous tubepiezometer, or by a pore-pressure transducer. Multiplezones may be monitored using multiple drill holes,multiple piezometers in a single drill hole, or multiplepiezometer ports in a single standpipe.

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Design

The most important aspect in the design of agroundwater monitoring well is the purpose and use ofthe well; whether for taking water samples, measuringwater levels, geophysical investigations, or a combinationof uses.

The hydrogeologic environment and the type of down-hole instruments that may be used in the well willinfluence the choice of well diameter, casing type, screento be used, and the interval to be monitored.

Components of a typical well include a screened intervalsurrounded by filter/gravel-pack material isolated by abentonite and/or cement grout seal, blank casing to thesurface, and a protective well cover.

PVC is the most widely used material for standpipes(casing and screens) in monitoring wells. It is relativelyinexpensive and presents few chemical interferences inwater quality sampling. Many other materials areavailable for specific uses, including galvanized andstainless steel, Teflon©, and other plastics.

The diameter of the well depends on the instrumentationto be installed and the intended use. If the well is to besampled, by either pump or bailer, a 3-inch (75-mm)diameter hole is the preferred size for accuracy and forcomplete development of the hole, but smaller sizes canbe used with small bailers and peristaltic pumps. Wellsused for measuring water levels only may be smallerdiameter or may have multiple small diameterstandpipes within a 4-inch (100-mm) to 8-inch (200-mm)diameter hole. A standpipe designed to accommodate anM-scope water level sensor can be ¾ inch (19 mm)diameter. However, if the standpipe is to be

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instrumented with a pneumatic or vibrating wirepiezometer or if a recorder and electric probe will be usedto monitor the water level, then the diameter of thestandpipe depends on the size of the instrument ortransducer to be installed. Lengths of well screen andcasing (PVC perforated and solid standpipe) must haveuniform inner and outer casing diameters. Inconsistentinner diameters cause problems when instruments withtight clearance are lowered into the well. The pipe mayneed to be reamed to remove the beads and burrs. Afilter pack is generally composed of washed sand andgravel and is placed within the screened interval. Theinterval may extend above the screen depending on thezone thickness. The pack is designed primarily to allowwater to enter the standpipe while preventing themovement of fines into the pipe through the slots, and toallow water to leave the standpipe when water levelsdrop. If the well is to be used for sampling, the packmaterial should be sterilized to prevent possiblecontamination before placement into the well. Thegravel pack should be tremied through a pipe to preventbridging. The top of the pack may be checked using asmall diameter tamping tool, or a properly weighted sur-veyor’s tape.

A seal is installed to create an impermeable boundarybetween the standpipe and the casing or drill hole wall.The seal should be placed in a zone of low permeability,such as a clay bed above the zone to be monitored. Thisensures that water will not travel vertically along thecasing or drill hole.

Cement grout can shrink due to temperature changesduring curing and may crack. This causes a poor bondbetween the grout and the standpipe. A 1-foot (0.3-m)bentonite seal should be placed preferably as pellets orby tremieing a bentonite slurry immediately below and

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above the cement grout seal. This helps ensure areliable plug. Any seal material (optional with bentonitepellets) should be tremied into place. This preventsbridging or caking along the hole wall. The seal must bereliable so that the screened interval monitors only thedesired groundwater zone.

A drill hole containing multiple standpipes, each mon-itoring a zone or distinct water bearing strata, may haveseveral isolating seals. To test the integrity of the seals,a gravity head test may be performed by adding water tothe shallowest standpipe and continuously measuringthe water level in the next lower piezometer to detectany leakage through or around the seals. If the waterleaks into the lower interval, the piezometric head willrise in the lower standpipe.

A protective cover helps prevent damage to the standpipeand reduces surface water drainage into the backfilledhole. The casing should extend 5 to 10 feet (1.5 to 3 m)below ground and be grouted into place. Uponcompletion of the monitoring well, standpipe should bebailed or blown dry and the water level allowed torecover to a static level. A completion log should beprepared using the drillers' records, geologic log, andmeasurements. The log should include the actual depthsand thicknesses of each component of the well; thestandpipe's total depth; the screened interval, theisolated interval; the type of filter pack; the depth,thickness, and type of isolating seals; and a referencepoint from which all measurements were taken, such astop of casing or ground surface. Many excellentreferences are available to design and installgroundwater monitoring wells for various purposes.Refer to these at the end of this chapter for moredetailed instructions.

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Construction Materials

Construction materials for observation wells andpiezometers are dictated by the projected use of theinstrument and the permeability of the aquifer. Thediameter of the standpipe, the type of standpipe used(metal versus plastic), screen slot size/porous tube type,and gravel pack material are all variables dictated byaquifer characteristics.

In a relatively permeable material, the diameter of astandpipe is not critical; sand or gravel pack around thewell tip may not be required, but the screen slot size maybe critical to the success of the installation. Too smallscreen or slot size may restrict instrument reaction tochanges in water levels.

In a relatively impermeable material, pipe diameter maybe critical, a pack material of select sand or fabric wrapusually is required, and a well point or screen assemblyusually is needed, (0.010-0.020-inch [0.0250.05centimeter (cm)] slot size). Generally, the smallestdiameter pipe practical should be used in this sort ofmonitoring application, keeping in mind that thestandpipe diameter must be large enough to install ameans of measuring water levels. If the volume of thehole is too large, too much water must move in and outof the hole to accurately reflect the water level. If rapidreaction to water level or changes is needed, a pressuretransducer may be more appropriate than an open-tubepiezometer or standpipe.

A variety of materials can be used as the standpipe.Polyvinyl chloride (PVC) plastic pipe is economical andeasy to install. Plastic pipe is fairly fragile, deformable,and can be destroyed accidentally during installation.Metal pipe is more durable for installation but generally

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costs more than plastic, rusts or corrodes, and is subjectto iron bacterial action. Generally, if grout plugs areused to isolate zones, black pipe is preferred because thezinc in galvanized pipe can react with the plug anddestroy the seal. The inside diameter (I.D.) of the pipedepends on the permeability of the aquifer material andcan vary from as small as ½ inch (13 millimeters [mm])to 2 inches (50 mm) or larger. The diameter of the riseris critical to instrumentation of the observation well orpiezometer. Generally, ¾-inch (19 mm) pipe is thesmallest practical size that can be used in automatedapplications. Reaming of the pipe prior to installation toremove burrs, weld seams, and blebs of galvanizingmaterial is a necessary precaution to ensure that thestandpipe will be usable if the pipe I.D. and measuringdevice outside diameter (O.D.) are close.

The screen assembly selected for an observation well orpiezometer can be a well point, well screen, porous tube,or perforated pipe (commercially manufactured or fieldfabricated). Screen should be PVC or corrosion-resistantmetal. Slot-size is determined by filter material size andaquifer material.

The gravel-pack material selected is determined by theparticle sizes of the aquifer material and the size of thewell screen. Concrete sand or reasonably well-gradedsand to pea gravel can be used.

Plug material used to isolate the interval to be monitoredcan be tremied cement grout, bentonite pellets, or a com-bination of the two. A bentonite slurry also may be usedin some instances but must be tremied in place.Bentonite pellets are preferred if only one isolationmethod is used.

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Methods Used to MeasureGroundwater Levels

General

Groundwater measurements (and any instrumentationreadings) should be interpreted concurrently with read-ing. Erroneous readings and faulty equipment need tobe detected as encountered, and timely interpretation isa reliable method of bad reading detection. Theperson(s) taking the readings must understand theequipment and gather reliable data from theinstruments. If bad read-ings or faulty equipment arenot detected by concurrent interpretation, months ofirretrievable data can be lost, and erroneousinterpretations or data impossible to inter-pret canresult.

Manual Methods Used to Measure GroundwaterLevels

Chalk and Surveyors' Chain.—Probably the oldestand one of the most reliable methods for measuring wellsis the surveyors' chain and chalk method. This methodis not recommended where water level depths exceedseveral hundred feet (300 m+).

A lead weight may (but not necessary) be attached to asteel measuring tape (surveyors' chain). The lower 5 feet(1.5 m) of the tape is wiped dry and covered with solidcarpenter's chalk if the water level is roughly known.The tape is lowered into the well, and one of the footmarks is held exactly at the top of the casing. The tapeis pulled up. The line can be read to a hundredth of afoot (0.003 m) on the chalked section. This reading issub-tracted from the mark held at the measuring point,and the difference is the depth to water.

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The disadvantage to this method is that the approximatewater depth must be known so that a portion of thechalked section will be submerged to produce a wettedline. Deep holes require a long surveyor’s chain whichcan be difficult to handle.M-Scope (Electric Sounder).—An M-scope is anelectric sounder or electrical depth gauge consisting of anelectrode suspended by a pair of insulated wires and amilliammeter that indicates a closed circuit and flow ofcurrent when the electrode touches the water surface.Usually, AA flashlight batteries supply the current. Theinsulated wire usually is marked off in 1-foot to 5-foot(0.3- to 1.5-m) intervals. The best devices have themeasuring marks embedded directly into the line.Markers that are attached to the line slip, making itnecessary to calibrate the instrument frequently.

With the reel and indicator wire in one hand and theother hand palm up with the index finger over the casingor piezometer pipe, the wire is lowered slowly over thefinger into the piezometer pipe or well casing. By slidingthe wire over the finger, the wire is not cut or damagedby the sharp casing or piezometer pipe. Several readingscan be taken to eliminate any errors from kinks or bendsin the wire. The water level depth can be measured fromthe top of casing using the mark-tags on the insulatedwire and a tape measure marked in tenths and hun-dredths of a foot. The advantage of this method is thatwater level depths in holes several hundred feet deep canbe measured fairly quickly and accurately. The disad-vantage to this method is that malfunctioning ormechanical problems develop in the instrument givinger-roneous water level readings. Before going into thefield, the instrument must be checked for low batteries,tears, scrapes on the insulated wires, and iron-calciumbuildup on the part of the electrode touching the watersurface.

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Airline and Gauge.—This method uses a smalldiameter pipe or tube inserted into the top of the wellcasing down to several feet below the lowest anticipatedwater level. The exact length of airline is measured asthe line is placed in the well. The airline must be airtight and should be checked. The airline must hangvertically and be free from twists and spirals inside thecasing. Quarter-inch (6.3 mm) copper or brass tubingcan be used. The upper end of the airline is fitted withsuitable connections and a Schraeder valve so that anordinary tire pump can be used to pump air into thetube. A tee is placed in the line so that air pressure canbe measured on a pressure gauge.

This device works on the principle that the air pressurerequired to push all the water out of the submergedportion of the tube equals the water pressure of a columnof water of that height. A reference point (e.g., top ofcasing or pipe) and the depth to the lower end of theairline must be known. Air is pumped into the airlineuntil the pressure on the gauge increases to a maximumpoint where all the water has been forced out of theairline. At this point, the air pressure in the tube justbalances the water pressure. The gauge reading showsthe pressure necessary to support a column of water ofa height equal to the distance from the water level in thewell to the bottom of the tube.

If the gauge reads the direct head of water, thesubmerged length of airline is read directly. The totallength of airline to the reference point, minus thesubmerged length gives the depth to water below themeasuring point. If the gauge reads in pounds persquare inch, multiply the reading by 2.31 to convert tofeet of water. An accurate, calibrated gauge and astraight, air-tight airline are important.

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Popper.—A simple and reliable method of measuringwater levels is with a popper. A tape with a popperattached to the bottom is lowered into the well or casinguntil the water is reached, as indicated by a pop. Thepopper is raised above and lowered to the water surfaceseveral times to accurately determine the distance. Apopper consists of a small cylinder closed at the top andopen at the bottom. The open bottom causes a poppingsound when the water surface is hit. A 1-inch (in) or1½-in (25- or 40-mm) pipe nipple 2 to 3 in (50 to 75 mm)long with a cap on top works satisfactorily.

Pressure Gauge for Monitoring Artesian Wells.—Additional standpipe or casing can theoretically be ex-tended to eventually equal the head of the water. Asimple method to determine the artesian head is toattach a pressure gauge to the casing or the piezometerpipe. The gauge selected may be read directly or in feet(meters) of water. Install a tee on the standpipe or onthe casing so that a pressure gauge and valve can beattached to the tee. The valve may be used to bleed thepressure gauge to see if the gauge is working and can beused to measure the flow on the artesian well. When apressure reading is taken, a flow measurement shouldalso be taken. During the winter months, the valveshould be cracked open to allow the well to flow slightlyto prevent the riser pipe from freezing and breaking.The line to the gauge should be bled of water. If thepressure gauge used is in lbs/in2, multiply the gaugereading by 2.31 to obtain the head of water above thevalve.

Continuous Recorders

Stevens Recorder.—The Stevens Recorder (producedby Stevens Water Resources Products) provides areliable and economical way to obtain continuous water

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level data. The recorder is a float type consisting of a 3-to 6-inch (76- to 152-mm) float connected to a pulleywhich turns a calibrated gear-driven drum. A powersource, such as a spring clock or small motor, rotates thedrum at a known rate giving a constant indication ofelapsed time. Gearing between the float pulley and the chart drumprovide a changeable ratio of water movement to penmovement on the chart. A time scale is available on thechart, and continuous recordings may be maintained forup to several months. When a Stevens recorder is usedin a well, the minimum diameter of the well casing is4 inches (100 cm). An advantage of the Stevens recorderis versatility. Hydrographs can be created with scales of1:1 to 1:20. Most recorders can be set from 4 hours toseveral months. Johnson-Keck has a water level sensinginstrument that can continuously record water levels in½-inch (13-mm) pipe and larger. Transistorized circuitryis used to control a battery powered motorized reel. Thesensing float is attached to one end of the control wire,and the other end of the wire is connected to the reel.The instrument is connected to a Stevens type F orStevens type A recorder. The control wire passes aroundthe recorder pulley, and the sensing device is placed inthe casing. The sensing device seeks the water surface;and once the water surface is found, the circuitry keepsthe sensing device at the water surface.

Many float recorders can be attached to digital recordersfor continuous records. Data from this type ofinstrument can be used and easily interfaced with acomputer system.

Bristol Recorders.—Recorders for monitoring contin-uous artesian pressures are produced by Bristol Instru-ment Systems. The Bristol and Stevens recorders aresimilar in that pressure and time are recorded on a

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chart. The instrument usually contains diaphragms thatcan be adjusted to varying pressure conditions. Thespring-driven clock usually is calibrated for 30 days. TheBristol recorder is very useful for observing pressurechanges in artesian wells but is limited by freezingconditions in northern climates. A pressure gaugeinstalled in the line between the artesian water and thepressure recorder is very useful. This gauge provides agood indication of the working condition of theinstrument.

Gas Bubbler Transducer.—Pneumatic or gas bubbletransducers are manufactured by many companies. Thetransducers vary from a single readout box to a compli-cated array of instruments that will measure severalwells at once. A gas is forced through a tube at aconstant rate past a diaphragm. When the pressure ofthe gas on the diaphragm and the water pressure on theother side of the diaphragm are equal, a constantreading is obtained. This reading equals the amount ofwater over the diaphragm. This number multiplied by2.31 will give the amount of water head over theinstrument. These instruments may be used as a singleunit or connected into an electronic data acquisitionsystem.

Maintenance.—A good maintenance program is neces-sary to ensure reliable performance of mechanicallyactuated recorders. The instruments and data collectedare only as good as the preventive maintenance. Aroutine preventive maintenance program should bescheduled for all the instruments. In some cases, dailyinspection of recorders is required; however, if theinstrument is working properly, weekly inspections maybe sufficient. Preventive maintenance can often beaccomplished when the charts are changed.

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Methods and Techniques Used to EstimateFlows from Seeps, Springs, and Small Drainages

A thorough and detailed discussion of weirs, flumes,stilling wells, and other techniques is presented inReclamation’s Water Measurement Manual [1]. Smallseeps, springs, and intermittent drainages are oftenencountered in field investigations. These features canprovide key information during design and constructionand may be key indicators of structure performance orenvironmental impacts that may affect the project. Thelocation of drainage features, the rate of flow, and thetime of year of the observation are importantinformation. Flow can be estimated accurately using themethods described below:

Estimate the rate of flow in an open channel usingQ=VA, where:

Q = rate of flowV = velocityA = cross sectional area of channel

The cross-sectional area is determined by direct meas-urements where possible. Where impractical, the cross-sectional area may be estimated or scaled from a topo-graphic map.

Velocity is determined using a float, a measuring tape,and a stop watch by timing how long a floating objecttakes to travel a given distance. This provides a crudebut reasonably accurate estimate of flow. Other methodsmay include a pitot tube or flow meter.

Substitute the values obtained into the Q=VA equationto obtain the volume of flow.

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Measure flow from small springs and seeps directly bydiverting the flow, or in some manner channel the flowto a point for collection in a container, such as a bucket.Determine the rate of flow by timing how long it takes tofill the container. Select points along a drainage whereabrupt dropoffs occur and use this method. It is betterto measure, however crudely; but if not possible,estimate the flow. Many more sophisticated methodscan be used to obtain more accurate flow measurements,if necessary. Determination of the most appropriatemethod can be made if preliminary data are available.

Computer-Based Monitoring Systems

General

Water level monitoring may be automated. Monitoringlandslides can require a great number of points andfrequent readings. A variety of data types may berequired, which may include measurements of not onlywater levels and pore pressure changes, but deformationand movement as well. Systems required to collect,store, format, and present these data are availableallowing realtime analysis of a wide variety of datatypes.

Components of a Computer-Based Monitoring System

1. Many types of instruments including inclinometers,pressure transducers, strain gauges, water level gauges,and flowmeters can be used in a monitoring system.Electronic instruments are available in many sizes andshapes; preliminary selection of the instrument type

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should be made during the initial design of the system.The inside diameter of the well must be sized to acceptthe transducer.

2. Acquired data is sent from the instrument at the wellto the data logger or processor. This is done by hardwirefrom the instrument, line-of-sight radio, satellite radio,or phone lines.

Data from the monitoring points may be preprocessed inthe field prior to transmittal to the central computer. Anumber of microprocessor data scanners that collect andreduce data can be installed at various field locations.The central computer queries the field scanners to obtainperiodic updates. The remote scanners can be interro-gated as frequently as desired. This may include acontinuous data scan mode.

3. Data scanners reduce the instrument output to usabledata. Data scanners can be the end destination for moresimple systems or can be part of a more elaboratesystem. Generally, two types of signals are generated byinstruments used in geotechnical monitoring: (a) digitaland (b) analog current or voltages. Data scanners whichaccept and reduce data from both types of signals areavailable.

Many manufacturers offer complete packages of auto-mated instrumentation systems, including computerhardware and software. If the initial observation wellprogram is designed for automation, most of thesesystems will provide the high quality data required.

Special Applications

Many types of instrumentation can be used in a singledrill hole. A multiple use casing collects groundwater

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data from a large number of horizons within a singledrill hole. Casing is available specifically for pore-pressure observations, or grooved casing can be used sothat the well can be completed for both pressure andinclinometer measurements. Isolation between horizonscan be accom-plished either by installing a bentonite sealor by using a packer assembly designed as an integralpart of a monitoring system. Use of a monitoring systemgreatly reduces drilling costs, provides detailedmonitoring of critical drill holes, and provides a greaterflexibility than systems previously available. Smalldiameter drill holes can be used to obtain a large numberof isolated water level intervals and, depending on theapplication, can be very cost effective.

Data Base Management and Data Presentation

Standard forms are available to record field data,although standard data sheets often must be modifiedfor specific applications. Data sheets must includeremarks and information that include the monitoringwell num-ber, location, elevation reference points, typeand size of well, dates and times the well was read,depth to water, and the elevation of the water surface.Periodic readings of these observation wells over longperiods of time generate numerous data sheets.Computerization of the data base very rapidly canbecome a necessity if data are to be readily available andeasily analyzed.

Data entry and storage in digital format allowselectronic transfer of data and greater flexibility indeveloping, analyzing, and presenting data. Data maybe tabulated or presented as time-depth/elevation plotsand interpre-tive drawings such as contours and otherthree dimensional plots. Tremendous volumes of data

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can be reduced quickly to a usable format. Use of acommer-cially available data base allows data use andmanipu-lation without specialized software or training.

Definitions

Aquifer—A body of soil or rock that is sufficientlypermeable to conduct groundwater and to yieldeconomically significant quantities of water to wells andsprings.

• Confined aquifer—An aquifer bounded aboveby impermeable beds, or beds of distinctly lowerpermeability than that of the aquifer itself. Anaquifer containing confined groundwater.

• Unconfined aquifer—An aquifer having awater table. An aquifer containing unconfinedground-water.

Artesian—An adjective referring to groundwaterconfined under hydrostatic pressure.

Artesian aquifer—An aquifer containing water underartesian pressure.

Aquitard—A confining bed that retards but does notprevent the flow of water to or from an adjacent aquifer;a leaky confining bed. An aquitard does not readily yieldwater to wells or springs but may serve as a storage unitfor groundwater.

Aquiclude—A body of relatively impermeable rock orsoil that is capable of absorbing water slowly butfunctions as an upper or lower boundary of an aquiferand does not transmit significant groundwater.

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Water table or water level—The surface between thezone of saturation and the zone of aeration; the surfaceof a body of unconfined groundwater at which thepressure is equal to atmospheric pressure.

Zone of aeration or Vadose zone—Subsurface zonecontaining water under pressure less than atmospheric,including water held by capillarity, and containing air orgases generally under atmospheric pressure. This zoneis limited above by the land surface and below by thesurface of the zone of saturation or water table.

