technical aspects of site investigation volume 2

TECHNICAL ASPECTS OF SITE INVESTIGATION.VOLUME II (OF II)

TEXT SUPPLEMENTS

Research and Development

Technical ReportP5-065/TR

Technical Aspects of Site Investigation. Vol II (of II)Text Supplements

R&D Technical Report P5-065/TR

J E Steeds, N J Slade, M W Reed

Research Contractor:WS Atkins


Publishing OrganisationEnvironment Agency, Rio House, Waterside Drive, Aztec West, Almondsbury,BRISTOL, BS32 4UD.

Tel: 01454 624400 Fax: 01454 624409Website: www.environment-agency.gov.uk

© Environment Agency 2000

ISBN: 1 85705 545 4

All rights reserved. No part of this document may be reproduced, stored in a retrieval system,or transmitted, in any form or by any means, electronic, mechanical, photocopying, recordingor otherwise without the prior permission of the Environment Agency.

The views expressed in this document are not necessarily those of the Environment Agency.Its officers, servants or agents accept no liability whatsoever for any loss or damage arisingfrom the interpretation or use of the information, or reliance upon views contained herein.

Dissemination StatusInternal: Released to RegionsExternal: Released to Public Domain

Statement of UseThis document provides guidance to Environment Agency staff, research contractors andexternal agencies, on technical issues relating to site investigation, in relation to landcontamination.

Research ContractorThis document was produced under the Land Quality Function R&D Project P5-065/TR by:

WS Atkins, Woodcote Grove, Ashley Road, Epsom, Surrey, KT18 5BW

Environment Agency’s Project ManagerThe Environment Agency’s Project Manager for Project P5-065/TR was:Ms Jane Morris, Environment Agency, Head Office

Further copies of this report are available from:Environment Agency R&D Dissemination Centre, c/oWRc, Frankland Road, Swindon, Wilts SN5 8YF

tel: 01793-865000 fax: 01793-514562 e-mail: [email protected]


CONTENTS

1. INTRODUCTION 1

2. GOOD PRACTICE OVERVIEW 4

2.1 - Investigation planning – major issues 5

2.2 - Investigation planning checklist – additional issues 5

2.3 - Investigation design checklist 6

2.4 - Summary of desk study information sources 7

2.5 - Typical target information available from a desk study 8

2.6 - Site reconnaissance information checklist 9

2.7 - Example of a site visit record sheet 10

2.8 - Selection of specialist advisors and contractors 11

2.9 - Definitions of professional and technical staff 11

2.10 - Audit trails and record keeping - issues on which confidence may be required 12

2.11 - Further Reading 13

3. SITE CHARACTERISATION RECORDS AND DATA MANAGEMENT 19

3.1 - Example of a daily site diary 20


4. INTRUSIVE AND NON-INTRUSIVE INVESTIGATION METHODS 22

4.1 - Investigation method summary sheets 23

4.2 - Selected photographs of investigation methods 82

4.3 - Choosing an intrusive investigation method 87

4.4 - Worked Example 90

4.5 – Site Investigation Preparation and Implementation Checklist 91


5. SAMPLING 95

5.1 - Checklist of major issues to be considered in preparation for and when sampling 96

5.2 - Labelling samples –information needed 98

5.3 - Type and amount of samples (Table A5 from Environment Agency R&DTechnical Report Number P5-066/TR Secondary Model Procedure for theDevelopment of Appropriate Soil Sampling Strategies (in preparation)) 99

5.4 - Field techniques used in soil sampling (Table A7 from Environment AgencyR&D Technical Report Number P5-066/TR Secondary Model Procedure for theDevelopment of Appropriate Soil Sampling Strategies (in preparation)) 100

5.5 - Sample chain of custody record 101



6. ON-SITE MEASUREMENTS 104

6.1 - Portable instruments commonly used for site investigations 105

6.2 - Groundwater field sampling installations commonly used for site investigations 108

6.3 - Groundwater sample extraction methods commonly used for site investigations 109

6.4 - Soil gas sampling equipment commonly used for site investigations 110


7. CROSS-CONTAMINATION 112

7.1 - Some ways in which cross-contamination can occur during a site investigation 113

7.2 - Examples of well and badly constructed trial pits 115

7.3 - Description of how to drill a borehole through an aquiclude into an aquifer 116

7.4 - Illustration of how to drill a borehole through an aquiclude into an aquifer 117


8. ANALYTICAL STRATEGIES 119

8.1 - What do we mean by Total Petroleum Hydrocarbons (TPH)? 120

8.2 - Key questions to be considered in developing an analytical strategy 121


9. TOPOGRAPHIC SURVEYS 123

9.1 - Example of topographic survey items/information needed 124

9.2 - Permanent ground marker types 125

9.3 - An illustration of the value of assimilating topographic survey data with historicmaps 126

9.4 - Suggested points of measurement on a borehole for the level 126

9.4 - Suggested points of measurement on a borehole for the level 127


10. SITE OBSTRUCTIONS AND GEOTECHNICAL CONSIDERATIONS 129

10.1 - Diagrammatic presentation of Section 6 of the Party Wall etc. Act 1996“Adjacent Excavation and Construction” 130


11. HEALTH AND SAFETY 132

11.1 - COSHH checklist 133

11.2 - CDM checklist 135

11.3 - Requirement flow chart for application of CDM Regulations 136

11.4 - Requirement flow-chart for notification to HSE11.5 – British DrillingAssociation site colour coded site characterisation system 137

11.5 – British Drilling Association site colour coded site characterisation system 138

11.6 - Investigations and surveys safety checklist 139


11.7 - Site visit safety checklist 140

11.8 - Safety method statement checklist 141


12. ENVIRONMENTAL PROTECTION 144

12.1 - Fauna species that are protected together with their resting place. 145

12.2 - Ecological evaluation checklist 146

12.3 - Possible mitigation measures 147

13. OPERATIONAL SITES – ADDITIONAL CONSIDERATIONS 150

13.1 - Checklist for working on operational sites 151

Appendix A Standard format for a site investigation report

1. Introduction 1

1.1 Background 1

1.2 Brief and limitations 1

1.3 Preliminary conceptual model and objectives 1

1.4 Information sources used 1

1.5 Report structure 1

2. Site location and description 2

2.1 Introduction 2

2.2 Site location 2

2.3 Site description 2

2.4 Ecological survey information 3

2.5 Archaeological information 3

3. Site geology, hydrogeology and hydrology 4

3.1 Introduction 4

3.2 Geology 4

3.3 Hydrogeology 4

3.4 Hydrology 4

4. Site history 5

4.1 Introduction 5

4.2 History 5

4.3 Information from statutory authorities 5

4.4 Information from other parties 5

4.5 Potential contamination sources 5


5. Previous site investigation information 6

5.1 Introduction 6

5.2 Findings and recommendations made 6

6. Site investigation design and methodology 7

6.1 Background and site investigation design 7

6.2 Methodology 7

6.3 Analytical suites 8

7. Factual results 9

7.1 Introduction 9

7.2 Summary of physical ground conditions 9

7.3 Made ground - physical conditions 9

7.4 Natural ground - physical conditions 9

7.5 Groundwater - physical conditions 9

7.6 Summary of chemical conditions 10

7.7 Made ground and natural ground – chemical conditions 10

7.8 Perched water/groundwater – chemical conditions 10

7.9 Gas or other monitoring/in situ test results 10

8. Other report sections 11

i

FOREWORD

This document is one of a range of guidance documents published (and in preparation) by theEnvironment Agency. Some of these are specific to the new contaminated land regime underPart IIA of the Environmental Protection Act 1990 (EPA 1990), and others are of a moregeneric nature and intended as guidance in a range of contexts. This document is the generictype and should cover any occasion where guidance on technical issues relating to siteinvestigation is needed in relation to land contamination. It is a supporting technicalguidance document within the framework of guidance being produced for landcontamination (see below and Figure 1). An outline of where the document fits within thishierarchy is provided below and in Figure 1.

The Model Procedures for the Management of Contaminated Land (2000 in preparation) havebeen developed for the Department of the Environment, Transport and the Regions, and theEnvironment Agency. These incorporate existing good technical practice, including the useof risk assessment and risk management techniques, into a systematic process for makingdecisions about and taking appropriate action to deal with contamination. The approachcontained in the Model Procedures is consistent with UK policy and legislative requirements.Therefore the model procedures set out a recommended good practice approach to managingland where contamination is, or may be, an issue.

The model procedures are part of a hierarchy of documents that provides a systematicapproach to managing ground and groundwater contamination. The guidance within thedocuments increases in complexity and technical detail within each tier of the hierarchy. Thefour main tiers are:

1 the process for managing ground and groundwater contamination describing theoverall approach and decision-making process within the UK legislative and policyframeworks;

2 primary model procedures that describe the procedural approach for the maintechnical activities involved in managing land contamination, namely:

• risk assessment;

• evaluation and selection of remedial measures;

• implementation of risk management measures;

3 secondary model procedures that describe the procedural approach for specificactivities that support, or are part of, the three main technical activities covered by theprimary procedures;

4. supporting technical guidance that describe technical aspects for specific activities(or sets of activities) that are part of the activities covered by the primary andsecondary procedures.

This document is supporting technical guidance that is expected to be relevant to all partiesinvolved in the assessment and management of contaminated sites, and in a variety of

ii

contexts. Users should establish a clear understanding of the purpose, context andrequirements of any site investigation before using this guidance.

Figure 1 - Where this document fits in the overall scope of guidance on land contamination

Activity Primary Model Procedures General technical guidance Specific technicalCLR11 (DETR in preparation) guidance areas

Desk Study

Preliminaryrisk

assessment

Siteinvestigation

Riskassessment

Volume MP1Risk assessment

Phase 1AHazard Identification

hase 1Bazard assessment

hase 2isk estimation and

valuation

Remediationolume MP2valuation and

Guidance on preliminary site inspection –DETR - CLR 2 (1994)Documentary research on industrial sites – DETR - CLR 3(1994)Prioritisation and categorisation procedure for sites which maybe contaminated – DETR - CLR 6 (1995)Guidance on the assessment and redevelopment of contaminatedland – DETR - ICRCL 59/83 (1983 shortly to be superseded)

DETR Contaminated Land Report (CLR) Series, Reports CLR 7-10, dealing with the programme of development of toxicologicaldata and guideline values for substances in soils (in preparation).Technical aspects of site investigation – Environment AgencyR&D Publication P5-065/TR(this document)Code of practice: The investigation of potentially contaminatedsites –British Standards Institute,BS10175, 2001Sampling strategies for contaminated land – DETR - CLR 4(1994)Secondary Model Procedure for the Development of AppropriateSoil Sampling Strategies for Land Contamination – EnvironmentAgency R&D Technical Report P5-066/TRSelection of tools for risk assessment of land – EnvironmentAgency R&D Technical ReportP260 (in preparation)Guidance on the protection of housing on contaminated land -Environment Agency R&D Publication 66 (2000)Communicating understanding of contaminated land risksSNIFFER Publication SR97(11)F (1999)

Industry profiles

Methane

Part IIA inspection strategies

Risk assessment:Human healthControlled watersEcologyBuildings

Part IIA Special Sites

Petroleum industry

Methane

Remedial treatment for contaminated land – CIRIA Reports SP101-112

Engineering options

PH

PRe

VE

i

selection of remedialmeasures

Volume MP3Implementation of riskmanagement measures

Survey of remedial techniques for land contamination used inEngland and Wales – Environment Agency R&D TechnicalReport 401 (2000)A review of full scale treatment technologies for the remediationof contaminated soil – RCEP (1996)Barriers, liners and cover systems for containment and control ofland contamination – CIRIA Report SP 124 (1996)Cost-benefit analysis in remediation of contaminated land –Environment Agency Technical Record No P316 (1999)

Treatment options

Monitoring and verification

Methane

R&D Technical Report P5-065/TR 1

1. INTRODUCTION

1.1 Intent and scope of the technical guidance document

This two-volume document provides technical guidance on the investigation of contaminatedsites for use in a wide variety of contexts, including:

• Part IIA of the EPA 1990;

• the planning regime;

• the Pollution Prevention and Control (PPC) regime; and

• purchase/sale of land.

1.2 Target audience

The technical guidance document is intended to provide guidance principally to EnvironmentAgency staff who are involved in the management of site investigation projects. The readershipis expected to be wide ranging, including:

• Environment Agency and local authority officers;

• those who fall under the regulatory regime and need to understand the EnvironmentAgency’s approach and requirements in relation to the investigation of contaminatedsites; and

• consultants and contractors engaged in site investigation projects.

The document is intended, primarily, to provide the target audience with the specialisttechnical information required when acting in a project management capacity dealing withinvestigation of contaminated sites. The variation in the level of existing expertise of thetarget audience has been recognised.

The document should also assist in the development of a nationally consistent approach to siteinvestigation projects in which the Environment Agency is involved by setting out what theEnvironment Agency believes to be the key issues relating to good site investigation practice.

In particular, the report serves as a supplement to, and should be used in conjunction with,other key guidance documents including:

• Model Procedures for the Management of Contaminated Land (2000 in preparation);

• Methodology for the derivation of remedial targets for soil and groundwater to protectwater resources. Environment Agency R&D Publication 20;


• Environment Agency National Sampling Procedures Manual – Quality ManagementSystem for Environmental Sampling (internal Environment Agency guidance);

• British Standard BS 10175:2001 Code of Practice for the Investigation of PotentiallyContaminated Sites;

• British Standard BS 5930:1999 Code of Practice for Site Investigations;

• Construction Industry Research and Information Association. Remedial treatment forcontaminated land. Special Publication SP101-112 (Volumes I to XII). CIRIA(London), 1996.

1.3 What is and is not included in the technical guidance document

There is a considerable depth and range of published literature produced in respect ofinvestigation of contaminated sites, both within the UK and internationally. This includes abroad range of technical guidance documents prepared by the Environment Agency for use inthe context of Part IIA, EPA 1990. The technical guidance document is not intended toduplicate the other relevant guidance thus, it cross-refers to this where appropriate. A list ofthe most relevant references and sources of further information is included in Volume II ofthis document.

The technical guidance document includes an overview of good practice, technicalinformation on the many individual investigation activities and provides a standard format fora site investigation report. The design/strategy aspects of site investigation are not dealt with inany detail within this document.

The completed document provides the benefit of collective past experiences combined with‘state of the art’ technical developments. It is relevant to the investigation of differentcontaminant types in ground and groundwater on all sites where contamination investigationis an issue.

This document addresses site investigation as required in Phase 1a/1b and 2 of the ModelProcedures, where the objectives of the investigation include:

• monitoring performance/effectiveness of remediation;

• verification testing; and

• site investigation to develop detailed remediation strategies or pilot treatments.

Further guidance can be obtained from:

• Guidance on Monitoring the Operations and Post-remediation Performance ofRemedial Treatments for Land Contamination (in preparation for the EnvironmentAgency);


• Guidance on the Assessment and Monitoring of Natural Attenuation of Contaminantsin Groundwater, Environment Agency R&D Publication 95, 2000;

• Verification of Remedial Techniques (in preparation for the Environment Agency).

1.4 How to use the supporting technical guidance document

The information is arranged and presented so that it can easily be drawn upon when usingother relevant guidance. It is split into two volumes:

• Volume I The main text with links to text supplements in Volume II;

• Volume II Text supplements that support Volume I (e.g. checklists, tables ofinformation, figures, photographs, technical information sheets, boxitems, flowcharts, a standard reporting format for site investigationsetc).

Volume I begins with an overview of good practice and further sections describe key issues inrelation to the principal site investigation activities. The different chapters cross-refer toothers within the technical guidance document where relevant. The format adopted aims toassist the reader in the practical use of the technical information by the strong links betweenthe text in Volume I and the supplementary material in Volume II.


2. GOOD PRACTICE OVERVIEW

2.1 - Investigation Planning – Major Issues

2.2 - Investigation Planning – Additional Issues

2.3 - Investigation Design Checklist

2.4 - Summary of Desk Study Information Sources

2.5 - Typical target Information available from a desk study

2.6 - Site Reconnaissance Information Checklist

2.7 - Example of a Site Visit Record Sheet

2.8 - Selection of Specialist Advisors and Contractors

2.9 - Definitions of Professional and Technical Staff

2.10 - Audit Trails and Record Keeping – Issues on which confidence may be required

2.11 - Further Reading


2.1 - Investigation planning – major issues

Issues Tick For more detail see

Objectives of the investigation Chapter 2

Applicability of investigation techniques? Chapter 4

Health and safety (investigation staff, other workers, neighbours)? Chapter 11

Environmental impacts (water pollution, dust, vapours, wastedisposal etc.)?

Chapter 12

Communications and emergency plans? Chapter 11

Sample type and quality requirements Chapter 5

Analytical requirements Chapter 8

Level of confidence required Chapters 2&8

Integration with other data needs (e.g. geotechnical) Chapter 10

Programme (How much time is needed? How much is available?) Chapter 4

Costs/budget available? Not covered

Access for investigation equipment? Chapter 4

Site ownership? Not covered

Consents/permits required? Chapter 13

Availability of water and power supplies? Not covered

Below or above ground services? Chapter 10

Presence of obstructions? Chapter 9

Site operational constraints? Chapter 13

2.2 - Investigation planning checklist – additional issues

Issues Tick For more detail see

Controlled waters (surface, groundwater, coastal) Chapter 12

Ecology Chapter 12

Archaeology Chapter 12

Topographic survey considerations Chapter 9

Audit trails and record keeping Chapter 2

Special reinstatement requirements Not covered


2.3 - Investigation design checklist

Issues Tick Comments

Exploratory investigations

number

type (boreholes, trial pits, groundwater wells etc.)

dimensions

locations

methods

Sample collection

media type (soils, liquids, gases)

numbers

size and type

locations

depths

storage and handling

In situ and on-site testing

media type

determinand/property

numbers

locations

duration

Laboratory testing

media type

sample preparation

determinand/property

analytical method

Health and Safety

procedures

protective equipment

Environmental protection

air quality

groundwater and surface waters

waste disposal

operating procedures/management systems

Source: CIRIA Special Publication 103


2.4 - Summary of desk study information sources

Historical and current land use information sources

• Site records (e.g. drawings, process descriptions, construction records, incident records);

• company records (e.g. archive materials, title deeds);

• maps (including historical OS);

• photographs (including historical aerial photographs);

• trade directories (including Kelly Street Directories);

• local historical information (e.g. published histories, museums, local history societies);

• site personnel (e.g. long serving and former employees);

• services drawing (e.g. for gas, electricity, water, telephone, cable, oil pipelines, sewers);

• records of authorised discharges to sewer/controlled waters;

• regulatory authorities (e.g. Environment Agency, SEPA, Local Authority, Petroleum Officer);

• technical literature (e.g. DoE Industry Profiles).

Geological/hydrogeological information sources

• geological maps, memoirs and reports;

• Hydrogeological maps and memoirs;

• source protection zones maps;

• mine plans and surveys;

• cave plans and surveys;

• borehole records;

• soil survey and geochemical atlas data;

• geological SSSI’s and RIGS (usually the County Museum);

• water abstraction records;

• meteorological information;

• tide tables.


2.5 - Typical target information available from a desk study

Item of information Examples

Site location Address, location plan (with scale and orientation) and OS grid reference

Site layout (as built both currentand historic)

Plant components, building structures, drainage systems, process areas,material storage areas, energy supply plant, effluent treatment plant, gastreatment plant, waste disposal plant and areas, maintenance facilities,laboratories, site services

Design/construction modifications Site layout, process train, materials

Nature/quantities of materialshandled on site

Feedstocks, intermediates, products, wastes, reagents, maintenancematerials

Nature of surrounding land use Residential, hospitals, schools, nurseries, commercial/industrial,agricultural/horticultural, surface water/groundwater resources, ecology,protected habitats, presence of public utilities, environmental consents(e.g. IPPC authorisations, waste management licences etc.)

Physical features Present and past topography, propensity for flooding

Previous history Industrial use, incidence of major accidents (fires, spillages etc.), previousmining activity, environmental enforcement records

Geology/hydrogeology/hydrology Solid and drift geology, mine workings, natural cavities, presence/status ofsurface and groundwater bodies and abstraction points, presence andsensitivity of surface waters, abstraction points and consented discharges

Ecological/geological status Presence of sensitive ecological systems on or near to the site

Presence of designated protected areas e.g. SSSI’s

Archaeological status Presence of sensitive or protected archaeological features

Source: CIRIA Special Publication 103


2.6 - Site reconnaissance information checklist

Features/characteristics/indicators Tick Comments

Current site uses

Previous site uses

Descriptions of buildings and ground cover

Location, type and condition of surface water/foul drainage

Name of adjacent roads/rivers/canals

Flow direction and appearance of streams and rivers, evidence ofgroundwater (e.g. seeps etc.)

Location and type of tanks, underground storage tanks, bunds, pits,walls, fences remaining buildings etc.

Evidence of previous investigations (boreholes, backfilled trial pits etc)

Level of ground in relation to adjacent areas and other parts of the site

Signs of ground settlement or subsidence

Geology/geomorphology/landscape/natural processes (landslips etc.)

Site access and any identifiable constraints for investigation of the site(including overhead services)

Visibly contaminated areas or malodorous areas

Signs of vegetation stress

Visible evidence of foundations

Present day potentially contaminative activities

Any known contamination incidents

Presence of underground services

Site security

Access for investigation plant and equipment

Adjacent land condition, uses, and nature of any businesses/activities

Other observations


2.7 - Example of a site visit record sheet

Site owner:Site name, address and telephone number:

Site size (ha)

Grid ref.: General site Use

Job reference Operational/disused/derelict

Visit by: Date and time:

Position (s): Visit number:

Visit accompanied by (include position): Weather:

Subject Information obtained

Follow-up action needed by (date) √√√√ when completed


2.8 - Selection of specialist advisors and contractors

• Demonstration of a breadth of suitable skills and experience;

• familiarity with published guidance and regulation;

• suitably qualified and experienced staff at a range of levels;

• adequate volume of resources;

• operation of a quality management system;

• operation of a comprehensive health and safety management system and a demonstrable track record;

• independent accreditation for testing procedures (contractors);

• availability of adequate Professional Indemnity Insurance, Public Liability Insurance and otherinsurances.

2.9 - Definitions of professional and technical staff

Principal Scientist / Engineer A graduate scientist / engineer with at least 10 years relevantexperience since graduation and with chartered status from a relevantprofessional body.

Senior Scientist / Engineer A graduate scientist / engineer with at least 5 years of relevantexperience since graduation and preferably chartered status from arelevant professional body.

Scientist / Engineer A graduate scientist / engineer with at least 3 years of relevantexperience since graduation.

Assistant Scientist / Engineer A graduate scientist / engineer who is receiving formal training andguidance in the practice of geoenvironmental matters and issupervised by one or more of the above ranked professionals.

Technician An individual with specific training and experience and proceduresfor sampling, field testing and monitoring.


2.10 - Audit trails and record keeping - issues on which confidence may be required

Issues Possible requirementWhether samples were taken from the specified site Ensure appropriate supervision during the sampling

exercise with logging and photographsThe precise locations from which samples weretaken

Survey locations and provide the uncertaintyassociated with survey of the sampling location.Consider whether sampling uncertainty needs to beaddressed explicitly by repeat sampling to allowstatistical analysis

Whether samples were properly and unambiguouslylabelled

QC methodology for the sampling procedures toinclude labelling

Whether samples could have been contaminated onsite, during transport or in the laboratory

Employ trip blanks and field blanks. Employ chainof custody so that samples are signed for at eachstage in the chain. Employ pre-selected courier orlaboratory’s own courier service

Whether samples have been stored at an appropriatetemperature after collection and during transit

Arrange for laboratory to measure temperature onarrival as appropriate. Provide refrigeratedtransport.

Whether all aspects of the sample preservation,preparation and analysis are satisfactory

Use laboratory with accredited proceduresapplicable to the tests being carried out and thatappropriate preservatives are provided for therequired test. Ensure that QC data (control charts,etc) are reported and examine QC data provided.Ensure that laboratory reports include details ofwhen samples were received and when analysed.



British Standard Institution (London) (1999) Code of Practice for Site Investigations. British StandardBS5930.

Cairney, T.C. (1995) Risk of attack on construction materials. The Re-use of Contaminated Land. Wiley(Chichester).

Charles, J.A. (1993) Building on fill: geotechnical aspects. BRE Report BR230 (out of print).

Construction Industry Research and Information Association. Remedial treatment for contaminated land.Volumes 1 to 12. Special Publications SP101-112. CIRIA (London).

Construction Industry Research and Information Association (1995). Methane investigation strategies. Report150. CIRIA (London).

Construction Industry Research and Information Association (1995). Risk assessment for methane and othergases from the ground. Report 152. CIRIA (London).

Construction Industry Research and Information Association (1993). The measurement of methane and othergases from the ground. Report 131. CIRIA (London).

Construction Industry Research and Information Association (1993). Methane investigation strategies. Areport in CIRIA’s research programme methane and associated hazards to construction. Funder report CP/14.CIRIA (London).

Construction Industry Research and Information Association (1995). Interpreting measurements of gas in theground. Report 151. CIRIA (London).

Construction of new buildings on gas-contaminated land (1991) BRE Report BR212.

Crowhurst, D., Beever, P.F. (1987) Fire and Explosion Hazards Associated with the Redevelopment ofContaminated Land. Fire Research Station. BRE Information Paper IP2/87.

Department of the Environment (1990) Planning Policy Guidance: Development on Unstable Land(PPG14).

Department of the Environment (1991) Policy Appraisal and the Environment: A Guide for GovernmentDepartments. HMSO.

Department of the Environment (1994) CLR 1. A framework for assessing the impact of contaminated landon groundwater and surface water. Volumes 1 and 2.

Department of the Environment (1994) CLR 2. Guidance on preliminary site inspection of contaminatedland. Report by Applied Environmental Research Centre Ltd. Volumes 1 and 2.

Department of the Environment (1994) CLR 3. Documentary research on industrial sites. Report by RPSGroup.

Department of the Environment (1994) CLR 4. Sampling strategies for contaminated land. Report by TheCentre for Research into the Built Environment, The Nottingham Trent University.

Department of the Environment (1994) CLR 5. Information systems for land contamination. Report byMeta Generics Ltd.


Department of the Environment (1995) CLR 6. Prioritisation and categorisation procedure for sites whichmay be contaminated. Report by M J Carter Associates.

Department of the Environment, Transport and the Regions. CLR 11. Handbook of Model Procedures for theManagement of Contaminated Land. Contaminated Land Research Report (in preparation).

Department of the Environment (1997) CLR 12. A quality approach for contaminated land consultancy.Report by the Environmental Industries Commission in association with the Laboratory of the GovernmentChemist.

Department of the Environment (1994) Planning Policy Guidance: Planning and Pollution Control(PPG23).

Department of the Environment (1995) Workshop 1. Professional standards, April 1994 (superseded by CLR12 – see below).

Department of the Environment (1995) Guide to Risk Assessment and Risk Management for EnvironmentalProtection.

Department of the Environment, Transport and the Regions (1998) CLR Research Report. Research into theImpact of Contaminated Land on the Water Environment. Prepared by Sir William Halcrow & PartnersLtd.

Department of the Environment, Transport and the Regions (1998) CLR Research Report. Modelling theImpact of Contaminated Land on Water Quality using the MIKE SHE model. Prepared by WS AtkinsConsultants Ltd.

Department of the Environment, Transport and the Regions (1998) CLR Research Report. Internationalreview of the state of the art in Contaminated Land Treatment Technology Research and a Frameworkfor Treatment Process Technology Research in the UK. Prepared by The Centre for Research into the BuiltEnvironment, The Nottingham Trent University.

Department of the Environment, Transport and the Regions (1998) CLR Research Report. ActiveContainment: Combined Treatment and Containment Systems. Prepared by Golder Associates (UK) Ltd.

Department of the Environment (1995) Workshop 3. Risk assessment and the use of guidelines, July 1994.

Department of the Environment (1996) Industry profile. Profile of miscellaneous industries, incorporatingcharcoal works, dry-cleaners, fibreglass resins, glass, photographic processing, printing and bookbindingworks.

Department of the Environment (1996) Industry profile. Waste recycling, treatment and disposal sites:solvent recovery works.

Department of the Environment (1996) Industry profile. Waste recycling, treatment and disposal sites:landfills and other waste treatment or waste disposal sites.

Department of the Environment (1996) Industry profile. Waste recycling, treatment and disposal sites:hazardous waste treatment plants.

Department of the Environment (1996) Industry profile. Waste recycling, treatment and disposal sites: drumand tank cleaning and recycling plants.

Department of the Environment (1995) Industry profile. Timber products manufacturing works.


Department of the Environment (1996) Industry profile. Textile works and dye works.

Department of the Environment (1996) Industry profile. Road vehicle fuelling, service and repair: transportand haulage centres.

Department of the Environment (1996) Industry profile. Road vehicle fuelling, service and repair: garagesand filling stations.

Department of the Environment (1996) Industry profile. Pulp and paper manufacturing works.

Department of the Environment (1995) Industry profile. Oil refineries and bulk storage of crude oil andpetroleum products.

Department of the Environment (1996) Industry profile. Metal manufacturing, refining and finishing works:non-ferrous metal works (excluding lead works).

Department of the Environment (1995) Industry profile. Engineering works: vehicle manufacturing works.

Department of the Environment (1996) Industry profile. Engineering works: electrical and electronicequipment manufacturing works (including works manufacturing equipment containing PCBs).

Department of the Environment (1995) Industry profile. Engineering works: aircraft manufacturing works.

Department of the Environment (1995) Industry profile. Dockyards and dockland.

Department of the Environment (1995) Industry profile. Timber products manufacturing works.

Department of the Environment (1996) Industry profile. Chemical works: mastics, sealants, adhesives androofing felt manufacturing works.

Department of the Environment (1995) Industry profile. Chemical works: linoleum, vinyl and bitumen-based floor covering manufacturing works.

Department of the Environment (1996) Industry profile. Chemical works: inorganic chemicalsmanufacturing works.

Department of the Environment (1996) Industry profile. Chemical works: fertiliser manufacturing works.

Department of the Environment (1995) Industry profile. Chemical works: disinfectants manufacturingworks.

Department of the Environment (1995) Industry profile. Chemical works: cosmetics and toiletriesmanufacturing works.

Department of the Environment (1995) Industry profile. Chemical works: coatings (paints and printing inks)manufacturing works.

Department of the Environment (1996) Industry profile. Ceramics, cement and asphalt manufacturingworks.

Department of the Environment (1995) Industry profile. Airports.

Department of the Environment (1995) Industry profile. Timber treatment works.


Department of the Environment (1995) Industry profile. Sewage works and sewage farms.

Department of the Environment (1995) Industry profile. Power stations (excluding nuclear power stations).

Department of the Environment (1995) Industry profile. Metal manufacturing, refining and finishing works:iron and steelworks.

Department of the Environment (1995) Industry profile. Metal manufacturing, refining and finishing works:precious metal recovery works.

Department of the Environment (1995) Industry profile. Metal manufacturing, refining and finishing works:electroplating and other metal finishing works.

Department of the Environment (1995) Industry profile. Engineering works: shipbuilding, repair andshipbreaking (including naval shipyards).

Department of the Environment (1995) Industry profile. Chemical works: soap and detergentmanufacturing works.

Department of the Environment (1995) Industry profile. Chemical works: organic chemicals manufacturingworks.

Department of the Environment (1995) Industry profile. Chemical works: pesticides manufacturing works.

Department of the Environment (1995) Industry profile. Engineering works: railway engineering works.

Department of the Environment (1995) Industry profile. Railway land.

Department of the Environment (1995) Industry profile. Animal and animal products processing works.

Department of the Environment (1995) Industry profile. Chemical works: explosives, propellants andpyrotechnics.

Department of the Environment (1995) Industry profile. Chemical works: pharmaceuticals manufacturingworks.

Department of the Environment (1995) Industry profile. Chemical works: fine chemicals manufacturingworks.

Department of the Environment (1995) Industry profile. Chemical works: rubber processing works(including works manufacturing tyres or other rubber products).

Department of the Environment (1995) Industry profile. Engineering works: mechanical engineering andordnance works.

Department of the Environment (1995) Industry profile. Gas works, coke works and other coal carbonisationplants.

Department of the Environment (1995) Industry profile. Asbestos manufacturing works.

Department of the Environment (1995) Industry profile. Metal manufacturing, refining and finishing works:lead works.

Department of the Environment (1995) Industry profile. Waste recycling, treatment and disposal sites: metal


recycling sites.

Department of the Environment, Transport and the Regions. Potential Contaminants for the Assessment ofLand. Report by Consultants in Environmental Science (in preparation).

Department of the Environment, Transport and the Regions SP99. Guidance on the sale and transfer of landwhich may be affected by contamination. Report by Parkman Environment, Andrew Bryce and Co. andClifford Chance (in preparation).

Department of the Environment, Transport and the Regions/Environment Agency/NHBC. Guidance for theDevelopment of Housing on Land affected by Contamination. R&D Publication 66 2000.

Department of the Environment. Royal Commission on Environmental Pollution (Nineteenth Report),Sustainable use of soil. HMSO.

Environment Agency (2000 in preparation) Model Procedures for the Management of Contaminated Land.

