Table Of ContentBarrier Systems for
Waste Disposal
Barrier Systems for
Waste Disposal
2nd edition
R. Kerry Rowe,
Queen's University Kingston, Ontario, Canada
Robert M. Quigley,
Richard W.I. Brachman
Queen's University Kingston, Ontario, Canada
and
John R. Booker
E & FN SPON
An imprint of Chapman & Hall
London • Glasgow • New York • Tokyo • Melbourne • Madras
First edition published 1995 by E & FN Spon
This edition published 2004
by E & FN Spon
2 Park Square, Milton Park, Abingdon, Oxon, OX14 4KN
Simultaneously published in the USA and Canada
by E & FN Spon
711 Third Avenue, New York, NY 10017
E & FNSpon is an imprint of the Taylor & Francis Group
© 2004 R. Kerry Rowe, Robert M. Quigley, Richard W.I. Brachman and John R. Booker
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All rights reserved. No part of this book may be reprinted or
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invented, including photocopying and recording, or in any
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The publisher makes no representation, express or implied, with regard to the
accuracy of the information contained in this book and cannot accept any
legal responsibility or liability for any errors or omissions that may be made.
British Library Cataloguing in Publication Data
A catalogue record for this book is available from the British Library
Library of Congress Cataloging in Publication Data
A catalog record for this book has been requested
ISBN (M19-22630-3
Publisher's Note
The publisher has gone to great lengths to ensure the quality of this reprint
but points out that some imperfections in the original may be apparent.
Contents
Preface ix
1 Basic concepts 1
1.1 Introduction 1
1.2 Overview of barrier systems 1
1.3 Transport mechanisms and governing equations 12
1.4 Complicating factors 28
1.5 Modelling the finite mass of contaminant 31
1.6 Modelling a thin permeable layer as a boundary condition 32
1.7 Hand solutions to some simple problems 34
1.8 Design considerations 37
1.9 Impact assessment 40
1.10 Choice of barrier system and service life considerations 42
1.11 Summary 43
2 Leachate characteristics and collection 45
2.1 Introduction 45
2.2 Liquid hydrocarbons 47
2.3 Landfill leachate 50
2.4 Collection, clogging and mounding 73
2.5 Estimating the service life of leachate collection blankets 97
2.6 Leachate mounding and liner temperature 98
2.7 Summary 99
3 Clayey barriers: compaction, hydraulic conductivity and clay mineralogy 103
3.1 Introduction 103
3.2 Methods of assessing hydraulic conductivity 105
3.3 Compacted clay liners 123
3.4 Clay mineralogy 136
3.5 Clay colloid chemistry 143
4 Clay /leachate compatibility by measurement of hydraulic conductivity 148
4.1 Introduction 148
4.2 Soil-MSW leachate compatibility 151
4.3 Compatibility of clays with liquid hydrocarbon permeants 159
4.4 Summary 171
V
Contents
5 Flow modelling 173
5.1 Introduction 173
5.2 One-dimensional flow models 173
5.3 Analysis of 2D and 3D flow 185
5.4 A finite difference approximation 186
5.5 Application of the finite element method to the analysis of plane flow 187
5.6 Boundary element methods 189
5.7 Calculating flow through holes in geomembranes 190
6 Chemical transfer by diffusion 198
6.1 Introduction 198
6.2 Free solution diffusion (Z) ) 198
0
6.3 Diffusion through soil 201
6.4 Steady-state diffusion 202
6.5 Transient diffusion 209
6.6 Use of laboratory and field profiles to obtain diffusion coefficient D 212
e
6.7 Diffusion during hydraulic conductivity testing for clay/leachate compatibility 212
6.8 Diffusion through geomembranes 214
6.9 Summary 221
7 Contaminant transport modelling 223
7.1 Introduction 223
7.2 Analytical solutions 225
7.3 Application of Laplace transforms to develop a finite layer solution for a single layer 230
7.4 Contaminant transport into a single layer considering a landfill of finite mass and
an underlying aquifer 232
7.5 Finite layer analysis 234
7.6 Contaminant migration in a regularly fractured medium 242
7.7 Finite layer analysis of geomembranes and gas-filled layers where there is phase change 245
8 Evaluation of diffusion and distribution coefficients 247
8.1 Introduction 247
8.2 Obtaining diffusion and partitioning/distribution coefficients: basic concepts 247
8.3 Example tests for obtaining diffusion and distribution coefficients for
inorganic contaminants 250
8.4 Dispersion at low velocities in clayey soils 259
8.5 Effective porosity 259
8.6 Distribution coefficients and non-linearity 260
8.7 Effect of leachate composition, interaction and temperature 262
8.8 Diffusion and sorption of organic contaminants 265
8.9 Use of field profiles to estimate diffusion coefficients 267
8.10 Summary of diffusion parameters for saturated soil and rock 269
8.11 Diffusion in unsaturated porous media 269
8.12 Diffusion and partition coefficients for geomembranes 286
vi
Contents
9 Field studies of diffusion and hydraulic conductivity 299
9.1 Introduction 299
9.2 Examples of long-term field diffusion 299
9.3 Examples of short-term field diffusion 304
9.4 Hydraulic conductivity of contaminated clay liners 312
9.5 Performance of a composite lagoon liner during 14 years of operation 316
10 Contaminant migration in intact porous media: analysis and design considerations 322
10.1 Introduction 322
10.2 Mass of contaminant, the reference height of leachate, H, and the equivalent
t
height of leachate, H 322
{
10.3 Development of a contaminant plume 331
10.4 Effect of Darcy flux in a receptor aquifer 333
10.5 Effect of horizontal dispersivity in a receptor aquifer 334
10.6 Effect of aquifer thickness 334
10.7 Effect of landfill size on potential impact 336
10.8 l^D versus 2D analysis and modelling of the aquifer beneath a liner 336