Saturation—The maximum possible content of water inthe pore space of rock or soil.

Zone of saturation—A subsurface zone in which all ofthe interstices are filled with groundwater underpressure greater than atmospheric. The zone is stillconsidered saturated even though the zone may containgas-filled interstices or interstices filled with fluid otherthan water. This zone is separated from the zone ofaeration by the water table.

References

American Geological Institute, Glossary of Geology,4th edition, Alexandria, VI, 1997.

Bureau of Reclamation, Embankment DamInstrumentation Manual, U.S. Department of theInterior, United States Government Printing Office,Washington, DC, 1987.

Bureau of Reclamation, Ground Water Manual,2nd edition, A Water Resources Technical Publication,

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U.S. Department of the Interior, United StatesGovernment Printing Office, Washington, DC, 1995.

Driscoll, Fletcher G., Groundwater and Wells, 2ndedition, published by Johnson Division, St. Paul, MN55112, 1987.

Leupold and Stevens Inc., Stevens Water Resources DataBook, 3rd edition, P.O. Box 688, Beaverton, OR 97005.

Morrison, Robert D., “Equipment, and Application,”Ground Water Monitoring Technology Procedures, TimcoManufacturing Inc., Prairie du Sac, WI, 1983.

BIBLIOGRAPHY

[1] Bureau of Reclamation, Water MeasurementManual, 3rd edition, A Water Resources TechnicalPublication, U.S. Department of the Interior,United States Government Printing Office,Washing-ton, DC, 1997.

Chapter 10

GUIDELINES FORCORE LOGGING

These guidelines incorporate procedures and methodsused by many field offices and are appropriate for"standard" engineering geology/geotechnical log forms,computerized log forms, and many of the modified logforms used by various Bureau of Reclamation(Reclamation) offices.

General

Introduction

This chapter describes the basic methods for engineeringgeology core logging and provides examples andinstructions pertaining to format, descriptive data, andtechniques; procedures for working with drillers to obtainthe best data; caring for recovered core; and water testingin drill holes. The chapter also provides a reference forexperienced loggers to improve their techniques and trainothers. Most of the discussions and examples shownpertain to logging rock core, but many discussions applyto soil core logging, standard penetration resistance logs,and drive tube sample logging.

Purpose, Use, and Importance of Quality CoreLogging

The ability of a foundation to accommodate structureloads depends primarily on the deformability, strength,and groundwater conditions of the foundation materials.The remediation of a hazardous waste site can beformulated only by proper characterization of the site.Clear and accurate portrayal of geologic design andevaluation data and analytical procedures is paramount.Data reported in geologic logs not only must be accurate,

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consistently recorded, and concise, but also must providequantitative and qualitative descriptions.

Logs provide fundamental data on which conclusionsregarding a site are based. Additional exploration ortesting, final design criteria, treatment design, methodsof construction, and eventually the evaluation of structureperformance may depend on core logs. A log may presentimportant data for immediate interpretations or use, ormay provide data that are used over a period of years.The log may be used to delineate existing foundationconditions, changes over time to the foundation orstructure, serve as part of contract documents, and maybe used as evidence in negotiations and/or in court toresolve contract or possible responsible party (PRP)disputes.

For engineering geology purposes, the basic objectives oflogging core are to provide a factual, accurate, and conciserecord of the important geological and physical character-istics of engineering significance. Characteristics whichinfluence deformability, strength, and water conditionsmust be recorded appropriately for future interpretationsand analyses. Reclamation has adopted recognizedindexes, nomenclature, standard descriptors anddescriptive criteria, and alphanumeric descriptors forphysical properties to ensure that these data are recordeduniformly, consistently, and accurately. Use of alpha-numeric descriptors and indexes permits analysis of databy computer. These descriptors, descriptive criteria,examples, and supporting discussions are provided inchapters 3, 4, and 5.

Exploration should be logged or, as a minimum, reviewedby an experienced engineering geologist. The loggershould be aware of the multiple uses of the log and theneeds and interests of technically diverse users. The

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experienced logger concentrates on the primary purposesof the individual drill hole as well as any subordinatepurposes, keeping in mind the interests of others withvaried geological backgrounds including geotechnicalengineers, contract drillers, construction personnel, andcontract lawyers. An experienced logger tailors the log tomeet these needs, describing some seemingly minorfeatures or conditions which have engineeringsignificance, and excluding petrologic features or geologicconditions having only minor or academic interest. Lessexperienced loggers may have a tendency to concentrateon unnecessary garnishment, use irrelevant technicalterms, or produce an enormously detailed log whichignores the engineering geology considerations andperhaps the purpose for completing the drill hole.Adequate descriptions of recovered cores and samples canbe prepared solely through visual or hand specimenexamination of the core with the aid of simple field tests.Detailed microscopic or laboratory testing to define rocktype or mineralogy generally are necessary only in specialcases.

Empirical design methods, such as the Rock Mass RatingSystem Geomechanics Classification (RMR) and Q-systemClassification (Q), are commonly used for design of under-ground structures and are coming into common use forother structures as well. If these methods are used, thenecessary data must be collected during core logging.

If hazardous waste site characterization is the primarypurpose of the drilling, the log should concentrate onproviding data for that type of investigation.

Drilling and logging are to determine the in-placecondition of the soil or rock mass. Any core condition,core loss, or damage due to the type of bit, barrel, or otherequipment used, or due to improper techniques used in

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the drilling and handling processes should be described.Such factors may have a marked effect on the amount andcondition of the core recovered, particularly in soft,friable, weathered, intensely fractured materials or zonesof shearing. Geologic logs require the adequatedescription of materials; a detailed summary of drillingequipment, methods, samplers, and significantengineering conditions; and geologic interpretations.Complete geologic logs of drill holes require adequatedescriptions of recovered surficial deposits and bedrock,a detailed summary of drilling methods and conditions,and appropriate physical characteristics and indexes toensure that adequate engineering data are available forgeologic interpretation and analysis.

Format and Required Data for theFinal Geologic Log

Organization of the Log

The log forms are divided into five basic sections: aheading block; a left-hand column for notes; a center col-umn for indexes, additional notes, water tests andgraphics; a right-hand column for classification andphysical conditions; and a comments/explanation block atthe bottom. Data required for each column are describedin the following discussion and the referenced examplelogs. Log DH-123, figure 10-1, and log B-102, figure 10-2,are the most complete and preferred examples; othervariations are presented but in some cases are notcomplete.

Heading

The heading block at the top of the form provides spacesfor supplying project identifying information, feature,

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Figure 10-1.—Drill hole log, DH-123, sheet 1 of 2.

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Figure 10-1.—Drill hole log, DH-123, sheet 2 of 2.

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Figure 10-2.—Drill hole log, B-102, for StandardPenetration Test, sheet 1 of 3.

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Figure 10-2.—Drill hole log, B-102, for StandardPenetration Test, sheet 2 of 3.

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Figure 10-2.—Drill hole log, B-102, for StandardPenetration Test, sheet 3 of 3.

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hole number, location, coordinates, elevation, bearing andplunge of hole, dates started and completed, and thename(s) of the person(s) responsible for logging and re-view. Locations should preferably be in coordinatesunless station and offset are all that is available.

Provide both coordinates and station and offset ifavailable. The dip or plunge of the hole can be the anglefrom horizontal or from vertical, but the reference pointshould be noted on the log. Spaces for depth to bedrockand water levels are also provided. All this informationis important and should not be omitted. Below theheading, the body of the log form is divided into a seriesof columns covering the various kinds of informationrequired according to the type of exploratory hole.

Data Required for the "Drilling Notes" Column

Data for the left-hand column of all drill hole logs aresimilar whether for large-diameter sampling, StandardPenetration Tests, rock core, or push-tube sampling logs.These data are field observations and informationprovided by the driller on the Daily Drill Reports.Examples are provided for some of these data headings;a suggested guideline and preferred order is presented inthe following paragraphs but may differ depending on thepurpose and type of exploration. Headers for data canindicate whether depths are in feet (ft) or meters (m),eliminating the need to repeat "ft" or "m" for each intervalentry. An example of the Drilling Notes column isprovided on figures 10-1 through 10-4.

General Information.—This includes headers and datafor the hole purpose, the setup or site conditions, drillers,and drilling and testing equipment used.

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Figure 10-3.—Drill hole log, DH-SP-2, sheet 1 of 2.

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Figure 10-3.—Drill hole log, DH-SP-2, sheet 2 of 2.

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Figure 10-4.—Drill hole log, SPT-107-2, sheet 1 of 3.

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Figure 10-4.—Drill hole log, SPT-107-2, sheet 2 of 3.

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Figure 10-4.—Drill hole log, SPT-107-2, sheet 3 of 3.

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1. Purpose of hole — Includes reason for drillingthe hole, such as foundation investigation, materialsinvestigation, instrumentation, sampling, or testing.

2. Drill site or setup — Includes general physicaldescription of the location of the drill hole.Information on unusual setups, such as adjacent toa stream, or drilled from a barge, gallery, or adit,may help understand the unusual conditions.

3. Drillers — Names of drillers may be significantfor reference or for evaluating or interpreting corelosses, drilling rates, and other drilling conditions.

4. Drilling equipment —

• Drill rig (make and model)

• Core barrel(s), tube(s), special samplers (typeand size)

• Bits (type and size)

• Drill rods (type and size)

• Collar (type)

• Water test equipment (rod or pipe size, hosesize, pump type and capacity, and relativeposition and elevation of pressure gauges ortransducers), packers (type—mechanical orpneumatic)

Example: Skid-mounted Sprague and HenwoodModel 250. NWD3 bottom discharge bit with a5-ft (1.5-m), split-tube inner barrel. 5-ft (1.5-m)NW rods. Water tested with NX pneumatic

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packer No. 12 with 1-1/4-inch (in) (32-millimeter[mm]) pipe, Bean pump with 35-gallons perminute (gal/min) (159 liters per minute)maximum volume, and 1-in (25-mm) watermeter. (Water testing equipment can be aseparate heading if desired.)

Drilling Procedures and Conditions.—These headersand data should include methods, conditions, driller'scomments, and records for water losses, caving, or casing.

1. Drilling methods — Synopsis of drilling, sam-pling, and testing procedures, including proceduresand pressures for drive or push tubes used throughthe various intervals of the hole.

2. Drilling conditions and driller's comments — Note by interval the relative penetration rate andthe action of the drill during this process (i.e., 105.6-107.9: drilled slowly, moderate blocking off, holeadvancing 15 minutes per foot [.3 meter]). Unusualdrilling conditions should be summarized. Changesin drilling conditions may indicate differences inlithology, weathering, or fracture density. Thegeologist needs to account for variations in driller'sdescriptions; each driller may describe similarconditions with different adjectives or percentageestimates. Any other comments relative to ease ordifficulty of advancing or maintaining the holeshould be noted by depth intervals. Drillers'comments need to adequately describe conditionsencountered while advancing the hole. Statementssuch as "normal drilling" or "no problemsencountered" are not useful.

Differences in drilling speeds, pressures, andpenetration rates may be related to the relative

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hardness and density of materials. Abrupt changesin drilling time may identify lithologic changes orbreaks and also may pinpoint soft or hard interbedswithin larger units. Often, these may be correlatedwith geophysical logs. If the driller provides usefuland accurate records of drilling conditions andprocedures, an accurate determination of the top andbottom of key marker horizons can be made evenwithout core.

Drilling progress should be recorded while drilling;recovery can be improved by relating recovery tooptimum pressures and speeds, as well as providingdata for interpretation. For each run, the drillershould record the time when starting to drill andwhen stopping to come out of the hole. Most of thesedrilling progress data are qualitative rather thanquantitative values. Controlling factors are not onlythe type of materials encountered but also may bemechanical or driller variables. These variables mayinclude type and condition of the bit, rotation speed,drilling fluid pressure, etc. THE PURPOSE OF THEBORING IS TO OBTAIN THE HIGHEST QUALITYCORE AND MOST COMPLETE RECOVERY ANDINFORMATION, NOT JUST FEET PER HOUR ORSHIFT.

3. Drilling fluid — Type and where used (includingdrilling fluid additives). This may be combined withor discussed under the heading, drilling methods.

4. Drilling fluid return — Include interval/percentreturn. Drilling fluid return may be combined withcolor.

5. Drill fluid color — Include interval/color.

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6. Caving conditions — Intervals of cave with ap-propriate remarks about the relative amount ofcaving are to be noted. When possible, report theactual caving interval rather than the depth of thehole.

7. Casing record — Casing depth is the depth ofcasing at the start of the drilled interval (see theexample below).

8. Advancement (push-tube or StandardPenetration Test (SPT) applications) — Includedepth/ interval sampled.

9. Cementing record — Note all intervalscemented and if intervals were cemented more thanonce. This information may be combined with thecasing record, as shown below:

Example of casing and cementing record:

Interval drilled(feet)

Size(inch)

Casing depth(feet)

0.0-2.3 6 Cs 0.0

2.3-4.5 6 Cs 2.0

4.5-9.2 6 Cs 4.0

9.2-15.3 NxCs 8.0

15.3-18.7 NxCs 15.0

18.7-33.2 Cmt 12.1-18.7 Cmt

Hole Completion and Monitoring Data.—Data shownin this section of the left-hand column include holecompletion, surveys, water levels, drilling rates or time,and reason for hole termination.

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1. Borehole survey data — Include if obtained.

Example of survey data:

Depth Bearing Plunge

597999119Average

S 72EWS 75E WS 72E WS 72E W

90E1

90E89E89E89E

1 E = degrees.

2. Water level data — Note depths and/or eleva-tions, water quantities, and pressures from artesianflows. Water levels or flows should be recordedduring hole advancement, between shifts, or at thebeginning or end of a shift, but definitely should berecorded at completion of the hole and periodicallythereafter. It may be advantageous to leave space orprovide a note to refer the user to additional readingsprovided elsewhere on the log for subsequentmeasurements. Computer generated logs allowconvenient updating of water levels long after thehole is completed.

Examples of drill hole logs illustrate optional formatand subsequent readings. Examples of how to recorddata are:

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Date1981

Hole depth(feet)

Depth to water(feet)

11-02 25.0 6.0

Bailed 100 gal:Level beforeLevel after

6.021.0

or:

DateHole depth

(feet)

Depth towater(feet)

11-03-81 25.0 15.0

11-04-81 40.0 29.0

01-05-82 95.2 7.0

01-15-82 95.2 Flowing 25 gal/min

02-03-82 95.2 Flowing 5 gal/min at 5 pounds per square inch (lb/in2)

3. Hole completion — Indicate how hole was com-pleted or backfilled; if jetting, washing, or bailingwas employed; depth of casing left in hole or thatcasing was pulled; location and type of piezometers;location, sizes, and types of slotted pipes (includingsize and spacing of slots) or piezometer risers; typeand depth of backfill or depths of concrete and/orbentonite plugs; location of isolated intervals; andelevation at top of riser(s). Hole completion can beshown graphically (see figure 10-5).

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Figure 10-5.—Drill hole log, DH-DN/P-60-1, sheet 1 of 3.

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Figure 10-5.—Drill hole log, DH-DN/P-60-1, sheet 2 of 3.

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Figure 10-5.—Drill hole log, DH-DN/P-60-1, sheet 3 of 3.

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4. Reason for hole termination — State whetherthe hole reached the planned depth or reason whythe hole was stopped short.

5. Drilling time — Total time, setup time, drillingtime, and downtime should be recorded on drillers'daily sheets and should also be recorded on the drilllog. These records are essential for determiningexploration program costs.

Center Columns of the Drill Log

Computer Logs.—Computer-generated logs offer severaloptions for the content and format of the log such aspermeability, penetration resistance, or rock propertieswhich have some differences in format. Examples of eachare shown in figures 10-2 through 10-5. Standard Geologic Log Form.—The followingdiscussion pertains to the center columns for the standardReclamation log (form 7-1337). The columns shown onall figures are self-explanatory. The columns can be mod-ified or new columns added to the existing log form forrecording appropriate indexes or special conditions.

The percolation tests (water-pressure tests) columnshould record the general information of the tests.Additional data may be recorded on "water testing" logforms or drillers' reports.

Type and size of hole, elevation, and depth columns areself-explanatory.

Core recovery should be recorded in percent of recoveryby run. Although desirable, core recovery does notnecessarily require a visual graph. Core recovery shouldbe noted carefully by the driller for each run on the daily

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drill reports; however, this column should be the recordof those measurements determined by the geologistduring logging. Measuring the core while in the splittube or sampler, if possible, will produce the mostaccurate recovery records.

A hole completion column may be added whichgraphically portrays how the hole was completed. If used,an explanation of the graphic symbols should be providedon the log form.

Rock quality designation (RQD) should be reported bycore run. RQD should be included on the log in graph ortabular form regardless of the type project. RQD is usedin almost any engineering application of the hole data.Most contractors are interested in RQD as an index ofblasting performance, rippability, and stability. RQD isdescribed and explained in chapter 5.

A lithologic log or graphic column is helpful to quicklyvisualize the geologic conditions. Appropriate symbolsmay be used for correlation of units, shear zones, waterlevels, weathering, and fracturing (see figure 10-1).

The samples and testing column should include locationsof samples obtained for testing and can later have actualsample results inserted in the column, if the column isenlarged.

Modifications to Standard Log Form.—Modificationsor adaptations of the center columns are permissible and,in some instances, encouraged. Examples are:

1. The use of a continuation sheet for longer drilllogs saves time and is easier to type. The sheets mayhave only one column to continue the right-handnarrative, or may be divided into two or more

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columns. See sheets 2 and 3 for drill hole SPT-107-2,figure 10-4, for an example; also see sheet 3 of 3 fordrill hole DH-DN/P-60-1, figure 10-5.

2. The center column may be modified to portray ad-ditional data such as hole completion, variousindexes, alphanumeric descriptors, or laboratory testdata.

Standard penetration test hole SPT-107-2,figure 10-4, is a modified penetration resistance logwhich shows laboratory test results; a percentgravel/percent sand/ percent fines column; liquidlimit/plasticity index (LL/PI) column, a field moisturecolumn, and other modifications. Drill hole DH-SP-2,figure 10-3, has columns for reporting field densitytest results, moisture, porosity, percent saturation,percent fines/percent sand, LL/PI, and laboratoryclassification.

3. Another modification, shown on DH-SP-2,figure 10-3, is a drawing showing the location of thehole in relation to the structure being explored.Diagrams or graphs, such as water levels, mayillustrate data better than a column of figures.

Required Data and Descriptions for the Right-Hand "Classification and Physical Condition"Column

General.—An accurate description of recovered core anda technically sound interpretation of nonrecovered coreare the primary reasons for core logging. The loggerneeds to remember that any interpretation, such as ashear, must be based on observed factual data. Theinterpreted reason for the core loss is given, but usually

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it is best to define the area of core loss as the intervalheading. For example:

99.4. to 101.6: No Recovery. Interpreted to be in-tensely fractured zone. Drillers reported blocking off,core probably ground up during drilling.

103.4 to 103.7: Open Joint?. Drillers reported 0.3-ftdrop of drill rods during drilling and loss of all water.Joint surfaces in core do not match.

0.7 to 11.6: Silty Sand. Poor recovery, only 6.2 ftrecovered from interval. Classification based on re-covered material and wash samples.

0.9 to 3.2: Rockbitted. No samples recovered.(Usually this would be subheaded under a previousdescription, inferring the materials are the same asthe last recovered).

Descriptions of Surficial Deposits.—Surficial depositssuch as slope wash, alluvium, colluvium, and residual soilthat are recovered from drill holes are described usingUSBR 5000 and 5005. If samples cannot be obtained,then description of the cuttings, percent return and colorof drilling fluid, drilling characteristics, and correlation tosurface exposures is employed. Always indicate what isbeing described—undisturbed samples, SPT or washsamples, cuttings, or cores. Descriptors and descriptivecriteria for the physical characteristics of soils mustconform to the established standards. Chapter 11provides guidelines for soil and surficial depositdescriptions.

Extensive surficial deposits usually are described usinggeologic and soil classifications. Where surficial depositsare very shallow and not pertinent to engineeringapplications for design or remediation or where geologic

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classification such as landslides or talus is preferable,units may be given genetic or stratigraphic terms only.For example, Quaternary basin fill, recent streamchannel deposit, Quaternary colluvium, zone 3embankment, and random fill may be describedgenerally; or these may be unit headings with groupname subheadings. The format is:

Geologic and group name. i.e., Alluvium, (sandysilt). Field classification in parentheses if classified,refer to chapters 3 and 11 for exceptions.

Classification descriptions. Additionaldescriptors (particle sizes, strength, consistency,compactness, etc., from the USBR 5000 and 5005standards descriptive criteria).

Moisture. (dry to wet).

Color.

If cores or disturbed samples are not available, describeas many of the above items as can be determined fromcuttings, drill water color, drilling characteristics,correlation to surface exposures, etc. Remember that forrockbitted, no recovery, or poor recovery intervals, aclassification and group name should be assigned as aprimary identification.

Description of Rock.—Description of rock includes arock unit name based on general lithologic characteristicsfollowed by data on structural features and physicalconditions. Bedrock or lithologic units are to be delineatedand identified, not only by general rock types but by anyspecial geological, mineralogical features withengineering significance, or those pertinent tointerpretation of the subsurface conditions.

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Any information which is characteristic of all of the rockunits encountered normally is included under the mainheading, producing more concise logs. Differences can bedescribed in various subheadings. Rock core is to bedescribed in accordance with descriptors and descriptivecriteria presented in chapters 4 and 5. A suggestedformat is:

1. Rock name — A simple descriptive name,sufficient to provide others with possible engineeringproperties of the rock type; may include geologicalage and/or stratigraphic unit name.