Environment Agency. Methodology for the derivation of remedial targets for soil and groundwater toprotect water resources. Environment Agency R&D Publication 20;

Environment Agency. National Sampling Procedures Manual – Quality Management System forEnvironmental Sampling (internal Environment Agency guidance);

Garston, CRC (1998) Contaminated Land: a review of research at BRE. BRE Report reference numberBR346. Published only on the CD-ROM BRE Reports on CD, number 10 (1998).

Harris, M.R. and Herbert, S.M. (1994) Contaminated land: investigation, assessment and remediation. ICEDesign Guide, Thomas Telford (London).

Health and Safety Executive (1991) Protection of workers and the general public during development ofcontaminated land. HS(G)66.

ICRCL 59.83. Guidance on the assessment and redevelopment of contaminated land. 2nd Edition, July1987.

ISO FDIS 10381-1 Soil quality Part 1 Guidance on the design of sampling programmes.

ISO FDIS 10381-2 Soil quality Part 2 Guidance on sampling techniques.

ISO FDIS 10381-3 Soil quality Part 3 Guidance on safety.

ISO FDIS 10381-4 Soil quality Part 5 Guidance on the procedure for the investigation of soil contaminationof urban and industrial sites.

Paul, V. (1995) Bibliography of Case Studies on Contaminated Land: investigation, remediation andredevelopment. BRE Report BR291.

British Standard Institution, BS 10175:2001. Code of Practice for the Investigation of PotentiallyContaminated Sites.

‘Risks of Contaminated Land to Buildings, Building Materials and Services’ a literature review. Report byBRE for the Environment Agency, R&D Technical Report P331, 2000.

Scottish Enterprise. How to investigate contaminated land. SE (Glasgow), revised.


Uff J F and Clayton C R I. Role and responsibility in site investigation. Special Publication 73. CIRIA, 1991

Warren Spring Laboratory (1994) An evaluation of the constraints to effective contaminated landremediation. Report LR 1003.


3. SITE CHARACTERISATION RECORDS AND DATAMANAGEMENT

3.1 - Example of a daily site diary

3.2 - Further reading


3.1 - Example of a daily site diary

Site owner:Site name, address and telephone number:

Grid ref.:

Contract details

Job reference Consultant:

Principal contractor and sub-contractor(s):

Recorded by: Date and time:

Position: Visit number:

Weather: Activities being undertaken on site:

Plant on site and condition: Personnel on site and contact details:

Time Activity

Additional comments

Follow-up action needed by (date) √√√√ when completed



Association of Geotechnical and Geoenvironmental Specialists. Electronic Transfer of Geotechnical andGeoenvironmental Data (3rd Edition) 1999.

British Geological Society and Environment Agency 2000. Some guidance on the use of digitalenvironmental data. BGS Technical Report WE/99/14, NGWCLC Technical report NC/06/32.

British Standard Institution (London) (1999) Code of Practice for Site Investigations. British StandardBS5930.

Burrough and McDonnell (1998) Principles of geographic information systems, Oxford University ISBN 0 19823366 3.


Environment Agency R&D Technical Report P241, 1999, Recommendations for the Processing andPresentation of Groundwater Quality Data.

Gilbert, R.O. (1987) Statistical Methods for Environmental Pollution Monitoring. John Wiley & Sons.



4. INTRUSIVE AND NON-INTRUSIVE INVESTIGATIONMETHODS

4.1 - Investigation method summary sheets

4.2 - Selected photographs of investigation methods

4.3 - Choosing an intrusive investigation method

4.4 - Worked example

4.5 - Site Investigation Preparation and Implementation Checklist



4.1 - Investigation method summary sheets

Summary sheets are included for the following intrusive and non-intrusive methods.

Intrusive methods

• trial pits (“trial holes”, “trial trenches”, “test pits” and “test holes” - hand dug andmechanically excavated)

• auger drilling (CFA/HSA);

• cable percussion drilling ( “shell and auger”)

• rotary coring

• rotary drilling ( “rock roller”/“tricone”)

• down the hole hammer drilling (DTH, DTHH and rotary percussive)

• window sampling

• probing ( e.g. “geoprobe”)

• hand augering and associated methods

In preparing the summary sheets for intrusive methods, the contribution of Chris Jeffries ofEnvironmental Sampling Ltd is gratefully acknowledged.

Non-intrusive methods

• seismic

• gravity

• electrical

• electromagnetic

• magnetic

• ground penetrating radar (GPR)

In preparing the summary sheets for non-intrusive methods, the contribution of John Arthur ofTop-hole Site Studies Ltd is gratefully acknowledged.


INVESTIGATION METHOD SUMMARY SHEET – TRIAL PITS

Related techniques and names: trial holes/trial trenches/test pits/test holes

BASIC DESCRIPTION OF METHOD

Trial pits are exploratory holes excavated into the ground by hand or by mechanical excavator. Compared toboreholes, trial pits allow faster inspection of a larger proportion of the groundmass and are a means of obtaininglarger quantities of soil samples. Trial pits can be used to obtain groundwater samples if conditions are such thatsufficient can collect in the base of the pit in the time available, without risk of ground instability and if samplesobtained in this way are technically suitable for the purposes of the investigation. Trial pits can also provide ameans of installing rudimentary gas monitoring standpipes to supplement ones constructed in boreholes.

Trial pits can be excavated to a variety of sizes to suit the requirements of the investigation e.g. narrow and verydeep to investigate within a landfill or a series of shallow and long “trial trenches” to establish the extent of aninfilled area. However the typical size of a trial pit is around 2 m long by 0.5 m – 1m wide by up to 5 deep. Trialpits can be hand dug to 1.2 m, but the usual method is to use hired mechanical plant with a skilled operator. Theplant most commonly used is a wheeled backhoe loader (using the backactor arm) which is frequently referred toas a “JCB”, irrespective of the actual make. With a conventional digging arm these can achieve depths of around3.5 m and with an extendable arm they can achieve depths around 5 m. Other types of excavators can be used tosuit certain situations. For example, a slew boom hydraulic excavator may gain access to areas too constrainedfor a backhoe loader. Where there is a high risk that the ground surface will cause puncture to vehicle tyres (forwhich the hirer pays) then tracked, rather than wheeled, excavators may be more suitable. Tracked vehicles canalso be useful where it is desirable to spread weight on soft ground. However, these vehicles have to be broughtto site on a low-loader. Very large machines can be hired to excavate pits deeper than 5 m. The condition ofmachines varies considerably and old machines and those that have been used for more than an average amountof breaker work (for breaking through concrete and other hard layers) may be considerably slower and risk ofbreak down is greatly increased. This can seriously impact on a site investigation programme.

The width of a mechanically excavated trial pit is dictated by the size of excavator used. Wider buckets (around 1m) allow inspection of a larger proportion of the ground but generate very large volumes of spoil and, whereconcrete is present on the ground surface, require more time to be spent breaking through. Narrow buckets(around 0.5 m) create less ground disturbance but it can be difficult to see the pit walls at depths below around 4m. A bucket size between these two extremes is usually appropriate. Breaker units vary in size and, particularly,in condition. It is usual to specify precise requirements to the plant hire company.

The operating arm and connecting parts of all excavators need considerable lubrication during the working day.An awareness of this on the part of the supervising scientist/engineer is necessary, particularly during samplingactivities. In addition, it is common practice for finished tubes of lubricant to be discarded on the ground or eveninto trial pits before backfilling. The unacceptability of this may need to be stressed to the excavator driver at theoutset of the investigation.

Sequence of events:

• an appropriate location (clear of underground services etc) for the trial pit is chosen and a “before”photograph may be taken. It may be necessary to protect the ground surface from contaminated arisingsusing plastic sheeting, wooden boards etc. and to use sand-bags or other methods to contain water as the pitis dug;

• the excavator driver manoeuvres the excavator into a suitable position for the trial pit location, taking intoaccount factors such as the position of the sun/other bright lights (good visibility is essential) and winddirection (in relation to vehicle exhaust fumes, ground gases, odours etc). Any surface concrete/other hardcover is broken out to a suitable size and the excavator changes from breaker to bucket. As the trial pit isdug, the scientist/engineer directs the speed/depth of excavation and also maintains a constant look out foranything that may affect safety of the trial pitting exercise. Under no circumstances should anyone enter atrial pit;

• as the trial pit progresses, the spoil is segregated in such a way that it can be used to backfill the pit inroughly the same order that it was removed. Photographs, depth measurements and samples are taken asrequired (during this time the excavator stands still with the bucket on the ground i.e. hydraulics at rest).Anyone approaching a trial pit should do so on the short side opposite the excavator and all the time with anawareness of the pit’s stability and the surrounding ground conditions. (see section below on practical safetyand environmental protection measures about safe distances for placement of excavated spoil, safe workingnear trial pits etc.).

• once the desired depth or limit of the machine is reached, final measurements and photographs are taken (thedriver should not be asked to hold the photograph identification board). The trial pit is then backfilled usingthe original spoil which is emplaced in roughly the same order to the original (alternatively, clean sand/gravelmay be used). A gas monitoring standpipe may be installed in the trial pit. When backfilling is completed, an“after” photograph may be taken;

• re-instatement works that are needed are carried out (arrangements for this should be made before startingthe investigation). Irrespective of whether formal re-instatement works are to be carried out, it is importantthat the backfilled trial pit and surrounding affected area are left in a safe condition. Open trial pits shouldNEVER be left unattended unless securely fenced off (safety issues are covered below).


KEY APPLICATIONS AND LIMITATIONS

Applications

Trial pits can be excavated in all but the densest ground conditions.

A large proportion of the groundmass can be inspected and large quantities of soil for samples can be taken.

Allows flexibility during investigation as trial pits can often be moved slightly, rather than re-started, if obstructionsare encountered.

Rudimentary gas monitoring probes can be installed.

Limitations

Ground instability can cause pit walls to collapse repeatedly so that the excavator ends up merely digging thismaterial out rather than deepening the pit. This occurs frequently with soil types such as ashy granular madeground and loose sands/gravels. Groundwater flowing rapidly into the pit through the sides of the pit canexacerbate unstable conditions.

Compacted or hard layers can be difficult to dig through and it may be necessary for a breaker unit to be usedintermittently.

All trial pits cause considerable ground disturbance and it can be difficult to restore the surface completely.Depending on the make-up of the groundmass, a slight mounding or dip in the surface will remain. On manyderelict or redevelopment sites this will not matter but on operational sites this may be unacceptable and formalre-instatement works may be required. These can be expensive and may require the general area to be fenced offfor the surface to settle first. In some parts of operational sites, the disturbance caused by trial pits is whollyunacceptable e.g. access roads, inside buildings, airport runways, close to rail lines, close to pipe/cable runs.

KEY COST FACTORS AND PERSONNEL REQUIREMENTS

Key cost factors

• Nature of the ground conditions;

• depth of excavation needed;

• surface cover conditions –the hourly hire rate is greater for an excavator with a breaker unit than for onewithout and breaking through concrete is a time consuming activity;

• re-instatement requirements;

• sampling rate;

• need for additional Health & Safety measures and working methods to address hazardous contaminants.

Personnel requirements

Trial pitting should be carried out only by an experienced scientist/engineer, working in partnership with anexperienced excavator operator. On average, around five trial pits to 5 m per day (no surface concrete) should beachieved per trial pitting team although the precise number will vary according to the factors listed in the section“key cost factors”.

Excavators with skilled operators are widely available but the experience of the driver needs to be assured prior tohire to ensure the success of the trial pitting exercise.

KEY OPERATIONAL PARAMETERS

• Access to the site and within the site (for a backhoe loader allow 2.7 m width for access through gates andmore for larger machines – check with the plant hire company);

• overhead clearance (allow 6.5 m for a backhoe loader and more for larger machines);

• available working area (allow an area of minimum 15 m X 15 m for a backhoe loader and more for largermachines);

• availability of washdown facilities, with power and freshwater supply, for the excavator bucket that can beaccessed by the excavator;

• ability of ground to support weight of plant (a backhoe loader weighs around 9 tonnes while larger machinescan weigh 45 tonnes).


PRACTICAL SAFETY AND ENVIRONMENTAL PROTECTON ISSUES

The usual approach to assessing and managing the risks presented by working on contaminated sites should beadopted. In addition, the following should be noted:

A trial pit should not be left unattended at any time during excavation. If it is necessary to leave a trial pit open,secure fencing and warning signs must be used to encircle the hole, the spoil stockpiles and a suitable marginaround this that could be affected if the pit walls collapse.

The utmost care should be taken by personnel working alongside trial pits. The risks presented by entering trialpits are very real. Bearing in mind the weight of a relatively small volume of soil, the forces operating on the sidesof a gradually deepening pit as spoil is piled above are immense. Collapse, particularly on the long side of arectangular pit, can be sudden and catastrophic. As a rule of thumb, if an average table were piled high with soil,this amount would weigh around two tonnes and a relatively small volume of soil can quickly crush and asphyxiatea person.

To reduce the risk of collapse, spoil should be placed away from the side of a trial pit at a distance equivalent tothe trial pit depth. When trial pitting close to buildings or on sloping sites, account will need to be taken of theadditional loading to the ground applied by the building/uphill side of the pit. Whilst the short ends of a trial pitare usually more stable than the long sides, the individual digging styles of excavator drivers vary and some willundercut the short sides. Any unsupported excavation will be safe without support only if its sides are batteredback sufficiently, or if it is in sound rock. The HSE document listed below in “Selected Further Reading” providestypical safe slope angles for battering back the sides of an excavation and also provides guidance on steppingexcavation sides as an alternative. However, in practice neither of these techniques are likely to have practicalapplication for trial pitting exercises and an awareness of the risks and extreme caution will be needed by all onsite.

Legislation used to prohibit anyone entering an unshored trial pit greater than 1.2 m depth. This prohibition waswithdrawn by the Construction Health and Safety and Welfare Regulations (1996). These stated that there was nodepth limit for entry by personnel but that the safety of an excavation, whatever its depth, should be judgedindividually before entry be permitted. Some trial pits shallower than 1.2 m are unstable, particularly whenexcavated into made ground. In addition the presence of contaminants will make many stable pits unsafe forentry. Thus, it is appropriate that a total ban on personnel entry into trial pits is imposed for groundcontamination investigations – whatever their depth. If someone falls into a trial pit, the emergency servicesshould be called.

If unmanageable materials (e.g. unexpected friable asbestos) or unexpected conditions (e.g. groundgases/odours/dust) are encountered the pit should be aborted and backfilled and the method of investigation andhealth and safety arrangements re-appraised. If large amounts of contaminated materials or dusty/odorousconditions etc are present, trial pits may be an inappropriate method for investigation.

During backfilling, any gases/vapours can be forced out of the pit. Thus, supervising and other personnel shouldstand well clear of the backfilling exercise.

Trial pits should never be used to penetrate through a low permeability horizon into an aquifer. Where a lowpermeability horizon separates contaminated ground and an underlying aquifer, trial pits should be executedextremely carefully to avoid penetration into the low permeability horizon: if it is reached, the trial pit should beterminated immediately.

Great care needs to be taken when manoeuvring excavators near overhead services, site structures etc and whenexcavating in the vicinity of services, near walls, fences, buildings, archaeological remains etc. to avoid damage.If structures are close by, this can occur some time later if the trial pit is not backfilled properly and settlementoccurs.

Similarly, care needs to be taken to avoid damage to flora and fauna, especially protected species. Considerableharm can be done to trees if knocked by an excavator or if roots are severed, even if damage is not readily visibleat the time.

After backfilling, the pit and affected ground around must be left safe e.g. sloppy pits will need to be fenced orconed off for an appropriate period of time, any broken reinforcing bars need to be bent down and any exposedcontaminated material covered with clean arisings. Surplus arisings need to be properly managed. It may benecessary to make a return trip to site to carry out re-instatement works.

SELECTED FURTHER READING

British Standard Institution, BS10175:2001. Code of Practice forthe Investigation of PotentiallyContaminated Sites.

HSE (1999) Health and Safety inExcavations – Be Safe and ShoreHS(G)185

“Guidance Document for CombinedGeoenvironmental and GeotechnicalInvestigation” AGS (2000)


INVESTIGATION METHOD SUMMARY SHEET –

AUGER DRILLING

Related techniques and names: Solid stem auger, solid stem continuous flight auger (CFA)hollow stem auger (HSA).


Auger drilling utilises a helical (spiral) tool to convey material to the ground surface. An auger is essentially aconveyor that has a drill head and cutting bit which shears the formation and conveys the cut material upwardsalong the helix. It is a purely mechanical method that does not require the use of circulation/flush fluids.

Solid stem continuous flight auger (CFA) and hollow stem auger (HSA) are the two main methods of auger drilling.An auger rig is usually capable of operating both types of augers. CFA and HSA methods, equipment, personneletc. are similar in many ways with the main difference being their applicability to ground contaminationinvestigation work and different geological conditions. Essentially, CFA is suited to consolidated conditions onlyand where it is not necessary to take soil samples from precise depths. CFA may be useful where it is necessaryto drill quickly and where cross-contamination is not an issue (e.g. where drilling within only one horizon).Otherwise, where it is necessary to avoid connecting two aquifers, careful sealing off of different horizons(described later in this section) would be needed. HSA is suited to both consolidated and unconsolidated soils, hastechnical advantages in collecting samples and accessing ground at specific depths with the risk of crosscontamination minimised. Neither method is suitable for highly consolidated rocks.

Rigs used on environmental projects tend to have been built specifically for environmental work and hence arerelatively modern, compact purpose built machines. Many of these are versatile assemblies e.g. able to coresurface concrete and also able to deploy other drilling techniques such as rotary and window sampling.

The augers of CFA have solid stems with diameters generally ranging between 100 mm and 250 mm (measuredacross the full flight). Each section is generally 1.0 m or 1.5 m in length. A cutting head slightly larger than theflight is fitted to the leading section and, as the bit rotates, the cuttings are brought to the surface with the flightsacting as a screw conveyor. A conventional CFA is known by the nominal diameter of the drill head which isapproximately 10 % greater than the actual diameter of the following augers and it is this diameter whichdetermines the diameter of the borehole.

The augers of HSA, as their name suggests, are hollow and the flights are built up around a tubular central shaftthat is unobstructed from the ground surface to the lead bit. A removable central “pilot bit” is fitted within theauger head and, when removed, can be replaced with a sampling tool that samples in advance of the cutter head.In such instances, the HSA sections act as temporary casings while cores or other samples are obtained. Inaddition, once the desired depth is achieved, the augers continue to act as casings as the groundwater/gasmonitoring installation is constructed through the hollow stem. Unlike with CFA, the augers of HSA are specifiedby the inside diameter of the hollow stem, not by the hole size drilled (although it is possible to specify the size ofthe hole required too). This can be a source of much confusion and it is necessary to be clear about the preciserequirements for borehole diameter and installation diameter in dialogue with the drilling contractor.

When drilling to avoid connecting two aquifers, the upper layer needs to be sealed off using a sufficiently largediameter system to allow continued drilling through the first drill system. This can be achieved with CFA, or HSA,or a combination of the two as appropriate for the specific conditions. For example, in stable conditions in bothaquifers it would be best to CFA to the top of the natural seal, withdraw, place and rehydrate a bentonite seal,position temporary casing and then continue with a narrower diameter CFA to the lower stratum. Where upperconditions are unconsolidated (unstable) and lower conditions are stable however, it would be best to HSA at largediameter to the top of the natural seal, pull back slightly, install a bentonite seal and, after this has rehydrated re-drill slightly. Once this has been done it will be possible to continue drilling using a smaller diameter CFA withoutgroundwater entering from the upper formation.

Down-hole geophysical logging can be used to examine the subsurface properties of both the groundwater and therock, extending a few or tens of centimetres into the rock matrix. A sonde (instrumental probe) is lowered intothe borehole at a known velocity to produce a log. The following are the down-hole logging techniques mostusually carried out. Some of these (marked with an asterisk) can be used in an installed borehole while others willbe most successful in a clean hole where the formation is unobstructed:

• *temperature and conductivity – to examine changes in the groundwater composition with depth and toidentify flow horizons;

• calliper (to determine the borehole diameter and the identify presence of fractures);• resistivity (to measure the resistance of the groundwater and the rock);• *natural gamma radiation (to determine the radioactive properties of the rock);• *neutron (to measure the porosity of the rock and the properties of the groundwater);• *gamma – gamma radiation (to determine the bulk density of the rock).

If down-hole logging is required, the specific technical requirements of the method (e.g. borehole diameter,casings etc) should be checked with a geophysics specialist before drilling work is commissioned.


Sequence of events:

• an appropriate location for the borehole is chosen and a “before” photograph may be taken. Any surfaceconcrete is broken or cored through. It may be necessary to protect the ground surface from contaminatedarisings using plastic sheeting, wooden boards etc. and to use sand-bags or other methods to contain water asthe borehole is drilled and arisings extracted;

• the general requirements for drilling, sampling, in situ tests and the design of the groundwater/gas monitoringinstallation (if needed) etc. are confirmed before the borehole is started. It is usually desirable, however forsome flexibility to be maintained as the borehole is drilled and the conditions emerge;

• the rig is positioned over the borehole location by the Drill Supervisor and the appropriate type of lead augeris fitted and the borehole is started. As the hole deepens and the auger spirals into the ground, the materialbeing conveyed up the auger helix emerges at the ground surface and is moved clear of the top auger.Depending on the specific requirements of the project and whether CFA or HSA is the method used, samplesof this conveyed material may be taken although this only permits an approximate depth to be ascribed to thesample. Alternatively (and only applicable to HSA), a sampler may be inserted down through the hollow stemto retrieve a soil sample from a specific depth;

• as the borehole develops the scientist/engineer liaises with the drilling crew on precise sampling andgroundwater measurement requirements, but stands a safe distance back from and avoids obstructing theactual drilling process. Anyone approaching the rig, aside from the drilling crew, should do so only afterindicating to the Drilling Supervisor of this intention as it may be necessary to stop the drilling mechanism.When approaching the rig, this must be done with an awareness of the safety of the rig itself, the equipmentin the vicinity and the condition of the ground surface. All personnel maintain a look out for anything thatmay affect the safety of the drilling exercise;

• where there is need to construct the borehole in such a way as to protect, for example, an underlying aquiferthe precise design is refined to reflect the emerging conditions;

• as the borehole progresses, any retrieved spoil that is not required for samples is either stockpiled temporarilyclose to the borehole or placed directly into bags. Whichever method is chosen, the arisings are stored insuch a way that any that are suitable can be used as backfill material at the appropriate time, while those thatare not may be disposed of appropriately;

• once the desired depth is reached, final measurements of the depth of the hole and groundwater level aretaken. If a groundwater/gas monitoring installation is required, this is constructed carefully by the drillingcrew and the top of the borehole fitted with an appropriate cover;

• Re-instatement works that are needed are carried out (arrangements for this should be made before startingthe investigation). Irrespective of whether formal re-instatement works are to be carried out, it is importantthat the borehole and surrounding area are left in a safe condition. Open boreholes and drilling equipmentshould not be left unattended unless securely roped, coned or fenced off (safety issues are covered below).


Applications

Auger drilling is suitable for all but the most consolidated ground conditions. CFA, in particular, is a fast method ofdrilling suitable for self supporting conditions (particularly where there is a high clay content). HSA is suitable forboth consolidated and unconsolidated conditions as the flights are self-casing.

Auger drilling has a high success rate in landfill sites.

By using core barrels down through the centre of the hollow stem, it is possible to measure, precisely, the depthfrom which soil samples have been obtained. With all techniques, quantities of soil that are usually adequate formost investigations of contaminated sites can be taken.

Robust groundwater and gas monitoring installations can be established.

Augering is a relatively clean drilling process as no additives (water, foam etc.) are required to aid drilling orflushing purposes. As such, this system is particularly favoured for environmental projects.

Limitations

It can be time-consuming to re-locate boreholes that have hit shallow obstructions.

Water may need to be added to the borehole to assist in the withdrawal of the lead auger when boring is complete.this is particularly the case in sandy conditions as sand can lodge and prevent the lead auger being withdrawn.

If samples of conveyed soil are taken from the top of the auger flights, it is difficult to be sure of which depth thishas come from and considerable reliance has to be placed on the skill of the Drill Supervisor. Similarly it is notalways possible to be precise about the intersection between different geological strata.



Key cost factors

• nature of the ground conditions and depth of boring needed;

• surface cover/re-instatement requirements;

• sampling and In situ testing requirements;

• spoil storage/disposal.


There are a small number of specialist environmental drilling companies that have developed HSA/CFA rigs for usein ground contamination investigation.

On average, around 30 m to 50 m per day (no surface concrete) should be achieved by CFA per drilling rig/crewalthough the precise meterage will vary according to the factors listed in the section “key cost factors”. Onaverage, around 15 m to 20 m per day (no surface concrete) should be achieved by HSA per drilling rig/crew and,again, the precise meterage will vary according to the “key cost factors”.


• access to and within the site – many of these rigs have been specifically designed for environmentalinvestigation and are much smaller than most other types of rig. Consequently, these are able to be used inareas that may be inaccessible for other drilling methods (allow 2 m width and 5 m length);

• overhead clearance – similarly, the mast height tends to be less than for many other rig types (allow 3.5 m fora rig when the mast is at full height;

• available working area (allow an area of minimum 2 m X 6 m for the rig and working area around). Take intoaccount the fact that the rig may be noisy and generate diesel fumes which may be a problem in areasconfined between buildings, near public walkways etc.;

• availability of washdown facilities, with power and freshwater supply, for washing of the augers etc. that canbe accessed by the towing vehicle.



An auger rig with associated equipment and open borehole present a wide range of hazards. Boreholes canusually be completed in one day but occasionally, may take more than one day to drill, install and complete. Inthese instances, the general area should be made safe and consideration should be given to the use of securefencing – particularly in areas accessible to the public.

Personnel working alongside an operational rig should take the utmost care – the augers, when turning, presentconsiderable physical hazard. Ear defenders may be needed in the vicinity of the rig.

With careful borehole design and construction, HSA and CFA may be used to drill through an aquiclude/lowpermeability horizon into an aquifer. See “basic description of method” for details.

Great care needs to be taken when manoeuvring rigs near overhead services, site structures etc and whenexcavating in the vicinity of services, near walls, fences, buildings, archaeological remains etc. to avoid damage.If structures are close by, this can occur some time later if settlement occurs.

Similarly, care needs to be taken to avoid damage to flora and fauna, especially protected species by careful sitingof the borehole, rig and arisings. When working under trees, consider the rig’s height and avoid damaging thecanopy.

If unmanageable materials (e.g. unexpected friable asbestos) or unexpected conditions (e.g. gases/strong odours)are encountered, drilling should be halted (leaving augers in the ground), the hole covered with a sheet, board orotherwise and method of investigation and health and safety arrangements re-appraised.

Once the borehole is completed, the general area must be left safe e.g. disturbed ground should be made good,any exposed contaminated material covered with clean and surplus arisings need to be properly managed.




“Guidance For The SafeInvestigation By Drilling Of LandfillsAnd Contaminated Land” SiteInvestigation Steering Group (1993)Thomas Telford, London

“Practical Handbook of Ground-Water Monitoring” edited by DavidM Nielsen (1991), Lewis Publishers,Michigan, USA (Chapters 6 and 7)


“Guidance Notes for the SafeDrilling of Landfill and ContaminatedLand” British Drilling Association(Operations) Ltd, Essex



CABLE PERCUSSION DRILLING

Related techniques and names: Shell and Auger, Cable-tool percussion.


Cable percussive drilling is the oldest and simplest form of drilling where advancement of the borehole is byhammering (percussion) a tool into the formation by cutting a hole or by bailing out the material. It is the mostcommon form of drilling in the UK.

The type of rig is usually an “A” frame type which arrives on site pulled by a four-wheel drive vehicle. Some cablepercussion rigs are fitted to lorry bases and these may offer rotary drilling as well. This system of drilling is verycommon for geotechnical investigations but is widely used on environmental projects as well. This technique isused mainly for boring into and sampling superficial deposits rather than bedrock. The boring equipment is simplein design and comprises a cable passing from a winch, over a pulley at the top of the rig’s mast to the boring tools.The tools are lifted and dropped successively and, as they advance and the borehole is deepened, more cable isfed from the winch drum.

The boring tools are robust steel tubes with a solid weight fitted above them, around 1500 mm long and ofdiameters ranging from 140 mm to 300 mm. They are designed to sample the ground in that, as the open endhits the formation on the down stroke, material is forced inside and retrieved when the tool is withdrawn at thesurface. Water is sometimes added to the borehole to assist in this. Different boring tools are available to suitdifferent types of ground conditions. A shell (a round cylinder with a flap valve) is used in non-cohesive materialswhile a claycutter (with windows in its sides) is used in cohesive materials. When the ground contains layers ofcobbles or boulders that inhibit the boring tools, a chisel can be used instead to break through and then boringresumes below.

As this technique is used mainly in soft ground conditions, the borehole may need to be lined with “casing” that isadvanced at the same rate as the boring tools to maintain stability and minimise the entry of unwantedgroundwater into the deepening borehole. In some circumstances, it may be necessary to use several differentstrings of casing and the more formations that there are requiring sealing-off, the larger the diameter of casingthat will be needed to start the borehole. Casings of 250 mm, 200 mm and 150 mm are conventional and it is the150 mm diameter casing that is most commonly used.

The technique may be used when there is a need to drill through an aquiclude into an aquifer. In these cases, theborehole is drilled in stages and at each change in casing diameter, a robust bentonite seal is placed at the baseand allowed to rehydrate prior to further advancement of the borehole at the narrower diameter.

Soil samples can be taken for environmental and geotechnical purposes. “Bulk” disturbed samples can be takenfrom the drill cuttings and undisturbed samples can be taken using U38 or U100 sample tubes (denoting 38 mmand 100 mm diameters respectively with the latter also called U4 denoting 4 inch). In situ geotechnical tests suchas SPT (Standard Penetration Tests) can also be carried out during drilling if required.

Cable percussion drilling is generally used for depths less than 40 m and typical drilling depths for groundcontamination investigations are 5 m to 20 m. Significantly greater depths can be achieved from the rarer, veryheavy duty, rigs.

“A” frame cable percussion rigs are fairly manoeuvrable as they are light but the length of the frame (6 m)prevents access to tight locations. Many contractors have “cut-down” mast rigs for access and operation in limitedheadroom locations if required. The method can generate considerable mess, particularly in soft clays and whenshelling out sands and silts.






Sequence of events:• an appropriate location for the borehole is chosen and a “before” photograph may be taken. It may be

necessary to protect the ground surface from contaminated arisings using plastic sheeting, wooden boardsetc. and to use sand-bags or other methods to contain water as the borehole is drilled and arisings extracted;

! any surface concrete is broken or cored through and a hand-dug “starter pit” may be required (e.g. to checkthat there are no pipes/cables etc at the drilling location). The Drill Supervisor or Second Man manoeuvresthe drilling rig into position and the legs of the mast are locked into position using cross-bars at above headheight. The general requirements for drilling, sampling, in situ tests and the design of the groundwater/gasmonitoring installation (if needed) etc. are confirmed before the borehole is started. It is usually desirable,however for some flexibility to be maintained as the borehole is drilled and the conditions emerge;

! a suitable boring tool is used to cut the start of the borehole and, at a suitable depth (usually less than 1 m),the first length of casing is established to which others are attached and progressively advanced as theborehole deepens;

• as the borehole develops the scientist/engineer liaises with the drilling crew on precise sampling andgroundwater measurement requirements and any in situ tests that are needed, but stands a safe distanceback from and avoids obstructing the actual drilling process. Anyone approaching the rig, aside from thedrilling crew, should do so only when the cable tools are at rest on the ground and all the time with anawareness of the safety of the rig itself, the equipment in the vicinity and the condition of the ground surface.All personnel should maintain a look out for anything that may affect the safety of the drilling exercise;


• as the borehole progresses, any retrieved spoil that is not required for samples is either stockpiled temporarilyclose to the borehole or placed directly into bags. Whichever method is chosen, the arisings are stored insuch a way that any that are suitable can be used as backfill material at the appropriate time, while those thatare not, are stored temporarily in a skip on the site and then disposed of appropriately;

• once the desired depth is reached, final measurements of the depth of the hole and groundwater level aretaken. If a groundwater/gas monitoring installation is required, this is constructed carefully by the drillingcrew under instruction from the scientist/engineer and the top of the borehole fitted with an appropriatecover. Re-instatement works that are needed are carried out (arrangements for this should be made beforestarting the investigation);

! irrespective of whether formal re-instatement works are to be carried out, it is important that the boreholeand surrounding area are left in a safe condition. Open boreholes and drilling equipment should not be leftunattended unless securely roped, coned or fenced off (safety issues are covered below).


ApplicationsPrimarily suitable for geotechnical investigations but is widely used on environmental projects.

Cable percussive boring is suitable for all but the densest ground conditions/unweathered bedrock. Can be used inmade ground (but not for very coarse fill e.g. containing tyres, compact paper, a large proportion of metalartefacts, timber etc.).

Suitable for sites where access is unrestricted.

Large quantities of soil for samples can be taken and it is possible to measure, fairly precisely, the depth fromwhich soil samples have been obtained.

The larger diameter boring tools allow inspection of a larger proportion of the groundmass compared to most ofthe other drilling techniques widely available for investigation of contaminated sites.

Robust groundwater and gas monitoring installations can be established. Nested installations may be achievable ifa borehole is drilled at wide diameter and good bentonite seals are constructed carefully.

LimitationsNot suitable for very small or confined sites.

Considerable quantities of water may need to be added to the borehole during drilling to enable collection of sandsand gravels.

