CIRIA C549 London, 2001

Remedial processes for contaminated land � principles and practice D Evans BSc PhD S A Jefferis BSc MSc PhD A O Thomas BSc MSc PhD S Cui BEng PhD

6 Storey�s Gate, Westminster, London SW1P 3AU TELEPHONE 020 7222 8891 FAX 020 7222 1708 EMAIL enquiries@ciria.org.uk WEBSITE www.ciria.org.uk

2 CIRIA C549

Remedial processes for contaminated land � principles and practice D Evans, D; Jefferis, S A; Thomas, A O; Cui, S

Construction Industry Research and Information Association

CIRIA C549 © CIRIA 2001 ISBN 0 86017 549 9

Keywords

Contaminated land, remediation, bioremediation, enhanced bioremediation, natural attenuation, soil vapour extraction, air sparging, bioventing, dual-phase vapour extraction, soil washing, cement fixation

Reader interest

Geotechnical engineers, environmental professionals, reclamation specialists, developers, regulators, planners, civil engineers

Classification

AVAILABILITY Unrestricted CONTENT Best practice guidance STATUS Commissioned, committee

guided USER Geotechnical and civil

engineers, environmental professionals

Published by CIRIA, 6 Storey�s Gate, Westminster, London, SW1P 3AU, enquiries@ciri a.org.uk, All rights reserved. No part of this publication may be reproduced or transmitted in any form or by any other means, including photocopying and recording, without the written permission of the copyright-holder, application for which should be addressed to the publisher. Such written permission must also be obtained before any part of this publication is stored in a retrieval system of any nature.

CIRIA C549 3

Summary

This book provides guidance for good practice in the selection, design, commissioning, operation, monitoring and validation of process technologies for the remedial treatment of contaminat ed land. It is the result of a CIRIA research project that identified UK usage of these process technologies and, by an international review of experi ence and consultation with practitioners, established guidelines for good practice in these relatively new methods.

The first two chapters describe the method and the general findings of the research and set the technologies in a framework of their use in UK and general criteria for their appropriat eness as a treatment method. Nine generic technologies � those with some history of use in UK � are described using a consistent set of headings.

The technologies are:

�� ex-situ bioremediation �� enhanced in-situ bioremediation �� natural attenuation �� soil vapour extraction �� air sparging �� bioventing �� dual-phase vapour extraction �� soil washing �� cement fixation.

Each is described in terms of:

�� its definition �� the scientific principles underlying the process �� its applicability and selection �� plant and equipment typically required �� limitations on its use �� aspects of planning and management of the treatment including data requirements �� timescales, health and safety, regulatory and environmental requirements, criteria

for remediation �� basics of design �� guidance on speci fications �� operations monitoring and evaluation �� closure and validation.

The final chapter uses the same headings to show what is needed in the research and development of a new treatment technology. Appendices give additional information about speci fication of the technologies. The text is supported by a comprehensive set of references.

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CIRIA C549 5

Acknowledgements

This report is the outcome of a research project in CIRIA�s geo-environmental engineering programme. It is one in a series of technical guidance documents and case studies on the remedial treatment of contaminated land. The purpose of this research project was to identify those treatment technologies where there was suffici ent experience, particularly in UK, to be able to establish and present guidance on what would be accepted as good practice in these relatively new and developing technologies. Golder Associates (UK) Limited undertook the research under contract to CIRIA. The authors of the report were Dr D Evans, Dr S A Jefferis, Dr A O Thomas and Dr S Cui.

In line with CIRIA practice, the project was guided by a steering group, which comprised:

Mr S Smith (chairman) Welsh Development Agency Mr P J Barker Bachy Soletanche Limited Mr P A Braithwaite Ove Arup and Partners Mr R W Clarke then of Cheshire County Council Mr E E Hughes Edmund Nuttall Limited Mr M Holroyd Telluric Limited Mr I Martin Environment Agency Dr K Prastka BNFL Mr S L Redfearn The BOC Foundation Mr J Steeds W S Atkins Environment Mr L W Todd Dames & Moore Mr J Waters Environmental Resources Management Limited Mr E Wilson Prudential Portfolio Managers

CIRIA�s research managers for the project were Dr M R Sansom and Mr F M Jardine.