2. Lithology (composition/grain sizes/texture/color) — Give a brief mineralogical description.Describe grain shape and size or sizes and textureusing textural adjectives such as vesicular,porphyritic, schistose. (Do not use petrographicterms such as hypidiomorphic, subidioblastic). Otherpertinent descriptions could include porosity,absorption, physical characteristics that assist incorrelation studies, and other typical and/or unusualproperties. Provide the wet color of fresh andweathered surfaces.

Contacts should be described here also. If thecontacts are fractured, sheared, open, or have othersignificant properties, the contacts should beidentified and described under separate subheadings.

3. Bedding/foliation/flow texture — Provide adescription of thickness of bedding, banding, orfoliation including the dip or inclination of thesefeatures.

4. Weathering/alteration — Use established de-scriptors which apply to most of the core or useindividual subheadings. For alteration other than

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weathering, use appropriate descriptors. These mayor may not be separate from weathering dependingupon rock type and type of alteration. Also, includeslaking properties if the material air or water slakes.(Weathering may be used as first or second orderheadings for some logs.)

5. Hardness — Use established descriptors.

6. Discontinuities — These include shears, joints,fractures, and contacts. Discontinuities control orsignificantly influence the behavior of rock massesand must be described in detail. Detailed discussionsof indexes and of descriptive criteria, descriptors, andterminology for describing fractures and shears areprovided in chapter 5 and 7.

Fractures or joints should be categorized into sets ifpossible, based on similar orientations, and each setshould be described. When possible, each set shouldbe assigned letter and/or number designations andvariations in their physical properties noted by depthintervals. Significant individual joints also may beidentified and described. Physical measurementssuch as spacing and orientation (dip or inclinationfrom core axis), information such as composition,thickness, and hardness of fillings or coatings;character of surfaces (smooth or rough); and, whenpossible, fracture openness should be recorded. Indrill core, the average length between fractures ismeasured along the centerline of the core forreporting any of the fracture indexes. However,when a set can be distinguished (parallel orsubparallel joints), true spacing is measured normalto the fracture surfaces.

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Description of Shears and Shear Zones.—Shears andshear zones should be described in detail, including datasuch as the percentage of the various components (gouge,rock fragments, and associated features such as dikes andveins) and the relationship of these components to eachother. Gouge color, moisture, consistency andcomposition, and fragment or breccia sizes, shape, surfacefeatures, lithology, and strengths are recorded. Thedepths, dip or inclination, and true thickness, measurednormal to the shear or fault contacts, also must bedetermined, if possible, along with healing, strength, andother associated features. A thorough discussion ofshears and shear zones is contained in chapter 5.

Description of Core Loss.—The significance of core lossis often more important than recovered core. Lost coremay represent the worst conditions for design concepts, orit may be insignificant, resulting from improper drillingtechniques or equipment. Core losses, their intervals,and the interpreted reason for the loss should be recordedon the log.

Written Description Form.—The written descriptionfor physical conditions consists of main headings,indented subheadings, and text which describes theimportant features of the core. Headings and indentedsubheadings divide the core into readily distinguishableintervals which are pertinent to an engineering geologystudy. Assigned unit names should correlate with thoseunit names used for surface mapping. These headingsmay describe portions of the core or the entire core,depending on how well the headings encompass overallcharacteristics. Items characteristic of the entire core inone hole may be stated under the major heading;however, in other holes, this same information may haveto be broken out into various subheadings because it isnot applicable to the entire core. In this discussion,

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several logs are referenced as examples. These logs donot necessarily reflect the established standards, andeach may be deficient in some format or context; they areexisting logs which are included as examples of differentsituations which may be encountered. A discussion ofheadings follows:

1. Main headings — The main heading usuallydivides surficial deposits from bedrock. However,other methods are also acceptable, for example, thesummary log in figure 10-5.

2. First order heading — The first order headingsmay be based on weathering or lithology. When theinitial rock type exhibits more than one weatheringbreak or the lithologic properties are mostsignificant, lithology would be the first orderheading. Weathering may be used as first orderheadings where significant. If a weathering breakcoincides with a lithologic break, or only oneweathering break is present, they may both beincluded in the main heading. Depending onlithologies present, for example, if there is only onerock type, the first order headings may be based onfracturing. Lithology, weathering, or fracturing canalso be the subject of the first order heading. Incertain circumstances, a shear or shear zone or otherfeature could be given a first order or any lower orderheading in order to emphasize a feature’s presence orimportance. The arrangement which will result inthe simplest log is usually the best and should beused. The following examples illustrate the use offirst, second, and third order headings. Theseexamples are not intended to represent examples ofcomplete logs.

An example in which weathering is preferred as thefirst order heading is:

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0.0-5.0: SLOPE WASH (main heading).—General de-scription could include the total description of theunit.

5.0-200.0: PALEOZOIC CALAVERAS GROUP (mainheading).

5.0-100.3: Moderately Weathered (first orderheading based on weathering; descriptions ofweathering applicable to all lithologies could bepresented here).

5.0-10.9: Basalt10.9-20.1: Limestone20.1-50.3: Shale50.3-100.3: Sandstone

100.3-150.0: Slightly Weathered100.3-120.2: Sandstone120.2-150.0: Shale

150.0-200.6: Fresh Shale

An example in which lithology is preferred as thefirst-order subheading is:

0.0-5.0: SLOPE WASH (main heading).—General de-scription, could include the total description of theunit.

5.0-200.6: PALEOZOIC CALAVERAS GROUP (mainheading).—General description applicable to alllithologies.

5.0-100.3: Sandstone (first order heading based onlithology)

5.0-10.2: Intensely weathered

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10.2-40.1: Moderately weathered

40.1-80.2: Slightly weathered

80.2-100.3: Fresh

100.3-150.1: Fresh Shale (first order heading whichcombines weathering and lithology)

150.1-200.6: Fresh Diabase

3. Second order heading — The second orderheading and the associated description contain thechar-acteristics of the rock that are unique to aninterval that is not described in the main and firstorder headings. The second order heading usually isbased on weathering if the first order heading isbased on lithology. If the first order heading is basedon weathering, the second order heading would usu-ally be based on lithology. Fracture data can bedescribed here if similar throughout the interval; ifnot, divide fracture data into third order headings.

4. Third order heading — The third order headingis usually based on fracture data, subordinatefeatures, variations in lithology, etc. This includesvariations of rock quality within a certain lithologydue to shears, joints, bedding or foliation joints, orother discontinuities. Core recovery lengths are anindicator of fracturing and should be described underthis heading, as in the interval from 87.2 to 101.2 inDH-123 figure 10-1. If the fractures are mainlyprominent joint sets or other discontinuities, thespacing and orientation of individual sets, along withthe overall fracture characteristics, should be noted.

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5. Additional indentations — Additionalindentations usually are used to describe importantaddi-tional subordinate features, such as veins orveinlets, variations in lithology, shears, and zones ofnon- or poor recovery.

In summary, any information consistent throughouta higher order heading, but usually included in alower one, should be described in the higher orderheading to prevent repetition.

Data Required for the Comments/ExplanationBlock

The comments/explanation block at the bottom of the logform is used for additional information. This may includeabbreviations used, gauge height for packer tests, andnotes. The hole start and completion date should be inthe heading, as well as the date logged. Revision dates ofthe log should be noted to ensure that the most recentversion of the log can be identified. (Date logged and anysubsequent revision dates should be entered in thisblock). The computer log file name can be recorded inthis block.

Method of Reporting Orientation of PlanarDiscontinuities and Structural Features

True dips can be measured directly in vertical holes. Thedips of planar features in vertical holes are recorded as"dips 60E”or "60E dip" (see drawing 40-D-6499, figure 5-9).True dip usually is not known in angle holes; and,orientation is measured from the core axis and calledinclination, i.e., "Joints are inclined 45E from the coreaxis" (figure 5-9). If dips are known from oriented core orother surveys, dips may be recorded instead of inclination

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in angle holes. Figure 5-9 demonstrates how misinter-pretations can occur; the inclination of a joint in the corefrom a 45E inclined angle hole can be interpreted as ahorizontal joint or as a vertical joint by rotating the core.

Core Recovery and Core Losses

Descriptions of core in the Classification and PhysicalCondition column should describe the recovered core, notonly by physical measurements (maximum, minimum,and mostly range or average), but should identify andinclude the interpretation for any core losses, especiallyif the losses are thought to represent conditions differentfrom the core recovered. Designers and other users of thecompleted log can incorporate into their design all thefactual data that are seen and recorded. What is not seenor reported (core losses) is more difficult to incorporateinto the design and may well be the most significantinformation. Also, core losses and interpretations of thereasons for their loss are significant engineering datathat may correlate open joints, soft zones, or shears fromboring to boring or from surface features to thesubsurface explorations.

Core losses can result from three generalized conditions:inaccurate measurements by the drillers; poor drillingtechniques, equipment, and handling; or geologicconditions. The geologist, using the depth of hole,recovered core, observations of the core, and drillersobservations, is the individual to make interpretations ofthe core loss. All core should be measured by the logger.If using a split-tube barrel, the core should be measuredwhile in the barrel and always after core segments arefitted together (using the midpoint of core ends). Unac-countable losses should be reconciled, and the location ofthe loss determined.

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Tape checks or rod checks are the most reliable and pre-ferred methods for knowing the exact location of geologicconditions (top of each run is known with certainty) andwhere losses occur. All core runs should be measured andrecorded; gains and losses can be transferred to adjacentruns and cancel out each other during the process ofdetermining where the core loss is located. Inaccuratedrillers’ measurements, or locations where portions of thepreviously drilled interval was left in the hole (pulled off,or fell back in and redrilled), can be determined byexamining and matching the end and beginning of eachcore run to see if they fit together or show signs of beingredrilled. Gains may be attributed to pulling out thebottom of the hole, mismeasurement, recovering core leftin the hole from the previous run, or recovery ofexpansive, slaking, or stress relieving materials.

Where unaccountable losses occur, the examination ofcore to determine the reason for that loss is critical. Poordrilling methods (excessive pressure, speed, excessivewater discharge from the drill bit, not stopping when fluidreturn plugs), inaccurate measurements, or geologicconditions responsible for core losses should bedetermined. Core may have spun in the barrel afterblocking; an intensely fractured zone may have beenground up; or a shear zone, open joint(s), solution cavity,or joint fillings may have been washed away. Geologicinterpretation of the core loss is based on examiningrecovered core and the fractures present in the core. Drillwater losses and color or changes in the drillingconditions noted by the driller may suggest aninterpretation of the core loss. Where losses occur near arecovered clay "seam," clay coats fracture surfaces,slickensides and/or breccia and gouge are present, thecore loss may be interpreted as a shear or shear zone.The description should include all the factualinformation—discontinuity surface orientations,slickensides, coatings, gouge and/or fractures; and the

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interpretation that the loss occurred in a shear.Depending on the confidence in the interpretation basedon the observed conditions, the description can be givenas "shear," or "shear?," or "probable shear zone." When aportion of a shear zone has been lost during drilling, theno recovery zone should be described as part of the shearand the loss or part of the loss included in the shear'sthickness.

Samples

If the geologist selects representative or special samplesfor laboratory testing, an appropriate space should be leftin the core box to ensure that when logs are reviewed orphotographs are taken, core recovery is not misleading.Either filler blocks or a spacer which indicates the topand bottom depths of the sample and a sample numbercan be used to fill the sample space. For N-size cores, alength of 2- by 2-inch (50- by 50-mm) block or otherspacers that fill the tray work well. These blocks alsoshould be used to separate core runs. The lettering onthe blocks should be easily readable at a distance. Spraypainting the blocks white or yellow and lettering themwith black waterproof pens enhances visibility andlegibility. The sample interval, and sample number ifdesired, must be recorded in the Samples for Testingcolumn on the log. Portions of the core may be preservedas representative samples or to protect samples fromslaking or other deterioration.

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Core Photography

General Photographic Methods

Transmittal of core photographs with the final logs is rec-ommended. The photos may be included in the datapackage or as an appendix to the data report. Coresshould be photographed while fresh. Before and afterphotographs of materials that slake or stress-relieve arerecommended. The importance of photographing the corebefore it has been disturbed in transit and before itsmoisture content has changed cannot be overemphasized.If proper precautions during transport are followed, andthe core is logged in a timely manner, reasonably goodphotographs can be obtained away from the drilling site.This permits the labeling of core features, if desired.

If possible, cores should be photographed in both colorand black and white at 8- by 10-inch (200- by 250-mm)size. Black and white photographs do not degrade overtime like color photographs. Core photographs should besubmitted with the final logs in the geology data report;color photographs are best for data analysis.

Many methods are employed for photographing core.Each box of core can be photographed separately as thebox is first filled or three or more boxes can bephotographed at a time. There are advantages to bothprocedures:

• Greater detail and photographs depicting fresherconditions are the major advantages of photo-graphing each box individually.

• When photographing several boxes at a time,transitional features, changes in weathering orfracturing, or large shear zones can be seen in onephotograph.

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The best method is a combination of the two. Pictures ofindividual boxes at the drill site and later pictures of theentire hole are the best of two worlds.

Individual Box Photography

Any portion of core that is in danger of altering or disag-gregating because of slaking or "discing" due to stressrelief, expansion, or shrinkage due to changes in moistureor confinement because of down time, ends of shifts, orweekends must be boxed and photographed. Under thesecircumstances, the core should be photographed while ator near the material natural condition (even if a box isonly partially filled).

Each photograph should be taken from approximately thesame distance so that the scale of each photograph isidentical. The box should fill the frame of the camera,thereby obtaining the highest quality resolution or coredetail, and the camera should be held as close to normalto the core as possible. A tripod should be used ifpossible. Tilting the core box and, if necessary, standingin a pickup bed or other vantage point may be helpful.Most core boxes can be tilted about 70 to 80E before anycore is in danger of spilling out, so very little additionalheight is required. A simple 2- by 4-foot (0.6- by 1.2-m)wood frame may be constructed, or the core box may beleaned against a tool box, pickup tailgate, or other stableobject. A Brunton compass can be used to ensure that thebox and the camera are placed at a consistent, uniformangle. Shadows should be eliminated as much aspossible.

All core should be photographed both wet and dry. In hotor dry weather, the unphotographed boxed core should becovered by moist cloth. When ready to photograph, anydry zones should be touched up using a wet cloth or

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paintbrush. In extremely hot weather, the boxed core canbe sprayed or sprinkled with water. A water hose, gardensprayer, or spray bottle works well for this operation.Wait for the water to be absorbed so that there is noobjectionable sheen or glare-producing film of water onthe core at the instant of film exposure.

A labeled lid, letter board, or another frame which showsfeature, drill hole number, photograph, or core boxnumber, and depths of the top and bottom of the coredinterval should be included in the photograph. A scale infeet and/or tenths of a foot or meters is helpful.

Photographing Multiple Boxes

As soon as possible after the core is removed from thebarrel and boxed, the core should be photographed. Tofacilitate the photography, construct a frame capable ofsupporting three or more boxes at a time for use at thedrill yard or core storage yard. Photograph the core drythen spray with water to bring back the natural moisturecolor. The same precautions about glare referred topreviously should be followed.

A frame which shows the project, feature, hole number,box __ of __boxes, and from—to, as a minimum, should beused for the photograph. Other optional butrecommended entries may include date photographed,and a scale.

Special Circumstances

Special photography such as closeups of shear zones orother special features may be worthwhile. When thesephotographs are taken, a common object or scale shouldbe included to provide the viewer with relative or actualdimensions.

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When cores are coated with drill mud, a brush, wet rag,or pocket knife should be used to wash or scrape off themud so that materials are their natural color and featuresof the core are not obscured. This step obviously must betaken prior to logging the material.

Photograph Overlays

Acetate or mylar overlays on photographs of core can helpinterpretation of exposed features. Details shown mayinclude labels for shears, weathering, lithologies, or itemsof special interest. Other items that may be shown onoverlays are joint sets, and they may be coded by an alphaor numeric character or by colored ink.

Equipment Necessary for Preparing Field Logs

The following equipment or supplies are necessary foradequately preparing geologic logs:

Core recovery sheets and rough log forms orcomputer data sheets.—For recording core recoveryand maintaining accurate depth measurements fordetermining core loss intervals.

Drillers' reports.—Daily drill reports (figure 10-6) tocheck measurements for core recovery, identifyingchanges in condition or contacts in intervals of poorrecovery, determining reasons for core loss, andevaluating openness of fractures.

Knife.—Core hardness/strength characteristics;cleaning or scraping drill mud from core to allowlogging and measurement of core recovery.

Hammer.—Core hardness/strength characteristics.

FIE

LD

MA

NU

AL

292

Figure 10-6.—Daily drill report.

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Tape measure or folding ruler (engineering scalewith hundredths of feet or metric as appropriate).—Recovery measurements, thickness of units, shearsand fillings, and spacing of fractures.

Protractor.—Measuring orientation of contacts,bedding and foliation, and fracture orientation.

Hydrochloric acid.—Mineral or cementing agentidentification (3:1 distilled water to acid).

Hand lens.—Mineral or rock identification, minimum10X.

Marking pen.—Waterproof ink for marking core formechanical breaks, depth marks on core, samplemarking.

Paintbrush and/or scrub brush, and water.—Forcleaning core and for identifying wet color andincipient fractures.

Color identification charts (Munsel Color System orAmerican Geological Institute Rock Color Chart).

Filler block (spacer) material.—For identifying non-recovery intervals and location of samples and forrecording drill depths.

Sample preparation materials.—Wax, heater,container, brush, cheese cloth, etc.

Rock testing equipment.—Schmidt hammer, pointload apparatus, pocket penetrometer or torvane.

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Instruction to Drillers, Daily Drill Reports, andGeneral Drilling Procedures

Communication between the geologist and driller isextremely important. Establishment of lines ofcommunication, both orally and in writing, is key to asuccessful exploration program.

The role of the geologist in the drilling program is as anequal partner with the driller at the drill site.Establishment of this partnership at the beginning of thedrilling program will result in better data. Failure toestablish a good working relationship with the drill crewoften results in unanswered questions and a poor qualityend product. One way to establish good working rapportis to keep the drillers informed and to plan with them.

Drill Hole Plan

A suggested method for ensuring that a clearunderstanding of what the drilling requirements andexpectations are from the drill hole is the preparation ofa drill hole plan. The plan is prepared prior to startingthe hole and after the geologist has used availableinterpretive data and has determined whether specialtesting and procedures or deviations in standard practiceare required. This document provides the driller withinformation about safety, special site conditions, purposeof the hole, procedures to be followed, water testingrequirements, materials expected to be recovered, anyspecial sampling or geophysical testing required, and holecompletion requirements.

Guidelines for Drillers

The following guidelines provide a framework forpreparing written instructions for drill crews or for

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contract drill specifications. Also, the guidelines serve tohelp geologists correct poor drilling procedures, collectadditional data, or improve core handling and logging.

Drill Setup.—To ensure that drill holes are completed atthe desired location and along the correct bearing andplunge, the use of aiming stakes and a suitable device formeasuring angles should be provided by the geologist andused by the drill crews. Drillers should use aiming stakesset by the geologist or survey crew for the specifiedbearing of the drill hole. The rig must be anchoredproperly so that it will not shift. If stakes have beenremoved or knocked over, they should be replaced by thegeologist. Also, drillers must ensure the hole is drilled atthe designated angle. The geologist should check theplunge angle with Brunton compass, and/or the drillersshould use an appropriate measuring device.

Daily Drill Reports Preparation.—The drillers shouldprepare duplicate daily drill reports using carbon paper(additional copies of each report may be required oncontract rigs). All copies must be legible and preferablyprinted. One copy should be provided to the geologist formonitoring progress and for preparation of the geologiclog. The drill report has a space opposite each run foreach item of information required; each of these spacesneed to be filled out completely. Data should be added tothe report or recorded in a notebook after each run.Drillers should record data as it occurs. Seedrawing 40-D-6484 (figure 10-6) as an example forreporting daily drill activities. Many field offices havelocal forms on which these data can be recorded.Comments regarding specific items to be recorded on thedaily reports are contained in the following paragraphs.

1. Recording depths and core loss — Check foragreement on depths for intervals drilled by

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consecutive shifts. Depths should be recorded in feetand tenths of feet or to the nearest centimeter, asappropriate. Tape checks or rod checks may berequired at change of shift or more frequently whenrequested by the geologist. The section entitled“Core Recovery and Core Losses” containsinstructions for proper use of core measurements,filler blocks (spacers), and tape checks. The driller isresponsible for knowing the depth of the barrel andthe hole at all times. Discrepancies betweenintervals drilled and recovery need to be resolved.Only standard length drill rods should be used. Coreshould be measured while it is still in the innerbarrel and after it is placed in the core box.Record the most correct measurement of the two inthe report. In the event core is left in the hole, thenext run should be shortened accordingly; the leftamount and proper hole entry and startupprocedures should be followed to facilitate recovery.

2. Recording drilling conditions — Make suredrilling conditions, such as fast or slow, hard or soft,rough or smooth, even or erratic, moderately fast orvery slow, bit blocks off, etc., are indicated for eachrun. Record time in minutes per foot (meter) ofpenetration. Any changes in the drilling rate withina run also should be noted along with intervals ofcaving or raveling. If the bit becomes plugged orblocking off is suspected, the driller should stopdrilling and pull the core barrel. Also, when drillcirculation is lost, the driller should pull and ex-amine the core.