Hard layers can be difficult and take long periods of time to chisel through.

The sections of casing may be of different lengths and these need to be checked as they are inserted if a record ofthe depth of casing used (a costed item) is to be kept independently of the Drill Supervisor.

Cable percussive boring can cause a significant amount of mess if the containment of arisings (both solid andliquid) is not planned for carefully. These can slow down the drilling operations slightly.



Key cost factors

• a wide range of unexpected situations can cause drilling to halt and drillers to go on “standing time”;

• nature of the ground conditions;

• depth of boring needed;



• need for containment measures in relation to solid and liquid arisings;

• drill spoil storage/disposal;


NB – cable percussive drilling is usually charged by the metre with additional costs applied to sampling, in situtesting, standing time etc. Many cable percussive drillers prefer straightforward drilling into “clean” ground withminimal sampling, testing etc. as it is that which gives the greatest financial return. It may be necessary,sometimes, to ‘slow down’ the rate of drilling to maintain control over the quality of sampling, measurementstaken etc.


Supervision of a cable percussive drilling contractor should be carried out only by an experiencedscientist/engineer that is familiar with this method of drilling and the way cable percussive drilling crews operate.One such scientist/engineer should be allocated to each rig and should be prepared to carry out or superviseclosely, the majority of the “hands on” sampling of soils.

A drilling crew should be used that is BDA (British Drilling Association) accredited for cable percussive work, hasexperience of working on a wide range of contaminated sites and is prepared to be flexible in terms of respondingto the emerging conditions, sampling requirements, borehole design etc. Many cable percussive drilling crewsprefer “clean” geotechnical work and it is essential that the nature of the ground conditions and the approach tosafe working is clearly specified at the time of the initial enquiry about availability for hire. There may be a needto re-state the need for particular personal protective equipment, safe working practices etc. throughout theduration of an investigation of a contaminated site, particularly where drillers are more familiar withuncontaminated conditions.

It is important that the supervising scientist/engineer double checks each measurement of borehole depth, gravelpack, bentonite seals etc.

On average, around 15 m to 20 m per day (no surface concrete) should be achieved per cable percussive drillingrig/crew although the precise meterage will vary according to the factors listed in the section “key cost factors”.


• Access within the site (for a towed drilling rig allow 2 m width and 12 m length;

• overhead clearance (allow 6.5 m for a rig when raised);

• available working area (allow an area of minimum 2.5 m X 6 m for the rig and the towing vehicle (usually alarge four-wheel drive vehicle) will also need to have access. A general working area around the rig of is alsodesirable). Take into account the fact that the rig will be noisy and generate diesel fumes which may be aproblem in areas confined between buildings, near public walkways etc.;

• availability of washdown facilities, with power and freshwater supply, for washing of the casing, boring toolsetc. that can be accessed by the towing vehicle;

• a skip will be needed for storage and disposal of arisings.




An operating drilling rig with associated equipment and open borehole present a wide range of hazards. Cablepercussive boreholes may take more than one day to drill, install and complete and, when unattended, the generalarea should be made safe and consideration should be given to the use of secure fencing – particularly in areasaccessible to the public.

The drill rig cable, shackles etc. must be in good condition. It is circumspect for the supervising scientist/engineerto require that a copy of a recent test certificate on the cable is provided. The rig must only be operated with thecross-bars on the tripod legs properly locked into position. If this were not the case, there would be risk of rigcollapse.

Personnel working alongside an operational rig should take the utmost care – the boring tools attached to thecable, in particular, present considerable physical hazards. Ear defenders may be needed in the vicinity of the rig.

With careful borehole design and construction, cable percussion may be used to drill through an aquiclude/lowpermeability horizon into an aquifer. See “basic description of method” for details.


Similarly, care needs to be taken to avoid damage to flora and fauna, especially protected species by careful sitingof the borehole, rig and arisings. When working under trees, consider the rig’s height and avoid damaging thecanopy.

If unmanageable materials (e.g. unexpected friable asbestos) or unexpected conditions (e.g. gases/strong odours)are encountered, drilling should be halted, the hole covered with a sheet, board or otherwise and method ofinvestigation and health and safety arrangements re-appraised.










ROTARY CORING

Related techniques and names: diamond core drilling


Rotary core drilling is a method in which a drill string, comprising a drill pipe with an attached steel core barrel andcoring bit, is rotated continuously against the formation with a steady load. The method can be used in virtuallyany stable geological formation, particularly consolidated rocks. Rotation speed can be slow to fast (10-2000 rpm)depending on the formation being drilled and the specific rig used.

Most commonly used for exploration uses, this system can also be used on environmental projects. Coring is veryuseful in sandstone, limestone and chalk where contamination may have penetrated the weathered zone, ortravelled through the formation or fractures. Air flush can be used to aid drilling although additives such as waterand foam may be needed and these are generally undesirable for ground contamination investigations.

The core bit contains diamond or tungsten cutting teeth/chips (hence the alternative name of diamond coredrilling) and these break only a small portion of the borehole face. The remainder is left intact inside the corebarrel as it moves down, providing a continuous sample of the ground penetrated. At intervals, this is brought tothe surface. Circulation fluid is pumped through the drill rods and barrel to flush the fine fragments from the thinannular ring and to cool the cutting face. Fluids are also often used to help maintain the stability of the boreholewall, although for the depth and nature of drilling typically carried out during investigation of contaminated sites,stability is usually achieved by inserting casings. It is appropriate to request that these additives arebiodegradable or based on natural products.

The “round trip” of: (i) drilling the length of the core barrel; (ii) removing the drill string;(iii) emptying the barrel;(iv) returning the barrel and drill string to the borehole; and (v) re-commencing drilling can be time consuming.To reduce this, a method of rotary core drilling called “wire line coring” has been developed. With this techniquethe inner tube and its core may be recovered without removing the entire drill string from the borehole via asystem of locking/releasing mechanisms attached to the core barrel.

The simplest core barrels comprise a single tube and coring bit which are suitable only for coring hard rocks. Adouble tube core barrel is used in less cohesive rocks i.e. an inner liner is added to the core barrel. With very softmaterials, a second inner liner may be used which reduces disturbance to it as it is handled at the surface. Thediameter of the core barrels and cores vary widely (core barrels generally between 36 mm and 200 mm and coresof between 21 mm and 165 mm). Boreholes to many hundreds of metres depth can be achieved i.e. much greaterthan that likely to be needed for investigation of contaminated sites.

Rotary core drilling is typically accomplished with vehicle mounted rigs (4X4, truck, track or trailer) that carry theirown pumps, and operating components. Many are relatively small rigs but some rigs are large complexassemblies that require a considerable amount of space in which to operate.

It is possible to rotary core into an aquifer protected by an aquiclude. However, it is not a straightforwardoperation and the exact approach will need to be thought through carefully and tailored to the specific sitegeology, sampling requirements etc. In some cases it may be necessary to start the borehole using a differentmethod e.g. cable percussive (although modern rotary rigs are versatile and able to drill through a range ofconditions). Where drilling into an aquifer, the borehole will need to be drilled at wide diameter to the aquicludestratum. A good bentonite plug (around 1-2 m) will be needed at the base with the casings left in place above (ifused – in stable conditions casings may not be necessary) and the bentonite left to hydrate. The borehole canthen be re-drilled by rotary coring at a narrower diameter down through the cased hole, the seal and into the rockformation below.






Sequence of events:• an appropriate location for the borehole is chosen and a “before” photograph may be taken. Any surface

concrete is broken or cored through. It is virtually impossible to protect the ground surface completely fromcontaminated arisings due to the volume of flush water/formation water and arisings that are ejected from theborehole intermittently (see “limitations” below). Nevertheless, the use of plastic sheeting, wooden boardssand-bags or other methods to contain these may reduce the extent of the area that is affected.

• if a different drilling method, e.g. cable percussive, is to be used to drill the upper part of the borehole toavoid causing cross-contamination into an aquifer (see above), this is completed and the rig removed. TheDrill Supervisor or Second Man then manoeuvres the rotary coring rig into position and progresses theborehole. If only rotary coring is to be used for the whole borehole, the rig is similarly set up from the outset;


• drilling commences and, at a suitable depth (usually less than 1 m), the first length of casing is established towhich others are attached and progressively advanced as the borehole deepens;

• as the borehole develops the scientist/engineer liaises with the drilling crew on precise sampling andgroundwater measurement requirements and any in situ tests that are needed, but stands a safe distanceback from and avoids obstructing the actual drilling process. Anyone approaching the rig, aside from thedrilling crew, should do so only after indicating to the Drill Supervisor of this intention as it may be necessaryto stop the drilling mechanism. At certain times e.g. when “running in/out” the drill rods, the Drill Supervisorwill not permit non-drilling personnel to approach. When approaching the rig, this must be done with anawareness of the safety of the rig itself, the equipment in the vicinity and the condition of the ground surface.All personnel maintain a look out for anything that may affect the safety of the drilling exercise;


• as the borehole progresses, the core samples will be placed in special core boxes for recording of the depthsthat the “run” came from, logging on site or to be sent for analysis/storage. The fragments of drilledformation that are flushed out of the deepening borehole gradually form a “carpet” around the top of the hole.Any unwanted arisings are disposed of appropriately but the total volume of these arisings is usually relativelysmall;


• re-instatement works that are needed are carried out (arrangements for this should be made before startingthe investigation). Irrespective of whether formal re-instatement works are to be carried out, it is importantthat the borehole and surrounding area are left in a safe condition. Open boreholes and drilling equipmentshould not be left unattended unless securely roped, coned or fenced off (safety issues are covered below).


ApplicationsRotary coring is suitable for virtually all stable ground conditions – particularly highly consolidated rocks and somemodern rigs have equipment that can be used in unconsolidated conditions.

This form of drilling is capable of achieving considerable depths.

It is possible to measure, very precisely, the depth from which samples have been obtained.

The method allows retrieval of cores for inspection and laboratory analysis, although fines and weathered zonesmay be washed out.


LimitationsIt can be time-consuming to re-locate boreholes that have hit shallow obstructions. However, this drilling methodwill probably be capable of drilling through most shallow obstructions.

Flush medium and water may need to be added to the borehole.

Some rotary coring rigs are too big for flexible use on small and/or operational sites.

Rotary coring can generate a great deal of flushed water and arisings when working below the groundwater leveland this is a considerable disadvantage of this drilling method. Even where this is uncontaminated water/slurry,the general “mess” that can result, even with use of sandbags, plastic sheeting etc can be unacceptable on many(e.g. operational) sites. In contaminated conditions, the potential for spreading contaminated water/arisings onthe ground surface may preclude the use of this method.



Key cost factors

• the possible need for an alternative drilling method to be used for the upper section of the borehole andestablish a seal and protect an underlying aquifer;

• the possible need to install multiple casing strings;



• well design;




NB – rotary coring usually proves to be one of the most expensive drilling methods as rates tend to be higher thanfor most other methods, but offers the best recovery of consolidated rock of all systems.


Supervision of a rotary core drilling contractor should be carried out only by an experienced scientist/engineer thatis familiar with this method of drilling. One such scientist/engineer should be allocated to each rig.

A drilling crew should be used that has experience of working on a wide range of contaminated sites and isprepared to be flexible in terms of responding to the emerging conditions, sampling requirements, borehole designetc. Most rotary coring contractors do exploration or geotechnical work and it is essential that the nature of theground conditions and the approach to safe working is clearly specified at the time of the initial enquiry aboutavailability for hire.

On average, around 15 m to 20 m per day (no surface concrete) should be achieved per rotary core drillingrig/crew although the precise meterage will vary according to the factors listed in the section “key cost factors”.


Some rigs offering this system are middle to large rigs mounted on lorries and capable of deep oil and water welldrilling. Smaller rig versions are available, which may be mounted on smaller vehicles, tracks or trailer. It isalways advisable to check with the driller on space requirements prior to appointment and to be familiar with whatis available on site.

Rigs vary greatly in size - as an indication, the largest rig will be 2.5 m wide, 12 m long and be 5 m high whentravelling. When working the mast could be 15 m high although some 4X4 mounted rigs have a maximum mastheight of 5-6 m. A working area of twice the rig is recommended as a minimum. Any access, space, weight orheight restrictions should be discussed fully with the driller in advance.

Noise, diesel fumes and drill returns may be a problem on some sites and a particular problem in areas confinedbetween buildings, near public walkways etc.

Washdown facilities, with power and freshwater supply that can be accessed by the rig/vehicle will be needed.



A rotary coring rig with associated equipment and open borehole present a wide range of hazards. Boreholes maytake more than one day to drill, install and complete. When unattended, the general area should be made safeand consideration should be given to the use of secure fencing – particularly in areas accessible to the public.

Personnel in the vicinity of an operational rig should take the utmost care and the Drill Supervisor should beconsulted before approaching close to the working area. Ear defenders may be needed in the vicinity of the rig.

It is usually wise to agree with the Drilling Supervisor, the drilling, sampling and other requirements at the outsetand for the Drill Supervisor to report on the conditions encountered at agreed intervals. The work will progressmost smoothly and safely if the supervising scientist/engineer then interferes as little as possible with the drillingoperations and observes from an agreed position a few metres away from the drilling rig and equipment. Thislocation can be where the extracted cores are placed for inspection.

With careful borehole design and construction, it is possible to drill through an aquiclude/low permeability horizoninto an aquifer using rotary coring although it will often be necessary to start the borehole using a differentmethod. See “basic description of method” for details.



Similarly, care needs to be taken to avoid damage to flora and fauna, especially protected species by careful sitingof the borehole, rig and arisings. When working under trees, consider mast height and avoid damaging thecanopy. Considerable harm can be done to trees if knocked by this type of rig, even if damage is not readilyvisible at the time.






“Practical Handbook of GroundwaterMonitoring” edited by David MNielsen (1991), Lewis Publishers,Michigan, USA (Chapters 6 and 7)





ROTARY DRILLING

Related techniques and names: rock roller, drag bit


This drilling method can be used in soft to hard formations, consolidated and some unconsolidated conditions. Thisis a very common form of drilling but it is not often used in ground contamination site investigation projects,particularly as soils samples are of poor quality. However, it has application where conditions are unsuitable forother drilling methods.

The drilling rigs used may be the same as for Rotary Coring and for Down the Hole Hammer. The drilling action isproduced by rotating a drill bit with downward pressure and flush of either air, water, mud (or polymer) or foam.The drill heads can be a solid body “drag” bit with tungsten inserts for soft conditions or a variety of rock roller ortricone bits used on hard rock. The drag bit has a shearing or scraping action. The rock roller is a series of cones(usually three) that rotates against the formation. Each cone turns on its axis offering new cutting teeth to theformation. The cones are shaped so that pressure is applied to different points across the borehole face. Somecones have hardened steel teeth while others have tungsten button bits.

The use of flushing agent is to remove drill cuttings and to cool the drill bit. The use of foam or mud has theadditional function of stabilising the borehole where collapse of the formation is possible. It would be usual torecirculate the water or mud through a series of settling tanks allowing the drill cuttings to settle out before reuse.

In the case of foam and polymers, biodegradable products are available and the mud used is a natural product ofbentonite (Fullers Earth). The use of mud/polymer has the disadvantage that it may be forced into the formationrequiring significant development if the borehole is to be a well on completion. In reality, the use of foam andmud flush in drilling boreholes for ground contamination site investigations will become less as better alternativesbecome available. If a compressor is being used this can also be a source of oil into the air stream if theequipment has not been properly serviced. On particularly sensitive projects it is advisable to sample additivesintroduced into the borehole and have it analysed for the contaminants being tested for at the same time as thesoil/groundwater tests.

This method of drilling is an “open hole” system but supportive casing can be installed if required. Drill diametersreadily available will be in the order of 75 mm to 300 mm but smaller and significantly larger diameter bits can beused. Drill depths of several hundred metres can be achieved using the rock roller and a suitable drilling set upbut it is unlikely that ground contamination investigations will require drilling to the maximum depths achievable.

Soil samples are of poor quality and it can be difficult to log the borehole. Drill returns will be a constant flow offine sand to medium gravel size chippings depending on the hardness and type of formation being drilled mixedwith the flush agent. Accurate logging is particularly difficult in unstable and fill conditions which can changerapidly.

Where loose material is present at the surface such as gravel or cobble, a different method of drilling will berequired in order to case the borehole first.

It is possible to use this method to drill into an aquifer protected by an aquiclude. However, it is not astraightforward operation and the exact approach will need to be thought through carefully and tailored to thespecific site geology, sampling requirements etc. In some cases it may be necessary to start the borehole using adifferent method e.g. cable percussive (although modern rotary rigs are versatile and able to drill through a rangeof conditions). Where drilling into an aquifer, the borehole will need to be drilled at wide diameter to the aquicludestratum. A good bentonite plug (around 1-2 m) will be needed at the base with the casings left in place above (ifused – in stable conditions casings may not be necessary) and the bentonite left to hydrate. The borehole canthen be re-drilled by rotary drilling at a narrower diameter down through the cased hole, the seal and into the rockformation below.

Rock rolling is a drilling technique that is offered by a wide range of contractors using rigs that are more frequentlyused for alternative methods. For example the large rigs that are more commonly used for rotary coring can alsodo rotary drilling. Some specialist environmental drillers that have developed small auger rigs for groundcontamination investigations may also be able to offer rotary drilling using the same small rigs. Essentially, thelarger rigs will achieve greater depths but may actually be too big for the work in hand and the site.






Sequence of events

• an appropriate location for the borehole is chosen and a “before” photograph may be taken. Any surfaceconcrete is broken or cored through. It is virtually impossible to protect the ground surface completely fromcontaminated arisings due to the volume of flush water/formation water and arisings that are ejected from theborehole intermittently. Nevertheless, the use of plastic sheeting, wooden boards sand-bags or othermethods to contain these may reduce the extent of the area that is affected.

• if a different drilling method, e.g. cable percussive, is to be used to drill the upper part of the borehole toavoid causing cross-contamination into an aquifer (see above), this is completed and the rig removed. Thedrill team then manoeuvres the rotary coring rig into position and progresses the borehole. If only rotarycoring is to be used for the whole borehole, the rig is similarly set up from the outset;


• drilling commences and at a suitable depth it is usual to install a short length of temporary casing to keep theborehole straight, to prevent collapse, prevent wash-out of material in the upper surface and in the case ofwater/mud flush, to help channel the flow for recirculation.

• as the borehole deepens, the scientist/engineer liaises with the drilling crew on precise sampling andgroundwater measurement requirements and any in situ tests that are needed, but stands a safe distanceback from and avoids obstructing the actual drilling process. Anyone approaching the rig, aside from thedrilling crew, should do so only after indicating to the Drill Supervisor of this intention as it may be necessaryto stop the drilling mechanism. At certain times e.g. when drilled arisings are being flushed out, the DrillSupervisor will not permit non-drilling personnel to approach. When approaching the rig, this must be donewith an awareness of the safety of the rig itself, the equipment in the vicinity and the condition of the groundsurface. All personnel maintain a look out for anything that may affect the safety of the drilling exercise;


• as the borehole progresses, the samples will be bagged for inspection on site or to be sent to the laboratory.The fragments of drilled formation that are flushed out of the deepening borehole gradually form a “carpet”around the top of the borehole. Any unwanted arisings are disposed of appropriately;


re-instatement works that are needed are carried out (arrangements for this should be made before starting theinvestigation). Irrespective of whether formal re-instatement works are to be carried out, it is important that theborehole and surrounding area are left in a safe condition. Open boreholes and drilling equipment should not beleft unattended unless securely roped, coned or fenced off (safety issues are covered below).



Applications

Rotary drilling can be used in most ground conditions but is not suited to loose material such as sand or gravel.Cobbles or other obstructions can easily deflect the borehole in the upper zone.


Limitations

Where the flush returns are constant; samples can be taken from precise depths, however, in all cases the qualityof sample for environmental project is poor. This limits the suitability of this method of drilling when soil samplingis an objective.

It can be time-consuming to re-locate boreholes that have hit shallow obstructions.

Considerable quantities of flush medium will need to be added to the borehole.

Some rig assemblies may be too big for flexible use on small operational sites.

Rotary drilling can generate a great deal of flushed water and arisings when working below the groundwater leveland this is a considerable disadvantage of this drilling method. Even where this is uncontaminated water/slurry,the general “mess” that can result, even with use of sandbags, plastic sheeting etc can be unacceptable on many(e.g. operational) sites. In contaminated conditions, the potential for spreading contaminated water/arisings onthe ground surface may preclude the use of this method.


Key cost factors

• the possible need for an alternative drilling method to be used for the upper section of the borehole andestablish a seal and protect an underlying aquifer;







Supervision of a rotary drilling contractor should be carried out only by an experienced scientist/engineer that isfamiliar with this method of drilling. One such scientist/engineer should be allocated to each rig.

A drilling crew should be used that has experience of working on a wide range of contaminated sites and isprepared to be flexible in terms of responding to the emerging conditions, sampling requirements, borehole designetc. Most contractors do mainly exploratory or geotechnical work and it is essential that the nature of the groundconditions and the approach to safe working is clearly specified at the time of the initial enquiry about availabilityfor hire.

The meterage achievable will vary widely (15 m to 100 m per day) according to the factors listed in the section“key cost factors”” above.


Some rigs offering this system are middle to large rigs mounted on lorries and capable of deep oil and water welldrilling. Smaller rig versions are available, which may be mounted on smaller vehicles, tracks or trailer. It isalways advisable to check with the driller on space requirements prior to appointment and to be familiar with whatis available on site.

As an indication, the largest rig will be 2.5 m wide, 12 m long and be 5 m high when travelling. When working themast could be 15 m high although some 4X4 mounted rigs have a maximum mast height of 5-6 m. A workingarea of twice that of the rig is recommended as a minimum. Any access, space, weight or height restrictionsshould be discussed fully with the driller in advance. The smallest type of rig available would be about the size ofa large 4WD vehicle.






Rotary rolling equipment, the drilling rig and an open borehole present a wide range of hazards. Boreholes maytake more than one day to drill, install and complete. When unattended, the general area should be made safeand consideration should be given to the use of secure fencing – particularly in areas accessible to the public.


It is usually wise to agree with the Drill Supervisor, the drilling, sampling and other requirements at the outset andfor the Drill Supervisor to report on the conditions encountered at agreed intervals. The work will progress mostsmoothly and safely if the supervising scientist/engineer then interferes as little as possible with the drillingoperations and observes from an agreed position a few metres away from the drilling rig and equipment. Thislocation can be where the extracted cores are placed for inspection.

With careful borehole design and construction, it is possible to drill through an aquiclude/low permeability horizoninto an aquifer using rotary drilling although it will be necessary to start the borehole using a different method.See “basic description of method” for details.


Similarly, care needs to be taken to avoid damage to flora and fauna, especially protected species by careful sitingof the borehole, rig and arisings. When working under trees, consider mast height and avoid damaging thecanopy. Considerable harm can be done to trees by the larger rigs, in particular, if knocked even if damage is notreadily visible at the time.











DOWN THE HOLE HAMMER DRILLING

Related techniques and names: none. The acronym DTTH or partial acronym DTH are frequently used.


Down the Hole Hammer (DTH) is a method of rotary percussion drilling that, as its name implies, combinespercussion with some aspects of rotary drilling. Together, these result in increased penetration speed. Also,compared to rotary and percussion techniques undertaken separately, DTH is more successful in harder and moreconsolidated formations. DTH is also capable of great drilling depths as the hammer action is directly above thedrill bit i.e. impact efficiency is high as the blow energy is exactly where it will be most effective. The depthlimitation is from the power of the compressor, the head of water being displaced and the lifting capability of thedrill rig compared to the weight of the drill string.

While this drilling method can be used to establish robust groundwater and gas monitoring installations, it is notgenerally recommended for ground contamination investigations unless there is no better alternative. This isbecause soil samples are of poor quality, it can be difficult to log the horizons and internal lubrication by means ofin-line additives is needed.

The method works as compressed air is forced down the drill string and into the hammer unit where the air powersa piston in an upwards and downwards motion (which may be as frequent as 25 strokes per second). A drill stemto the surface provides very slow rotation (15 rpm to 25 rpm) and sufficient feed or retract force for properoperation of the hammer and to assist the cutting action of the bit. On each downward stroke, shock wave energypasses down the bit and, providing the bit is in contact with the borehole face, passes directly to the formation.Air that has operated the piston passes onwards through the hammer, exits across the bit face to scavenge thecuttings and cool the bit. The air and cuttings return to the surface, carried by the velocity of the air flow.Reverse Circulation DTH drilling employs a dual walled drill string and the rock chippings are passed back up theannular space between the dual walls.

Normally the volume of air will have an adequate up-hole velocity to clear the annulus of cuttings but sometimesconditions within the borehole will develop that cause the DTH hammer to lose efficiency and flushing ability. Thisis usually caused by either the production of too many cuttings during rapid penetration or groundwater enteringthe hole that exerts back pressure on the DTH hammer. While excess cuttings can easily be cleared by lifting thebit from the base of the borehole slightly, the ingress of groundwater may be sufficient to stop the action of thehammer and drilling cannot continue.

The hammer requires internal lubrication by means of in-line oilers. Oil is passed at a very low dose into the airflow and down the drill rods. This oil is typically a hydrocarbon oil as this is most readily available and cheap.Other, synthetic, biodegradable or vegetable oil based products are available. The compressor can also be asource of oil into the air stream if the equipment has not been properly serviced. On particularly sensitive projectsit is advisable to sample additives introduced into the borehole and have it analysed for the contaminants beingtested for at the same time as the soil/groundwater tests.

The DTH system is used to good effect to drill rapidly in medium to hard rock formations such as sandstone,limestone, metamorphic and igneous rocks that are stable formations. This system may also be used in less stableconditions for example interbedded clays/limestone or boulder conditions. The less stable the conditions, thehigher the risk of trapping (expensive) equipment down the hole.

In conditions that are considered unstable or where the upper layer is unstable, then a “Duplex System” can beused i.e. simultaneous cased system in conjunction with the DTH. All hammer suppliers offer their own systemwith their own trade name such as Simcas/Odex. This system operates a conventional hammer with a drill bit thathas a part that swings out on rotation so that the hole is drilled at large enough diameter to receive the followingcasing. On completion the eccentric part of the hammer slides in and the hammer can be removed. Once instable conditions and intending to drill deeper, it would be normal to switch to the standard DTH system.

With the above system, the one rig can be used to drill into an aquifer through an aquiclude (and any madeground and superficial deposits. A bentonite seal is placed at the bottom of the casing and once hydrated, drillingat a smaller DTH diameter can continue into the bedrock. This system is relatively common and available frommost drilling companies.

Most hammers in use would be to drill diameters in the range 100 mm to 300 mm but smaller and significantlylarger hammers are available. Soil samples are of poor quality for ground contamination investigations and it canbe difficult to log the borehole. Drill returns will be a constant flow of fine to medium sand to medium gravel sizechippings depending on the hardness and type of formation being drilled. Accurate logging is particularly difficultin unstable and fill conditions where these change rapidly.






Sequence of events:

• an appropriate location for the borehole is chosen and a “before” photograph may be taken. Any surfaceconcrete is broken or cored through. It may be necessary to protect the ground surface from contaminatedarisings using plastic sheeting, wooden boards etc. and to use sand-bags or other methods to contain water asthe borehole is drilled and arisings extracted. Property in the vicinity may also need protecting from the dustand chippings generated;


• the drill team then manoeuvres the auger rig into position, the appropriate type of bit is fitted and theborehole is started. In uncohesive conditions, a simultaneous casing system will be used;

• as the borehole develops the scientist/engineer liaises with the drilling crew on precise sampling andgroundwater measurement requirements and any in situ tests that are needed, but stands a safe distanceback from and avoids obstructing the actual drilling process. Anyone approaching the rig, aside from thedrilling crew, should do so only after indicating to the Drill Supervisor of this intention as it may be necessaryto stop the drilling mechanism. At certain times e.g. when drilled arisings are being flushed out, the DrillingSupervisor will not permit non-drilling personnel to approach. When approaching the rig, this must be donewith an awareness of the safety of the rig itself, the equipment in the vicinity and the condition of the groundsurface. All personnel maintain a look out for anything that may affect the safety of the drilling exercise;


• as the borehole progresses, the samples will be bagged for inspection on site or to be sent to a laboratory.The fragments of drilled formation that are flushed out of the deepening borehole gradually form a “carpet”around the top of the hole. Any unwanted arisings are disposed of appropriately;


• re-instatement works that are needed are carried out (arrangements for this should be made before startingthe investigation). Irrespective of whether formal re-instatement works are to be carried out, it is importantthat the borehole and surrounding area are left in a safe condition. Open boreholes and drilling equipmentshould not be left unattended unless securely roped, coned or fenced off (safety issues are covered below).


ApplicationsDTH is best suited to drilling in stable formations, particularly those rocks rated as medium to very hard.

Penetration in hard formations can be very rapid.

The method can be used for drilling boreholes up to and beyond the sizes usually needed for ground contaminationinvestigations e.g. up to about 600 mm diameter and to depths of 1000 m.

Robust groundwater and gas monitoring installations can be established.

DTH using simultaneous casing can be used in a wide variety of situations.

DTH can be used to drill through most conditions.


LimitationsDTH is not recommended for ground contamination investigations unless there is no better alternative because soilsamples are of poor quality, it can be difficult to log the horizons and internal lubrication by means of in-lineadditives is needed.

DTH is inefficient at drilling through superficial deposits and other unconsolidated formations, unless asimultaneous casing is used.

Performs poorly in “sticky” formations (e.g. soft clays) where returns can be poor and clogging can occur.

Requires a large amount of fuel and a powerful compressor.

Requires oils to be used for lubrication.

DTH can drill through most conditions but fill with metal, rubber and paper can be problematic.

DTH can cause a significant amount of mess, particularly air-borne dust in unsaturated rock zones. On manyderelict or redevelopment sites this will not matter but on operational sites this may be unacceptable andcontainment measures will needs to be planned carefully. These can slow down the drilling operations slightly.

The compressor needed is powerful and can be particularly noisy. In some situations, vibration can be sufficient todamage nearby pipes, foundations etc.


Key cost factors



• the possible need to install multiple casing strings;





The DTH and simultaneous casing system should be commonly available. Rigs tend to be relatively large (seebelow) but small rigs may also offer this drilling method.

For ground contamination investigations, daily meterage in the order of 20 m to 80 m would be expected,depending on the drilling conditions (for exploratory purposes, greater meterage can be achieved).


Most rigs offering this system tend to be middle to large rigs mounted on lorries and capable of water well drilling.Smaller rig versions are available which may be mounted on smaller vehicles, tracks or trailer. It is alwaysadvisable to check with the driller on space requirements prior to appointment and to be familiar with what isavailable on site.

As an indication, the largest rig will be 2.5 m wide, 12 m long and be 5 m high when travelling. When working themast could be 15 m high and a working area of twice the rig is recommended as a minimum. Any access, space,weight or height restrictions should be discussed fully with the driller in advance. The smallest type of rig availablewould be about the size of a large 4WD vehicle.






A DTH rig, associated equipment and open borehole present a wide range of hazards. Boreholes can usually becompleted in one day but occasionally, may take more than one day to drill, install and complete. In theseinstances, the general area should be made safe and consideration should be given to the use of secure fencing –particularly in areas accessible to the public.


It is usually wise to agree with the Drill Supervisor, the drilling, sampling and other requirements at the outset andfor the Drill Supervisor to report on the conditions encountered at agreed intervals. The work will progress mostsmoothly and safely if the supervising scientist/engineer then interferes as little as possible with the drillingoperations and observes from an agreed position a few metres away from the drilling rig and equipment. Thislocation can be where the samples are placed for inspection.

With careful borehole design and construction, it is possible to drill through an aquiclude/low permeability horizoninto an aquifer using DTH. See “basic description of method” for details.


Similarly, care needs to be taken to avoid damage to flora and fauna, especially protected species by careful sitingof the borehole, rig and arisings. When working under trees, consider mast height and avoid damaging thecanopy. Considerable harm can be done to trees if knocked by this type of rig, even if damage is not readilyvisible at the time.











WINDOW SAMPLING

Related techniques and names: none


Window sampling is essentially a percussive method of creating small diameter boreholes. Mostly the technique isachieved using hand-held equipment but some small drilling rigs have the capacity for window-sampling and thepower of the rig enables window samplers to be driven to, and extracted from, greater depths compared to themanual technique.

A window sampler is a high tensile steel tube with a hardened cutting shoe to penetrate hard materials. Eachsampler is usually 1 m or 2 m long with a series of “windows” or slots cut in the wall of the tube through which toview or extract soil samples. Samplers are driven down into the ground using a percussive hammer. A full set ofwindow samplers usually consists of around four samplers ranging in diameter from 80 mm down to 35 mm.These are used systematically, starting with the widest and subsequently at reducing diameter to the requireddepth or limit of the technique. The depth limit tends to be around 8 m to 10 m although the technique is usuallyused to a maximum depth of around 5 m. In practice, the limiting factor tends not to be how deep the samplerscan be driven in but rather whether the ground conditions are such that they may then be pulled back out. Coarsedense gravels, in particular, can grip the samplers and make extraction extremely difficult. The Drill Supervisorwill assess the conditions at each location individually.

The start diameter is dictated by the ground conditions i.e. the softer the conditions, the wider the sampler setthat can be driven in. Typically, however, a 60 mm to 80 mm diameter start sampler will be used, reducing toaround 35 mm by around 4 m to 5 m depth. The full samplers are either jacked out manually or pulled from thehole using a hydraulic jacking system.