FUNDERS

CIRIA acknowledges the support of the following organisations for funding Phase III of CIRIA�s �Programme on contaminated land�, under which this project was completed:

�� Department of the Environment, Transport and the Regions, Construction Directorate

�� The BOC Foundation �� British Waterways �� The Environment Agency (previously National Rivers Authority) �� Highways Agency �� National House-Building Council �� Scottish Enterprise.

CIRIA and the authors are grateful for the support of these funding organisations and the technical help and advice provided by steering group members. Contributions do not imply that individual funders necessarily endorse all views expressed in published outputs.

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The authors wish to acknowledge those who gave special help and comments, in particular:

�� Dr S Wallace of BGPD for conducting a site tour of the soils washing project at Basford Gasworks

�� Golder staff in Nottingham, Toronto, Calgary, Vancouver and Atlanta �� Mr R Keen at Bio-logic Remediation Limited �� Dr R Bewley of Dames & Moore �� VHE Limited �� Bachy Soletanche Limited �� all participants in the consultation workshops.

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Contents

Summary................................................................................................ 3 Acknowledgements .................................................................................. 5 List of figures ........................................................................................ 11 List of boxes ......................................................................................... 13 List of tables ......................................................................................... 14 Abbreviations ........................................................................................ 17

1 Introduction.......................................................................................19 1.1 Background ................................................................................. 19 1.2 Aims .......................................................................................... 19 1.3 Scope, layout and report contents ..................................................... 20 1.4 Methodology used in the collection and assessment of data ................... 22

2 Selection and experience in the application of various technologies........................................................................................23

3 Ex-situ bioremediation � engineered treatment beds..........................29 3.1 Definition.................................................................................... 29 3.2 Principles .................................................................................... 29 3.3 Applicability and selection.............................................................. 32 3.4 Plant and equipment ...................................................................... 35 3.5 Limitations .................................................................................. 36 3.6 Planning and management .............................................................. 37 3.7 Design ........................................................................................ 42 3.8 Speci fication ................................................................................ 48 3.9 Operations monitoring and evaluation............................................... 52 3.10 Closure and validation ................................................................... 55

4 Enhanced in-situ bioremediation........................................................57 4.1 Definition.................................................................................... 57 4.2 Principles .................................................................................... 57 4.3 Applicability and selection.............................................................. 59 4.4 Plant and equipment ...................................................................... 61 4.5 Limitations .................................................................................. 61 4.6 Planning and management .............................................................. 62 4.7 Design ........................................................................................ 65 4.8 Speci fication ................................................................................ 69 4.9 Operations monitoring and evaluation............................................... 69 4.10 Closure and validation ................................................................... 72

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5 Soil vapour extraction........................................................................73 5.1 Definition.................................................................................... 73 5.2 Principles .................................................................................... 73 5.3 Applicability and selection.............................................................. 74 5.4 Plant and equipment ...................................................................... 77 5.5 Limitations .................................................................................. 77 5.6 Planning and management .............................................................. 80 5.7 Design ........................................................................................ 85 5.8 Speci fication ................................................................................ 90 5.9 Operations monitoring and evaluation............................................... 91

5.10 Closure and validation ................................................................... 94

6 Dual-phase vacuum extraction...........................................................97 6.1 Definition.................................................................................... 97 6.2 Principles .................................................................................... 97 6.3 Applicability and selection.............................................................. 99 6.4 Plant and equipment .....................................................................100 6.5 Limitations .................................................................................100 6.6 Planning and management .............................................................100 6.7 Design .......................................................................................105 6.8 Speci fication ...............................................................................110 6.9 Operations monitoring and evaluation..............................................110