10.9 Effect of sorption 339
10.10 Effect of liner thickness 339
10.11 Effect of Darcy flux in the barrier and design for negligible impact 340
11 Migration in fractured media: analysis and design considerations 343
11.1 Introduction 343
11.2 Numerical considerations 345
11.3 Lateral migration through fractured media 346
11.4 Vertical migration through fractured media and into an underlying aquifer 365
11.5 Summary 377
12 Geosynthetic clay liners (GCLs) 379
12.1 Introduction 379
12.2 Basic properties 380
12.3 Swelling behaviour 380
12.4 Hydraulic conductivity 382
12.5 Factors influencing hydraulic performance 383
12.6 Solute transport 392
12.7 Gas migration 396
12.8 Installation 399
12.9 Internal and interface shear strength 399
12.10 GCLs in composite liners 401
12.11 Equivalency GCLs and CCLs 403
13 Geomembrane liners 405
13.1 Introduction 405
13.2 Physical response of HDPE geomembranes 406
13.3 Durability of HDPE geomembranes 417
vii
Contents
13.4 Leakage through geomembranes 423
13.5 Diffusion of contaminants through HDPE geomembranes 441
13.6 Summary 444
14 Covers 446
14.1 Introduction 446
14.2 Controlling infiltration 446
14.3 Common final cover systems 447
14.4 Calculating percolation through the cover 449
14.5 Alternate cover systems 450
15 Geotechnical and related design issues 452
15.1 Introduction 452
15.2 Geotechnical considerations 452
15.3 Design of geotextiles 462
15.4 Leachate collection pipes 464
15.5 Manholes 478
16 Integration of hydrogeology and engineering in barrier design and impact assessment 480
16.1 Introduction 480
16.2 Hydraulic conductivity of aquitards 480
16.3 Some considerations in the design of highly engineered systems 488
16.4 Concentration of contaminant in the landfill 496
16.5 Failure of PLCS and SLCS 503
16.6 Composite liners 511
16.7 Expansion of landfills 519
16.8 Summary 521
Appendix A Glossary 524
Appendix B Notation 541
Appendix C Specific solution for matrix diffusion: one-dimensional, two-dimensional or
three-dimensional conditions 548
Appendix D Bulk GCL void ratio 551
References 552
Index 580
viii
Preface
The design of waste disposal facilities typically involves some form of "barrier" that separates the
"waste" from the general groundwater system and a cover (also a barrier) that separates the waste
from the above ground environment. The bottom barrier is intended to minimize the migration of
contaminants from the facility and hence the environmental impact of the facility is intimately
related to its design and long-term performance. Natural clayey deposits, recompacted clayey liners
or geosynthetic clay liners frequently represent a key component of these barriers. However, there
are many practical situations where neither a low-permeability clay nor plastic liner (geomembrane)
alone is sufficient to prevent unacceptable long-term environmental impact. In these circumstances,
the barrier is a designed system which may involve numerous components (e.g., composite liners,
multiple leachate collection systems, etc.) which work together to provide protection to the ground-
water environment. The cover may also involve drainage layers, geomembranes and/or clay liners,
and may serve both to limit inward migration of water and outward migration of both dissolved
contaminants and gases to the surface.
This book deals with the design and performance of barrier systems which may include natural
clayey deposits, recompacted clayey liners or even porous rock as part of the barrier system.
Considerable attention is also given to other components of the barrier system, such as the leachate
collection system and geomembrane liners. The first edition of the book was written as the basis for
short courses which the authors have given for educators, practising engineers and hydrogeologists
as well as a text for a senior or graduate level course. This second edition addresses the same
audience. We have attempted to explain all key concepts assuming little background knowledge
other than introductory courses in chemistry, soil mechanics and/or hydrogeology. In particular,
Chapter 1 is essential to the reader not familiar with the basic concepts. Appendix A also presents a
glossary of terms which should assist the reader not familiar with some of the terminology.
The objectives of this book are threefold. First, to examine the clayey component of the barrier.
Contaminants can potentially pass through a barrier by advection (e.g., the movement of contami-
nants due to groundwater movement) and diffusion (i.e., the movement of contaminants from
locations of high concentration to locations of lower concentration). The potential impact of a
given contaminant will generally depend on both the hydraulic conductivity and diffusion coefficient
for the barrier. Thus the book deals with the construction/compaction of clayey liners, the signifi-
cance of clay mineralogy in the design of barriers, geosynthetic clay liners and the determination of
appropriate hydraulic conductivity values and diffusion coefficients for clayey liners. In particular,
the field studies discussed in Chapter 9 demonstrate conclusively that diffusive contaminant trans-
port can and does occur even in the absence of significant advection. The chapters dealing with these
issues from the original book have been updated to reflect advances since the first book was
published in 1995 and a new chapter on geosynthetic clay liners has been added.
The second objective is to provide the reader with the current state-of-the-art with respect to
aspects of barrier system design other than the clayey component. Thus this second edition has a
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