A full sampler will reveal a complete or partial ground profile although guidance from the Drill Supervisor will beneeded on any compression that may have occurred and resulted in, for example, a 1.5 m sample occupying a 1 mspace in the sampler. With some window sampling systems, samples can be recovered in a thin walledtransparent liner placed inside the steel tubes. The liner is removed for visual inspection or capped at each end fortransporting to the laboratory. Whatever system is used, the quantity of soil within the sampler is small and,particularly where the analytical suite is extensive, a sample may have to be taken from a 0.5 m or so section toensure sufficient quantity. The advantage, however, is that once soil is taken for samples and backfillingpurposes, there is rarely any excess requiring disposal.

Narrow diameter groundwater/gas monitoring installations can be constructed in the borehole once all samplersare withdrawn. Whilst the diameter of the standpipe is ultimately dictated by the diameter of the smallest (andlowest positioned) sampler, in practice it is usually possible to install a 19 mm or 35 mm standpipe with a finegravel pack surround. With some systems, it is possible to drive a water well in through unsampled ground usingthe hammer unit.

This method is not suitable where there is a need to drill through an aquiclude into an aquifer as there is no way ofprotecting the aquifer from downwards migration of any contaminants from the ground above the aquiclude duringdrilling.

The equipment is generally brought to site in a van or four-wheel drive vehicle and from then on, it can be carriedby hand around the site. In many circumstances the fact that this is largely a manual method is its advantageover even the smallest drilling rigs. Window sampling causes minimal disturbance to the ground surface (e.g.useful for investigations inside buildings, in a landscaped car park or between the sleepers of rail lines. Themethod can be used where access is very restricted (e.g. small operational sites and in gardens). It can alsoachieve rapid coverage to shallow depth (e.g. useful for establishing the thickness of a landfill cap over a largearea).

Sequence of events:

• an appropriate location for the window sampler borehole (“the borehole”) is chosen and a ‘before’ photographmay be taken. Any surface concrete is broken or cored through. It is usually unnecessary to protect theground surface as the method generates hardly any mess. However, if needed, samplers can be placed onplastic sheeting during sampling to protect particularly sensitive ground surfaces.



• the first, and widest, sampler is driven fully into the ground and withdrawn. The next narrower one is pushedthrough the open hole to its base and then driven, in turn, into the soil at the bottom. This sequence isrepeated using progressively smaller diameter samplers down to the required depth or limit of the techniquein the particular ground conditions encountered;

• as the borehole develops the scientist/engineer liaises with the drilling crew on precise sampling andgroundwater measurement requirements, but avoids obstructing the actual drilling and jacking out processes.All personnel maintain a look out for anything that may affect the safety of the drilling exercise;

• if there is spoil in excess of that needed for sampling/backfilling purposes, this is placed directly into bags andstored in such a way that they may be disposed of appropriately once the investigation has finished;

• once the desired depth is reached, a groundwater/gas monitoring installation is constructed carefully by thedrilling crew (if required) and the top of the borehole fitted with an appropriate cover. If an installation is notneeded, the hole is backfilled with clean suitable material. This can be any spoil in excess of that required forsampling (if suitable), clean sand/gravel (if appropriate) or bentonite to prevent future downward migration ofcontaminants through the hole;

• On many sites it is unlikely that any re-instatement works will be needed. If they are (e.g. concrete/tarmacrepair), these are carried out (arrangements for this should be made before starting the investigation). Theborehole and surrounding area must be left in a safe condition. Drilling equipment should not be leftunattended, not least due to its portability (safety issues are covered below).


Applications

Window sampling is most suitable for clay, sand, glacial tills and some made ground.

It is possible to measure, fairly precisely, the depth from which soil samples have been obtained although theadvice of the Drill Supervisor should be sought on whether the sample has been compressed within the sampler.

The method is fast, particularly where only the shallow ground needs to be drilled.

If obstructions are encountered, it is usually an easy and quick exercise to re-locate elsewhere.

Virtually no mess is created.

Window sampling is, under controlled conditions, suitable for investigations into ground known to contain difficultto manage materials such as asbestos and highly odorous wastes as only very small quantities are brought to thesurface, very little ground is opened up and excess spoil requiring specialist disposal can be avoided.

The engine on the hand-held equipment generates noise similar to a lawn-mower and this can mean that it isparticularly suitable for “sensitive” investigations in, for example, householders’ gardens where larger rigs mayprove intimidating and cause alarm.

Relatively inexpensive groundwater and gas monitoring installations can be established.

Window sampling is a relatively clean drilling process as no additives (water, foam etc.) are required to aid drilling.As such, this system is particularly favoured for environmental projects.

The equipment is easy to clean between locations and a drilling crew will usually carry several complete sets ofsamplers.

Limitations

Compacted/hard layers and buried concrete can be difficult to progress through.

The method does not work well in some fill materials that includes large quantities of paper, rubber, wood andmetal.

While some contractors will claim that depths to 20 m can be achieved, this method should really be viewed as onemost successful in shallow depths. In practice, depths of around 5 m are typical with depths of around 8 m to10 m achievable in only very favourable conditions. At greater depths, the diameter of the samplers will be muchreduced and consequently only small soil samples can be retrieved.

Dense gravels can grip onto the samplers and make extraction difficult.

The method is not suitable in spark-risk situations.



Key cost factors


• distance between sampling locations (equipment can easily be carried but, if the distance between locationexceeds more than about 200 m, it may prove quicker to use a vehicle;

• presence of fences/walls/steep inclines/dense vegetation etc. that may inhibit transport of equipment betweenlocations by hand;


• surface cover (need for concrete to be broken through);

• sampling and In situ testing requirements.


There are an increasing number of specialist environmental drilling companies that offer window sampling forground contamination investigations.

On average, around 20 m to 30 m per day (no surface concrete) should be achieved (no installations constructedi.e. all drilled boreholes backfilled). If all boreholes are installed, around 20 m to 25 m per day (no surfaceconcrete) should be achieved. In both cases, the precise meterage will vary according to the “key cost factors”.


• access to and within the site – window sampling is a method that is particularly suited to sites where access isvery constrained and inaccessible for other drilling methods. Essentially, a window sampler borehole can bedrilled if there is space for two people and equipment the size of a small suitcase held initially just above headheight. In exceptionally small spaces, the equipment can be operated by one person but this is not ideal;

• overhead clearance - similarly, the overall height of the equipment tends to be less than for many otherdrilling methods (allow 2.5 m);

• available working area -see notes above (while a borehole can be drilled very small spaces, if possible, allow aworking area of around 2 m by 3 m to accommodate the drilling operations, the samplers on the ground andancillary equipment). The hammer unit will generate noise similar to that of lawnmower and this should beconsidered when working in locations close to members of the general public;

• availability of washdown facilities, with power and freshwater supply, for washing of the samplers etc. (can beaccessed on foot);

• knowledge of the location of buried services is essential for the safety of the drilling crew.



When used properly, window sampling equipment present few hazards.

Some of the equipment (the jacking system for example) is heavy and should only be carried by those who arefamiliar with its handling. The equipment should not be left unattended although the risks are more in relation totheft and tampering (with consequential impact on programme) rather than any physical harm presented.

Personnel working alongside a drilling crew installing and jacking out window samplers should avoid obstructingthe operations. All personnel in the immediate vicinity should wear ear defenders when the hammer unit is beingused to install the samplers into the ground.

Window sampling should not be used to penetrate through an aquiclude/low permeability horizon into an aquifer.

Great care needs to be taken when drilling in the vicinity of services and archaeological remains, particularly asthis is a percussive method applying a great deal of force onto a small cutting shoe and samplers can easilypenetrate cables, pipes etc. While care should always be taken when drilling near walls, fences and buildings, it ismost unlikely that the size of borehole created by window sampling will cause significant damage during drilling orvia later settlement.


Care needs to be taken to avoid damage to flora and fauna, especially protected species by careful siting of theborehole and operational area where samplers etc. are placed. When working under trees, consider the height ofthe hammer unit when drilling and avoid damaging the canopy.

If unexpected and unmanageable materials (e.g. friable asbestos) are encountered, drilling should be halted, thehole covered with a sheet, board or otherwise and method of investigation and health and safety arrangements re-appraised.

Once the borehole is completed, the general area must be left safe e.g. the small area of disturbed ground shouldbe made good.








SOIL PROBING

Related techniques and names: direct push, probing, probe-holes, geoprobe


For environmental site investigations, direct push probeholes are usually inserted using hydraulically-poweredpercussion/probing machines that rely on a small amount of static (vehicle) weight acting on a hammer unit as theenergy for advancement of a tool string made up of 1 m long rods. The vehicle used is often a small van that hasa series of hydraulic rams that allow the sampling hammer to be unfolded from its rear. This permits sampling tobe carried out close to buildings and site boundaries.

Tools are available for sampling soil, water and soil gas and many of these are US EPA approved. Depending onthe diameter of the sampling tool, permanent installations can also be constructed once sampling is completed.

Narrow diameter groundwater/gas monitoring installations can be constructed in the borehole once all samplersare withdrawn. It is usually possible to install a 19 mm or 35 mm standpipe with a fine gravel pack surround.

This method is not suitable where there is a need to drill through an aquiclude into an aquifer as there is no way ofprotecting the aquifer from downwards migration of any contaminants from the ground above the aquiclude duringdrilling.

Soil Sampling

Sampling tools for soil sampling are rugged, designed to avoid cross-contamination between samples and containliners that vary in diameter between 25 mm and 40 mm (the smaller diameter tools avoid the generation of excessspoil). The tool assembly contains a releasable piston system to prevent the ingress of soil and liquids into thesample liner as the tool is driven into the ground. At the required sampling depth, the piston is released and thetool pushed further, thus filling the liner. A new sample line is used for each sample taken. Typical samplingdepths of 10 m to 15 m are routinely achieved in UK soil conditions. Once soil is taken for sampling purposes,there is rarely any excess requiring disposal.

Soil Gas and ground water sampling

Similar to soil sampling, the soil gas and groundwater sampling tools are driven to the required depth with thesampling port closed. However, at the required sampling depth, a sample line is installed inside the drive rods andthis connects to the back of the sample port. The line is pulled back which opens the sampling port and the on-board pump is used to obtain a sample by drawing it into the sampler. Some companies also offer tools that areable to measure, in situ, the presence of semi-volatile or volatile organic compounds in soil and groundwater aswell as the measurement of soil type and strength. Typical sampling depths of 10 m to 25 m are routinelyachieved in the UK.

The depth limit tends to be around 8 m to 10 m although the technique is usually used to a maximum depth ofaround 5 m. The Drill Supervisor will assess the conditions at each location individually.

Sequence of events:

• an appropriate location for the probehole is chosen and a ‘before’ photograph may be taken. Any surfaceconcrete is broken or cored through. It is usually unnecessary to protect the ground surface as the methodgenerates little mess. However, if needed, samplers and other tools can be placed on plastic sheeting duringsampling to protect particularly sensitive ground surfaces.

• the general requirements for drilling, sampling, in situ tests and the design of the groundwater/gas monitoringinstallation (if needed) etc. are confirmed before the borehole is started. It is usually desirable, however forsome flexibility to be maintained as work progresses and the conditions emerge;

• the vehicle driver manoeuvres the vehicle over the location and unfolds the hammer sampling mast;

• as the probehole develops the scientist/engineer liaises with the drilling crew on precise sampling and otherrequirements. All personnel maintain a look out for anything that may affect the safety of the drillingexercise;

• if there is spoil in excess of that needed for sampling purposes, this is placed directly into bags and stored insuch a way that it may be disposed of appropriately once the investigation has finished;

• once sampling is finished, a groundwater/gas monitoring installation is constructed carefully by the drillingcrew (if required) and the top of the borehole fitted with an appropriate cover. If an installation is not needed,the hole is backfilled with clean suitable material. This can be any spoil in excess of that required for sampling(if suitable), clean sand/gravel (if appropriate) or bentonite to prevent future downward migration ofcontaminants through the hole;


• On many sites it is unlikely that any re-instatement works will be needed. If they are (e.g. concrete/tarmacrepair), these are carried out (arrangements for this should be made before starting the investigation). Theborehole and surrounding area must be left in a safe condition. Equipment should not be left unattended(safety issues are covered below).


Applications

Probe holes can be carried out in most UK soil conditions but may meet refusal in gravel deposits.

It is possible to measure, fairly precisely, the depth from which soil samples have been obtained although theadvice of the Drill Supervisor should be sought on whether the sample has been compressed.

The method is relatively fast, particularly where only the shallow ground needs to be drilled.

If obstructions are encountered, it is usually an easy and quick exercise to re-locate elsewhere.

Virtually no mess is created.

It is a relatively clean drilling process as no additives (water, foam etc.) are required to aid drilling. As such, thissystem is particularly favoured for environmental projects.

The equipment is easy to clean between locations and a drilling crew will usually carry several complete sets.

Limitations

Compacted/hard layers can be difficult to progress through.

The method does not work well in some fill materials that includes large quantities of paper, rubber, wood andmetal.

While some contractors will claim that depths to 30 m can be achieved, this method should really be viewed as onemost successful in shallow depths. In practice, depths of around 5 m are typical with depths of around 8 m to10 m achievable in only very favourable conditions.

Dense gravels can grip onto the rods make extraction difficult.


Key cost factors




• sampling and In situ testing requirements.


There are an increasing number of specialist companies that offer this technique for ground contaminationinvestigations.

On average, around 7 probe holes to around 6 m per day (no surface concrete and continuous sampling) should beachieved (no installations constructed i.e. all drilled boreholes backfilled). If all boreholes are installed, around 5per day (no surface concrete) should be achieved. In both cases, the precise meterage will vary according to the“key cost factors”.


• access to and within the site – this equipment is vehicle-deployed and access requirements will depend on thesize of the vehicle. Generally, allow 2 m width and 5 m length;

• overhead clearance - similarly, this will depend on the vehicle deploying the technique. Generally, allow 3 mthe mast at full height;

• available working area (allow an area of minimum 2 m X 6 m for the vehicle and a working area around).Take into account the fact that the equipment may generate fumes which may be a problem in areas confinedbetween buildings, near public walkways etc;

• availability of washdown facilities, with power and freshwater supply, for washing of the equipment that canbe accessed by the vehicle.




The equipment presents a range of hazards. Personnel working alongside operational equipment should take theutmost care. All personnel in the immediate vicinity should wear ear defenders when samplers/tools are beingdriven into the ground. Personnel working alongside a crew operating probing equipment should avoid obstructingthe operations.

Probing should not be used to penetrate through an aquiclude/low permeability horizon into an aquifer.

Great care needs to be taken when drilling in the vicinity of services and archaeological remains, particularly asthis is a percussive method applying a great deal of force onto a small area and samplers can easily penetratecables, pipes etc. While care should always be taken when drilling near walls, fences and buildings, it is mostunlikely that the size of borehole created by probing will cause significant damage via later settlement.

Similarly, care needs to be taken to avoid damage to flora and fauna, especially protected species by careful sitingof the vehicle and equipment. When working under trees, consider the mast height and avoid damaging thecanopy.








In preparing this text, the contribution of Fugro Geotechnics is gratefully acknowledged.



HAND AUGERS AND ASSOCIATED METHODS

Related techniques and names: none.


There are a number of small, simple investigation tools that can be operated by hand to sample quickly to shallowdepths (commonly around 1.25 m), without the need for circulation/flush fluids and with minimal grounddisturbance, mess and noise. Depending on the ground conditions and the tool used it is possible to install shallowrudimentary groundwater/gas monitoring installations.

The wide range of hand operated investigation tools are frequently subsumed under the title “hand auger” eventhough a number of these do not actually use an auger method. The main types are described below. Whenchoosing between these, consideration should be given to the need to avoid cross contamination, the types/sizesof samples needed etc.

Hand auger

A true hand auger comprises a helical (spiral) plane that, when screwed into the ground, shears the formation andeither captures it on a “blade” or in “jaws” at the bottom or, where the flight is continuous to the surface, conveysmaterial along the helix to the ground surface. If a groundwater/gas monitoring installation is not needed, handaugering can be used in both consolidated and unconsolidated soils to obtain samples. The method can be used tosample and create a hole for a shallow groundwater/gas monitoring installation in only consolidated conditions.The method is not suitable for use in highly consolidated rocks. This type of auger can create holes ranging indiameters between 70 mm and 200 mm to depths varying widely with ground conditions e.g. 1. m in consolidatedconditions to greater than 8 m in soft conditions.

Stony soil auger

A tool used in soils with a large gravel content. The auger bits are bent outward and capture stones between themas the auger is removed from the hole while the tubular design ensures that finer particles remain in the “jaws” ofthe auger. Samples are retrieved from the auger after it is removed from the hole. These are available indiameters between 70 mm and 140 mm and can be used to depths around 2.25 m.

Riverside auger

This has with sharp points used for sampling stiff soils and those containing a lot of fine gravel, both above andbelow the water level. Samples are retrieved from the auger after it is removed from the hole. These areavailable in diameters between 50 mm and 140 mm and can be used to depths around 1.25 m.

Soft soil auger

The soil is held between two blades in a conical shape joining at a point. The soft soil moves between the narrowentrance and is held. A sharp tap allows the soil to be removed. This tool is for sampling very soft soils (andliable to damage if used in stiffer ground). These are available in only one size i.e. 70 mm diameter which can beused to depths around 1.25 m.

Spiral auger

A hand auger rarely used in the UK. It is effectively a large corkscrew able to penetrate hard layers. Samplesmay either be taken from the material conveyed to the ground surface or, if the auger is extracted from the holecarefully and contains some cohesive properties, they can be peeled away from the flights themselves. This isavailable in only one diameter i.e. 70 mm although extension rods can be used to allow sampling down to X m infavourable conditions.

Post hole borer

Similar to a conventional flighted auger but available in a wide range of diameters (75 mm to 200 mm). As itsname suggests, this equipment is intended for creating holes to take fence and other posts. It is available as ahand held system with a short length of flights or from a mechanically operated system with conventional drillingaugers. This equipment is useful for ground contamination investigations in a wide range of soil conditions anddepths. The hand held post-hole borer could achieve 1.25 m and the mechanical system significantly deeper,dependent on the conditions encountered.


Hand-held piston sampler

Used for sampling of less cohesive layers (fine sand, very soft clay and mud) below the groundwater table, softsediments in rivers, channels and ditches etc. Other augers are often used initially to reach an appropriatestratum for the piston sampler. The normal diameter is 40 mm and a full sampler set will allow sampling insuitable conditions to a depth of 5 m.

Gouge auger

A narrow diameter auger (30 mm) used to take undisturbed samples down to a depth of 1 m in soils of minimalcompaction (not widely used in ground contamination investigations).

Choice of equipment

When commissioning hand auger work from a contractor, it is necessary to be clear about the ground conditionsexpected, the type and quantity of samples needed and any requirements for groundwater/gas monitoringinstallations. In practice, a contractor will usually bring a range of auger types to allow some flexibility to respondto the emerging conditions.

Sequence of events:

• an appropriate location for the borehole is chosen and a “before” photograph may be taken. Any surfaceconcrete is broken or cored through. It is usually unnecessary to protect the ground surface as these methodsgenerates hardly any mess. However, if needed, samplers can be placed on plastic sheeting during samplingto protect particularly sensitive ground surfaces. If using a piston sampler to sample sediments in a river,lagoon etc, an appropriate boat, raft or otherwise will be needed that can be stabilised at the appropriatelocation;

• the general requirements for drilling, sampling, and the design of any (necessarily shallow) groundwater/gasmonitoring installation needed etc. are confirmed before the borehole is started. It is usually desirable,however for some flexibility to be maintained as the borehole is drilled and the conditions emerge;

• as the borehole develops the scientist/engineer liaises with the drilling crew on precise sampling andgroundwater measurement requirements, but avoids obstructing the actual processes. All personnel maintaina look out for anything that may affect the safety of the drilling exercise;

• it is rare for there to be spoil in excess of that needed for sampling/backfilling purposes but any that is spareis placed directly into bags and stored in such a way that they may be disposed of appropriately once theinvestigation has finished;

• once the desired depth is reached, the hole is either backfilled with bentonite/spoil or, in some circumstances,left to collapse in. Leaving the hole open will only be acceptable if (i) the site conditions are appropriate and(ii) very small diameter augers have been used. Where a shallow groundwater/gas monitoring installation isrequired, this is constructed carefully by the drilling crew and the top of the borehole fitted with anappropriate cover. It is most unlikely that any spoil in excess of that needed for sampling backfilling willremain but, if any does, this is bagged and disposed of appropriately;

• On many sites, it is unlikely that any re-instatement works will be needed. If they are (e.g. concrete/tarmacrepair), these are carried out (arrangements for this should be made before starting the investigation). Theborehole and surrounding area must be left in a safe condition. Drilling equipment should not be leftunattended, not least due to its portability (safety issues are covered below).


Applications

Hand held drilling tools are available that are suitable for all but the most compacted ground conditions.

It is possible to measure, fairly precisely, the depth from which soil samples have been obtained with all of thesesystems.

Shallow (around 1.25 m) groundwater and gas monitoring installations can be established quickly and relativelycheaply.

These methods are, under controlled conditions, suitable for investigations into ground known to contain difficult tomanage materials such as asbestos and highly odorous wastes. This is because only very small quantities arebrought to the surface, very little ground is opened up and excess spoil requiring specialist disposal can beavoided.

Hand-held equipment generates virtually no noise and this can mean that it is particularly suitable for “sensitive”investigations in, for example, householders’ gardens and near noise-sensitive livestock.

These methods are relatively “clean” as no additives (water, foam etc.) are required to aid drilling.

The equipment is easy to clean between locations.


Limitations

The method is not suitable for collapsing conditions or coarse gravels.

Many of the hand held tools can be used to only very shallow depths (generally around 1.25 m). The exceptionsare the Piston Sampler (5 m), the Spiral Auger (varies greatly in UK conditions and rarely used) and the Post HoleBorer (possibly up to 10 m if used in conjunction with a tripod).

With most of the most commonly used hand augers, the diameter of the equipment means that only smallquantities of soil samples can be obtained.

Compacted or hard layers can be difficult to progress through.

Dense gravels can grip onto the equipment in the ground and make extraction difficult.


Key cost factors


• distance between sampling locations (equipment can easily be carried but, if the distance between locationexceeds more than about 200 m, it may prove quicker to use a vehicle;

• presence of fences/walls/steep inclines/dense vegetation etc. that may inhibit transport of equipment betweenlocations by hand;


• sampling requirements.


Many contractors offer a range of these hand-operated methods alongside other drilling methods.

The daily meterage that can be achieved with hand augers varies markedly with the ground conditions andoperating context. Between around 20 m to 100 m per day (no surface concrete) could be achieved (noinstallations constructed i.e. all drilled boreholes backfilled). If all boreholes are installed, around 10 m m to 30 mper day (no surface concrete) should be achieved. In both cases, the precise meterage will vary according to the“key cost factors”.


• access to and within the site – these methods are particularly suited to sites where access is very constrainedand inaccessible for other drilling methods. Essentially, a small borehole can be drilled if there is space forone person and equipment that takes up the space of one other. General access for the vehicle bringing theequipment to site/general drilling location will also be needed;

• overhead clearance – similarly overhead clearance is rarely an issue with these methods as equipment is notgenerally used above head height);

• available working area -see notes above (while a borehole can be drilled in very small spaces, if possible allowa working area of around 2 m by 3 m to accommodate the drilling operations, the samplers on the ground andancillary equipment);

• availability of washdown facilities, with power and freshwater supply, for washing of the augers and ancillaryequipment etc. (can be accessed on foot).



When used properly, these types of hand held equipment present few hazards.

The equipment should not be left unattended although the risks are more in relation to theft and tampering (withconsequential impact on programme) rather than any physical harm presented.

Personnel working alongside a drilling crew operating these types of equipment should avoid obstructing theoperations.

These methods should not be used to drill through an aquiclude/low permeability horizon into an aquifer.

Care needs to be taken when drilling in the vicinity of services and archaeological remains. While care shouldalways be taken when drilling near walls, fences and buildings, it is most unlikely that the size of borehole createdby these methods will cause significant damage during drilling or via later settlement.

Care needs to be taken to avoid damage to flora and fauna, especially protected species by careful siting of theborehole and operational area where samplers etc. are placed.


If unexpected and unmanageable materials (e.g. friable asbestos) are encountered, drilling should be halted, thehole covered with a sheet, board or otherwise and method of investigation and health and safety arrangements re-appraised.

Once the borehole is completed, the general area must be left safe e.g. the small area of disturbed ground shouldbe made good.








GRAVITY SURVEYING

Related techniques and names: microgravity, gravitational sounding, gravity vertical gradient, highprecision gravity survey


Gravity surveying is a geophysical method that determines sub-surface changes in density. Gravitationalattraction is directly proportional to mass and it is this relationship that is central to the way this method works.

It is a technique that has been utilised for investigation of industrial sites for several years to , for example, detectburied tanks and voids. Traditional gravity surveying as used in the oil and mineral industries has now been givengreater resolution by the development of instruments with greater precision. These require great care to beexercised in acquiring and processing the field data. With modern equipment and careful field procedures it is nowpossible to measure gravitational changes as small as one part in 1,000 million. This enables the detection, notonly of underground voids, (both natural and man made) but also the monitoring of fluid levels in, for example,aquifer recharge and discharge.

The gravity at any point on the earth is the cumulative effect of many influences and in order for the method to beapplied, these have to be compensated for. For example, at the poles, gravity is more than at the equator becausethe polar regions are 21 km closer to the centre of the earth. Mountain tops can be up to 8km further from thecentre of the earth than the oceans, and these too experience less gravity. Between them, the sun and moonproduce two tides a day which cause the earth to bulge. Geological formations vary vertically (and also laterally)in their density and therefore mass.

The removal of positional (latitude/elevation), tidal and regional gravity effects enables the plotting of what isknown as the Bouguer Anomaly. This is also known as a residual gravity map and enables specific local densitychanges in the subsurface to be identified (depth achieved dependent on their size versus depth). Nevertheless,the likely change in gravitational attraction due to a subsurface change may be very small or masked by otherfeatures.

A typical field survey might comprise 60-80 stations per day; additional time is required to process and analysethe data set.

Sequence of events

• A modelling exercise is ideally carried out offsite as a preliminary stage to determine whether the suspectedfeature is theoretically discernible. This enables the limit of detectability to be calculated for a given site.Models may be simple two dimensional along a profile across the site or a three-dimensional model plotted asa map of expected gravitational change over an area.

• If the modelling exercise indicates that a survey could be successful, a field team is mobilised to conduct aseries of acquisition procedures to ensure that accuracy is achieved in both gravity and topographicobservations over a grid of points (or along a profile or series of profiles). This can be accomplished in anurban environment, inside or outside buildings, as well as in a brownfield or greenfield site.

• The equipment is light and easily transported in a car or van. However if the site is away from levelled tracksor roads an off-road vehicle should be provided to enable access to the survey area. In remote areas, if dataare to be processed simultaneously with acquisition, a local site hut may be desirable.

• It is usual for the Contractor to carry out field work supported by a dedicated assistant working in the localoffice carrying out data reduction. Field plots (station location and non-terrain corrected Bouguer anomalycontour maps and profiles) are produced and are often available for inspection on a daily basis.

• Unless existing ground levels are already available to an accuracy of +/-0.01 m, it will be necessary for thesurvey team (usually two persons) not only to mark out on the ground (by pegs or biodegradable paint) butalso to undertake a levelling exercise to an accuracy of 0.01 m to obtain corrected heights for each gravitystation. The modelling exercise will have determined what spacing of stations is required; 1 m to 2.5 m gridsare appropriate for environmental type investigations. Approximately 60-80 stations (which includes basereadings and repeats) is achievable each day depending on grid size and accessibility.


• A model D LaCoste & Romberg Land Gravity Microgal meter has a high precision with readings that can berepeated to 0.005 mGal (milligal) = 5 µGal. An automated levelling/recording system, the Scintrex CG-3 isalso available. Contractor should demonstrate that gravity meters have been calibrated within the last threemonths. Otherwise a calibration will need to be carried out along approved BGS, or an equivalent, calibrationrange prior to commencement of survey. Prior to the surveying exercise, the instruments will usually requirea settling period of 24 hours.

• For a large area of survey a local gravity base net will be established and tied to National Gravity ReferenceNet. Local base stations should not be located within the sphere of cultural effects, these being any man-made object capable of generating and transmitting vibrations to the ground, e.g. dwellings, roads, pylons andtheir associated effects. For both base station and field readings it may be necessary to stipulate more thanone reading be taken until repeatability is achieved. Modern instruments can sample tens to 100’s of readingsper station to provide a standard deviation within acceptable limits.

• All gravity measurements require to be corrected for tidal effects and meter drift. This is accomplished bymaking repeat readings throughout the overall period of field observations at a local sub-base station that isallocated for each day's operations. Readings are made at the local base station before and after each day'soperation and at the sub-base station at 2 hourly intervals throughout the surveying.

• Depending on the timing criticality of the survey two meters of the same make may need to be provided toensure no break in survey due to meter malfunction. Duplicate readings with both meters should be taken atthe first and last station point to determine comparability of operational meter and spare.

• Daily production may be displayed on a simple Bouguer anomaly plot and elevation plot. Together with thefield readings these can be used to identify specific station readings that may be in error or indicate a localanomaly, although this can prove costly. These readings should be repeated the following day together withadjacent stations to ensure data will fit in with the set.

• “Terrain corrections" need to be estimated because the gravity values are also affected by lateral changes inmass (e.g. local humps and/or hollows). Very local changes should be recorded by the instrument observer.A digital terrain model based on estimates of mean elevations, with the degree of sensitivity decreasing withdistance, can be used for more distant effects.

• Data should be supplied digitally. The data would include station ID, positional information, Bouguer density,observed gravity value, free air anomaly, terrain correction, the Bouguer gravity anomaly latitude correction,regional gravity gradient.

• Having acquired the data it is necessary to undertake an evaluation of the results in order for example, toreveal hitherto unknown voids or suspected underground tanks. This work element could be accomplished bythe acquisition contractor or by an alternative specialist. This may be qualitative or quantitative and shouldalways be followed by careful intrusive investigation to establish ground truth. If such investigation is notfeasible then further modelling exercises may be initiated on each of the perceived discrete anomalies toestimate the depth to the causative body (or cavity).


Applications

Location of man-made voids such as cellars, tanks and water cisterns with or without contents.

Studies of landfill sites to determine depth, extent and compaction.

Thickness of made ground/fill

Monitoring of fluid level in oil, geothermal and water reservoirs.

Karst collapses in the Carboniferous, in the Chalk and in Tertiary limestones.

Sub-surface bridged, open and partially backfilled or semi collapsed mine shafts

Shallow galleries and partially collapsed mine workings.

Endoscopic microgravity for detailed archaeological investigations.

Evaluation of the success of grouting of cavities/mine workings.

Stress relaxation in tunnels (time series measurements);

Mapping of evaporite dissolution.

Lateral discontinuities and faulting.

To a lesser extent: Ice and permafrost thickness, ice lenses within permafrost, slope stability, ground failure andvolcano eruption prediction e.g. small changes in flanks.


Limitations

Measurement of such small variations requires a very sensitive instrument. This is therefore sensitive tomicroseisms and man-made vibrations that may occur on an active industrial site. If severe these may precludemeasurements being obtainable.

To be effective there needs to be a density contrast between the desired target and host rock/soil or variations indensity within the geological structure within which the target is expected; absence of density contrast means nogravity anomaly will exist.

If strong local topographic variations are present it may be impracticable to assess the terrain corrections requiredto fully correct gravity observations.


Key cost factors

Openness of site and foot access to areas to be surveyed.

• topographic variation and/or density of vegetation.

• size of area/number of profiles to be surveyed.

• grid/station spacing to achieve useable/interpretable data set.

• ambient weather - high winds can affect ability to make readings.

• ambient vibration - prevalence of microseisms and/or machinery, vehicles, pedestrians, livestock close by.

• degree of pre and post modelling required.


Design, fieldwork and at least initial interpretations are usually best undertaken by a specialist geophysicalcontractor/consultant.

A typical geophysics team carrying out a gravity survey will comprise between one and three experiencedpersonnel carrying out the following activities:

service design - one geophysical advisor and access to computing facilities and modellingsoftware.

field measurements - one geophysicist and one surveyor or surveying assistant.

data processing - one geophysicist in addition to above if data to be reduced simultaneously withacquisition.

geophysical interpretation - one geophysical specialist with access to computing and software modellingfacilities.

environmental assessment - one geophysical advisor

It is not usually necessary for the survey team to be accompanied full time by the commissioning organisation. Itwill, however, be necessary for a technical representative from the commissioning organisation, familiar with theoverall aims of the investigation, to be present on the first day and then to maintain contact thereafter.



• the presence of unstable ground, such as potential shallow old workings, mine shafts or marshy environment.

• the existence of farm stock, which potentially could be hostile or consume/remove pegs.

• site may extend across busy highways and railway lines or rivers; adequate precautions should be made toensure safety of personnel.

• all physical survey markers to be removed on completion of survey (to avoid ingestion by stock).