6.10 Closure and validation ..................................................................114

7 Air sparging.....................................................................................115 7.1 Definition...................................................................................115 7.2 Principles ...................................................................................115 7.3 Applicability and selection.............................................................116 7.4 Plant and equipment .....................................................................118 7.5 Limitations .................................................................................119 7.6 Planning and management .............................................................119 7.7 Design .......................................................................................123 7.8 Speci fication ...............................................................................125 7.9 Operations monitoring and evaluation..............................................127

7.10 Validation...................................................................................129

8 Bioventing........................................................................................131 8.1 Definition...................................................................................131 8.2 Principles ...................................................................................131 8.3 Applicability and selection.............................................................132 8.4 Plant and equipment .....................................................................134 8.5 Limitations .................................................................................134 8.6 Planning and management .............................................................135 8.7 Design .......................................................................................140 8.8 Speci fication ...............................................................................141 8.9 Operations monitoring and evaluation..............................................143

8.10 Closure and validation ..................................................................145

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9 Natural attenuation..........................................................................147 9.1 Definition...................................................................................147 9.2 Principles ...................................................................................147 9.3 Applicability and selection.............................................................148 9.4 Plant and equipment .....................................................................150 9.5 Limitations .................................................................................150 9.6 Planning and management .............................................................150 9.7 Assessment .................................................................................153 9.8 Monitoring and validation..............................................................156

10 Soil washing.....................................................................................159 10.1 Definition...................................................................................159 10.2 Principles ...................................................................................159 10.3 Applicability and selection.............................................................162 10.4 Plant and equipment .....................................................................163 10.5 Limitations .................................................................................165 10.6 Planning and management .............................................................166 10.7 Design .......................................................................................169 10.8 Speci fication ...............................................................................171 10.9 Operations monitoring and evaluation..............................................173 10.10 Closure and validation ..................................................................174

11 Cement-based fixation processes......................................................175 11.1 Definition...................................................................................175 11.2 Principles ...................................................................................175 11.3 Applicability and selection.............................................................176 11.4 Plant and equipment .....................................................................181 11.5 Limitations .................................................................................182 11.6 Planning and management .............................................................185 11.7 Design .......................................................................................189 11.8 Speci fication ...............................................................................192 11.9 Operations monitoring and evaluation..............................................193 11.10 Validation...................................................................................195

12 Research and development of a new technology...............................201 12.1 Definition...................................................................................201 12.2 Principles ...................................................................................201 12.3 Applicability and selection.............................................................201 12.4 Plant and equipment .....................................................................202 12.5 Limitations .................................................................................202 12.6 Planning and management .............................................................202 12.7 Design .......................................................................................202 12.8 Speci fication ...............................................................................202 12.9 Monitoring, performance evaluation and validation ............................202

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References........................................................................................203

Appendices.......................................................................................217 A1 Speci fication aspects for soil vapour extraction ..................................217 A2 Speci fication aspects for dual-phase vacuum extraction .......................222 A3 Speci fication aspects for air sparging ...............................................223 A4 Speci fication aspects for bioventing.................................................225 A5 Natural attenuation .......................................................................227

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Figures

Figure 1.1 Area of topic overlap .................................................................. 21

Figure 3.1 Ex-situ bioremediation: (a) soil treatment, (b) aerated static pile (biopile) .. 31 (c) windrow system .................................................................... 32

Figure 3.2 Relationship between treatment time and soil type............................ 34

Figure 3.3 Example of a laboratory microcosm............................................... 43

Figure 3.4 Effects of soil mixing on soil oxygen concentration .......................... 46

Figure 3.5 Typical design concepts for an aerated biopile ................................. 47

Figure 4.1 Schematic diagrams of (a) an active EISB system............................. 58 (b) a passive system.................................................................... 59

Figure 4.2 Possible patterns for extraction and extraction-injection well systems... 68

Figure 4.3 Typical design details for infiltration trench .................................... 68

Figure 5.1 Schematic layout of a typical SVE system....................................... 73

Figure 5.2 Relationship between vapour movement and soil permeability............ 74

Figure 5.3 A schematic decision tree for screening SVE and bioventing.............. 76

Figure 5.4 Relationship between subsurface airflow and soil moisture content...... 79