3. Drilling fluid return and color — The type,color, and estimated percent of drilling fluidsreturned should be recorded for each core run. Thedepth of changes in fluid loss or color is particularly

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important. If drilling mud is used, indicate numberof sacks used per shift. In case of total loss of drillingfluid, it may be necessary to pressure test theinterval.

4. Description of core — Drillers need to describethe core in general terms; i.e., moderately hard, veryhard, soft, clay seams, broken, color, etc. If familiarwith the rock types, drillers may report more thanjust general terminology.

5. Water-pressure testing — Holes in rock are typi-cally water tested in 10-foot (3-m) intervals atpressures of approximately ½ lb/in2 (3.5 kilopascals[kPa]) to 1 lb/in2 (6.90 kPa) per foot (1/3 m) of coverup to 100 lb/in2 (690 kPa). NOTE: Pressures may bemodified for each site. Factors such as density ofmaterials, "overburden pressure" or "cover," bedding,purpose of testing, distances from free faces, waterlevels, and artesian pressures all must be taken intoaccount so that pressure testing does notunintentionally hydrofracture the foundation or jackfoundation materials. Pressures should bedetermined by the geologist. If a range of pressuresis used, and disproportionately high water losses areobtained at the higher pressures, the pressuresshould be stepped down and water losses at thelower pressures recorded. Water test pressuresshould be stepped up 3 to 5 times and then steppeddown. Flow versus pressure should be plotted; andif the relationship is not linear or smoothly curved,hydrofracturing or jacking may be occurring. If thedecreasing pressure curve does not follow theincreasing pressure curve, washing, plugging, orhydrofracturing or jacking may be occurring withoutthe foundation materials returning to the prewatertest state. Intentionally increasing the pressureuntil the foundation is fractured or jacked is a good

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way to determine appro-priate grout pressures.Gravity tests, overlapping pressure tests, andvariations in the length of the interval tested may beused to ensure complete test data. For example, apacker interval of 8 feet (2.4 m) may be used if thehole is caving too badly to get 10 feet (3 m) of openhole. Also, if a packer will not seat at 10 feet (3 m)above the bottom of the hole and there is good rock at12 feet (3.66 m), a 12-foot test interval may be used.If losses are above 15 gal/min (1.146 liters persecond [L/sec]), exceed pump or system capacity, orwater is known to be bypassing the packer, reducethe length of the packer interval and retest.

Losses should be recorded in gallons and tenths ofgal/min (L/sec). The driller should record the watermeter reading at 1-minute intervals, and the testshould be run for a full 5 minutes at each pressureincrement after the flow has stabilized. The drillershould report the average flow in gal/min (L/sec) forthe 5-minute test. Each driller should keep his ownrecord of the packer data in case questions ariseconcerning the testing. A suggested form forrecording data is shown in figure 10-7.

6. Casing or cementing depths — The depth of thecasing or the cemented interval should be shown foreach core run. Do not cement any more of the holethan is necessary to repair a caving or ravelinginterval. The use of additives such as calciumchloride or aluminum powder, if permitted, willreduce the set time. These materials should beadded to the water and not to the cement.

7. Recording unusual conditions — All unusualconditions or events should be noted in the "Notes"

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299 Figure 10-7.—Water testing record.

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column of the report. This includes such items assudden changes in drilling speed, loss of circulation,drop of drill string (open joints or cavities), casingand cementing procedures, caving, squeezing, packerfailures, and gas.

8. Recording setups, drilling, and downtime —Time must be noted on reverse side of report. Type,number, and size of bit is indicated here also.

9. Recording water level measurements —Measurement should be recorded at the start of eachday shift and shown on the day shift report. Holesshould be jetted or bailed prior to completion of thehole to obtain reliable water level data. Immediatelyafter jetting or bailing, the depth to water should berecorded.

10. Care of core and core boxes — Split-tube(triple tube) core barrels should be used. If not used,the core should not be damaged when extracted fromthe core barrel. Do not beat on the barrel with ametal hammer; use a rubber mallet/hammer or apiece of wood. The best way to remove core from asolid barrel is by using a pump to pressurize theinside of the barrel and extrude the core (standback!). The mud pump will work satisfactorily forthis. Core should be extracted from the inner tubeand carefully placed into core boxes by hand. Theuse of cardboard or plastic halfrounds isrecommended (see figure 10-8. Core pieces shouldbe fitted into the core box and fragments shouldbe arranged to save space. Long pieces maybe broken for better fit in the core box, buta line should be drawn across the core to denote mechanical breaks. If 5-foot (1.5-m) core

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Figure 10-8.—Use of half-round to protect core.

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boxes are used, mechanical breaks to fit 5-foot runsin boxes are reduced. Figure 10-9 shows a typicalcore box for N-size core.

Core should be placed in the core box from left toright, with the top to the left, bottom to the right,starting at the top of the box so the core reads like abook. The ends and top of the box should be markedwith black enamel paint or indelible felt pen. Coreblocks, which mark the depths, are placed betweeneach run and the depth marked. Data on the outsideof the left end of the box should include the project,feature, drill hole number, box number, and depthinterval in the box.

Filler blocks (spacers) are necessary to properlyrecord information and minimize disturbance to thecore during handling. Blocks should be placed witha planed side marked with either black enamel paintor indelible felt-tip pen; 2- by 2-inch (50- by 50-mm)blocks work well for N-size core. All core runs mustbe separated with blocks properly labeled at the topand bottom of the run. Sample intervals should bemarked in the boxes using wooden blocks of lengthsequal to the missing core so that the sample may bereturned to the box. Gaps for core losses should notbe left in the core box. Core left in the hole andrecovered on the next run may be added to theprevious run. Filler blocks inserted whereunaccountable core losses occur should show thelength of loss in tenths of feet, as follows: LC (lostcore) 0.3 foot, or NR (no recovery) 0.3 foot. The coreloss block indicates that a certain length of core wasunaccountably lost within a run, and the blockshould be placed at the depth of the core loss. Ifthe point of core loss cannot be determined, the blockcan be placed in the core box at the bottom of

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303 Figure 10-9.—Standard N-size core

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the run, preceding the bottom of run block. Cavitiesmay be marked on the block. All spacer, sample,and core loss blocks should be nailed to the bottomor sides of the box to prevent movement of the core.

At the drill site, core boxes should be lined up,preferably on boards or planks, in order from top tobottom, with labels and up side to left, in a safe areaand kept covered with lids. While in the field, donot place boxes where sliding or caving of slopes islikely to occur and keep out of the way of vehiclesand equipment. Core boxes, especially thosecontaining soft, slaking, or intensely fractured corematerial, should be covered immediately to preventdamage by rain or drying. Tray partitions in boxesshould be nailed so that nails do not protrude frombottom of boxes.

When the core is moved, be careful to preventdisturbance, breakage, or spilling. Damage to thecore during transportation can be minimized byusing nailed-down spacers and a 3/4- to 1-inch thick(19-25-mm) foam-rubber pad placed between the topof the core and the secured core box lid.

Hole Completion.—Completion of the drill hole shouldmeet the requirements established by the explorationprogram and at the direction of the field geologist. Drillholes usually will be completed either with sufficientcasing or plastic pipe to assure that the hole will stayopen for later water level observations. In areas wherevandalism may occur or when long-term monitoring iscontemplated, a standpipe and suitable cap with lockshould be installed. Completion information should beindicated on the driller's report. The drill hole numbershould be stamped or welded into the casing. Ifgroundwater observation riser pipes have been installed,

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install a minimum 3-foot (1-m) length of surface casingwith a locking cap as a standpipe to mark the drill holeand protect the riser pipe. Grouted in place, thisstandpipe can also serve to protect the observation wellfrom infiltration by surface runoff.

Concrete Core Logging

Concrete structures are commonly cored to assess thequality of concrete or as part of foundation investigationson existing features. An early macroscopic assessmentof concrete core is warranted for the following reasons:

• Concrete physical condition may suggest changesin the drilling program or sampling techniquesthat would be difficult to modify after drilling iscomplete. A different approach in drilling orsampling techniques may be necessary todetermine the cause of distress or failure.

• Shipping, handling, and sample preparation maymodify the concrete core by inducing, modifying,or masking fractures or causing coredisintegration.

• Core could be lost or destroyed before reachingthe laboratory.

• Macroscopic examination may provide therequired information eliminating the need for apetrographic examination.

This section is based on American Society for TestingMaterials Designations (ASTM) C 823-83 and C 856-83.

Purposes of Examination.—Investigations of in-service concrete conditions are usually doneto: (a) determine the ability of the concrete to perform

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satisfactorily under anticipated conditions for futureservice; (b) identify the processes or materials causingdistress or failure; (c) discover conditions in the concretethat caused or contributed to satisfactory performance orfailure; (d) establish methods for repair or replacementwithout recurrence of the problem; (e) determineconformance to construction specification requirements;(f) evaluate the performance of the components in theconcrete; and (g) develop data for fixing financial andlegal responsibility.

In addition to the usual drill log information, thefollowing should be provided, if available:

• Reason for and objectives of the coring program.

• Location and original orientation of each core.

• Conditions of operation and service exposure.

• Age of the structure.

• Results of field tests, such as velocity andrebound or Schmidt hammer data.

Figure 10-10 is an example of a drill hole log showing thetypes of information that can be shown and a format fora log showing both rock and concrete core.

Examination.—Concrete core is commonly marked inthe field showing the top and bottom depths at theappropriate ends and at any of the following features.Below are listed the major items to examine and record:

Fractures — Cracks or fractures in core are bestseen on smooth surfaces and can be accented bywetting and partial drying of the surface. Old cracksurfaces are often different colors than freshfracture

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Figure 10-10.—Log of concrete and rock core.

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surfaces. Old fracture surfaces often have reactionproducts or alteration of the surfaces. Fracturesoften follow structural weaknesses.

Reacted particles — Rims on gravel or sand areoften caused by weathering processes unless otherfactors indicate chemical reactions with the cementpaste. Crushed aggregate with rims probably is dueto chemical reaction with the cement paste.

Reaction products — Crushed aggregate with rimsusually indicates alteration in the concrete, such asalkali-silica reaction or alkali-carbonate reaction.Rims in paste bordering coarse aggregate and lightcolored areas in the paste may be gel-soaked orhighly carbonated paste adjoining carbonateaggregate that has undergone an alkali-carbonatereaction. White areas of fairly hard, dry material orsoft, wet material that has fractured and penetratedthe concrete and aggregate or fills air voids shouldbe recorded. Alkali aggregate reaction products canbe differentiated from calcium carbonate deposits byusing hydrocloric acid. The reaction products do notfizz.

Changes in size or type of fine and coarseaggregate — Sizes, shapes, and types of aggregatecan vary in a structure due to changes in mixes,placement procedure, or sources and should belogged.

Voids — Voids (honeycomb, popcorn) are indicatorsof trapped air, inadequate vibration, or insufficientmortar to effectively fill the spaces among coarseaggregate particles. Voids should be described andthe volume percent estimated.

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Segregation of components — Concrete compo-nents can become segregated or concentrated duringplacement. Large aggregate sizes can separate fromfine aggregate, and paste can separate from theaggregate, especially near forms or finishedsurfaces.

Cold joints or lift lines — Weak joints or zonescan form in concrete due to long periods betweenbuckets or mixer loads. Poor vibration or poor orimproper preparation of previous lift surfaces canform zones of weakness or actual planes similar tojoints in rock. These surfaces, called lift lines,should be described and any material on thesurfaces described. Lift lines can be very subtle anddifficult to locate. Design or construction data oftenprovide clues as to where to look for lift lines andconstruction joints. The core should be examinedwet. Clues to lift line locations are: (1) alignedaggregate along the surfaces each side of a line,(2) coarser aggregate above the lift line than is belowthe line, (3) different shape, gradation, orcomposition of aggregate above and below the liftline, (4) a thin line of paste on the lift line, and(5) no aggregate crosses the lift line.

Steel or other imbedded items — Reinforcing steeland orientations should be described as well as othermaterials encountered such as timber, steel lagging,dirt, or cooling pipes.

Changes in color of the cement — Changes inpaste color can indicate reaction products or changesin cement type or cement sources and should belogged.

Aggregate-paste bond — The bond between theaggregate and cement should be described. A goodbond is characterized by concrete breaking through

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the aggregate and not around the particles. A fairbond is characterized by concrete breaking throughand around the aggregate. A poor bond has concretebreaking around the aggregate.

Aggregate rock type — The aggregate rock typecan be important in determining the causes ofconcrete problems. For example, limestone oftenhas chert inclusions suggesting an aggregatereaction, whereas an igneous rock such as graniteprobably will not react with cement. Both the coarseand fine aggregate should be examined.

Aggregate shape — Aggregate shape is usuallyunique to each source. Rounded or subroundedaggregate is probably natural. Angular (sharp)aggregate is probably crushed.

Mechanical breaks — Mechanical breaks in thecore and whether the break is around or through theaggregate should be noted.

Chapter 11

INSTRUCTIONS FORLOGGING SOILS

General

All subsurface investigations of soils for constructionmaterials and for most engineering purposes using testpits, trenches, auger holes, drill holes, or otherexploratory methods should be logged and describedusing the standards in USBR 5000 [1] and 5005 [1](Unified Soil Classification System [USCS]) in accordancewith the established descriptive criteria and descriptorspresented in chapter 3 and the guidelines presented inthis section.

All investigations associated with land classification forirrigation suitability, as well as data collection andanalyses of soil and materials related to drainage inves-tigations, should be logged and described using theU.S. Department of Agriculture terminology outlined inappendix I to Agriculture Handbook No. 436 (SoilTaxonomy), dated December 1975 [2].

Test pits and auger holes may be logged on a form(figure 11-1), or logs may be computer generated. Formetric design studies and specifications, information is tobe in metric units. For specifications using English units,the written soil description should use metric units forthe description of soil particle sizes (millimeters insteadof inches). Example word descriptions are shown infigures 11-2 through 11-11.

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Figure 11-1.—Log of test pit or auger hole.

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Figure 11-2.—Clean coarse-grained soils.

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Figure 11-3.—Fine-grained soils.

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Figure 11-4.—Soil classifications based on laboratory test data.

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Figure 11-5.—Auger hole with samples taken.

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Figure 11-6.—Reporting laboratory classification inaddition to visual classification.

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Figure 11-7.—Undisturbed soils.

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Figure 11-8.—Coarse-grained soils with fines.

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Figure 11-9.—Coarse-grained soils with dual symbols.

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Figure 11-10.—Reporting in-place density tests andpercent compaction.

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Figure 11-11.—Soil with measured percentages ofcobbles and boulders.

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Formats for Test Pits and Auger Hole Logs

General Instructions

The following subsection provides general instructions forlog format and descriptions. Refer to chapter 3 fordescriptive criteria, classification, and group names andsymbols.• Capitalize the group name. If cobbles and boulders arepresent, include them in the typical name.

• Describe plasticity of fines as:

“approximately 30 percent (%) fines with high plasticity”“approximately 60% fines with low to medium

plasticity”“approximately 10% nonplastic fines”

• Give results of hand tests when performed.

• Use “reaction with hydrochloric acid (HCl).”

• Do not give unnecessary information such as “no odor,”“no gravel,” and “no fines.”

However, the negative result of a hand test is positive in-formation and should be reported as “no dilatancy,”“nonplastic,” “no dry strength,” or “no reaction with HCl.”

For reporting maximum particle size, use the following:Fine sandMedium sandCoarse sand5-millimeter (mm) increments from 5 mm to 75 mm25-mm increments from 75 mm to 300 mm100-mm increments over 300 mm

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For example, “maximum particle size 35 mm” or“maximum particle size 400 mm” are the correct formatand size increment.

Table 11-1 is a checklist for log descriptors. Format fordescriptions, results, and other information are in thefollowing subsections.

Table 11-1.—Checklist for the description of soils in test pit and auger hole logs

1. Group symbol. - Capitalized and shown in the left-hand column.2. Depth. - Depths of interval classified, shown in eithermeters or feet and tenths of units in second column fromthe left.3. Identification of sample. - Type and size of sample andorigin of sample, shown in third column from the left.4. Classification and description column. -

a. First paragraph. -(1) Depth of interval classified(2) Group name capitalized(3) Percent of fines sand and gravel by weight

(include trace amounts but not added topercentage which must equal 100 percent)

(4) Description of particles(a) Particle size range: describe as either

gravel - fine or coarse, or sand—fine,medium, or coarse

(b) Hardness of particles (coarse sand andlarger)(c) Particle angularity (angular,

subangular, sub-rounded, or rounded)(d) Particle shape (flat, elongated, or flat

and elongated)(e) Maximum particle size or dimension

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(5) Description of fines(a) Plasticity (nonplastic, low, medium, or

high)(b) Dilatancy (none, slow, or rapid)(c) Dry strength (none, low, medium, high,

or very high)(d) Toughness (low, medium, or high)

(6) Moisture condition (dry, moist, or wet)(7) Color (moist color)(8) Odor (mention only if organic or unusual)(9) Reaction with HCl (none, weak, or strong)

b. TOTAL SAMPLE (BY VOLUME): second para-graph, if applicable - i.e., more than 50 per-cent plus 75-mm material(1) Percent of cobbles and percent of boulders (2) Same information as item 4.a (4)

c. IN-PLACE CONDITION: third paragraph(second paragraph if less than 50 percentoversize)(1) Consistency; fine-grained soils only (very

soft, soft, firm, hard, or very hard) (2) Structure (stratified, lensed, slickensided,

blocky, fissured, homogeneous)(3) Cementation (weak, moderate, strong)(4) Moisture (if an in-place condition

paragraph is included, moisture is notdescribed in the first paragraph)

(5) Color (if an in-place condition paragraph isincluded, color is not described in the firstparagraph)

(6) Result of in-place density and/or moisturetests

d. GEOLOGIC INTERPRETATION: (fourth para-graph) geologic description including geneticname, stratigraphic name if known, and anylocal name.

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5. Remarks block. - Provide additional description orremarks such as root holes, other debris found, caving,degree of difficulty to auger or excavate, reason forrefusal or reached predetermined depth, and waterlevel information or hole completion.

Figure 11-12 is a field form for logging soils.

Reporting by Method of Classification

Preparation of Logs Based on Visual Classifica-tion.—List fines, sand, and gravel in descending order ofpercent (must add up to 100 percent). For visual classi-fication, estimate percentages to the closest 5 percent.Precede the estimated percentages with “approx.,” not“about.” If a component is present but is less than5 percent of the total, use “trace.” “Trace” is not includedin the 100 percent.

Preparation of Logs Based on Laboratory Classifi-cation.—When logs are prepared using laboratoryclassifications (based on laboratory tests), the informationmust be presented on the log as shown in figure 11-4.The difference between a laboratory and a visualclassification is depicted in figure 11-6.

The visual classification should not be changed, norshould the estimated percentages, plasticity description,or the results of the hand tests (dry strength, dilatancy,and toughness) be changed to reflect laboratory testsresults. The visual classification is based on the totalmaterial observed; whereas, the laboratory classificationis based on a representative sample of the material.

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FIELD FORM—SOIL LOGGING HOLE NO. ____

DATE _______ PROJECT ___________________ FEATURE ___________________AREA _________________ DRILLER _________ LOGGED BY __________________

SAMPLE INTERVAL AND TYPE:Type MoistureSample SampleInterval _________ Sample Weight (Lbs) ______ Interval___________________

Typical Name __________________________________________________________Group Symbol _________________________________________________________

SIZE DISTRIBUTION, CHARACTERISTICS:(5-mm increments from 5 to 75 mm, 255-mm increments from 75 to 300 mm, 100mmincrements over 300 mm)

Boulders (>300 mm) __% (vol.) Max. size (mm) __ Hardness __ Angularity _____

Cobbles (75-300 mm) __% (vol.) Max. size (mm) ___ Hardness ___ Angularity ____

Gravel __% Coarse (20-75 mm) __ Fine (5-20 mm) ___ Hardness ___ Angularity __

Sand ___% Coarse ___ Medium ___ Fine ___ Hardness ___ Angularity _____

Fines _____%

Plasticity: Nonplastic _____ Low _____ Medium _____ High _____Dilatancy: No _____ Slow _____ Rapid _____Dry Strength: No ____ Low ____ Medium ____ High ____ Very High ____Toughness: Low _____ Medium _____ High _____

Maximum Size: Fine Sand ____ Medium Sand ____ Coarse Sand ____ ____mm

Moisture: Dry _____ Moist _____ Wet _____

Color _______________ Odor __________ Organic Debris and Type ___________

Reaction with HCl: None _____ Weak _____ Strong _____

EXCAVATING/AUGERING/DRILLING CONDITIONS:

Hardness: Very Soft _____ Soft _____ Hard _____ Very Hard _____

Penetration Action: Smooth ___ Mod. Smooth ___ Mod. Rough ___ Rough ____

Penetration Rate: Very Fast ____ Fast _____ Slow _____ Very Slow _____

PAGE ___ OF ___

Figure 11-12.—Field form - soil logging.

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The specimens for testing are to be samples that repre-sent the entire interval being described (see USBR 7000and 7010 [1]). The material collected must be split orquartered to obtain the specimen that is to be tested inthe laboratory.

Coefficients of uniformity and curvature (Cu and Cc) areto be calculated and reported on the logs for coarse-grained materials containing 12 percent or less fines.

Laboratory gradation percentages and Atterberg limitsare to be reported to the nearest whole number.