Engineering Geophysics QJEG Vol.21 pp. 207-271

Civil Engineering Applications ofGeophysical InvestigationTechniques (CIRIA project report inproduction)

Reynolds, J. M. An Introduction toApplied and EnvironmentalGeophysics. Wiley

Applied Geophysics. Telford,Geldart, Sheriff and Keys,Cambridge University Press

Applied Geophysics Code ofPractice, Ministere de l'Industrie(SQUALPI) with BRGM, CGG,CGGFand LCPC, France

Institute of Civil Engineers (1999)Geophysics for Civil Engineers anIntroduction

English Heritage (1995) GeophysicalSurvey in Archaeological FieldEvaluation. Research andProfessional Services GuidelineNo. 1

Reynolds, J. M. (1996) Some basicguidelines for the procurement andinterpretation of geophysicalsurveys in environmentalinvestigations. In Forde, M. C. (ed.),Proceedings of the FourthInternational Conference on Re-Useof Contaminated Land and Landfills,2-4 July 1996, Brunel University,London. Engineering TechnicsPress, pp. 57-64.



SEISMIC SURVEYING

Related techniques and names: seismic refraction, seismic reflection, high resolution seismic, 2Dseismic, 3D seismic; surface wave seismic.


Seismic surveying may be used in two specific modes to determine sub-surface structural conditions that maycontrol the movement of fluids. Both methods rely on measuring the time taken for a seismic signal, artificiallygenerated on or close beneath the ground, to travel to a subsurface and return to a series of receivers(geophones) that are coupled to a seismic recorder. The method is based on the fact that soils and rocks vary intheir elastic properties enabling them to be differentiated along a two-dimensional vertical section.

Seismic refraction has been used for many years to identify surfaces below ground at which a signal has beencritically refracted, usually at a sub-surface exhibiting an increase of seismic wave velocity with depth such asrockhead. Depths to such surfaces can be calculated by timing the arrival at the ground surface of the returningsignal generated by the head wave travelling along the seismic interface. Both P-wave and S-wave energy sourcescan be used.

Reflection Surveying has more recently become available for shallow investigations as the technology has refinedto allow detail within the zone of interest to be revealed. With this approach the seismic signal is recorded atcomparatively shorter horizontal offsets from the source than refraction. The reflected energy is gathered from alldiscrete sub-surface interfaces within the depth to which the source can transmit energy.

Data are gathered along traverses and therefore spatial coverage depends on line spacing. A typical refractionsurvey might take four days per hectare at 10 m line spacing depending on the target depth and resolutionrequired and number of shots per spread. Reflection surveying, requiring more shots per spread, could takesignificantly longer. Whilst time is required to pick seismic arrivals on the refraction records and analyse the dataset, additional time is required to process the reflection seismic data before a record is available for interpretation.

A recent development utilises the ground response to varying frequencies of surface seismic (Rayleigh) waves toinvestigate the shallow geotechnical properties.

Sequence of events

• Whilst pre-survey modelling exercises can be carried out off-site for the refraction to determine whether theparticular feature is theoretically discernible, it is more usual to undertake an initial trial. This enables theoperating parameters to be established for a given site and provides positive proof of the efficacy, orotherwise, of the method. Where specific details of the subsurface are known, a simple two dimensionalmodel along a profile across the site can provide an early view of the potential value of the approach.

• It is particularly important that the objectives of the survey are discussed and agreed with the contractorduring the modelling or trial stage. If the modelling exercise or trial indicates that a survey could be successful,then a full field team may be mobilised to lay out geophones along a profile or series of profiles. Whilst themethod can be utilised in an urban environment, the higher ambient noise levels mean that disused sites aremore likely to produce more noisy data than on greenfield sites.

• The recording equipment is light and easily transported in a van. However if the site is away from levelledtracks or roads an off-road vehicle should be provided to enable access to the survey area. In remote areas, ifdata are to be processed simultaneously with acquisition, a local site hut plus computing facilities in air-conditioned accommodation would be needed and for ground contamination investigations, post-processing inan office is normal.

• It is usual for the Contractor to carry out field work supported by a dedicated assistant working in the localoffice carrying out data reduction for refraction surveys. Reflection data requires a processing unit and, whilstthis can be provided in the field, it is more usual to process data at a processing centre.


• For a survey of large size it will be necessary to arrange access, wayleaves and permitting in advance toensure no hold up to the survey crew. The laying out of geophone spreads, particularly where these arealongside roads, and the use of seismic sources that are audible to the general public (and which in some casescan cause ground damage), may require compensation to be paid.

• Prior to the geophysical acquisition it will be necessary for the survey team (which may be independent of theseismic crew), to mark out on the ground (by pegs or biodegradable paint) the positions of the geophones andseismic source points. Unless existing ground levels are already available, a levelling exercise to obtaincorrected heights for each position will also be required. Permanent reference stations should be establishedoff the area that may be disturbed during remediation or construction.

• Geophone spacing will depend on the specific targets and detail required. 1 m to 5 m separations areappropriate for shallow environmental type investigations for refraction and spreads usually contain 12 or 24detectors. Shot positions depend on source strength, likely depth to refractor and ground resolution required.Shots will be undertaken at both ends of spread and maybe also be within and/or at spread-length distances offthe end of the spread. Approximately 4 to 6 spreads might be achievable each day depending on stationspacing and accessibility.

• Contractor should bring to site a range of source types. Shallow refraction targets can be addressed by shortspreads and a sledgehammer. Deeper targets may require a weight drop (which may by accelerated) or a landairgun. In open country, especially for longer spreads, it may be appropriate to use detonators, a proprietary“shot gun” or small explosive charges set in shallow augered holes.

• The most appropriate surface energy source should be selected having in mind the objectives of the survey,access to the survey site, the proximity of dwellings, services, potential sources of noise and safety issues.Previous examples demonstrating the suitability of the proposed source should be provided.

• Reflection spreads are usually longer and may contain up to 120 channels. Geophones may be placed as closeas 1m with receiving positions being selected at the recording unit to avoid or diminish unwanted shot noise orrefracted arrivals at far range.

• Where it has been decided to utilise energy sources placed in shot holes it may be necessary to employ adrilling rig if ground conditions are too hard for hand auger drilling. It is inevitable that some grounddisturbance will be experienced and the air blast may be offensive (and potentially dangerous) to localresidents. Adequate arrangements, approved by the police if necessary, must be made prior to arrival on sitefor the supply and storage of explosives and detonators.

• Reflection seismic surveys require sufficient experienced personnel to carry out the works in a timely andefficient manner. Where geophone spreads are left on line overnight security along the line, particularly withregard to pre-loaded holes, must be maintained and line guards should be provided for this purpose.

• A micro-processor based field office processing system using industry standard software may be an efficientway to keep up with seismic reflection data acquisition for a large survey. An experienced operator familiarwith the basic principles of data processing and use of the system and software will be required. Two tape-drives, fully compatible with the field format to enable copying of field tapes and an electrostatic plotter capableof quality are integral parts of the system for large high-volume surveys.

• The field processing system can be used for producing analytical displays and print-outs, filtered displays offield records to facilitate rapid assessment of the relationship between shot depth and record quality andpreliminary displays (brute stacks). It may be used not only for assessing the quality of acquired data, butproducing a final record. It can also be used to make copies of field tapes before despatch to main processingcontractor.

• Land survey data should be supplied digitally. The data would include station ID, positional information,geophone and shot location elevations to an agreed datum. Field seismic reflection data will be retained in shotrecord form and passed to the field or office based processing centre in digital form. These data will bereassembled into Constant Mid-Point form through a processing sequence.

• Having acquired the data it is necessary to undertake an evaluation of the results in order for example, todetermine the nature of the geology along each 2D section or to build a 3D image. This work element could beaccomplished by the acquisition or processing contractors or more usually by a specialist in seismicinterpretation. This interpretation may be qualitative but more usually is quantitative and should provideddepths to specific horizons of interest to the environmentalist. It should be followed by careful intrusiveinvestigation to establish ground truth and relate specific sub-surface horizons to events on the seismic record.



Applications

Studies of landfill sites to determine depth and extent.

Thickness of made ground/fill/overburden above bedrock.

Monitoring of fluid level in oil, geothermal and water reservoirs.

Structural characteristics of rock types and their ability to be excavated.

Identification of shallow galleries and partially collapsed mine workings.

Mapping of evaporites and salts beds subject to dissolution.

Detection of gas pockets (in certain situations – check with your geophysical specialist).

Lateral discontinuities and faulting where bedding structures are evident.

Investigation of underground waste sites and estimation of safety factors.

Soil strength parameters.

Limitations

Measurement of acoustic signals requires a quiet environment. The methods are sensitive to microseisms andman-made vibrations that may occur on an active industrial site. If severe these may preclude measurementsbeing obtainable.

To be effective there needs to be a contrast in acoustic impedance between the desired target and host rock/soil,or variations in impedance within the geological structure within which the target is expected. Absence ofimpedance contrast means no surface will be detected.

For refraction the soil/rock seismic velocity must increase with depth for a refractor to be identified.

If strong local bedding dips are present it may be impracticable to image the structure.


Key cost factors

• openness of site and foot access to areas to be surveyed.




• ambient weather - high winds can generate noise on geophones.

• ambient vibration – prevalence of microseisms and/or machinery operating close by, pedestrians, traffic, fastflowing rivers, surf noise on beaches, trees etc.

• degree of processing required.




A typical geophysics team carrying out a seismic survey will comprise between two (for refraction) and up to four(for reflection) experienced personnel plus helpers carrying out the following activities:

service design - one geophysical advisor and, for refraction, access to computing facilities andmodelling software.

field measurements - one geophysicist (party chief), one instrument operator, one surveyor, onelicensed blaster/source operator, plus a number of geophone installers/surveying assistants.

data processing - one geophysicist specialised in processing in addition to above if data to bereduced simultaneously with acquisition.

geophysical interpretation - one geophysical specialist.


It is usual for reflection seismic survey teams to be accompanied full time by a technical representative from thecommissioning organisation. He should be familiar with the overall aims of the investigation, present at thecontractor briefing and available on the crew when it mobilises and thereafter. There may also be the need tosupervise the data processing especially if the company is not familiar with environmental/engineering type data.


Access to the site perimeter at least for the recording vehicle and on-line for a small drilling rig or a seismic sourceunit.

Access within the site and along the survey lines for a man carrying units the size of a medium suitcase.

Ability of ground to support the weight of a man and (if necessary) drilling equipment.

Ease of laying out a grid of stations with appropriate markers (e.g. flags in corn field)






• all physical survey markers to be removed on completion of survey (to avoid ingestion by stock);

• HSE guidelines on use of seismic sources should be followed.













RESISTIVITY SURVEYING

Related techniques and names: A) electrical sounding, electric drilling, Schlumberger sounding, Wennersounding, vertical electrical sounding (VES). B) electrical impedancetomography, sub-surface imaging, electrical imaging, resistivitypseudosection. C) resistivity profiling, constant separation traversing,electrical resistivity traversing, electric mapping or trenching, D) pulledarray continuous electrical profiling/VES.


All resistivity methods employ an artificial source of direct or low frequency current that is introduced into theground through point electrodes, flat contacts or less frequently, porous pots. The resulting electrical potentialchanges in the sub-surface are measured between two other electrodes in the vicinity of the current flow. Inmost cases the current is noted as well. It is then possible to determine the apparent resistivity of the subsurfacewhich may then be converted to true resistivity versus depth.

For the “static” systems two general approaches are used for taking resistivity measurements in the field. With thefirst type of measurement, the centre of the electrode spread remains fixed but the separation of electrodes isprogressively increased until the maximum desired depth of penetration is reached. This method locateshorizontal discontinuities in conductivity and makes it possible to determine their depth. Recent advances in datalogging and analysis using personal computers has enable larger quantities of data to be acquired and processed(inverted) in a given time enabling this method to gain popularity for environmental purposes. Large arrays ofelectrodes can be laid out in line or on a grid and sampled under computer control.

In the second method, the current and potential electrode spacings are fixed and the array of electrodes is movedalong the line of spread with constant separation from one place to another, the apparent resistivities being plottedat the mid-points. These data are contoured over the area of interest. Any body having anomalous conductivitythat is shallower than the depth of maximum effective penetration should be identified as an anomaly.

Continuous profiling systems have been developed by the Danes (PA-CEP/VES), French (CORIM) and most recentlythe Canadians (Ohm-Mapper), which can be coupled behind a mini-tractor or golf buggy to greatly improve speedof data acquisition.

There are three geometrical configurations commonly in use for Environmental and Engineering surveys, Wenner,Schlumberger and Dipole-Dipole with varying benefits (See Reynolds, p433). A typical field survey might takethree to seven days per hectare depending on the configuration; if ground conditions were suitable for the towedsystem a day might be adequate. Additional time is required to process and analyse the data set.

Sequence of events

• A modelling exercise is optionally carried out offsite as a preliminary stage to determine whether thesuspected feature/s is/are theoretically discernible and which geometrical configuration will be most suitable.It is also necessary to evaluate the resistivity contrasts. Models may be simple one dimensional at a point ortwo dimensional along a profile. In the absence of modelling a field trial is usually undertaken.

• If the conditions appear to be satisfactory for using this approach a field team is mobilised to conduct a seriesof acquisition procedures at either selected sounding positions, along a profile or series of profiles or over agrid of points (with base current electrodes in place).

• The equipment is light and easily transported in a car or van. However if the site is away from levelled tracksor roads an off-road vehicle should be provided to enable access to the survey area. In remote areas, if datais to be processed simultaneously with acquisition, a local site hut may be desirable.

• It is usual for the Contractor to carry out field work supported by a dedicated assistant working in the localoffice carrying out data reduction. Field plots (station location and non-terrain corrected anomaly contourmaps and profiles) may be produced and are often available for inspection on a daily basis.

• Unless existing ground levels are already available, it may be necessary for the survey team (usually aminimum of two persons) not only to mark out on the ground (by pegs or biodegradable paint) but also toundertake a levelling exercise to obtain corrected heights for each station.


• Electrodes can be in the form of steel rods, steel plates with bentonite, tin or aluminium foil or, lessfrequently, porous pots. Plates or foil are used when sufficient penetration of a steel rod cannot be achievedand/or when high contact resistances are experienced. The foil is placed in a hole filled with water or coppersulphate solution and covered with soil soaked with copper sulphate solution. The current electrodes aregenerally but not always placed on the outside of the potential electrodes, although the opposite layout istheoretically equivalent. NB Galvanic versus capacitative electrode systems.

• The most common electrode set-up is the Wenner arrangement. Each potential electrode is separated fromthe adjacent current electrode by a distance a which is one-third the separation of the current electrodes. Fordepth exploration using the Wenner spread the electrodes are expanded about a fixed centre, increasing thespacing a in steps. For mapping the spacing remains constant and all four electrodes are moved along theline. The apparent resistivity for each array position is then plotted using the centre of the spread.

• In the Schlumberger configuration, the linear electrode spacing is expanded by increasing the distancebetween current electrodes a or that between potential electrodes b, but only one at a time, during the courseof a measurement. The potential electrodes are assumed to be an infinitesimal distance apart, and observedvalues of potential are adjusted by extrapolation to fit this assumption. In depth probing the potentialelectrodes remain fixed while the current electrode spacing is expanded symmetrically about the centre of thespread.

• Resistivity mapping may be conducted by using a very large fixed separation of the current electrodes (100’sof metres) and the potential pair moved between them, also with a fixed spacing. Apparent resistivity isplotted at the mid-point of the potential electrodes.

• Dipole-dipole arrays are the most expensive of the arrays to run, since all four electrodes are moving alongthe line, but have several advantages. The foremost of these is that all four electrodes are in the local area ofthe station measured and therefore spurious effects that relate to a distant electrode placement are absent.The current electrodes are usually well separated from the potential electrodes. Usually the separations a andb are equal and the distance between the respective pairs is r.

• Where deep soundings or widely spaced current electrodes are required (and especially in arid conditions) itwill be necessary to utilise a generator to provide adequate power for the transmitter. In these surveys aseparate receiver may be employed. Smaller surveys in the moist European environment usually use a singleunit.

• For traversing, apparent resistivity may be displayed on a lap-top computer to identify lateral changes in thesubsurface for given potential electrode spacings (not necessarily the same depth due to lateral changes inconductivity). For soundings a curve of increasing apparent resistivity with depth is produced. Where datashow single anomalous values in relation to adjacent readings these may have to be rejected or the particularreading for that position (any one of the four electrode may have a poor contact) repeated before the dataaccepted.

• Field data should be supplied digitally. The data would include station ID, positional information, electrodeconfiguration and apparent resistivity. This data requires processing and analysis in order to assess the trueground conditions. This work element could be accomplished by the acquisition contractor, but preferably byan alternative specialist.

• Resistivity sounding curves may be interpreted by computer curve matching (there may be more than onesolution). Computer inversion has been developed to enable inversion of Sub-Surface Imaging apparentresistivity pseudo-sections is now standard.

• Evaluation should always be followed by careful intrusive investigation to establish ground truth. If suchinvestigation is not feasible then further modelling exercises may be initiated on each of the perceived discreteanomalies to estimate depth and nature of the variations established in the sub-surface or a particularcausative body.



Applications

Location of natural voids, such as in karst environment, partially fluid filled with sediment and/or liquid.

Studies of landfill sites to determine depth and extent and differences in waste types.

Thickness of made ground, fill, overburden or weathering.

Mapping of perched water tables, depth to ground water and extent of aquifers.


Mapping natural saline wedges, lagoon discharges and contaminated zones (e.g. landfill leachates).

Lateral discontinuities, fissuring and fractured fault zones.

To a lesser extent: Ice and permafrost thickness, ice lenses within permafrost, slope stability and ground failure.

Limitations

To be effective there needs to be a resistivity contrast between the desired target and host rock/soil and variationsin resistivity within the geological structure within which the target is expected; absence of contrast means nodetectable anomaly will exist.

Analysis generally assumes a horizontally layered host medium. Extreme lateral variation in ground surface orsubsurface may preclude meaningful soundings being obtainable.

If strong local topographic variations are present current paths may be so complex that the sub-surface structuremay not be resolvable by Sub-Surface Imaging.

Natural or artificial electrical sources may cause interference.

High voltage cables or other buried cables, water mains or metal pipes may locally preclude valid observations.


Key cost factors• openness of site (especially for towed arrays) and foot access to areas to be surveyed.• topographic variation and/or density of vegetation.• degree of man-made obstructions present• size of area/number of profiles to be surveyed.• station spacing to achieve useable/interpretable data set and depth penetration.• ambient weather – heavy rain or standing water can affect ability to make readings.• degree of analysis and post modelling required.



A typical geophysics team carrying out a resistivity survey will comprise between one and three experiencedpersonnel plus helpers carrying out the following activities:

service design - one geophysical advisor and access to computing facilities and modellingsoftware.

field measurements - one geophysicist and one surveyor or surveying assistant

data processing - one geophysicist in addition to above if data to be reduced simultaneously withacquisition.


environmental assessment - one geophysical advisor.

Depending on changes to the field configurations resulting from the initial results that may be required it may benecessary for the survey team to be accompanied full time by a representative of the commissioning organisation.In all cases, it is recommended that a technical representative from the commissioning organisation, familiar withthe overall aims of the investigation, is present on the first day and then to maintain contact thereafter.



Access to the site and within the site for a person carrying units the size of a medium suitcase.

Ability of ground to support the weight of a person.

Ease of implanting electrodes to ensure good electrical contact and managing extensive electrical cabling.

Ease of laying out a line of stations or grid with appropriate markers.

Ability to avoid laying cables close to or parallel with high voltage power lines due to risk of induction effects.




• the existence of farm stock, which potentially could be hostile, consume/remove pegs or be harmed bycontact with live electrodes.


• survey markers to be removed on completion of survey (to avoid ingestion by stock).

• the use of a generator for powering a transmitter may mean that there is a danger of electrocution. Cautionis required when working with high power electrical equipment.













MAGNETIC SURVEYING

Related techniques and names: ground magnetometry, total magnetic field, magnetic gradiometry,magnetic susceptibility.


Magnetic surveying is a geophysical method that has been utilised by the environmental profession for many yearsto locate sub-surface ferro-metallic objects such as tanks and unexploded ordnance as well as features that modifythe natural earth’s magnetic field. The technique has been refined to reveal small local anomalies in the earth’smagnetic field that result from the contrasting levels of magnetic susceptibility that exist between infilled featuresor structures and the local substrate or bedrock. This effect is principally due to the varying iron content in the soiland rock forming minerals

Traditional total-field magnetic surveying, as used in the exploration industries for structural geology and mineralprospecting, has now been given greater resolution by the development of high resolution of very sensitiveinstruments. Units are often coupled to Differential Global Positioning System units and automatic logging devicesthat enable data to be acquired rapidly on foot and down loaded to lap-top computers for visual presentation.

Processing the field data enables extremely subtle features to be identified and the removal of unwanted noise.With modern equipment and careful field procedures it is now possible to measure the magnetic field changes assmall as one part in 10-11. This enables the detection, not only of small, buried man-made objects, but also subtlefeatures of archaeological significance.

A typical field survey might cover up to ten line Km per day on foot; additional time is required to process andanalyse the data set.

Sequence of events

• A modelling exercise may be carried out off-site as a preliminary stage to determine whether the suspectedfeature with a particular magnetic susceptibility is theoretically discernible. This enables the limit ofdetectability to be calculated for a given site. Models may be simple two dimensional along a profile acrossthe site or a three-dimensional model plotted as a map of expected magnetic change over an area.

• If the modelling exercise indicates that a survey could be successful, a field team is mobilised to acquire overa grid of points (or along a profile or series of profiles). This can be accomplished in an urban environment, aswell as in a brownfield or greenfield site.

• The equipment is light and easily transported in a car or van. However if the site is away from levelled tracksor roads an off-road vehicle should be provided to enable access to the survey area.

• It is usual for the Contractor to carry out field work supported by a dedicated assistant working in the localoffice carrying out data reduction. Field plots (station location and non-terrain corrected anomaly contourmaps and profiles) are produced and are often available for inspection on a daily basis.

• It is not usually necessary for the survey team to undertake a levelling exercise as the surveys are generallyonly concerned with the position of subsurface features. If an automatic positioning system is being usedthere may also be no need to mark out stations on the ground (by non-magnetic pegs or biodegradable paint)although some form of visual location will be required. Survey observations may be as close as 0.25 m onlines at 1m interval and 40,000 readings can be accomplished in a day for such archaeological surveycoverage with an auto-recording system depending on grid size and accessibility. 1 m to 2.5 m grids areappropriate for environmental type investigations.

• Various types of magnetometer are available, the earlier Fluxgate and Caesium vapour (10 readings/sec)being most usual for environmental and archaeological work. For detail surveys it is usual to use two units,one above the other, to measure the vertical gradient. In this case no base readings are required as thegradient is independent of diurnal variation.


• For a large area of survey where total field is being recorded a local base station should be established. Thisshould be located away from magnetic targets or magnetic noise (e.g. pylons) and where the local fieldgradient is relatively flat. As the survey progresses the base station is re-occupied every 30 or 45 minutes tocompile a diurnal curve for later correction of field readings against time of observation. Alternatively aseparate continuous recording unit may be installed on the base station.

• Daily production may be displayed on a simple anomaly plot and used to identify specific station readingswhich may be in error or indicate a local anomaly. These readings should be repeated the following daytogether with adjacent stations to check that data will fit in with the set.

• “Terrain corrections" may need to be estimated when the ground over which the survey is conducted is bothmagnetically and topographically rough. If the rough terrain is made up largely of low-susceptibilitysedimentary rocks there will be little or no distortion of the earth’s magnetic field.

• Field data should be supplied digitally. The data would include station ID, positional information, totalmagnetic field for each given sensor and magnetic gradient. Data may require processing in order to removehigh frequency noise and remove diurnal variation.

Results should be evaluated to identify features of potential concern. This could either be accomplished by theacquisition contractor or, preferably, by an alternative specialist. This may be qualitative or quantitative andshould always be followed by careful intrusive investigation to establish ground truth. If such investigation is notfeasible then further modelling exercises may be initiated on each of the perceived discrete anomalies to estimatethe depth to the causative body. The intensity and direction of any permanent (natural remanent) magnetisationwill affect the validity of the model which is produced.


Applications

Location of man-made ferro-magnetic objects such as tanks with or without contents and underground metal pipes(and their joints).

Studies of landfill sites to assess history and extent.

Location of unexploded ordnance (bombs and shells)

Karst collapses in the Carboniferous; clay infilled depressions in the Chalk topography.

Sub-surface bridged and partially backfilled or semi-collapsed mine shafts

Identification of buried steel drums.

Lateral geological discontinuities (such as dikes) and faulting in specific circumstances.

Limitations

Measurements are not possible during periods of intense sunspot activity when magnetic storms occur.

Due to the sensitivity to all ferro-metallic objects, on brownfield sites it will be necessary to set the sensor at asuitable height above ground to limit sensitivity to likely noise.

High voltage cables, fences, armouring or proximity to metal framed buildings with their attendant magnetic fieldsmay preclude meaningful measurements being obtainable.

To be effective there needs to be a magnetic susceptibility contrast between the desired target and host rock/soilor variations within the geological structure within which the target is expected. Absence of magneticsusceptibility contrast may mean no anomaly will exist unless a specific target has its own remnant magnetism.

If strong local topographic variations are present and sub-surface is highly magnetic it may be impracticable toassess the terrain corrections required to fully correct the observations.



Key cost factors





• degree of post-survey modelling required.

Personnel Requirements


A typical geophysics team carrying out a magnetic survey will comprise between one and three experiencedpersonnel carrying out the following activities:

service design - one geophysical advisor with access to computing and software modellingfacilities if necessary.

field measurements - one observer and one surveyor or surveying assistant

data processing - one geophysicist in addition to above with access to computing and softwarefacilities if data to be reduced simultaneously with acquisition.



It is not usually necessary for the survey team to be accompanied full time by the commissioning organisation. Itwill, however, be necessary for a technical representative from the commissioning organisation, familiar with theoverall aims of the investigation, to be present on the first day and then to maintain contact thereafter.


Access to the site and within the site for a man carrying a unit the size of a medium suitcase.

Ability of ground to support the weight of a man

Ease of laying out a grid of stations with appropriate markers.







• tale care to avoid high sensor rods from touching overhead cables.



GROUND PENETRATING RADAR SURVEYING

Related techniques and names: radar, georadar, GPR, ground probing radar, sub-surface radar


Ground Penetrating Radar has developed rapidly in the last few years as a geophysical tool to identify very shallowsub-surface structures on environmental, archaeological and engineering sites. The method utilises the fact thatobjects or interfaces that have significantly contrasting electromagnetic properties will cause a partial reflection orscattering of an impinging radiowave signal.

Whilst similar to echo-sounding or reflection seismic profiling the ground penetrating radar produces aelectromagnetic pulse that travels though a medium depending on its conductivity and is reflected at dielectricpermittivity changes. However there is a danger in making the comparison of radargrams to seismograms as thevector nature of the former may be overlooked and incorrect assumptions made about the way that theradiowaves behave in geologic media. Nevertheless seismic data processing can be used effectively in most casesalthough the electromagnetic polarisable characteristics of the radiowaves are more analogous to seismic shearwaves than to pressure waves.

The electromagnetic properties of materials are related to their composition and water content, both of which exertthe main control over the speed of radiowave propagation and the attenuation of electromagnetic energy. Polarice and dry sand are virtually transparent to radiowaves. Other materials such as water-saturated clay andseawater either absorb or reflect the signals to such an extent that they are virtually opaque. For geologicalapplications, where depth penetration is more important than very fine resolution, frequencies generally less than200 MHz are used. For engineering applications or non-destructive testing, frequencies of 200 MHz to 1.5 GHz arethe norm. This range enables the detection of rock structure in solid rock to depths of greater than 20 m,identification of underground voids (both natural and man made), definition of contamination plumes, fine detailsof road surface de-lamination and within engineered structures.

A radar system comprises a signal generator, transmitting and receiving antennae and a recorder that may havedigital recording and/or hard copy output. The antennae are usually in contact with the ground and are movedalong a straight line to produce a continuous output of reflected signals from the subsurface. The data arepresented in real time as a two-dimensional record of two-way travel time against distance. Some advancedinstruments have additional computing capabilities that provide data processing facilities, both whilst acquiringdata in the field and post recording.

A typical field survey might comprise ten line Km per day; additional time is required to process and analyse the

data set.

Sequence of events

• There are many manufacturers of radar equipment addressing different technical situations. Likewise therehas been a growth in companies offering ground radar surveys. The technology is advanced but because theequipment can be hired easily and operated with only minimal training/understanding of the technique, thequality of the results may not be high. To obtain appropriate results and for a full understanding ofconstraints in the use of the technology it is wise to check the experience of the operator before engaging acompany’s services.

• Whilst modelling is not undertaken as a preliminary stage it is necessary to consider whether the site andtargets are amenable to investigation/location by GPR. In particular, if clay is present to any degree or if thegroundwater is likely to be conductive and at a shallow level then the chance of reasonable penetration isslight. A small trial in selected parts of the site is recommended before the main acquisition commences.

• If the trial indicates that a survey could be successful, a field team is mobilised to conduct a series of profiles.This can be accomplished in an urban environment, inside or outside buildings, as well as in a brownfield orgreenfield site. An early decision is required as to which frequency of transmitter is to be used. This willdetermine not only likely penetration but also degree of resolution.



• Aside from field work, it is usual for the Contractor to provide draft data presentation (without elevations).Processing of data will be required post-acquisition to improve the data quality, insert the elevation data andproduce a useable section.

• Unless existing ground levels are already available, it will be necessary for the survey team, not only to markout way points on the ground (by pegs or biodegradable paint), but also to undertake a levelling exercise toobtain corrected heights along each traverse. This will enable the data to be height corrected to remove theground variation distortion on final records.

• For a large area of survey several units may be operated simultaneously. In these circumstances, althoughthe data may be recorded digitally enabling subsequent playback at modified outputs, it is recommended thata uniform presentation style be adopted enabling field records to be directly compared and interpreted.

• Signal transmission can usually be triggered at set distance or at regular time intervals Whilst the latter isacceptable for reconnaissance in open, smooth sites, the former is preferred as the horizontal scale of printedrecords is then uniform. The antennae are usually dragged or wheeled along a survey line with referencemarks being inserted by the operator, if necessary, for future correlation with site features. Record length isset to encompass the depth to which reflections are achievable and the detail required.

• Whilst units which combine transmitter and receiver antennae are preferable for profiling work there are alsosystems which operate with separate units. These provide the opportunity to undertake wide angle reflectionand refraction (WARR) measurements that can be used in areas of flat lying reflectors to measure the velocityof the electromagnetic wave. This information is needed to convert the time section to depth and should beobtained at discrete points within a survey where changes in sub-structure have been observed.

• Problems may be experienced in transmitting the signal into the ground in local parts of the site. A decisionwill have to be made as to whether a change in antenna or acquisition parameters will improve this or whetherthe survey will have to be abandoned. Where a change is dictated then readings should be repeated over theoriginal section for comparison and subsequent analysis.

• Where data quality is good and reasonable penetration is obtainable, it is possible to operate ground radar in aCommon Mid-Point mode using multiple channels, as with reflection seismic. This should only be attemptedby a skilled geophysical team, as the geometry needs to be fully understood. The methodology has now beenextended to acquire three-dimensional data sets for full site assessment.

• Data should be supplied digitally. The data would ideally include station ID, positional information and theradar data. Data can be processed using specialist GPR processing software or using standard seismicreflection processing software.

• Having acquired the data it is necessary to undertake an evaluation of the results in order for example, toreveal hitherto unknown voids or suspected underground contamination. This work element could beaccomplished by the acquisition contractor or by an alternative specialist. This may be qualitative orquantitative and should always be followed by careful intrusive investigation to establish ground truth.


Applications

Location of shallow man-made voids such as cellars, tanks and water cisterns.

Studies of existing landfill sites to determine depth of capping and extent.

Thickness of made ground/fill in uniform, non-clay deposits.

Mapping and monitoring of contaminants in groundwater.

Detection of natural cavities and fissures.

Sub-surface bridged, open and partially backfilled or semi-collapsed mine shafts


Mapping of superficial deposits and archaeological features.


Lateral discontinuities and faulting.

Ice and permafrost thickness, ice lenses within permafrost.

Location of buried fuel tanks and oil drums.

Limitations

The presence of clay or any other electrically conducting medium will severely preclude the recovery of usefuldata. Metallic screen at ground level or close re-bars in concrete may prevent penetration, depending on antennaefrequencies.

Transmitters and receivers have limited directivity and therefore signals that are recovered out of the plane of theintended section (overhead gantries, adjacent walls) may cause severe interference and subsequent problems ininterpretation. In constricted areas, shielded antennae should be used.

Multiple reflections between subsurface layers and interaction between the antennae and the immediate above–surface environment may produce ringing or an overlong pulse which obscures the required detail.

To be effective there needs to be a permitivity contrast between the desired target and host rock/soil or variationsin permittivity within the geological structure in which the target is expected. Absence of contrast means thestructure will not be resolved.

If strong local topographic variations are present along the survey line it may essential to input the elevationsbefore any attempt is made to interpret the data.





• number of different frequency antennae to achieve useable/interpretable data set.

• complex sub-surface may require slow profiling speed to resolve structure

• degree of post-survey processing required.



A typical geophysics team carrying out a GPR survey will comprise between one and three experienced personnelcarrying out the following activities:

service design - one geophysical advisor.

field measurements - one qualified operator and optionally one surveyor or surveying assistant

data processing - one geophysicist and second system if data to be processed simultaneouslywith acquisition.

geophysical interpretation - one geophysical specialist with optional access to computing facilities.