Figure 5.5 Example of radius-of-influence design approach .............................. 87

Figure 5.6 Influence of pulsing on vapour recovery: (a) typical removal via continuous operation and (b) removal during pulsing........................ 93

Figure 6.1 Schematic layout of a typical dual-phase vacuum extraction system..... 98

Figure 6.2 Well design for (a) conventional recovery systems, (b) separat e recovery systems and (c) single conduit systems.............................108

Figure 7.1 Schematic layout of a typical air sparging system............................115

Figure 7.2 Schematic representation of the behavioural stages occurring during continuous air sparging.....................................................116

Figure 7.3 Schematic presentation of hydrocarbon mass removal with air sparging ..................................................................................117

Figure 7.4 The influence of stratigraphy on horizontal channelling....................118

Figure 7.5 Air sparging test measurements....................................................124

Figure 7.6 Impact of pulsing on performance ................................................128

Figure 8.1 Schematic layout of typical bioventing system................................131

Figure 8.2 Hydrocarbon volatilisation and biodegradation rates as a function of airflow rates .........................................................................132

Figure 8.3 Relationship between volatility and biodegradability with respect to selection of bioventing ...............................................................133

Figure 8.4 In-situ respiration test apparatus ...................................................138

Figure 9.1 Example of a natural attenuation monitoring plan............................152

Figure 9.2 Possible redox zones in contaminated groundwater..........................153

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Figure 9.3 Natural attenuation flow chart ......................................................155

Figure 10.1 Example of a soil washing system................................................159

Figure 10.2 Process flow diagram of a soil washing system...............................160

Figure 10.3 Schematic representation of waste segregation practice ....................171

Figure 11.1 Solubility of metal hydroxide as a function of pH ............................176

Figure 11.2 In-situ delivery system...............................................................177

Figure 11.3 Ex-situ delivery system ..............................................................177

Figure 11.4 Flow diagram for evaluating selection of fixation technologies ..........178

Figure A1.1 Piping and instrumentation diagram for typical SVE manifold system ....................................................................................219

Figure A3.1 Typical example of an instrumentation diagram for air sparging.........224

Figure A4.1 Schematic diagram of a typical vent well .......................................225

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Boxes

Box 3.1 Stoichiometry of aerobic biodegradation......................................... 29

Box 3.2 Case study of ex-situ degradation of PAH and TPH.......................... 34

Box 5.1 Use of hydraulic fracturing for enhanced site remediation .................. 78

Box 5.2 Potential effects of upwelling ....................................................... 79

Box 5.3 Screening software package ......................................................... 88

Box 5.4 Guidance on undertaking pilot testing............................................ 89

Box 5.5 Operational aspects of an SVE programme...................................... 92

Box 6.1 Guidance on undertaking pilot testing (assuming use of a single pump)............................................................................106

Box 6.2 Guidance on well screen design for slurper wells.............................109

Box 6.3 Overcoming balancing problems for dual-phase extraction systems (single-pump systems) ...............................................................112

Box 7.1 Example of post-remediation groundwater concent ration following air sparging..............................................................................130

Box 8.1 Assessing in-situ aerobic hydrocarbon degradation ..........................138

Box 8.2 Determination of injection flow rates for bioventing ........................142

Box 10.1 Key findings of a soil-washing pilot study......................................170

Box 10.2 Summary of the Greenwich Millennium site, soil-washing project ......172

Box 11.1 Case study example of pre- and post-treatment monitoring at the in-situ stabilised chemical landfill at Ardeer, Scotland.................198

Box A1.1 Charact eristics of blower type......................................................217

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Tables

Table 3.1 Critical environmental factors for microbial activity.......................... 30

Table 3.2 Treatability of hydrocarbon fractions ............................................. 33

Table 3.3 Typical issues in project planning/programming............................... 38

Table 3.4 Typical data requirement for ex-situ bioremediation technologies ........ 39

Table 3.5 Environmental factors influencing design ....................................... 46

Table 3.6 Speci fications for ex-situ bioremediation ........................................ 50