Procedures for Reporting Laboratory Data in Addi-tion to Visual Classification and Description.—Insome instances, gradation analyses and Atterberg limittests are performed on soil samples in conjunction withpreparation of logs of test pits or auger holes. These datashould be shown on the logs and clearly identified aslaboratory test data.

Specimens for testing are to be from samples thatrepresent the entire interval being described. If this isnot possible, the location of the sample should be given aspart of the word description. The sample taken should besplit or quartered to get the specimen size required fortesting (figure 11-5, interval 0.0 to 9.8 feet (ft).

Laboratory test data are to be presented in a separateparagraph. If the test results indicate a different classi-fication, and therefore different group symbol and/orgroup name than the visual classification, give thelaboratory classification symbol and name in thisparagraph (figure 11-6).

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Note: For logs which incorporate the testresults, the statement “Classification bylaboratory” should be placed in the “Remarks”portion of the log.

Coefficients of uniformity and curvature (Cu and Cc) areto be calculated and reported on the logs for coarse-grained materials containing 12 percent or less fines.

All laboratory gradation percentages and Atterberg limitsare to be reported to the nearest whole number.

Reporting Undisturbed (In-Place) Conditions

List in-place conditions on logs of test pits in a separateparagraph (figure 11-7). Do not give in-place soil condi-tions (consistency, compactness) on auger hole logs(unless the holes are large enough to inspect). Instead,describe difficulty of augering (figure 11-8). Also describecaving or any other unusual occurrences during drillingof the auger hole.

In-place density tests are often performed in test pits ortrenches. When a large quantity of logs are reviewed,density information on the log can save time, even thoughadditional time is required for preparation of the log.

Results of in-place density tests that are performed intest pits or trenches are to be included on the log in thedescriptive paragraph on in-place conditions, asillustrated in figure 11-10.

Results of any laboratory compaction tests (Proctor, mini-mum and maximum density) performed on the materialfrom the in-place density tests or from the pit or trenchare to be included on the log.

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For pipeline investigations, the percent of the maximumdry density or the percent relative density should be inparentheses on the logs (figure 11-10).

Densities are reported to the nearest 0.1 pound per cubicfoot (lb/ft3) or 1 kilogram per cubic meter (kg/m3).Moisture content is reported to the nearest 0.1 percent.Percent of laboratory maximum dry density or relativedensity is reported to the nearest whole number.

Geologic Interpretations

Geologic interpretations should be made by or under thesupervision of a geologist. Give geologic interpretation ina separate paragraph (figure 11-7). Interpretation shouldalso be included in the narrative section of the materialsportion of the design data submittals.

Description Formats on Test Pit and Auger HoleLogs for Soils with Cobbles and Boulders

If the soil has less than 50 percent cobbles and boulders(by volume), give the group name of the minus 75-mmportion and include cobbles and/or boulders in the groupname (figure 11-11). Use two paragraphs to describe soil.Refer to chapter 3 for a more complete discussion ofclassification and classification group names and symbols.

• Describe the minus 75-mm fraction in the first para-graph. These component percentages are estimated byweight.

• Describe the total sample in a second paragraph. Thesepercentages are estimated by volume. Even if thepercentage of cobbles and boulders is determined bymeasurement, use “approx.” in the word description.

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If the soil has more than 50 percent cobbles and boulders(by volume), list cobbles and boulders first in the name(figure 11-13). Do not give a group symbol or group name.

• Describe the total sample in the first paragraph.Percentages are estimated by volume.

• Describe the minus 75-mm fraction in a secondparagraph. Percentages are estimated by weight.

Angular particles larger than 75 mm are described as cob-bles and boulders, not as rock fragments. A descriptionof their shape should be provided in the word description.

Description of Materials Other than Natural Soils

Materials which are not natural soils are not described orclassified in the same manner as natural soils. Thesection titled “Use of Soil Classification as SecondaryIdentification Methods for Materials other than NaturalSoils”, chapter 3, outlines the criteria to be followed andprovides example descriptions for test pit and auger holelogs. Refer to appropriate sections in chapter 3 forexample format and descriptions. Figures 11-14 through11-17 show a variety of logs of test pits and auger holesreflecting miscellaneous conditions.

Format of Word Descriptions for Drill Hole Logs

The descriptions of surficial deposits and soil-likematerials in geologic logs of exploration holes should usesimilar descriptive criteria and format established for testpits and auger holes except as noted in the followingparagraphs.

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Figure 11-13.—Soil with more than 50 percent cobbles and boulders.

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Figure 11-14.—Borderline soils.

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Figure 11-15.—Test pit with samples taken.

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Figure 11-16.—Disturbed samples.

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Figure 11-17.—Two descriptions from the same horizon. (Top) Undisturbed soil containing estimated percent

of boulders. (Bottom) Disturbed soil containing trace of cobbles.

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Exceptions to Test Pit and Auger Hole Format and Descriptions for Drill Hole Logs

Unlike test pit logs where geologic interpretations may beprovided at the bottom of the log form, geologic inter-pretations are required on drill hole logs. The geologic classification (e.g., Quaternary Alluvium, QuaternaryGlacial Outwash, Quaternary Landslide, Tertiary BasinFill Deposits) should be provided as main headings on thegeological drill hole log.

Group names are capitalized in all test pit and auger holelogs. Where capitalization of the group name wouldconflict with main headings on drill hole logs, capitalizeonly the first letter of each word of the group name andthe group symbol. If the first letter of each word is notcapitalized, the group name is considered informal usageonly and not a classification. Classification and word description format for drill holelogs is similar to those used for test pit logs. Also,materials recovered from drill holes are generallyconsidered to represent in-place conditions. Thesecriteria do not apply when samples are not recovered orwhen poor recovery precludes classification (figure 11-18).

Samples Recovered from Wash Borings or asCuttings

When drill holes are advanced with a rock bit, water jet,or other nonsampling methods, a group symbol and nameor classification of the recovered materials should not beassigned, nor should in-place descriptions, such asconsistency, be used. However, descriptive criteria, suchas particle size, dry strength, and reaction with HCl,should be provided using the same terminology andformat used for auger holes.

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Figure 11-18.—Drill hole advanced by tri-cone rock bit.

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Descriptions should be preceded by “Recovered cuttingsas . . .” or “Recovered wash samples as. . .” (figure 11-18,interval 0.0-11.7 ft.

Poor or Partial Recovery

Where poor or partial recovery precludes accurate classi-fication, a primary classification should not be assigned,but as much descriptive information as possible should beprovided. Recovered materials, together with drillingconditions, cuttings, and drilling fluid color or losses, maybe used to interpret reasons for losses and types ofmaterials lost. However, an appropriate subheading (i.e.,“Poor Recovery”) should be used (figure 11-19, 2.1 to3.9 ft.

Materials Other Than Soils and Special Cases

As discussed in chapter 3, “Use of Soil Classification asSecondary Identification Methods for Materials OtherThan Natural Soils,” exceptions to the test pit and holeclassification and format are also applicable to hole logs.These special cases include processed or manmadematerials, shells, partially lithified or poorly cementedmaterials and decomposed bedrock, and shallow surficialdeposits or soils. Other special categories of soil-likematerials should be classified by USBR 5000 orUSBR 5005[1]. These are soil-like slide-failure zones orplanes; shear or fault zones; bedrock units which arerecovered as soil-like material or consist of soil-likematerial; and landslides and talus (figures 11-20, 11-21,and 11-22).

Format and classification for these exceptions aredescribed below.

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Figure 11-19.—Log showing poor recovery.

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Figure 11-21.—Log of landslide material (b).

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Processed or Manmade Materials.—Surficial depositssuch as tailings, crushed rock, shells, or slag are assigneda genetic name such as filter, bedding, drain material,shells, tailings, or road base, and a classification groupname and symbol are assigned in quotation marks, forexample: Filter material, “poorly graded sand (SP-SM).”Soil descriptors are then used to describe the materials.

Where drill holes penetrate embankment materials, mainheadings on the drill hole logs should be a classificationof the type of embankment, such as “Zone 3Miscellaneous Embankment.” The materials recovered ineach interval are classified, and group names andsymbols are provided as subheadings. See 1.0- to 3.9-ftand 3.9- to 15.4-ft intervals shown in figure 11-19.

Partially Lithified or Poorly Cemented Materialsand Decomposed Rock.—Descriptions of partiallylithified or poorly cemented materials such as siltstone,claystone, sandstone, and shale or decomposed rock whichare broken down during drilling or field classificationtesting should be classified by an appropriate rock unitname or by geologic formation name, if known, of the in-place materials. The materials are then described usingdescriptors for rock (chapter 4). A soil classification forthe broken down materials should be reported inquotation marks on the drill logs and all figures, tables,drawings, or narrative descriptions. The disaggregatingmechanism (e.g., drilling or testing) should be specified(figure 11-22, interval 17.3 to 67.9 ft).

Shallow Surficial Deposits.—Surficial deposits such asdrill pad or dozer trench fill for drill setups, shallow slopewash, or topsoil materials which will not be used in, orinfluence, design or construction may be classified bygenetic classification (e.g., “fill,” “slopewash,” or “topsoil”).Complete classification descriptions are not required ondrill hole logs; however, a classification name and/or

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symbol may be assigned and is often desirable. Althougha complete description is not required on each log, anadequate description of these materials should beprovided in a general legend or explanation drawing andin the narrative of the report, if not completely describedin drill hole logs.

Slide Failure Zones or Planes, Shear or FaultZones, and Interbeds Recovered as Soil-likeMaterials.—These features should be described usinggeologic names as well as behavior and soilclassifications.

Landslides and Talus.—Surficial deposits such aslandslides and talus should be assigned their geneticgeologic name in the main headings of the drill hole log.Landslide debris composed primarily of soils is classifiedas landslides in the main heading. Soil-like materialsshould be classified and group names and symbolsprovided in the headings. The materials are thendescribed using the descriptive criteria for drill hole logs.Where materials are predominantly rock fragments suchas talus and block slides, the materials should be loggedsimilar to the method used in figure 11-22.

Equipment Necessary forPreparing the Field Log

The following is a list of equipment for field testing anddescribing materials.

Required equipment:

• Small supply of water (squirt bottle)—forperforming field tests

• Pocket knife or small spatula• Materials for taking or preserving samples—sacks,

jars, labels, cloth, wax, heater, etc.

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• Hammer—for hardness descriptors• Tape measure and/or rule (engineer's scale and

metric scale)• Petrie dish for washing specimens• Small bottle of dilute hydrochloric acid [one part

HCl (10 N) to three parts distilled water. Whenpreparing the dilute HCl solution, slowly addacid into the water following necessary safetyprecautions. Handle with caution and storesafely. If solution comes in contact with skin,rinse thoroughly with water.]

• Rags for cleaning hands• Log forms

Optional apparatus:

• Small test tube and stopper or jar with lid• Plastic bags for “calibration samples”• Hand lens• Color identification charts• Paint brush and/or scrub brush and water for

cleaning samples• Marking pens• Protractor• Drillers' reports for drill holes• Comparison samples (in jars): fine gravel—3/4

inchto No. 4 sieve; medium sand—No. 4 to No. 10sieve; and coarse sand—No. 10 to No. 40 sieve

• Small No. 4 and 200 sieves

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Example Descriptions and Format

The examples which follow illustrate the preferredformat, description, and organization, and some of themore significant exceptions to typical standards.

Laboratory Classifications in Addition to Visual Classifications

In some instances, laboratory classifications may bedetermined in addition to the field visual classification.This may be done to confirm the visual classification,particularly when starting work in a new location orbecause the classification may be critical.

The laboratory data used must be reported in a separateparagraph at the end of the work description, as shown inthe examples in figure 11-23. If the laboratory clas-sification is different from the visual classification, as inthe upper example, give the group symbol in the left-hand column and the group name in the paragraph on thelaboratory data.

DO NOT CHANGE THE VISUAL CLASSIFICATION ORDESCRIPTION. The visual classification is based on awidely observed area in the excavation, whereas the labo-ratory classification is based on a sample of the material.

If the visual classification was the best judgment of anexperienced classifier, both are correct in what theyrepresent.

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Figure 11-23.—Geologic interpretation in test pit(sheet 1).

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Word Descriptions for Various SoilClassifications

Figures 11-6 to 11-17 illustrate some typical worddescriptions based on the soil classifications.

Logs are generally typed and single spaced. Theexamples in this manual are presented double spaced forlegibility.

Samples Taken

In addition to the brief description of the samples takenunder the “classification group symbol” column, a morecomplete description of any samples taken from eachdepth interval is included in the word descriptions. Thedescription should include the size of the sample, thelocation represented by the sample, and how the samplewas obtained (e.g., quartering and splitting).

Examples of how to report the sample information for apit or trench are shown in figures 11-24 through 11-33.

Some examples use the abbreviated method of indicatingthe group name with the group symbol. This abbreviatedmethod is described in appendix X5 in USBR 5000,“Determining Unified Soil Classification (LaboratoryMethod)” [1] and chapter 3.

Reporting Laboratory Data

Classifications Based on Laboratory Data

If the soil classification reported on the logs is based onlaboratory data and not a visual classification, this shouldbe clearly and distinctly reflected on the log.

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Figure 11-24.—Geologic interpretation in test pit(sheet 2).

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Figure 11-25.—Geologic interpretation in test pit using a geologic profile (1).

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Figure 11-26.—Geologic interpretation in test pit(sheet 3).

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Figure 11-27.—Geologic interpretation in test pit(sheet 4).

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Figure 11-28.—Geologic interpretation in test pit using a geologic profile (2).

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Figure 11-29.—Geologic interpretation in test pit(sheet 5).

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Figure 11-30.—Geologic interpretation in test pit (sheet 6).

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Figure 11-31.—Geologic interpretation in test pit(sheet 7).

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Figure 11-32.—Geologic interpretation in test pit (sheet 8).

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Figure 11-33.—Geologic interpretation in test pit using a geologic profile (3).

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The laboratory data should be reported on the log form asshown in the examples in figure 11-4.

The location of the sample and any laboratory testsperformed need to be clearly described.

The coefficients of uniformity and curvature (Cu, Cc) areto be calculated and reported for coarse-grained soilscontaining 12 percent fines or less.

Gradation percentages and Atterberg limits are to be re-ported to the nearest whole number.

The fact that the classification is a laboratory classi-fication needs to be indicated in the “classification groupsymbol” column.

The words “about” or “approximately” are not used in theword description.

Soils with More Than 50 Percent Cobbles andBoulders

If the soil contains more than 50 percent (by volume)cobbles and/or boulders:

1. The first paragraph describes the total sampleand includes the information on the cobbles andboulders. The information in the paragraph is thesame as described previously for cobbles andboulders.

2. The words “COBBLES” or “COBBLES ANDBOULDERS” are listed first in the classificationgroup name:

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COBBLES WITH POORLY GRADED GRAVELCOBBLES AND BOULDERS WITH SILTY GRAVEL

3. A classification symbol is not given. Where areport or form requires a classification symbol, usethe words “cobbles” or “cobbles and boulders”instead.

An example of a word description for a soil with morethan 50 percent cobbles and boulders is shown infigure 11-13.

Special Cases for USCS Classification

Some materials that require a classification anddescription according to USCS should not have a headingthat is a classification group name. When thesematerials will be used in, or have influence on, design andconstruction, they should be described according to thecriteria for logs of tests pits and auger holes, and theclassification symbol and group name should be inquotation marks. The heading should be as follows:

TOPSOILDRILL PADGRAVEL ROAD SURFACINGMINE TAILINGSUNCOMPACTED FILLFILL

For example:

Classification symbol Description

TOPSOIL 0.0 to 1.6-ft TOPSOIL—wouldbe classified as “ORGANICSOIL (OL/OH).” About 90%

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fines with low plasticity, slowdilatancy, low dry strength,and low toughness; about 10%fine to medium sand; soft, wet,dark brown, organic odor; rootspresent throughout strata;weak reaction with HCl.

Reporting In-Place Density Tests

In-place density tests are sometimes performed in testpits in borrow areas so that in-place densities can becompared with the expected compacted densities for theembankment. The required volume of material neededfrom the borrow area can also be calculated. The in-placedensity is also used to evaluate the expansion or collapsepotential for certain soils.

The density should be reported in the paragraph onin-place condition. Examples of the format are shown infigure 11-10. The upper example is used when only thedensity is determined. The lower example is used whena laboratory compaction test is also performed tocalculate the percent compaction (or D value if rapidmethod is used) (USBR 7240, [1]). For cohesionless soils,similar information is reported for the maximum indexdensity, the minimum index density, and the percentrelative density.

If the in-place density test hole spans two (or more) depthintervals of classification, the data and comments for thetest should be placed in the interval description corre-sponding to the top of the test hole. At the end of the in-formation reported, the comment (in all capital letters)must be added: “NOTE: TEST EXTENDED INTOUNDERLYING INTERVAL.” An in-place density testshould not span different materials or layers.

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Because the laboratory compaction test is generallyperformed on the material removed from the test hole,note that the data are for a mixture of intervals byadding, “NOTE: COMPACTION TEST PERFORMEDON MATERIAL MIXED FROM TWO DIFFERENTINTERVALS.”

The density units are lb/ft3 or kilonewtons per cubic meter(kN/m3).

Samples Taken

In addition to the brief description of the samples takenunder the “Classification Group Symbol” column, a morecomplete description of any samples taken from eachdepth interval is included in the word description. Thedescription should include the size of the sample, thelocation represented by the sample, and for each sample,how the sample was obtained (e.g., quartering andsplitting).

An example of how to report the sample information foran auger hole is shown in figure 11-17. An example ofhow to report the sample information for a test pit ortrench is shown in the section on word descriptions ofundisturbed samples.

The approximate weight of samples should be stated.

Measured Percentages of Cobbles and Boulders

If the percentages of the plus 3-inch particles are mea-sured, not estimated, the percentages are reported to

the nearest 1 percent. In the word description for theplus 3-inch particles, do not use the term “about” beforethe percentages.

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The procedure for measuring the percent by volume ofcobbles and boulders is given in the test procedure,USBR 7000, “Performing Disturbed Soil Sampling in TestPits”[1]. This method is rarely used; percentages areusually estimated. It is not recommended that thepercentages be measured for auger holes, since the massof material recovered is generally insufficient to obtain areliable gradation of plus 3-inch particles.

Figures 11-23 through 11-33 show a variety of logs of testpits using both the USCS and the geologic interpretationof the parent material. Note that USCS indicates thatbedrock has been altered or weathered to a soil-likematerial. For engineering considerations, use the USCSbut present the rock conditions as well.

BIBLIOGRAPHY

[1] Bureau of Reclamation, U.S. Department of theInterior Earth Manual, Part 2, third edition, 1990.

[2] U.S. Department of Agriculture, AgricultureHandbook No. 436, Appendix I (Soil Taxonomy),December 1975.

Chapter 12

HAZARDOUS WASTE SITEINVESTIGATIONS

General

Hazardous waste site investigations are geologic bynature. Site geology affects how the contaminants enterand migrate through the environment, controls theseverity of the contamination problem, and determines ifand how the contamination is remediated. An accuratecharacterization of site geology is critical for thesuccessful removal and/or remediation of hazardouswaste.

Investigations at hazardous waste sites use the samebasic tenets of geology commonly applied in other areasof engineering geologic exploration. Even though theseengineering geologic investigation techniques areuniversal, certain specialized criteria and regulations arerequired at hazardous waste sites which differ fromtraditional geologic work. This chapter assumes thataccepted geologic procedures and equipment are used athazardous waste sites and only discusses the variationsin the planning, implementation, and documentation ofgeologic field work required at such sites. Documentationat hazardous waste sites plays a very prominent role andinvolves much more effort than other geologicinvestigations.

This chapter provides a general overview of documents,terminology, processes, requirements, and site specificfactors for an investigation. This information can be usedto better prepare or conduct a field program. Muchinformation provided here is extracted from numerousEnvironmental Protection Agency (EPA) guidancedocuments. Hazardous waste investigations involve a

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myriad of documents and processes, mostly referred to byacronyms. See the appendix for an explanation of themore common acronyms.

In hazardous waste investigations, understanding thecontaminant’s physical and chemical properties is veryimportant. These properties are useful for predictingpathways that allow contaminant migration throughcomplex subsurface conditions. The understanding ofsubsurface conditions permits a program designed tobetter investigate and sample potentially contaminatedsoil, rock, and water.

Common Terminology and Processes

The "typical" hazardous waste site remediation processinvolves several investigation phases. Each phaseusually has a different emphasis and a different level ofdetail.

In general, there are two sets of regulations involved inhazardous waste site remediation: Resource Conserva-tion Recovery Act (RCRA) and Comprehensive Environ-mental Response, Compensation, and Liability Act(CERCLA). RCRA regulations are largely confined tooperators and generators of existing facilities, whereasCERCLA regulations are confined to the investigation ofabandoned sites (Superfund). Although most Bureau ofReclamation (Reclamation) activities involve CERCLAinvestigations, wastes generated during the investigationmay fall under RCRA regulations.

According to EPA guidelines (Guidance for PerformingPreliminary Assessments Under CERCLA, EPA/540/G-91/013), EPA uses a structured program to determineappropriate response for Superfund sites. The CERCLA/

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Superfund Amendments and Reauthorization Act of 1986(SARA) process ideally evolves through the followingphases: (1) discovery, (2) preliminary assessment, (3) siteinspection, (4) hazard ranking, (5) remedial investigation,(6) feasibility study, (7) record of decision, (8) remedialdesign, (9) remedial action, and (10) operation andmaintenance. Removal actions may occur at any stage.