It may not be necessary for the survey team to be accompanied full time by the commissioning organisation. Itwill, however, be necessary for a technical representative from the commissioning organisation, familiar with theoverall aims of the investigation, to be present at the trial and on the first day of full survey and then to maintaincontact and view records regularly thereafter.


Access to the site and within the site for a man carrying a unit the size of a medium suitcase.

Ability of ground to support the weight of a man







• when working within buildings the stability of the structure should be assessed.






Civil Engineering Applications ofGeophysical InvestigationTechniques (in production)









ELECTROMAGNETIC SURVEYING

Related techniques and names: ground conductivity survey, frequency-domain EM survey, time-domain(TDEM) survey, pulse-transient (TEM), very early time-domain (VETEM),controlled-source audio magneto-telluric (CSAMT), very low frequency(VLF) mapping


Electromagnetic surveying is a geophysical method that has been utilised by the environmental profession formany years to locate hazardous materials by measuring changes in the ability of the sub-surface to modify anapplied electromagnetic field.

Traditional electromagnetic surveying as used in the mineral exploration industry has developed greatly in the last10 years and has the broadest range of instruments in geophysical methods with a very wide range ofapplications. Highly portable instrumentation has been developed enabling reconnaissance surveys to beconducted swiftly. These systems are of particular value for shallow depth environmental studies as the process ofinduction does not generally require direct contact with the ground. This enables the detection, not only ofunderground voids (both natural and man made) but also the monitoring of contaminants from waste lagoons andleaking tanks, for example.

Frequency-domain instruments use either one or more frequencies. Time-domain equipment makesmeasurements as a function of time. Some systems use natural ground signals and are regarded as passive.Active systems use an artificial transmitter which can either be at a considerable distance away from the site or inimmediate juxtaposition to the receiving unit.

Survey methods vary so widely that it is not possible to indicate how long a “typical” field survey might take.However for the more usual portable reconnaissance systems 800-2,500 stations per day might be the norm;additional time is required to process and analyse the data set.

Sequence of events:

• For certain of the methods a modelling exercise may be optionally carried out offsite as a preliminary stage todetermine whether the suspected feature is theoretically discernible. This enables the limit of detectability tobe calculated for a given feature at a particular site. Models may be simple two dimensional along a profileacross the site or a three dimensional model plotted as a map of expected values over an area.

• If the modelling exercise indicates that a survey could be successful, a field team is mobilised to conduct aseries of acquisition procedures as indicated below using one or a number of differing approaches to ensurethat sufficient data is acquired over a grid of points, along profiles or at a sounding location. In certaincircumstances this can be accomplished in an urban environment, as well as in a brownfield or greenfield site.


• It is usual for the Contractor to carry out field work supported by a dedicated assistant working in the localoffice carrying out data reduction. Computations for some of the sounding methods are complex and requireconsiderable computer time to produce an acceptable depth (inversion) result.

• It will not usually be necessary for the survey team to undertake a levelling exercise although it should benoted that VLF measurements can be adversely affected by topography. However the survey grid will need tobe marked out on the ground (by non-magnetic pegs or biodegradable paint). Specific requirements willdepend on the method adopted.

• The most commonly-used frequency-domain EM surveying method in Environmental and engineeringgeophysics is the moving-source dual-coil method. Two separate coils are connected by a reference cable;one coils serves as a transmitter to generate the primary field and the other acts as a receiver. Differingseparations and coil orientations are used to penetrate to different depths with the mid-point being the plottedpoint of the observation. Single man systems have the coils mounted on the ends of a 2 m boom andsurveying takes place using orthogonal positions of the boom at each location on a grid or along a profile.


• For a time-domain sounding a large direct current is passed through a large ungrounded loop transmitter for aperiod of 20 to 40 milliseconds. The applied current is then terminated and the presence of any surface currentsinduced in the ground recorded by the transient voltage in the same or a separate loop at discrete timeintervals. As the surface currents dissipate a decreasing magnetic field is experienced and the resultingdecaying voltage is recorded. This is repeated many times at a given location with all the data being loggedautomatically. Various types of time-decay plots are used to characterise the resulting sounding data forenvironmental purposes using PC software. Up to 50 soundings of 25 –50 m depth with high vertical resolutioncan be achieved per day for environmental purposes.

• Profiling surveys are accomplished with the time-domain approach by establishing a large ungroundedtransmitter loop with the long axis parallel to any geological strike. A small receiver coil is moved alongtransects perpendicular to the long axis of the transmitter to obtain profiles of the measured parameters as afunction of distance. Data can be plotted as profiles or a grid developed utilising a loop size appropriate to thedepth being investigated.

• The use of Very Low Frequency (VLF) military transmitters around the world for the reconnaissance of nearsurface effects has been established for many years. The transmitters propagate powerful horizontal plane EMwaves which are modified by local conducting ground conditions that can therefore be specially mapped. Surveyprofiles are conducted along the line of the magnetic vector for a given transmitter (of which there are currentlyeleven); two orthogonal electric and magnetic sensors are used to measure the electrical (R) and magnetic (EM)components which relate to the near-sub-surface site conditions (approximately 2 –5 m).

• The magneto-telluric (MT) method uses measurements of both the electric and magnetic components of thenatural time-variant fields generated as a consequence of the presence and fluctuation of the earth’smagnetosphere. Natural-source MT method uses 0.001 to 19Hz frequencies, audio-frequency systems (AMT)operate within 10Hz to 10kHz. A controlled-source system (CSAMT) operating from 0.1 to 10kHz has recentlybeen developed for geotechnical and environmental investigations. A loop or grounded dipole is used as atransmitter off site with two orthogonal electric and three orthogonal magnetic sensors to measure thehorizontal electrical and total magnetic components and build sounding curves to depths of the order of 300 m.

• Depending on the requirements of the survey it may be necessary to use two differing EM units. These willneed calibrating against each other to ensure that data can be merged from both units. Duplicate readings withboth should be taken on selected stations to determine comparability of systems at the same coil spacing.

• Data should be supplied digitally. The data would include station ID, positional information, observed valuesand topography (if recorded).

• Having acquired the data it is necessary to undertake an evaluation of the results. This work element could beaccomplished by the acquisition contractor or by an alternative specialist. This may be qualitative orquantitative and should always be followed by careful intrusive investigation to establish ground truth. If suchinvestigation is not feasible then further modelling exercises may be initiated on each of the perceived discreteanomalies to estimate the depth to the causative body (or cavity).


Applications

Location of man-made features such as cellars, tomb chambers, tanks and steel drums with or without contents.

Studies of landfill sites to determine depth, extent and leachate leakage.

Thickness of made ground/fill/overburden.

Monitoring migration and mapping extent of conductive contaminant plumes.

Identification of clay filled sinkholes (dolines) and other karst features in Carboniferous, Cretaceous and Tertiarylimestones.

Sub-surface bridged, open and partially backfilled or semi collapsed mine shafts

Mapping of shallow galleries and partially collapsed mine workings.

Mapping of brine contamination of aquifers.

Mapping of saline-freshwater interfaces in coastal regions.

Groundwater and geothermal resource investigations.

Locations of pipes and culverts.


Lateral sub-surface discontinuities and faulting.

Mapping extent of frozen and unfrozen ground and identifying massive ice within section.

Limitations

Ambient electrical noise from AC power cables and VLF transmitters

Live electrical cables that produce a signal at a specific frequency that may be removable.

Static cultural noise from pipes (if these are not the “target”), metal fences or other utilities.

Existence of metal structures above, around or beneath the ground (other than target)

In open environments wind may cause motion of magnetic field sensors within earth’s magnetic field.

Natural geomagnetic signals may cause interference at low frequencies (less than 1Hz); distant lightning dischargesproduce sferics which interfere in the 6-10Hz band.

To be effective there needs to be a conductivity contrast between the desired target and host rock/soil or variationsin density within the geological structure within which the target is expected; absence of conductivity contrastmeans no anomaly will exist.

If strong local topographic variations exist or the host sub-surface geology is not near horizontal, it may beimpossible to assess the effect or model the sounding to produce a reasonable interpretation.


Key cost factors





• ambient weather – excessive rain can affect ability to make readings as many instruments are not weather-proof.

• degree of pre and post modelling required.



A typical geophysics team carrying out an electromagnetic survey will comprise between one and three experiencedpersonnel plus helpers carrying out the following activities:

service design - one geophysical advisor and/or access to computing facilities and modellingsoftware.

field measurements - one instrument operator or geophysicist and one surveyor or surveying assistant

data processing - one geophysicist in addition to above with access to computing facilities andsoftware if data to be reduced simultaneously with acquisition.



Depending on changes which may be required to the field configurations resulting from the initial results it may benecessary for the survey team to be accompanied full time by the commissioning organisation. In all cases it isrecommended that a technical representative from the commissioning organisation, familiar with the overall aims ofthe investigation, is present on the first day and then to maintain contact thereafter.



Access to the site and within the site for a man carrying a unit the size of a large suitcase.


Ability of ground to support the weight of a man.

Space to lay out large/medium size ground loops and location for transmitter in case of TEM method.





• when working within buildings the stability of the structure should be assessed.



• the use of a generator for powering a transmitter may mean that there is a danger of electrocution. caution isrequired when working with high power electrical equipment.




Civil Engineering Applications ofGeophysical InvestigationTechniques (in production)








4.2 - Selected photographs of investigation methods

Site investigation methods: trial pits

Plate 1 - trial pits can be hand dug, but the usual method is to use hiredmechanical plant with a skilled operator. Plate 1 shows a backactor excavatorwith an extendable arm capable of digging to around 5 m.

Plate 2 shows a slew boom excavator capable of greater depth, power andmanoeuvrability.

Note The utmost care should be taken by personnel working alongside trial pits as the forces operating on the sides of agradually deepening pit as spoil is piled above are immense and collapse can be sudden and catastrophic. In both of the casesshown in Plates 1 and 2, the surface concrete and ground conditions were such that it was safe to approach the trial pit sides.

Site investigation methods: drilling techniques

Plate 3


Plate 4

Plates 3 and 4 show cablepercussive (“shell and auger”) rigswith casings and associatedmaterials.



Plate 6

Plates 5 and 6 show large rigsemploying rotary coringtogether with associated plantneeded for their operation.

These rigs can usually alsooffer rotary drilling and downthe hole hammer techniques.They can also sometimes offerauger drilling techniques,depending on their precisedesign.

Plate 5



Plate 7 shows a small rig using a combination of hollow stem auger (HSA) andcontinuous flight auger (CFA) techniques. Both CFA and HSA augers lie on theground nearby (CFA in operation).

Plate 8 shows CFA in operation and Plate 9 shows HSA in operation. Thesesmall rigs can sometimes also offer rotary coring, rotary drilling and down thehole hammer techniques, depending on their precise design.


Plate 10 shows hand-heldwindow sampling equipment –the sampler has been drivenfully into the ground.

Plates 11 and 12 show rigdeployed window sampling.



4.3 - Choosing an intrusive investigation method

Intrusive methodsinstructions for using this table (see also Text Supplement 4.4 – Worked example)1 identify the site specific soil/rock conditions and the most appropriate intrusive methods;2 identify any site specific special situations and the most appropriate intrusive methods;3 identify any site specific operational issues and the most appropriate intrusive methods;4 discuss your specific requirements with your chosen drilling contractor(s);5 if no suitable methods remain, consider using non-intrusive methods (see Chapter 4 of Volume I) or modify the

investigation design (e.g. avoid penetrating through an aquiclude or move boreholes away from areas where overheadclearance is restricted).

√√√-

method should be suitablemethod may be suitable depending on working methods adoptedmethod is unlikely to be suitable

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and

asso

ciat

edm

etho

ds

Coarse and/or heterogeneous fill/made ground √√ √ √ - √ √ - √ √ √

Fine homogeneous fill/made ground √√ √√ √ - √ √√ - √√ √√ √√

Unconsolidated sands √ √ - - √ √√ - √ √ √

Unconsolidated gravels √√ √ - - √ √ - √ √ √

Boulders and cobbles and boulder clays √√ √ √ - √ √ - - - -

Soft sedimentary (e.g. clay, marl, shale, sandy clays) √√ √√ √√ - √√ √√ - √√ √√ √

Medium sedimentary √ √ √√ √√ - - √ √ √ -

Strong sedimentary (e.g. limestone, dolomite, grit) - - √ √√ - - √√ - - -

Soi

l/R

ock

con

dit

ion

s

Metamorphic (e.g. slate, marble, schist, gneiss, quartzite) and igneous(e.g. gabbro, dolerite, basalt, granite)

- - √ √ - - √√ - - -




√√√-



Tri

al p

its

Cab

le p

ercu

ssiv

ebo

reho

les

Rot

ary

cori

ng

Rot

ary

dril

ling

CF

A

HS

A

Dow

n th

e ho

leha

mm

er

Win

dow

sam

plin

g

Pro

bing

Han

d au

ger

and

asso

ciat

edm

etho

ds

Penetrating through an aquiclude into an aquifer.1 - √√ √ √ √√ √√ √√ - - -

Drilling into ground containing asbestos/highly odorous wastes/highgas/vapour concentrations)

√ √ √ - √ √ - √ √ √

Sampling to USEPA protocols is needed - - √ √ √ √√ - √ √√ -

Robust groundwater/gas monitoring installations needed - √√ √√ √√ √√ √√ √√ √ √ -

Supplementary groundwater/gas monitoring installations are needed √√ √ - - √√ √ - √√ √√ √

Large quantities of soil/water samples are needed √√ √√ √√ - √√ √√ - √ √ -

Archaeological features √ √ √ √ √ √ √ √ √ √

Sp

ecia

l sit

uat

ion

s

Sensitive ecological habitats - √ √ √ √ √ √ √ √ √√

Sit

esp

eci-

fic Access within the site is constrained by buildings, structures etc - √ √ √ √ √ √ √√ √ √√

1 note that it may be necessary to use two drilling techniques in combination and also to use robust bentonite seals between horizons.




√√√-



Tri

al p

its

Cab

le p

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ssiv

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les

Rot

ary

cori

ng

Rot

ary

dril

ling

CF

A

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A

Dow

n th

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leha

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er

Win

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sam

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Pro

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Han

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Access within the site is constrained by dense non-protected vegetation √√ √ √ √ √ √ √ √√ √√ √√

Investigation locations are close to temporary above ground structures(e.g. vehicles, portacabins etc)

√ √ √ √ √ √ √ √√ √√ √√

Investigation locations are close to permanent buildings/below groundstructures (e.g. footings of buildings/plant/services, archaeologicalfeatures etc)

√ √ √ √ √ √ √ √√ √√ √√

Overhead clearance is restricted √ √ √ √ √ √ √ √√ √√ √√

Members of the general public are in the vicinity of investigationlocations (temporarily/permanently)

√ √ √ √ √ √ √ √√ √√ √√

Investigation locations are close to livestock √ √ √ √ √ √ √ √ √ √

Vehicles will need to pass over the finished installations (e.g.operational sites/agricultural land).

√ √ √ √ √ √ √ √ √ √


4.4 - Worked Example

Scenario

A series of seven groundwater monitoring installations were needed within a small (2 ha) busy industrial unit wherebuildings and plant were closely spaced and vehicle movements were frequent. Two of the borehole locationsneeded to be close to offices where people work for most of the day and others needed to be sited in tight spacesbetween tanks, vehicles and walls. An old BGS borehole log for an area within the site recorded 5 m of very sandyclay overlying clay bedrock with groundwater at 2.5 m corresponding to the approximate level of a nearby river. Itwas decided that groundwater monitoring installations to 4 m would be needed, this depth allowing approximately a1.5 m water column, which would be sufficient for the quantity of water samples, needed. The information on thenatural ground conditions provided by the borehole log on the site had been confirmed at shallow depths during thesite reconnaissance visit, when open excavations around a sewer repair were observed. The made ground wasexpected to comprise reworked clay and, in some locations, pulverised fuel ash (PFA) that was imported at the timeof the site’s redevelopment. It was suspected that small amounts of asbestos insulation were present in the PFA.

Choice of investigation method

1 Identify the site specific soil/rock conditions and the most appropriate intrusive methods;

• Made ground = reworked clay and PFA. Natural ground = sandy clay overlying clay bedrock. The mostsuitable methods = Trial Pits, Cable Percussive, HSA, Window Sampling and Probing. Unsuitable methods =Rotary Drilling and Down the Hole Hammer.

2 Identify any site specific special situations and the most appropriate intrusive methods;

• Drilling into ground containing asbestos. A number of methods may have been suitable, depending on theworking methods adopted. Trial Pitting was identified as an unsuitable method.

3 Identify any site specific operational issues and the most appropriate intrusive methods;

• Access constraints (buildings, tanks), locations next to buildings, members of the general public in the vicinity ofinvestigation locations and vehicles needing to pass over the finished installations. The most suitable methods =window sampling and hand auger/associated methods.

4 Discuss your specific requirements with your chosen drilling contractor(s);

• The project manager discussed the site context, ground conditions and technical objectives of the siteinvestigation with a drilling contractor, who suggested that, of his two suggested methods (window samplingand hand augering) hand-deployed window sampling be used. The contractor advised that hand auger methodswould not achieve the required depth.

• The contractor estimated that it would take one long day to complete the seven installations, together withbreaking out of concrete at nearly all of these which was scheduled to be completed first (using hand-heldequipment), before workers arrived at the industrial unit in the morning. In addition, as the method was quick,it was planned that the two boreholes close to offices would be completed during the workers’ lunch break. Asthe diameter of the largest samplers was only 50 mm, the amount of surface concrete broken out was minimaland “stop-cock” type covers with neat concrete repair established flush with ground level were chosen as thesewould not obstruct vehicle movements.

• The detailed method statement included for safe investigation in those areas where small amounts of asbestosinsulation were expected in the fill.


4.5 – Site Investigation Preparation and Implementation Checklist

Site Investigation Preparation and ImplementationIssues

Comments

Has the date that work will start and its duration been discussed andagreed with the client contact?

Will Permits to Work need to be obtained?

Will security badges etc need to be worn by personnel and how arethese obtained?

Have the permitted site working hours been agreed with the site?

Can a key to the site gate be held by site investigation personnel andif so, who will be responsible for this and its safe return?

Will the site contact need/wish there to be an inaugural site meetingand what will be the impact on the intended organisation of the partiesinvolved?

Can the site provide a secure and suitable office and storage area foruse by site investigation personnel and can a refrigerator be usedtemporarily in this for the storage of samples (if needed)?

Can the site provide an appropriate “washdown area” for equipmenttogether with nearby power and clean water supplies?

Are site skips appropriate for waste arisings from the siteinvestigation and if not, where can site investigation skips be stored?

Will the client and/or site contact need a set of borehole keys?

Will the client and/or site contact wish to inspect the site investigationlocations and condition of the working areas after the work hasfinished?

What needs to be done to comply with the requirements of CDM,COSHH and other Health and Safety legislation?

Cli

ent

and

Sit

e C

omm

un

icat

ion

s

Who needs copies of contact names and telephone numbers etc forparties involved in the investigation?

Have copies of the contractors’ relevant Risk and COSHHassessments and Health and Safety Plans beenrequested/received/approved?

Are the necessary personal protective equipment and other health andsafety equipment (e.g. monitors) available and in good workingorder?

Are the locations of all underground services/utilities known anddrawings available?

Will the work have health and safety implications for the generalpublic and, if so, what are the implications?

Will measures be needed to protect ground surfaces and preventfugitive dust, groundwater, soil arisings and/or odours?H

ealt

h a

nd

Saf

ety

Issu

es

Are sufficient appropriately qualified and skilled staff membersavailable for the investigation?



Comments

What information will need to be provided to ensure that site staff areproperly briefed (e.g. technical objectives, expected conditions, clientcontact details and project set-up, site drawings, health and safetyissues, personal protective equipment needed, dates, times, contractorand other contact details etc.)?

Are all third parties contractors available - including all individualsnamed in contract documents (e.g. cable tracing, drilling andexcavation contractors, waste management/skip hire, laboratory,hand-digging crew, re-instatements crew, surveyors)?

What is the information that will need to be provided to these thirdparties to ensure that they are fully briefed and prepared (technicalspecification, health and safety issues, personal protective equipmentneeded, dates, times, contact details etc.)?

Will the arrival on site of contractors need to be staggered to allowseparate briefings or is it better that they arrive together for oneinaugural meeting?

Are site access gates and turning circles wide enough to allow allplant and vehicles into the site?

Are all general parts of the site that need to be investigated accessibleto plant and vehicles?

Is it physically and otherwise possible to establish site investigationlocations in the required positions?

What is the best system for executing the site investigation locations(e.g. (i) start at one end of the site and progress systematically -efficient but risks entailing “gaps” if progress is slow, or (ii)“leapfrog” between locations – involves greater plant movements butensures general overall coverage if progress is slow or if theinvestigation is curtailed for any reason).

Will any earth/waste mounds/concrete security blocks on site need toby moved or vegetation cleared?

Will topographic survey work need to be carried out at the start of theinvestigation, at the end or both?

Will services locations need to be checked as a self-containedexercise before drilling and excavation works begin or will the abilityto check for these be needed throughout the investigation in the eventthat locations need to be moved?

Will services clearance need to be confirmed by hand-digging?

Will surface concrete need to be broken as a self-contained exercisebefore drilling and excavation works begin or will the ability to breakconcrete be needed throughout the investigation in the event thatlocations need to be moved or sub-surface concrete is encountered?

What borehole covers and re-instatement works will be needed?

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Will measures be needed to manage water and arisings as trialpits/boreholes are excavated/drilled?



Comments

What waste management measures will be needed (solid and liquidarisings from excavations, drilling and purging exercises)?

Are all portacabins, first aid facilities, site toilets, sample/equipmentstorage facilities etc that are needed available?

What special storage facilities are needed for samples to maintain thecorrect temperature, security etc)?

Will any cover/reinstatement materials (e.g. gravel, sand, scalpingsetc) be needed, when should they arrive on site and where should theybe stored?

Will any ropes, cones, barriers, warning signs be needed?

Will any couriers that are needed to collect samples for delivery to thelab need to be booked provisionally?

What referencing system will be used for the investigation locationsand samples?

Will any photographs need to be taken during the investigation (e.g.“general” ones of the site, “before and after” ones at investigationlocations etc)?

If the site is near to surface water features, will the level of these needto be recorded?

What other on-site measurements will be needed?

What arrangements will need to be made forskips/portacabins/equipment etc to be collected after the siteinvestigation is finished?

Op

erat

ion

al a

nd

Tec

hni

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ssu

es # ###

What is the priority for “nice to have” items if contractors are on“Standing Time” or if the supervising scientist(s)/engineer(s) havefree time for some other reason?

Might there be the opportunity/the time to interview personnel/thegeneral public on site who would have knowledge that couldsupplement the desk study findings?

What feedback to the project manager will be needed from the on-sitestaff during the site investigation period?

How much can the supervising scientist/engineer divert from theoriginal site investigation design, brief and budget, without the projectmanager’s approval, if conditions on site change or are found to bedifferent to what was anticipated?

Are any of the third parties ones with whom the project manager isunfamiliar and, if so, is there a need formally to monitor performanceduring the site investigation?

What general lines of communication need to be established betweenon-site staff, contractor, consultant, regulator, site owner and sitecontact to deal with everyday issues?

Div

isio

n o

f R

esp

onsi

bili

ties

an

d O

ther

Iss

ues

How is this to differ in the event that problems occur on site, workprogresses at a different rate to expected, the client/site contactexpresses any dissatisfaction etc?



Association of Geotechnical and Geoenvironmental Specialists. Guidelines for Combined Geoenvironmentaland Geotechnical Investigation (2000).

British Drilling Association (Operations) Ltd, Essex. Guidance Notes for the Safe Drilling of Landfill andContaminated Land.

British Standards Institution Code of Practice for Site Investigations. BS5930: 1999.

Construction Industry Research and Information Association (1995) Remedial Treatment for ContaminatedLand. Volume III: Site Investigation and Assessment.

Construction Industry Research and Information Association Special Publication 103 (1996) RapidCharacterisation of Contaminated Sites Using Electrical Imaging.

Driscol, F. G. (1986) Groundwater and Wells. Second Edition. Johnston Division, Minnesota.

Environment Agency R&D Project P2-178. Review of Non-intrusive Groundwater Investigation Techniquesfor Groundwater Pollution Studies (in preparation).

Environment Agency R&D Project record P5-044. Guidance on Monitoring the Operational and Post-remediation Performance of Remedial Techniques (in preparation)

Environment Agency (1988) Review of LNAPL Monitoring Techniques in Groundwater. R&D ProjectRecord P2/080/1/M.

Guidance Document for Combined Geoenvironmental and Geotechnical Investigation. AGS 2000.

Idel, K.H., Muhs, H., and Von Soos, P. (1969) Proposals for quality classes in soil sampling and the importanceof boring methods and sampling equipment. In: Soil Mechanics and Foundation Engineering, Mexico,Speciality Session No 1. Rotterdam: Balkema.

Ministere de l'Industrie (SQUALPI). Applied Geophysics Code of Practice. With BRGM, CGG,CGGF andLCPC, France.

Nielson, D.M. (1991) Editor. Practical Handbook of Groundwater Monitoring. Lewis Publishers, Michigan,USA (Chapters 6 and 7).


Reynolds, J.M. An Introduction to Applied and Environmental Geophysics.

Site Investigation Steering Group (1993) Guidance for the Safe Investigation by Drilling of Landfills andContaminated Land. Thomas Telford, London.

Telford, Geldart, Sheriff and Keys. Applied Geophysics.

USEP (1991) Handbook of Suggested Practices for the Design and Installation of Ground-WaterMonitoring Wells EPA1600 14-89 1034 (available on the Internet: http://www.epa.gov/swerust1/at/wwelldct.pdf last accessed August 2000).

http://www.epa.gov/swerust1/ at/wwelldct.pdf

http://www.epa.gov/swerust1/ at/wwelldct.pdf


5. SAMPLING

5.1 - Checklist of major issues to be considered in preparation for and when sampling

5.2 - Labelling samples – information needed

5.3 - Type and amount of samples (Table A5 from Environment Agency R&D TechnicalReport Number P5-066/TR Secondary Model Procedures for the Development ofAppropriate Soil Sampling Strategies)

5.4 - Field techniques used in soil sampling (Table A7 from Environment Agency R&DTechnical Report Number P5-066/TR Secondary Model Procedure for the Developmentof Appropriate Soil Sampling Strategies)

5.5 - Sample chain of custody record



5.1 - Checklist of major issues to be considered in preparation for and when sampling

This checklist uses the simple example of a site on which two pollutant linkages have been identified, namelyleakage from an underground petrol tank and known disposal of lead catalyst waste.

Issues Tick Comments (using example)

Has a Conceptual Model been developed for thesite and have the pollutant linkages beenidentified?

e.g. unleaded petrol leakage from an undergroundtank migrating into a major aquifer.

possible leaching into the ground water fromdisposal of lead catalyst waste.

Can the site be zoned into areas of pollutantlinkages and others so that the sampling can betargeted, as well as providing general coverage ofthe remainder of the site if required? Where andhow many sampling locations should be plannedfor in these areas?

e.g. three zones:

1) vicinity of the tank (three locations in thisinstance);

2) area of known lead catalyst disposal (eightlocations in this instance);

3) remainder of site where pollutant linkageshave not been determined (five locations inthis instance).

Has the purpose of the site investigation beendetermined? Should it be carried out on a stagedbasis or as a single exercise?

• to establish baseline conditions?

• to investigate pollutant linkages?

• to investigate redevelopment pollutantlinkages?

• preliminary/exploratory/main/validation?

Exploratory, in this instance, to investigateredevelopment pollutant linkages.

Are the likely contaminants of concern known i.e.what should be looked for and what otherparameters should be measured?

e.g. petroleum hydrocarbons, MTBE, benzene andlead.

What phase are the contaminants likely to be in?

• LNAPL (floating on water table)?

• DNAPL (sunk to base of water table)?

• dissolved phase (moving with groundwaterdirection)?

• adsorbed onto soil particles?

• adsorbed into building fabric?

• solid phase (non-adsorbed onto soilparticles)?

• gaseous/ vapour phase (in soil)?

• uptake into flora/fauna?

e.g.

• LNAPL (TPH, benzene) floating on watertable;

• dissolved phase (TPH, MTBE, benzene andpossibly lead);

• vapour phase, (benzene and other lightfractions of petrol);

• gaseous phase (methane and carbon dioxidefrom degradation of the petrol);

• solid non-adsorbed phase (lead).

Therefore, in this example, perched water,groundwater, any free phase present, gas and soilshould all be sampled.

Where are the contaminants likely to be found?

• location?

• depth, stratum, medium?

In the vicinity of the tank with the migrationplume following groundwater flow and possibly assoil gas.

Lead is likely to remain in the location in which itwas initially disposed; although site works such aslevelling, or service route excavation may havespread the lead catalyst around the site. Underacidic conditions, migration via leaching intogroundwater may have occurred.

What field techniques should be used to collectsamples or conduct tests?

e.g. LNAPL versus DNAPL? – an interface probemeter is a good way to determine if LNAPL orDNAPL is present.


Issues Tick Comments (using example)

What frequency of sampling or testing should becarried out?

e.g. interface probe used at pre-determined timesduring the day to reflect tidal cycle or otherinfluence on groundwater.

How much sample should be collected and whatlaboratory techniques should be used to test thesamples?

e.g. proportionally larger quantity per sample in‘general’ areas of the site to facilitate wide suite ofanalyses, compared to that per sample of leadcatalyst waste (specific quantities determined bylaboratory and methods).


5.2 - Labelling samples –information needed

• The name of the laboratory;

• any laboratory reference (often pre-printed onto labels provided by the laboratory);

• any information needed to ensure safe transportation/handling of samples;

• sample type (e.g. soil/water/sediment – sometimes pre-printed onto the label);

• site name/location;

• name of company taking the sample and possibly also the name of the person takingthe sample;

• company job number, other internal reference(s);

• date, and possibly also the time of, sampling;

• full sample reference;

• sample depth.

Note:

A sample may be made up of several different bottles/pots etc and the same information needsto be included on each.

Labelling must comply with legislative requirements e.g. the:

• Classification, Packaging and Labelling of Dangerous Substances Regulations 1986(and any amendments);

• Chemicals (Hazard Information and Packaging) Regulations 1993 (and anyamendments).


5.3 - Type and amount of samples(Table A5 from Environment Agency R&D Technical Report Number P5-066/TR Secondary ModelProcedure for the Development of Appropriate Soil Sampling Strategies)

Type of sample Typical application Amount of sample

Small disturbed sample Routine off-site chemical testing(including total and leachablesubstances, moisture content, organicmatter content)

1-2 kg depending on nature ofsoil (e.g. larger sample neededwhere high proportion of stone,pebbles or brick/concrete debris)

Small disturbed sample Extraction of soil pore water 1-2 kg depending on nature andpermeability of soil

Small disturbed sample For head-space testing ofvolatile/semi-volatile substances inthe field (indicative only)

Approximately 1 kg

Small disturbed sample Chemical testing in the field Substance and kit specific

U100 undisturbedsample

Laboratory analysis of volatile/semi-volatile substances

Standard core, 100mm diameter

Non-Aqueous PhaseLiquids

Chemical composition Application specific – check withreceiving laboratory

Large undisturbedsample

Measurement of density particle sizeand porosity

Depends on nature of strata – seeBS 812

Large disturbed sample Particle size analysis Depends on nature of strata – seeBS 812

Pressurised stainlesssteel or aluminiumcylinder

Laboratory analysis of ground gases(e.g. methane, carbon dioxide,oxygen)

Approximately 100 mls(pressurised to 10 atmospheres)

Activated carbon tubesample

Laboratory analysis of organicvapours

Exposure period/gas volume isapplication and substance specific

Colorimetric detectiontube

Field determination of a range ofdifferent gases and vapours

Exposure period/gas volume isapplication and substance specific


5.4 - Field techniques used in soil sampling(Table A7 from Environment Agency R&D Technical Report Number P5-066/TR Secondary ModelProcedure for the Development of Appropriate Soil Sampling Strategies)

Type of sample/test Technique

Small disturbed soil sample Soil auger (for shallow depths), trial pits, trenches, boreholes,probeholes (although note that sample recovery from probeholes may bepoor in unconsolidated strata)

Large disturbed soil sample Trial pits, trenches, boreholes

Large undisturbed/U100undisturbed samples

Cable percussion borehole drilling

Non-aqueous phase liquids Sampling by disposable bailer (e.g. down dedicated monitoring wells) orsimilar container from trial pits/trenches

Chemical soil test kits Substance and application specific

In situ gas and vapourtesting:

• Ground gases

• Organic vapours

• Other gases/vapours

Portable instruments used, for example, during probehole/boreholeformation and in dedicated monitoring wells

• Combined infra-red/electrochemical cell gas analysers• Flammable gas meters (incorporating catalytic oxidation/thermal

conductivity/electrochemical cell)• Gas pressure/flow meters

• Photo-ionisation Detectors (PIDs) fitted with an appropriate lamp• Organic vapour analysers (flame ionisation method)• Activated carbon tube

• Colorimetric detection tube


5.5 - Sample chain of custody record



American Society for Testing and Materials (1995) Standards on Ground Water and Vadose ZoneInvestigations: Drilling, Sampling, Well Installation and Abandonment Procedures.