Table 3.7 Suggested environmental parameters for pre-t reatment ...................... 51

Table 3.8 Material speci fication checklist ..................................................... 52

Table 3.9 Suggested sampling schedule for ex-situ treatment beds .................... 53

Table 3.10 Treatment bed trouble-shooting guide............................................ 55

Table 4.1 Summary of the influence of environmental redox potential on microbial degradation processes .................................................... 57

Table 4.2 Generalised parameters for applicability of EISB ............................. 59

Table 4.3 Influence of various electron acceptors on hydrocarbon degradation .... 61

Table 4.4 Typical issues in project planning and programming......................... 62

Table 4.5 Typical data requirement for implementing enhanced in-situ bioremediation .......................................................................... 63

Table 4.6 Physical and biological consideration for EISB design ...................... 65

Table 4.7 Comparison between laboratory and field-derived contaminant hal f-lives .................................................................................. 66

Table 4.8 Speci fication for enhanced in-situ bioremediation design................... 70

Table 4.9 EISB system operation strategy and trouble-shooting guide................ 72

Table 5.1 Examples of volatile contaminants considered amenable to SVE......... 75

Table 5.2 Typical issues in project planning and programming......................... 81

Table 5.3 Typical data requirement for selection of a soil vapour extraction system ..................................................................................... 82

Table 5.4 Typical site requirements for soil vapour extraction .......................... 83

Table 5.5 Typical environmental hazards ..................................................... 83

Table 5.6 Potential advantages and disadvantages of various design approaches .. 86

Table 5.7 Pilot tests employed for SVE systems ............................................ 89

Table 5.8 Speci fication for SVE design........................................................ 91

Table 5.9 Available SVE monitoring regimes................................................ 92

Table 5.10 SVE systems trouble-shooting guide.............................................. 95

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Table 6.1 Geological and hydrogeological consideration in the selection of dual-phase vacuum extraction technologies ..................................... 99

Table 6.2 Typical issues in project planning and programming........................101

Table 6.3 Typical data requirement for selection of a dual-phase vacuum extraction system ......................................................................102

Table 6.4 Typical site requirements for dual-phase vacuum extraction ..............103

Table 6.5 Typical environmental hazards ....................................................103

Table 6.6 Advantages and disadvantages of various pumping configurations ......109

Table 6.7 Speci fication for dual-phase vacuum extraction...............................111

Table 6.8 Dual-phase vacuum extraction monitoring parameters ......................112

Table 6.9 Dual-phase vacuum extraction system trouble-shooting guide............113

Table 7.1 Generalised parameters for applicability of air sparging....................117

Table 7.2 Typical issues in project planning and programming........................120

Table 7.3 Typical data requirement for selection of air sparging ......................121

Table 7.4 Pilot tests for air sparging ...........................................................124

Table 7.5 Speci fication for air sparging systems ...........................................126

Table 7.6 Typical range of operating conditions for air sparging ......................127

Table 7.7 In-situ air sparging monitoring parameters .....................................127

Table 7.8 Air sparging system trouble-shooting guide....................................129

Table 8.1 Typical issues in project planning and programming .......................136

Table 8.2 Typical data requirement for selection of bioventing........................137

Table 8.3 Speci fication items for bioventing ................................................142

Table 8.4 Bioventing system operation strategy and trouble-shooting guide.......144

Table 9.1 Typical parameters for site characterisation....................................151

Table 10.1 Applicability of contaminants to soil washing.................................162

Table 10.2 Summary of potential soil washing process units.............................164

Table 10.3 Typical issues in project planning programming..............................166

Table 10.4 Soil characterisation requirements ................................................167

Table 10.5 Typical site requirements ............................................................168

Table 10.6 Speci fications for soil washing ....................................................173

Table 11.1 Applicability for cement fixation to contaminants............................179

Table 11.2 Advantages and disadvantages of in-situ and ex-situ systems and their applicabilities ....................................................................180

Table 11.3 Charact eristics of cement-based process ........................................181

Table 11.4 Influence of physical properties on cement-based processes ..............183