Documentation

Proper documentation at jobs involving hazardous wasteis more important than at more "traditional" geologicinvestigation sites. The alleged low concentration valuesfor risks to human health and the associated costs forcontaminant testing are primary reasons for gooddocumentation. Soil contaminants are typically reportedin parts per million (ppm) (milligram per kilogram[mg/Kg]) and water contaminants are typically reportedin parts per billion (ppb) (microgram per liter [µg/L]).Since relatively low concentration levels may influence adecision for an expensive cleanup, the prevention of crosscontamination and proper testing procedures is anecessity. Also, proper documentation is necessary forlegally defensible data.

EPA has established documentation requirements forinvestigations. This chapter discusses the variousdocuments needed by EPA under the Superfund programwith an emphasis on the Sampling and Analysis Plan(SAP). Other documents such as the Health and SafetyPlan (HASP), Spill Prevention Plan, and CommunityRelation Plan are often pertinent to the field operation.

The SAP will assist in preparing the required documentsnecessary before actual site work begins. Specificrequirements for individual programs vary greatly, and

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common sense and regulatory concurrence dictate thelevel of detail needed. The EPA report Guidance forConducting Remedial Investigations and FeasibilityStudies Under CERCLA, Interim Final, October 1988(EPA/540/G-89/004) provides additional details regardingEPA-required documentation.

Work Plan (WP)

The WP includes a review of the existing data(background and study rationale), documents thedecisions to be made during the evaluation process, andpresents anticipated future tasks. The WP alsodesignates responsibilities and sets the project scheduleand cost. The primary use of the WP is to provide anagreed procedure to accomplish the work. The WP alsoprovides other interested agencies (such as localgovernment agencies) the opportunity to review proposedwork. The WP is placed in the Administrative Record.

The WP may include an analysis and summary of the sitebackground and physical setting, an analysis andsummary of previous studies and response actions, apresentation of the conceptual site model (including thenature and extent of contamination), a preliminaryassessment of human health and environmental impacts,additional data needs to conduct a baseline riskassessment, the preliminary identification of generalresponse actions and alternatives, and the data needs forthe evaluation of alternatives.

Sampling and Analysis Plan (SAP)

The SAP provides the "nuts and bolts" of the proceduresto be used at a site and must be site specific. The SAPshould consist of three parts:

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(1) A Field Sampling Plan (FSP) that providesguidance for all field work by defining in detail thesampling and data-gathering methods to be used on aproject.

(2) An Analysis Plan (AP) that describes analysis ofthe collected data, such as the contaminant chemicaldata, the groundwater quality, and the geologicsetting.

(3) A Quality Assurance Project Plan (QAPP) thatdescribes the quality assurance and quality controlprotocols necessary to achieve Data Qaulity Objectives(DQOs). Data Quality Objectives are qualitative andquantitative statements that clarify the studyobjective, define the type of data to collect, determinethe appropriate collection conditions, and specifytolerable decision error limits on the quality andquantity of data needed to support a decision.

The level of detail contained within the SAP varies.Depending on the WP, the testing, analysis, and qualitycontrol may be delegated to a differing lead agency orcontractor. Whether the SAP contains individual FSP,AP, and/or QAPP, the SAP indicates the field personnelroles and responsibilities, the acquired data goals, theanalytical methods, and how these methods meet theDQOs. Guidance for the selection and definition of fieldmethods, sampling procedures, and custody can beobtained from the EPA report Compendium of SuperfundField Operations Methods, December 1987(EPA/540/P-87/001 or National Technical InformationService [NTIS] publication PB88-181557). This report isa compilation of demonstrated field techniques that havebeen used during remedial response activities athazardous waste sites.

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The FSP specifies the actual data collection activities tobe performed. The AP provides the details if changes insampling methods or number of samples need to be made.If the AP is a separate document, the FSP should spellout in detail exactly how and why samples will becollected in the field.

Included with the SAP (sometimes as an appendix to theFSP) are the standard operating procedures (SOPs) to beused during the investigations. The SOPs describe, initem-by-item detail, the exact steps to be followed for eachsampling procedure. Included in the SOPs are calibrationand maintenance requirements for equipment to be used.Manufacturer's recommendations and usage manuals canserve as part of the individual SOPs. Further detailsregarding standardized tasks are given in the EPAQuality Assurance Technical Information BulletinCreating SOP Documents.

The QAPP is a companion document typically writtenwhen the FSP is final. The QAPP ensures that data andthe subsequent analyses are of sufficient quantity andquality to accurately represent the conditions at the site.The QAPP often describes policy, organization, andfunctional activities not addressed within the work plan.

The following is a suggested SAP format.

Example Sampling and Analysis Plan

FSP1. Site Background2. Sampling Objectives3. Sample Location and Frequency4. Sample Designation5. Sampling Equipment and Procedures6. Sample Handling and Analysis

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AP1. Objective(s) of the Data Collection2. Analytical Methods and Software3. Parameters Available and Required4. Analytical Assumptions (Boundaries, Estimated

Data)5. Data Management and Manipulation6. Evaluation of Accuracy (Model Calibration

and/or Sensitivity Analysis)

QAPP1. Project Organization and Responsibilities2. QA Objectives for Measurement3. Sample Custody4. Calibration Procedures5. Data Reduction, Validation, and Reporting6. Internal Quality Control7. Performance and System Audits8. Preventative Maintenance9. Data Assessment Procedures

10. Corrective Actions11. Quality Assurance Reports

Health and Safety Plan (HASP)

Each field activity will vary as to amount of planning,special training, supervision, and protective equipmentneeded. The HASP, prepared to support the field effort,must conform to the Reclamation “Safety and HealthStandards.” The site-specific HASP should be preparedconcurrently with the SAP to identify potential problemsearly in the planning stage, such as availability of trainedpersonnel and equipment. The HASP preparer shouldreview site historical information along with proposedactivities to identify potentially hazardous operations orexposures and to require appropriate protectivemeasures. Appendix B of the Occupational Safety and

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Health Guidance Manual for Hazardous Waste SiteActivities (National Institute for Occupational Safety andH e a l t h / O c c u p a t i o n a l S a f e t y a n d H e a l t hAdministration/U.S. Coast Guard/U.S. EnvironmentalProtection Agency, 1985) provides an example of a genericformat for an HASP. Commercial computer programsthat allow preparers to "fill in the blanks" to producerudimentary HASPs are also available.

A HASP should include, as appropriate, the followingelements:

1.Name of site health and safety officer and namesof key personnel and alternates responsible for sitesafety and health.

2. Listing of the potential contaminants at the siteand associated risk(s).

3. A health and safety risk analysis for existing siteconditions and for each site task and operation.

4. Employee training assignments.

5. A description of personal protective equipment tobe used by employees for each of the site tasks andoperations being conducted.

6. Medical surveillance requirements.

7. A description of the frequency and types of airmonitoring, personnel monitoring, and environ-mental sampling techniques and instrumentationto be used.

8. Site control measures.

9. Decontamination procedures.

10. Standard operating procedures for the site.

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11. A contingency plan that meets the requirements of29 CFR 1910.120(l)(1) and (l)(2).

12. Entry procedures for confined spaces.

13. Local emergency numbers, notification procedures,and a clear map (and written instructions) showingthe route to the nearest medical facility capable ofhandling emergencies arising from a hazardouswaste site.

Spill Prevention Plan (SPP)

All samples, equipment, cuttings, and other materialsthat have been exposed to potential contaminants mustbe decontaminated and/or tested and treated according toApplicable or Relevant and Appropriate Requirement(ARAR). Contingencies must be made for accidentallyreleasing and spreading contaminants into theenvironment during field activities at hazardous wastesites. Contaminants may originate from substancesbrought onto the site for specialized testing (e.g.,standards for chemical testing), from accumulations of"free" contaminants, or from contaminated natural waterwhich is released during sampling or investigations.Sufficient equipment (e.g., drums, absorbents, etc.) mustbe onsite to effectively control spills. In addition, keypersonnel should be identified for the control of spills.Paramount to such planning are spill preventionmeasures. Spill prevention plans may be incorporatedinto appropriate sections of a SAP or HASP, if desired.

Contaminant Characteristics and Migration

A primary difference between conventional engineeringgeology investigations and hazardous waste inves-tigations is that drilling methods may impact thecontaminant sampling results and increase migration

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paths. Lubricants, fuels, and equipment may maskspecific chemical testing or react with the contaminant ofconcern (COC). All samples, waste discharges, andequipment used in the investigations require evaluationin relation to the potential contaminant(s). The followingunique site factors are also important.

Contaminant Properties

Some contaminants are inherently mobile, for example,volatile organic compounds (VOCs). When released,VOCs can migrate rapidly through air, soil, andgroundwater. Other contaminants, such as heavy metalsolids, are less mobile. Heavy metals tend to accumulateon the surface of the ground. Although heavy metals maynot readily migrate into and through the subsurface,heavy metals may still migrate through the air asairborne particles. Understanding the behavior of COCsis very important because behavior will significantlyinfluence the ultimate design of the exploration program.For example, investigations to find gasoline, a lightnonaqueous phase liquid (LNAPL), should concentrate onthe water table surface. Dense, nonaqueous phase liquid(DNAPL) investigations should concentrate towards thebottom of the aquifer(s) or water table. Note that somecontaminants react with investigation materials; e.g.,TCE in high concentrations reacts with polyvinyl chloride(PVC) pipe.

When possible, the typical contaminant investigation willestimate the source type and location. The source typemay be barrels, storage tanks, pipelines, injection wells,landfills, or holding ponds. In investigations that involvegroundwater contamination, the investigation mustaddress collecting samples of material that may bemoving or have moved off site.

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Identifying the contaminant and its behavior within thehydrogeologic environment must be kept foremost inmind while developing the program. Hydrochemicalparameters such as density, diffusivity, solubility, soilsorption coefficient, volatilization (vapor pressure), andviscosity may impact the specific contaminant movement.Biological activities or meteoric waters may impactvarious COCs in the subsurface. Some contaminantsdegrade over time and under some environmentalconditions. In some instances, the degradation product(TCE to vinyl chloride) is worse than the original product.

A general introductory geological hazardous waste inves-tigation reference is the Standard Handbook for Solidand Hazardous Waste Facility Assessments, by Sara,1994. A general introductory reference for environ-mental chemistry is Fundamentals of EnvironmentalChemistry, by Manahan, 1993. A reference on DNAPLmaterials is DNAPL - Site Evaluation by Cohen andMercer, 1993. A reference for groundwater chemical andphysical properties is Groundwater Chemicals - DeskReference, by Montgomery, 1996. Toxicological ProfileSeries published by the U.S. Department of Health andHuman Resources describes physical, chemical, andbiological processes which effect contaminant fate andtransport.

Geologic Factors

The migration of contaminants is dependent on thesubsurface materials and water. The arrangement of thegeologic materials impacts the direction and flow rate ofthe contaminants and groundwater. Geologic factors suchas stratigraphy, structure, and lithology control theoccurrence and movement of water.

Various geologic factors to consider include: depth of soil,depth to bedrock, depth to the water table, seasonal

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variations in water table, water quality characteristics ofsite aquifers, mineralogic compositions of soil and rock,gradation, consolidation, and fracturing. Contaminantcharacteristics, such as property differences between solidor liquid materials, differences in liquid viscosity, ordifferences in liquid density relative to water, mayinfluence how the contaminants interact with geologicfactors and how the contamination plumes will behave.

Hydrologic Factors

Groundwater flow is a function of precipitation, runoff,and infiltration (figure 12-1).

Groundwater flow occurs through two zones: theunsaturated (vadose or aeration) zone and the saturatedzone. Each zone can be either soil or rock. Groundwatermovement is affected by the characteristics of thematerial pore spaces (porosity) and the interconnectivityof the pore spaces (permeability). Water movementoccurs under a hydraulic gradient.

Other terms often used in groundwater are transmissivityand storativity. Both terms are bulk terms used todescribe the water over the entire hydrologic unit. Trans-missivity is directly related to permeability. Storativityis a dimensionless value often incorrectly equated withspecific yield. For a more detailed description, see theBureau of Reclamation Water Resource Technical Publi-cation, Ground Water Manual, second edition, 1995 orGroundwater, by Freeze and Cherry, 1979.

An unconfined aquifer, often referred to as a "water table"aquifer, has no overlying confining layer. Water infiltrat-ing into the ground percolates downward through air-filled interstices of the vadose zone to the saturated zone.The water table, or surface of the saturated groundwater

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379 Figure 12-1.—Aquifer types.

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body, is in contact with the atmosphere through the openpores of the material above and is in balance withatmospheric pressure.

A confined, or artesian, aquifer has an overlying,confining layer of lower permeability than the aquifer.Water in an artesian aquifer is under pressure, and whenthe confining layer is penetrated, the water will riseabove the bottom of the confining bed to an elevationcontrolled by the aquifer pressure. If the confining layertransmits some water into adjacent layers, the aquifer issaid to be a "leaky aquifer." A perched aquifer is createdby beds of clay or silt, unfractured rock, or other materialwith relatively lower permeability impeding thedownward percolation of water. An unsaturated zone ispresent between the bottom of the perching bed and theregional aquifer. Such an aquifer may be permanent ormay be seasonal.

Aquifers are typically anisotropic; i.e., flow conditionsvary with direction. In granular materials, the particleshapes, orientation, and the deposition process usuallyresult in vertical permeability being less than horizontalpermeability. The primary cause of anisotropy on amicroscopic scale is the orientation of platy minerals. Insome rock, the size, shape, orientation, and spacing ofdiscontinuities and other voids may result in anisotropy.These factors should always be considered when modelingcontaminant migration from hazardous waste sites.

After the natural flow conditions at a site are char-acterized, the presence of artificial conditions which maymodify the flow direction or velocity of groundwater isdetermined. Such items as surface water impoundmentsand drainages may influence overall groundwater flowmodels. Also, if existing water wells are present in thearea, pumping may be drawing the contaminants towardthe wells. All possible influences affecting the

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groundwater flow must be identified to modelcontaminant plume migration rates and paths.

Classification and Handling of Materials

Classification of soils for engineering properties isdescribed in chapter 3. “ Instructions for Logging Soilsand Surficial Deposits” (chapter 11) describes loggingprocedures, but there are two significant differences forhazardous waste investigations.

(1) Logging of the soil is often limited to visualinspection of cuttings. The sampling protocol mayprohibit the handling or poking of samples. Oftenthe samples are sealed for chemical testing, and timefor classification is restricted to the period when thesample is being packaged. Size of samples is kept toa minimum to reduce the amount of investigation-derived waste.

(2) All material recovered or generated during aninvestigation (samples, cuttings, water, etc.) shouldbe considered hazardous waste unless proven other-wise. Material removed should not be considered“normal” waste unless tested and permitted.

The RCRA “statutory” definition for hazardous waste isbroad and qualitative and does not have clear bounds.Hazardous waste is defined as material meeting theregulatory definition contained in 40 CFR 261.3.However, the definitions of solid and hazardous wastecontained in 40 CFR 261 are relevant only in identifyingthe waste. Material may still be considered solid orhazardous waste for purposes of other sections of RCRA.Some waste defined under the present regulatory statutescould become hazardous waste in the future.

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From the RCRA document, the definition of hazardouswaste is any

. . .solid waste or combination of solid wasteswhich because of its quantity, concentration, orphysical, chemical, or infectious characteristicsmay: (A) cause, or significantly contribute to, anincrease in mortality or an increase in seriousirreversible, or incapacitating reversible, illness;or (B) pose a substantial present or potentialhazard to humans or the environment whenimproperly treated, stored, transported, ordisposed of, or otherwise managed.

The level of contamination acceptable within the subsur-face is based on a complex formula that involves the riskof exposure; toxicity, mobility, and volume of contami-nants; and the cost of remediation. Soil and rock removedfrom a site cannot be returned to a site after theinvestigation has been completed.

Investigation waste water must be tested and handledunder a different set of rules. If the water is mixed withcuttings, the material is considered a combination of solidwastes. If the water is discharged on a site, the watertypically must meet drinking water standards. EPA cur-rently requires that sole source aquifers have specialproject review criteria for Federal actions possiblyaffecting designated aquifers. Water withdrawn forpublic drinking water supplies currently falls under theSafe Drinking Water Act (SDWA) (Public Law 93-523)regulations, as amended and reauthorized (1974). (See40 CFR 141 G for applicable water supply systems. See40 CFR 143 for applicable water supply systems.) Notethat the number of regulated constituents and theirrespective maximum contaminant levels (MCLs) arefrequently updated.

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Identifying and classifying hazardous waste is describedin Hazardous Waste, by Wagner, 1990. Procedures forsite evaluation are contained in EPA Guidance forConducting Remedial Investigation and FeasibilityStudies Under CERCLA, 1988.

Field Sampling Protocol

One of the most difficult parts of any investigation iscollecting representative samples. A sampling strategymust be efficiently and logically planned which delineatessite location, number of samples collected, types ofsamples collected, testing methods to be used, and theduration and frequency of sampling. The difficulties ofdrilling in the “right” location and the problemsassociated with collecting representative samples issimilar to traditional investigations. However, forhazardous waste investigation, the COC must be con-sidered in both time and space. Statistical considera-tions should be part of the sampling program. The follow-ing are references for sampling statistical considerations:

• Harvey, R.P. “Statistical Aspects of Air SamplingStrategies.” In: Detection and Measurement ofHazardous Gases; edited by C.F. Cullis andJ.G. Firth. Heineman Educational Books, London,1981.

• Mason, B.J. Protocol for Soil Sampling: Tech-niques and Strategies. EPA EnvironmentalSystems Laboratory, Contract No. CR808529-01-2.March 30, 1982. EPA-600/54-83-0020.

• Smith, R., and G.V. James. The Sampling of BulkMaterials. The Royal Society of Chemistry,London. 1981.

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• Environmental Protection Agency. Handbook forSampling and Sample Preservation of Water andWastewater. September 1982. EPA 600/4-82-029.

Sampling Strategies

Investigators must determine the correct number andtypes of samples to be collected, the proper chemicaltesting methods (analytical procedures), and the propersampling equipment before field activities begin. Samplecontainers, preservatives, sample quantities, and properholding times are also dictated by the chosen methods.

Table 12-1 is a list of recommended sampling containersand holding times for various classes of contaminants insoils.

Several sampling strategies are available, each withadvantages and disadvantages. Random sampling usesthe theory of random chance probabilities to choose repre-sentative sample locations. This is appropriate whenlittle information exists concerning the material, loca-tions, etc. Random sampling is most effective when thenumber of sampling locations is large enough to lendstatistical validity to the random selection.

Systematic random sampling involves the collection ofrandomly selected samples at predetermined, regularintervals (i.e., a grid). The method is a common samplingscheme, but care must be exercised to avoid over-sampling of one material or population type over others.

Stratified sampling is useful if data are available fromprevious investigations and/or the investigator hasexperience with similar situations. This scheme reducesthe number of samples needed to attain a specifiedprecision. Stratified sampling involves the division of the

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Table 12-1.—EPA recommended sampling containers, preservation requirements, and holding

times for soil samples

ContaminantContainer1

Preservation2Holding

time3

Acidity P, G 14 days

Alkalinity P, G 14 days

Ammonia P, G 28 days

Sulfate P, G 28 days

Sulfide P, G 28 days

Sulfite P, G 48 hours

Nitrate P, G 48 hours

Nitrate-Nitrite P, G 28 days

Nitrite P, G 48 hours

Oil and grease G 28 days

Organic carbon P, G 28 days

Metals

Chromium VI P, G 48 hours

Mercury P, G 28 days

Other metals P, G 6 months

Cyanide P, G 28 days

Organic compounds

Extractables

Including: Phthalates, nitro-samines, organic pesticides,PCBs, nitroaromatics, iso-phorone, polynuclear aroma-tics hydrocarbons, haloethers,chlorinated hydrocarbons, andtetrachlorodibenzo-p-dioxin(TCDD)

G, Teflon®-lined cap

7 days untilextraction

30 daysafterextraction

Footnotes at end of table.

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Table 12-1.—EPA recommended sampling containers, preservation requirements, and holding times for soil samples (continued)

ContaminantContainer1

Preservation2Holding

time3

Purgeables

Halocarbons andaromatics

G, Teflon®-linedseptum

14 days

Acrolein and acrylonitrate G, Teflon®-linedseptum

3 days

Orthophosphate P, G 48 hours

Pesticides G, Teflon®-linedcap

7 days untilextraction

30 days afterextraction

Phenols G 28 days

Phosphorus G 48 hours

Phosphorus, total P, G 28 days

Chlorinated organiccompounds

G, Teflon®-linedcap

7 days

1 P = polyethylene, G = glass. 2 All samples are cooled to 4 EC. Preservation is performedimmediately upon collection. For composites, each aliquot preservedat collection. When impossible to preserve each aliquot, samples maybe preserved by maintaining 4 EC until compositing and samplesplitting is completed. 3 Samples are analyzed as soon as possible. Times listed aremaximum holding if analysis is to be valid.

Source: Description and Sampling of Contaminated Soils,EPA/625/11-91/002 (1991).

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sample population into groups based on sample char-acteristics. The procedure involves handling each groupor division separately with a simple random samplingscheme.

Judgement sampling introduces a certain amount ofjudgment into the sampling approach and should beavoided if a true random sample is desired. Judgmentsampling allows investigator bias to influence decisions,which can lead to poor quality data or improper conclu-sions. If the local geology is fairly well understood,judgement sampling may provide the most efficient andcost-effective sampling scheme; however, regulatoryconcurrence, rationale, and proper documentation will benecessary.