American Society for Testing and Materials (1999) Standards on Ground Water and Vadose ZoneInvestigations: Drilling, Sampling, Geophysical Logging, Well Installation and Decommissioning. 2nd

Edition

American Society of Safety Engineers. Soil Sampling (Technical Engineering and Design Guides as Adaptedfrom the U.S. Army Corps of Engineers, No. 30).

Barcelona, M.J., Helfrich, J.A. and Garske, E.E. (1988) Verification of sampling methods and selection ofmaterials for groundwater contamination studies. In: Collins, A.G. and Johnson, A.I. (eds.) GroundwaterContamination: Field Methods ASTM STP963 (Philadelphia).

British Standard BS 1377-1 (1990) Methods of test for soils for civil engineering purposes Generalrequirements and sample preparation.

British Standard BS 1427 (1993) Guide to field and on-site test methods for the analysis of waters.

British Standard BS 1924-1 (1990) Stabilised materials for civil engineering purposes. Generalrequirements, sampling, sample preparation and tests on materials before stabilisation.

British Standard BS 3680-10E (1993) (ISO 9195:1992) Measurement of liquid flow in open channels.Sediment transport. Sampling and analysis of gravel bed material.

British Standard BS 5930 (1999) Code of practice for site investigations, Section 3:21 frequency of samplingand testing in boreholes, Section 3:22 Sampling the Ground.

British Standard BS 7755-1.2 (1999) (ISO 11074-2:1998) Soil quality. Terminology and classification.Terms and definitions relating to sampling.

British Standard BS 7755-3.11 (1995) (ISO 11048:1995) Soil quality. Chemical methods. Determination ofwater-soluble and acid-soluble sulphate.

British Standard BS EN ISO 10301 (1997) (BS 6068-2.58:1997) Water quality. Determination of highlyvolatile halogenated hydrocarbons. Gas-chromatographic methods.

British Standard BS1017 (1989) Sampling of Coal and Coke. Part 1 Methods for sampling coal. BritishStandards Institution (London).

British Standard BS6068 (1981) Section 6.1 Guidance on the Design of Sampling Programmes. BritishStandards Institution (London).

British Standard BS6068- 6.14 (1998) (ISO 5667 – 14:1998) Water quality. Sampling. Guidance on qualityassurance of environmental water sampling and handling.

British Standard EN 25667-1 (1994) (BS 6068-6.1:1981 ISO5667/1-1980) Water quality. Sampling.Guidance on the design of sampling programmes.

British Standard ISO/5667- 18: Guidance on sampling groundwaters from potentially contaminated sites(ISO/DIS 5667-18).

Bymes, M.E. (1994) Field Sampling Methods for Remedial Investigations CRC Press - Lewis Publishers.

Carter, M.R. Soil Sampling and Methods of Analysis. CRC Press - Lewis Publishers.

Cheremisinoff, P.N., Gigliello, K.A., O’Neill, T.K. Groundwater-Leachate: Modelling, Monitoring,Sampling. ASIN: 0877623767.

Department of the Environment (1994) CLR 4. Sampling strategies for contaminated land. Report by The


Centre for Research into the Built Environment. The Nottingham Trent University.


Department of the Environment, Transport and the Regions CLR 11 Handbook of Model Procedures for theManagement of Contaminated Land. Contaminated Land Research Report (2000 in preparation).

Environment Agency (1998) National Sampling Procedures Manual.

Environment Agency R&D Technical Report Number P5-066/TR Secondary Model Procedure for theDevelopment of Appropriate Soil Sampling Strategies)

Environment Agency. Guidance on Monitoring of Landfill Leachate, Groundwater and Surface Water (inpreparation).

Environment Agency. Guidance on Monitoring the Operational and Post-remediation Performance ofRemedial Techniques. R&D Project P5-044.

Hvorslev, M.J. (1948) Subsurface exploration and sampling of soils for civil engineering purposes.Vicksburg, Miss: Waterways Experiment Station.

Idel, K.H., Muhs H., and Von Soos, P. (1969) Proposals for quality classes in soil sampling and the importanceof boring methods and sampling equipment. In: Soil Mechanics and Foundation Engineering, Mexico,Speciality Session No 1. Rotterdam: Balkema.

International Standards Organisation ISO/DIS 10381-1. Soil quality: Sampling – Guidance on the design ofsampling programmes.

International Standards Organisation ISO/DIS 10381-2. Soil quality: Sampling – Guidance on samplingtechniques.

International Standards Organisation ISO/DIS 10381-4. Soil quality: Sampling – Guidance on the procedurefor the investigation of natural, near-natural and cultivated sites.

International Standards Organisation ISO/DIS 10381-5. Soil quality: Sampling – Guidance on proceduresfor the investigation of soil contamination of urban and industrial sites.

International Standards Organisation ISO/DIS 10381-6 (1993) Soil quality: Sampling – Guidance on thecollection, handling and storage of soil for the assessment of aerobic microbial processes in the laboratory.

International Standards Organisation ISO/DIS 10381-7 (1993) Soil quality: Sampling – Guidance on theinvestigation and sampling of soil gas.

International Standards Organisation ISO/DIS 10381-8 (1993) Soil quality: Sampling – Guidance on thesampling of stockpiles.

Saxena, K.S., Gill, S.A., Lukas, R.G. Subsurface Exploration and Soil Sampling. American Society of SafetyEngineers.

Tan, K.M. Soil Sampling, Preparation, and Analysis. Marcel Dekker.

Wilson, N. Soil Water and Ground Water Sampling. CRC Press - Lewis Publishers.


6. ON-SITE MEASUREMENTS

6.1 - Portable instruments commonly used for site investigations

6.2 - Groundwater field sampling installations commonly used for site investigations

6.3 - Groundwater sample extraction methods commonly used for site investigations

6.4 - Soil gas sampling equipment commonly used for site investigations



6.1 - Portable instruments commonly used for site investigations

Instrument Analytes/capabilities ApplicationsDetection/

quantificationlimits

Interference Maintenance/care

Interface meter Air/water, air/product andwater/product interfaces; isintrinsically safe.

Groundwater monitoring. Resolution: 1mm Dirt or viscous producton the probe and rainor condensation waterinterfere.

Keep the probeclean, handle withcare.

Landfill gasanalyser

Typical analytes: CH4, CO2 by infra-red absorption, O2, H2S and CO byinternal electro-chemical cells;records maximum and stabilised CH4

concentrations, atmospheric pressure,gas pressure/vacuum, temperature;display of methane concentration as% by volume and % LEL (lowerexplosion limit); some models areintrinsically safe.

Routine monitoring of landfill sitesand other sites where bulk gases fromthe microbial degradation of organicmaterials are expected; may be usedin confined areas, if intrinsically safe.

Methane has highthreshold of accuracy(+/-10% LEL);typical detectionlimits: 0.5% CH4,0.5% CO2; 1% O2

Avoid water enteringthe instrument.

Check calibration,batteries, filters.

Flameionisationdetector(F.I.D.)

Detection of organic compounds inthe gas phase; fast response time (2-3seconds) and good long-termstability; intrinsically safe modelshave been developed, but mostmodels are not intrinsically safe,since an open flame is used fordetection.

Use models which are notintrinsically safe only in well ventedareas or where gas concentrations arebelow 20% of the LEL (i.e. 1% byvolume), e.g. detection of leaks inpiping and apparatus containinghydrocarbon gases, measurement ofatmospheric hydrocarbonconcentrations at low levels,‘continuous’ on-site monitoring.Intrinsically safe models can be usedfor compliance monitoring withhealth and safety laws; landfillmonitoring; tracking migratoryemissions; monitoring safety of

Typically detectionlimits: 0.5 ppm,1ppm; typicalaccuracies: +/-1-5%(for semi-logarithmicscales) or +/-0.1ppm.

Two versions: one withGC and one withoutGC, standard version(without GC) does notdifferentiate betweenmethane and VOC’swhile the GC versiondoes; will not operatein very oxygendeficient areas.

Check calibration,batteries, filters;highconcentrations ofhydrocarbons cancontaminate(‘poison’) thedetector for aconsiderable time.





buildings, etc.

Personal gasmonitors

Sensor/alarm for explosive and othergases and in normal operatingconditions should be intrinsicallysafe. Instantaneous measurement ofthe gas content in the atmosphere;measurement of short-term exposurelevel and intake by inhalation afterone or more work shifts. Up to fourgases can be measured at any onetime.

Personal protection in hazardousareas.

Typical ranges: 0.1-100% LEL; 0-1000ppm CO; 0%-35% O2; 0-500ppmH2S; 0-3% CO2; 0-100ppm chlorine

Silicones, halogens(>1000ppm),halogenatedhydrocarbons, volatileorganometallics,phosphorous andsulphur containingcompounds maydamage the sensor.

Check batteries;do not replacedry-cell batteriesin a hazardous orpotentiallydangerous area.

Photoionisationdetector (PID)

Analysis of volatile organiccompounds (VOC’s) within soilsamples using photoionization and aUV lamp.

Generally used for ‘HeadspaceAnalysis’ of VOC’s within soilsamples.

Typical range: 0.1-2000 ppm, linearrange: 0.1ppm-400ppm, detectionlimit: 0.1ppmrepeatability: +/-1.0%.

Avoid water or dirtentering the instrument.

Check batteriesand calibration.

Portablehydrocarbonanalyzer

In situ hydrocarbon screening tool,based on the modulation oftransmitted light intensity along an-optical fibre; particularly sensitive tohydrocarbons in the range C6 to C10;no methane interference or highhumidity related problems; fastresponse; usually certified asintrinsically safe.

Used for determination of free phasehydrocarbons (BTEX/diesel) invapour, water/vapour interfaces andwater environments e.g.hydrocarbons emanating from storagetanks or in remediation wells, leakdetection and wastewater discharge,water quality and groundwatermonitoring.

Typical range: 0-20,000 ppm as BTEXin water; detectionlimit: 200ppb forBTEX, otherwiseppm range;accuracy+/-3ppm or10% whichever isgreater.

Avoid long-termexposure to product orwater, especially atdepth of more than0.5m of water; theprobe can be used forshort periods of time todepths up to 8m.

Keep the probeclean (followmanufacturer’sinstructions),preconditioning ofthe probe may berequired; checkcalibration andbatteries.

Geiger-Muellercounter

Measures radioactivity in air. Personal protection against ionisingradiation.

Typical range: 0.05-1.25MeV

Check batteries.





Electronicmeters andprobes

In situ measurement of pH, dissolvedoxygen, electric conductivity, redoxpotential, temperature.

Routine monitoring of ground andsurface waters, and In situmeasurement of samples which arelikely to change on exposure to air(e.g.. landfill leachates).

Probe specific; seemanufacturer’sdetails.

Not suitable in oilyenvironments;dissolved oxygen andelectrode potentialmeasurements onlysuitable in ground andsurface waters.

Calibration check;store probesaccording tomanufacturer’sinstructions.

Notes –

Confirmatory laboratory analysis:

All measurements made on site with portable instruments should be supported by confirmatory laboratory analysis.

Test kits and ion specific probes:

A range of chemical and biological field test kits, such as immuno-assays, and ion selective probes are commercially available. These provide for a rapid analysis in the fieldand are useful screening tools. However, their sensitivity and accuracy are relatively coarse and may be affected by site conditions. Thus, for quantitative assessment,measurements should to be accompanied laboratory analysis. Test kits should also be used only for testing a matrix for which they have been validated. Thus a test kitvalidated for testing of soils should not be used for groundwater until the kit has been validated for groundwater.


6.2 - Groundwater field sampling installations commonly used for site investigations

Samplinginstallations

Principle/description applications Comments/limitations

Piezometer Tube or pipe usually of an outer diameterbelow 80 mm with a porous element orperforated section.

Dependent onsampling extractionmethod.

Only one specificzone/depth rangecan be sampled.

Multipleborehole/piezometerarrays

A group of closely spaced boreholes orpiezometers installed at different depths.

Dependent onsampling extractionmethod.

Can causeexcessive grounddisturbance.

Nestedpiezometers

A group of isolated piezometers installedwithin a larger diameter borehole to enablesampling over a specific depth intervalwithin the aquifer. The probes are isolatedby an impermeable seal between them.

Dependent onsampling extractionmethod. Allows fordepth profiling.

Seals between theprobes are difficultto install and maybe unreliable.

Multi-levelsampler

System enabling sampling from discretedepths. The system may be driven directlyinto the ground, installed in an existingborehole or in a purpose-drilled hole.

Dependent onsampling extractionmethod. Allows fordepth profiling.

Difficult to installand requiresspecialistknowledge. Costly.


6.3 - Groundwater sample extraction methods commonly used for site investigations

Sampleextractionmethods

Principle/description Applications Limitations

Bailer (‘grabsampler’)

Samples groundwater at specific depths withina borehole or piezometer. Consists of a tube orcylinder with a check valve at the lower end orboth ends. The opening and closing of thevalve(s) can be controlled by motion,electricity, gas pressure, vacuum or bymechanical messenger. Made of PVC, stainlesssteel or Teflon.

Suitable for mostparameters. Closed orshut-in-bailer must beused for redox potential,dissolved gases, VOC’sand TOX.

If the number ofmonitoring points and/orsampling frequency arehigh, purging andsampling can belaborious.

Inertia pumps Consists of a continuous length of tube with anon-return valve at the lower end. Samples areretrieved by lowering the tube down themonitoring well to the required depth and thensuccessively lifting and lowering the tube overa short distance. Mechanical lifting devices arecommercially available. The tube shouldpreferably be made of Teflon. With theamendment of a second inner tube can besuitable for VOC’s etc.

Suitable for mostparameters except forredox potential,dissolved gases, VOC’s,TOC and TOX.

Sampling can belaborious. Limited todepth of approx. 60 m.

Care to be taken not toentrain air in the“sampling” column.

Bladder pumps Consists of a sample chamber with a gasinflatable bladder inside and a check valve ateach end. The bladder is successively inflatedand deflated using compressed gas, throughwhich the sample is lifted. Available in a rangeof sizes.

Can be used forsampling piezometerswith diameters as lowas 25 mm. Suitable formost parameters.

Air introduced to thepump during samplingmay affect performance.Limited to sampling fromshallower depths. Somehydrocarbons may affectthe pump’s rubber parts.

Gas driven pumps Similar to bladder pumps but do not contain aninflatable bladder. Sample is transported bysequential pressurisation and venting.

Suitable only formeasurement ofelectrical conductivity,major ions, trace metals,nitrate and non-volatileorganics.

Limited by the smallnumber of suitabledeterminands.

Gas lift pumps The sample is forced upwards in an air/samplemixture by applying compressed gas (air) to theexternal case of the borehole. The water istransported up an inserted tube.

Suitable only formeasurement ofelectrical conductivity,major ions, trace metalsand nitrate.

The resulting aerosol maybe hazardous. The samplemay be significantlyaltered through themixing with air and gasmay be forced into thegeological formation.

Suction/vacuumpumps

Available in a range of capacities and pumpingspeeds

Suitable only formeasurement ofelectrical conductivity,major ions, nitrate andnon-volatile organics.

Limited to a depth ofaround 10 m. Limited bythe small number ofsuitable determinands.


6.4 - Soil gas sampling equipment commonly used for site investigations

Samplinginstallations

Principle/description Applications/limitations

As in table 6.2

Drive-inpiezometers/gasspike

Steel pipes of small diameters (approx 80 mmo.d) with a perforated section or gas inlet atthe lower end, which are directly driven intothe ground using a hammer or engine-drivendevice.

Depth limited to about 3-5 meters.Suitable only for a limited range ofsoils, but easy to install and use. Alarge area can be surveyed in a shorttime. Can give false negatives wherethey are too shallow to penetrate thecritical zone or where used in lowpermeability surface soils.

Samplecontainers Principle/description Applications/limitations

Gas samplingbulbs/cylinders

Gas is passed through a sampling vessel fittedwith valves at both ends. Sampling is carriedout with both valves open and continues untilthe gas in the vessel is replaced by the samplegas. A pump must be used if there is nopositive pressure in the sampling tube. Thecylinders are made from glass, steel oraluminium alloy.

A sufficiently high flow rate is requiredto replace the gas in the cylinder or alow flow rate pump must be used. Thevolume of gas passed through thesampler must be monitored. The vesselshould be flushed with an inert gasprior to sampling

Pressurisedgas cylinders

The gas sample is compressed into a smallcylinder using a hand pump. Samplers areusually made of stainless steel or aluminiumalloy and may be fitted with either one valve(‘closed end’) or two valves (‘flow through’).Alternatively, the cylinder may be evacuatedprior to sampling and the vacuum is then usedto draw the sample into the cylinder.

The body material may be reactive tocertain VOC’s and hydrogen.

Adsorbent tubes The gas is passed through a small steel orglass tube filled with an adsorbent. Selectivegas components can be sampled by varyingthe adsorbent material. Gas components arepre-concentrated. Must be used incombination with a low flow pump.

Used for trace gas analysis.

Gas samplingbags

Inflatable light-weight bags which are pre-emptied before sampling. The sample may bereleased directly into the bag or injected witha syringe. Available in different materials,such as Tedlar®, Teflon®, aluminium or sarangas sampling bags.

Storage period of samples is limited.



British Standard ISO/5667- 18 (draft). Guidance on Sampling Groundwaters from PotentiallyContaminated Sites (ISO/DIS 5667-18).

Construction Industry Research and Information Association (1993) The Measurement of Methane and OtherGases from the Ground. Report 131.

Department of the Environment (1991) Landfill Gas: A Technical Memorandum Providing Guidance onthe Monitoring and Control of Landfill Gas. Waste Management Paper No. 27, HMSO, London.

Environment Agency (2000) Guidance on the Monitoring of Landfill Leachate, Groundwater and SurfaceWater. Consultation Document.


7. CROSS-CONTAMINATION

7.1 - Some ways in which cross-contamination can occur during a site investigation

7.2 - Examples of well and badly constructed trial pits

7.3 - Description of how to drill a borehole through an aquiclude into an aquifer

7.4 - Illustration of how to drill a borehole through an aquiclude into an aquifer



7.1 - Some ways in which cross-contamination can occur during a site investigation

Potential source/cause of cross-contamination

Possible mitigation measures

Penetration through an aquiclude intoan aquifer.

Creation of a preferential migrationroute from shallow contaminatedhorizons to deeper, uncontaminatedones (where there is no aquiclude)during drilling.

Badly constructed boreholes resultingin ineffective seals between formations.

• use appropriate drilling methods and techniques (see Chapter 4);

• specify an appropriate borehole design (see Chapter 7);

• supervise construction of groundwater/gas monitoringinstallations and double check all measurements made by thecontractor;

• use an experienced drilling contractor that understands the issuesfully.

Contaminated groundwater and arisingsbrought to the surface from trial pitsand boreholes.

Fugitive release of contaminatedgroundwater and/or dust from trial pitsand boreholes duringexcavation/drilling and subsequentpurging.

• minimise by choice of most appropriate investigation method;

• ensure that ‘clean’ and ‘contaminated’ materials are segregatedas far as is practicable;

• adopt appropriate water/spoil management methods;

• protect the ground with wooden boards/plastic sheeting etc wherenecessary.

Surface water entering a monitoringinstallation if the level of the cover islower than surrounding ground.

• choose location of boreholes carefully with regard for generaltopography;

• choose an appropriate design for borehole headwork.

Badly back-filled boreholes or trial pits(see Chapter 7).

• take care in back-filling.

Contaminated spoil re-used duringconstruction of a monitoringinstallation.

• be clear in specifying to the contractor that only clean material isto be used;


Supposedly clean imported back-fillmaterial is actually contaminated.

• inspect all imported material and reject if not acceptable;

• if accepted, analyse to confirm properties are acceptable.

Surplus arisings from boreholes andtrial pits badly managed.

• give appropriate consideration to waste management proceduresat outset of project and communicate this to all involve parties;

• check condition of skips brought to site;

• adopt Duty of Care.

Hydrocarbon oils used to lubricatescrew threaded drilling equipment e.g.casings, augers (oils can be transferredto formation).

• specify the use of synthetic lubricants, lard, vegetable-based oilsor pure vegetable oils;


Hydrocarbon oils introduceddeliberately into the air line to lubricatedown the hole hammer equipment

• avoid use of DTH if other methods are suitable (see Chapter 4);

• specify the use of synthetic lubricants or vegetable-based oils;



Potential source/cause of cross-contamination

Possible mitigation measures

Hydrocarbon oils inadvertentlyintroduced to the formation duringdrilling via air flow from badlymaintained compressors (applicable torotary coring, rotary drilling and downthe hole hammer techniques).

• notify the contractor that properly serviced compressors only canbe used on site;

• on particularly sensitive projects, request that proof ofcompressor servicing is provided;

• ensure that badly maintained/faulty equipment is removed fromsite.

Oil/diesel leaking onto ground surfacefrom badly maintained plant andvehicles brought to site.

• be aware of condition of plant/vehicles when brought to site andduring investigation;

• immediately contain any losses.

Leakage/spillage from contractor’stemporary diesel tanks.

• specify that these are to be contained within temporary bunds andfilled/used carefully.

Contamination transferred betweeninvestigation locations and off-site onequipment, vehicle wheels etc.

• clean equipment between locations;

• use an experienced drilling contractor that understands the issuesfully;

• clean vehicle wheels if necessary before they leave site. onlarger investigations, hire a wheel wash.

Smearing between formations duringexcavation (excavator bucket) ordrilling (from casings/bit).

• not possible to eliminate but impact in many instances is unlikelyto be significant.

Smearing between formations ascasings are “surged” into position (atechnique commonly carried out bycable percussive drillers to aid theirsubsequent removal).

• specify that this is not acceptable.


Groundwater pumps and dippingequipment used between investigationlocations without cleaning.

• make sure that these are cleaned between locations.

Vandalism to plant, vehicles, skipsboreholes etc on site.

• adopt appropriate security arrangements during the siteinvestigation;

• ensure that all boreholes have securely locked covers wheninvestigation is finished.

Contaminants transferred betweensamples and monitoring equipment etcon dirty gloves.

Sampling equipment e.g. trowels etc.not cleaned between samples

• wear two pairs of disposable gloves and change the outer pair asfrequently as necessary;

• clean sampling equipment or use dedicated sampling equipment.

Use of dirty/damaged/unsuitablesample vessels.

• check that all vessels are clean and caps are well-fitting;

• segregate new clean pots from used ones;

• wipe sample vessels after filling to remove soil/water residues.

Bad handling of samples after they haveleft site.

• not easy to manage but use a reputable laboratory and followprotocols set out in Chapter 5.


7.2 - Examples of well and badly constructed trial pits


7.3 - Description of how to drill a borehole through an aquiclude into an aquifer

(illustrated in 7.4)

NBdescribed in conceptual terms only – the precise design (diameters, depths etc) will need to be tailored to thesite specific conditions

Stage One: Insert a wide diameter “cut-off” casing into the aquiclude to an appropriate depth;

Stage Two: Place an appropriate thickness of bentonite plug to form a seal and pull back the wide diametercasing to the top of the seal;

Stage Three: Drill and drive in a narrow diameter casing through the bentonite seal to the required depth;

Stage Four: Place a bentonite plug at the base of the borehole (if needed);

Stage Five: Install a groundwater/gas monitoring standpipe (filter-wrapped if necessary to prevent finesingress) with a sand/gravel pack around the response zone and a bentonite plug placed above the sand/gravelpack. Withdraw the narrow casing to just above the aquiclude;

Stage Six: Place bentonite plug/suitable fill material whilst removing casing and install a robust, lockablecover.

Where drilling is to proceed through several aquifers and intervening aquicludes, then several sizes ofcasing and down-hole drilling equipment will be needed. This will need very careful consideration at anearly stage.


7.4 - Illustration of how to drill a borehole through an aquiclude into an aquifer

(described in 7.3)

AQUICLUDE

AQUIFER

BENTONITEPLUG

CASINGPULLED-BACK

BENTONITEPLUG

RESPONSEZONE

BENTONITEPLUG

PLUGBENTONITE

STANDPIPE

KEY

FILL/MADE GROUND

SAND AND GRAVEL

CLAY

SAND

BENTONITE SEAL

PERFORATED

UNPERFORATED

CONCRETE PLINTH



American Society for Testing and Materials Standard Practice for Decontamination of Field EquipmentUsed at Non-radioactive Waste Sites D5088-90. (West Conshohocken)

American Society for Testing and Materials Standard Practice for Decontamination of Field EquipmentUsed at Low Level Radioactive Waste Sites D5608-94. (West Conshohocken)


Environment Agency Decommissioning Redundant Boreholes and Wells (leaflet produced by the NationalGroundwater and Contaminated Land Centre)

USEP (1991) Handbook of Suggested Practices for the Design and Installation of Ground-WaterMonitoring Wells EPA1600 14-89 1034 (available on the Internet: http://www.epa.gov/swerust1/cat/wwelldct.pdf last accessed August 2000).

http://www.epa.gov/swerust1/cat/wwelldct.pdf

http://www.epa.gov/swerust1/cat/wwelldct.pdf


8. ANALYTICAL STRATEGIES

8.1 - What do we mean by Total Petroleum Hydrocarbons (TPH)?

8.2 - Key questions to be considered in developing an analytical strategy



8.1 - What do we mean by Total Petroleum Hydrocarbons (TPH)?

TPH is sometimes referred to, incorrectly, as hydrocarbon oil, extractable hydrocarbon oil and grease andmineral oil*. There are many analytical techniques available for which the output is reported as TPH. No singlemethod measures the entire range of petroleum-derived hydrocarbons.

The definition of TPH depends on the analytical method used because a TPH determination is the totalconcentration of the hydrocarbons extracted and measured by a particular method. The same sample analysedby different TPH methods may produce different TPH values. It is therefore essential to know how eachdetermination is made and to recognise that the interpretation of the results depends on the capabilities andlimitations of the selected method.

Analytically, there are two major components in TPH: Gasoline Range Organics (GRO) which are volatilehydrocarbons in the C5-C10 range which are speciated to include BTEX’s/MTBE and Diesel Range Organics(DRO) which are extractable hydrocarbons in the C10 – C35 range covering both aliphatic and aromatichydrocarbons. Crude oils may contain molecules with 100 carbons or more. These heavy hydrocarbons areoutside the detection range of the more common GC-based TPH methods, but specialised gas chromatographsare capable of analysing such heavy molecules.

Generally C5 to C10 hydrocarbons are detectable through purge and trap or headspace analysis for both soil andwaters. Generally C10 to C35 hydrocarbons are detectable through a solvent extraction process followed by gaschromatography flame ionisation detection (GC/FID). GC/FID is a commonly used method for petroleumhydrocarbon analysis. The method involves extracting the hydrocarbons with a suitable solvent, concentratingthe extract and injecting into a GC equipped with an FID. Quantification is performed by comparing the areaunder the chromatogram from the appropriate FID response of a sample to the corresponding response of astandard mixture.

GC-based methods are preferred for TPH measurement because they detect a broad range of hydrocarbons, theyprovide both sensitivity and selectivity, and they can be used for TPH identification as well as quantification.The speciation of the hydrocarbons into the composite aliphatics (mineral oils) and the composite aromatics(polynuclear aromatics) is essential to allow a comprehensive risk assessment to be carried out covering thecomponents that are most toxic to the receptor. One approach is that of the US-based TPH Criteria WorkingGroup (TPHCWG, 1997a-e) which has developed detailed procedures for analysing TPH within a riskassessment framework.

Infra-red spectrometry, although widely used in the oil industry, is generally less useful than gaschromatographic methods since the former provide no understanding of chemical composition (it yields only anumber: oil in mg/kg). At best, infra-red gives a relative measure of contamination (although more rarely isused to identify functional groups), so its role (if used) is likely to be in delineation. It should also be borne inmind that infra-red fails to identify certain hydrocarbons, depending on their molecular weights (a particularconcern being the losses of volatiles).

* mineral oil is often referred to but actually consists of, amongst other chemicals, straight chain aliphatic hydrocarbons in the range C10 toC35 (of which TPH is a fraction).

In preparing the text in this box, the contribution of Geochem Group, Chester is gratefully acknowledged.


8.2 - Key questions to be considered in developing an analytical strategy


In situ or ex-situanalysis, or acombination of both?

Using a PID, for example, can be a cost-effective means of screeningsoil and groundwater samples for laboratory analysis of VOC’s.

Turnaround timerequired?

A fast turnaround time may only be achieved by an on-site laboratoryor utilising field kit tests.

Detection limitsrequired?

Depending on the toxicity of the contaminant and the sensitivity of thereceptor, different detection limits may be suitable.

See also “Detection Limits” in Chapter 8.

Initial laboratoryscreening techniquesversus speciation?

A PAH screen, for example, could be used to select those samples forsubsequent USEPA 16 PAH’s speciation analyses.

Total metals orbioavailable metals orparticular valency?

Total metal could be used as a screen to determine any requirement tofurther analyse for bioavailable or a particular valency of metalconcentration For example, chromium (VI) is consideredcarcinogenic whereas chromium (III) and (0) are not classified ascarcinogenic.

Leachate analysis? Is leaching a pollutant linkage? Leachate analyses were developed todetermine the total amount of contaminant that would leach out intothe groundwater over a specified period of time (e.g. 60 years, (former)NRA analysis). They can, however, overestimate the amount likely tobe encountered in the field.

What is the analyticalmethod actuallymeasuring?

This is most relevant for organic analyses, where ranges of carbonchain length are analysed rather than a particular species.

For example:

(i) Colorimetric methods typically determine “overall” phenols,but this does not include p-cresol (which is often found oncontaminated land sites);

(ii) solvent extraction excludes analysis of volatiles;

(iii) DCM/acetone extraction (typically used for PAH extraction)will co-extract some plastics and resins, so caution must beexercised.

Soil characteristics? pH, organic matter content and clay content can affect the availabilityof contaminants and will therefore be important during any subsequentsemi-quantitative risk assessment determination of required RBCLs(Risk Based Clean-up Levels). The forthcoming CLEA guidelinevalues are dependent upon organic matter content and clay content.




Department of the Environment (1994) CLR 5. Information Systems for Land Contamination. Report byMeta Generics Ltd.

Department of the Environment, Transport and the Regions (in preparation) CLR 9 Contaminants in Soil:Collation of Toxicological Data and Intake Values for Humans. Total Petroleum Hydrocarbons.

Department of the Environment, Transport and Regions. Handbook of Model Procedures for theManagement of Contaminated Land (not yet published). Contaminated Land Research Report CLR 11.

Department of the Environment (1997) A Quality Approach for Contaminated Land Consultancy. CLR 12,prepared by the Association of Environmental Consultancies with the Laboratory of the Government Chemist.London.

Development and Validation of an Analytical Method to Determine the Amount of Asbestos in Soils andLoose Aggregates (1996)


Department of the Environment, Transport and the Regions. CLR 11. Handbook of Model Procedures for theManagement of Contaminated Land. Contaminated Land Research Report (in preparation).

Environment Agency Chemical Test Data on Contaminated Soils - Qualification Requirements ref.EAS/2703/1/6/Version3/FINAL 1

Eurochem (1998) Harmonised Guidelines for the Use of Recovery Information in Analytical Measurements(can be downloaded from the Internet free of charge: http//www.vtt.fi/ket/eurochem/publications.htm last visitedJuly 2000)

Eurochem (1998) Quality Assurance in Research and Development and Non-routine Analysis (can bedownloaded from the Internet free of charge: http//www.vtt.fi/ket/eurochem/publications.htm last visited July2000)

Eurochem (1998) The Fitness for Purpose of Analytical methods (can be downloaded from the Internet free ofcharge: http//www.vtt.fi/ket/eurochem/publications.htm last visited July 2000)

Eurochem and Royal Society of Chemistry (1999) Vam Bulletin Proficiency Testing and Contaminated Landpps 4-10 and p 35

National Rivers Authority (1994) Leaching Tests for Assessment of Contaminated Land: Interim NRAGuidance. R&D Note 301, National Rivers Authority (Bristol).

Smith, M.A. (1991) Data Analysis and Interpretation. In: Recycling Derelict Land. G. Fleming (ed.)Thomas Telford.

Van der Sloot et al (1997) Harmonisation of Leaching/Extraction Tests Elsever, Amsterdam.


9. TOPOGRAPHIC SURVEYS

9.1 - Example of topographic survey items/information needed

9.2 - Permanent ground marker types

9.3 - An illustration of the value of assimilating topographic survey data with historic maps

9.4 - Suggested points of measurement on a borehole for the level



9.1 - Example of topographic survey items/information needed

Project name/numberCo-ordinate system Arbitrary grid National grid Local grid

Level datum Ordnancedatum

Arbitrarydatum

Survey stations Permanent Temporary

Detail survey/scale of plot 1:200 1:500 Other

Detail to be included Permanent buildings/structures

Temporary/mobile buildings

Visible boundary features & descriptions

Roads, tracks, footways, paths

Changes in surfaces

Street furniture

Statutory authorities plant & service covers

Underground pipe sizes & inverts

Vegetation Isolated trees

Wooded areas

Vegetation limits

Pitches/recreation areas

Private gardens or grounds

Water features

Earth works

Industrial features

Railway features

Site access from public highways

Site investigation works

Spot levels Contours Roadsections

Height informationSpacing Interval SpacingOthers (specify)

Drawing information to beincluded

Site address

Site boundary

Site area in acres & hectares

Scale of drawing & scale bar (in metres)

Direction of true north

OS co-ordinates and/or grid

Historical information

Underground services Traced on site Digitised

Gas mains (high, medium, low pressure)

Water

Electrical (HV & LV)

Telephone (including fibre-optic)

Cable TV

Sewers (foul & storm)

Others

Dead services- approx. location & marked as ‘Dead’


9.2 - Permanent ground marker types

9.3 - An illustration of the value of assimilating topographic survey data with historicmaps



9.4 - Suggested points of measurement on a borehole for the level

“Stop cock” type cover set flush with the ground (cap covering well not shown)

cover

“Top hat” type cover s

cover

Measurement point could be:! the top of the well tube; or! ground level.

ground level

well tube

et proud above the ground (cap covering well not shown)

outer tube

ground level

Meas! ! !

well tube

127

urement point could be:the top of the well tube;the top of the outer tube; orground level.