Table 11.5 Chemical interferences with the fixation process .............................184

Table 11.6 Common difficulties in project planning........................................185

Table 11.7 Information requirements for cement-based process design ...............186

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Table 11.8 Site requirements for cement-based processes .................................186

Table 11.9 Additives and their applications to fixation.....................................190

Table 11.10 Treatability test procedures .........................................................191

Table 11.11 Speci fication items for fixation systems.........................................192

Table 11.12 Cement-based problem-scoping guide...........................................196

Table A1.1 Equivalent pipe length conversions due to friction losses ..................219

Table A3.1 Typical construction details for injection wells................................223

Table A4.1 Typical blower specifications for bioventing evaluation....................226

CIRIA C549 17

Abbreviations

ASTM American Society for Testing and Materials BGPD British Gas Property Division BNFL British Nuclear Fuels Limited BOC British Oxygen Company BSI British Standards Institution BTEX Benzene toluene ethylbenzene and xylene C:N:P carbon:nitrogen:phosphorus CDM Construction (Design and Management) Regulations CEC cation exchange capacity CIRIA Construction Industry Research and Information Association COSHH Control of Substances Hazardous to Health DCE dichloroethene DETR Department of the Environment, Transport and the Regions DNAPL dense non aqueous phase liquid DoE NI Department of the Environment for Northern Ireland DRH diesel range hydrocarbons DSM deep soil mixing EA Environment Agency eH redox potential EISB enhanced in-situ bioremediation FID fl ame ionisation detector GAC granular activated carbon HDPE high-density polyethylene HS(G) Health and Safety Guidance HSE Health and Safety Executive ID internal diameter LNAPL light non-aqueous-phase liquid MTBE methyl tertiary butyl ether NAPL non-aqueous-phase liquid PAH polyaromatic hydrocarbons PCB polychlorinated biphenyl PCE perchloroethene PCP pentachlorophenol PFA pulverised fuel ash pH acidity of a solution PID photo-ionisation detector PVC poly vinyl chloride ROI radius of influence SEPA Scottish Environment Protection Agency

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SG speci fic gravity SSM shallow soil mixing SVE soil vapour extraction TCE trichloroethene TCLP toxicity characteristic leaching procedure TPH total petroleum hydrocarbons UCS unconfined compressive strength USEPA United States Environmental Protection Agency VOC volatile organic compounds

CIRIA C549 19

1 Introduction

1.1 BACKGROUND

Recently, innovative in-situ techniques have been commercially applied to the treatment of contaminants in soil and groundwater and to solve other problems associated with the reclamation of contaminated sites. Greater use of process-ori entated technologies is considered likely by many practitioners and problem-holders, but will be influenced by variations in waste management practices, competition among specialist technology providers, and more widespread acceptance of quantitative risk-based remediation strategies and environmental legislation.

CIRIA�s programme of reference and guidance for managing contaminat ed land has common themes of characterisation, investigation, remedial treatment, testing and validation, construction and development, and monitoring the effects on surroundings. The programme was initiated in 1991 and has resulted in a series of good practice documents, and it continues to develop guidance for less well-established procedures.

The contaminated land programme was divided into phases. First to be prepared was a manual of broad overall guidance (Harris et al, 1995a�i; Harris et al, 1996; Harris et al, 1998). This was followed by state-of-the-art reports on speci fic remedial technologies (Privett et al, 1996; Ellis, 1997; Holden et al, 1998). Finally, the programmed aimed to establish, where possible, guidance for good practice in the application and development of important remediation technologies.

During the initial phases of the research programme (pre-1995), experi ence with the effective implementation of process-orient ated technologies in the UK was in its infancy. Consequently, much of the information detailed was based on international knowledge and practice. As more experience is being gained in the UK it is necessary to assimilate and promulgate the information to promote greater confidence in the selection, design and operation of these technologies.

This report, therefore, forms the final part of the third phase of CIRIA�s contaminated land programme. The first part was to report the findings of commercial projects and trials being undertaken by various, process-based methods in a series of case study reports. The second part was the research the project (on which this report is based) to establish the principles of good practice in the main remediation technologies and to present guidance about them.