Hybrid sampling is a combination of the types previouslydescribed. For example, an initial investigation of drumsmight be based on preliminary information concerningcontents (judgement, stratified) and then random sam-pling of the drums within specific population groups(random). Hybrid schemes are usually the method ofchoice for sampling a diverse population, reducing thevariance, and improving precision within each subgroup.

After the appropriate sampling scheme has been chosen,the specific type of samples necessary for characterizationmust be identified. The unique characteristics of the siteCOCs will play an important role in determining whichmedia will be sampled. Some sampling devices aredescribed in this manual or the Earth Manual, parts 1and 2, USBR, 1990 and 1999. A summary of samplingdevices is shown in table 12-2.

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Table 12-2.—Summary of soil sampling devices

Samplingdevice Applications Limitations

Hand-held samplers

Spoons andscoops

Surface soil samplesor the sides of pits ortrenches

Limited to relativelyshallow depths;disturbed samples

Shovels andpicks

A wide variety of soilconditions

Limited to relativelyshallow depths

Augers1

Screw auger Cohesive, soft, or hardsoils or residue

Will not retain dry,cohesionless, orgranular material

Standardbucket auger

General soil orresidue

May not retain dry,cohesionless, orgranular material

Sand bucketauger

Bit designed to retaindry, cohesionless, orgranular material(silt, sand, and gravel)

Difficult to advanceboring in cohesivesoils

Mud bucketauger

Bit and bucket de-signed for wet silt andclay soil or residue

Will not retain dry,cohesionless, orgranular material

Dutch auger Designed specificallyfor wet, fibrous, orrooted soils (marshes)

1 Suitable for soils with limited coarse fragments; only thestoney soil auger will work well in very gravelly soil.

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Table 12-2.—Summary of soil sampling devices (continued)

Samplingdevice Applications Limitations

Augers1

In situ soilrecoveryauger

Collection of soil sam-ples in reusable liners;closed top reduces con-tamination from cavingsidewalls

Similar to standardbucket auger

Eijkelcampstoney soilauger

Stoney soils andasphalt

Planer auger Clean out and flattenthe bottom of predrilledholes

Tube samplers2

Soil probe Cohesive, soft soils orresidue; representativesamples in soft tomedium cohesive soilsand silts

Sampling depthgenerally limited toless than 1 meter

Thin-walledtubes

Cohesive, soft soils orresidue; special tips forwet or dry soilsavailable

Similar toVeihmeyer tube

Soil recoveryprobe

Similar to thin-walledtube; cores arecollected in reusableliners, minimizingcontact with the air

Similar toVeihmeyer tube

1 Suitable for soils with limited coarse fragments; only the stoneysoil auger will work well in very gravelly soil. 2 Not suitable for soils with coarse fragments.

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Table 12-2.—Summary of soil sampling devices (continued)

Samplingdevice Applications Limitations

Tube samplers1 (continued)

Veihmeyertube

Cohesive soils orresidue to depth of10 feet (3 meters [m])

Difficult to drive intodense or hard mate-rial; will not retaindry, cohesionless, orgranular material;may be difficult topull from ground

Peat sampler Wet, fibrous, organicsoils

Power-driven samplers

Split spoonsampler

Disturbed samplesfrom cohesive soils

Ineffective in cohe-sionless sands; notsuitable for collectionof samples forlaboratory testsrequiringundisturbed soil

Thin-walled samplers

Fixed pistonsampler

Undisturbed samplesin cohesive soils, silt,and sand above orbelow water table

Ineffective incohesionless sands

Hydraulicpistonsampler(Osterberg)

Similar to fixed-pistonsampler

Not possible to limitthe length of push orto determine amountof partial samplerpenetration duringpush

1 Not suitable for soils with coarse fragments.

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Table 12-2.—Summary of soil sampling devices (continued)

Samplingdevice Applications Limitations

Thin-walled samplers (continued)

Free pistonsampler

Similar to stationarypiston sampler

Not suitable forcohesionless soils

Open drivesampler

Similar to stationarypiston sampler

Not suitable forcohesionless soils

Pitchersampler

Undisturbed samplesin hard, brittle, cohe-sive soils and ce-mented sands; repre-sentative samples insoft to medium cohe-sive soils, silts, andsome sands; variablesuccess with cohe-sionless soils

Frequentlyineffective incohesionless soils

Denisonsampler

Undisturbed samplesin stiff to hard cohe-sive soils, cementedsands, and soft rocks;variable success withcohesionless materials

Not suitable forundisturbedsampling of cohesionless soils orsoft cohesive soils

Vicksburgsampler

Similar to Denisonsampler except takeswider diametersamples

In addition, the following references may be consulted forsample collection methods:

• Environmental Protection Agency. Characterizationof Hazardous Waste Sites - A Methods Manual,Volume I - Site Investigations. April 1985. EPA600/4-84-075.

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• Environmental Protection Agency. Characterizationof Hazardous Waste Sites - A Methods Manual:Volume II. Available Sampling Methods. September1983. EPA 600/4-83-040, PB84-126929.

• Environmental Protection Agency. A Compendium ofSuperfund Field Operation Methods. December 1987.EPA 540/P-87-001, PB88-181557.

Samples can be either grab or composite samples. Grabsamples are collected at a discrete point, representing onelocation and/or time interval. Composite samples arecollected from several sources which are then accumu-lated to represent a broader area of interest. Therequirements for testing will often dictate which samplingmethod is used. For example, composite samples of soilcannot be used for volatile compounds because portions ofthe contaminants may easily volatilize during collection.

Many soil samples are collected as grab samples. Soilsamples should be collected from areas where dumping,spills, or leaks are apparent. Soil samples should becollected from areas upstream and downstream fromsuspected contaminant entry and in areas wheresediment deposition is significant. Samples can becollected readily from the first 18 inches (450 mm)(depending upon the soil type) by using relatively simpletools, such as spades, scoops, and dredge scoops. If scoopsare used for collecting surface soil samples, purchaseenough scoops to use a new scoop for each sample ratherthan decontaminating scoops between samples. Not onlyis time saved, but cross contamination is kept to aminimum. The COC must also be considered. Ifsampling for heavy metals, metal scoops should not beused, or if sampling for semivolatiles, plastic scoopsshould be avoided. Samples from greater depths usuallyrequire more elaborate methods or equipment, such astest pits, hand augers, thin-wall tube samplers, hand or

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power corers, bucket augers, cutting or wash samples,direct-push tools, etc. The nature of the geologic materialto be sampled will influence significantly the methods touse, but every effort should be made to reduce the amountof investigation-derived waste generated from thesampling method. Direct-push sampling (such as theGeoprobe®) is preferable in that drill cuttings and drillingfluids are not generated.

A useful field pocket guide is available from EPA:Description and Sampling of Contaminated Soils,EPA/625/12-9/002, November 1991. This guide addressessoil characterization, description, sampling, and samplehandling. Within this guide are general protocols for soilsample handling and preparation. The following areprocedures from the guide:

Soil Sample Collection Procedures for Volatiles.—

1. Tube samples are preferred when collecting forvolatiles. Augers should be used only if soil condi-tions make collection of undisturbed coresimpossible. Soil recovery probes and augers withdedicated or reusable liners will minimize contactof the sample with the atmosphere.

2. Place the first adequate grab sample, maintainingand handling the sample in as undisturbed a stateas possible, in 40-milliliter (mL) septum vials or ina 1-liter (L) glass wide mouth bottle with aTeflon®-lined cap. Do not mix or sieve soilsamples.

3. Ensure the 40-mL containers are filled to the top tominimize volatile loss. Secure the cap tightly, butdo not overtighten.

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4. Examine the hole from which the sample wastaken with an organic vapor instrument after eachsample increment. Record instrument readings.

5. Label and tag sample containers, and recordappropriate data on soil sample data sheets (depth,location, etc.).

6. Place glass sample containers in sealable plasticbags, if required, and place containers in icedshipping container. Samples should be cooled to4 degrees Centigrade (EC) as soon as possible.

7. Complete chain of custody forms and ship as soonas possible to minimize sample holding time.Scheduled arrival time at the analytical laboratoryshould give as much holding time as possible forscheduling of sample analyses.

8. Follow required decontamination and disposalprocedures.

Soil Sample Collection and Mixing Procedures forSemivolatiles and Metals.—

1. Collect samples.

2. If required, composite the grab samples or usediscrete grab samples.

3. If possible, screen the soils in the field through aprecleaned O-mesh (No. 10, 2-millimeter [mm])stainless steel screen for semivolatiles, or Teflon®-lined screen for metals.

4. Mix the sample in a stainless steel, aluminum (notsuitable when testing for aluminum), or glassmixing container using appropriate tool (stainlesssteel spoon, trowel, or pestle).

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5. After thorough mixing, place the sample in themiddle of a relatively inexpensive 1-meter (m)square piece of suitable plastic, canvas, or rubbersheeting.

6. Roll the sample backward and forward on thesheet while alternately lifting and releasingopposite sides or corners of the sheet.

7. After thorough mixing, spread the soil out evenlyon the sheet with a stainless steel spoon, trowel,spatula, or large knife.

8. Take sample container and check that a Teflon®liner is present in the cap, if required.

9. Divide the sample into quarters, and take samplesfrom each quarter in a consecutive manner untilappropriate sampling volume is collected for eachrequired container. Separate sample containerswould be required for semivolatiles, metals,duplicate samples, triplicate samples (split), andspiked samples.

10. Secure the cap tightly. The chemical preservationof solids is generally not recommended.

11. Label and tag sample containers, and recordappropriate data on soil sample data sheets (depth,location, etc.).

12. Place glass sample containers in sealable plasticbags, if required, and place containers in icedshipping container. Samples should be cooled to4 EC as soon as possible.

13. Complete chain of custody forms and ship as soonas possible to minimize sample holding time.Scheduled arrival time at the analytical laboratory

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should give as much holding time as possible for scheduling of sample analyses.

14. Follow required decontamination and disposalprocedures.

Water Quality Sample Collection Methods

Surface Water Collection.—Surface water on oradjacent to a suspected hazardous waste site can yieldsignificant information with minimal sampling effort.Surface water can reveal the presence of contaminationfrom several pathway mechanisms. If only a knowledgeof the presence or absence of contamination in the wateris needed, the collection of grab samples will usuallysuffice. If the water source is a stream, samples alsoshould be collected upstream and downstream from thearea of concern. Additional monitoring of surface wateris required of seeps, spills, surface leachates, etc. If thesite has National Pollutant Discharge EliminationSystem (NPDES) outfalls, the discharges should besampled.

Water quality samples are often the most importantmaterial collected at a site. Determining the appropriatenumber of samples and appropriate test method is criticalto a successful program. A good guidance document todevelop a water quality sampling program and providethe reasoning for collecting appropriate water samples isEPA’s Handbook, Ground Water, volumes I and II,EPA/625/6-90/016. There are several factors to considerin the selection of appropriate sampling devices. Timeand money are obvious factors; however, the data use,formation permeability, water depth, and contaminationtype are considerations. Water monitoring goals andobjectives should be addressed, such as:

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• Is the investigation to determine source(s)?

• Are the investigations included for a time criticalremoval action?

• Have the potential contaminants been identified?

• Will there be a follow up risk assessment and/orremediation?

• Are there potential responsible parties (PRPs)involved?

Water samples can be routinely analyzed for current EPAlisted priority pollutants. Alkalinity, acidity, totalorganic halogens, and chemical oxygen demand are oftenindicators of contamination. Routine tests can be used asscreening techniques before implementing more costlypriority pollutant analyses. Bioassessment samples, ifneeded, are described in Rapid Bioassessment Protocolsfor Use in Streams and Rivers, EPA/444/4-89-001. Iftechnical impracticability (Guidance for Evaluating theTechnical Impracticability, EPA Directive 9234.2-25, ornatural attenuation are potential remediation options,additional water quality parameters may need testingconsideration.

G r o u n d w a t e r C o l l e c t i o n . — G r o u n d w a t e rcontamination is usually difficult and costly to assess,control, and remove. Monitoring wells sample a smallpart of an aquifer, depending on screen size, length,placement depth, pumping rates, and other factors. Theuse of wells and piezometers can introduce additionalproblems due to material contamination, inadequateconstruction, and uncertainties of the water zonesampled. Guarding against cross contamination ofmultiple aquifers is important. Proper well constructionrequires significant skill. General guidelines for designand construction of monitoring wells can be found inAmerican Society for Testing Materials (ASTM)

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D5092-90, and guidelines for sampling can be found inRCRA Groundwater Monitoring Draft TechnicalGuidance, EPA/530-R-93-001. For general details ongroundwater quality monitoring well construction, seefigure 12-2. The location of the screen and designing anddevelopment of the screen and sand pack is extremelyimportant in hazardous waste wells. Meeting theturbidity requirement of less than five nephelometricturbidity units (NTUs) is difficult to achieve in the bestcircumstances. Drilling exploration and monitoring wellsin sequence from least to most contaminated areas isgood practice because this minimizes the possibility ofintroducing contaminants into cleaner aquifers or areas.

Although the Compendium of ERT GroundwaterSampling Procedures, EPA/540/P-91/007, providesstandard operating procedures for emergency responseteams, the recommended water quality samplingprocedures for groundwater should be in accordance withEPA’s Low-Flow (Minimal Drawdown) Ground-WaterSampling Procedures, EPA/540/S-95/504. The MinimalDrawdown (MD) method requires using a submersiblepump placed within a riser and not operated until thewell has stabilized. The use of bailers and hand pumps,including automated hand pump systems for waterquality sampling, is discouraged under the MD method.

Limiting water column disturbance is a primary reasonfor installing a dedicated submersible pump. Lowering atemporary sampling device into the water column createsa mini-slug test. The surge of water may induce sedi-ments into the monitoring well. As a result, the watermay not meet the five NTU limit that is part of therequirement for water quality monitoring wells.Sediments can significantly impact testing. If sediment

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Figure 12-2.—Typical monitoring wellconstruction for water quality sampling.

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content is great, additional tests, such as comparing totalversus dissolved solids, should be considered.

Some sampling devices may induce volatilization.Peristaltic pumps, bailers, or hand pumps in low-flowconditions can impact the test results for semi-volatileand volatile compounds. Peristaltic pumps may inducevolatilization if the samples are lifted from depths greaterthan about 25 feet.

The MD method is the preferred sampling collectionmethod because the method uses a low pumping rate (aslow as 0.1 liter per minute) and attempts to limitdrawdown to less than 0.3 foot. If the extraction rateexceeds the ability of the formation to yield water for lowpermeability wells, turbulent conditions can be inducedwithin the borehole. Water may trickle and fall down thecasing. This may potentially increase air exposure andcan entrain air in the water.

Although preferred water quality sampling uses theMD method, other methods may be acceptable to EPA orother regulatory agencies. Devices such as bailers orperistaltic and hand pumps are routinely used at somesites. However, if these devices are used and surge thewell, water sampling protocols often require that the wellbe purged of at least three well volumes of water prior tocollecting a sample.

Whatever sample device is selected, stabilization oftypical water quality parameters, such as pH, redoxpotential, conductivity, dissolved oxygen, and turbidity,are usually required. Which water quality parametersare specified may be dependent on the site conditions andregulatory requirements. The water extraction devicesand procedures should be specified in the FSP and

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correlated to match the site conditions, contaminants,and the regulatory agency requirements.

Vadose Zone.—In addition to sampling aquifers athazardous waste sites, significant information can beobtained by vadose zone sampling. Leachates from COCsmigrate through the vadose zone toward the water table.Samples collected from this zone can indicate the types ofcontaminants present and can aid in assessing thepotential threat to the aquifer below. The various typesof vadose zone monitors can be used to collect watersamples or interstitial pore space vapors for chemicalanalyses and to determine directional flow of COCs. Themain advantage is that such sampling is relativelyinexpensive, simple to do, and can begin supplyinginformation before aquifer monitoring is started. Thetypes of vadose zone monitors, their applications, andtheir use in satisfying the requirements of RCRA arediscussed in Vadose Zone Monitoring at Hazardous WasteSites, EMSL-LV KT-82-018R, April 1983.

Geophysical Methods

Geophysical methods can be used effectively at hazardouswaste sites to assist in defining the subsurface characterof the site, to assist in the proper placement of monitoringwells, to identify buried containers and debris, and todecrease the safety risks associated with drilling intounknown buried materials. A good overview of thesubject of geophysical methods for surveying hazardouswaste sites is: Geophysical Techniques for Sensing BuriedWastes and Waste Migration, prepared for EPA byTechnos, Inc., available from the National Water WellAssociation.

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Miscellaneous Methods

Ambient concentrations of volatile and semivolatileorganics, trace metals, and particulate matter in the aircan provide important data on the atmospheric migrationpath and the populations at risk and can be used forsource evaluations and personnel monitoring. Portablemonitoring devices such as organic vapor analyzers, staindetector tubes, or other monitors can detect the presenceof various atmospheric hazards. Other monitorscommonly used at hazardous waste sites are explosi-meters, oxygen indicators, and personal sampling pumps.

Other specialized sampling techniques may be necessaryat hazardous waste sites to sample media normally notfound in the geologic environment. Wipe samples may beused to document the presence of toxic materials and todetermine that site or equipment decontamination hasbeen adequate. Wipe sampling consists of rubbing amoistened filter paper, such as Whatman 541 filter paper,over a measured area of 15 in2 (100 cm2) to 10 ft2 (1 m2).The paper is then sent to a laboratory for analysis.

Sample Analysis

Onsite laboratories and field analytical equipment, suchas portable gas chromatographs (GCs) and immunoassaykits, can be very beneficial for rapid analyses. Rapid-analysis equipment, such as GCs, immunoassay, andcolorometric kits, are a cost-effective alternative forproviding qualitative and semi-quantitative chemicaldata and for screening large numbers of samples prior tosubmittals for laboratory testing. Another beneficial useof field screening techniques is to provide generalcontaminant level data for samples to be tested in thelaboratory. If a sample has a very high contaminant

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concentration, the sample may have to be diluted beforebeing analyzed to protect the laboratory instruments fromcostly contaminant saturation problems.

There are many standardized testing procedures andmethods for hazardous waste evaluation. Table 12-3 listssome common method series. Each series containsnumerous individual methods. There are over 25 series-500 (determination of organic compounds in drinkingwater) methods. Method 502.1 is for halogenated volatileorganics (purgeable halocarbons) by GC (48 compounds);Method 502.2 is for nonhalogenated volatile organics byGC (6 compounds); Method 503.1 is for aromatic andunsaturated volatile organics (purgeable aromatics) byGC (28 compounds); Method 507 is for nitrogen andphosphorus containing pesticides by GC (66 substances).

The following references discuss some of the commonmethods:

• Methods for the Determination of OrganicCompounds in Drinking Water. EPA-600/4-88/039, December 1988 (500 Series).

• Guidelines Establishing Test Procedures for theAnalysis of Pollutants Under the Clean Water Act.40 CFR Part 136, October 26, 1984 (600 Series,for effluent - wastewater discharged to a sewer orbody of water).

• Test Methods for Evaluating Solid Waste.SW-846, 2nd Edition, Revised, 1985 (8000 Seriesfor groundwater, soil, liquid, and solid wastes).

• Methods for Chemical Analysis of Water andWastes. EPA-600/4-79-020, March 1983.

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Table 12-3.—Common laboratory testing methods1

Method testing series Analytes

100 - EPA method Physical properties - water

200 - EPA method Metals - water

300 - EPA method Inorganic, non-metallics - water (i.e.,alkalinity)

400 - EPA method Organics - water (i.e., chemical oxygendemand, total recoverable petroleumhydrocarbons [TRPH])

500 - EPA method Organic compounds in drinking water

600 - EPA method Organic compounds in effluent

900 - EPA method Biologic - water (i.e., coliform, fecalstreptococcal)

1000 - SW-846 method Ignitability, toxicity characteristic leachingprocedure (TCLP), extractions, cleanup,headspace - solids

3000 - SW-846 method Acid digestion, extractions, cleanup,headspace - solids

4010 - SW-846 method Screening for pentachlorophenol byimmunoassay - solids

5000 - SW-846 method Organic (purge and trap, gaschromatograph/mass spectrometer[GC/MS], sorbent cartridges)

6000 - SW-846 method Inductively coupled plasma (spectrometry)

7000 - SW-846 method Metals - solid waste

8000 - SW-846 method Organic compounds in solid waste

9000 - SW-846 method Inorganics, coliform, oil and greaseextractions - solids

1 This list is not inclusive. Significant overlap and exceptions are present. Methods listed are basic guides to provide the investigator with the generalstructure of the testing method scheme. Numerous individual methods existwithin each series.

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• Standard Methods for the Examination of Waterand Wastewater, 19th edition, Greenberg;American Public Health Association, Washington,DC, 1995.

Reference guides are also available from several sources,such as the Trace Analysis Laboratory Reference Guidesfrom Trace Analysis Laboratory, Inc., 3423 InvestmentBoulevard, No. 8, Hayward, California 94545, telephone(415) 783-6960.

An important consideration in planning any fieldinvestigation program is scheduling the anticipatedactivities. Sufficient time must be allowed for thepeculiarities of hazardous waste work. Several factorsmust be considered: (1) time for establishing work zonesand erecting physical barriers, (2) time for establishingequipment, personnel, and vehicle decontaminationstations, (3) time needed to decontaminate equipmentand personnel, ( 4) loss of worker efficiency due to safetymonitoring, safety meetings, and the use of protectiveclothing, (5) documentation requirements and sample-handling procedures, and (6) inventory and procurementof specialized sample containers, preservative pre-paration, and reference standards, and equipmentcalibrations.