BGS/EA 2000 Some Guidance on the Use of Digital Environmental Data BGS Technical Report WE/99/14,EA NGWCLC Report NC/06/32.

Ordnance Survey maps at various scales.

RICS Business Services Limited (RICS Books) (1996) Surveys of Land, Buildings and Utility Services atScales of 1:500 and Larger - Client Specification Guidelines 2nd Edition.

Surveys of Land, Buildings and Utility Services at Scales of 1:500 and Larger - Client SpecificationGuidelines 2nd Edition 1996. RICS Business Services Limited (RICS Books).


10. SITE OBSTRUCTIONS AND GEOTECHNICALCONSIDERATIONS

10.1 - Diagrammatic Presentation of Section 6 of the Party Wall etc. Act 1996 “AdjacentExcavation and Construction”


10.1 - Diagrammatic presentation of Section 6 of the Party Wall etc. Act 1996 “AdjacentExcavation and Construction”




Association of Geotechnical and Geoenvironmental Specialists. Guidelines for Combined Geoenvironmentaland Geotechnical Investigation (2000).

British Standard (1995) Code of Practice for Site Investigations. British Standard Institution (London).BS5930 (1981).

British Standard (1999) Code of Practice for Site Investigations. BS 5930.

Construction Industry Research and Information Association Special Publication 32 (1984) Construction OverAbandoned Mine.

Department of the Environment (1990) Regional Atlas of Mining Areas produced by Arup Geotechnics

Department of the Environment (1990) Review of Mining Instability in Great Britain produced by ArupGeotechnics


11. HEALTH AND SAFETY

11.1 - COSHH checklist

11.2 - CDM checklist

11.3 - Requirement flow chart for application of CDM Regulations

11.4 - Requirement flow chart for notification to HSE

11.5 - BDA site colour coded site characterisation system

11.6 - Investigations and surveys safety checklist

11.7 - Site visit safety checklist

11.8 - Safety method statement checklist



11.1 - COSHH checklist


Are hazardous substances likely to be:

• Present in the ground?

• Brought onto the site?

• Given off/produced by any work activity?

Have the hazardous substances been identified?

Have the hazards that these substances can present been assessed?

Is exposure to hazardous substances likely to occur via:

• Inhalation?

• Ingestion?

• Skin contact?

Who will be exposed:

• Site workers?

• Contractors?

• Visitors?

• General public?

• Others?

Have the risks associated with the following activities beenassessed:

• Site reconnaissance?

• Site investigations?

• Long term monitoring?

• Other?

Has COSHH been considered in planning and designing theinvestigation?



Are the safety procedures and precautions proposed adequate forcontrolling exposure of employees to substances hazardous tohealth?

Have arrangements been made for the maintenance of safetyequipment?

Have employees been given adequate training?

Is health surveillance needed?

What first aid training is needed?

Is monitoring required?

If YES what of and when?

When will the COSHH assessment be reviewed?

Do CDM/MHSW/PPER Regulations apply?

Source: CIRIA Report 132


11.2 - CDM checklist

Tasks Tick Comments

Appointment of a planning supervisor

Hand over of the site Health and Safety File, if one exists

Notification of the investigation to the HSE, if required

Preparation of risk and COSHH assessments for the investigation

Preparation of the pre-tender Health and Safety Plan

Commence preparation, or add to the existing Health and SafetyFile

Assessment of tenderers competence to carry out the investigation

Appointment of a principal contractor for the investigation

Preparation of the contractors risk and COSHH assessments

Preparation of the Construction Health and Safety Plan

Preparation of work method statements, to include health andsafety issues

Continued collection of information for the Health and Safety File

On completion of investigation carry out project review andfeedback

Complete Health and Safety File and hand over to client


11.3 - Requirement flow chart for application of CDM Regulations

Do the CDM Regulations applyto the investigation?

Is the local authority theenforcing authority for health

and safety purposes?

No

Is the investigation to be carriedout for a private householder?

No

Will demolition or dismantlingwork be involved as part of the

investigation?

No

Is the investigation notifiable?See Figure11.4

No

Will the largest number ofpeople on the site for the

investigation at any one timeexceed four?

No

Yes

YesNone of the CDM Regulations

apply

Yes No

Has the client entered into anarrangement with a developer?

Only CDM Regulation 7 (SiteNotification Requirement) and

13 (Designer Duties) apply

Yes All CDM Regulations apply

CDM Regulations do notapply except for Regulation

13 (Designer Duties)

R&D Tec

11.4 - R uirement flow-chart for notification to HSE
eq
hnical Report P5-065/TR 137

Written notification to HSE using Form F10 is required

Yes

Yes

No

Notification not required

Will the investigation be longer than 30 working days on site

Does the project need to be notified to the HSE

Will the investigation involve more than 500 person working days on site

No


11.5 – British Drilling Association site colour coded site characterisation system

BDA site designation Broad description

GREEN Subsoil, topsoil, hardcore, bricks, stone, concrete, clay, excavated road materials,glass, ceramics, abrasives, etc.

Wood, paper, cardboard, plastics, metals, wool, cork, ash, clinker, cement, etc.

NOTE: There is a possibility that bonded asbestos could be contained in otherwiseinert areas.

YELLOW Waste food, vegetable matter, floor sweepings, household waste, animal carcasses,sewage sludge, trees, bushes, garden waste, leather etc.

Rubber and latex, tyres, epoxy resin, electrical fittings, soaps, cosmetics, non toxicmetal and organic compounds, tar, pitch, bitumen, solidified wastes, dye stuffs, fuelash, silica dust etc.

RED All substances that could subject persons and animals to risk of death, injury orimpairment of health.

Wide range of chemicals, toxic metal and organic compounds etc., pharmaceutical andveterinary wastes, phenols, medical products, solvents, beryllium, micro-organisms,asbestos, thiocyanates, cyanides etc.

Hydrocarbons, peroxides, chlorates, flammable and explosive materials. Materials thatare particularly corrosive or carcinogenic etc.

Source: BDA Guidance Notes for the Safe Drilling of Landfills and Contaminated Land

This guidance should be used with caution and should not replace the assessments requiredby COSHH and CDM.


11.6 - Investigations and surveys safety checklist


Have assessments for all hazardous substances (COSHH) andother health and safety risks (MHSW) likely to be encountered onsite been carried out?

Has the use of a non-intrusive investigation method or one thatlimits ground disturbance to minimise contact between employeesand contaminants been considered?

What equipment will be required to help ensure health and safetyon site?

What safety procedures have been adopted?

In the case of an emergency, are the locations of and contacts forthe emergency services known and communicated to the site team?

Have any risks associated with possible lone working beenconsidered?

Have the emergency services been informed/consulted?

Source CIRIA Report 132


11.7 - Site visit safety checklist

Name of person(s) carrying out site visit: Contact number during site visit:

Vehicle make, colour and registration: Name and contact number of site representative:

Date and time of visit: Contact in office:

Site name, address and telephone number: Site size and note whether operational/disused/derelict:

Site accessed from (name of road) Site owner and contact details:

Grid ref.: Tick to confirm that location map attached

Job reference: Visit number:

Subject Information required


11.8 - Safety method statement checklist


Have the work objectives been defined?

Have appropriate risk assessments been undertaken?

Have the site activities been described and divided intocontaminated and ‘clean’ categories?

Have the timing and location of the site activities been described?

Have the entry and exit arrangements both for the site and betweencontaminated/’clean’ zones been described?

Are any phasing or relocation of zone boundaries and entry/exitarrangements required?

Have the safe working methods for each activity been detailed?

Have permits to work been obtained?

Have the use, storage and maintenance of PPE been detailed foreach activity?

Have the decontamination facilities for both people and plant beendescribed?

Have the communication procedures been detailed?

Are safety audits required? If YES are they described?

Have the environmental monitoring requirements been detailed?

Have the key staff their roles, qualifications and experience beendetailed in respect to health and safety?

Have the requirements for training been addressed?

Is medical screening of staff required?

Have the first aid requirements been defined?

Have the site emergency plan and emergency requirements beenestablished?

Has a record keeping system been established that details theresults of monitoring, changes in methods etc.?

Source CIRIA Report 132



British Drilling Association (Operations) Ltd, Essex. Guidance for the safe investigation by drilling oflandfills and contaminated land.

Building Research Establishment. Fire and explosion hazards associated with the redevelopment ofcontaminated land. BRE Information Paper IP 2/87. BRE (London), 1087.

Construction Industry Research and Information Association (1992) Special Publication 79. Methane andassociated hazards to construction: A bibliography.

Construction Industry Research and Information Association (1996) A guide for safe working practices oncontaminated sites. Report Number 132. Prepared by WS Atkins.

Construction Industry Research and Information Association Report 166 CDM Regulations – Work SectorGuidance for Designers.

Construction Industry Research and Information Association Report 172 CDM Regulations – PracticalGuidance for Clients and Client’s Agents.

Construction Industry Research and Information Association Report 173 CDM Regulations – Practicalguidance for Planning Supervisors.

Construction Industry Research and Information Association Special Publication 90 (1992) Handbook. SiteSafety.

Control of Substances Hazardous to Health (COSHH) Regulations 1999.

Construction (Design and Management) Regulations 1994.

Environment Agency. Health and Safety Codes of Practice Manual.

Environment Agency. Health and Safety Risk Management Manual.

Environment Agency. Health and Safety Management Procedures Manual.

Environment Agency. Occupational Health Manual.

Health and Safety Executive (1991) Avoiding Danger from Underground Services.

Health and Safety Executive (1980) Avoidance of danger from overhead electrical power lines. GS6.

Health and Safety Executive (1999) Health and Safety in Excavations – Be Safe and Shore. HS (G) 185.

Health and Safety Executive. A Guide to Managing Health and Safety in Construction. HSE Books

Health and Safety Executive. Five steps to Risk Assessment. HSE (IND(G)163L).

Health and Safety Executive. Managing Construction for Health and Safety, Approved Code of Practice.HSE Books.

Health and Safety Executive. Occupational exposure limits. EH40/2000, HSE Books (updated annually).


Health and Safety Executive. Protection of workers and the general public during development ofcontaminated land. HSE(G)66, 1991.

Institute of Petroleum (1998) Guidelines for investigation and remediation of petroleum retail sites.(London).

ISO FDIS 10381-3 Soil Quality Part 3 Guidance on safety.

Management of Health and Safety at Work Regulations 1999.

Personal Protective Equipment at Work Regulations 1993.

Site Investigation Steering Group (1993). Guidance for the safe investigation by drilling of landfills andcontaminated land. Thomas Telford, London.


12. ENVIRONMENTAL PROTECTION

12.1 - Fauna species that are protected together with their resting place

12.2 - Ecological evaluation checklist

12.3 - Possible mitigation measures



12.1 - Fauna species that are protected together with their resting place.

Species Legislation Habitat notes Protective Measure Close season(approximate dates)

Badger 1992 BadgersAct

Requires suitablesoils forburrowing

Protects badgers and theirsetts

Breeding females in settsfrom December to Mayinclusive

Bats – allspecies

1981 W&CAct,Schedule 5

Buildings, caves,hollow trees

Protects all bats, theirbreeding roosts, autumnroosts and hibernationroosts

Mid-May (approx.) to July(breeding), Mid October-early April approx.(hibernation).

All breedingwild birds

1981 W&CAct,

All habitats butespecially densescrub

Protects breeding birdsand their nests.

Mid March to late July(approx.)

Great crestednewt

1981 W&CActSchedule 5

Ponds with roughvegetation around

Protects newts and theirbreeding ponds

Late February to June

Otter* 1981 W&CAct,Schedule 5

Holts may beestablished awayfrom river courses

Protects otters and theirholts

Breeding can take placethroughout the year

Water vole 1981 W&CAct,Schedule 5

Burrows in ditchand river banks

Protects the burrowsystems

Occupied throughout theyear

Dormouse* 1981 W&CAct,Schedule 5

Diverse,especially ancientcoppicewoodland.

Protects dormice, theirnests and hibernation sites

May to July (nests),November to Marchinclusive (hibernation)

Sand lizard* 1981 W&CAct,Schedule 5

Sandy heathhabitats insouthern England

Protects the animal and itsbreeding site

May to July (breeding),November to Marchinclusive (hibernation)

Natterjacktoad*

1981 W&CAct,Schedule 5

Shallow pools,especially in heathand coastal areas

Protects the animal and itsbreeding site

Late February to early June

* rarer species that could be found at some sites in certain parts of the country


12.2 - Ecological evaluation checklist

Issues Tick CommentsWill the works affect an SSSI or other site withlegal protection (e.g. National Nature Reserves,Local Nature Reserves)?

Obtain information on SSSI from the StatutoryAuthority, English Nature (or CCW, SNH) or LocalPlans. Where SSSI may be affected the proposedinvestigation works must be agreed with the statutoryauthority. Seasonal limits on work may be advised

Will the works affect a scheduled site of localwildlife importance?

Obtain information on sites from the local WildlifeTrust (WT), or from Local Plans. The WT or theLocal Authority Ecologist can advise on theecological interest of the site and precautions to betaken, e.g. in the case of protected species beingpresent or species being the subject of BiodiversityAction Plans.

Does the site contain habitats suitable forbreeding birds and will proposed works resultin disturbance?

Inspect site for presence of trees, scrub, otherpotential nesting areas, e.g. derelict buildings. Wherenesting is likely employ seasonal working (betweenlate July and mid-March) to avoid disturbance

Are badgers present on the site and will worksaffect any setts?

Inspect sites for signs of burrowing or well usedanimal pathways. Advice on local badger activitymay be obtained from the local WT, or EN (CCW orSNH). Avoid works close to setts in the breedingseason

Are bats likely to be present on site and willworks affect their resting places?

Inspect site for potential habitat, buildings, trees withhollows or small crevices, underground caves orcrevices. Obtain specialist advice (from the WT, ENetc) where works may impinge on any such sites.Note that seasonal restrictions on work will apply.

Are other protected species likely to be present? Ponds are likely to contain amphibia. Obtain specialistadvice (from the WT, EN etc) where works mayimpinge on any such sites. Note that seasonalrestrictions on work may apply.

Will the works require the removal of any treesor hedgerows?

Check with the local authority for the presence of anyTPO, or hedges protected under the HedgerowRegulations on the site. Avoid the bird-breedingseason. Where trees are to be felled consult the localForestry Commission Conservators Office over theneed for a felling licence. Trees with hollows orcrevices may contain bats (see above).


12.3 - Possible mitigation measures

Investigation workelement

Potential environmentalimpact

Possible mitigation measure

Creation of accessroutes for tracked orwheeled vehicles

Impacts on burrowing animalsincluding badgers, loss of treesand scrub with potential impactson breeding birds

Seasonal working to avoid bird breeding season,planned access routes to avoid habitats, plannedaccess routes following ornithological survey tolocate nesting areas if works in bird breedingseason.

Borehole installation Impacts on burrowing animalsincluding badgers, risk of animalsfalling into uncapped boreholes.

Adjust spatial pattern of samples. Avoid anyground disturbance within 30 metres of anoccupied badger sett. Ensure any openboreholes are capped overnight.

Trial pits Impacts on burrowing animalsincluding badgers, loss of valuedplant communities, risk ofanimals falling into uncoveredtrenches.

Adjust spatial pattern of samples. Avoid anyground disturbance within 30 metres of anoccupied badger sett.Plan sampling pattern to avoid sensitive plantcommunities, or, lift turves, retain turves andsubsoil and replace in original pattern afterworks. Ensure any open trenches are coveredovernight.

Window andPenetrometer Sampling

Impacts on burrowing animalsincluding badgers,Noise impacts may disturbbreeding birds (applies to allmechanised and percussivesampling techniques).

Adjust spatial pattern of samples. Avoid anyground disturbance within 30 metres of anoccupied badger sett. Avoid the bird breedingseason where breeding sites may be affected orelse seek ornithological advice.

Watercourse sedimentsampling

Breeding waterbirds, watervoles Conduct ornithological survey or avoid the bird-breeding season, avoid damage to watersideburrow systems.



Archaeology

Council for British Archaeology (1998) Annual Report York.

Department of the Environment (1990) Planning Policy Guidance 16: Archaeology and planning London.

Department of the Environment Planning Policy Guidance 15: Planning and the historic environmentLondon.

Department of the Environment, Transport and the Regions Environmental Geology in Land Use Planning:A Guide to Good Practice; Advice for Planners and Developers; Emerging Issues.

Highways Agency (1995) Trunk Roads and Archaeological Mitigation. Advice Note 75/95

Institute of Field Archaeologists (1993 revised 1999) Standard and Guidance for Archaeological Desk BasedAssessment.

Institute of Field Archaeologists (1994 revised 1999) Standard and Guidance of archaeological fieldevaluation.

Scottish Office (1994) National Planning Policy Guideline 5: Archaeology and Planning Edinburgh.

Scottish Office (1994) Planning Advice Note 42; archaeology-the planning process and scheduled ancientmonuments.

Shilston D.T., Harrison E., Parsons A.S. and Lee K. (1998) Giants’ Shoulders: The Cost-effective Use ofGeotechnical Desk Studies in Civil and Structural Engineering. Association of Geotechnical Specialists’Symposium on The Value of Geotechnics in Construction.

Welsh Office (1996) Planning and the Historic environment: Archaeology. Welsh Office Circular 60/96’Cardiff.

Ecology

Coventry S. and Woolveridge C. (1999) Environmental Good Practice on Site CIRIA London.

Hydrogeology and Hydrology


Environment Agency (1998) Policy and Protection of Groundwater (including series of groundwatervulnerability maps of England and Wales).

National Rivers Authority (1995) Guide to Groundwater Vulnerability Mapping in England and Wales

National Rivers Authority (1995) Guide to Groundwater Protection Zones in England and Wales

Scottish Environment Protection Agency and Environment Agency Guidance Note PPG1 General Guide to thePrevention of Water Pollution

Scottish Environment Protection Agency and Environment Agency Guidance Note PPG2 Above Ground


Oil Storage Tanks

Scottish Environment Protection Agency and Environment Agency Guidance Note PPG5 Works In, Near orLiable to Affect Watercourses

Scottish Environment Protection Agency and Environment Agency Guidance Note PPG6 Working atConstruction and Demolition Sites

13. OPERATIONAL SITES – ADDITIONALCONSIDERATIONS

13.1 - Checklist for working on operational sites

13.1 - Checklist for working on operational sites


Appropriate channels of communication with the site operator

Working in close proximity to personnel not involved in theinvestigation

Frequent vehicle movements, sometimes heavy goods vehicles

Noise levels from equipment used and the work type, especiallyclose to hospitals and residential areas

Ground vibration caused by percussion boring or rotary drilling closeto computer facilities and similar sensitive equipment

Air pollution from working equipment or odours and dusts arisingfrom the excavation, in populated areas

Working close to adjacent and overhead equipment

Working in confined environments, with little or no ventilation

Over water work, with moving river traffic

Working over buried tanks/voids/structures etc

Appendix A

Standard format for a factual site investigation report

begins on the following page

Cover to include:

Main Title (include site name and any site reference)

Report Version (e.g. Draft/Revised Draft/Final/Client Issue)

Confidentiality Status

Reporting Company

Document Reference

inside cover to include:

Main title (as on front cover)

Report status (as on front cover)

Report author(s) (typed, signed and dated)

Report checker(s) (typed, signed and dated)

Report reviewer(s) (typed, signed and dated)

Client:Reporting company (as on front cover)

Reporting company address

Report reference

CONTENTS

EXECUTIVE SUMMARY i

1. Introduction 1

1.1 Background 1

1.2 Brief and limitations 1

1.3 Preliminary conceptual model and objectives 1

1.4 Information sources used 1

1.5 Report structure 1

2. Site location and description 2

2.1 Introduction 2

2.2 Site location 2

2.3 Site description 2

2.4 Ecological survey information 3

2.5 Archaeological information 3

3. Site geology, hydrogeology and hydrology 4

3.1 Introduction 4

3.2 Geology 4

3.3 Hydrogeology 4

3.4 Hydrology 4

4. Site history 5

4.1 Introduction 5

4.2 History 5

4.3 Information from statutory authorities 5

4.4 Information from other parties 5

4.5 Potential contamination sources 5

5. Previous site investigation information 6

5.1 Introduction 6

5.2 Findings and recommendations made 6

6. Site investigation design and methodology 7

6.1 Background and site investigation design 7

6.2 Methodology 7

6.3 Analytical suites 8

7. Factual results 9

7.1 Introduction 9

7.2 Summary of physical ground conditions 9

7.3 Made ground - physical conditions 9

7.4 Natural ground - physical conditions 9

7.5 Groundwater - physical conditions 9

7.6 Summary of chemical conditions 10

7.7 Made ground and natural ground – chemical conditions 10

7.8 Perched water/groundwater – chemical conditions 10

7.9 Gas or other monitoring/in situ test results 10

8. Other report sections 11

REFERENCES 12

FIGURES AND DRAWINGS 13

APPENDICES 14

INCLUDE REPORTING COMPANY NAME IN HEADER

INCLUDE REPORT REFERENCE IN FOOTER i

EXECUTIVE SUMMARY

Summarise the pertinent issues i.e. the main findings and recommendations.


INCLUDE REPORT REFERENCE IN FOOTER 1

1. INTRODUCTION

1.1 Background

Provide reasons for works being undertaken, including whom has commissioned thework/when/how (e.g. by letter of X/X/X) and, where appropriate, intended future usage of thesite.

1.2 Brief and limitations

State what is included and also what has been specifically excluded. Mention any:

• liability to Third Parties;

• time constraints (e.g. applied by Client);

• any site constraints (e.g. access, financial).

1.3 Preliminary conceptual model and objectives

Provide brief details.

1.4 Information sources used

List, briefly, all information sources and nature of information (include source of any“anecdotal information” and all references used in the References section). Mention also, anyinformation that was sought but not obtained/still awaited.

1.5 Report structure

Provide a brief summary.



2. SITE LOCATION AND DESCRIPTION

2.1 Introduction

State that this chapter of the report includes Hazard Identification and, where there is someassessment of potentially relevant exposure scenarios/hazardous conditions, HazardAssessment.

2.2 Site location

Include:

• location description (e.g. located in the centre of X city, between X river and X canaland accessed off X road);

• OS National Grid Reference;

• full address (including postcode);

• Site Location Figure (scale 1:25,000 or better).

2.3 Site description

Include:

• current site size in hectares;

• whether previously part of a larger site;

• current use;

• ownership;

• general topography, noting ground level of land surrounding the site relative to that ofthe site;

• general description of ground surfaces;

• evidence of visual contamination from walk-over observations;

• notes of any site features that may have the potential to cause ground/groundwatercontamination;

• a description of surrounding land uses (identify local receptors e.g. school playingfields, sensitive habitats, housing and boundaries of neighbouring properties);



• current site layout plan (showing site boundary(s) clearly) with notes from sitereconnaissance visit and previous process activity locations (if appropriate); and

• site visit photographs.

NB As appropriate, summarise descriptions from reports of earlier stages and include latestdescription in full. Include full references for the previous reports.

2.4 Ecological survey information

State if an ecological survey has been included during this or any previous stage and providedetails.

2.5 Archaeological information

State if archaeological work has been included during this or any previous stage and providedetails.



3. SITE GEOLOGY, HYDROGEOLOGY ANDHYDROLOGY

As appropriate, summarise descriptions from other reports and include latest description infull. Include full references for the previous reports.

3.1 Introduction

State that this chapter of the report includes both Hazard Identification and, where there issome assessment of potentially relevant exposure scenarios/hazardous conditions, HazardAssessment.

3.2 Geology

Include:

• a description of the site geology from published geological maps and borehole logsfrom the local area (differentiate between solid and drift);

• a statement as to whether data obtained in site investigations have confirmed thepublished information (full detail to be provided in Chapter 7).

Consider including a conceptual drawing of the geological profile, particularly if the naturalstratigraphy is complex and/or has since become complicated by anthropological activity (e.g.deeply founded tanks and piles etc).

3.3 Hydrogeology

Describe preliminary hydrogeological model (e.g. unconfined/confined aquifer, piezometerheads etc). Include aquifer classification, licensed abstractions (volume, use,distance/direction from the site) groundwater flow direction (if known) and any reportedpollution incidences.

3.4 Hydrology

Include description and details of local surface watercourses, e.g. distances and direction fromsite, flow direction, General Quality Assessment, licensed abstractions (volume, use,distance/direction from the site) and any reported pollution incidences.



4. SITE HISTORY

Summarise history from previous desk study/other reports and include any new information infull. Include full references for the previous reports.

4.1 Introduction

List information sources used (in more detail than in Section 1.3). State that this chapter ofthe report includes both Hazard Identification and, where there is some assessment ofpotentially relevant exposure scenarios/hazardous conditions, Hazard Assessment.

4.2 History

Provide a description from historical maps, aerial photographs, anecdotal evidence etc. for thesite and surrounding area (list specific sources/information used). In a site investigationreport, it may be appropriate to tabulate much of this information.

NB Avoid taking each map in turn and describing it as a chronology. Instead assimilate theinformation first and then describe the history using suitable headings. For example, for aPower Station Site:

• “Pre-Development (dates X to X)”;

• “Operational Period (dates X to X)”;

• “Decommissioning Period (dates X to X)”;

• “Post-Closure (dates X to X)”;

• “Redevelopment for Light Industrial Units (dates X to X”);

etc.

4.3 Information from statutory authorities

E.g. Environment Agency, local authority Environmental Health Department, Health andSafety Executive.

4.4 Information from other parties

E.g. previous employees, nearby residents, site manager.

4.5 Potential contamination sources

Include potential contamination sources, nature, scale etc. Summarise this information on aplan of the site if possible.



5. PREVIOUS SITE INVESTIGATION INFORMATION

As appropriate, summarise information and data included in reports of earlier stages in themain body of the report. If there has been a series of previous investigations, deal with theseone at a time using a separate section for each (using the headings below in each section).Include the full reference for each previous report.

If there has been only one previous investigation report and this is brief, consider including itin full in an Appendix to the current report. If there are several reports of previousinvestigations, consider including the investigation logs and analytical data in anAppendix/series of Appendices to the current report.

5.1 Introduction

Provide a summary of why the investigation was undertaken, by whom, what it included andwhen and how it was carried out. State that this chapter of the report includes both HazardIdentification and, where there is some assessment of potentially relevant exposurescenarios/hazardous conditions, Hazard Assessment.

5.2 Findings and recommendations made

Provide a summary of the physical and chemical conditions encountered (include any gasmonitoring results, groundwater levels etc.) and any recommendations made following theinvestigation.

Include a drawing showing the locations of trial pits/boreholes etc. at a suitable scale.



6. SITE INVESTIGATION DESIGN ANDMETHODOLOGY

6.1 Background and site investigation design

Include:

• specific objectives of the site investigation;

• a description of the preliminary Conceptual Model (as described briefly in theIntroduction) and explain how this has been used to design the investigation;

• a description of the site investigation design, including any phasing of investigations;

• give the rationale used in locating boreholes and trial pits etc (e.g. “borehole BH328located on downstream side of a former diesel tank”, “river sample R303 taken justdownstream of an outfall pipe”).

6.2 Methodology

Include:

• the start and finish dates of the site investigation;

• weather conditions (including atmospheric pressure data/trends where gas monitoringhas been undertaken);

• a brief description of the personnel on site and their roles;

• a brief description of the work that was actually undertaken;

• a drawing showing the locations of trial pits/boreholes etc at a suitable scale;

• brief details of the site investigation contractor(s) and laboratory(s) (include laboratoryUKAS testing accreditation number(s), details of other accreditation and QA/QCprocedures);

• brief details of any preparatory work (e.g. moving of mounds of waste, breakingthrough concrete etc) and all investigation activities included in the activity (e.g.intrusive work, tank inspections/sampling of contents, gas/groundwater monitoring,topographic survey etc);

• for boreholes and trial pits, state maximum depth achieved, drilling method(boreholes) and whether groundwater/gas monitoring installations were included;

• details of any in situ testing;



• for gas/other monitoring exercises state the methods, equipment used (e.g. PID with10.2eV lamp), duration and frequency of monitoring and ambient conditions etc.;

• description of sampling methods and confirmation that samples weretaken/stored/transported in accordance with good practice (specific details ifnecessary);

• field QA/QC procedures and results;

• any limitations/constraints on field works.

6.3 Analytical suites

Describe the basis of the analytical strategy e.g. how and why analytical suites and sampleswere chosen.

Include a summary of chemical analytical suites, samples scheduled for these (includingstrata/locations/depths), brief details of the sample preparation and analytical methods usedtogether with any limitations/constraints on laboratory analysis.



7. FACTUAL RESULTS

7.1 Introduction

An introductory paragraph should be included, particularly if this chapter may be separatedfrom the rest of a report and copied to other parties. In the introduction re-state very brieflythe date of the investigation, the number/type of investigation locations any other pertinentbackground information. State that this chapter of the report is mainly a factual HazardIdentification stage of risk assessment although some Hazard Assessment may be included.

7.2 Summary of physical ground conditions

Include a general overview of:

• the physical conditions encountered on site (refer also to the geological informationprovided in Chapter 3 and confirm whether the expected geology was proven);

• any olfactory and/or visual evidence of presence/absence of contamination;

• the type and nature of contamination and its spatial distribution.

Where possible, present physical conditions in tabular/illustrative forms.

7.3 Made ground - physical conditions

Provide a full description of the made-ground encountered including any olfactory and/orvisual evidence relating to presence/absence of contamination. Where appropriate providedescriptions for different areas and identify any emerging “patterns”.

7.4 Natural ground - physical conditions

Provide a full description of the natural ground encountered including any olfactory and/orvisual evidence of presence/absence of contamination.

7.5 Groundwater - physical conditions

Provide a description of groundwater encountered, including rate of inflow to trialpits/boreholes, depth from ground surface (mBGL) and level (mAOD) of inflow and standingafter settlement. Include colour(s) of water and odours and evidence/thickness of freeproduct. It will usually be necessary to tabulate the groundwater measurements.



7.6 Summary of chemical conditions

Include a general overview of:

• the chemical conditions encountered on site;

• the type and nature of contamination and its spatial distribution and whether thisaccords with the physical conditions observed, any olfactory and visual contaminationindicators, gas readings etc.;

• identify any invalid or suspect data.

Where possible, present chemical conditions in tabular/illustrative forms.

7.7 Made ground and natural ground – chemical conditions

Provide a full description and describe possible contamination sources.

7.8 Perched water/groundwater – chemical conditions

Provide a full description and describe possible contamination source(s).

7.9 Gas or other monitoring/in situ test results

(where relevant)

Present results in tabular/illustrative forms. State what instruments were used as a footnote tothe table(s) and include detection/quantification limits or the instruments used where no gaswas recorded. Provide a description of the findings and relate to physical and chemicalconditions.



8. OTHER REPORT SECTIONS

Other report sections may be required depending on the requirements of the siteinvestigation, for example:

• Hazard assessment;

• Risk estimation;

• Risk evaluation;

• Recommendations;

• Cost estimates for remedial work;

• Summary (NB – different to an “executive summary”).



REFERENCES

Include:

• full references of reports of previous site investigations;

• guidance documents referred to;

• methods of test/analysis etc;

• standards/codes/guidance documents;

• any local history books used;

• any local geological memoirs;

• any other documents/reports/correspondence referred to in the report.



FIGURES AND DRAWINGS

Include, as a minimum:

• site location plan (scale 1:25,000 or better);

• current site layout plan with notes from site reconnaissance visit(s), previous processactivity locations (if appropriate);

• drawing showing ground investigation locations (may or may not include topographicsurvey details).

Include the following where appropriate:

• assimilated information from historical maps/aerial photographs etc;

• geological map extract;

• conceptual drawing of the site geology;

• illustrative sketches/diagrams of the site physical and chemical conditions;

• any cross-sections, plans and other drawings needed to illustrate specific findings fromthe desk study, site reconnaissance and site investigation phases.



APPENDICES

To contain any information supplementary to that in the main body of the report e.g.:

• selected/full set of historical maps/aerial photographs;

• general site photos;

• previous site investigation report(s) and/or data;

• pertinent copies of correspondence and file notes of relevant conversations withnamed individuals;

• extracts of historical documents/plans/drawings etc;

• trial pit/borehole logs and photos of these;

• site and laboratory chemical data and QA/QC information;

• field data including results of any monitoring data recorded on site and groundwaterdata;

• copies of any relevant calibration check forms/certificates.

technical aspects of site investigation volume 2

Documents

site investigation preparation

environment agency staff

investigation design

technical issues

technical staff

checklist of major issues

site characterisation

daily site diary