1.2 AIMS

The purpose of this report is to provide guidance on good practice in the selection, design, operation and closure of contaminated land remediation projects involving a range of biological, physical and fixation technologies.

This report is primarily aimed at practitioners involved in design and implementation of remediation strategies, notably consultants, contractors and problem-holders. The report has also been designed to help non-specialists. Thus, site-owners and operators, funders, insurers, operational or corporate managers and regulatory bodies (Environment Agency, Scottish Environmental Protection Agency (SEPA), the Environment Heritage

20 CIRIA C549

Service in Northern Irel and and local authorities) can also obtain information about the remediation technologies to enable them to make commercial judgements and decisions.

1.3 SCOPE, LAYOUT AND REPORT CONTENTS

1.3.1 Remedial processes included

The main part of this report (Sections 3 to 11) deals with the operating principles and good practice for the selection, design, operation and validation of the following nine remediation technologies:

�� ex-situ biological treatments �� enhanced in-situ bioremediation �� soil vapour extraction �� dual-phase vacuum extraction �� air sparging �� bioventing �� natural attenuation �� soil washing �� cement-based fixation.

Before considering guidance on design, operation and validation of these technologies, some broad selection issues need to be addressed. These issues are highlighted in Section 2, and should be regarded as indicators for technology selection. A comprehensive description of each of the nine technologies is outside the scope of this report, as it has been written for practitioners with some knowledge of the subject. Readers should refer to CIRIA Special Publications 101�111 (Harris et al, 1995a�i; Harris et al, 1996; Harris et al, 1998) during initial screening of remediation options.

In the course of this research project, it became apparent that some technical issues were poorly understood, or not fully considered during the application of remedial measures. Reasons for this included incomplete understanding of scienti fic principles, theoretical uncertainties and lack of proven field experience. This was why each of the main technologies (Sections 3 to 11) was addressed using the following scheme of topics:

�� definition �� principles �� applicability and selection �� plant and equipment �� limitations �� planning and management �� design �� speci fication �� operations, monitoring and evaluation �� validation and closure.

Necessarily there are overlaps in the technical contents of some sections, particularly when discussing modifications in subsurface airflow regimes. These areas of overl ap are shown in Figure 1.1 and should be considered when making technology selection.

CIRIA C549 21

Section 12 provides guidance and comments about the research and development of a new remediation technology and draws from the experiences of more commercially proven technologies. As an aid to practitioners, the salient issues are demonstrated via a worked example of research and development of a new technology.

Figure 1.1 Area of topic overlap

1.3.2 Remedial processes excluded

The following remedial processes are speci fi cally not discussed in this report:

�� active containment (reactive barriers or � funnel and gate� technologies ) �� low-temperature thermal desorption �� electrokinetics �� non-cement -based fixation technologies �� solvent washing.

22 CIRIA C549

1.4 METHODOLOGY USED IN THE COLLECTION AND ASSESSMENT OF DATA

Various research methods were adopted during the study period to collate information to establish good practice. First, the main process variations for each generic treatment category were identi fied and the level of UK and international experience estimated.

Second, a systematic literature search of abstract databases, recent trade magazines, environmental newsletters and Internet sources was undertaken to identify UK and international experience, case studies, manual/review documents, demonstration projects, vendor literature and research projects. This resulted in the generation of a project database of several thousand entries.

Third, experts (consultants, technology vendors, earthworks and specialist environmental contractors, regulators, researchers and landowners ) were consulted, by means of meetings, telephone conversations and questionnaires.

To conclude the consultation process, two workshops were arranged, to which key industry practitioners were invited. This was especially useful, as, in a rapidly developing subject, case study information is vital. The experience detailed in this report is thus considered current, and much of it is previously unpublished.

As the report covers many and diverse technologies it has not been possible to provide detailed engineering design data on the technologies. Rather, the report has focused on information requirements that have to be addressed for the success ful application of a particular technology.