Safety at Hazardous Waste Sites

A major factor during hazardous waste site investigationsis the safety of both the general public and the siteinvestigators. The following references may be ofassistance:

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• Interim Standard Operation Safety Guides.Revised September 1982, U.S. EPA, Office ofEmergency and Remedial Response (OERR).

• Guidance Manual for Protection of Health andSafety at Uncontrolled Hazardous SubstancesSites. EPA, Center for Environmental ResearchInformation (ORD) (in draft, January 1983).

• Reclamation Safety and Health Standards.U.S. Department of the Interior, Bureau ofReclamation, Denver, Colorado, 1993.

• Chemical Substance Hazard Assessment andProtection Guide. OWENS/URIE Enterprises,Inc., Henehan, Urie, & Farlern, Wheat Ridge,Colorado, 1994.

Sample Quality Assurance and Quality Control

Sample QA procedures confirm the quality of the data bydocumenting that integrity is present throughout thesample history. Several sample types are used. Fieldblanks are samples of a "pure" substance, either water,solid, or air, which are collected in the field using thesame procedures as are used for actual environmentalsamples. The purpose of the field blank is to ensure thatoutside influences are not contaminating the truesamples (i.e., vehicular exhaust) during sampling. If"hits" are discovered in the field blank, the questionarises whether contamination not associated with the siteis affecting the true samples.

Trip blanks are samples of a "pure" substance (analyte-free deionized water which accompanies samples withvolatile contaminants) prepared in a laboratory or other

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controlled area and placed in a shipping container withenvironmental samples. The purpose of the trip blank isto ensure that samples were not cross contaminatedduring shipment and storage. "Hits" in a trip blankindicate that COCs were present in a container to adegree sufficient to infiltrate into the trip blank samplejar and, hence, possibly into true samples.

Equipment blanks are used when sampling equipment iscleaned and re-used for subsequent sample collection.The blanks verify the effectiveness of field cleaningprocedures. The final rinse for the sampling equipmentis often made with analyte-free deionized water. Therinse water is run on or through the sampling equipment,collected in appropriate containers and preserved. Thesesamples are usually collected on a schedule, such as onceevery 10 episodes.

Duplicates are samples collected at the same time, in thesame way, and contained, preserved, and transported inthe same manner as a corresponding duplicate.Duplicates are used to determine the precision of thelaboratory method and integrity of the sample fromcollection through testing. Duplicates are typicallycollected once every 10 samples.

Matrix spikes provide the best overall assessment ofaccuracy for the entire measurement system. For waterinvestigation episodes, a laboratory usually prepares thespike samples, sends them to the site, and the spikesample(s) are included in the sample handling andshipping process. The samples are analyzed blind by theoff-site laboratory. Matrix spikes can also be made fromcertified mixtures of a contaminant and clean soil in thefield.

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All types of blanks and duplicates must be prepared inthe same sample containers as actual samples includinglabeling and identification schemes so that the laboratoryanalyzes the sample without knowing that the samplesare quality control (QC) samples (blind testing).

In addition to field QC samples, the analytical laboratoryalso uses QC samples. Method blanks are organic-free ordeionized water carried through the analytical schemelike a sample. Method blanks measure contaminationassociated with laboratory activities. Calibration blanksare prepared with standards to create a calibration curve.Internal standards are measured amounts of certaincompounds added after preparation or extraction of asample. Surrogates are measured amounts of certaincompounds added before preparation or extraction of asample to determine systematic extraction problems.Duplicates and duplicate spikes are aliquots of samplessubjected to the same preparation and analytical schemeas the original sample. Laboratory control standards(LCSs) are aliquots of organic-free or deionized water towhich known amounts of analyte have been added. LCSsare subjected to the sample preparation or extractionprocedure and analyzed as samples.

Field, laboratory, data validation, and report presentationdocuments must be meticulously maintained duringhazardous waste site investigations. All field activitiesshould be recorded in bound, consecutively numbered logbooks. Each entry should be made with indelible ink, andall strike outs should be made by a single line whichallows the original error to be legible and initialed anddated by the person making the correction. Entriesshould include date, weather conditions, personnelinvolved with the activity, the type of activity beingperformed, unusual circumstances or variations made tothe SOPs, and data appropriate to the activity being

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performed. This is a diary of all activities on a site. Theinvestigator responsible for the activity is responsible formaintaining the field log book. An important purpose ofthe field log book is to document any changes made toSOPs. If such changes may affect data quality,concurrence with managers or regulatory personnel isrequired in writing. All records must be under control atall times. Unique project numbers should be assigned toall log books, documents, and reports. All records mustbe maintained and custody documented so thatunauthorized changes or tampering are eliminated. Logbook entries should be photocopied on a regular scheduleto ensure that field data are not lost if the original bookis lost or destroyed.

Activities during an investigation must be reviewed toensure that all procedures are followed. System auditsshould consist of inspections of training status, records,QC data, calibrations, and conformance to SOPs. Systemaudits are performed periodically on field, laboratory, andoffice operations. Each major investigation type shouldbe subject to at least one system audit as early aspracticable. Performance audits include evaluation andanalysis of check samples, usually from laboratoryactivities. Readiness reviews occur immediately prior tobeginning each type of field activity to assess thereadiness of the team to begin work. A checklist ofprerequisite issues, such as necessary equipment,controlled documents, training, assignments, spare parts,field arrangements, etc., are discussed and documented.

If any weaknesses or deficiencies are identified, theinvestigator must resolve them before field activitiesproceed.

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Sample Management

There must be control and documentation of all samplesafter the environmental samples are collected in the field.The proper quantity of a sample must be collected to havesufficient volume for the subsequent analysis. The propersample container and preservative must be used so thatsample integrity is not compromised. Many types ofsamples (e.g., volatiles) must be cooled, usually to 4 EC,throughout their history after collection. The properanalytical methods must be identified to obtain thedesired result. The laboratory must handle and track thereceived samples in a timely and accurate manner toensure that the results are correct.

Sample Custody

Sample custody is a prime consideration in the propermanagement of samples. Sample custody is designed tocreate an accurate, written, and verified record that canbe used to trace the possession and handling of thesamples from collection through data analyses andreporting. Adequate sample custody is achieved bymeans of QA-approved field and analyticaldocumentation. A sample is considered in custody if thesample is (1) in one's actual physical possession, (2) is inone's view after being in one's physical possession, (3) isin one's physical possession and then locked up orotherwise sealed so that tampering will be evident, or(4) is kept in a secure area restricted to authorizedpersonnel only. Personnel who collect samples arepersonally responsible for the care and integrity of thesecollected samples until the samples are properlytransferred or dispatched. To document that samples areproperly transferred or dispatched, sample identification

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and chain of custody procedures must be followed.Sample custody in the field and in transit involves thesteps described below.

Sample Identification.—The sample must first beproperly and uniquely identified. Sample identificationentails establishing a scheme which ensures that eachsample is identified in such a way that one sample cannotbe mistaken for another. Examples of sample labels areshown in figure 12-3. Labels must be filled outimmediately after the sample is collected to ensure thatcontainers are not later misidentified. Indelible ink mustbe used on all labels, and the writing must be legible. Forsamples which require preservation, the sample labelsmust have a space on the label reserved for noting thepreservative added, or other treatments, such as filtering,compositing, etc. Labels can be removed from a samplejar during shipment, especially if the accompanying icemelts and saturates the shipping labels. Double-labelsamples such as sacked soil whenever possible orcompletely wrap the label over the sample bottle withwide, water-proof tape. Also record the collection of eachsample in the field log book and chain of custody records. Chain of Custody.—Once all samples for a specific sam-pling task have been collected, the sampler(s) will com-plete the chain of custody record (figure 12-4). Specificprocedures for completing this form should be included inthe work plan documents specific to the project. Thisrecord accompanies the samples to their destination. Allsamples typically are transferred from the sampletransport container (e.g., cooler) and kept in the exclusionzone until transferred to a noncontaminated sampletransport container in the contamination reduction zone.The samples, with accompanying documentation, are

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Figure 12-3.—Soil and water sample identification labels.

HA

ZA

RD

OU

S W

AS

TE

413 Figure 12-4.—Chain of custody record.

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then prepared for either distribution to the onsitelaboratory or shipment to an analytical laboratory in thesupport zone.

When transferring the possession of samples, theindividuals relinquishing and receiving the samples willsign, date, and note the time on the chain of custodyrecord. This record documents sample custody transferfrom the sampler to the analyst. Note that somecommercial shippers (such as Federal Express) do notsign chain of custody records but do prepare separateshipping documents which indicate receipt of thecooler(s). When samples are passed among fieldpersonnel while still onsite, chain of custody records donot need to be signed, as long as physical possession isretained by identified, responsible personnel duringtransit of the container(s). Packaging

Samples must be packaged properly for shipment anddispatched to the appropriate laboratory for analysis; aseparate record accompanies each shipment. Sampleswithin shipping containers will be sealed for shipment tothe laboratory by using custody seals (figure 12-5). Sealsare made of paper, with adhesive backing, so that theywill tear easily to indicate possible tampering. There aretwo methods of using custody seals. One method is toplace several sample containers in individual plastic bags(or boxes) within the shipping container and then placethe custody seal along the only opening of each bag. Anadvantage of this scheme is that the seal is not exposedto outside influences; but the disadvantages are that thebags are very pliable, and shifting may cause the seal tobreak, and the seal may become immersed in water if icemelts around the bags. The second method is to place thecustody seal on the outside of the cooler, along a seam of

HA

ZA

RD

OU

S W

AS

TE

415 Figure 12-5—Custody seal.

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the lid. The advantage of this method is that the seal isstuck to the solid body of the cooler. The maindisadvantage is that the seal is exposed to handling bythe shipping company and other personnel from the fieldto the laboratory. The seal must not be broken acci-dentally because a broken seal will place all thesamples represented by the seal in jeopardy ofdisqualification due to tampering. An option may be toplace clear tape over the seal as added protection.

The samples within a container must be packed to avoidrattling and breakage. Styrofoam "popcorn" or bubblepack sheeting are acceptable packing materials. Organicpacking materials, including sawdust, should be avoideddue to the possibility of becoming wet from melting ice.Each sample jar should be wrapped such that jar-to-jarcontact is avoided. Also, it is usually desirable to placeice at the bottom of the container, and place the samplesabove the ice, with a water-proof barrier between the iceand samples. This way, if the ice melts, there is alessened probability of the samples becoming immersed.If time is available, ice should be double-wrapped, usingseveral "ice packages" to lessen spillage potential.Chemical ice packs and dry ice should be avoided, ifpossible, to lessen the chance of chemical contamination.The chain of custody record must accompany eachcontainer and list only the samples contained within thespecified cooler. The original chain of custody recordshould be sealed in a "zip-lock" plastic bag and taped tothe inside top of the cooler lid. When the laboratoryopens a cooler, the number and identification of eachsample contained within the cooler must exactly matchthe corresponding chain of custody record. A copy of thechain of custody record is to be retained by theinvestigator or site manager, and a copy is also retainedby the laboratory. A three-carbon copy type chain ofcustody record is best.

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The water drain at the lower edge of the cooler must besealed so there is no possibility of the drain opening. Ifany leakage occurs from a cooler containing environ-mental samples, the shipping company will cease ship-ment and delay the arrival of the samples, possiblyexceeding the holding times of the contained samples. Ashipping company may have unique requirements; but asa general rule, the weight of a cooler should not exceed50 to 70 pounds. If sent by mail, the package must bereceipt requested. If sent by common carrier, a govern-ment bill of lading can be used. Proper shipment trackingmethods must be in place. Copies of all receipts, etc.,must be retained as part of the permanentdocumentation.

Upon arrival at the laboratory, the containers will beopened, the custody seals inspected and documented, andany problems with chain of custody, temperature, orsample integrity noted. The laboratory custodian willthen sign and date the chain of custody record and enterthe sample identification numbers into a bound,paginated log book, possibly assigning and cross-referencing a unique laboratory number to each samplereceived. The laboratory then controls the samplesaccording to the SOPs specified in their work plandocuments.

Decontamination

Decontamination consists of removing contaminantsand/or changing their chemical nature to innocuoussubstances. How extensive decontamination must bedepends on a number of factors, the most important beingthe type of contaminants involved. The more harmful thecontaminant, the more extensive and thorough decon-tamination must be. Less harmful contaminants may

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require less decontamination. Only general guidance canbe given on methods and techniques for decontamination.The exact procedure to use must be determined afterevaluating a number of factors specific to the site.

When planning site operations, methods should bedeveloped to prevent the contamination of people andequipment. For example, using remote sampling tech-niques, using disposable sampling equipment, wateringdown dusty areas, and not walking through areas ofobvious contamination would reduce the probability ofbecoming contaminated and require a less elaboratedecontamination procedure.

The initial decontamination plan is usually based on aworst-case situation. During the investigations, specificconditions are evaluated including: type of contaminant,the amount of contamination, the levels of protectionrequired, and the type of protective clothing needed. Theinitial decontamination system may be modified byadapting it to actual site conditions.

APPENDIX

ABBREVIATIONS AND ACRONYMSCOMMONLY USED IN

BUREAU OF RECLAMATIONENGINEERING GEOLOGY

AND RELATED TO HAZARDOUS WASTE

(Many are modified from A.A.P.G. Committeeon Stratigraphic Correlations)

Acronyms and Abbreviations Commonly Used in Bureau of Reclamation Engineering Geology

A Apparent trace

acre-ft Acre-feet

acre-ft/d Acre-feet per day

acre-ft/yr Acre-feet per year

AGI American Geological Institute

AP Analysis Plan

APSRS Aerial Photography Summary RecordSystem

ARAR Applicable or Relevant and AppropriateRequirement

ASCS Agricultural Stabilization andConservation Service

ASTM American Society for Testing Materials

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ASTM/USCS American Society for Testing Materials/Unified Soil Classification System

b As a suffix, with boulders

BJ Bedding joint

c As a suffix, with cobbles

CADD Computer assisted design and drafting

CERCLA Comprehensive EnvironmentalResponse, Compensation, andLiability Act

CH Fat clay

CL Lean clay

CL Cleavage

CL-ML Silty clay

cm Centimeter

cm2 Square centimeter

cm/s Centimeter per second

COC Contaminant of concern

D Dip trace

DI Durability Index

DLS Detail line survey

DNAPL Dense, nonaqueous phase liquid

DQOs Data Quality Objective

ABBREVIATIONS

421

EPA Environmental Protection Agency

ft Foot

ft2 Square foot

ft3 Cubic foot

ft3/s Cubic foot per second

ft/yr Feet per year

FJ Foliation joint

FSP Field Sampling Plan

FZ Fracture zone

g As a prefix, gravelly; as a suffix, withgravel

gal Gallon

gal/min Gallon per minute

GC Clayey gravel

GC-GM Silty, clayey gravel

GC/MS Gas chromatograph/mass spectrometer

GC Gas chromatograph

GM Silty gravel

GP Poorly graded gravel

GP-GC Poorly graded gravel with clay

GP-GM Poorly graded gravel with silt

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GPS Global Positioning System

GW Well graded gravel

GW-GC Well graded gravel with clay

GW-GM Well graded gravel with silt

H1 Extremely hard

H2 Very hard

H3 Hard

H4 Moderately hard

H5 Moderately soft

H6 Soft

H7 Very soft

HASP Health and Safety Plan

HCl Hydrochloric acid

ID Inside diameter

IF Incipient fracture

IJ Incipient joint

in Inch

in2 Square inch

in3 Cubic inch

JT Joint

ABBREVIATIONS

423

k Hydraulic conductivity

kPa Kilopascal

kg/cm2 Kilogram per square centimeter

km Kilometer

kN Kilonewton

kN/m3 Kilonewton per cubic meter

L Liter

lbf/in2 Pound-force per square inch

lb/in2 Pounds per square inch

lb/ft3 Pounds per cubic foot

LCS Laboratory control standard

LL/PI Liquid limit/plasticity index

LNAPL Light nonaqueous phase liquid

L/sec Liter per second

m Meter

m2 Square meter

m3 Cubic meter

m3/s Cubic meter per second

m3/yr Cubic meter per year

MB Mechanical break

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MCL Maximum contaminant level

mg/Kg milligram per kilogram

MH Elastic silt

mi Mile

ML Silt

mm Millimeter

NAD North American Datum

NASC North American Stratigraphic Code

NCC National Cartographic InformationCenter

NGI Norwegian Geotechnical Institute

NPDES National Pollutant DischargeElimination System

NTIS National Technical Information Service

NTU Nephelometric turbidity unit

OD Outside diameter

OERR Office of Emergency and RemedialResponse

OH Organic clay

OL Organic silt

OSHA Occupational Safety and Health Administration

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425

Pa Pascals

PRP Possible responsible party

PCB Pentachlorobenzene

ppb Part per billion

ppm Part per million

PSI Pound-force per square inch

PT Peat

PVC Polyvinyl chloride

QAPP Quality Assurance Project Plan

QC Quality control

RCRA Resource Conservation Recovery Act

Reclamation U.S. Bureau of Reclamation

RF Random fracture

RMR Rock Mass Rating System GeomechanicsClassification

RQD Rock Quality Designation

RSR Rock Structure Rating

S Strike trace

s As a prefix, sandy; as a suffix, with sand

SAP Sampling and Analysis Plan

SC Clayey sand

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SC-SM Silty, clayey sand

SDWA Safe Drinking Water Act

SM Silty sand

SOP Standard operating procedures

SP Poorly graded sand

SP-SC Poorly graded sand with clay

SPT Standard Penetration Test

SP-SM Poorly graded sand with silt

SW Well graded sand

SW-SC Well graded sand with clay

SW-SM Well graded sand with silt

TBM Tunnel boring machine

TCE Trichloroethlyene

TCLP Toxicity characteristic leachingprocedure

TRPH Total recoverable petroleumhydrocarbons

URCS Unified Rock Classification System

USCS Unified Soil Classification System

USDA United States Department of Agriculture

USGS United States Geological Survey

ABBREVIATIONS

427

VOC Volatile organic compound

WP Work plan

yd3 Cubic yard

µg/L microgram per liter

µm Micrometer

EC degrees Centigrade

EF degrees Fahrenheit

Commonly Used Acronyms and AbbreviationsRelated to Hazardous Waste

ARAR Applicable or relevant and appropriaterequirement

AST Above ground storage tank

AP Analysis plan

BADT Best available demonstrated technology

BAT Best available technology or bestavailable treatment

CAA Clean Air Act

CERCLA Comprehensive Environmental Response,Compensation, and Liability Act(Superfund)

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CERCLIS Comprehensive Environmental Response,Compensation, and LiabilityInformation System

COD Chemical oxygen demand

CRP Community Relations Plan

CRZ Contaminant reduction zone

CWA Clean Water Act (aka FWPCA)

DQO Data quality objectives

EPA Environmental Protection Agency

FS Feasibility study

FSP Field sampling plan

HASP Health and safety plan

HRS Hazard ranking system

HS Head space (analysis)

IDL Instrument detection limit

IDLH Immediately dangerous of life andhealth

LEL Lower explosive limit

LFL Lower flamability limit

LUST Leaking underground storage tank

MCL Maximum contaminant level (SDWA)

MDL Method detection limit

ABBREVIATIONS

429

MSDS Material safety data sheet

NCR Nonconformance report

ND Nondetect

NFRAP No further remedial action planned

NPDES National Pollutant Discharge EliminationSystem

NPL National Priority List

NTIS National Technical Information Service

OSWER Office of Solid Waste and EmergencyResponse

PA Preliminary assessment

PCB Polychlorinated biphenyl

PEL Permissible exposure limit or personalexposure limit

PPB Parts per billion

PPM Parts per million

PPT Parts per trillion

PPTh Parts per thousand

PRP Potentially responsible party

PS Point source

PVC Polyvinyl chloride

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PWS Public water supply or public water system

QA Quality assurance

QAPP Quality assurance project plan

QC Quality control

QL Quantitation limit

RA Remedial action or removal action or riskassessment

RCRA Resource Conservation Recovery Act

RD Remedial design

RfD Reference dose

RI Remedial investigation

RMCL Recommended maximum contaminantlevels

RME Reasonable maximum exposure

ROD Record of decision

RP Responsible party

RPM Remedial project manager

RQ Reportable quantity

SAP Sampling and analysis plan

SAR Start action request

ABBREVIATIONS

431

SARA Superfund Amendments andReauthorization Act of 1986

SAS Special analytical services

SDWA Safe Drinking Water Act

SF Slope factor

SI Site inspection

SOP Standard operating procedures

SQG Small quantity generator

STEL Short-term exposure limit

STP Sewage treatment plant

SVOC Semivolatile organic chemical(Compound)

SWDA Solid Waste Disposal Act

TCE Trichloroethylene

TCL Target compound list

TCLP Toxicity characteristic leaching procedure

TD Toxic dose

TDS Total dissolved solids

THC Total hydrocarbons

TIC Tentatively identified compound

TLV Threshold limit value

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TOA Trace organic analysis

TOC Total organic carbon or total organiccompound

TOX Total organic halogens

TPY Tons per year

TRPH Total recoverable petroleumhydrocarbons

TSCA Toxic Substances Control Act

TSDF Treatment, storage, and disposal facility

TSS Total suspended solids

UEL Upper explosive limit

UFL Upper flamability limit

UST Underground storage tank

VOC Volatile organic chemical (compound)

WP Work plan

WSRA Wild and Scenic Rivers Act

WWTP Wastewater treatment plan